Presence of matrix metalloproteinases and tissue inhibitor of matrix metalloproteinase in human sperm

The matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade protein components of the extracellular matrix. The necessity of breakdown of physical barriers in the fertilization process suggests that MMPs, along with their tissue inhibitors (TIMPs), might be involved in this task. We have examined the presence of MMP and TIMP in normal and abnormal human sperm samples by gel zymography and Western blot analysis. Thirty-five normal sperm samples and 35 abnormal sperm samples were examined in this study. Gel zymography showed 92-, 72-, 62-, and 28-kd molecular-weight bands exhibiting gelatin-degrading activity in both normal and abnormal sperm samples. The 92-, 72-, and 62-kd bands with gelatinolytic activity are consistent with pro-MMP-9, pro-MMP-2, and active MMP-2, respectively (pro-MMP being the zymogen of MMP). Western blot analysis showed the presence of TIMP-1 in both normal and abnormal sperm samples. A higher 28-kd activity and a lower 92-kd MMP activity in normal sperm samples relative to abnormal samples were detected. No marked difference in TIMP-1, 72-kd, and 62-kd release was observed between normal and abnormal sperm samples. In conclusion, this is the first report of MMP activity in normal and abnormal human sperm samples and of TIMP presence in sperm samples. The data indicate a different MMP profile between normal and abnormal sperm samples, with a higher 28-kd activity and a lower 92-kd MMP activity in normal relative to abnormal samples.