Effects of various steroids on in vitro lifespan and cell growth of human fetal lung fibroblasts (WI-38)

Sex steroid signaling: implications for lung diseases

There is increasing recognition that sex hormones (estrogen, progesterone, and testosterone) have biological and pathophysiological actions in peripheral, non-reproductive organs, including the lung. Clinically, sex differences in the incidence, morbidity and mortality of lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, lung cancer and pulmonary hypertension have been noted, although intrinsic sex differences vs. the roles of sex steroids are still not well-understood. Accordingly, it becomes important to ask the following questions: 1) Which sex steroids are involved? 2) How do they affect different components of the lung under normal circumstances? 3) How does sex steroid signaling change in or contribute to lung disease, and in this regard, are sex steroids detrimental or beneficial? As our understanding of sex steroid signaling in the lung improves, it is important to consider whether such information can be used to develop new therapeutic strategies to target lung diseases, perhaps in both sexes or in a sex-specific manner. In this review, we focus on the basics of sex steroid signaling, and the current state of knowledge regarding how they influence structure and function of specific lung components across the life span and in the context of some important lung diseases. We then summarize the potential for sex steroids as useful biomarkers and therapeutic targets in these lung diseases as a basis for future translational research in the area of gender and individualized medicine.

Metabolic changes during cellular senescence investigated by proton NMR-spectroscopy

Cellular senescence is of growing interest due to its role in tumour suppression and its contribution to organismic ageing. This cellular state can be reached by replicative loss of telomeres or certain stresses in cell culture and is characterized by the termination of cell division; however, the cells remain metabolically active. To identify metabolites that are characteristic for senescent cells, extracts of human embryonic lung fibroblast (WI-38 cell line) have been investigated with NMR spectroscopy. Three different types of senescence have been characterized: replicative senescence, DNA damage-induced senescence (etoposide treatment) and oncogene-induced senescence (hyperactive RAF kinase). The metabolite pattern allows (I) discrimination of senescent and control cells and (II) discrimination of the three senescence types. Senescent cells show an increased ratio of glycerophosphocholine to phosphocholine independent from the type of senescence. The increase in glycerophosphocholine implicates a key role of phospholipid metabolism in cellular senescence. The observed changes in the choline metabolism are diametrically opposite to the well-known changes in choline metabolism of tumour cells. As tumours responding to chemotherapeutic agents show a "glycerophosphocholine-to-phosphocholine switch" i.e. an increase in glycerophosphocholine, our metabolic data suggests that these malignant cells enter a senescent state emphasizing the role of senescence in tumour suppression.

Estrogens and development of pulmonary hypertension: interaction of estradiol metabolism and pulmonary vascular disease

Severe pulmonary arterial hypertension (PAH) is characterized by clustered proliferation of endothelial cells (ECs) in the lumina of small size pulmonary arteries resulting in concentric obliteration of the lumina and formation of complex vascular structures known as plexiform lesions. This debilitating disease occurs more frequently in women, yet both animal studies in classical models of PAH and limited clinical data suggest protective effects of estrogens: the estrogen paradox in pulmonary hypertension. Little is known about the role of estrogens in PAH, but one line of evidence strongly suggests that the vascular protective effects of 17β-estradiol (estradiol; E2) are mediated largely by its downstream metabolites. Estradiol is metabolized to 2-hydroxyestradiol (2HE) by CYP1A1/CYP1B1, and 2HE is converted to 2-methoxyestradiol (2ME) by catechol-O-methyl transferase. 2ME is extensively metabolized to 2-methoxyestrone, a metabolite that lacks biologic activity, but which may be converted back to 2ME. 2ME has no estrogenic activity, and its effects are mediated by estrogen receptors–independent mechanism(s). Notably, in systemic and pulmonary vascular ECs, smooth muscle cells, and fibroblasts, 2ME exerts stronger antimitotic effects than E2 itself. E2 and 2ME, despite having similar effects on other cardiovascular cells, have opposing effects on ECs; that is, in ECs, E2 is promitogenic, proangiogenic, and antiapoptotic, whereas 2ME is antimitogenic, antiangiogenic, and proapoptotic. This may have significant ramifications in severe PAH that involves uncontrolled proliferation of monoclonal apoptosis-resistant ECs. Based on its cellular effects, 2ME should be expected to attenuate the progression of disease and provide protection in severe PAH. In contrast, E2, due to its mitogenic, angiogenic, and antiapoptotic effects (otherwise desirable in normal quiescent ECs), may even adversely affect endothelial remodeling in PAH, and this may be even more significant if the E2's effects on injured endothelium are not opposed by 2ME (eg, in the event of reduced E2 conversion to 2ME due to hypoxia, inflammation, drugs, environmental factors, or genetic polymorphism of metabolizing enzymes). This review focuses on the effects of estrogens and their metabolites on pulmonary vascular pathobiology and the development of experimental PAH and offers potential explanation for the estrogen paradox in PAH. Furthermore, we propose that unbalanced estradiol metabolism may lead to the development of PAH. Recent animal data and studies in patients with PAH support this concept.

2-methoxyestradiol attenuates bleomycin-induced pulmonary hypertension and fibrosis in estrogen-deficient rats

Pulmonary hypertension (PH) is a common and life-threatening complication of pulmonary fibrosis. Estradiol (E2) is protective in experimental PH, and its non-estrogenic metabolite 2-methoxyestradiol (2ME) prevents the development and retards the progression of monocrotaline-induced PH in male and female rats. However, the effects of E2 and 2ME on pulmonary fibrosis and associated PH have not been examined. Therefore, we compared the growth inhibitory effects of E2 and 2ME in human lung fibroblasts (hLFs) and pulmonary vascular smooth muscle cells (hPASMCs), and we investigated the effects of estrogen deficiency and 2ME on bleomycin-induced pulmonary fibrosis and PH. Intact and ovariectomized (OVX) female Sprague-Dawley rats were administered intratracheally either saline or bleomycin (15IU/kg), and a subset of OVX bleomycin-treated rats received 2ME (10microg/kg/h) for 21days. Estradiol had only limited inhibitory effects on growth in hPASMCs and no effect in hLFs, whereas 2ME exhibited strong and concentration-dependent (1-10microM) antimitogenic effects in both cell types. Bleomycin caused lung injury/PH (significantly increased lung and right ventricle (RV) weights, RV peak systolic pressure (RVPSP), and RV/left ventricle + septum ratio (RV/LV + S); caused medial hypertrophy and adventitial widening of pulmonary arteries; induced marked focal/diffuse fibrosis with diffuse infiltration of inflammatory (ED1+) cells; and resulted in 30% mortality). OVX exacerbated the disease and increased mortality (to 75%); whereas 2ME tended to reduce mortality (55.5%) and in surviving animals reduced RVPSP and RV/LV + S ratio, and attenuated vascular remodeling, pulmonary inflammation and fibrosis. This study suggests that 2ME may have protective effects in bleomycin-induced PH and fibrosis. Further investigation of 2ME in pulmonary fibrosis and PH is warranted.

The impact of chronic in vivo glucocorticoid excess on the functional characteristics of human skin fibroblasts obtained from patients with endogenous Cushing's syndrome

OBJECTIVE

Chronic exposure to elevated glucocorticoid (GC) concentrations induces detrimental effects in several tissues. In the skin, GCs provoke intense alterations on various parameters of the physiology of fibroblasts, cumulatively leading to skin atrophy and impaired wound healing. As there are concerns that GCs may generate permanent adverse functional changes, we have investigated whether chronic in vivo exposure to GC excess results in persisting defects in skin fibroblasts.

DESIGN AND METHODS

We have studied in vitro primary skin fibroblast cultures obtained from patients suffering from endogenous Cushing's syndrome (CF), as well as from sex- and age-matched normal donors (NF). The following functional parameters were investigated: cell proliferation, secretion of collagen, matrix metalloproteinases (MMPs) and their inhibitors (tissue inhibitors of metalloproteinases; TIMPs) and contractile capacity.

RESULTS

CFs, grown under standard culture conditions in the absence of a hypercortisolemic milieu, exhibited an increased proliferative capacity and a higher final cell culture density compared with NFs. Collagen synthesis, in the absence or presence of transforming growth factor-beta, was equal to that of NFs. However, CFs secreted comparatively lower levels of MMP-1, MMP-2 and TIMP-1, and nearly equal levels of TIMP-2. CFs also exhibited an increased ability to contract gels of polymerized collagen.

CONCLUSIONS

Collectively, these functional characteristics of CFs are in contrast to the known catabolic effects of GCs, and suggest that prior exposure to GC excess is not associated with a persisting adverse outcome in the functional phenotype of the fibroblasts.

Comparison of Colony-Formation Efficiency of Bovine Fetal Fibroblast Cell Lines Cultured with Low Oxygen, Hydrocortisone, L-Carnosine, bFGF, or Different Levels of FBS

A comparison of colony-formation efficiency (CFE) was made between six independent bovine fetal fibroblast (BFF) cell lines used in somatic cell nuclear transfer. Variation in CFE was assessed under different culture conditions. The conditions examined were ambient atmosphere (approximately 20% oxygen) culture versus 5% oxygen culture, three levels of fetal bovine serum (FBS) in the medium (5%, 10% or 20%), and the amendment of 10% FBS medium with basic fibroblast growth factor (1 ng/mL), L-carnosine (20 mM), or hydrocortisone (1 microM). The six BFF cell lines showed significant differences from one another in CFE. No significant difference in CFE was found with reduced oxygen culture. L-Carnosine also had no significant effect on CFE. A FBS concentration of 10% was found to produce the best overall CFE. Hydrocortisone treatment reduced the size of colonies although the number of colonies formed was not affected. Basic FGF increased the size of colonies but the number of colonies formed was not affected. The results showed that different BFF cell lines varied significantly in their CFE. Also, some medium supplements or culture conditions that have shown positive CFE effects on the fibroblasts of other species failed to show significant positive CFE effects on the BFF cell lines tested.

Effect of polyelectrolyte complex (PEC) on human periodontal ligament fibroblast (HPLF) functions in the presence of glucocorticoids

Cell functions in vivo are stimulated by extracellular matrices, vitamins, growth factors, and hormones. In this paper, the effects of glucocorticoids, dexamethasone (Dex), and Cortexrone (Cor) on the growth and differentiation of human periodontal ligament fibroblast (HPLF) were discussed in relation to a polyelectrolyte complex (PEC) consisting of polysaccharides (chitin, cellulose derivatives, and chitosan) as a tissue-culture material. A Dex-treatment at a concentration of 10(-)-10(-7) M inhibited one-half of HPLF growth in comparison with 10(-9) M Dex-treatment and no additive medium and produced aggregates on the chitosan-sulfated chitin PEC (SPECs) with regard to the degree of sulfate substitution. On the chitosan-sulfated cellulose PEC, 10(-7)-10(-9) M Dex-treatment promoted HPLF growth and inhibited the production of aggregates. On the other hand, a Cor-treatment, a mineral corticoid, which inhibits the interaction between Dex and its receptor, increased HPLF growth on SPEC141, but the HPLF did not construct aggregates. A Dex and Cor mixture-treatment inhibited one-third HPLF growth in comparison with 10(-5) M Dex-treatment and produced aggregates on PEC. The cooperative effect of both the culture material and hormones was found to control HPLF growth and morphology. The alkaline phosphatase (ALPase) activities of HPLF increased with an increase in the Dex and Cor concentration. The value of Dex-treated HPLF ALPase activity demonstrated a two-fold increase from that with Cor-treatment. The ALPase activity of Dex and Cor mixture-treated HPLF on PEC decreased with an increase in the Cor concentration, because Cor increased HPLF growth on PEC. In using carboxymethylated chitin derivatives as the polyanion, HPLF decreased in cell growth and produced aggregates in the absence of the additives, suggesting that PEC induces HPLF differentiation using only the stimulation of the material surface.

Chromosomal analysis in young vs. senescent human fibroblasts by fluorescence in situ hybridization: a selection hypothesis

Almost all previous studies on chromosomal analysis related to in vitro aging of human fibroblasts were done using only metaphase chromosomes. However, this procedure may provide only partial information since the aneuploidy presumably hidden in interphase cells would remain undetected. For this reason, we have analyzed aneuploidy both at interphase and at metaphase. Female (IMR-90) and male (IMR-91) cells were grown from the lowest to the highest population doubling levels and aneuploidy analysis was done by FISH with alpha-satellite DNA probes of 15 autosomes and two sex chromosomes. Our data on total aneuploidy in young cells indicate that significantly higher proportions of cells with aneuploidy can be detected at interphase than at metaphase. This presumably indicates that during active division of young cells, more aneuploid than diploid cells are selected against entry to mitosis. In contrast, interphase senescent cells from both strains show significantly fewer aneuploid nuclei than do young cells at interphase. This probably indicates that during senescence, there is greater selective pressure in the culture against long-term survival of aneuploid cells than against survival of diploid cells. Our study shows that cellular dynamics with respect to aneuploidy involving various chromosomes differs significantly at interphase and at mitosis during in vitro aging of human fibroblasts, and we propose a 'Selection Hypothesis' as an explanation to our findings.

Platelet-derived growth factor in combination with collagen promotes the migration of human skin fibroblasts into a denuded area of a cell monolayer

Since we have found previously that adult donor skin fibroblasts (TIG-114) migrated more slowly in serum-depleted medium than in medium supplemented with 10% FBS, we tried to identify a factor(s) which promotes fibroblast migration from the edge of a denuded area in a monolayer. In medium supplemented with 10% FBS, the effects of both suramin, a competitor of growth factors at the receptor level, and monensin, an inhibitor of the secretion of extracellular matrix, were examined. Both substances suppressed cell migration, suggesting that growth factors and matrix substances are important for cell migration. Then, we examined the effects of growth factors and extracellular matrix on fibroblast migration in serum-free medium. Platelet-derived growth factor (PDGF), basic fibroblast growth factor, acidic fibroblast growth factor, and transforming growth factor-beta did not stimulate cell migration. Type I collagen, plasma fibronectin, and heparin also did not promote cell migration. However, the combination of PDGF and type I collagen did promote cell migration. Addition of anti-PDGF antibody reduced the stimulatory effect induced by the combination of PDGF and type I collagen. These results suggest that the copresence of growth factors and extracellular matrix regulates fibroblast migration into a denuded area in a monolayer.

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.

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.

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

We carried out a study to determine whether serum from old human subjects inhibited cell proliferation. The results showed that serum from old subjects of either sex did not greatly inhibit the proliferation of human fetal lung fibroblast TIG-1 cells, even when serum from subjects in their 80s was used. The same results were obtained when the effects of serum on cell proliferation were examined up to a serum concentration of 50%. It was also found that serum from old subjects did not inhibit proliferation of human skin fibroblasts from a young adult to any greater degree than serum from young adult subjects, and that serum from young adult subjects did not stimulate proliferation of skin fibroblasts from an elderly donor to any greater degree than serum from old subjects.

Culture media variation as related to in vitro aging of human fibroblasts: II. Effects on nucleolar number/cell, volume/nucleolus and total nucleolar volume/cell

The relative effect of five commonly used culture media (MEM, BME, McCoy's 5A, M199 and HMEM) on the average nucleolar number/cell, the average volume/nucleolus and the total nucleolar volume/cell was examined during in vitro senescence of WI-38 human fetal fibroblasts. Statistical analyses show that cells aging in MEM show a higher number of nucleoli/cell than that of cells aging in any other medium. For cells aging in the other four media, there are no significant differences in the average number of nucleoli/cell. Linear regression analysis shows that in all cases there is a linear decrease in the average number of nucleoli/cell as a function of PDL. Statistical analyses show that the average volume/nucleolus is significantly greater for cells aging in M199 than in any other medium. Cells aging in HMEM show smaller average nucleolar volume than cells aging in M199, but display larger volumes than that of cells aged in BME, McCoy's 5A, or MEM. Cells aging in BME and McCoy's 5A media show no significant difference among each other in terms of average nucleolar volume, but a difference in this parameter is noted in cells aging in BME and MEM. A linear regression analysis shows that the average volume/nucleolus increases linearly as a function of age for cells grown in all five media. Analysis of the total nucleolar volume/cell in the five media shows that cells aging in M199 and HMEM are not significantly different from each other in terms of this variable, but show significantly larger volumes than those of cells aging in BME, McCoy's 5A and MEM. Cells aging in BME, McCoy's 5A and MEM display no significant difference with regard to this parameter. Linear regression analysis shows a positive linear relationship between the PDL and the total nucleolar volume/cell. The relative effects of all five media are not the same on the three cellular variables studied during in vitro aging of WI-38 cells. We, therefore, suggest that one should note this medium differential in order to allow meaningful comparison of results on possible changes in various morphological parameters during in vitro senescence of diploid human fibroblasts.

Effects of serum collected from rats of different ages on in vitro cell proliferation

It has been reported by Carrel and his co-workers that serum from old hens inhibits cell growth in culture. However, as we had previously demonstrated contradictory results using serum from old rabbits, we examined whether serum from old rats would also show strong induction of cell proliferation. Sera from young and adult rats of either sex strongly stimulated the growth of rat fetal skin fibroblasts and human fetal lung fibroblasts (TIG-1). Sera of old female and male rats (24-29 months old) produced much greater fluctuations in growth-stimulatory activity than sera from young animals. Most samples of serum from old rats stimulated the growth of TIG-1 cells, as did fetal bovine serum and samples from younger rats, even when a higher concentration of serum (up to 50%) was used. On the other hand, a small proportion of samples repressed the growth of the cells. A study on the effects of serial mixtures of both different types of serum samples from old rats on cell growth suggested that this minor proportion of serum samples contain a large amount of inhibitory factor(s). The cell growth-stimulatory activity of serum did not correlate with the total protein and albumin concentrations, albumin/globulin ratio, and the levels of lipid peroxide in the sample. These results therefore seemed to imply that serum induced a striking increase in the heterogeneity of cell growth stimulatory activity with age, although most samples of serum from old rats of either sex stimulated cell proliferation as effectively as samples from younger rats. The biological significance of the small proportion of serum samples from old rats which do inhibit cell proliferation was discussed.

Hydrocortisone stimulation of proliferation and glycosaminoglycan synthesis in rabbit craniofacial chondrocytes in vitro

Hydrocortisone stimulated glycosaminoglycan (GAG) synthesis, a cartilage phenotype, in chondrocytes from mandibular condylar cartilage (MCC), nasal septal cartilage (NSC) and sphenooccipital synchondrosis (SOS). These stimulations were dose- and time-dependent, being maximal 27 h after addition of 10(-7) M hydrocortisone. The maximal induced increase of GAG synthesis was about 100%, 50% and 20% that of non-stimulated MCC, SOS and NSC chondrocytes, respectively. When stained with toluidine blue, all three types of cortisone-treated chondrocytes showed stronger metachromasia than non-treated controls. DNA synthesis was also increased by hydrocortisone, reaching a maximum 20 h after the addition; stimulation was also dose-dependent and maximal at a concentration of 10(-6) M. The maximal increase in DNA synthesis was 200% in NSC chondrocytes, 90% in SOS chondrocytes, and slight in MCC chondrocytes. However, there was no stimulation of DNA synthesis in serum-free medium, in contrast to that of GAG synthesis. These observations suggest that hydrocortisone regulates craniofacial growth by controlling the differentiation of these chondrocytes directly and their proliferation indirectly, and that the difference in their responses to hydrocortisone may reflect different responses in vivo.

Cellular senescence revisited: a review

The field of cellular senescence (cytogerontology) is reviewed. The historical precedence for investigation in this field is summarized, and placed in the context of more recent studies of the regulation of cellular proliferation and differentiation. The now-classical embryonic lung fibroblast model is compared to models utilizing other cell types as well as cells from donors of different ages and phenotypes. Modulation of cellular senescence by growth factors, hormones, and genetic manipulation is contrasted, but newer studies in oncogene involvement are omitted. A current consensus would include the view that the life span of normal diploid cells in culture is limited, is under genetic control, and is capable of being modified. Finally, embryonic cells aging in vitro share certain characteristics with early passage cells derived from donors of increasing age.

Effects of dexamethasone on the growth of cultured rabbit articular chondrocytes:relation with the nuclear glucocorticoid-receptor complex

This study reports that dexamethasone at a high dose (10(-4) mol/l) induced slowing of the in vitro proliferation of rabbit articular chondrocytes in both monolayer and clonal culture. This effect is consistent with an inhibition of DNA and RNA synthesis and was characterised by an accumulation of cells in the G0G1 phase of the cell cycle, as shown by flow cytometric analysis. Therefore we determined the extent of nuclear localisation of dexamethasone-receptor complexes. The results showed a discrepancy between 50% growth inhibitory dose (10(-4) mol/l) and the apparent affinity, KD (1.4 (SD 0.2) X 10(-9) mol/l). Thus the growth inhibition of rabbit articular chondrocytes by dexamethasone did not seem to be related exclusively to an interaction with the glucocorticoid-receptor complexes.

Autocrine stimulation of WI38 cell proliferation in the presence of glucocorticoids. Characteristics of the stimulatory factor(s) involved in this response

Chronic exposure to hydrocortisone (HC) or dexamethasone (DEX) results in a 20-40% extension in the proliferative lifespan of WI38 cells. Within a single growth cycle, the addition of HC or DEX at seeding results in saturation densities 20-40% higher than in control cultures. We have recently reported that, within a single growth cycle, the proliferative response of WI38 cells to glucocorticoids is mediated by a stimulatory factor(s) present in medium conditioned by cells in the presence of the hormone. We report here that chronic exposure to medium conditioned in the presence of HC for the first 24 h after seeding (24-h HC-conditioned medium (24-h HC-CM)) results in a 25% extension in the proliferative lifespan of these cultures. The generation of the stimulatory factor(s) present in glucocorticoid-conditioned medium is apparently dependent upon undefined cellular alterations which result from the subcultivation-procedure; confluent or low-density quiescent cultures did not generate media stimulatory to cell growth in the presence of glucocorticoids. This response was not trypsin-dependent, since cultures subcultivated in the absence of proteolytic treatment generated media equally stimulatory to cell growth. A further characterization of this glucocorticoid-induced activity revealed the stimulatory factor(s) was of low MW (dialyzable and recoverable in the less than 10,000 MW fraction following ultrafiltration), heat-stable (95 degrees C), and resistant to treatment with trypsin, chymotrypsin, or protease (S. griseus).

Culture media variation as related to in vitro aging of human fibroblasts: I. Effects on population doubling, nuclear volume and nuclear morphology

The relative effect of five commonly used culture media (MEM, BME, McCoy's 5A, M199 and HMEM) on the population doubling level (PDL), nuclear volume and nuclear morphology was examined during in vitro senescence of WI-38 human fetal fibroblasts. Statistical analyses showed that cells grown in M199 had a significantly lower PDL than that of cells cultured in any other medium. The PDL in McCoy's 5A was significantly lower compared to that in BME, MEM and HMEM. Cells grown in BME, MEM and HMEM showed similar PDL. It was found that the nuclei of aged cells grown in M199 were significantly larger in volume than cells aged in any other medium. The average increases in nuclear volume of cells during aging in BME, MEM and McCoy's 5A were statistically equivalent. The increase in nuclear volume in HMEM was significantly smaller than that of cells aging in M199 and was longer than that of cells aging in BME or MEM. Linear regression analysis showed that there was a linear increase in nuclear volume as a function of PDL for cells aged in all five media. However, the rate of increase in nuclear volume with increasing PDL varied from medium to medium. There was no significant difference between media on induction of abnormal nuclear morphology as related to PDL. The relative effects of all five media were not uniform on the three cellular parameters investigated during in vitro aging of WI-38 cells. It is, therefore, suggested that one should keep this medium differential in mind to allow meaningful comparison of possible changes in various morphological parameters during in vitro senescence of diploid human fibroblasts such as WI-38.

Hormonal control of the replication of human fetal fibroblasts: role of somatomedin C/insulin-like growth factor I

Sparse cultures of fetal and postnatal human fibroblasts were equivalent in their responsiveness to the mitogenic action of somatomedin C/insulin-like growth factor I (SM-C/IGF-I). At both developmental stages, the addition of SM-C/IGF-I (100 ng/ml) increased cell number at day 3 1.4-fold in serum-free medium and 2-fold in the presence of 0.25% human hypopituitary serum. Furthermore, dose-response curves indicated that there was no difference in the sensitivity of fetal and postnatal fibroblasts to the growth-promoting effects of SM-C/IGF-I, with a half-maximal response occurring at 6 ng/ml SM-C/IGF-I. This biological action of SM-C/IGF-I correlated with SM-C/IGF-I binding to fetal and postnatal fibroblast monolayers. Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) also stimulated replication of fetal and postnatal fibroblasts. The mitogenic effects of SM-C/IGF-I, EGF, and PDGF were additive. Dexamethasone, which alone had no effect, was synergistic with SM-C/IGF-I in stimulating replication of postnatal fibroblasts. The combination of SM-C/IGF-I (100 ng/ml), dexamethasone (10(-7) M), EGF (10 ng/ml), and PDGF (5 ng/ml) had the same mitogenic effectiveness as 10% calf serum (CS) in postnatal cells. In marked contrast, there was no mitogenic interaction between SM-C/IGF-I and dexamethasone in fetal fibroblasts. In fetal cells, SM-C/IGF-I + EGF + PDGF +/- dexamethasone could only account for 50% of the activity of 10% CS. Moreover, fetal cells were 50-100% more responsive than postnatal cells to the proliferative effect of serum.

Neurotropin increases in vitro life span of human fibroblasts

Fibroblasts isolated from human fetal tissues (skin, lung and heart) exhibited the following population doubling levels (PDL): about 40 PDL for skin; 60 PDL for lung; 10 PDL for heart. Neurotropin extract from vaccinia-virus infected skin tissues of rabbits increases the growth rate of the fibroblast when added to the old lung cell culture (PDL 40, 70% of the maximum life span) but not when added to the young lung (PDL 5, 8% of the maximum life span). Neurotropin (40 or 80 micrograms/ml) increased the replicative life span of the three lines of fibroblasts (skin, lung and heart) when added to the young cell cultures. The increase of the maximum PDL of skin, lung and heart fibroblasts with the Neurotropin treatment was by 19%, 5% and 17%, respectively. When Neurotropin was added to the old lung cell culture (PDL 44, 73% of the maximum life span), the maximum PDL was increased by 9%. Since the existence of hydrocortisone, known to extend the in vitro life span, was negligible in the fluorimetric test of the medium containing Neurotropin, this agent may belong to the class other than hydrocortisone, for increasing in vitro life span.

Effects of serum from rabbits of various ages on cell proliferation

The report of Carrel and Ebeling (J. Exp. Med., 34 (1921) 599-623) generally gives the impression that both serum and blood plasma from old animals inhibit cell proliferation. For confirmation of this, we examined the effects of serum from rabbits of various ages on rabbit fetal skin fibroblasts (RSF cell) and human fetal lung fibroblasts (TIG-1 cell). Serum from young rabbits 8 months of age stimulated proliferation of RSF cells just as did fetal bovine serum, but that from old rabbits 5-7.8 years of age was found to significantly increase proliferation more than serum from the young. This was also the case when using TIG-1 cells. The lesser effect on cell proliferation by young serum apparently does not arise from growth-inhibitory factor(s) in the blood components. An examination showed young serum to possibly contain fewer growth-stimulatory factor(s) than old serum. On the basis of our data, we concluded that old rabbit serum stimulates, not inhibits, the proliferation of RSF and TIG-1 cells.

The heterogeneity of human fibroblasts as determined from the effects of hydrocortisone on cell growth and specific dexamethasone binding

To elucidate the heterogeneity of human fibroblasts from lung and skin, the effects of hydrocortisone on cell proliferation and the specific dexamethasone binding to cells were studied. Hydrocortisone at physiological concentrations stimulated the proliferation in three strains of human fetal lung fibroblasts and inhibited it in two strains. There are two kinds of fibroblasts in the human fetal lung in addition to the human skin fibroblasts reported previously. Dexamethasone-binding experiments showed that human fibroblasts may be classified into two groups with respect to the dissociation constant (Kd) of the binding reaction. The heterogeneity of human fibroblasts shown by Kd could not be correlated to classification on the basis of the effects of hydrocortisone on cell proliferation. The differences in Kd for the binding reactions suggest differences in donor tissues from which human fibroblasts are derived.