EXPRESSION OF INSULIN-LIKE GROWTH-FACTORS IN 2 BOVINE OVIDUCTAL CULTURES EMPLOYED FOR EMBRYO COCULTURE

We have investigated the patterns of expression and cellular localizat ion of polypeptides and mRNAs encoding TGF-I and IGF-II in intact bovi ne oviduct and two bovine oviductal primary cultures (monolayers and v esicles) which are utilized for supporting development in vitro. IGF-I and IGF-II polypeptides were localized by immunocytochemistry in inta ct oviduct and in both primary cultures for an 8-day culture interval, but IGF-II polypeptide displayed a more restricted distribution in da y 8 monolayer cultures. IGF-I and IGF-II mRNAs were localized in both oviductal cell cultures as assessed by in sih hybridization. We were u nable to detect IGF-I and IGF-II mRNAs in intact oviduct by in situ hy bridization; however, transcripts encoding IGF-I and IGF-II mRNAs were detected in intact oviduct cell preparations and all primary culture samples by reverse transcription-PCR methods. The origin and phenotypi c stability of these cultures was assessed by immunostaining with anti bodies raised against vimentin (mesenchymal cell marker) and cytokerat in (epithelial cell marker). Over the culture period, the proportion o f vimentin-immunoreactive cells increased in the monolayer cultures bu t remained at a low level in the vesicle cultures which were predomina ntly composed of cytokeratin-positive cells. The results suggest that oviductal cell co-culture may facilitate early mammalian development, in part, by the establishment of paracrine growth factor circuits.