Cell aging in vivo and in vitro

Long-Term In Vitro Culture Alters Gene Expression Pattern of Genes Involved in Ontological Groups Representing Cellular Processes

The oviduct provides an optimal environment for the final preparation, transport, and survival of gametes, the fertilization process, and early embryonic development. Most of the studies on reproduction are based on in vitro cell culture models because of the cell's accessibility. It creates opportunities to explore the complexity of directly linked processes between cells. Previous studies showed a significant expression of genes responsible for cell differentiation, maturation, and development during long-term porcine oviduct epithelial cells (POECs) in vitro culture. This study aimed at establishing the transcriptomic profile and comprehensive characteristics of porcine oviduct epithelial cell in vitro cultures, to compare changes in gene expression over time and deliver information about the expression pattern of genes highlighted in specific GO groups. The oviduct cells were collected after 7, 15, and 30 days of in vitro cultivation. The transcriptomic profile of gene expression was compared to the control group (cells collected after the first day). The expression of COL1A2 and LOX was enhanced, while FGFBP1, SERPINB2, and OVGP1 were downregulated at all selected intervals of cell culture in comparison to the 24-h control (p-value < 0.05). Adding new detailed information to the reproductive biology field about the diversified transcriptome profile in POECs may create new future possibilities in infertility treatments, including assisted reproductive technique (ART) programmes, and may be a valuable tool to investigate the potential role of oviduct cells in post-ovulation events.

How Metabolic Rate Relates to Cell Size

Simple Summary

The metabolic conversion of resources into living structures and processes is fundamental to all living systems. The rate of metabolism (‘fire of life’) is critical for supporting the rates of various biological processes (‘pace of life’), but why it varies considerably within and among species is little understood. Much of this variation is related to body size, but such ‘metabolic scaling’ relationships also vary extensively. Numerous explanations have been offered, but no consensus has yet been reached. Here, I critically review explanations concerning how cell size and number and their establishment by cell expansion and multiplication may affect metabolic rate and its scaling with body mass. Numerous lines of evidence suggest that cell size and growth can affect metabolic rate at any given body mass, as well as how it changes with increasing body mass during growth or evolution. Mechanisms causing negative associations between cell size and metabolic rate may involve reduced resource supply and/or demand in larger cells, but more research is needed. A cell-size perspective not only helps to explain some (but not all) variation in metabolic rate and its body-mass scaling, but may also foster the conceptual integration of studies of ontogenetic development and body-mass scaling.

Abstract

Metabolic rate and its covariation with body mass vary substantially within and among species in little understood ways. Here, I critically review explanations (and supporting data) concerning how cell size and number and their establishment by cell expansion and multiplication may affect metabolic rate and its scaling with body mass. Cell size and growth may affect size-specific metabolic rate, as well as the vertical elevation (metabolic level) and slope (exponent) of metabolic scaling relationships. Mechanistic causes of negative correlations between cell size and metabolic rate may involve reduced resource supply and/or demand in larger cells, related to decreased surface area per volume, larger intracellular resource-transport distances, lower metabolic costs of ionic regulation, slower cell multiplication and somatic growth, and larger intracellular deposits of metabolically inert materials in some tissues. A cell-size perspective helps to explain some (but not all) variation in metabolic rate and its body-mass scaling and thus should be included in any multi-mechanistic theory attempting to explain the full diversity of metabolic scaling. A cell-size approach may also help conceptually integrate studies of the biological regulation of cellular growth and metabolism with those concerning major transitions in ontogenetic development and associated shifts in metabolic scaling.

Serial Passaging of RAW 264.7 Cells Modulates Intracellular AGE Formation and Downregulates RANKL-Induced In Vitro Osteoclastogenesis

The passage number of cells refers to the number of subculturing processes that the cells have undergone. The effect of passage number on morphological and phenotypical characteristics of cells is of great importance. Advanced glycation end products have also been associated with cell functionality and characteristics. Murine monocyte RAW 264.7 cells differentiate into osteoclasts upon receptor activation caused by nuclear factor-kappa-Β ligand (RANKL) treatment. This study aims to identify the role of passage number on intracellular advanced glycation end products (AGEs) formation and osteoclastogenic differentiation of RAW 264.7 cells. Western blotting was performed to check intracellular AGE formation along with fluorometric analysis using a microplate reader. Tartrate-resistant acid phosphatase (TRAP) staining was performed to check osteoclastogenic differentiation, and qPCR was realized to check the responsible mRNA expression. Immunofluorescence was used to check the morphological changes. Intracellular AGE formation was increased with passaging, and the higher passage number inhibited multinucleated osteoclastogenic differentiation. Osteoclastogenic gene expression also showed a reducing trend in higher passages, along with a significant reduction in F-actin ring size and number. Lower passages should be used to avoid the effects of cell subculturing in in vitro osteoclastogenesis study using RAW 264.7 cells.

Long-term explant culture: an improved method for consistently harvesting homogeneous populations of keloid fibroblasts

Explant culture is a more suitable method than enzyme digestion for the isolation of keloid fibroblasts (KFs), but it has a longer isolation period. In this study, we propose a long-term explant culture method. Unlike in the conventional explant culture method, we continued culturing explants to isolate KFs rather than discarding them during passage. We demonstrated that keloid explants could be cultured for more than 4 months to continuously yield enriched KFs, and the KFs from the repeatedly cultured explants had shorter isolation times. The biological behavior and fibrotic phenotypic characteristics of the KFs from the explants cultured long term were investigated, and no statistical differences were found compared with the KFs from the original explants. In conclusion, the long-term explant culture method was shown to be efficient for harvesting a large, homogeneous population of KFs. The high efficiency as well as ease of operation and sample saving make this method convenient for researchers working with KFs.

Regulation of Gene Expression by Telomere Position Effect

Many diseases that involve malignant tumors in the elderly affect the quality of human life; therefore, the relationship between aging and pathogenesis in geriatric diseases must be under-stood to develop appropriate treatments for these diseases. Recent reports have shown that epigenetic regulation caused by changes in the local chromatin structure plays an essential role in aging. This review provides an overview of the roles of telomere shortening on genomic structural changes during an age-dependent shift in gene expression. Telomere shortening is one of the most prominent events that is involved in cellular aging and it affects global gene expression through genome rearrangement. This review provides novel insights into the roles of telomere shortening in disease-affected cells during pathogenesis and suggests novel therapeutic approaches.

Age and sex modify cellular proliferation responses to oxidative stress and glucocorticoid challenges in baboon cells

Aging is associated with progressive loss of cellular homeostasis resulting from intrinsic and extrinsic challenges. Lack of a carefully designed, well-characterized, precise, translational experimental model is a major limitation to understanding the cellular perturbations that characterize aging. Here, we tested the feasibility of primary fibroblasts isolated from nonhuman primates (baboons) as a model of cellular resilience in response to homeostatic challenge. Using a real-time live-cell imaging system, we precisely defined a protocol for testing effects of prooxidant compounds (e.g., hydrogen peroxide (H₂O₂), paraquat), thapsigargin, dexamethasone, and a low glucose environment on cell proliferation in fibroblasts derived from baboons across the life course (n = 11/sex). Linear regression analysis indicated that donor age significantly reduced the ability of cells to proliferate following exposure to H₂O₂ (50 and 100 µM) and paraquat (100 and 200 µM) challenges in cells from males (6.4-21.3 years; average lifespan 21 years) but not cells from females (4.3-15.9 years). Inhibitory effects of thapsigargin on cell proliferation were dependent on challenge duration (2 vs 24 h) and concentration (0.1 and 1 µM). Cells from older females (14.4-15.9 years) exhibited greater resilience to thapsigargin (1 µM; 24 h) and dexamethasone (500 µM) challenges than did those from younger females (4.3-6.7 years). The cell proliferation response to low glucose (1 mM) was reduced with age in both sexes. These data indicate that donor's chronological age and sex are important variables in determining fibroblast responses to metabolite and other challenges.

Mechanisms and significance of therapy-induced and spontaneous senescence of cancer cells

In contrast to the well-recognized replicative and stress-induced premature senescence of normal somatic cells, mechanisms and clinical implications of senescence of cancer cells are still elusive and uncertain from patient-oriented perspective. Moreover, recent years provided multiple pieces of evidence that cancer cells may undergo senescence not only in response to chemotherapy or ionizing radiation (the so-called therapy-induced senescence) but also spontaneously, without any external insults. Since the molecular nature of the latter process is poorly recognized, the significance of spontaneously senescent cancer cells for tumor progression, therapy effectiveness, and patient survival is purely speculative. In this review, we summarize the most up-to-date research regarding therapy-induced and spontaneous senescence of cancer cells, by delineating the most important discoveries regarding the occurrence of these phenomena in vivo and in vitro. This review provides data collected from studies on various cancer cell models, and the narration is presented from the broader perspective of the most critical findings regarding the senescence of normal somatic cells.

Multi-Parameter Analysis of Biobanked Human Bone Marrow Stromal Cells Shows Little Influence for Donor Age and Mild Comorbidities on Phenotypic and Functional Properties

Heterogeneous populations of human bone marrow-derived stromal cells (BMSC) are among the most frequently tested cellular therapeutics for treating degenerative and immune disorders, which occur predominantly in the aging population. Currently, it is unclear whether advanced donor age and commonly associated comorbidities affect the properties of ex vivo-expanded BMSCs. Thus, we stratified cells from adult and elderly donors from our biobank (n = 10 and n = 13, mean age 38 and 72 years, respectively) and compared their phenotypic and functional performance, using multiple assays typically employed as minimal criteria for defining multipotent mesenchymal stromal cells (MSCs). We found that BMSCs from both cohorts meet the standard criteria for MSC, exhibiting similar morphology, growth kinetics, gene expression profiles, and pro-angiogenic and immunosuppressive potential and the capacity to differentiate toward adipogenic, chondrogenic, and osteogenic lineages. We found no substantial differences between cells from the adult and elderly cohorts. As positive controls, we studied the impact of in vitro aging and inflammatory cytokine stimulation. Both conditions clearly affected the cellular properties, independent of donor age. We conclude that in vitro aging rather than in vivo donor aging influences BMSC characteristics.

Do senescence markers correlate in vitro and in situ within individual human donors?

Little is known on how well senescence markers in vitro and in situ correlate within individual donors. We studied correlations between the same and different in vitro markers. Furthermore, we tested correlations between in vitro markers with in situ p16INK4a positivity.

From 100 donors (20-91 years), cultured dermal fibroblasts were assessed for reactive oxygen species (ROS), telomere-associated foci (TAF), p16INK4a and senescence-associated β-gal (SAβ-gal), with/ without 0.6 µM rotenone for 3 days (short-term). In fibroblasts from 40 donors, telomere shortening, ROS and SAβ-gal were additionally assessed, with/ without 20 nM rotenone for 7 weeks (long-term). In skin from 52 donors, the number of p16INK4a positive dermal cells was assessed in situ.

More than half of the correlations of the same senescence markers in vitro between duplicate experiments and between short-term versus long-term experiments were significant. Half of the different senescence marker correlations were significant within the short-term and within the long-term experiments. The different senescence markers in vitro were not significantly correlated intra-individually with in situ p16INK4a positivity.
In conclusion, the same and different senescence markers are frequently correlated significantly within and between in vitro experiments, but in vitro senescence markers are not correlated with p16INK4a positivity in situ.

Spontaneous Cancers, But Not Many Induced Ones in Animals, Resemble Semi-New Organisms that Possess a Unique Programmed Cell Death Mode Different from Apoptosis, Senescent Death, Necrosis and Stress-Induced Cell Death

There are four basic cell death modes in animals, i.e. physiological senescent death (SD) and apoptosis as well as pathological necrosis and stress-induced cell death (SICD). There have been numerous publications describing “apoptosis” in cancer, mostly focused on killing cancer cells using radio- or chemo-therapy, with few on exploring how cancer cells die naturally without such treatments. Spontaneous benign or malignant neoplasms are immortal and autonomous, but they still retain some allegiance to their parental tissue or organ and thus are still somewhat controlled by the patient's body. Because of these properties of immortality, semi-autonomy, and semi-allegiance to the patient's body, spontaneous tumors have no redundant cells and resemble “semi-new organisms” parasitizing the patients, becoming a unique tissue type possessing a hitherto unannotated cell death mode besides SD, apoptosis, necrosis and SICD. Particularly, apoptosis aims to expunge redundant cells, whereas this new mode does not. In contrast to spontaneous tumors, many histologically malignant tumors induced in experimental animals, before they reach an advanced stage, regress after withdrawal of the inducer. This mortal and non-autonomous nature disqualifies these animal lesions as authentic neoplasms and as semi-new organisms but makes them a good tissue type for apoptosis studies. Ruminating over cell death in spontaneous cancers and many inauthentic tumors induced in animals from these new slants makes us realize that “whether cancer cells undergo apoptosis” is not an easy question with a simple answer. Our answer is that cancer cells have an uncharacterized programmed cell death mode, which is not apoptosis.

Evaluating the Remote Control of Programmed Cell Death, with or without a Compensatory Cell Proliferation

Organisms and their different component levels, whether organelle, cellular or other, come by birth and go by death, and the deaths are often balanced by new births. Evolution on the one hand has built demise program(s) in cells of organisms but on the other hand has established external controls on the program(s). For instance, evolution has established death program(s) in animal cells so that the cells can, when it is needed, commit apoptosis or senescent death (SD) in physiological situations and stress-induced cell death (SICD) in pathological situations. However, these programmed cell deaths are not predominantly regulated by the cells that do the dying but, instead, are controlled externally and remotely by the cells' superior(s), i.e. their host tissue or organ or even the animal's body. Currently, it is still unclear whether a cell has only one death program or has several programs respectively controlling SD, apoptosis and SICD. In animals, apoptosis exterminates, in a physiological manner, healthy but no-longer needed cells to avoid cell redundancy, whereas suicidal SD and SICD, like homicidal necrosis, terminate ill but useful cells, which may be followed by regeneration of the live cells and by scar formation to heal the damaged organ or tissue. Therefore, “who dies” clearly differentiates apoptosis from SD, SICD and necrosis. In animals, apoptosis can occur only in those cell types that retain a lifelong ability of proliferation and never occurs in those cell types that can no longer replicate in adulthood. In cancer cells, SICD is strengthened, apoptosis is dramatically weakened while SD has been lost. Most published studies professed to be about apoptosis are actually about SICD, which has four basic and well-articulated pathways involving caspases or involving pathological alterations in the mitochondria, endoplasmic reticula, or lysosomes.

Effect of antiaggregants on the in vitro viability, cell count and stability of abalone (Haliotis iris) haemocytes

The ability to successfully prepare and preserve haemocyte cells for microscopy and flow cytometry is critical for the investigation of animal immune systems. In this study, we observed the total cell count, in vitro viability and stability of New Zealand black-footed abalone (Haliotis iris) haemocytes with different antiaggregants and handling protocols. Haemocyte stability was evaluated by direct observation of haemocytes under the microscope and calculating the aggregation index. Haemocyte counts and viability were measured via flow cytometry and tested for the effect of different antiaggregants (Alsever's solution at three concentrations, and specialised blood collection tubes containing lithium heparin and K₂EDTA) at different temperatures and storage times. Results showed that Alsever's solution is an effective antiaggregant at haemolymph:antiaggregant dilution ratios of 1:1, 1:2 and 1:3. Lithium heparin was ineffective as an antiaggregant, whereas K₂EDTA was similarly as effective as Alsever's solution. The influence of different mixing techniques (vortex, pipetting and flipping) were subsequently tested using the K₂EDTA Microtainer^® tubes, revealing that proper mixing should be performed immediately. High cell viability can be achieved by mixing samples by either 10 s of vortexing (1000 rpm), 10 times pipetting or 20 times flipping. The in vitro storage of abalone haemocytes in AS and K₂EDTA as antiaggregants at ambient room temperature was highly effective for up to 24 h (75-85% viability; 0.05-0.15 aggregation index) and is recommended for haemocyte studies in H. iris. Utilization of K₂EDTA Microtainer^® tubes were advantageous since they are more cost effective compared to Alsever's solution, and samples can be prepared more efficiently.

A computational modelling framework to quantify the effects of passaging cell lines

In vitro cell culture is routinely used to grow and supply a sufficiently large number of cells for various types of cell biology experiments. Previous experimental studies report that cell characteristics evolve as the passage number increases, and various cell lines can behave differently at high passage numbers. To provide insight into the putative mechanisms that might give rise to these differences, we perform in silico experiments using a random walk model to mimic the in vitro cell culture process. Our results show that it is possible for the average proliferation rate to either increase or decrease as the passaging process takes place, and this is due to a competition between the initial heterogeneity and the degree to which passaging damages the cells. We also simulate a suite of scratch assays with cells from near–homogeneous and heterogeneous cell lines, at both high and low passage numbers. Although it is common in the literature to report experimental results without disclosing the passage number, our results show that we obtain significantly different closure rates when performing in silico scratch assays using cells with different passage numbers. Therefore, we suggest that the passage number should always be reported to ensure that the experiment is as reproducible as possible. Furthermore, our modelling also suggests some avenues for further experimental examination that could be used to validate or refine our simulation results.

Cellular Stiffness as a Novel Stemness Marker in the Corneal Limbus

Healthy eyes contain a population of limbal stem cells (LSCs) that continuously renew the corneal epithelium. However, each year, 1 million Americans are afflicted with severely reduced visual acuity caused by corneal damage or disease, including LSC deficiency (LSCD). Recent advances in corneal transplant technology promise to repair the cornea by implanting healthy LSCs to encourage regeneration; however, success is limited to transplanted tissues that contain a sufficiently high percentage of LSCs. Attempts to screen limbal tissues for suitable implants using molecular stemness markers are confounded by the poorly understood signature of the LSC phenotype. For cells derived from the corneal limbus, we show that the performance of cell stiffness as a stemness indicator is on par with the performance of ΔNP63α, a common molecular marker. In combination with recent methods for sorting cells on a biophysical basis, the biomechanical stemness markers presented here may enable the rapid purification of LSCs from a heterogeneous population of corneal cells, thus potentially enabling clinicians and researchers to generate corneal transplants with sufficiently high fractions of LSCs, regardless of the LSC percentage in the donor tissue.

Proangiogenic effects of soluble α-Klotho on systemic sclerosis dermal microvascular endothelial cells

Background

Systemic sclerosis (SSc) is characterized by endothelial cell (EC) apoptosis, impaired angiogenesis and peripheral microvasculopathy. Soluble α-Klotho (sKl) is a pleiotropic molecule with multiple effects on ECs, including antioxidant and vasculoprotective activities. On the EC surface, sKl interacts with vascular endothelial growth factor (VEGF) receptor-2 (VEGFR-2) and transient receptor potential canonical-1 (TRPC-1) cation channel to control EC homeostasis. Here, we investigated whether sKl might act as a protective factor to improve angiogenesis in dermal microvascular endothelial cells (MVECs) from SSc patients (SSc-MVECs).

Methods

Wound healing assay was performed on healthy dermal MVECs (H-MVECs) challenged with sera from healthy controls or SSc patients with or without the addition of sKl. Capillary morphogenesis on Matrigel was assessed in H-MVECs and SSc-MVECs at basal conditions and treated with sKl, as well as in H-MVECs challenged with healthy or SSc sera in presence or absence of sKl. The expression of α-Klotho, VEGF₁₆₅b, VEGFR-2, TRPC-1, Ki67 and active caspase-3 in H-MVECs and SSc-MVECs was investigated by western blotting. Immunostaining for α-Klotho was performed in H-MVECs and SSc-MVECs, and in healthy and SSc skin sections.

Results

Treatment with sKl effectively counteracted the inihibitory effects of SSc sera on wound healing ability and angiogenic performance of H-MVECs. The addition of sKl significantly improved angiogenesis and maintained over time capillary-like tube formation in vitro by SSc-MVECs. Stimulation of SSc-MVECs with sKl resulted in the upregulation of the proliferation marker Ki67 in parallel with the downregulation of proapoptotic active caspase-3. The expression of α-Klotho was significantly lower in SSc-MVECs than in H-MVECs. The expression of TRPC-1 was also significantly decreased, while that of VEGFR-2 and VEGF₁₆₅b was significantly increased, in SSc-MVECs compared with H-MVECs. Challenge with sKl either significantly increased TRPC-1 or decreased VEGF₁₆₅b in SSc-MVECs. Ex vivo analyses revealed that α-Klotho immunostaining was almost absent in the dermal microvascular network of SSc skin compared with control skin.

Conclusions

Our findings provide the first evidence that α-Klotho is significantly decreased in the microvasculature in SSc skin and that sKl administration may effectively improve SSc-MVEC functions in vitro by acting as a powerful proangiogenic factor.

Aging of Stem and Progenitor Cells: Mechanisms, Impact on Therapeutic Potential, and Rejuvenation

It was once suggested that adult or tissue-specific stem cells may be immortal; however, several recently published data suggest that their efficacy is limited by natural aging in common with most other somatic cell types. Decreased activity of stem cells in old age raises questions as to whether the age of the donor should be considered during stem cell transplantation and at what age the donor stem cells should be harvested to ensure the largest possible number of viable, functional, and non-altered stem cells. Although stem cells remain active into old age, changes in stem cells and their microenvironments inhibit their regenerative potential. The impact of aging on stem cell populations differs between tissues and depends on a number intrinsic and extrinsic factors, including systemic changes associated with immune system alterations. In this review, we describe key mechanisms of stem and progenitor cell aging and techniques that are currently used to identify signs of stem cells aging. Furthermore, we focus on the impact of aging on the capacity for proliferation, differentiation, and clinical use of stem cells. Finally, we detail the aging of embryonic, mesenchymal, and induced pluripotent stem cells, with particular emphasis on aging mechanisms and rejuvenation.

Cell Electrical Impedance as a Novel Approach for Studies on Senescence Not Based on Biomarkers

Senescence of cardiac myocytes is frequently associated with heart diseases. To analyze senescence in cardiac myocytes, a number of biomarkers have been isolated. However, due to the complex nature of senescence, multiple markers are required for a single assay to accurately depict complex physiological changes associated with senescence. In single cells, changes in both cytoplasm and cell membrane during senescence can affect the changes in electrical impedance. Based on this phenomenon, we developed MEDoS, a novel microelectrochemical impedance spectroscopy for diagnosis of senescence, which allows us to precisely measure quantitative changes in electrical properties of aging cells. Using cardiac myocytes isolated from 3-, 6-, and 18-month-old isogenic zebrafish, we examined the efficacy of MEDoS and showed that MEDoS can identify discernible changes in electrical impedance. Taken together, our data demonstrated that electrical impedance in cells at different ages is distinct with quantitative values; these results were comparable with previously reported ones. Therefore, we propose that MEDoS be used as a new biomarker-independent methodology to obtain quantitative data on the biological senescence status of individual cells.

Immortalization of human normal and NF1 neurofibroma Schwann cells

Neurofibromas, which are benign Schwann cell tumors, are the hallmark feature in the autosomal dominant condition neurofibromatosis 1 (NF1) and are associated with biallelic loss of NF1 gene function. There is a need for effective therapies for neurofibromas, particularly the larger, plexiform neurofibromas. Tissue culture is an important tool for research. However, it is difficult to derive enriched human Schwann cell cultures, and most enter replicative senescence after 6-10 passages, impeding cell-based research in NF1. Through exogenous expression of human telomerase reverse transcriptase and murine cyclin-dependent kinase (mCdk4), normal (NF1 wild-type), neurofibroma-derived Schwann cells heterozygous for NF1 mutation, and neurofibroma-derived Schwann cells homozygous for NF1 mutation were immortalized, including some matched samples from the same NF1 patient. Initial experiments employed retroviral vectors, while subsequent work utilized lentiviral vectors carrying these genes because of improved efficiency. Expression of both transgenes was required for immortalization. Molecular and immunohistochemical analysis indicated that these cell lines are of Schwann cell lineage and have a range of phenotypes, many of which are consistent with their primary cultures. This is the first report of immortalization and detailed characterization of multiple human NF1 normal nerve and neurofibroma-derived Schwann cell lines, which will be highly useful research tools to study NF1 and other Schwann tumor biology and conditions.

Prevention of hair graying by factors that promote the growth and differentiation of melanocytes

Epidermal melanocyte precursors migrate into developing hair follicles to form the melanocyte stem cell system required to supply pigmented melanocytes necessary for hair pigmentation in repetitive hair cycles. Hair graying is caused by irreversible defects in the self-renewal and/or development of follicular melanocyte stem cells in the hair follicles. To investigate the mechanism(s) of hair graying during the normal aging process, we established a hair graying model in mice by repeatedly plucking or shaving trunk hairs. We repeatedly plucked or shaved trunk hairs to induce and accelerate the hair graying and counted the gray hairs. By using this functional model of hair graying in mice, we assessed the effects of genes known to affect melanocyte development, such as Kitl, hepatocyte growth factor (HGF) and endotheline 3 (ET3). After increasing the total numbers of cumulative hair cycles by plucking or shaving, we observed a significant increase in the gray hair of C57BL/6 mice. Kitl expression in the skin was the most effective for preventing hair graying and a significant effect was also confirmed for HGF and ET3 expression. The repeated hair plucking or shaving led to hair graying without any genetic lesion. Kitl is a more effective factor for prevention of hair graying than HGF or ET3. Our simple model of hair graying may provide a basic tool for screening the molecules or reagents preventing the progression of hair graying.

Tissue formation and tissue engineering through host cell recruitment or a potential injectable cell-based biocomposite with replicative potential: Molecular mechanisms controlling cellular senescence and the involvement of controlled transient telomerase activation therapies

Accumulated data indicate that wound-care products should have a composition equivalent to that of the skin: a combination of particular growth factors and extracellular matrix (ECM) proteins endogenous to the skin, together with viable epithelial cells, fibroblasts, and mesenchymal stem cells (MSCs). Strategies consisting of bioengineered dressings and cell-based products have emerged for widespread clinical use; however, their performance is not optimal because chronic wounds persist as a serious unmet medical need. Telomerase, the ribonucleoprotein complex that adds telomeric repeats to the ends of chromosomes, is responsible for telomere maintenance, and its expression is associated with cell immortalization and, in certain cases, cancerogenesis. Telomerase contains a catalytic subunit, the telomerase reverse transcriptase (hTERT). Introduction of TERT into human cells extends both their lifespan and their telomeres to lengths typical of young cells. The regulation of TERT involves transcriptional and posttranscriptional molecular biology mechanisms. The manipulation, regulation of telomerase is multifactorial in mammalian cells, involving overall telomerase gene expression, post-translational protein-protein interactions, and protein phosphorylation. Reactive oxygen species (ROS) have been implicated in aging, apoptosis, and necrosis of cells in numerous diseases. Upon production of high levels of ROS from exogenous or endogenous generators, the redox balance is perturbed and cells are shifted into a state of oxidative stress, which subsequently leads to modifications of intracellular proteins and membrane lipid peroxidation and to direct DNA damage. When the oxidative stress is severe, survival of the cell is dependent on the repair or replacement of damaged molecules, which can result in induction of apoptosis in the injured with ROS cells. ROS-mediated oxidative stress induces the depletion of hTERT from the nucleus via export through the nuclear pores. Nuclear export is initiated by ROS-induced phosphorylation of tyrosine 707 within hTERT by the Src kinase family. It might be presumed that protection of mitochondria against oxidative stress is an important telomere length-independent function for telomerase in cell survival. Biotechnology companies are focused on development of therapeutic telomerase vaccines, telomerase inhibitors, and telomerase promoter-driven cell killing in oncology, have a telomerase antagonist in late preclinical studies. Anti-aging medicine-oriented groups have intervened on the market with products working on telomerase activation for a broad range of degenerative diseases in which replicative senescence or telomere dysfunction may play an important role. Since oxidative damage has been shown to shorten telomeres in tissue culture models, the adequate topical, transdermal, or systemic administration of antioxidants (such as, patented ocular administration of 1% N-acetylcarnosine lubricant eye drops in the treatment of cataracts) may be beneficial at preserving telomere lengths and delaying the onset or in treatment of disease in susceptible individuals. Therapeutic strategies toward controlled transient activation of telomerase are targeted to cells and replicative potential in cell-based therapies, tissue engineering and regenerative medicine.

Uncoupling of Elastin Complex Receptor during In Vitro Aging Is Related to Modifications in Its Intrinsic Sialidase Activity and the Subsequent Lactosylceramide Production

Degradation of elastin leads to the production of elastin-derived peptides (EDP), which exhibit several biological effects, such as cell proliferation or protease secretion. Binding of EDP on the elastin receptor complex (ERC) triggers lactosylceramide (LacCer) production and ERK1/2 activation following ERC Neu-1 subunit activation. The ability for ERC to transduce signals is lost during aging, but the mechanism involved is still unknown. In this study, we characterized an in vitro model of aging by subculturing human dermal fibroblasts. This model was used to understand the loss of EDP biological activities during aging. Our results show that ERC uncoupling does not rely on Neu-1 or PPCA mRNA or protein level changes. Furthermore, we observe that the membrane targeting of these subunits is not affected with aging. However, we evidence that Neu-1 activity and LacCer production are altered. Basal Neu-1 catalytic activity is strongly increased in aged cells. Consequently, EDP fail to promote Neu-1 catalytic activity and LacCer production in these cells. In conclusion, we propose, for the first time, an explanation for ERC uncoupling based on the age-related alterations of Neu-1 activity and LacCer production that may explain the loss of EDP-mediated effects occurring during aging.

A novel ATM/TP53/p21-mediated checkpoint only activated by chronic γ-irradiation

Different levels or types of DNA damage activate distinct signaling pathways that elicit various cellular responses, including cell-cycle arrest, DNA repair, senescence, and apoptosis. Whereas a range of DNA-damage responses have been characterized, mechanisms underlying subsequent cell-fate decision remain elusive. Here we exposed cultured cells and mice to different doses and dose rates of γ-irradiation, which revealed cell-type-specific sensitivities to chronic, but not acute, γ-irradiation. Among tested cell types, human fibroblasts were associated with the highest levels of growth inhibition in response to chronic γ-irradiation. In this context, fibroblasts exhibited a reversible G1 cell-cycle arrest or an irreversible senescence-like growth arrest, depending on the irradiation dose rate or the rate of DNA damage. Remarkably, when the same dose of γ-irradiation was delivered chronically or acutely, chronic delivery induced considerably more cellular senescence. A similar effect was observed with primary cells isolated from irradiated mice. We demonstrate a critical role for the ataxia telangiectasia mutated (ATM)/tumor protein p53 (TP53)/p21 pathway in regulating DNA-damage-associated cell fate. Indeed, blocking the ATM/TP53/p21 pathway deregulated DNA damage responses, leading to micronucleus formation in chronically irradiated cells. Together these results provide insights into the mechanisms governing cell-fate determination in response to different rates of DNA damage.

In vitro lifespan and senescence mechanisms of human nucleus pulposus chondrocytes

BACKGROUND CONTEXT

Our previous in vivo study demonstrated that human nucleus pulposus chondrocytes (NPCs) in aging discs exhibited characteristic senescent features such as an increased senescence-associated β-galactosidase (SA-β-gal) expression, shortened telomere, and decreased telomerase activity. The replicative p53-p21-pRB pathway, rather than the stress-induced p16-pRB pathway, played a more important role in the senescence of NPCs in an in vivo condition, although there is a situation in which both the pathways can be activated simultaneously. However, the in vitro lifespan and senescence mechanisms of human NPCs remain unclear.

PURPOSE

To evaluate the underlying mechanisms of in vitro lifespan and in vitro senescence of the human NPCs and to verify whether the in vitro senescence mechanisms of the human NPC can represent the in vivo aging mechanisms of the cell.

STUDY DESIGN/SETTING

An in vitro study.

METHODS

We serially cultivated human NPCs from patients of different ages (35, 42, 55, 66, and 76 years) until the cells reached the end of their in vitro lifespan. During each subcultivation, we calculated NPCs cumulative population doubling level (PDL) and examined senescence markers (SA-β-gal, telomere length, telomerase activity, and p53, p21, pRB, and p16 expressions).

RESULTS

The cumulative PDLs of the NPCs from patients aged 35, 42 55, 66, and 76 years were 32, 29, 11, 9, and 11, respectively. The younger patients (35 and 42 years) had a higher mean of cumulative PDLs than the elderly patients did (55, 66, and 76 years; 30.5 vs. 10.3; p=.001). In addition, there was a significant, negative correlation between the cumulative PDLs and patient's age (r=-0.89; p=.04). With advancing culture passages, the NPCs irrespective of patient's age exhibited characteristic senescent features, such as an increase in SA-β-gal expression, shortening of telomeres, decrease in telomerase activity, and activation of both replicative p53-p21-pRB and stress-induced p16-pRB pathways. However, all the senescent features occurred at the earlier passages in elderly compared with younger patients.

CONCLUSIONS

The present study demonstrated that the human NPCs had a finite in vitro lifespan, which declined with host aging. The in vitro lifespan was determined by both replicative and stress-induced senescence mechanisms. The similarity in the in vitro senescent features with those apparent in the previous in vivo study suggests a possibility of the in vitro senescence mechanisms of the human NPC as a model of the in vivo aging mechanisms of the cell for future studies.

Determination of critical factors causing cytotoxicity in the virus neutralization test

The fluorescent antibody virus neutralization (FAVN) test, an international standard method for serological testing for rabies, has been adopted by many countries. However, some dog serum samples inhibit the formation of cell monolayers by BHK-21 cells used in the test, resulting in failures to determine antibody titers. This inhibition of cell monolayer formation was defined as cytotoxicity. In this study, critical factors that induce cytotoxicity of the dog serum in BHK-21 cells were determined, and the effective ways to prevent cytotoxicity were also established. Specifically, some anticoagulants, anti-BHK-21 cell IgG antibodies, and serum storage at temperatures of >25°C were found to induce cytotoxicity. On the other hand, several treatments of the dog serum, including the absorption by BHK-21 cells or kaolin, incubation with trypsin-EDTA, and the use of collagen- or gelatin-coated plates, were shown to reduce cytotoxicity. Based on these results, the FAVN test may be modified to enhance its performance.

Endothelial cells expressing low levels of CD143 (ACE) exhibit enhanced sprouting and potency in relieving tissue ischemia

The sprouting of endothelial cells from pre-existing blood vessels represents a critical event in the angiogenesis cascade. However, only a fraction of cultured or transplanted endothelial cells form new vessels. Moreover, it is unclear whether this results from a stochastic process or instead relates to certain endothelial cells having a greater angiogenic potential. This study investigated whether there exists a sub-population of cultured endothelial cells with enhanced angiogenic potency in vitro and in vivo. First, endothelial cells that participated in sprouting, and non-sprouting cells, were separately isolated from a 3D fibrin gel sprouting assay. Interestingly, the sprouting cells, when placed back into the same assay, displayed a sevenfold increase in the number of sprouts, as compared to control cells. Angiotensin-converting enzyme (CD143) was significantly down regulated on sprouting cells, as compared to regular endothelial cells. A subset of endothelial cells with low CD143 expression was then prospectively isolated from an endothelial cell culture. Finally, these cells were found to have greater potency in alleviating local ischemia, and restoring regional blood perfusion when transplanted into ischemic hindlimbs, as compared to unsorted endothelial cells. In summary, this study indicates that low expression of CD143 can be used as a biomarker to identify an endothelial cell sub-population that is more capable to drive neovascularization.

Cdc42 and aging of hematopoietic stem cells

PURPOSE OF REVIEW

Hematopoietic stem cells (HSCs) continuously provide mature blood cells during the lifespan of a mammal. The functional decline in hematopoiesis in the elderly, which involves a progressive reduction in the immune response and an increased incidence of myeloid malignancy, is partly linked to HSC aging. Molecular mechanisms of HSC aging remain unclear, hindering rational approaches to slow or reverse the decline of HSC function with age. Identifying conditions under which aged HSCs become equivalent to young stem cells might result in treatments for age-associated imbalances in lymphopoiesis and myelopoiesis and in blood regeneration.

RECENT FINDINGS

Aging of HSCs has been for a long time thought to be an irreversible process imprinted in stem cells due to the intrinsic nature of HSC aging. Mouse model studies have found that aging is associated with elevated activity of the Rho GTPase Cdc42 in HSCs that is causative for loss of polarity, altered epigenetic modifications and functional deficits of aged HSCs. The work suggests that inhibition of Cdc42 activity in aged HSCs may reverse a number of phenotypes associated with HSC aging.

SUMMARY

Maintaining the regenerative capacity of organs or organ systems may be a useful way to ensure healthy aging. A defined set of features phenotypically separate young from aged HSCs. Aging of HSCs has been thought to be irreversible. Recent findings support the hypothesis that functional decline of aged HSCs may be reversible by pharmacological intervention of age altered signaling pathways and epigenetic modifications.

Changes in cultured dermal fibroblasts during early passages across five wild bird species

With the advent of the usage of primary fibroblasts in comparative and evolutionary biology, it is important for researchers to know the extent to which cells might be altered during the culturing process and how much species might differ in response to cell culture. We compared early changes in cell size and lipid composition of primary dermal fibroblasts grown at physiologically relevant oxygen concentrations (5% O2) from wild-caught species of birds. Fibroblasts from American Robins (Turdus migratorius L., 1766) and Bobwhite Quails (Colinus virginianus (L., 1758)) increased in size early in the culture process and cells from all five species of wild-caught birds exhibited changes in lipid-class composition. The two most common phospholipids, phosphatidylcholine and phosphatidylethanolamine, increased in concentration in all species between early passages and later passages of fibroblasts. Some less abundant lipid species, such as cardiolipin and sphingomyelin, exhibited similar concentrations in all three passages that we measured. Other lipid classes, such as cholesterol, increased in some species in later passages and decreased in others. Although results may vary with cell-culture conditions, this study points to a need for researchers comparing multiple species to take precautions when using cell culture, such as experimenting on the earliest possible passage of cells.

Age-associated changes in the ecological niche: implications for mesenchymal stem cell aging

Adult stem cells are critical for organ-specific regeneration and self-renewal with advancing age. The prospect of being able to reverse tissue-specific post-injury sequelae by harvesting, culturing and transplanting a patient's own stem and progenitor cells is exciting. Mesenchymal stem cells have emerged as a reliable stem cell source for this treatment modality and are currently being tested in numerous ongoing clinical trials. Unfortunately, the fervor over mesenchymal stem cells is mitigated by several lines of evidence suggesting that their efficacy is limited by natural aging. This article discusses the mechanisms and manifestations of age-associated deficiencies in mesenchymal stem cell efficacy. A consideration of recent experimental findings suggests that the ecological niche might be responsible for mesenchymal stem cell aging.

Effects of long-term serial cell passaging on cell spreading, migration, and cell-surface ultrastructures of cultured vascular endothelial cells

The effects of serial cell passaging on cell spreading, migration, and cell-surface ultrastructures have been less investigated directly. This study evaluated the effects of long-term serial cell passaging (totally 35 passages) on cultured human umbilical vein endothelial cells which were pre-stored at -80 °C as usual. Percentage- and spread area-based spreading assays, measurements of fluorescently labeled actin filaments, migration assay, and measurements of cell-surface roughness were performed and quantitatively analyzed by confocal microscopy or atomic force microscopy. We found that the abilities of cell spreading and migration first increased at early passages and then decreased after passage 15, in agreement with the changes in average length of actin filaments. Recovery from cold storage and effects of cell passaging were potentially responsible for the increases and decreases of the values, respectively. In contrast, the average roughness of cell surfaces (particularly the nucleus-surrounding region) first dropped at early passages and then rose after passage 15, which might be caused by cold storage- and cell passaging-induced endothelial microparticles. Our data will provide important information for understanding serial cell passaging and implies that for pre-stored adherent cells at -80 °C cell passages 5-10 are optimal for in vitro studies.

Comparative Evaluation of Human Mesenchymal Stem Cells of Fetal (Wharton's Jelly) and Adult (Adipose Tissue) Origin during Prolonged In Vitro Expansion: Considerations for Cytotherapy

Mesenchymal stem cells (MSCs) are somatic cells with a dual capacity for self-renewal and differentiation, and diverse therapeutic applicability, both experimentally and in the clinic. These cells can be isolated from various human tissues that may differ anatomically or developmentally with relative ease. Heterogeneity due to biological origin or in vitro manipulation is, nevertheless, considerable and may equate to differences in qualitative and quantitative characteristics which can prove crucial for successful therapeutic use. With this in mind, in the present study we have evaluated the proliferation kinetics and phenotypic characteristics of MSCs derived from two abundant sources, that is, fetal umbilical cord matrix (Wharton's jelly) and adult adipose tissue (termed WJSC and ADSC, resp.) during prolonged in vitro expansion, a process necessary for obtaining cell numbers sufficient for clinical application. Our results show that WJSC are derived with relatively high efficiency and bear a substantially increased proliferation capacity whilst largely sustaining the expression of typical immunophenotypic markers, whereas ADSC exhibit a reduced proliferation potential showing typical signs of senescence at an early stage. By combining kinetic with phenotypic data we identify culture thresholds up to which both cell types maintain their stem properties, and we discuss the practical implications of their differences.

Establishment and characterization of fetal fibroblast cell lines for generating human lysozyme transgenic goats by somatic cell nuclear transfer

This study was performed to qualify goat fetal fibroblast (GFF) cell lines for genetic modification and somatic cell nuclear transfer (SCNT) to produce human lysozyme (hLYZ) transgenic goats. Nine GFF cell lines were established from different fetuses, and the proliferative lifespan and chromosomal stability were analyzed. The results suggested that cell lines with a longer lifespan had stable chromosomes compared with those of cells lines with a shorter lifespan. According to the proliferative lifespan, we divided GFF cell lines into two groups: cell lines with a long lifespan (GFF1/2/7/8/9; group L) and cell lines with a short lifespan (GFF3/4/5/6; group S). Next, a hLYZ expression vector was introduced into these cell lines by electroporation. The efficiencies of colony formation, expansion in culture, and the quality of transgenic clonal cell lines were significant higher in group L than those in group S. The mean fusion rate and blastocyst rate in group L were higher than those in group S (80.3 ± 1.7 vs. 65.1 ± 4.2 % and 19.5 ± 0.6 vs. 15.1 ± 1.1 %, respectively, P < 0.05). After transferring cloned embryos into the oviducts of recipient goats, three live kids were born. PCR and Southern blot analyses confirmed integration of the transgene in cloned goats. In conclusion, the lifespan of GFF cell lines has a major effect on the efficiency to produce transgenic cloned goats. Therefore, the proliferative lifespan of primary cells may be used as a criterion to characterize the quality of cell lines for genetic modification and SCNT.

Cell senescence culturing methods

Development of therapeutic approaches that slow or ablate the adverse physiological and pathological changes associated with aging has been considered as an important goal for gerontological research. As cellular senescence is characterized as the basis for aging in organisms, culturing and subculturing of normal human diploid fibroblasts to mimic the in vivo aging processes have been developed as major methods to investigate molecular events involved in aging. It has been established that normal human diploid fibroblasts can proliferate in culture for only finite periods of time. There are many ways to study aging in vitro. In this chapter, we will discuss some of the basic laboratory procedures for cell senescence culturing methods.

Bone marrow derived mesenchymal stem cells from aged mice have reduced wound healing, angiogenesis, proliferation and anti-apoptosis capabilities

Decline in the function of stem cells with age, such as other cells of the body, results in an imbalance between loss and renewal. Increasing age of the donor thus diminishes the effectiveness of MSCs (mesenchymal stem cells) transplantation in age-related diseases. The clinical use of stem cell therapies needs autologous stem cell transplantation; it is essential therefore to study the repair ability and survivability of cells before transplantation. Bone marrow derived MSCs possess multi-lineage differentiation potential, but aging adversely affects their therapeutic efficacy. MSCs from young (2-3 months) and aged (23-24 months) GFP (green fluorescent protein)-expressing C57BL/6 mice were isolated and their regenerative potential was assessed in vitro. Real-time RT-PCR (reverse transcriptase-PCR) showed significantly higher expression of Sirt1 in MSCs isolated from young than older animals. Down-regulation of VEGF (vascular endothelial growth factor), SDF-1 (stromal-cell-derived factor 1), AKT (also known as protein kinase B) and up-regulation of p53, p21, Bax and p16 occurred in aged cells. Tube formation, wound healing and proliferative abilities of the young MSCs were better than the aged MSCs. The results suggest that age-related increased expression of apoptotic and senescent genes, with concomitant decrease in Sirt1 gene expression, inhibits to some extent stem cell functioning.

Explaining differences in the lifespan and replicative capacity of cells: a general model and comparative analysis of vertebrates

A better understanding of the factors that govern individual cell lifespan and the replicative capacity of cells (i.e. Hayflick's limit) is important for addressing disease progression and ageing. Estimates of cell lifespan in vivo and the replicative capacity of cell lines in culture vary substantially both within and across species, but the underlying reasons for this variability remain unclear. Here, we address this issue by presenting a quantitative model of cell lifespan and cell replicative capacity. The model is based on the relationship between cell mortality and metabolic rate, which is supported with data for different cell types from ectotherms and endotherms. These data indicate that much of the observed variation in cell lifespan and cell replicative capacity is explained by differences in cellular metabolic rate, and thus by the three primary factors that control metabolic rate: organism size, organism temperature and cell size. Individual cell lifespan increases as a power law with both body mass and cell mass, and decreases exponentially with increasing temperature. The replicative capacity of cells also increases with body mass, but is independent of temperature. These results provide a point of departure for future comparative studies of cell lifespan and replicative capacity in the laboratory and in the field.

Nuclear ribonucleoprotein-containing foci increase in size in non-dividing cells from patients with myotonic dystrophy type 2

Myotonic dystrophies (DM) are genetically based neuromuscular disorders characterized by the accumulation of mutant transcripts into peculiar intranuclear foci, where different splicing factors (among which the alternative splicing regulator muscleblind-like 1 protein, MBNL1) are ectopically sequestered. The aim of the present investigation was to describe the dynamics of the DM-specific intranuclear foci in interphase nuclei and during mitosis, as well as after the exit from the cell cycle. Primary cultures of skin fibroblasts from DM2 patients were used, as a model system to reproduce in vitro, as accurately as possible, the in vivo conditions. Cycling and resting fibroblasts were investigated by immunocytochemical and morphometric techniques, and the relative amounts of MBNL1 were also estimated by western blotting. MBNL1-containing foci were exclusively found in the nucleus during most of the interphase, while being observed in the cytoplasm during mitosis when they never associate with the chromosomes; the foci remained in the cytoplasm at cytodieresis, and underwent disassembly in early G1 to be reformed in the nucleus at each cell cycle. After fibroblasts had stopped dividing in late-passage cultures, the nuclear foci were observed to progressively increase in size. Interestingly, measurements on muscle biopsies taken from the same DM2 patients at different ages demonstrated that, in the nuclei of myofibers, the MBNL1-containing foci become larger with increasing patient's age. As a whole, these results suggest that in non-dividing cells of DM2 patients the sequestration in the nuclear foci of factors needed for RNA processing would be continuous and progressive, eventually leading to the onset (and the worsening with time) of the pathological traits. This is consistent with the evidence that in DM patients the most affected organs or tissues are those where non-renewing cells are mainly present, i.e., the central nervous system, heart and skeletal muscle.

Characterization and modulation of fibroblast/endothelial cell co-cultures for the in vitro preformation of three-dimensional tubular networks

Various assays of different complexity are used in research on angiogenesis in health and disease. The results of these assays increasingly impact the field of tissue engineering because preformed microvascular networks may connect and conduct to the vascular system of the host, thereby helping us to support the survival of implanted cells and tissue constructs. An interesting model that supports the formation of EC (endothelial cells) tubular structures in vitro is based on co-culturing them with fibroblasts. Our initial multilayer approach was recently transferred into a three-dimensional spheroid model using HUVEC (human umbilical vein endothelial cells) as model cells. The aim of the present study is to further characterize, extend and validate this fibroblast/EC spheroid co-culture system. We have evaluated the model with a maximum size of 600-650 μm attained on day 3 from inoculation of 4×104 fibroblasts with 1×104 EC. Cell count and spheroid diameter significantly decreased as a function of time, but the EC network that developed over a period of 14 days in culture was clearly visible and viable, and central cell death was excluded. We successfully included HMVEC (human microvascular endothelial cells) of dermal origin in the system and replaced FBS (fetal bovine serum) with human AB serum, which positively impacted the EC network formation at optimized concentrations. The need for exogenous growth factors [VEGF (vascular endothelial growth factor), EGF (epithelial growth factor), bFGF (basic fibroblast growth factor) and IGF-1 (insulin-like growth factor-1)] routinely added to classical EC media was also assessed. The behaviour of both fibroblasts and EC in response to a combination of these exogenous growth factors differed critically in fibroblast/EC spheroid co-cultures compared with the same cells in the multilayer approach. VEGF was the most relevant exogenous factor for EC network formation in fibroblast/EC multilayers, but was ineffective in the spheroid system. IGF-1 was found, in general, to be dispensable; however, while it had a negative impact on EC networking in the presence of bFGF and EGF in the multilayer, it did not in the spheroid approach. We conclude that the critical determinants of EC network formation and cell survival are not universal, but have to be specifically optimized for each culture model.

Regenerative potential of human muscle stem cells in chronic inflammation

Introduction

Chronic inflammation is a profound systemic modification of the cellular microenvironment which could affect survival, repair and maintenance of muscle stem cells. The aim of this study was to define the role of chronic inflammation on the regenerative potential of satellite cells in human muscle.

Methods

As a model for chronic inflammation, 11 patients suffering from rheumatoid arthritis (RA) were included together with 16 patients with osteoarthritis (OA) as controls. The mean age of both groups was 64 years, with more females in the RA group compared to the OA group. During elective knee replacement surgery, a muscle biopsy was taken from the distal musculus vastus medialis. Cell populations from four RA and eight OA patients were used for extensive phenotyping because these cell populations showed no spontaneous differentiation and myogenic purity greater than 75% after explantation.

Results

After mononuclear cell explantation, myogenic purity, viability, proliferation index, number of colonies, myogenic colonies, growth speed, maximum number of population doublings and fusion index were not different between RA and OA patients. Furthermore, the expression of proteins involved in replicative and stress-induced premature senescence and apoptosis, including p16, p21, p53, hTERT and cleaved caspase-3, was not different between RA and OA patients. Mean telomere length was shorter in the RA group compared to the OA group.

Conclusions

In the present study we found evidence that chronic inflammation in RA does not affect the in vitro regenerative potential of human satellite cells. Identification of mechanisms influencing muscle regeneration by modulation of its microenvironment may, therefore, be more appropriate.

Molecular links between cellular senescence, longevity and age-related diseases - a systems biology perspective

The role of cellular senescence (CS) in age-related diseases (ARDs) is a quickly emerging topic in aging research. Our comprehensive data mining revealed over 250 genes tightly associated with CS. Using systems biology tools, we found that CS is closely interconnected with aging, longevity and ARDs, either by sharing common genes and regulators or by protein-protein interactions and eventually by common signaling pathways. The most enriched pathways across CS, ARDs and aging-associated conditions (oxidative stress and chronic inflammation) are growth-promoting pathways and the pathways responsible for cell-extracellular matrix interactions and stress response. Of note, the patterns of evolutionary conservation of CS and cancer genes showed a high degree of similarity, suggesting the co-evolution of these two phenomena. Moreover, cancer genes and microRNAs seem to stand at the crossroad between CS and ARDs. Our analysis also provides the basis for new predictions: the genes common to both cancer and other ARD(s) are highly likely candidates to be involved in CS and vice versa. Altogether, this study shows that there are multiple links between CS, aging, longevity and ARDs, suggesting a common molecular basis for all these conditions. Modulating CS may represent a potential pro-longevity and anti-ARDs therapeutic strategy.

Chronic inhibition of the respiratory chain in human fibroblast cultures: differential responses related to subject chronological and biological age

Respiratory chain function becomes less efficient with age resulting in increased levels of damaging reactive oxygen species. We compared rotenone-exposed fibroblast strains from young and old subjects and from offspring of nonagenarian siblings and the partners of the offspring. Rotenone increased reactive oxygen species levels, inhibited growth rate, and increased telomere shortening (all p < .05). Non-stressed strains from young subjects showed lower reactive oxygen species levels (p = .031) and higher growth rates (p = .002) than strains from old subjects. Stressed strains from young subjects showed smaller increases in reactive oxygen species levels (p = .014) and larger decreases in growth rate (p < .001) than strains from old subjects. Telomere-shortening rates were not different between groups. Stress-induced decreases in growth rate were larger in strains from offspring than from partners (p = .05). Strains from young and old subjects are differentially affected by chronic inhibition of the respiratory chain. Changed growth rates in strains from offspring resemble those from strains from young subjects.

The role of nanofibrous structure in osteogenic differentiation of human mesenchymal stem cells with serial passage

Using scaffolds with autologous stem cells is a golden strategy for the treatment of bone defects. In this strategy, human mesenchymal stem cells (hMSCs) have often been isolated and expanded in vitro on a plastic surface to obtain a sufficient cell number before seeding on a suitable scaffold. Materials & Methods: Investigating the influence of serial passages (from passage two to passage eight) on the abilities of proliferation and osteogenic differentiation of hMSCs on 24-well tissue culture polystyrene plates and poly L-lactic acid electrospun nanofibrous scaffolds was performed to determine how prolonged culture affected these cellular abilities and how the nanofibrous scaffolds supported the osteogenic differentiation potential of hMSCs. Results & Conclusion: Serial passage caused adverse changes in hMSCs characteristics, which were indicated by the decline in both proliferation and osteogenic differentiation abilities. Interestingly, the poly L-lactic acid nanofibrous scaffolds showed a significant support in recovering the osteogenic abilities of hMSCs, which had been severely affected by prolonged culture.

Investigation of aging effects in human hair using atomic force microscopy

BACKGROUND

A thorough characterization of the morphological structure and physical properties is essential for an understanding of human hair. A number of techniques such as scanning electron microscopy, transmission electron microscopy and confocal microscopy have been used to study hair surfaces. Recently, atomic force microscopy (AFM) has emerged as an ideal method for the non-invasive examination of hair surfaces.

PURPOSE

To investigate the effects of aging on normal Korean hair diameter and surface features using AFM.

METHODS

We enrolled 60 Korean volunteers of various ages who had no hair diseases. We analyzed hair diameter, AFM images of the hair surface, cuticular descriptors and micro-scale mechanical properties for their associations with aging.

RESULTS

Hair diameter was found to increase for the first 20-30 years of life, after which it began to decrease. AFM images of most of the younger subjects showed typical step-like topographic properties with clear scale edges. The AFM images of most of the older subjects revealed dilapidated structures, poorly demarcated scale edges and undulated surfaces. Among the cuticular descriptors, surface roughness increased significantly with age. Force to distance analysis demonstrated a dependence on age.

CONCLUSION

These results suggest that aging causes changes in hair diameter and surface structure.

Keloid explant culture: a model for keloid fibroblasts isolation and cultivation based on the biological differences of its specific regions

In vitro studies with keloid fibroblasts frequently present contradictory results. This may occur because keloids present distinct genotypic and phenotypic characteristics in its different regions, such as the peripheral region in relation to the central region. We suggest an explant model for keloid fibroblasts harvesting, standardising the initial processing of keloid samples to obtain fragments from different regions, considering its biological differences, for primary cell culture. The different keloid regions were delimited and fragments were obtained using a 3-mm diameter punch. To remove fragments from the periphery, the punch was placed in one longitudinal line extremity, respecting the lesion borders. For the central region, it was placed in the intersection of lines at the level of the largest longitudinal and transversal axes, the other fragments being removed centrifugally in relation to the first one. Primary fibroblast culture was carried out by explant. Flow cytometry analysis showed cell cycle differences between the groups, confirming its different origins and biological characteristics. In conclusion, our proposed model proved itself efficient for keloid fibroblast isolation from specific regions and cultivation. Its simplicity and ease of execution may turn it into an important tool for studying the characteristics of the different keloid-derived fibroblasts in culture.

Impact of cellular senescence signature on ageing research

Cellular senescence as the state of permanent inhibition of cell proliferation is a tumour-suppressive mechanism. However, due to the associated secretory phenotype senescence can also contribute to cancer and possibly other age-related diseases, such as obesity, diabetes, atherosclerosis and Alzheimer's disease. There are two major mechanisms of cellular senescence; replicative senescence depends on telomere erosion or dysfunction whilst stress-induced premature senescence (SIPS) is telomere-independent and also includes oncogene-induced senescence (OIS). The senescence phenotype is characterised by altered cellular morphology, increased activity for senescence-associated-β-galactosidase (SA-β-GAL), increased formation of senescence-associated heterochromatin foci (SAHF) and promyelocytic leukemia protein nuclear bodies (PML NBs), permanent DNA damage, chromosomal instability and an inflammatory secretome. Some of these markers have been identified in cells from age-related pathologies. However, to improve our understanding of the contribution of cellular senescence to organismal ageing and age-related disease, it is imperative to define an unequivocal signature of cellular senescence that is functionally connected with normal and pathological ageing. Herein, we describe the processes leading to senescence, and the current biomarkers of cellular senescence, with particular emphasis on the causal role of DNA damage responses involved in the process. We highlight the gaps in our knowledge both of the processes leading to senescence, and the signature of cellular senescence both in vitro and in vivo. A well-defined set of senescence biomarkers for ageing and age-related disease would have a strong impact on the diagnosis, staging and predicted outcomes of age-related disease, providing the basis for a pharmacological intervention to postpone ageing and age-related disease.

Mapping the cellular and molecular heterogeneity of normal and malignant breast tissues and cultured cell lines

Introduction

Normal and neoplastic breast tissues are comprised of heterogeneous populations of epithelial cells exhibiting various degrees of maturation and differentiation. While cultured cell lines have been derived from both normal and malignant tissues, it remains unclear to what extent they retain similar levels of differentiation and heterogeneity as that found within breast tissues.

Methods

We used 12 reduction mammoplasty tissues, 15 primary breast cancer tissues, and 20 human breast epithelial cell lines (16 cancer lines, 4 normal lines) to perform flow cytometry for CD44, CD24, epithelial cell adhesion molecule (EpCAM), and CD49f expression, as well as immunohistochemistry, and in vivo tumor xenograft formation studies to extensively analyze the molecular and cellular characteristics of breast epithelial cell lineages.

Results

Human breast tissues contain four distinguishable epithelial differentiation states (two luminal phenotypes and two basal phenotypes) that differ on the basis of CD24, EpCAM and CD49f expression. Primary human breast cancer tissues also contain these four cellular states, but in altered proportions compared to normal tissues. In contrast, cultured cancer cell lines are enriched for rare basal and mesenchymal epithelial phenotypes, which are normally present in small numbers within human tissues. Similarly, cultured normal human mammary epithelial cell lines are enriched for rare basal and mesenchymal phenotypes that represent a minor fraction of cells within reduction mammoplasty tissues. Furthermore, although normal human mammary epithelial cell lines exhibit features of bi-potent progenitor cells they are unable to differentiate into mature luminal breast epithelial cells under standard culture conditions.

Conclusions

As a group breast cancer cell lines represent the heterogeneity of human breast tumors, but individually they exhibit increased lineage-restricted profiles that fall short of truly representing the intratumoral heterogeneity of individual breast tumors. Additionally, normal human mammary epithelial cell lines fail to retain much of the cellular diversity found in human breast tissues and are enriched for differentiation states that are a minority in breast tissues, although they do exhibit features of bi-potent basal progenitor cells. These findings suggest that collections of cell lines representing multiple cell types can be used to model the cellular heterogeneity of tissues.