Regulatory role of human fibrocartilage stem cells in condyle osteochondroma

Objective: Osteochondroma is a common benign skeletal disorder for which different molecular and histological features of long bones have been reported. We investigated cell-of-origin and molecular mechanisms of a rare condylar osteochondroma (CO).

Methods: Human fibrocartilage stem cells (hFCSCs) isolated from CO and normal condyle tissue were used for RNA sequencing, Real-Time PCR, Western Blotting, immunohistology, flowcytometry, as well as for chondrogenic differentiation, proliferation, and Apoptosis detection assays.

Results: HFCSCs were fewer in number with weaker proliferative capacity and higher Apoptosis ratio in the CO group. During the chondrogenic inducing process, hFCSCs from CO were prone to form more mature and hypertrophic cartilage. The result of RNA sequencing of hFCSCs from CO and normal condyle revealed a correlation between the PI3K/Akt signalling pathway and CO. Activated PI3K/Akt signalling might lead to functional changes in hFCSCs by enhancing cell Apoptosis in the developmental process of CO. Increased expression of BCL2-like protein 11 (Bim) in CO tissue also supports this conclusion. Furthermore, the activation of the PI3K/Akt pathway in TMJ of mice induced histological disorder and increased Apoptosis in condylar cartilage.

Conclusion: We conclude that the activation of PI3K/Akt signalling in hFCSCs of CO suggests a new hypothesis for the cell-of-origin of human CO and another possible target to treat it.