The fibroblast of radicular cyst facilitate osteoclastogenesis via the autocrine of Fibronectin containing extra domain A.

Objective: To investigate the alternative spliced isoforms of Fibronectin (FN) in the stroma of radicular cysts and analyze the associations between these isoforms and the osteoclastogenic effects of fibroblasts. Methods and materials: The specimens of radicular cysts were stained with immunohistochemistry, and the associations between each FN isoform and clinical parameters were assessed. The fibroblasts isolated from cysts or jaw bone were cultured to induce the Trap + MNCs. In the conditioned medium, the Fibronectin containing extra domain A (EDA + FN) was neutralized by antibody IST‐9, and the EDA exon of fibroblasts was knockout by CRISPR/Cas system, for assessing the osteoclastogenic effects. The mRNA level of FN isoforms and the osteoclastogenesis‐related genes were analyzed by quantitive PCR. Results: EDA + FN staining was positively associated with the size of the lesions (p < 0.05). In contrast with the controls, the ratio of EDA + FN/total FN in the fibroblasts from radicular cysts was significantly higher (p < 0.05), and positively associate with Trap + MNCs counting, it was consistent with increased expression of COX‐2, IL‐6, IL‐17, and the RANKL/OPG (p < 0.05). The Trap + MNCs counting and osteoclastogenesis‐related genes were decreased by IST‐9 blocking and EDA exon knockout in fibroblasts, but the blockage of the interaction between EDA + FN and pre‐osteoclasts exhibited little effects on Trap + MNCs formation. Conclusion: The microenvironment of the fibrous capsule of radicular cysts facilitates the splicing of EDA exon, it endues EDA + FN with autocrine effects on fibroblast itself, and it increases the expression of osteoclastogenesis‐related genes, by which the osteoclastogenesis in radicular cysts could be initiated. [ABSTRACT FROM AUTHOR]