Background: Matrix metalloproteinases (MMPs) are key players in proteolytic blood-brain barrier (BBB) disruption during ischemic stroke, leading to vascular edema, hemorrhagic transformation and infiltration by leukocytes. Their effect is dampened by the endogenous tissue inhibitors of metalloproteinases (TIMPs). The respective cellular source of specific MMPs and TIMPs during BBB breakdown is still under investigation.
Methods: We analyzed the MMP and TIMP release of human brain microvascular endothelial cells (BMECs) under oxygen glucose deprivation (OGD). Cultured human BMECs (the hCMEC/D3 cell line) were subjected to OGD (6, 12, 18 and 24 h). Gene expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 were serially measured by quantitative real time-PCR and compared to ELISA-detected cell culture medium levels.
Results: OGD induced a significant and long-lasting increase in MMP-2 gene expression, reaching a plateau after 12 h. Medium protein levels of MMP-2 were correspondingly elevated at 12 h of OGD. The MMP-9 synthesis rate was detectable at very low levels and remained unaffected by OGD. TIMP-1 gene expression and secretion declined under OGD, whereas both expression and secretion of TIMP-2 remained stable. Contrary to the respective gene expression rate, medium levels of MMP-2, TIMP-1 and TIMP-2 started a simultaneous decline after 12 h of OGD. This is most likely due to an impaired synthesis and enhanced consumption rate under OGD.
Conclusions: The objective of our study was to determine the contribution of human BMECs to the MMP metabolism under in vitro OGD conditions simulating ischemic stroke. Our results suggest that human BMECs switch to a proinflammatory state by means of an enhanced production of MMP-2, attenuated release of TIMP-1, and unaffected production of TIMP-2. Thus, human BMECs might participate in the MMP-mediated BBB breakdown during ischemic stroke. However, our data does not support human BMECs to be a source of MMP-9.
Copyright © 2013 S. Karger AG, Basel.