RESUMO
OBJECTIVE: To evaluate the effects of electrical stimulation (ES), stretching and their combined effects in matrix metalloproteinases (MMPs) gene expression and activity during early denervation of rat tibialis anterior (TA) muscle by axonotmesis. METHODS: Thirty adult male Wistar rats were divided into five groups: normal (N), denervated TA (D), denervated TA submitted to daily ES (D + ES), denervated TA submitted to daily stretching (D + St) and denervated TA submitted daily to both ES and stretching concurrently (D + ES + St). Both zimographic analysis and real time polymerase chain reaction of MMPs were used to muscular evaluation. In addition, muscle fiber cross-section area (CSA) was also evaluated. RESULTS: Stretching increased MMP-2 activity in denervated muscle when performed alone as well as in association with ES (p<0·01). Both stretching and ES, individually and in association, increased MMP-2 gene expression in denervated muscle compared to N and D (p<0·05). All denervated groups decreased muscle fiber CSA compared to N (p<0·05). DISCUSSION: While stretching is the main stimulus leading to the activation of MMP-2, both ES and stretching are able to increase MMP-2 gene expression in rat denervated muscle suggesting ECM remodeling.