Evaluating the Balance Regulating Matrix Remodeling

Background Myelinating Schwann cells (mSCs) form myelin in the peripheral nervous system. Because of the works by us and others, matrix metalloproteinase-9 (MMP-9) has recently emerged as an essential component of the Schwann cell signaling network during sciatic nerve regeneration. Methodology/Principal Findings In the present study, using the genome-wide transcriptional profiling of normal and injured sciatic nerves in mice followed by extensive bioinformatics analyses of the data, we determined that an endogenous, specific MMP-9 inhibitor [tissue inhibitor of metalloproteinases (TIMP)-1] was a top up-regulated gene in the injured nerve. MMP-9 capture followed by gelatin zymography and Western blotting of the isolated samples revealed the presence of the MMP-9/TIMP-1 heterodimers and the activated MMP-9 enzyme in the injured nerve within the first 24 h post-injury. MMP-9 and TIMP-1 co-localized in mSCs. Knockout of the MMP-9 gene in mice resulted in elevated numbers of de-differentiated/immature mSCs in the damaged nerve. Our comparative studies using MMP-9 knockout and wild-type mice documented an aberrantly enhanced proliferative activity and, accordingly, an increased number of post-mitotic Schwann cells, short internodes and additional nodal abnormalities in remyelinated nerves of MMP-9 knockout mice. These data imply that during the first days post-injury MMP-9 exhibits a functionally important anti-mitogenic activity in the wild-type mice. Pharmacological inhibition of MMP activity suppressed the expression of Nav1.7/1.8 channels in the crushed nerves. Conclusion/Significance Collectively, our data established an essential role of the MMP-9/TIMP-1 axis in guiding the mSC differentiation and the molecular assembly of myelin domains in the course of the nerve repair process. Our findings of the MMP-dependent regulation of Nav channels, which we document here for the first time, provide a basis for therapeutic intervention in sensorimotor pathologies and pain.

Objectives: The aim of the study was to determine whether the release by macrophages of matrix metalloproteinase (MMP)-12 and vascular endothelial growth factor (VEGF) - leading to inflammation, matrix degradation and neoangiogenesis - represents an effective pathway that underlies aortic wall remodeling in Stanford type A acute aortic dissection (AAD). Methods: Twenty-one consecutive patients with no genetic predisposition, with Stanford type A AAD were selected. In each patient, the levels of serum VEGF, MMP-12, serum interleukin (IL)-6, IL-8 and monocyte chemoattractant protein (MCP)-1 were evaluated using enzyme-linked immunosorbent assay. Ascending aortic specimens were collected for immunohistochemical identification of any presence of inflammatory infiltrate, VEGF and CD31 expression. Results: A significant increase in serum VEGF (p = 0.044), MMP-12 (p = 0.007), IL-6 (p = 0.0001), IL-8 (p = 0.0001) and MCP-1 (p = 0.0001) levels was observed in the AAD group compared to the control group. Furthermore, all AAD samples were positive for VEGF in the tunica media and showed vessel growth and immune-inflammatory infiltrate. A large number of cases (62.79%) showed inflammation at the edge of the dissection and approximately half (51.42%) showed neovessels growing at the edge of the dissection. Conclusions: The results suggest that VEGF-mediated angiogenesis and matrix degradation play a role in AAD. Finally, we believe that MMP-12 should be considered a marker of AAD.