Gene expression of collagen types IX and X in the lumbar disc

Objective:To study gene expression of collagen types IX and X in human lumbar intervertebral discs during aging and degeneratio n and to explore the role of collagen types IX and X in disc degeneration. Methods:Fetal, adult and pathologic specimens were subjected t o in situ hybridization with cDNA probes to investigate mRNA-expressions of typ es IX and X collagen gene. Results:In fetal intervertebral discs, positive mRNA hybridiza tion signals of type IX collagen were concentrated in the nucleus pulposus and t he inner layer of anulus fibrosus. Interstitial matrix of the nucleus pulposus a lso showed positive type X collagen staining. Positive mRNA hybridization signal s of types IX and X were not detected in the middle and outer layers of anulus f ibrosus. In adult specimens, expression of type IX collagen mRNA was markedly de creased. No hybridization signals of type X collagen was observed. As for pathol ogical specimens, there was no gene expression of type IX collagen. In severe de generated discs from adults, there were focal positive expressions of type X col lagen. Conclusions:Obvious changes of collagen gene expression occur with aging. Expression of type IX collagen decreases in adult and pathological d iscs. Results of type X collagen expression suggest that type X collagen is expr essed only in older adult and senile discs (i.e., when disc degeneration has alr eady reached a terminal stage), indicating the terminal stage of degeneration.