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Degree

PHD, Kent State University, School of Biomedical Sciences, 2005.

Abstract

Bcl-2 is an anti-apoptotic protein that has recently been shown to regulate other cellular functions. We previously reported the novel function of Bcl-2 that regulates chondrocyte matrix gene expression, independent of its anti-apoptotic function. The first hypothesis was that Bcl-2 regulates chondrocyte phenotype through the specific pathways. The role of three intracellular signaling pathways likely to be associated with Bcl-2 function, namely, NFkappaB, PKCalpha, and ERK1/2, was examined. The NFkappaB and PKCalpha signaling pathways were not involved in Bcl-2 regulated matrix expression, even thought these are known to regulate Sox9. The ERK1/2 signaling pathway was activated in Bcl-2 deficient cells that lost the chondrocyte phenotype by decreasing chondrocyte matrix protein expression and increasing fibroblastic collagen expression. The inhibition of phopspho-ERK1/2 reversed cells to have chondrocyte phenotype. Moreover, the MEK-ERK1/2 pathway limits the gene expression of matrix protein in wild type chondrocytes. These data indicate that Bcl-2 regulates chondrocyte phenotype through the MEK-ERK1/2 pathway. The second hypothesis was that Bcl-2 regulates chondrocyte phenotype in vitro as well as in vivo specifically, in human osteoarthritis. Osteoarthritis (OA) is an age-related degenerative cartilage disease and is known that the chondrocyte phenotype is altered. However, the significance of the altered phenotype in OA is unclear due to the use of non-age match samples, different source of samples, and lack of precise determination of the stage of OA progression. We developed an intrajoint comparison model using human OA samples to control for patient age and genetic background effects. The advanced OA cartilage was taken from within 1cm of overt lesions. In contrast, minimal OA cartilage was taken from areas without any obvious lesions. The chondrocyte matrix protein and Bcl-2 mRNA expression was decreased in advanced OA cartilage compared with minimal OA cartilage in most of patients studied. In contrast, osteopontin mRNA expression was up-regulated in advanced OA cartilage compared with minimal OA cartilage. A correlation was observed between the steady state mRNA coding for aggrecan and Bcl-2, and Bcl-2 and Sox9. These results support the hypothesis that Bcl-2 regulates chondrocyte phenotype in vivo as well as in vitro.

Keywords

Chondrocytes; Osteoarthritis; Sox9; Bcl-2; MEK-ERK1/2

Advisor

Walter E Horton

Pages

113p.

Document number: kent1118329494
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=kent1118329494

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