PARENT SESSION
SLIDE SESSION 14: GROWTH FACTORS IN REPRODUCTIVE TISSUES
Chairs: Andrea Cupp, Barbara Vanderhyden, Wendy Ingman (Trainee)
Univ Ottawa-Lamoureaux 122
1:30 PM-3:30 PM

VASCULAR ENDOTHELIAL GROWTH FACTOR (VEGF) EXPRESSION AND LOCALIZATION INDICATES ROLE IN TESTIS MORPHOGENESIS AND SERTOLI-GERM CELL INTERACTIONS DURING EMBRYONIC TESTIS DEVELOPMENT.

Clopton, Debra¹, Toombs, Candice¹, Cupp, Andrea¹, ¹

ABSTRACT- Abnormal expression of VEGF and VEGF-stimulated genes results in abnormal testis morphogenesis, spermatogenic arrest, and male infertility. However, there is limited information on the site of action and function of VEGF within the testis, especially during early development. Because of the critical role of VEGF in vascular development, and the effects on male fertility, the hypothesis tested was that VEGF and its receptors would be expressed at critical time points during testis development and localized to cells which initiate endothelial cell migration and blood vessel formation. Expression and localization of VEGF and its receptors Flt-1 and Flk-1 was examined just after seminiferous cord formation {embryonic day 14 (E14; E0 = plug date)}, and when critical Sertoli and germ cell proliferation occurs (E16 and E18). Expression of VEGF mRNA was present at E14 and E16 but was barely detectable at E18 of embryonic testis development with reverse-transcription PCR (RT-PCR). Flk-1 was present at all days examined, E14, E16 and E18. However, the band for Flt-1 was faint at E14 and E16 with a more visible band at E18 of testis development. The expression pattern of both of these receptors correlates with their putative functions in vascular development in other organ systems. VEGF and Flk-1 are involved in formation of new vasculature during organogenesis while Flt-1 and VEGF function to maintain and remodel existing blood vessels. VEGF was localized to cells within the seminiferous cords at E14, and became localized to germ cells by E18 of testis development. Flk-1 was expressed in both the interstitium and Sertoli cells at E14 and by E18 was mainly in Sertoli cells. Flt-1 was localized to the seminiferous cords and interstitium at E14 with localization mainly to Sertoli cells at E18. Interestingly, the majority of expression for VEGF and its receptors occurred in cells that were not involved in vascular development. Therefore, this would indicate that in addition to angiogenic functions, there also are novel non-angiogenic roles (Sertoli-germ cell interactions) for VEGF during embryonic testis development.

KEY WORDS: embryonic testis, vascular development, seminiferous cord formation, Sertoli-germ cell interactions