Col9a2 gene deletion accelerates the degeneration of intervertebral discs

Huihui Xu; Rui Dong; Qinghe Zeng; Liang Fang; Qinwen Ge; Chenjie Xia; Peng Zhang; Shuaijie Lv; Zhen Zou; Pinger Wang; Ju Li; Hongfeng Ruan; Songfeng Hu; Chengliang Wu; Hongting Jin; Peijian Tong

doi:10.3892/etm.2022.11130

Col9a2 gene deletion accelerates the degeneration of intervertebral discs

Exp Ther Med. 2022 Mar;23(3):207. doi: 10.3892/etm.2022.11130. Epub 2022 Jan 7.

Authors

Huihui Xu^{1

2}, Rui Dong^{1

3}, Qinghe Zeng^{1

2}, Liang Fang^{1

2}, Qinwen Ge^{1

2}, Chenjie Xia^{1

2}, Peng Zhang^{1

2}, Shuaijie Lv^{1

2

3}, Zhen Zou^{1

2}, Pinger Wang^{1

2}, Ju Li^{1

2

3}, Hongfeng Ruan^{1

2}, Songfeng Hu⁴, Chengliang Wu^{1

2}, Hongting Jin^{1

2}, Peijian Tong^{1

2

3}

Affiliations

¹ The First College of Clinical Medicine, Zhejiang Chinese Medical University, Hangzhou, Zhejiang 310053, P.R. China.
² Institute of Orthopaedics and Traumatology of Zhejiang Province, Hangzhou, Zhejiang 310053, P.R. China.
³ Department of Orthopaedic Surgery, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, Zhejiang 310006, P.R. China.
⁴ Department of Orthopaedics and Traumatology, Shaoxing Hospital of Traditional Chinese Medicine, Shaoxing, Zhejiang 312000, P.R. China.

Abstract

As an essential component of the extracellular matrix (ECM) in cartilage, the α2 chain of type IX collagen (Col9a2), has been implicated in human intervertebral disc degeneration (IVDD). However, the precise role of the Col9a2 gene in the pathogenesis of IVDD has remained elusive. In the present study, the spines of Col9a2-deficient (Col9a2^-/-) mice were systematically analyzed and compared with wild-type control mice using micro-CT (µCT), histomorphology, immunofluorescence, immunohistochemistry and reverse transcription-quantitative PCR (RT-qPCR). µCT analysis revealed that endplate (EP) osteochondral remodeling in the Col9a2^-/- group was accompanied by a significant increase in EP porosity. Likewise, histopathological staining at 12 weeks revealed that the Col9a2^-/- mice exhibited a marked early-stage IVDD phenotype, including EP sclerosis, calcification and annulus fibrosus rupture. The immunofluorescence results indicated that Col9a2 was extensively expressed in the IVDs, whereas it was barely detectable in Col9a2^-/- mice. Immunohistochemical and RT-qPCR analyses demonstrated that the expression levels of Col2a1 and Aggrecan in the IVDs of Col9a2^-/- mice were significantly decreased. In addition, the levels of Mmp13, ADAM metallopeptidase with thrombospondin type 1 motif 5, Col10a1 and Runx family transcription factor 2 were significantly elevated. These results suggested that deletion of the Col9a2 gene led to osteochondral remodeling of cartilage EP and suppressed ECM synthesis, accelerating matrix degradation and chondrocyte hypertrophy in the IVD tissue.

Keywords: Col9a2; calcification; endplate; intervertebral disc degeneration; ossification.

Grants and funding

Funding: This research was funded by the Chinese National Natural Science Foundation (grant nos. 81774346, 81873324, 81973869, 81904221 and 81904219), the Traditional Chinese Medical Administration of Zhejiang Province (grant nos. 2021ZZ014, 2018ZA034, 2019ZQ018 and 2018ZZ011), the Health Commission of Zhejiang Province (grant no. 2019RC225) and the Shaoxing Science and Technology Project (grant no. 2018C30114).