MT1-MMP in rat testicular development and the control of Sertoli cell proMMP-2 activation

Metalloproteases (MMPs) are likely to be involved in the restructuring events occurring in the testis throughout development. We here demonstrate that membrane-type 1 (MT1)-MMP, a physiological activator of proMMP-2 under TIMP-2 control, is present within the testis together with MMP-2 and TIMP-2. In the prepubertal testis MT1-MMP immunoreactivity was uniformly distributed, whereas in the adult it was confined to the apical compartment of the tubules, where meiosis and spermiogenesis occur. We further showed that the two cell lineages (somatic and germinal) expressed MT1-MMP and TIMP-2, whereas MMP-2 was of somatic origin. To get a better picture into proMMP-2 activation, use was made of a model of cultured Sertoli cells treated with FSH or co-cultured with germ cells to mimic an immature or a mature developmental period, respectively. We found that follicle-stimulating hormone enhanced the expression of MMP-2 and TIMP-2 but not of MT1-MMP, and promoted the activation of proMMP-2. In co-cultures, a tremendous elevation and activation of MMP-2 was observed, which might relate to the processed MT1-MMP form solely detected in germ cells. That MMP-2 synthesis and activation are under local (germ cells) and hormonal (follicle-stimulating hormone) regulation emphasizes the importance of MMPs in testicular physiology.