Back pain caused by degenerative disc disease is associated with significant costs and patient morbidity. Although previous studies have thoroughly investigated the matrix of degenerated discs, few studies have investigated the subset of degenerated discs that are specifically painful. Detailed knowledge of how these properties in painful discs compare to those of nonpainful discs will provide guidelines for the development of tissue engineered treatment. The goal of the current dissertation is to characterize the matrix of the painful disc and investigate nucleus pulposus tissue engineering.
We characterized painful and nonpainful discs that were harvested from waste tissue of human surgical patients. The mechanical properties, matrix properties, and matrix synthesis of these tissues were measured using mechanical indentation, hydration, biochemistry, histology, and gene expression. Our data indicated that the painful annulus had altered gene and protein expression of proteoglycan and collagen, and consequent diminished mechanical properties. In contrast, the painful nucleus had elevated gene expression of decorin and higher energy dissipation than the nonpainful nucleus. Interestingly, gene expression data of several proteoglycans and collagens correlate with indentation and hydration properties.
In addition to characterizing the matrix properties of painful discs, we investigated the differentiation of human mesenchymal stem cells (MSCs) into nucleus pulposus cells for tissue engineering. Specifically, MSCs were seeded into a three-dimensional alginate scaffold, pretreated with growth factor, and stimulated with mechanical compression. The effect of compressive stimulation on cell differentiation was measured by gene expression of several chondrogenic markers, including aggrecan, collagen II, Sox9, collagen I, and collagen X. Our data indicate that growth factor treatment promotes production of chondrogenic matrix proteins, including proteoglycans and collagen II; however, compressive stimulation had no effect on gene markers of chondrogenic differentiation.
The results of this dissertation suggest that painful discs have diminished mechanical and matrix properties. Importantly, these diminished properties have previously been associated with pain mechanisms via disc hypermobility, stress concentrations, and reduced barriers to nerve infiltration. Although our investigation of MSC differentiation with compressive stimulation was inconclusive, our characterization of painful disc matrix may guide future attempts to regenerate painful degenerated discs.
|1989||Cassidy JJ, Hiltner A, Baer E. Hierarchical structure of the intervertebral disc. Connect Tissue Res. 1989;23(1):75-88.|
|1999||Wilke H-J, Neef P, Caimi M, Hoogland T, Claes LE. New in vivo measurements of pressures in the intervertebral disc in daily life. Spine. April 15, 1999;24(8):755-762.|
|2000||Mauck RL, Soltz MA, Wang CCB, Wong DD, Chao P-HG, Valhmu WB, Hung CT, Ateshian GA. Functional tissue engineering of articular cartilage through dynamic loading of chondrocyte-seeded agarose gels. J Biomech Eng. June 2000;122(3):252-260.|
|1995||Buschmann MD, Gluzband YA, Grodzinsky AJ, Hunziker EB. Mechanical compression modulates matrix biosynthesis in chondrocyte/agarose culture. J Cell Sci. April 1995;108(4):1497-1508.|
|1961||Woessner JF Jr. The determination of hydroxyproline in tissue and protein samples containing small proportions of this imino acid. Arch Biochem Biophys. May 1961;93(2):440-447.|
|1999||Pittenger MF, Mackay AM, Beck SC, Jaiswal RK, Douglas R, Mosca JD, Moorman MA, Simonetti DW, Craig S, Marshak DR. Multilineage potential of adult human mesenchymal stem cells. Science. April 2, 1999;284(5411):143-147.|
|1990||Thompson JP, Pearce RH, Schechter MT, Adams ME, Tsang IK, Bishop PB. Preliminary evaluation of a scheme for grading the gross morphology of the human intervertebral disc. Spine. May 1990;15(5):411-415.|