To present the morphological changes of classic primary versus rapidly progressive and secondary hip osteoarthritis (HO) and to examine the expression of two pluripotent mesenchymal stem cell-like markers in the synovial membrane. A prospective observational study was conducted in 57 consecutive cases of radiologically confirmed HO in which total hip arthroplasty was performed. Based on the radiological and clinicopathological features, the cases were divided into three categories: classic primary HO (group A; n=16), rapidly destructive HO (group B; n=24), and HO secondary to avascular osteonecrosis of the femoral head (group C; n=17). Immunostains were performed using the markers CD44 and CD105. The cases from group A were mainly characterized by a marked perivascular inflammatory infiltrate and simple synovial hyperplasia. In group B, the papillary type of synovial hyperplasia was found and presence of chondromatosis, ossification, and ectopic follicles with germinal centers in the subsynovial layer was characteristic, whereas marked calcification and/or ossification were seen in group C. Focal expression of the CD105 and CD44 was noted in the hyperplastic synovial cells and subsynovial layer in cases from group A, whereas synovial cells from group B were diffusely positive for both CD44 and CD105. In secondary HO, CD44 marked the inflammatory cells. Mobilization of the CD44/CD105 positive synovial cells seems to play a role in the genesis of HO. The number of the pluripotent mesenchymal stem cell-like cells derived from the hyperplastic synovial cells might be related to the severity of possible immune-mediated rapidly destructive HO.
Contributors SGT performed the interpretation of the histological stains and drafted the article. IJ performed the interpretation of the histological stains, the immunostains and examined the synovial fluid smears. SG designed the research and the paper structure and approved the final variant. AZ analyzed literature data regarding radiological aspects of osteoarthritis. AF performed the histological daily diagnosis and checked the English quality. COR participated in the surgical interventions and managed the clinical data. MT performed the interpretation of the literature data regarding the immunostains. TSP performed the surgical interventions, managed the clinical data and approved the final variant.
Funding This work was partially supported by the University of Medicine and Pharmacy of Tirgu Mures, Romania and Bosintex S.R.L., grant 8645/2015.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Clinical County Hospital of Tirgu-Mures, Romania.
Provenance and peer review Not commissioned; externally peer reviewed.