Telomerase expression restores dermal integrity to in vitro-aged fibroblasts in a reconstituted skin model

The lifespan of human fibroblasts and other primary cell strains can be ext ended by expression of the telomerase catalytic subunit (hTERT). Since repl icative senescence is accompanied by substantial alterations in gene expres sion, we evaluated characteristics of in vitro-aged dermal fibroblast popul ations before and after immortalization with telomerase. The biological beh avior of these populations was assessed by incorporation into reconstituted human skin. Reminiscent of skin in the elderly, we observed increased frag ility and subepidermal blistering with increased passage number of dermal f ibroblasts, but the expression of telomerase in late passage populations re stored the normal nonblistering phenotype. DNA microarray analysis showed t hat senescent fibroblasts express reduced levels of collagen I and III, as well as increased levels of a series of markers associated with the destruc tion of dermal matrix and inflammatory processes, and that the expression o f telomerase results in mRNA expression patterns that are substantially sim ilar to early passage cells. Thus, telomerase activity not only confers rep licative immortality to skin fibroblasts, but can also prevent or reverse t he loss of biological function seen in senescent cell populations. (C) 2000 Academic Press.