Preliminary Study Of The Correlation Between SOX9and Human Cervical Intervertebral Disc Degeneration

【Background】Cervical intervertebral disc degeneration(CIDD), the prerequisite andbasis for a series of cervical degenerative disease, plays a crucial role in the pathogenesis ofcervical spondlosis. Its etiology and pathogenesis, however, remain unclear. Recently, IDDhas been shown to be influenced by specific genetic risk factors. Genetic abnormalities ofthe extracellular matrix (ECM) are implicated in disc degeneration. Phenotypes oftransgenic mice and human mutations underscore the candidacy of ECM genes assusceptibility genes for intervertebral disc degeneration (IDD). Several researchers havereported the association of ECM protein genes, including genes for typeⅡcollagen andaggrecan with IDD. Type Ⅱ collagen is important for cartilage collagen formation and fororganization of the extracellular matrix. It was known that SOX9[SRY(sex determiningregion Y)-box9, SOX9] is a member of the SOX family of transcription factors andregulate both chondrogenesis and sex determination. SOX9is a key component of thecartilage extracellular matrix; thus, variations in this gene may affect the pathogenesis ofcartilage-related diseases such as embryonic development dysplasia; and it plays animportant role in the colleagen type Ⅱ synthetic process. In order to illustrate theinvolvement of SOX9and COL2A1(Collagen type Ⅱalpha1, COL2A1) in the discdegeneration, the degenerative NP were collected from cervical spondylotic patients whowere received anterior cervical decompression fusion and internal fixation, pathological,immunohistochemical, fluorescence quantitative reverse transcription polymerase chainreaction (FQ-PCR) and western-blot methods were used to observe the pathologicalchanges of nucleus pulposus with the increasing degeneration and the location of them inthe nucleus pulposus cells, to detect their expression in degenerative nucleus pulposus ofhuman.【Objective】The aim of this study is to observe the pathological changes of nucleuspulposus with the increasing degeneration and the location of SOX9and COL2A1in thenucleus pulposus cells, to detect their expression in degenerative nucleus pulposus ofhuman, elucidate the relationship between SOX9and COL2A1in intervertebral disc cells.Here, we present evidence that SOX9and COL2A1, one of the type XI collagen genes,contribute to the genetic risk of CIDD in Chinese.【Methods】36cases of NP tissue and the preoperative MRI (T2-weighted midsagittalimages) of patients, recruited from february2010to may2011in the Department of Orthopedic Surgery at the Changhai Hospital of Second Military Medical University,whomade surgery for cervical spondylosis or cervical trauma were obtained. All the subjectsgave informed consent before the study. This study was approved by the Ethics Committeesof the Second Military Medical University and the participating clinical institutes.Thedegrees of degenerative discs were assessed by Miyazaki’s grading system for cervicalintervertebral disc degeneration. Pathological changes of NP tissue were observed underlight microscope in different CIDD levels through HE staining. The location and expression(negative, weakly positive, strongly positive) of SOX9and COL2A1in NP tissue wereobserved by immunohistochemical. The changes of SOX9and COL2A1mRNA andprotein levels were detected by FQ-PCR and Western blot analysis in each. The relationshipbetween the levels of SOX9, COL2A1expression and the degrees of MRI degenerationwere analyzed.【Results】In this study, with the increasing degrees of discs degeneration, the collagenfibers were irregularly arranged within the NP, fiber is thickening, aggregating into bolt,progressing into fibrosis. SOX9and COL2A1both are present in intervertebral disc, SOX9located in nucleus, COL2A1located in ECM. Statistical differences of positive intensitywere conspicuous during every degenerated degree’s group (P﹤0.05). SOX9, COL2A1mRNA and protein expression rates were significantly decreased in disc cells as well asdegenerating severity.【Conclusions】With the degeneration aggravating, the NP tissue is gradually replaced byfibrous tissue, tending to be fibrosis. SOX9, COL2A1mRNA and protein expression rateswere significantly decreased in disc cells as well as degenerating severity. Theseobservations indicate that SOX9and COL2A1are critical for CIDD metabolism and thattheir decrease is related to cervical spondilosis.