The mammary gland is unique in its development because most of its branching occurs in adolescent rather than in prenatal development. During early pregnancy extensive ductal side branching occurs while during the second half, secretory lobuloalveolar units are formed within the mammary gland. As modulators of the extracellular matrix, matrix metalloproteinases (MMPs) are the major enzymes taking part in the development of the gland. The activity of MMP-2 and MMP-9 has mostly been associated with tumor progression, while their participation in the physiological development of the mammary gland is not well characterized. In the present study the cell-specific localization of MMP-2 and MMP-9 in the developing dog mammary gland during pregnancy was investigated. In the early stages, both gelatinases were present, being located mostly in the epithelium of the ducts and less so in the surrounding stroma. After the formation of alveoli, MMP-2 was still present but MMP-9 was absent from the glandular epithelium and the stroma, being present only in the epithelium of the larger ducts. The results show that most likely, both gelatinases take part in ductal branching during early pregnancy, but only MMP-2 is associated with the differentiated stage of lactation.
Matrix metalloproteinases (MMPs) areagroup of proteases containing Zn ions asacofactor, which are involved in degrading ofalarge number of extracellular matrix proteins, and bioactive molecules. They also playamajor role in processes such as cell proliferation, cell migration, differentiation and apoptosis. Very little is known about the expression and function of MMPs in the male reproductive tract. Occurrence of MMP-2 and MMP-9 activity in human seminal plasma has been previously reported but their origin and function are still not fully understood. The aim of this study was to examine the presence of MMP-2 and MMP-9 in normal and abnormal human sperm samples and find if any correlation existed between the levels of expression of MMPs and fertilization potential of the spermatozoa. Human spermsamples were examined for the presence of MMP-2 and MMP-9 by gel zymography and western blot analysis. A DNAfragmentation test was performed. The samples were divided into two groups - samples with normozoospermia and teratozoospermia. The gelatin zymography showed gelatinolytic bands with molecular weight 64 and 72 k Da corresponding to active and inactive form of MMP-2. MMP-9 was not detected. The MMP-2 enzymatic activity appeared to be much higher in samples with compromised sperm morphology as compared to the normozoospermic samples. The mean DNAfragmentation index (DFI) of the group with teratozoospermia was relatively higher (22.16%) and over the upper reference limits, compared to the normozoospermic group, in which it was within the normal range (17.26%).