Matrix metalloproteinase (MMP) may be required for gonocyte transformation in postnatal l testicular tubules (#209)
Background and Aim: Cryptorchidism may cause infertility by failed transformation of neonatal gonocytes into adult dark spermatogonia (AD-S), the putative stem cells for spermatogenesis (1-3). Gonocytes migrate centrifugally to the tubular basement membrane to become AD-S. Regulation of this transformation remains unknown. We aimed to investigate neonatal rodent testis MMP production to see whether MMPs loosen extracellular matrix between Sertoli cells to facilitate gonocyte movement.
Methods: Sprague-Dawley rat testes (n=4-6 per group) were collected at embryonic day 19 (E19), postnatal (P) days P0 (birth), P2, P4, P6, P8 and P10 and fixed in 4% paraformaldehyde in phosphate-buffered saline (PBS) for immunohistochemistry. Immunofluorescent confocal images were captured for presence of MT1-MMP, MMP2, TIMP2, MVH, AMH and AR in paraffin embedded tissue sections. MVH-positive gonocytes in cross-sections of testicular tubules in confocal images were counted and analysed. Testicular proteins were analysed by immunoblotting .
Results: MT1-MMP was strongly present in gonocytes at E19, then decreased, whereas it increased in testicular somatic cells from P0 to P10. Testicular protein levels of MT1-MMP, MMP2 and AR were constant from E19 to P10. AMH protein sharply decreased after P2, while TIMP2 gradually increased from E19 to P10. Number of MVH+ germ cells decreased from 13 per tubular cross-section at E19 to 1 at P6, then started to increase from P8 to P10. Gonocytes migrated to basement membrane at P2-6 where spermatogonia stem cells are localized.
Conclusion: MT1-MMP, MMP2 and TIMP2 were present in testis from E19 to P10 during gonocyte migration and transformation into spermatogenic stem cells. Increased knowledge about germ cell development may aid efforts to improve fertility in cryptorchidism.
1.Hadziselimovic F, Huff D. Adv Exp Med Biol. 2002;511:15-21; discussion 3.
2.Ong C, Hasthorpe S, Hutson JM. Pediatric Surgery International. 2005;21(4):240-54
3.Hadziselimovic F, Hocht B, Herzog B, et al, Horm Res. 2007;68(1):46-52.