Variation in expression and activity pattern of mmp2 and mmp9 on different time scales in the regenerating caudal fin of Poecilia latipinna.

Alteration in the expression pattern of matrix metalloproteinase (MMP)2 and MMP9 was studied in the regenerating caudal fin of Poecilia latipinna immediately following amputation until the new tissues gained structural integrity. Timed expression pattern of these two MMPs was studied at enzyme, transcript as well as protein levels. Additionally, both the gelatinases were localized in the regenerating caudal fin during three specific stages of regeneration. The results revealed a progressive increase in the expression of MMP2 starting at 1 h post amputation (hpa), indicating its possible role in the remodelling of extracellular matrix early on during caudal-fin regeneration. Nevertheless, a reduction in transcript level expression of MMP2 at 6 hpa and 12 hpa stages, points towards a possible transcriptional regulation, to further moderate its activity. As observed in the case of MMP2, expression of MMP9 too increased from 1 hpa and remained elevated until 5 dpa. However, the active MMP9 revealed its presence only 12 hpa onwards. Moreover, both the gelatinases were localised in the apical epithelial cap and in the progress zone at wound epithelium (1 dpa) and blastema (60 hpa) stages respectively. Further, during early differentiation stage (5 dpa), high intensities of MMP2 and MMP9 were localized in the newly formed actinotrichia as compared with the tissue proximal to it. Based on the results, it could be construed that the controlled up-regulation of MMP2 and MMP9 from 1 hpa until the early differentiation stage ensures a regulated digestion of extracellular matrix, perhaps to facilitate the recruitment, proliferation, morphogenesis and re-patterning of resident stem cells during caudal fin regeneration in P. latipinna.