Impairment of regeneration in aging: appropriateness or stochastics?

Khokhlov A.

According to our conception, the aging process is caused by cell proliferation restriction-induced accumulation of various macromolecular defects (mainly DNA damage) in cells of a mature organism or in a cell population. In the case of cell cultures, the proliferation restriction is related to so-called contact inhibition and to the Hayflick's limit, while in the case of multicellular organisms, it is related to the appearance, in the process of differentiation, of organs and tissues consisting of postmitotic and very slowly dividing cells. It is assumed that the proliferation of intact cells prevents accumulation of various errors in a cell population. However, the continuous propagation of all the cells in a multicellular organism is absolutely incompatible with its normal functioning. Thus, the program of development, when it generates postmitotic or slowly dividing cells, automatically leads also to the onset of the aging process (mortality increase with age). Therefore, any additional special program for aging simply becomes unnecessary. This, however, doesn't reject, for some organisms, the reasonability of programmed death, which makes possible the elimination of harmful, from the species point of view, individuals. It is also very important to emphasize that increase or decrease of an organism's lifespan under the effects of various external factors is not always necessarily related to modification of the aging process, though the experimental results in the field are usually interpreted in just this way. I called the experimental-gerontological models similar to the Hayflick's model "correlative", since they are based on some correlations only and not related necessarily to the gist of the aging phenomenon. So, for the Hayflick's model, it is the relationship between population doubling level and donor age, between population doubling potential and species lifespan, between some cell changes in vivo and in vitro, and so forth. If the rationale of the "Hayflick phenomenon" is used, we can't explain why we age. Nevertheless, many authors virtually put a sign of equality between aging in vitro and aging in vivo, which generates conclusions that are of quite doubtful accuracy. A classic illustration of this is the telomere concept of aging. Originally, the principle of shortening end-segments of DNA (telomeres) during each cell division was formulated at the beginning of seventies by the Russian scientist Aleksey Olovnikov and used by him to explain the limited "proliferative" lifespan in vitro of normal cells. Subsequently, the existence of this phenomenon was confirmed by the results of many research reports, the culmination of which was a publication in which the authors demonstrated the possibility of increasing the proliferative potential of normal cells by introducing the enzyme telomerase to them, thus restoring the lost telomere segments. At the moment it looks like the telomere shortening contributes to aging in vitro only, but not to aging in vivo because an organism never realizes the full proliferative potential of its cells. Besides, the most "responsive to aging" are the organs and tissues consisting of postmitotic cells, for which the concept of proliferative potential loses any meaning in practical terms. We developed another "correlative" model--a model for testing of geroprotectors and geropromoters--the "cell kinetics model." It is based on the well-known correlation between the "age" of cultured cells (age of their donor) and their saturation density. The model allowed us to perform preliminary testing of a lot of different compounds and factors that are interesting from a gerontological point of view, but it revealed no information about the real mechanisms of aging. However, the second model we use in our studies--the "stationary phase aging" model--obviously, is a "gist" model. It is based on the assumption that in the cells of stationary cultures various intracellular changes similar to those of an aging organism can be observed. The proliferation restriction in the case is provided, as a rule, just by contact inhibition. Many experimental results confirming this assumption were obtained. "Age-related" changes that are well known from organismal studies were shown to really occur in our experimental stationary cell culture model. Besides, such experiments can be carried out on nearly any type of cells from various biological species. Thus, the evolutionary approach to analysis of the data is provided. Moreover, the changes in the stationary cell cultures become detectable very soon--as a rule, in 2 to 3 weeks after beginning the experiment. All this allows us to suppose that the "stationary phase aging" model should provide a very effective approach to testing of different substances and their cocktails on their activities in terms of accelerating or retarding aging--of course, if their effect is realized on the cell level only.

Yablonskaya O.I., Ryndina T.S., Voeikov V.L., Khokhlov A.N.

The effect of an aqueous solution of hydrated C60-fullerene (HyFn) on the growth and “stationary phase aging” (accumulation of “age-related” changes in cultured cells during the slowing down of their proliferation within a single passage and the subsequent “aging” in the stationary phase of growth) of transformed B11-dii FAF28 Chinese hamster cells was studied. The final calculated concentration of HyFn in the growth medium was 10−19 M. A paradoxical result contrasting the available data on the absence of HyFn cytotoxicity at higher concentrations was obtained in our experiments: namely, HyFn decelerated cell proliferation (estimated by the growth of mass culture, as well as by the efficiency of colony formation) and accelerated the “stationary phase aging” of the cell culture. Moreover, repeated addition of an aqueous solution of HyFn (to the final calculated concentration of 10−19 M) to the cells that had already reached the stationary phase of growth caused a rapid (within no more than 24 h) death of a significant part of the cell population. The observed effect of HyFn at ultralow concentration is supposed to arise from the alterations in the properties of the water surrounding the fullerene molecule: namely, water becomes a donor and acceptor of electrons and regulates redox processes (especially those involving oxygen) in aqueous systems. This effect of HyFn at an ultralow concentration may be specific for transformed cells, and, therefore, experiments on normal fibroblasts with limited mitotic potential are planned as a continuation of the present study. It is also possible that the reported antiaging effect of HyFn in experimental animals is due to its anticancer, immunostimulatory, antiviral, and antibacterial properties manifested only at the whole-organism level.

Campisi J.

For most species, aging promotes a host of degenerative pathologies that are characterized by debilitating losses of tissue or cellular function. However, especially among vertebrates, aging also promotes hyperplastic pathologies, the most deadly of which is cancer. In contrast to the loss of function that characterizes degenerating cells and tissues, malignant (cancerous) cells must acquire new (albeit aberrant) functions that allow them to develop into a lethal tumor. This review discusses the idea that, despite seemingly opposite characteristics, the degenerative and hyperplastic pathologies of aging are at least partly linked by a common biological phenomenon: a cellular stress response known as cellular senescence. The senescence response is widely recognized as a potent tumor suppressive mechanism. However, recent evidence strengthens the idea that it also drives both degenerative and hyperplastic pathologies, most likely by promoting chronic inflammation. Thus, the senescence response may be the result of antagonistically pleiotropic gene action.

Boehm A., Khalturin K., Anton-Erxleben F., Hemmrich G., Klostermeier U.C., Lopez-Quintero J.A., Oberg H., Puchert M., Rosenstiel P., Wittlieb J., Bosch T.C.

Hydra ’s unlimited life span has long attracted attention from natural scientists. The reason for that phenomenon is the indefinite self-renewal capacity of its stem cells. The underlying molecular mechanisms have yet to be explored. Here, by comparing the transcriptomes of Hydra ’s stem cells followed by functional analysis using transgenic polyps, we identified the transcription factor forkhead box O (FoxO) as one of the critical drivers of this continuous self-renewal. foxO overexpression increased interstitial stem cell and progenitor cell proliferation and activated stem cell genes in terminally differentiated somatic cells. foxO down-regulation led to an increase in the number of terminally differentiated cells, resulting in a drastically reduced population growth rate. In addition, it caused down-regulation of stem cell genes and antimicrobial peptide (AMP) expression. These findings contribute to a molecular understanding of Hydra ’s immortality, indicate an evolutionarily conserved role of FoxO in controlling longevity from Hydra to humans, and have implications for understanding cellular aging.

Gladyshev V.N.

What the causes of aging are and which factors define lifespan are key questions in the understanding of aging. Here, it is argued that cellular life involves (i) inevitable accumulation of damage resulting from imperfectness and heterogeneity of every cellular process, and (ii) dilution of damage when cells divide. While severe damage is cleared by protective systems, milder damage can only be diluted. This is due to the high cost of accuracy, the greater number of damage forms compared to protective systems, and the constraints on cellular life inherited from the prokaryotic world. This strategy also applies to cancer cells, which are particularly dependent on damage dilution. Imposing restriction on cell division necessarily leads to aging. Interventions that extend lifespan act through metabolic reprogramming, thereby changing both damage composition and the rate of damage accumulation. Thus, heterogeneity leading to myriad mild damage forms represents the cause of aging, whereas the processes that affect the damage landscape and damage accumulation are lifespan regulators.

Martínez D.E., Bridge D.

Existing data imply that the cnidarian Hydra vulgaris does not undergo senescence. In contrast, the related species Hydra oligactis shows increased mortality and physiological deterioration following sexual reproduction. Hydra thus offers the chance to study a striking difference in lifespan in members of the same genus. Adult Hydra possess three well-characterized stem cell populations, one of which gives rise to both somatic cells and gametes. The lack of senescence in Hydra vulgaris raises the question of how these stem cell populations are maintained over long periods of time. Investigation of the roles in Hydra of proteins involved in cellular stress responses in other organisms should provide insight into this issue. Proteins of particular interest include the Hsp70 family proteins and the transcription factor FoxO.

Alinkina E.S., Vorobyova A.K., Misharina T.A., Fatkullina L.D., Burlakova E.B., Khokhlov A.N.

In order to clarify possible cytological mechanisms that underlie the beneficial effects of carvacrol-bearing essential oils on health and mental abilities, we studied one of them (oregano essential oil) in experiments on transformed cultured Chinese hamster cells. Possible cytotoxic or mitogenic effects of the preparation at various concentrations were preliminarily estimated by analyzing the cell culture density after 4 days of cultivation. The preparation concentration in the growth medium (on carvacrol basis) varied from 1 × 10−15 up to 5 × 10−4 M (on carvacrol basis). As a result, two concentrations were selected for further experiments, including 2.5 × 10−5 M as the maximal absolutely non-toxic concentration and 2.5 × 10−4 M as the concentration at which the oregano essential oil decreased approximately 2-fold the final cell density of the grown culture. It was found that the preparation at 2.5 × 10−5 M had no effect on either the colony-forming ability of the cells or the saturation density of the culture (which is a marker of its “biological age”) or kinetics of its “stationary phase aging” (degradation of cultured cells in the stationary phase of growth, similar to age-related changes of the cells in aging organism). On the contrary, the oregano essential oil at 2.5 × 10−4 M abruptly diminished colony-forming ability of the cells and influenced as a “pro-aging” factor on the saturation density of the cell culture and kinetics of the cell death induced by “stationary phase aging.” Based on our own concept of aging and the data obtained, we assumed that detected increase in the life span of mice under the influence of the oregano essential oil could be determined by certain functional changes at the organismal level only, but is not associated with any geroprotective (anti-aging) activity of the preparation, which is manifested at the cellular level and improves the cell viability.

Skulachev V.P.

The abstract of the paper published by T. B. L. Kirkwood and S. Melov in the September issue of Current Biology starts with the following categorical statement: “Compelling arguments eliminate the idea that death is generally programmed by genes for ageing” [1]. The end of the abstract is less categorical: “It is recognized that in exceptional circumstances the possibility exists for selection to favor limiting survival. In acknowledging that at least in theory, aging might occasionally be adaptive, however, the high barriers to validating actual instances of adaptive ageing are made clear” [1]. A few years ago it was hardly possible to find the latter statement in an article written by the most famous proponents of non-programmed aging. Certainly, this conclusion is accompanied by some reservations. Nevertheless, the balance between concepts of programmed and non-programmed aging seems to be really shifted to the programmed one. Such a tendency appeared in 1972 when Kerr, Willie, and Currie published their paper “Apoptosis: a basic biological phenomenon” [2]. The main message of this article was that cells of multicellular organisms are equipped with a death program. In 2002, Severin and Hyman showed that a natural signal molecule (yeast pheromone) sex-specifically kills S. cerevisiae cells [3]. I suggested that this phenomenon can be regarded as a precedent of programmed death of a unicellular organism [4]. Later it was found in our group that the mechanism of such death strikingly resembles apoptosis of higher organisms [5]. To explain the pheromone effect on yeast in terms of the traditional concept of non-programmed death of organisms, Kirkwood and Melov [1] assumed that yeast cells form in fact a multicellular organism. Such an explanation is hardly sufficient since (i) programmed death phenomena are now also described in bacteria [6-9] and (ii) an additional function of a pheromone as an inducer of the organism's death program was discovered in a mammal, the small marsupial Antechinus stuartii. Male of this rodent uses pheromone to attract females and then to kill himself after run [10]. To define all cases of programmed death of organisms, in 1997 I suggested the term "phenoptosis" [11] (for discussion, see [7, 9, 12]).

Macieira-Coelho A.

The capacity to regenerate cell compartments through cell proliferation is an important characteristic of many developed metazoan tissues. Pre- and post-natal development proceeds through the modifications occurring during cell division. Experiments with cultivated cells showed that cell proliferation originates changes in cell functions and coordinations that contribute to aging and senescence. The implications of the finite cell proliferation to aging of the organism is not the accumulation of cells at the end of their life cycle, but rather the drift in cell function created by cell division. Comparative gerontology shows that the regulation of the length of telomeres has no implications for aging. On the other hand there are interspecies differences in regard to the somatic cell division potential that seem to be related with the “plasticity” of the genome and with longevity, which should be viewed independently of the aging phenomenon. Telomeres may play a role in this plasticity through the regulation of chromosome recombination, and via the latter also in development.

Blagosklonny M.V.

The most influential line of reasoning in gerontology is known as Disposable Soma Theory (DST). In brief, the theory states that aging is caused by accumulation of random damage, which is counteracted by repair. Repair is costly and the organism allocates exactly the needed amount of energetic resources. Recently, DST was applied to explain why women live longer than men [1]. Women are less disposable than men, so they need a better repair and thus live longer [1].

Khokhlov A.N.

The history of gerontological experiments on cell cultures is reviewed. Cytogerontological studies and aging theories by Weismann, Carrel, Hayflick, and the author are compared. It is emphasized that the basic notion of aging mechanisms was deeply revised several times within the 20th century. It is concluded that at present the aging of multicellular organisms cannot be satisfactorily explained with the help of cytogerontological studie’s data. Experiments on cell cultures need to be combined with fundamental gerontological studies, including survival curve analysis for humans or experimental animals.

Hayflick L.

In the invitation to write this article, I am asked to describe my “…contributions… to cell aging and the telomere story”. My research on the phenomenon of cell senescence began more than 50 years ago. From that time until today, the work done on this subject in my laboratory, and that of hundreds of other researchers, can only be described in the allotted space by a few generalizations and even fewer details. From the birth of cell culture technology in 1907, it was believed that all cultured cells, if provided with the proper conditions, would replicate indefinitely. Fifty-three years later, we overthrew this dogma by finding that, in the best conditions, normal cells have a finite capacity to replicate and that only abnormal or cancer cell populations can replicate indefinitely. We interpreted these findings to impact on our understanding of the aging process. If, as had been thought prior to our work, that normal cultured cells released from in vivo controls can replicate indefinitely, then age changes could not have an intracellular origin. Our findings demonstrated that, on the contrary, age changes do have an intracellular origin. The hundreds of changes that were subsequently found to precede the loss of replicative capacity have been interpreted to be age changes and the finitude of replication to be an expression of longevity determination. Age changes are the result of the inexorable dissipation of energy that occurs in complex biomolecules and that, unless repaired, causes their dysfunction. The positive balance of repair and synthetic processes over accumulating dysfunctional substrate molecules shifts after reproductive success to favor the increase in more dysfunctional molecules over repair capability as the repair processes succumb to the same Second Law of thermodynamics. The processes that control longevity, or how long repair and synthesis processes remain functional and retain their balance over dysfunctional molecules, are governed by the genome. Hence, the information that governs longevity determination is sexually transmitted whereas the aging process is a stochastic or random process governed by the laws of probability that are embodied in the Second Law of thermodynamics. Our search for the location of the molecular mechanism that controls the number of cell, or DNA replications, that occur in normal cells ended with our finding that the mechanism was located in the nucleus. Years later, and as the result of the confluence of studies done by others in several unrelated fields, the molecular mechanism was discovered. It was found that telomere attrition governs the limit on DNA replications in normal cells and that the expression of telomerase can circumvent this limit, thus explaining our discoveries of the phenomena of normal cell mortality and cancer cell immortality.

W. Estep P.

Khokhlov A.N.

According to author’s concept, the aging process is caused by cell proliferation restriction-induced accumulation of various macromolecular defects (mainly DNA damage) in cells of an organism or cell population. In case of cell cultures, this proliferation restriction is related to either so-called contact inhibition or Hayflick’s limit, and in case of multicellular organisms, to the appearance, in the process of differentiation, of organs and tissues consisting of postmitotic or very slowly dividing cells. Cell proliferation is absolutely incompatible with normal functioning of a macroorganism. Thus, the development program automatically leads to a situation inducing the aging process (martaliry rates increase with age). Therefore, any special program of aging simply becomes senseless. This, however, does not reject for some organisms the reasonability of programmed death, which makes possible the elimination of harmful, from the species’s point of view, individuals. It is also very important to understand that increase or decrease of organism’s life span under the action of various factors are not necessarily related to a modification of the aging process, even though the experimental results in this field are interpreted just in this way.

Holliday R., Rattan S.I.

The biological reasons for ageing are now well known, so it is no longer an unsolved problem in biology. Furthermore, there is only one science of ageing, which is continually advancing. The significance and importance of the mutations that lengthen the lifespan of invertebrates can be assessed only in relationship to previous well-established studies of ageing. The mutant strains of model organisms that increase longevity have altered nutrient signalling pathways similar to the effects of dietary restriction, and so it is likely that there is a shift in the trade-off between reproduction and maintenance of the soma. To believe that the isolation and characterisation of a few invertebrate mutations (as well as those in yeast) will “galvanise” the field and provide new insights into human ageing is an extreme point of view which does not recognize the huge progress in ageing research that has been made in the last 50 years or so.

Shilovsky G.A.

The article describes the history of studies of survival data carried out at the Research Institute of Physico-Chemical Biology under the leadership of Academician V. P. Skulachev from 1970s until present, with special emphasis on the last decade. The use of accelerated failure time (AFT) model and analysis of coefficient of variation of lifespan (CVLS) in addition to the Gompertz methods of analysis, allows to assess survival curves for the presence of temporal scaling (i.e., manifestation of accelerated aging), without changing the shape of survival curve with the same coefficient of variation. A modification of the AFT model that uses temporal scaling as the null hypothesis made it possible to distinguish between the quantitative and qualitative differences in the dynamics of aging. It was also shown that it is possible to compare the data on the survival of species characterized by the survival curves of the original shape (i.e., “flat” curves without a pronounced increase in the probability of death with age typical of slowly aging species), when considering the distribution of lifespan as a statistical random variable and comparing parameters of such distribution. Thus, it was demonstrated that the higher impact of mortality caused by external factors (background mortality) in addition to the age-dependent mortality, the higher the disorder of mortality values and the greater its difference from the calculated value characteristic of developed countries (15-20%). For comparison, CVLS for the Paraguayan Ache Indians is 100% (57% if we exclude prepuberty individuals as suggested by Jones et al.). According to Skulachev, the next step is considering mortality fluctuations as a measure for the disorder of survival data. Visual evaluation of survival curves can already provide important data for subsequent analysis. Thus, Sokolov and Severin [1] found that mutations have different effects on the shape of survival curves. Type I survival curves generally retains their standard convex rectangular shape, while type II curves demonstrate a sharp increase in the mortality which makes them similar to a concave exponential curve with a stably high mortality rate. It is noteworthy that despite these differences, mutations in groups I and II are of a similar nature. They are associated (i) with “DNA metabolism” (DNA repair, transcription, and replication); (ii) protection against oxidative stress, associated with the activity of the transcription factor Nrf2, and (iii) regulation of proliferation, and (or these categories may overlap). However, these different mutations appear to produce the same result at the organismal level, namely, accelerated aging according to the Gompertz’s law. This might be explained by the fact that all these mutations, each in its own unique way, either reduce the lifespan of cells or accelerate their transition to the senescent state, which supports the concept of Skulachev on the existence of multiple pathways of aging (chronic phenoptosis).

Ruggieri E., Domenico E.D., Locatelli A.G., Isopo F., Damanti S., Lorenzo R.D., Milan E., Musco G., Rovere-Querini P., Cenci S., Vénéreau E.

Shilovsky G.A.

The article describes the history of studies of survival data carried out at the Research Institute of Physico-Chemical Biology under the leadership of Academician V. P. Skulachev from 1970s until present, with special emphasis on the last decade. The use of accelerated failure time (AFT) model and analysis of coefficient of variation of lifespan (CVLS) in addition to the Gompertz methods of analysis, allows to assess survival curves for the presence of temporal scaling (i.e., manifestation of accelerated aging), without changing the shape of survival curve with the same coefficient of variation. A modification of the AFT model that uses temporal scaling as the null hypothesis made it possible to distinguish between the quantitative and qualitative differences in the dynamics of aging. It was also shown that it is possible to compare the data on the survival of species characterized by the survival curves of the original shape (i.e., “flat” curves without a pronounced increase in the probability of death with age typical of slowly aging species), when considering the distribution of lifespan as a statistical random variable and comparing parameters of such distribution. Thus, it was demonstrated that the higher impact of mortality caused by external factors (background mortality) in addition to the age-dependent mortality, the higher the disorder of mortality values and the greater its difference from the calculated value characteristic of developed countries (15-20%). For comparison, CVLS for the Paraguayan Ache Indians is 100% (57% if we exclude prepuberty individuals as suggested by Jones et al.). According to Skulachev, the next step is considering mortality fluctuations as a measure for the disorder of survival data. Visual evaluation of survival curves can already provide important data for subsequent analysis. Thus, Sokolov and Severin [1] found that mutations have different effects on the shape of survival curves. Type I survival curves generally retains their standard convex rectangular shape, while type II curves demonstrate a sharp increase in the mortality which makes them similar to a concave exponential curve with a stably high mortality rate. It is noteworthy that despite these differences, mutations in groups I and II are of a similar nature. They are associated (i) with “DNA metabolism” (DNA repair, transcription, and replication); (ii) protection against oxidative stress, associated with the activity of the transcription factor Nrf2, and (iii) regulation of proliferation, and (or these categories may overlap). However, these different mutations appear to produce the same result at the organismal level, namely, accelerated aging according to the Gompertz’s law. This might be explained by the fact that all these mutations, each in its own unique way, either reduce the lifespan of cells or accelerate their transition to the senescent state, which supports the concept of Skulachev on the existence of multiple pathways of aging (chronic phenoptosis).

Khokhlov A.N.

The history of research into the basic mechanisms of the pathogenesis of Alzheimer’s disease (AD) is briefly considered. Concepts are analyzed in which a decisive role in the development of this disease was attributed to aluminum or free radicals. The lack of reliable data to date to support these concepts is emphasized. The point of view of the author is presented, according to which almost all the results indicating the feasibility of using antioxidants (as well as other potential drugs for AD) for the prevention and treatment of AD were obtained on model animals with certain pathologies (for example, with severe oxidative stress), which contribute to the formation of symptoms similar to those of AD in humans. In this regard, parallels are drawn with experimental gerontological research aimed at studying the effect of a calorie-restricted diet on aging and life span. It is noted that in these studies, animals were used that were either not completely normal or were in unfavorable conditions. According to the author, the lack of significant progress in the development of effective geroprotectors or drugs for the prevention/ treatment of AD is due to the fact that most specialists ignore the principles of classical gerontology, in particular, the definitions of aging and age-related diseases, as well as the correct approaches to the selection of control objects for their studies. It is emphasized that humans, unfortunately, cannot use the freshwater hydra method to combat aging and age-related diseases. Under certain conditions, it continuously renews all cells (including nerve ones) of its body and thereby ensures its “immortality.” In humans, the replacement of “old” neurons can lead to the loss of personality/individuality, and the “repair” of these cells today seems impossible. In this regard, the author considers it expedient to study the aging of postmitotic cells in experiments on stationary cell cultures, which can accelerate, in particular, the deciphering of the mechanisms of accumulation of beta-amyloid and senile pigments such as lipofuscin in neurons. The need for clinical studies of AD is noted as complementary to experimental work, although the first ones are much more expensive and time-consuming. Only confirmation in human studies of the effectiveness of drugs developed in experiments on model animals will allow them to be recommended for use in the clinical practice.

Khokhlov A.N.

The history of research into the fundamental mechanisms of the pathogenesis of Alzheimer’s disease (AD) is briefly reviewed. Concepts in which a decisive role in the development of this disease was attributed to aluminum or free radicals are analyzed. The lack of reliable data to date to support these concepts is highlighted. The author’s point of view is stated, according to which almost all the results indicating the advisability of using antioxidants (as well as other potential drugs for AD) for the prevention and treatment of AD were obtained in model animals with certain pathologies (for example, with severe oxidative stress), which contribute to the formation of symptoms similar to those of AD in humans. In this regard, parallels with experimental gerontological work aimed at studying the effect of calorie-restricted nutrition on aging and life span are drawn. It is noted that these studies also used animals that were either not completely normal or were in unfavorable conditions. According to the author, the lack of serious success in the development of effective geroprotectors or drugs for the prevention/treatment of AD is due to the ignorance by most specialists of the principles of classical gerontology, in particular, the definitions of aging and age-related diseases, as well as correct approaches to the selection of control objects for their studies. It is emphasized that humans, unfortunately, cannot use the freshwater hydra method to combat aging and age-related diseases. Under certain conditions, it continuously renews all cells (including nerve cells) of its body and thereby ensures its “immortality.” In humans, replacing “old” neurons can lead to loss of personality/individuality, and “repairing” these cells seems impossible today. In this regard, the author considers it advisable to conduct studies of the aging of postmitotic cells in experiments on stationary cell cultures, which can accelerate, in particular, elucidation of the mechanisms of accumulation of beta-amyloid and senile pigments, such as lipofuscin, in neurons. The need to conduct clinical studies of AD as complementary to experimental work is noted, although the former are much more expensive and time-consuming. Only confirmation in human studies of the effectiveness of drugs developed in experiments on model animals will allow them to be recommended for clinical use.

Khokhlov A.N.

Editor-in-Chief of Advances in Gerontology describes the current editorial policy and the strategy of future development of the renewed journal which since 2023 is published as a separate independent edition. It is emphasized that now priority is given to publications devoted to (1) the fundamental mechanisms which may determine the increase in the probability of death of living organisms, including humans, with age, and to (2) identifying various factors of both chemical and physical nature that could potentially help to slow down the aging process. In addition, papers included in Volume 13, Issue 1 are shortly reviewed.

Gupta M., Somasundaram I.

HBOT has been implemented in a large number of clinical conditions where it is found to be highly beneficial. HBOT enables increased bioavailability of oxygen throughout the tissues by elevating the partial pressure of oxygen in the blood. The therapeutic effects of HBOT arise from the direct effect of oxygen in preservation of oxidative environment and indirectly by modulating a wide array of physiological functions. HBOT has gained attention as an anti-ageing therapy due to its ability to modulate the physiological and molecular functions directly involved in the process of ageing. The regenerative effect of HBOT is evident in its application in treatment of wound healing and repair. In general, HBOT can affect the cellular micro-environment to modulate functions like cell senescence, proteostasis, telomerase activity and mitochondrial function which may result in a rejuvenating effect on body. However, further research is required to understand the role of oxygen in the process of ageing.

Singh B., Kumar Rai A.

The progressive decline of the anatomical architecture and loss of functional integrity of an individual is aging. Accumulation of degenerative cellular and molecular changes in the aging cells increases the fragility at the cellular and molecular levels. It pushes towards age-associated diseases like Alzheimer's disease, hypertension, cancer, cardiovascular diseases, etc. The impaired T cell function in aging is a leading contributor to increased susceptibility to pathogens, minimized vaccine response, and skewed inflammation. Recent studies about the role of T cells in the remodelling of the immune system have provided ways to examine and explore aging puzzles and their correlation with T cell functions. Here we review the metabolic aspect of T cell function and its possible restoration. IL-7 and mTOR mediated pathways and their association with reactivation of effector T cell function could help understanding the dark side of the compromised adaptive immune system, particularly T cell response, in aging. Understanding these crucial fundamentals could help design and target new molecules to prevent loss of T cell functionality in aging.

Khokhlov A.N.

The author’s view on the current state of gerontological research is presented. He believes that the widespread departure from the principles of classical gerontology, formulated back in the 20th century, has not been reflected in the works in the field of biology of aging (both theoretical and experimental) in the best way. The neglect of the fundamental principles of gerontological research has led to the fact that, in most works, the classical definition of aging as a set of age-related changes in practically healthy individuals leading to an increase in the rate of mortality is ignored. The emphasis is on assessing the average and maximum life span of the studied organisms, even if they are ageless. Extending the lifetime of such objects cannot be considered a modification of the rate of their aging. It is emphasized that special attention is now being paid to molecular age-related changes, which some gerontologists consider aging, although this is just its possible mechanism or consequence. However, geroprotectors are very often studied exactly by assessing the modification of the rate of such age-related changes. At the same time, as classical gerontology rightly believes, the principles of which the author urges to adhere to, without taking the survival curves of the control and experimental cohorts, it is impossible to draw a correct conclusion about whether the studied compound is a geroprotector. At the same time, an approach to the formation of such cohorts, including an assessment of the minimum required number of organisms in them, as well as the “quality” of their health, is very important. Several gerontological articles that have been published in the most highly ranked scientific journals and, therefore, have attracted much attention of relevant specialists are considered. This attention was expressed, among other things, in the high citation rate of these works, although they were performed with significant violations of the principles of classical gerontology, which were subsequently identified by other researchers. It is also emphasized that, at present, the rating of a scientific journal for many gerontological readers has become much more important than the correctness of the results and ideas presented in the article. A list of methodological problems is given, which, according to the author, not only complicate the situation with modern gerontological research but also make tangible progress in this area practically unattainable.

Ashapkin V., Khavinson V., Shilovsky G., Linkova N., Vanuyshin B.

Effects of the short peptides Ala-Glu-Asp (AED), Lys-Glu-Asp (KED) and Lys-Glu (KE) on the expression of IGF1, FOXO1, TERT, TNKS2, and NFκB genes were studied in human embryo bone marrow mesenchymal stem cells (line FetMSCs) variously aged in “passages” or “stationary” cultures. Both cell aging models were similar in gene expression. The main difference was in the TERT gene expression level, which showed an eightfold increase at the “stationary” aging. IGF1 gene expression levels were very similar in both cell culture aging models, being enhanced by 3.5–5.6 fold upon the addition of the peptides. The FOXO1 gene was expressed twice more actively in the “stationary” than in the “passages” aging model. KED peptide inhibited FOXO1 gene expression by 1.6–2.3 fold. KE peptide increased FOXO1 gene expression by about two-fold in the “stationary” aging model but did not affect it in the “passage” aging model. The most striking difference in the peptide effect on cell aging between “passages” and “stationary” aging models was in the KED effects on TNKS2 gene expression; this expression was inhibited by KED in the “passages” model, while stimulation was observed in the “stationary” model. AED, KED, and KE stimulated expression of the NFκB gene in both models. Thus, the peptides studied at nanomolar concentrations modulate the expression of some genes known to be involved in cell aging.

Khokhlov A.N.

This is a short review concerning the problem of germ line “immortality,” which was already formulated by A. Weismann at the end of the 19th century. Over the following years, it attracted the attention of many gerontologists, who tried to understand the mechanisms of infinite transfer of genetic information from generation to generation with the help of germ cells, which, in contrast to somatic cells, avoid aging in this way. However, it remained unclear how the germ cells of women, which are in fact a population of non-dividing cells (it is similar to stationary phase aging non-subcultured cell culture), provide the mentioned immortality of the germ line. Distinguished Russian gerontologist Zh.A. Medvedev, who passed away recently, published in 1981 his brilliant work “On the Immortality of the Germ Line: Genetic and Biochemical Mechanisms. A Review,” the main points of which are relevant up to today. His paper just discusses the possible mechanisms of such “immortality.” They are analyzed in detail in the current article and can be reduced mainly to the existence of a number of barriers that, in most cases, do not allow progeny to emerge from “old” germ cells (although certain “rejuvenating” processes in the gametes still go). Therefore, children are “born young.” Some alternative approaches to explaining the immortality of the germ line are also considered. Special attention is paid to the “parental age effect” and the role of eggs and sperm cells in this phenomenon.

Khokhlov A.N.

This is a brief overview of the ideas of the possibility of using the cell kinetic model developed by the author in the 1980s to test, in experiments on cell cultures, potential geroprotectors and geropromoters that slow down or accelerate, respectively, the aging process in animals and humans. The history of the evolution of this model—from estimation of only the cell reproduction rate and saturation density in a non-subcultured cell culture to constructing survival curves in the stationary phase of growth and to a further analysis of the possible interrelation between all parts of the curve of cells’ growth and subsequent dying out—is considered. Possible approaches to mathematical and statistical analysis of the data obtained within the framework of this model system are analyzed. It is emphasized that such studies can be carried out on cells of a very different nature (normal and transformed human and animal cells, plant cells, yeast, mycoplasmas, bacteria, etc.), which makes possible an evolutionary approach to the interpretation of the results obtained. At the same time, in the author’s opinion, the most promising experiments are those carried out on immortalized cells of humans and animals, since they are not cancerous on the one hand and have an unlimited mitotic potential on the other hand and, therefore, do not “age” in the process of numerous divisions, as, for example, normal human diploid fibroblasts do. It is assumed that the appropriate mathematical analysis of the entire growth and dying out curve of a non-subcultured cell culture (from seeding into a culture flask to the complete death of all cells) may allow the clarification of certain relationships between the development and aging of a multicellular organism and to increase the reliability of identifying promising geroprotectors.

Shilovsky G.A., Shram S.I., Morgunova G.V., Khokhlov A.N.

It is well known that the number of dividing cells in an organism decreases with age. The average rate of cell division in tissues and organs of a mature organism sharply decreases, which is probably a trigger for accumulation of damage leading to disturbance of genome integrity. This can be a cause for the development of many age-related diseases and appearance of phenotypic and physiological signs of aging. In this connection, the protein poly(ADP-ribosyl)ation system, which is activated in response to appearance of various DNA damage, attracts great interest. This review summarizes and analyzes data on changes in the poly(ADP-ribosyl)ation system during development and aging in vivo and in vitro, and due to restriction of cell proliferation. Special attention is given to methodological aspects of determination of activity of poly(ADP-ribose) polymerases (PARPs). Analysis of relevant publications and our own data has led us to the conclusion that PARP activity upon the addition of free DNA ends (in this review referred to as stimulated PARP activity) is steadily decreasing with age. However, the dynamics of PARP activity measured without additional activation of the enzyme (in this review referred to as unstimulated activity) does not have such a clear trend: in many studies, the presented differences are statistically non-significant, although it is well known that the number of unrepaired DNA lesions steadily increases with aging. Apparently, the cell has additional regulatory systems that limit its own capability of reacting to DNA damage. Special attention is given to the influence of the cell proliferative status on PARP activity. We have systematized and analyzed data on changes in PARP activity during development and aging of an organism, as well as data on differences in the dynamics of this activity in the presence/absence of additional stimulation and on cellular processes that are associated with activation of these enzymes. Moreover, data obtained in different models of cellular aging are compared.

Khokhlov A.N., Klebanov A.A., Morgunova G.V.

Ideas of proponents and opponents of programmed aging concerning the expediency of this phenomenon for the evolution of living organisms are briefly considered. We think that evolution has no “gerontological” purpose, because the obligate restriction of cell proliferation during the development of multicellular organisms is a factor that “automatically” triggers aging due to the accumulation of various macromolecular lesions in cells as a result of the suppression, or even complete cessation of emergence of new, intact cells. This leads to the “dilution” of stochastic damage (the most important of which is DNA damage) at the level of the entire cellular population. Some additional arguments in favor of the inexpediency of aging for both species and individuals are also listed.

Peregrim I.

This article introduces a new evolutionary theory of aging, which suggests that aging is the result of imperfections in cell turnover in organisms. Some of the simplest animals demonstrate the strongest ability of cell renewal and therefore, according to this theory, their aging often seems to be negligible. Evolutionarily related organisms (e.g. mammals) share similar abilities in tissue cell turnover but they differ in the rates at which the process is performed. These rate differences are more or less forced by the speed of irreversible damage (e.g. lipofuscin) increase in their cells. This speed is the result of an evolutionary trade-off of “function vs. resistance to irreversible damage” in their cell molecules. The article also offers an explanation of the differences in basal metabolic rate between different species. Put simply, while a trade-off in irreversible damage plays a role in aging, the trade-off in reversible damage plays a role in basal metabolic rate.