The Skin, Dermis, Fibroblasts and Aging

Furth JJ. (1991) The steady-state levels of type I collagen mRNA are reduced in senescent fibroblasts., J Gerontol May; 46(3):B122-4

Abstract:

The decreased collagen content in aging skin could be a consequence of decreased synthesis or increased degradation. The possibility that decreased synthesis of collagen results from decreased synthesis of mRNAs for Type I collagen, the major collagen in skin, was investigated by assessing the steady-state levels of alpha 1(I) and alpha 2(I) collagen mRNAs in actively proliferating and senescent WI-38 fibroblasts. The levels of both alpha 1(I) mRNA and alpha 2(I) mRNA were significantly lower in senescent fibroblasts, suggesting that one factor contributing to the decreased collagen content of aging skin may be decreased synthesis of these collagen mRNAs by senescent fibroblasts. Both mRNAs were reduced to the same extent, suggesting that coordinate regulation of the two Type I collagen genes is maintained in senescent fibroblasts.

West MD. (1994) The cellular and molecular biology of skin aging., Arch Dermatol; 130(1):87-95

Abstract:

The dramatic alterations in the appearance of the integument with increasing age are due in part to a progressive destruction of the delicate architecture of the connective tissue components of the dermis. Both collagenous and elastic components display a degeneration consistent with the overexpression of proteolytic activity. Recent advances in the field of molecular gerontology, using in vitro models of cellular aging, are yielding clues as to the fundamental causes of dermal aging.

OBSERVATIONS: Dermal fibroblasts possess a finite replicative capacity of 50 to 100 doublings, then cease replicating in response to growth factors. Cells cultivated to the end of their replicative lifespan in vitro display alterations consistent with their playing a role in aging in vivo. In particular, senescent dermal fibroblasts overexpress metalloproteinase activities that may explain the age-related atrophy of extracellular matrix architecture.

CONCLUSIONS: The recent discovery of a structural change in the telomeric region of the genome with cellular aging and new insights into DNA damage checkpoint mechanisms offer new opportunities to uncover both the molecular mechanisms regulating cellular aging and possibly to devise new strategies to manipulate these molecular events for therapeutic effect.

Reed MJ; Vernon RB; Abrass IB; Sage EH. (1994) TGF-beta 1 induces the expression of type I collagen and SPARC, and enhances contraction of collagen gels, by fibroblasts from young and aged donors., J Cell Physiol; 158(1):169-79

Abstract:

Fibroblasts have a major role in the synthesis and reorganization of extracellular matrix that occur during wound repair. An impaired biosynthetic or functional response of these cells to stimulation by growth factors might contribute to the delayed wound healing noted in aging. We, therefore, compared the responses of dermal fibroblasts from young and elderly individuals (26, 29, 65, 89, 90, and 92 years of age) to transforming growth factor-beta 1 (TGF-beta 1) with respect to: (1) the synthesis of type I collagen and SPARC (two extracellular matrix proteins that are highly expressed by dermal fibroblasts during the remodeling phase of wound repair) and (2) the contraction of collagen gels, and in vitro assay of wound contraction. With the exception of one young donor, all cultures exposed for 44 hours to 10 ng/ml TGF-beta 1 exhibited a 1.6- to 5.5-fold increase in the levels of secreted type I collagen and SPARC, relative to untreated cultures, and exhibited a 2.0- to 6.2-fold increase in the amounts of the corresponding mRNAs. Moreover, the dose-response to TGF-beta 1 (0.1-10 ng/ml), as determined by synthesis of type I collagen and SPARC mRNA, was as vigorous in cells from aged donors as in cells from a young donor. In assays of collagen gel contraction, fibroblasts from all donors were stimulated to a similar degree by 10 ng/ml TGF-beta 1. In conclusion, cells from both young and aged donors exhibited similar biosynthetic and contractile properties with exposure to TGF-beta 1. It therefore appears that the impaired wound healing noted in the aged does not result from a failure of their dermal fibroblasts to respond to this cytokine.

Dumas M; Chaudagne C; Bonte F; Meybeck A. (1994) In vitro biosynthesis of type I and III collagens by human dermal fibroblasts from donors of increasing age., Mech Ageing Dev; 73(3):179-87

Abstract:

A quantitative study of type I and type III collagen production was carried out on primary cultures of human dermal fibroblasts. Cultures were initiated from facial and mammary skin of 29 women aged between 19 and 68 years. Secreted and cell-associated collagen levels were determined by an enzyme linked immunosorbent assay (ELISA). We found that the secretion of type I and type III collagen decreased linearly with age (r = 0.432; P = 0.0193 and r = 0.502; P = 0.0147, respectively). There was a 29% loss in secretion ability for type I and type III collagen over the 49-year period studied. Furthermore, no significant linear age-related decrease was observed for type I and type III collagen associated with the cellular fraction. The influence of body site was also analysed. We observed a significant linear age-related decrease in type I collagen secretion by mammary skin cells (P = 0.0183 and r = 0.618) as well as facial skin cells (P = 0.0037 and r = 0.699). Furthermore, only mammary skin fibroblasts showed a significant linear age-related decrease in secreted type III collagen (P = 0.106 and r = 0.513). No age-related variations in cell-associated collagen were found.

Brinckmann J; Bodo M; Brey M; Wolff HH; Muller PK. (1994) Analysis of the age-related composition of human skin collagen and collagens synthesized by fibroblast culture., Arch Dermatol Res; 286(7):391-5

Abstract:

Age-related differences in the composition and the post-translational modifications of human skin collagens were examined in the present study. The data were compared with results of collagen synthesis from in vivo-aged fibroblasts in culture. Skin extracts and newly synthesized collagen from fibroblast cultures derived from both old and young donor groups showed the same ratio of collagen III to collagen I. Furthermore, no difference was noted in the degree of prolyl and lysyl hydroxylation of collagen I and collagen III Young and old fibroblasts synthesized a similar quantity of collagen in vitro. The data suggest that fibroblasts maintain a uniform level of collagen production, composition and modification independent of the age of the donor.

Freedland M; Karmiol S; Rodriguez J; Normolle D; Smith D Jr; Garner W. (1995) Fibroblast responses to cytokines are maintained during aging., Ann Plast Surg; 35(3):290-6

Abstract:

Impaired wound healing in older individuals may result from a global deficit of fibroblast activity or a decreased response of aged fibroblasts to stimulation by inflammatory cytokines. Twenty-eight fibroblast cell strains were developed from normal human skin aged 3 days to 84 years. Mitogenic response to cytokines, epidermal growth factor, tumor necrosis factor-alpha, platelet-derived growth factor or fetal bovine serum was determined using a 4-hour 3H-thymidine incorporation assay. Synthesis of collagen and noncollagen proteins was determined basally and in response to transforming growth factor-beta using a 6-hour 3H-proline incorporation assay. Neither the mitogenic response to cytokine stimulation (p > 0.3) nor the synthesis of collagen and noncollagen protein after transforming growth factor-beta stimulation (p > 0.4) varied with the age of the cell donor. Individual cell lines’ response to cytokine stimulation varied widely, reflecting differences commonly seen in patients’ wound-healing abilities. Cellular responses to wound-healing cytokines are preserved as people age. Abnormalities in wound healing in older patients may be the result of altered immune initiation of healing or the cumulative result of concomitant disease.

Grasilli, E., et. al. (1996) C-fos expression and AP-1 Activation in Skin Fibroblasts from Centenarians, Biochem and Biophys. Res. Comm; 226, 517-523

Jarisch, A., Krieg, T., and Hunzelmann, N. (1996) Regulation of collagen expression by interleukin-1 beta is dependent on donor age, Acta Derm Venereol; 76(4): 287-290.

Campisi J. (1996) Replicative senescence: an old lives’ tale? Cell Feb 23; 84(4):497-500

Campisi J. (1997) Aging and cancer: the double-edged sword of replicative senescence. J Am Geriatr Soc Apr; 45(4):482-8

Abstract:

Normal cells do not divide indefinitely. This trait, termed the finite replicative life span of cells, limits the capacity for cell division by a process termed cellular or replicative senescence. Replicative senescence is thought to be a tumor suppression mechanism and also a contributor to organismic aging. This article reviews what is known about the genetics and molecular biology of cell senescence. It discusses the evidence that replicative senescence suppresses tumorigenesis, at least in young organisms, and that it also contributes to the aging of mitotic tissues. Finally, it puts forth the somewhat unorthodox view that, in older organisms, senescent cells may actually contribute to carcinogenesis.