Effects of serum from human subjects of various ages on proliferation of human lung and skin fibroblasts

A simple cell proliferation assay and the inflammatory protein content show significant differences in human plasmas from young and old subjects

Some studies showed a "rejuvenating" effect of exposing aging tissues to a young environment. In mouse heterochronic parabiosis experiments, in response to young organisms, old animals lived longer than isochrony old age-matched conjoint animals. Comparable "rejuvenating" effects were obtained by injecting young plasma in old mice. This raised great hopes of slowing down the senescence process in humans by the injection of young plasma, as well as to prevent or cure age-related diseases. Some clinical trials are currently being performed or were recently completed. However, these studies are small and of limited duration, and we still lack convincing evidence to support the effectiveness of young plasma injection. It is urgent to perform additional investigations, including the development of an assay to measure the cell proliferation induction capability of different human plasmas, before one can seriously think of a large-scale treatment of humans. We adopted a simple method to measure the potential of different plasmas in supporting cell line proliferation, regardless of the co-presence of a platelet lysate. By comparing plasmas from young and old subjects, we observed a decreased activity in plasmas from old individuals. The young plasma effect may be attributed to specific proteins and growth factors more abundant in younger individuals that could decrease with age. Alternatively, or at the same time, the reduced cell proliferation support could be due to inhibitors present in the old plasma. Studying the different protein content of young and old plasmas was out of the scope of this article. Such differences should be adequately investigated by proteomics using many samples. However, a preliminary study of the different protein content of young and old plasmas was part of the assay validation using a commercially available cytokine array for parallel determination of the relative levels of 105 selected human proteins. We could show the existence of specific differences between young and old plasmas and that plasmas from old individuals presented a higher concentration of "inflammatory" proteins.

A review of the effects of ageing on skin integrity and wound healing

It is well known that advancing age is a factor that affects the normal course of wound healing. The population over the age of 65 years is increasing globally, and this may be accompanied by an increase in the number of individuals experiencing delayed wound healing. There is a breadth of research to show that age-related changes in the epidermis and dermis change the skin's ability to resist damage and injury. In particular, the dermoepidermal junction becomes flattened, which predisposes the tissue to shear and friction forces. Within the dermis, alterations in the amount and structure of collagen also mean that the tissue is much more rigid. Prompt assessment of the skin to identify existing conditions as well as preventive measures is therefore essential. This article discusses the anatomy of the skin and the effects of ageing on the tissues. It also offers some guidance on skin assessment and the basics of skin care.

Skeletal stem cells and their contribution to skeletal fragility: senescence and rejuvenation

Age-related osteoporotic fractures are major health care problem worldwide and are the result of impaired bone formation, decreased bone mass and bone fragility. Bone formation is accomplished by skeletal stem cells (SSC) that are recruited to bone surfaces from bone marrow microenvironment. This review discusses targeting SSC to enhance bone formation and to abolish age-related bone fragility in the context of using stem cells for treatment of age-related disorders. Recent studies are presented that have demonstrated that SSC exhibit impaired functions during aging due to intrinsic senescence-related changes as well as the presence of senescent microenvironment. Also, a number of approaches aiming at increasing bone formation through targeting SSC and that include systemic SSC transplantation, systemic SSC targeting using aptamers or antibodies, use of therapeutic screteome and tissue engineering approaches will be presented and discussed.

Human platelet lysate: Replacing fetal bovine serum as a gold standard for human cell propagation?

The essential physiological role of platelets in wound healing and tissue repair builds the rationale for the use of human platelet derivatives in regenerative medicine. Abundant growth factors and cytokines stored in platelet granules can be naturally released by thrombin activation and clotting or artificially by freeze/thaw-mediated platelet lysis, sonication or chemical treatment. Human platelet lysate prepared by the various release strategies has been established as a suitable alternative to fetal bovine serum as culture medium supplement, enabling efficient propagation of human cells under animal serum-free conditions for a multiplicity of applications in advanced somatic cell therapy and tissue engineering. The rapidly increasing number of studies using platelet derived products for inducing human cell proliferation and differentiation has also uncovered a considerable variability of human platelet lysate preparations which limits comparability of results. The main variations discussed herein encompass aspects of donor selection, preparation of the starting material, the possibility for pooling in plasma or additive solution, the implementation of pathogen inactivation and consideration of ABO blood groups, all of which can influence applicability. This review outlines the current knowledge about human platelet lysate as a powerful additive for human cell propagation and highlights its role as a prevailing supplement for human cell culture capable to replace animal serum in a growing spectrum of applications.

Donor age of human platelet lysate affects proliferation and differentiation of mesenchymal stem cells

The regenerative potential declines upon aging. This might be due to cell-intrinsic changes in stem and progenitor cells or to influences by the microenvironment. Mesenchymal stem cells (MSC) raise high hopes in regenerative medicine. They are usually culture expanded in media with fetal calf serum (FCS) or other serum supplements such as human platelet lysate (HPL). In this study, we have analyzed the impact of HPL-donor age on culture expansion. 31 single donor derived HPLs (25 to 57 years old) were simultaneously compared for culture of MSC. Proliferation of MSC did not reveal a clear association with platelet counts of HPL donors or growth factors concentrations (PDGF-AB, TGF-β1, bFGF, or IGF-1), but it was significantly higher with HPLs from younger donors (<35 years) as compared to older donors (>45 years). Furthermore, HPLs from older donors increased activity of senescence-associated beta-galactosidase (SA-βgal). HPL-donor age did not affect the fibroblastoid colony-forming unit (CFU-f) frequency, immunophenotype or induction of adipogenic differentiation, whereas osteogenic differentiation was significantly lower with HPLs from older donors. Concentrations of various growth factors (PDGF-AB, TGF-β1, bFGF, IGF-1) or hormones (estradiol, parathormone, leptin, 1,25 vitamin D3) were not associated with HPL-donor age or MSC growth. Taken together, our data support the notion that aging is associated with systemic feedback mechanisms acting on stem and progenitor cells, and this is also relevant for serum supplements in cell culture: HPLs derived from younger donors facilitate enhanced expansion and more pronounced osteogenic differentiation.

Perfringolysin O, a cholesterol-binding cytolysin, as a probe for lipid rafts

Gaining an understanding of the structural and functional roles of cholesterol in membrane lipid rafts is a critical issue in studies on cellular signaling and because of the possible involvement of lipid rafts in various diseases. We have focused on the potential of perfringolysin O (theta-toxin), a cholesterol-binding cytolysin produced by Clostridium perfringens, as a probe for studies on membrane cholesterol. We prepared a protease-nicked and biotinylated derivative of perfringolysin O (BCtheta) that binds selectively to cholesterol in cholesterol-rich microdomains of cell membranes without causing membrane lesions. Since the domains fulfill the criteria of lipid rafts, BCtheta can be used to detect cholesterol-rich lipid rafts. This is in marked contrast to filipin, another cholesterol-binding reagent, which binds indiscriminately to cell cholesterol. Using BCtheta, we are now searching for molecules that localize specifically in cholesterol-rich lipid rafts. Recently, we demonstrated that the C-terminal domain of perfringolysin O, domain 4 (D4), possesses the same binding characteristics as BCtheta. BIAcore analysis showed that D4 binds specifically to cholesterol with the same binding affinity as the full-size toxin. Cell-bound D4 is recovered predominantly from detergent-insoluble, low-density membrane fractions where raft markers, such as cholesterol, flotillin and Src family kinases, are enriched, indicating that D4 also binds selectively to lipid rafts. Furthermore, a green fluorescent protein-D4 fusion protein (GFP-D4) was revealed to be useful for real-time monitoring of cholesterol in lipid rafts in the plasma membrane. In addition, the expression of GFP-D4 in the cytoplasm might allow the investigations of intracellular trafficking of lipid rafts. The simultaneous visualization of lipid rafts in plasma membranes and inside cells might help in gaining a total understanding of the dynamic behavior of lipid rafts.

Inhibition of osteoblast differentiation but not adipocyte differentiation of mesenchymal stem cells by sera obtained from aged females

Aging is associated with decreased osteoblast-mediated bone formation leading to bone loss and increased risk for osteoporotic fractures. However, the cellular mechanisms responsible for impaired osteoblast functions are poorly understood. In the present study, we hypothesized that changes in bone microenvironment composition with aging are responsible for impaired osteoprogenitor cell recruitment and differentiation. As a model for bone microenvironment, we examined the effects of sera obtained from young (age 20-30 year old [yo], n=20) and old (70-84 yo, n=19) healthy female donors on cell proliferation and differentiation capacity into osteoblasts and adipocytes of human mesenchymal stem cells (hMSC). Cell proliferation rate determined by counting cell number was similar when the cells were cultured in the presence of media containing 5% sera from old or from young donors. Similarly, the number of adipocytes and levels of adipocytic gene expression was similar in cultures incubated with sera from young or old donors. We observed decreased osteoblastic gene expression in hMSC cultured either in pooled or individual sera of old donors compared to sera from young donors: core binding factor/runt-related binding factor 2 (Cbfa1/Runx2) 46%+/-2% (P<0.05), alkaline phosphatase (ALP) 45%+/-2% (P<0.05), collagen type I (Col-I) 50%+/-1% (P<0.05), and osteocalcin 65%+/-3% (P<0.05). This down-regulation of the mRNA was accompanied by reduced ALP enzyme activity by 25%+/-1% (P<0.01), immunocytochemical staining for osteoblastic markers: ALP, Col-I, and bone sialoprotein (BSP) as well as reduced in vitro mineralization as determined by Alizarin red staining. In conclusion, age-related changes in the serum composition and possibly hMSC microenvironment may contribute to the impaired osteoblast functions with aging. The factors mediating these changes remain to be determined.

Accumulation of oxidative DNA damage, 8-oxo-2'-deoxyguanosine, and change of repair systems during in vitro cellular aging of cultured human skin fibroblasts

Effects of in vitro cellular aging on the content of 8-oxo-2'-deoxyguanosine, a typical oxidation product of DNA bases, were examined in cultured human skin fibroblasts. The 8-oxo-2'-deoxyguanosine content in the DNA of TIG-3S cells established from skin tissues of a fetal donor increased immediately before the cessation of proliferation. TIG-114 and TIG-104 cells established from skin tissues of adult and aged donors, respectively, showed similar changes in 8-oxo-2'-deoxyguanosine content during in vitro cellular aging. The accumulation of 8-oxo-2'-deoxyguanosine in late-passage cells was dependent on the number of cell divisions, and not on the cultivation time. Increases in the activities of superoxide dismutase and glutathione peroxidase were observed prior to the increase in 8-oxo-2'-deoxyguanosine content, while the catalase activity decreased gradually during in vitro cellular aging at late-passage. Furthermore, the activities of 8-oxo-2'-deoxyguanosine endonuclease and DNA polymerases decreased with the progression of proliferation. These results indicate that defense systems against oxidative stress in late-passage cells remain sufficiently active before the cessation of cell division, but that repair systems against oxidative damage decay at late-passage. Oxidative stress beyond the antioxidant capacity and/or repair activity seems to result in an accumulation of 8-oxo-2'-deoxyguanosine in late-passage cells.

Human fetal skin fibroblast migration stimulated by the autocrine growth factor bFGF is mediated by phospholipase A(2) via arachidonic acid without the involvement of pertussis toxin-sensitive G-protein

We reported previously that human fetal skin fibroblast migration into a denuded area was stimulated by an autocrine factor, basic fibroblast growth factor (bFGF). Since the signal transduction pathway of this migration is unknown, we attempted to clarify it by comparing this fibroblast migration with a previously reported bovine endothelial cell migration into a wounded area stimulated by an addition of bFGF, in which the bFGF signal was mediated by phospholipase A(2)-coupled G-protein and phospholipase A(2) (PLA(2)) via arachidonic acid. Our study demonstrated that pertussis toxin, a specific inhibitor of PLA(2)-coupled G-protein, did not suppress human fetal skin fibroblast migration, but 2-(p-amylcinnamyl)amino-4-chlorobensoic acid (ONO-RS-082), a PLA(2) inhibitor, did. Since ONO-RS-082 is a non-specific PLA(2) inhibitor, a cytoplasmic, Ca-dependent PLA(2) (cPLA(2)) inhibitor, AACOCF3, was examined. AACOCF3 suppressed cell migration in certain concentrations. The PLA(2) inhibitor-suppressed cell migration was restored by adding arachidonic acid, and cell migration suppressed by anti-bFGF antibodies was restored by adding arachidonic acid. In addition, pertussis toxin did not suppress arachidonic acid release, which shows an action of PLA(2), but AACOCF3 did. These results indicate that human fetal skin fibroblast migration stimulated by an autocrine factor, bFGF, was mediated by PLA(2) via arachidonic acid without the involvement of PLA(2)-coupled G-protein.

Inhibitory effects of human serum on human fetal skin fibroblast migration: migration-inhibitory activity and substances in serum, and its age-related changes

In order to clarify the environmental factors modulating cell migration, we investigated the effects of human serum on cell migration, and found that serum from adult donors strongly (by 48%) suppressed the migration of human fetal skin fibroblasts into a denuded area in a cell monolayer. Human serum from old donors inhibited cell migration more strongly than that from adult donors. Next, we investigated the properties of migration-inhibitory activity of human serum and serum proteins in order to identify migration-inhibitory substances. Human serum from adult donors strongly suppressed the migration of human fetal skin fibroblasts, although it stimulated cell proliferation more strongly than fetal bovine serum (FBS), indicating that the inhibitory effects of human serum on cell migration was not due to its toxic effects. The inhibition of cell migration by human serum was concentration dependent. It was demonstrated that the inhibition did not depend on the inhibitory effects of human serum on collagen synthesis. The migration-inhibitory activity was seen in fractions over 100 kDa, as determined by an ultrafiltration membrane, and no inhibitory activity was observed in fractions under 100 kDa. On the other hand, it was not detected either in fractions over 100 kDa or under 100 kDa in FBS. Among the over 100 kDa human serum proteins examined, gamma-globulin, alpha2-macroglobulin, and low density lipoprotein (LDL) suppressed fibroblast migration in a concentration-dependent manner. However, among the three, cell migration-inhibiting activity of gamma-globulin almost disappeared when cell migration was conducted in 10% FBS-supplemented medium. These results indicated that alplha2-macroglobulin and LDL were candidate substances for cell migration-inhibiting activity in human serum.

Interferon-beta, an autocrine cytokine, suppresses human fetal skin fibroblast migration into a denuded area in a cell monolayer but is not involved in the age-related decline of cell migration

The migration of human skin fibroblasts into a denuded area in a cell monolayer declined during in vitro and in vivo aging. We carried out a study to determine whether this age-related decline in cell migration was mediated by the autocrine cytokine interferon-beta (IFN-beta), which has been reported to suppress the proliferation, chemotaxis and collagen synthesis of human fibroblasts. Actually, IFN-beta specifically suppressed the migration of TIG-3S human fetal skin fibroblasts into a denuded area in a cell monolayer, as shown by the dose response experiments of IFN-beta and neutralizing anti-IFN-beta antibody. IFN-beta also inhibited their collagen synthesis but the addition of type I collagen could not reverse IFN-beta-induced inhibition of cell migration. Double strand RNA, which has been generally known to induce IFN-beta in human skin fibroblasts, suppressed the migration of TIG-3S cells. Next, a study was done to determine whether IFN-beta and double strand RNA suppressed the migration of TIG-3S cells in late passages as well as early passages, or whether neutralizing anti-IFN-beta antibody stimulated the migration of TIG-3S cells in late and middle passages. IFN-beta and double strand RNA suppressed the migration of TIG-3S cells in middle (PD45) and late (PD55) passages as well as in early passages (PD23-28). Neutralizing anti-IFN-beta antibodies could not reverse the low migratory activity of middle and late passage cells to the high migratory activity of early passage cells. These results indicated that the autocrine cytokine IFN-beta did not seem to be involved in the age-dependent decline of fibroblast migration.

Effects of aging and dietary restriction on activity of monkey serum in promoting fibroblast migration

In order to determine whether serum modified cellular aging in vivo, we previously studied the effects of serum from various mammals of different ages on cell functions such as proliferation and migration, and reported that cell migration was more greatly inhibited by serum from old donors than cell proliferation [1]. Moreover, since dietary restriction has been reported to extend lifespan and slow the aging rate of some animals [2], we wondered whether sera from dietary restricted and control monkeys of various ages might exhibit reduced aging effects on cell migration. When serum from young adult (3-5 years old) monkeys was added to plain medium, the migration of human fetal skin fibroblasts was very strongly inhibited compared to FBS. Surprisingly, sera from adult (6-11 years old) and old (more than 18 years old) monkeys caused significantly less migration-inhibitory activity than serum from young adult monkeys although sera from adult and old monkeys were much more inhibitory to cell migration than FBS. Dietary restriction only caused marginal effects on serum migration-promoting activity in a few monkey groups. The inhibition of cell migration caused by monkey serum was not brought about by cytotoxic effects since monkey serum stimulated cell proliferation as well as fetal bovine serum. These results indicate that the effects of aging on monkey serum migration-promoting activity are much more pronounced than those of dietary restriction.

Autonomous migration of human fetal skin fibroblasts into a denuded area in a cell monolayer is mediated by basic fibroblast growth factor and collagen

Human fetal skin fibroblasts (TIG-3S) were found to migrate into a denuded area in a cell monolayer when cultured in both serum-depleted and serum-supplemented media, unlike adult-donor skin fibroblasts which migrated well only when cultured in serum-supplemented medium. Therefore, a series of experiments was carried out to determine whether autocrine factors are involved in their migration. The migration of TIG-3S cells in serum-depleted medium was suppressed by the addition of suramin, a factor with growth factor antagonist properties, which suggests that growth factors are important for cell migration. The suramin-induced inhibition was reversed completely by adding excess basic fibroblast growth factor (bFGF) to the culture medium and partially by platelet-derived growth factor (PDGF). Treatment with neutralizing anti-PDGF antibody did not suppress TIG-3S cell migration, whereas neutralizing anti-bFGF antibody did, which indicates that bFGF is an autocrine and PDGF a paracrine factor involved in cell migration. Next, an experiment was performed to ascertain whether the extracellular matrix is involved in TIG-3S cell migration. Monensin, an inhibitor of extracellular matrix secretion, inhibited cell migration, which was reversed by adding excess type I collagen, but not excess plasma fibronectin. In addition, further evidence for the involvement of collagen was provided by the observation that ethyl-3,4-dihydroxybenzoate, a specific inhibitor of collagen synthesis, suppressed cell migration. These results suggest that the autonomous migration of TIG-3S human fetal skin fibroblasts is mediated by bFGF and type I collagen, which they produce and secrete.

Age-related changes in the mitogenic activity of heparin-binding growth factors in rat sera

Sera from rats of either sex and different ages were examined for their ability to stimulate DNA synthesis in BALB/c 3T3 cells. The activity levels of sera from male and female rats were almost the same, with age-related changes in activity also being quite similar. Activity was considerably higher in infant rats (1-month-old), but then, at a young age (6-7 months), decreased drastically for male rats, but not significantly for female rats. It increased again in middle-aged rats (12-13 months old) and was maintained at the same level toward old age (24-26 months old) for both sexes. In order to determine what kinds of growth factors were responsible for these changes, we carried out heparin affinity chromatography on the sera of male rats. Four peaks were obtained for all sera, with individual peaks exhibiting specific age-related changes in activity. Among them a peak which was eluted at 1.1 M NaCl had very high activity. It showed a similar age-related change to that of the whole sera, except for a significant increase at old age, and the factor(s) included in the peak was found to be derived from platelets. These results suggested that the factor(s) in the peak was responsible for maintaining serum mitogenic activity at an old age. The experiments undertaken to characterize this factor suggested that it is a novel one.

Changes in the migratory ability of human lung and skin fibroblasts during in vitro aging and in vivo cellular senescence

The migration of human lung and skin fibroblasts was determined during in vitro aging and in vivo cellular senescence by measuring their migration from the edge of a denuded area of a monolayer. The migration of human fetal lung fibroblasts (TIG-1 and TIG-3) decreased only very slightly with increasing passage, whereas the migration of human fetal skin fibroblasts (TIG-3S) declined gradually: the difference in cell migratory ability between early and late passages was significant (P less than 0.05). The migratory patterns of skin fibroblasts from adult and elderly donors were also similar to that of fetal skin fibroblasts. Next, the migratory abilities of fibroblast lines from adult and elderly donor groups were compared, using relatively early passaged cells. The migratory ability of the elderly-donor skin fibroblast lines was significantly lower (P less than 0.05) than that of the adult-donor skin fibroblast lines. Addition of suramin and monensin suppressed the migration of fibroblasts from fetal, adult and elderly donors, which implies that fibroblast migration is regulated by growth factors and matrix substances. The relationships between the age-dependent decline of migratory ability, growth factors and the extracellular matrix are discussed.

Species-specific differences in the mitogenic activity of heparin-binding growth factors in the sera of various mammals

Sera from different mammalian species displayed great differences in mitogenic activity, as measured by stimulation of DNA synthesis in BALB/c 3T3 cells (3T3 cells). Among the sera examined, fetal bovine serum was least active, and increasing activity was detected in calf serum, human serum, rat serum and mouse serum, in that order. Rat and mouse sera exhibited extremely high mitogenic activity with 3T3 cells, but when TIG-1 human fetal lung fibroblasts were used for the DNA assay instead, the activity levels of all of the sera were lower, and the differences between them were smaller. To determine the reasons for these differences, the heparin-binding growth factors in each serum were separated on a heparin affinity column. Five peaks of DNA-stimulating activity were obtained. Three of these were found in all sera examined, with both 3T3 cells and TIG-1 cells. Two other peaks were found only with 3T3 cells; one was peculiar to rat and mouse sera, with extremely high activity in the rat, and the other was specific to fetal serum. The dependence of the activity of these peaks on the cells used for the test was confirmed using normal rat lung fibroblasts and immortalized rat kidney cells. These findings adequately explain the species-specific differences in mitogenic activity of whole sera, and the variation in activity depending on the cells used for assay of DNA synthesis.

Effects of serum from human subjects of different ages on migration in vitro of human fibroblasts

A study was carried out to determine whether human serum from older subjects inhibited cell migration. Sera of both sexes from subjects in their 60s (60-64 years) tended to be more inhibitory (8-14%) to the migration of human fetal lung fibroblasts, TIG-1, than serum from subjects in their 20s (20-29 years). In the case of females, the effects of serum on cell migration were significantly (P less than 0.05) different between the younger and older groups. Next, cell migration-stimulatory activity of serum was measured using human skin fibroblasts from young adult (age 21) and elderly (age 65) donors. The results were similar to those obtained with TIG-1 cells. However, the cell migration-stimulatory activity of serum was not significantly different between the two age groups. A study on the effects of concentration of human serum on the migration of TIG-1 cells showed that cell migration-stimulatory activity of serum declined linearly with increasing concentrations of sera from subjects in their teens (16-19 years) and 50s (50-59 years), and was the same between the two age groups. These results imply that substance(s) inhibitory to cell migration may not have accumulated in serum during the ageing process in humans, although human serum contained substance(s) inhibitory to cell migration.