63 IMPROVEMENT OF SEMEN-DERIVED EPITHELIAL CELL PROLIFERATION BY FIBROBLAST CO-CULTURE

Abstract

We previously isolated epithelial-like cells (ELC) from sheep (Ovis aries) and eland (Taurotragus oryx) semen (Nel-Themaat et al. 2004 Reprod. Fertil. Dev. 16, 152) and subsequently developed a system to separate ELC before plating (Nel-Themaat et al. 2005 Reprod. Fertil. Dev. 17, 314). Cells attached and proliferated in only 50% and 31% of the attempts, respectively. Therefore, the purposes of the present study were to improve ELC proliferation by co-culture with inactivated 3T3 mouse fibroblasts and to characterize the obtained cells. Semen fractions from two mature Gulf Coast Native rams (n = 20 ejaculates) and one common eland bull (n = 2 ejaculates) were plated on feeder layers (A), on collagen with feeder cell inserts (B), or on collagen alone (C). For B and C, cell attachment and division were assessed; proliferation and passage 1 (P1) confluence were evaluated for A, B, and C. No difference in attachment rates between B (80%) and C (70%) were found for ovine cells, but (P < 0.05) cells divided more times in B (80%) than in C (35%). All colonies in A (60%) and B (70%) reached P1 confluence and no difference was detected between A and B, but less proliferation (10%) and P1 confluence (5%) were observed in C. Therefore, contact between epithelial cells and feeders was not necessary for growth stimulation by the feeder cells. No difference among A, B, and C was detected for eland ELC proliferation (100%), but no P1 confluence was observed in C. Ram cells were subsequently characterized by immunohistochemical detection of keratin and vimentin, as well as morphology. The 3T3 cells cross-reacted with keratin, and characterization was thus performed mainly on morphology and vimentin expression. Distribution of vimentin microfilaments differed between different epithelial morphologies and fibroblasts. Expression in epithelial cells was faint and patchy in confluent colonies and located around cytoplasmic extremities in semi-confluent colonies. In 3T3 cells, expression was very prominent throughout the cytoplasm and around the nucleus. For treatments A and B, 63 and 57%, respectively, were characterized as only epithelial cells; 25 and 36%, respectively, appeared to contain a mixture of epithelial and fibroblast cells; and 13 and 7%, respectively, contained only fibroblast cells. Only one sample was evaluated from treatment C and only keratin was detected in the epithelial-like colony. We conclude that culture of semen-derived ELC is markedly improved by 3T3 fibroblast co-culture. Further research on conditioned media may simplify the system and reduce chances of 3T3 cell contamination.