PARENT SESSION

(M724) CLOSE CORRELATION BETWEEN COLLAGEN IV 1 SUBUNIT UP-REGULATION AND SEXUAL DIMORPHIC EPITHELIAL MORPHOGENESIS OF THE RAT GONAD.

Magre, Solange¹, Mazaud-Guittot, Severine^{1, 2}, ¹ CNRS-Paris VI University UMR-7079, Paris, France² CRBR-CHUL Research Center, Laval University, Ste-Foy, QC, Canada

ABSTRACT- In both male and female gonads, the germ cell lineage is supported by epithelial cells, Sertoli and granulosa cells, respectively. Whereas in the male, Sertoli cells differentiate early during the fetal development and aggregate to form testicular cords, their counterparts in the ovary arrange into ovigerous cords during fetal life, and differentiate later on into granulosa cells, as follicular units emerge from fragmenting ovigerous cords. Recent advances have led to a better understanding of the molecular cascade underlying sexual differentiation, but the mechanisms of epithelial structure building are still not well understood. To investigate epithelial morphogenetic processes and specifically the contribution of the different cell types in basal membrane synthesis, we analyzed the expression pattern of one of its essential components : the 1 subunit of collagen IV. In situ hybridization revealed that in the fetal rat testis, Col4a1 expression was transiently up-regulated in Sertoli cells when they differentiate and aggregate and durably up-regulated in mesenchymal cells. In the fetal ovary, Col4a1 was expressed by endothelial and peri-endothelial cells. Immediately after birth, as follicle histogenesis initiated, its expression was up-regulated transiently in epithelial granulosa cells and durably in mesenchymal cells of the theca lineage. We further tracked the role of collagen deposition during epithelial gonadal morphogenesis by organotypic cultures using the ring prolin analog L-Azetidin-2-Carboxilic Acid (LACA) to inhibit collagen IV secretion. LACA induced the progressive scattering of fetal Sertoli cells with a time-dependent manner. In the ovary, LACA did not perturb ovigerous cord formation but efficiently inhibited their remodeling into follicular units. Our results thus demonstrate that collagen secretion is a key event of the terminal differentiation of both male and female epithelial gonadal structures.

KEY WORDS: collagen, gonadal epithelium morphogenesis, rat