Defining Common Molecular Parameters For Onset and Progression of Osteoarthritis

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DESCRIPTION (provided by applicant): This RC4 application in thematic area 1-- Applying Genomics and Other High Throughput Technologies-is an integrated, multi-disciplinary strategy to achieve a major "leap forward" in defining common biomolecular mechanisms underpinning osteoarthritis (OA). Rational therapeutic strategies against specific targets that determine the onset and severity of OA disease are severely lacking. Traditional prior efforts have primarily focused on single regulatory molecules, thereby hindering our ability to decipher the puzzle underlying the development of what is clearly a multifactorial disease or group of diseases. Prior achievements of our team of investigators have led to the development of novel murine models of OA disease and, of equal importance, also uncovered roles of specific transcription factors and upstream signaling molecules contributing to chondrocyte stress and differentiation. Among these are NF-B, Runx2, ESE-1/Elf3, GADD452, and DDR2, each of which impact on the expression of MMP-13, the major collagen-degrading enzyme in chondrocytes. Thus, our findings provide a conceptual framework that will be exploited to analyze unbiased genome-based and phospho-proteome screens across multiple mouse OA disease models. We hypothesize that stress- or inflammation-induced signals not only contribute to IRREVERSIBLE joint damage (progression) in OA, but importantly, also to the initiation/onset phase, wherein chondrocytes in articular cartilage leave their natural growth- and differentiation-arrested state. We will employ 3 carefully chosen murine OA models, each of which affect OA disease development by different inherent changes in chondrocyte function and physiology: (1) diminished expression of Runx2, a pivotal transcription factor that drives chondrocyte differentiation towards hypertrophy, and (2) loss of canonical NF-:B signaling, the major pathway orchestrating diverse responses to intracellular and extracellular stress, and (3) haploinsufficiency of type XI collagen in the cho/+ mutant mouse. Each of these 3 murine OA models will be subjected to the first integrated use of vanguard technologies of microRNA (miRNA) and gene expression arrays, phospho-protein proteomics (focusing initially on NF-:B, MAPK/ERK, p38, JNK, JAK/STAT, and Tak1/Smad cascades), and systems-level bioinformatics to define key networks and targets most commonly activated in genetic and post-traumatic murine OA. Importantly, the latter novel data will then be used to interrogate existing genome or proteome datasets from human OA cartilage, synovia and synovial fluids to uncover the conserved, clinically relevant targets in the context of the "whole joint" in OA disease development and progression. PUBLIC HEALTH RELEVANCE: This RC4 proposal (Thematic Area 1) involves a multi-disciplinary approach using powerful gene expression, miRNA, and single cell phospho-proteome screens that will give a comprehensive and integrated picture of the important regulatory networks in cartilage that impact on OA disease onset and progression. The innovative and coordinated efforts of multiple PIs at four different institutions will uncover novel 'common effectors' and critical networks across 3 murine models with post-traumatic or genetic OA. Moreover, interrogation against available human OA datasets will have clinically relevant impact in the context of the "whole joint" and uncover new therapeutic targets.