Phénotypes des fibroblastes d'embryons de souris vieillissant in vitro (sem et tem)

Concerning their proliferative capacity, primary cultures of embryonic mice (Balb) firboblasts behave like human diploid fibroblasts. The phenotypes of early passage cells and late passage cells, at the beginning of the last generation life-time, look very different. Early passage cells, despite their heterogenous morphology, bear similar features (phenotype I): cells thick and small, surface smooth, filopodia few and simple, well organized small bundles of microfilaments, some microtubules, ergastoplasmic cisternae abundant and dilated. Late passage cells look very homogenous (= phenotype II): cells thin and large, surface with microvilli, filopodia numerous and dichotomized, microfilaments very abundant but poorly organized, many microtubules, ergastoplasmic cisternae sparse and small. In middle aged cultures, beside very rare phenotype II cells, we observed a mixture of fibroblasts of phenotype I and of an intermediary I/II phenotype. The passage from I to II seems to be progressie. We suggest that the phenotype II, shown by all the late passage cells, should be a terminal (in vitro) differentiated type. True (degenerative) senescence would occur later on in these differentiated cells (as in any differentiated cells), leading to delayed death.SCOPUS: NotDefined.j