Upon aging, the intervertebral disc (IVD) inevitably undergoes degeneration characterized by biochemical and morphologic changes. IVD degeneration can lead to multiple clinical disorders such as back and neck pain, and myelopathy. Low back pain can disable up to 85% of the adult population and results in a significant restriction of social activities and inability to work. Such disorder incurs billions of dollars in medical expenditures each year. Despite advances in the detection and treatment of the degeneration, the regeneration of the IVD remains low because current therapies are limited by exogenous curing approaches. New strategies for the reversal of IVD degeneration, including gene, cytokine, and stem cell therapies that can influence the anabolic and catabolic pathways in disc cells have been under investigation. These therapies aim to rejuvenate or replace diminished nucleus pulposus cells in the degenerative IVD. Recent reports have put forth a proposal of “endogenous disc stem cells”, suggesting that cells derived from the degenerative IVD tissue possess stem cell properties. These putative stem cells are believed to regulate the development and homeostasis of the IVD tissue. In this study, we identified and characterized a stem cell population from the IVD of healthy Rhesus monkey, termed disc stem/progenitor cells (DSCs). We show that the DSCs possess clonogenicity, multipotency and self-renewal capacity. The DSCs are phenotypically similar to bone marrow mesenchymal stem cells (BMSCs) but they are not identical. The DSCs show a faster growth rate under hypoxia than normoxia. DSCs derived from nucleus pulposus (DSCNP) show a stable expression level of hypoxia inducible factor-1 alpha (Hif-1ａ) in response to hypoxia. DSCs derived from annulus fibrosus (DSCAF) are more resistant to apoptosis under hypoxia than DSCNP. More importantly, small leucine-rich proteoglycans (SLRPs) are identified as important DSC niche components. We show that biglycan (bgn) and decorin (dcn) reduce the susceptibility of DSCs to hypoxia-induced apoptosis by promoting the expression of hypoxia inducible factors (HIFs). Our findings suggest that DSCs rely on the unique niche components for survival. In summary, our findings propose the existence of endogenous stem cells in IVD. Further study of the DSCs may provide new insights into the biology of IVD and facilitate the design of new strategies to treat disc degeneration in future. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Degenerative disc disease (DDD) is a medical condition whereby the intervertebral discs (IVD) of the human spine degenerates and may cause pain which significantly affects the quality of one掇 life. Its prevalence has sparked off much research in deciphering its causes and developing new treatments. Recently, attempts to treat this degenerative problem have turned to seeking answers from regenerative medicine. One approach is to deliver mesenchymal stem cells (MSCs) with or without carriers to the nucleus pulposus (NP) in degenerative disc to restore both its structural and functional properties. However, the optimal conditions and signals for inducing MSCs differentiation toward NP-like phenotype have not been identified. This work aimed to develop injectable microspheres with matrix microenvironment mimicking that of native NP tissue for MSCs delivery. Firstly, it was aimed to establish a collagen microencapsulation based 3D culture system for maintenance of the phenotype of nucleus pulposus cells (NPCs) and remodeling of the collagen matrix to one that was similar to the native NP. Secondly, it was aimed to optimize a decellularization protocol for complete removal of the encapsulated NPCs with minimal loss of remodeled extracellular matrix. Thirdly, it was aimed to investigate whether this acellular matrix produced by NPCs was inductive for MSCs discogenic differentiation. Finally, it was aimed to evaluate the efficacy of the MSC-seeded acellular matrix microspheres in a pilot rabbit disc degeneration model. It demonstrated that NPCs maintained their phenotype, survived within the collagen microspheres and produced NP-like ECM such as glycosaminoglycan (GAG) and collagen type II. GAG production of NPCs was found to positively correlate with the dosage of TGF-? within a short period, initial collagen concentration and cell seeding density. An optimized decellularization protocol with 50mM SB-10, 0.6mM SB-16 and 0.14% Triton X-200 was established to completely remove the encapsulated NPCs with partial retention of the GAG-rich matrix. The decellularized microspheres were able to be repopulated with human MSCs (hMSCs) or rabbit MSCs (rMSCs). Within the NPC-derived acellular matrix, the repopulated hMSCs were able to partially exhibit NPC phenotype with upregulated expression of a few NPC markers and NP-like ECM according to histological, biochemical, immunohistological and real-time PCR results. In the pilot in vivo evaluation study, preliminary results showed that intra-discal injection of MSCs reseeded acellular NPC-matrix microspheres maintained a better water content than the control MSC-microspheres without the NPC-derived acellular matrix. This work reconstituted in vitro a NP-like 3D matrix and provided preliminary evidence on discogenic differentiation of MSCs in such a matrix environment. This work laid down the foundation to future development of stem cell-based therapies for DDD. Further studies should focus on deciphering the soluble and insoluble composition of such a NP-like matrix environment and understanding the molecular mechanism of the cell-matrix interactions involved. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

The need for the development of a rigorous analytical model of the lumbar spine to clarify the role of mechanical factors in low-back disorders has long been recognized. In response to this need, a general three dimensional nonlinear finite element program has been developed as part of this work and has been applied to the analysis of a lumbar L(,2-3) joint including the posterior elements. The analysis accounts for both the material and geometric nonlinearities and is based on a representation of the nucleus as an incompressible inviscid fluid and of the annulus as a composite of collagenous fibres embedded in a matrix of ground substance. The facet articulation has been accounted for by treating it as a general moving contact problem. The ligaments have been modelled as a collection of nonlinear axial elements. The geometry of the finite element model is based on in-vitro measurements. / The response of the joint under single compression, single flexion, single extension and also under flexion or extension combined with compression and sagittal shear has been analyzed for both the normal and degenerated states of the nucleus. Validity of the model has then been established by a comparison of those predictions which are also amenable to direct measurements. The states of strain and stress in different components of the lumbar joint have been thoroughly studied under all the foregoing loading conditions. / Those elements of the joint predicted to be vulnerable to mechanical failure or damage under the above types of loading have been identified. These results have been correlated with the lumbar joint injuries reported clinically. Furthermore, some joint injury mechanisms and degeneration processes have been proposed and the supporting clinical evidences have been presented.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Thesis (M.Eng.). / Written for the Dept. of Biomedical Engineering. Title from title page of PDF (viewed 2008/07/29). Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaves 151-192) Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaves 151-192) Also available online.

電針夾脊穴治療腰椎間盤突出症的研究進展 摘要：筆者通過對近10年來關於電針夾脊穴治療腰椎問盤突出症的研究132篇，其中有49篇是對於電針夾脊穴治療腰椎間盤突出症的有效性觀察﹔有67篇論述電針夾脊穴聯合其他治療方法的臨床觀察﹔有16篇為專門討論電針夾脊穴對治療腰間盤突出的機理的探討﹔通過對文獻的整理發現目前研究者的研究主要集中在幾個問題方面，一是電針夾脊穴治療腰椎間盤突出症的有效性觀察，目前電針夾脊穴對於腰椎問盤突出症的鎮痛效應經筆者整理，各文獻治療組鎮痛的即時起效時間為3.5-4min ，而對照組在12-13.5 min之間。治癒率治療組平均在80-90%之間，對照組在65-90%之間﹔二是電針夾脊穴的方法如選穴、針刺方法及波形、頻率等參數的運用。在筆者所搜集的文獻中，採用疏密波的文獻占48%，採用連續波（疏波）的占52%，波形的應用各有其治療特色。電針頻率色選擇，各研究者通過大量的實驗，得出高頻和低頻的有效結合對腰椎間盤突出症的治療其有較好的效果﹔三是電針夾脊穴聯合其他方法治療腰椎間盤突出症。如電針夾脊穴聯合牽引治療、電針夾脊穴聯合穴位注射治療、電針夾脊穴聯合正骨推拿治療、電針夾脊穴聯合重要薰蒸治療等，臨床上都取得了良好的效果。四是電針夾脊穴治療的作用機制，包括圍繞中醫理論指導下的機制與現代醫學的生化機制。 關鍵字：電針夾脊穴 腰椎問盤突出 電針參數

Problems with the low back resulting from diseases of the lumbar disc account for much human suffering and medical expense. Through early identification of changes in the disc, Magnetic Resonance Imaging offers a potential method for recognition of those at risk of low back trouble. An understanding of the chemical and structural basis of the MR image will therefore be of great help in understanding the degenerative mechanism itself. With this in mind, NMR studies of human intervertebral discs were performed to extract data that could be correlated with different stages of degeneration. In vitro samples of anulus fibrosus and nucleus pulposus of grades II and IV discs were examined. The Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was used to obtain T₂ relaxation data, which were analysed with a non-negative least squares algorithm and presented as a continuous spectrum of exponentials. An inversion-recovery sequence was used to obtain T₁ data which were analysed with the same algorithm, then presented as a discrete exponential spectrum. The same procedures were used to produce relaxation times from samples of isolated disc collagen and proteoglycan. Also, T₂ relaxation data were obtained with a twelve-echo CPMG imaging sequence from healthy volunteers, and these data analysed with the same procedure used for in vitro data. In vivo and in vitro results were compared and found to agree in terms of the T₂ relaxation values. Most change between grades occurred in the nucleus, where both T₁ and T₂ values decreased from grade II to grade IV. The results of the proteoglycan and collagen studies support the theory that structure, not chemical composition, is responsible for the observed changes in relaxation times. Based on estimates of the percentages of protons in the nucleus due to water, proteoglycan and collagen, tentative assignments were made to the components of the T₂ spectra for grades II and IV nucleus, and these were supported by the results of all parts of the study. / Science, Faculty of / Physics and Astronomy, Department of / Graduate