to detect the expression of hsp25 in rat dental follicles both in vivo and vitro , and explore the underlying mechanism of hsp25 on the proliferation and differentiation of rat dental follicle cells ( dfcs ) . immunohistochemistry was performed to detect the expression of hsp25 in mandibles of postnatal rats on days 1 , 3 , 5 , 7 , 9 and 11 in vivo . in vitro , thiazolyl blue tetrazolium bromide ( mtt ) assay , flow cytometry and alkaline phosphatase ( alp ) assay were used to identify the time - course effect mediated by different concentrations of recombinant murine hsp25 of 0 , 1 , 10 , 50 and 100 ng / ml on rat dfcs . expression of hsp25 was not detected in dental follicles of the rats until day 5 after birth , but became up - regulated in a time - dependent manner till day 11 . no significant difference could be observed in the proliferation of dfcs after stimulation with different concentrations of hsp25 on days 1 , 2 and 3 ( p>0.05 ) . hsp25 at concentrations of 50 ng / ml and 100 ng / ml up - regulated the alp activity of dfcs on day 9 ( p<0.05 ) . hsp25-immunoreactivity increased chronologically during the development of dental follicles . the protein had no significant effect on cell proliferation but may play a role in cementoblast / osteoblast differentiation of dfcs .