This dissertation, "Potential of Bone Marrow and Umbilical Cord Derived Mesenchymal Stem Cells in Intervertebral Disc Repair" by Fengjuan, Lu, 吕凤娟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Introduction: Intervertebral disc (IVD) degeneration is suggested to begin from the nucleus pulposus (NP). Evidence from various studies highlights mesenchymal stem cells (MSC), in most cases using bone marrow derived MSC, as a potential stem cell source for NP regeneration. However MSC can be isolated from many sources with various characteristics. There are indications that fetal or close to fetal tissue sources contain MSC with relatively undifferentiated phenotype with respect to MSC from adult sources. Moreover, umbilical cord (C)-MSC may have better chondrogenic differentiation potential than bone marrow (B)-MSC. We hypothesize CMSC are different from BMSC, and more efficient than BMSC in stimulating NP regeneration. Methods: MSC were isolated from human bone marrow and umbilical cord with corresponding ethical approval. BMSC and CMSC were characterized for cell surface marker expression profile and differentiation potential.. RT-PCR of interest genes in NP cells isolated from scoliosis and degenerate discs was performed to search for NP degeneration indicators. Conditioned media (CM) was collected from confluent MSC monolayer, and used for stimulation of four batches of degenerated NP cells isolated from human degenerative intervertebral discs. Cell proliferation and cytotoxicity were assessed by MTT assay. Proteoglycan content were measured by DMMB assay. Gene expression of a series of degeneration related molecules including ACAN, SOX9, CDH2, CD55, KRT19, KRT18, FBLN1 and MGP, and fibrosis related molecules, including MMP12, HSP47, COL1A1, COL3A1 and FN1, of NP cells in MSC-CM were determined by real- time RT-PCR. All results were normalized to the control cells in basal medium. The expression of discogenic, chondrogenic and osteogenic markers on BMSC and CMSC were compared by RT-PCR. Results and Conclusion: CMSC were similar to BMSC and fulfilled the minimum criteria of MSC, however the expression of CD146, CD106 and Stro-1 was different, and BMSC had a spontaneous osteogenesis tendency while CMSC expressed chondrogenic marker even without TGF-beta stimulation. BMSC demonstrated a paracrine effect on modulating human degenerated NP cells towards a non-degenerative phenotype in stimulating cell proliferation, slightly enhancing proteoglycan production, upregulating KRT19 while downregulating MMP12. Compared with BMSC, a higher paracrine effect of CMSC was disclosed in modulating the phenotype of NP cells in all aspects tested, and an intrinsic higher expression on CMSC of 'potential NP markers', including KRT19, KRT18 and CD55, but lower expression of osteogenic markers, including RUNX2 and ALPL, was revealed, which indicate a higher potential of CMSC for future clinical application to treat IVD degeneration diseases. KRT19 and MMP12 were also confirmed to be the highest differentially expressed candidate genes between cultured scoliosis and degenerated human NP cells, indicating a high indicator potential of NP degeneration. Furthermore, a subpopulation was detected in the degenerated NP cells that possessed macrophage-like phenotype and activities, which may play a role in the pathogenesis of