• Yuji Yamamoto, Ken-Ichi Furukawa, Kazumasa Ueyama, Tohru Nakanishi, Masaharu Takigawa, and Seiko Harata.
• Department of Orthopaedic Surgery, Hirosaki University School of Medicine, Hirosaki, Japan.
• Spine. 2002 Sep 1; 27 (17): 1852-7.

Study DesignA biochemical and histochemical study investigating the role of CTGF/Hcs24 in the ossification of the posterior longitudinal ligament (OPLL) was conducted.ObjectiveTo clarify the involvement of CTGF/Hcs24 in ectopic bone formation in OPLL through endochondral ossification using human tissue.Summary Of Background DataPrevious studies have shown that various cytokines are involved in the occurrence or development of ectopic bone formation in OPLL. Recently, the authors cloned an mRNA predominantly expressed in chondrocytes by differential display PCR and found that its gene, hcs24, is identical to that of connective tissue growth factor. It has been shown that CTGF/Hcs24 plays a major role in endochondral ossification.MethodsOssified ligament tissues were taken from seven male OPLL patients during surgery. Immunohistochemical staining was performed using an antibody specific for CTGF/Hcs24. Spinal ligament cells were isolated from five OPLL patients as well as five non-OPLL patients. The cells were incubated with recombinant human CTGF/Hcs24 or TGFbeta. The expression of ALP was analyzed by RT-PCR. For the effects of TGFbeta, the expression of CTGF/Hcs24 mRNA was analyzed.ResultsImmunohistochemical staining showed that chondrocytes in the transitional region from nonossified to ossified ligament were stained with an antibody against CTGF/Hcs24. It was found that CTGF/Hcs24 enhanced the expression ALP mRNA in OPLL cells, whereas the expression remained unchanged in non-OPLL cells. The expression of CTGF/Hcs24 mRNA in OPLL and non-OPLL cell lines was increased by TGFbeta, and there was no significant difference between the two groups. However, TGFbeta and CTGF/Hcs24 enhanced the expression of ALP mRNA only in OPLL cells.ConclusionsAccording to the study results, CTGF/Hcs24 may not only be an important factor in the development of endochondral ossification in OPLL, but may also be responsible for initiating osteogenesis in spinal ligament cells.

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