Experimental observation of human bone marrow mesenchymal stem cell transplantation into rabbit intervertebral discs

Gene Therapy in Orthopaedics: Progress and Challenges in Pre-Clinical Development and Translation

In orthopaedics, gene-based treatment approaches are being investigated for an array of common -yet medically challenging- pathologic conditions of the skeletal connective tissues and structures (bone, cartilage, ligament, tendon, joints, intervertebral discs etc.). As the skeletal system protects the vital organs and provides weight-bearing structural support, the various tissues are principally composed of dense extracellular matrix (ECM), often with minimal cellularity and vasculature. Due to their functional roles, composition, and distribution throughout the body the skeletal tissues are prone to traumatic injury, and/or structural failure from chronic inflammation and matrix degradation. Due to a mixture of environment and endogenous factors repair processes are often slow and fail to restore the native quality of the ECM and its function. In other cases, large-scale lesions from severe trauma or tumor surgery, exceed the body’s healing and regenerative capacity. Although a wide range of exogenous gene products (proteins and RNAs) have the potential to enhance tissue repair/regeneration and inhibit degenerative disease their clinical use is hindered by the absence of practical methods for safe, effective delivery. Cumulatively, a large body of evidence demonstrates the capacity to transfer coding sequences for biologic agents to cells in the skeletal tissues to achieve prolonged delivery at functional levels to augment local repair or inhibit pathologic processes. With an eye toward clinical translation, we discuss the research progress in the primary injury and disease targets in orthopaedic gene therapy. Technical considerations important to the exploration and pre-clinical development are presented, with an emphasis on vector technologies and delivery strategies whose capacity to generate and sustain functional transgene expression in vivo is well-established.

Effects of AAV2-mediated co-transfection of CTGF and TIMP1 genes on degenerative lumbar intervertebral discs in rhesus monkeys in vivo

OBJECTIVE

This study aims to investigate the effects of co-transfection of the genes for connective tissue growth factor (CTGF) and tissue inhibitor of metalloproteinase-1 (TIMP1) mediated by adeno-associated virus 2 (AAV2) on degenerative lumbar intervertebral discs in a primate model.

METHODS

Twelve 4-7 year-old rhesus monkeys weighing 4.5-7.0 kg were utilized. CTGF and TIMP1 genes carried by AAV2 were injected into the degenerative lumbar intervertebral discs. Cytokine expression and biological effects were determined using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and ³⁵S-sulfate incorporation assays. A rhesus monkey model of intervertebral disc degeneration was successfully established.

RESULTS

At post-transfection, CTGF mRNA expression was higher in the transfection group than in the control group (P < 0.05). Furthermore, TIMP1 mRNA expression in the transfection group was several times the levels observed in the control group (P < 0.05). Moreover, type-II collagen mRNA expression was higher in the transfection group than in the control group (P < 0.05). In addition, higher aggrecan mRNA expression and synthesis were observed in the transfection group, compared to that in the control group (P < 0.05).

CONCLUSION

The stable expression of CTGF and TIMP1 genes in vivo promoted the synthesis of aggrecan and type II collagen in the nucleus pulposus in the rhesus monkey model of intervertebral disc degeneration, which has a potential for intervertebral disc regeneration.