Overexpression of murine small heat shock protein HSP25 interferes with chondrocyte differentiation and decreases cell adhesion

Although multiple functions for the small heat shock protein HSP25 have bee n proposed, its specific role during developmental and differentiation proc esses is not known. Cartilage is one of the tissues in which HSP25 is speci fically and highly expressed during development. C1 cells, able to form agg regates in vitro, can be induced to differentiate into chondrocytes, In thi s study, we generated two stable transfected clones overexpressing HSP25 at two different levels, Cell morphology and growth rate were modified in bot h clones, although the actin content and distribution did not seem to be al tered. Overexpressing clones had more difficulties in coalescing, leading t o smaller aggregates and they did not differentiate into chondrocytes, Subs equently, these aggregates tended to dissociate into loose masses of dying cells. The strength of all these effects was directly correlated to the lev el of HSP25 overexpression. These data suggest that overexpressing HSP25 de creases cellular adhesion and interferes with chondrocyte differentiation.