In vivo assessment of class-specific inducible inhibitors of metalloproteinases in osteoarthritis

• Main Author: Lo Cascio, Leandro
• Other Authors: Bou-Gharios, George
• Published: Imperial College London 2015
• Subjects: 610
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682103

The role of articular cartilage is providing a painless and attrition-free surface for joints movements. Osteoarthritis (OA) is a debilitating multifactorial pathology characterized by progressive articular cartilage loss, exposition of the bone surface accompanied by pain, and final loss of joint functions. To date there is not an effective alternative to surgical replacement of damaged joints. Metalloproteinases (MPs) play an important role in cartilage remodelling both in physiological and pathological conditions. Among the metalloproteinases, the aggrecanase family was shown to be the major family responsible for aggrecan breakdown, while matrix metalloproteinases (MMPs) target preferentially the collagen molecules. Tissue inhibitor of metalloproteinases (TIMPs) are the endogenous regulators of those enzymes and in particular TIMP-3 was found to possess the broadest activity. So far all synthetic MP inhibitors failed in trials for OA treatment, and TIMP-3 may prove to be a possible alternative. Notably several synthetic mutants were generated to restrict its activity towards metalloproteinases. In order to test the potential therapeutic effects of these proteins, I decided to employ transgenic overexpressing mice. However I appreciated that it is of paramount importance to restrict the exogenous expression just to cartilage. Moreover because it was previously observed that overexpression of TIMP-3 in cartilage severely affects bone development and caused embryonic lethality, I decided to generate tissue specific inducible transgenic mice. I focused on the Aggrecan promoter in order to achieve specific cartilage expression and the Cre/loxP system to obtain inducible expression. Here I show the design and generation of a new aggrecan-driven Cre deleter mouse line. These mice can effectively target floxed genes in cartilage. I also show the generation of inducible TIMP-expressing mouse lines for both a cartilage-specific and ubiquitous expression. I aim to induce OA in those transgenic mice, after induction of TIMPs expression, to evaluate the inhibitors role in OA treatment.