Tissue-specific differences in cultured human diploid fibroblasts

Some metabolic differences between human skin and aponeurosis fibroblasts in culture

Two types of human fibroblast strains were studied in culture. One was derived from abdomen skin and the other from abdominal muscle aponeurosis. Tissue-specific differences were found between these two cell strains. Skin fibroblasts had faster doubling time, smaller cell volume, and lower glucose consumption when compared to aponeurosis fibroblasts. Furthermore, extracellular amino acid variations showed some specific differences, in particular a lack of serine consumption in skin fibroblasts.

Recent advances in the cell biology of aging

Cultured normal human and animal cells are predestined to undergo irreversible functional decrements that mimic age changes in the whole organism. When normal human embryonic fibroblasts are cultured in vitro, 50 +/- 10 population doublings occur. This maximum potential is diminished in cells derived from older donors and appears to be inversely proportional to their age. The 50 population doubling limit can account for all cells produced during a lifetime. The limitation on doubling potential of cultured normal cells is also expressed in vivo when serial transplants are made. There may be a direct correlation between the mean maximum life spans of several species and the population doubling potential of their cultured cells. A plethora of functional decrements occurs in cultured normal cells as they approach their maximum division capability. Many of these decrements are similar to those occurring in intact animals as they age. We have concluded that these functional decrements expressed in vitro, rather than cessation of cell division, are the essential contributors to age changes in intact animals. Thus, the study of events leading to functional losses in cultured normal cells may provide useful insights into the biology of aging.

In utero analysis of sister chromatid exchange: alterations in suscptibility to mutagenic damage as a function of fetal cell type and gestational age

Frequencies of baseline and cyclophosphamide-induced sister chromatid exchanges (SCE) were measured in mouse maternal and fetal cells between days 11 and 19 of gestation. Baseline levels of SCE did not vary as a function of gestational age in either the mother or fetus. Cyclophosphamide-induced SCE frequencies remained constant in maternal cells but declined dramatically in the fetus throughout the latter half of development. Because cyclophosphamide is a metabolically activated mutagen, a direct-acting drug, mitomycin C, was given on days 11 and 15 to determine if the decline in induced SCE levels seen with gestational results from alterations in activating enzymes. A similar decline in mitomycin C-induced SCE levels was noted in fetal tissues as a function of gestational age. Dose-response curves to cyclophosphamide performed on day 13 of gestation showed increases in SCE as a function of cyclophosphamide concentration in both the mother and the fetus. When mutagen-induced SCE levels were compared in different fetal organs, the direct-acting drugs (mitomycin C and daunomycin) were found to induce similar levels in all tissues. Cyclophosphamide, which is metabolically activated, induced higher SCE levels in fetal liver than in lung or gut. Whereas cyclophosphamide induced similar SCE levels in fetal and maternal cells on day 13 of gestation, daunomycin produced fetal SCE levels that were approximately 50% of maternal levels. Simultaneous measurement of the distribution of [14C]cyclophosphamide and [3H]daunomycin in maternal and fetal cells revealed that the lower SCE induction by daunomycin was probably due to decreased ability to cross the placental barrier.

Cell-surface changes accompanying aging in human diploid fibroblasts: effects of tissue, donor age and genotype

The generality of age-related changes in concanavalin A (Con A)-mediated red blood cell (RBC) adsorption to human diploid fibroblasts was investigated on fibroblast-like cells from fetal lung, heart, liver, skin and muscle tissues. All the cells examined showed the continuous increase from early passages in RBC adsorption with the RBC coating method (in which Con A-coated RBCs are adsorbed to fibroblasts) and the incraease only at phase III with the fibroblast coating method (in which RBCs are adsorbed to Con A-coated fibroblasts). All of the four strains of lung fibroblasts gave nearly the same extent of the age-related change in RBC adsorption, when expressed as a function of percentage life span consumed, indicating that the change in RBC adsorption is independent of genetic heterogeneity and conditions of primary culture. Liver and heart fibroblasts also gave results similar to those of lung fibroblasts. However, skin and muscle fibroblasts were lower in their RBC adsorption capacity throughout the life span. The continuous age-related increase in RBC adsorption to these cells could be sensitized by using glutaraldehyde-prefixed RBCs, trypsinized RBCs or phytohemagglutinin P in place of Con A. The relevance of the phenotype of in vitro aging revealed by RBC adsorption to in vivo aging was also demonstrated on skin fibroblasts from different ages of donors using glutaraldehyde-prefixed RBCs. In addition, fibroblasts from patients with Werner's syndrome, an hereditary disease manifested by early and widespread degenerative changes, showed senescent phenotype in RBC adsorption even at early passages.

Clonal growth of human keratinocytes with small amounts of dialyzed serum

A survey of commercially available media revealed that medium F-12 was superior to medium 199 for clonal growth of human epidermal keratinocytes (HK) when supplemented with 10 micrograms/ml hydrocortisone (HC) plus dialyzed fetal bovine serum protein (FBSP), rather than the whole serum used in previous studies. Qualitative and quantitative adjustment of the medium composition for optimal clonal growth with minimal amounts of FBSP generated a new medium, MCDB 151, which supports clonal growth of HK with 10 micrograms/ml HC and as little as 1 mg/ml FBSP (equivalent in protein concentration to 2.0% whole serum). MCDB 151 differs significantly from NCDB 105, previously developed in this laboratory for normal human fibroblasts, and each medium selectively favors growth of its own type of cell in primary cultures of disaggregated human neonatal foreskin cells. Differences in the amounts of calcium and adenine in the two media appear to be among the most influential factors mediating the selective growth. Optimal growth of HK occurs at a very low level of Ca2+ that causes the colonies to remain as monolayers rather than stratifying as they do in the presence of higher levels of calcium. However, keratin synthesis, which was examined through use of highly specific fluorescent antibodies, is not affected by the Ca2+ concentration. Agents that increase intracellular cyclic AMP levels appear to have no effect on HK growth in MCDF 151 with 10 micrograms/ml HC and 1.0 mg/ml FBSP.

Effects of glucocorticosteroids on cultured human skin fibroblasts. III. Transient inhibition of cell proliferation in the early growth stages and reduced susceptibility in later growth stages

An immediate depression of the rate of cell proliferation occurred upon addition of glucocorticosteroids to cultures of human skin fibroblasts in the early growth stages. A reduced sensitivity or even insensitivity of the fibroblasts to growth inhibition inhibition was found upon the addition of the steroids at later stages of cell growth, when the cell density has increased. The inhibition in the early growth stages is transient and is most pronounced if the cultured medium is not renewed. This transient inhibition is not due to the development of steroid-resistant cell lines, and resembles the effect called tachyphylaxis, as is also observed in vasoconstriction tests.

Effect of SiO2-liberated macrophage factor on protein synthesis in connective tissue in vitro

1. To elucidate the role of macrophages in fibrosis the effect of the SiO2-liberated macrophage factor was assessed on protein synthesis in granulation-tissue slices. SiO2 could be replaced by chrysotile asbestos. The active factor is found in the 45/55% sucrose interface of macrophage homogenate. 2. There is no evidence of the involvement of collagenase. 3. The SiO2 effect is not influenced by the addition of yeast RNA to the incubation medium. 4. At a small concentration of polyvinylpyridine-N-oxide (PVNO) protein synthesis in the granulation tissue slices is stimulated, but at higher concentrations PVNO prevented the liberation of the fibrogenic factor from macrophages by SiO2. 5. Phospholipase C and trypsin inhibited the effect of SiO2, which was partially abolished also by heating, and by repeated freezing and thawing. 6. The macrophage RNAse, its inhibitors and fibroblast mRNA are suggested as key factors in the development of fibrosis.

The effect of donor age on the in vitro life span of cultured human arterial smooth-muscle cells

The number of population doublings of cultured human arterial smooth-muscle cells decreased as a function of donor age (0.5 to 82 years). Cells from older donors also showed longer latent periods for outgrowth from explants. These results extend other comparable observations with human skin fibroblasts to another cell type, and may have relevance to the pathogenesis of atherosclerosis with aging in vivo.

Differential effects of hydrocortisone on both growth and collagen metabolism of human fibroblasts from normal and keloid tissue

Cultured fibroblasts isolated from normal and keloid tissue do not differ in their growth characteristics or in the rate of collagen synthesis under routine culture conditions. The addition of hydrocortisone to the culture media results in significant differences in both growth and collagen synthesis between these cell types. Collagen synthesis is inhibited 60% in normal cultures by hydrocortisone (0,5 micrograms/ml) and the population size at which density-dependent growth inhibition is achieved is increased. Keloid-derived fibroblasts grow to a lower maximum density in the presence of hydrocortisone, while their rate of collagen synthesis is not significantly reduced. The rate of non-collagen protein synthesis is increased significantly by hydrocortisone in both cell types. Comparison of normal and keloid-derived cultures obtained from a single individual suggests that the keloid phenotype with respect to both growth and collagen synthesis is restricted to the fibroblasts isolated from the keloid nodule.