Reacquisition of a spindle cell shape does not lead to the restoration of a youthful state in senescent human skin fibroblasts.

Senescent fibroblasts are characterized by their inability to proliferate and by a pro-inflammatory and catabolic secretory phenotype, which contributes to age-related pathologies. Furthermore, senescent fibroblasts when cultured under classical conditions in vitro are also characterized by striking morphological changes, i.e. they lose the youthful spindle-like appearance and become enlarged and flattened, while their nuclei from elliptical become oversized and highly lobulated. Knowing the strong relation between cell shape and function, we cultured human senescent fibroblasts on photolithographed Si/poly(vinyl alcohol) (PVA) micro-patterned surfaces in order to restore the classical spindle-like geometry and subsequently to investigate whether the changes in senescent cells' morphology are the cause of their functional alterations. Interestingly, under these conditions senescent cells' nuclei do not revert to the classical elliptical phenotype. Furthermore, enforced spindle-shaped senescent cells retained their deteriorated proliferative ability, and maintained the increased gene expression of the cell cycle inhibitors p16 and p21. In addition, Si/PVA-patterned-grown senescent fibroblasts preserved their senescence-associated phenotype, as evidenced by the overexpression of inflammatory and catabolic genes such as IL6, IL8, ICAM1 and MMP1 and MMP9 respectively, which was further manifested by an intense downregulation of fibroblasts' most abundant extracellular matrix component Col1A, compared to their young counterparts. These data indicate that the restoration of the spindle-like shape in senescent human fibroblasts is not able to directly alter major functional traits and restore the youthful phenotype.