Controlling chondrocyte matrix degradation and repair in 3-D culture.

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DESCRIPTION (provided by applicant): This proposal's long-term objectives are: 1) to provide basic knowledge about how manipulation of Inflammatory signaling pathways can affect the mechanical properties of chondrocyte created neo-matrix, and 2) to create a tissue-engineered surgical solution to restore osteochondral defects. These objectives will be through two specific aims: construction and analysis of tissue-engineered cartilage using 1) genetically-modified mouse chondrocytes with knockout of MKK/MEK3; and 2) pharmacologic inhibition of key signaling pathways (p38 and JNK MARK) that regulate proteoglycan and collagen deposition by chondrocytes in tissue-engineered cartilage. Analysis will encompass mechanical characterization, collagen, crosslink, and GAG content, multiphoton microscopy, and mathematical modeling of the tissue. The goals of this proposal are relevant to the mission of the NIH and NIAMS. Functional engineered cartilage would greatly alleviate cartilage damage which affects ~10% of the population (1). Information gained about the genetic determinants of cartilage neo-matrix formation would increase understanding of cartilage degradation in rheumatoid and osteoarthritis. This proposal has tissue engineering, multiphoton imaging, and mathematical modeling components, and is a multidisciplinary effort to advance basic knowledge of chondrocyte genetic programming in disease and repair processes. Chondrocytes from mice with knockouts and mutations of TNF-alpha and IL-1beta signaling elements will be harvested and seeded within alginate scaffolds to allow neo-matrix development. Tissue mechanical properties, collagen, proteoglycan, and crosslink content will be assessed during culture under normal and transgenic phenotype, and with or without pharmacologic inhibition of the same signaling pathways, known to affect extracellular matrix production (2). Multiphoton imaging will be used to assess collagen deposition and network structure (using signal from second harmonic generation) and collagen crosslink formation (through two-photon autofluorescence signal). Data from the tissue-engineered cartilage will be fit to a cartilage growth mixture model, previously developed to assess native cartilage (3). Every year, cartilage Injury affects nearly 1 million Americans resulting in 200,000 procedures. Injury often leads cryptically to osteoarthritis (1). Tissue-engineered cartilage is a promising method to examine chondrocyte-controlled cartilage degradation and repair. Understanding these processes in vitro would help clinicians control and repair cartilage through pharmaceutical, genetic, and surgical manipulations.