Giordano, B. D. | bioRxiv Science

bioRxiv2022

Whole-Genome RNA Sequencing of Femoral Head Impingement Cartilage Identifies FGF18 As A Biomarker in Hip Osteoarthritis Progression

IntroductionThe natural history of Femoroacetabular Impingement (FAI) has been clinically associated with the development of hip osteoarthritis (OA); however, the pathobiological mechanisms underlying the transition from focal impingement to global joint degeneration remain unclear. The goal of the study was to investigate differences in transcriptomic profiles of the cartilage from FAI and hip OA patients using whole-genome RNA sequencing. MethodsThirty-seven patients were included in the study with 20 diagnosed with FAI undergoing arthroscopic treatment and 15 diagnosed with hip OA undergoing total hip arthroplasty (THA). Cartilage samples were obtained intraoperatively over the femoral head-neck junction for both FAI and OA cohorts. Whole-genome RNA sequencing was performed on 10 gender-matched patients in the FAI and OA cohorts with the remaining samples used for histopathologic analysis using the Osteoarthritis Research Society International (OARSI) grading system and qRT-PCR validation. Target validation was further confirmed with immunohistochemical staining for FGF18 on FAI and OA cartilage samples. ResultsWe identified a total of 3,531 Differentially Expressed Genes (DEGs) between the FAI and OA cohorts with multiple targets for genes implicated in canonical OA pathways. qRT-PCR validation confirmed increased expression of FGF18 and WNT16 in the FAI samples, while there was increased expression of MMP13 and ADAMTS4 in the OA samples. Expression levels of FGF18 and WNT16 were also higher in FAI samples with mild cartilage damage (OARSI grades 1-2) compared to FAI samples with severe cartilage damage or OA cartilage (OARSI grade 4-6). Immunohistochemical evaluation identified increased FGF18 staining in OARSI grade 1-2 FAI samples compared to OARSI grade 5-6 FAI and OA samples. ConclusionsRNA sequencing of cartilage of FAI and hip OA patients identified a negative association of FGF18 expression levels with cartilage damage severity, suggesting that FGF18 may be used as a marker for hip OA progression. Future evaluation of FGF18 signaling as well as other markers in early OA may yield further insight into disease prevention and treatment.

bioinformatics↗

bioRxiv2022

A Murine Model of Abductor Insufficiency Accelerates the Development of Hip Osteoarthritis

Osteoarthritis (OA) of the hip is a common and debilitating painful joint disease. A growing body of evidence suggests that there may be an association between periarticular myotendinous pathology and the development of hip OA. Thus, we hypothesized that a murine model of hip OA could be achieved through selective injury of the abductor complex around the hip. C57BL6/J mice were randomized to sham surgery or abductor injury, in which the myotendinous insertion at the third trochanter and greater trochanter were surgically detached. Mice were allowed free, active movement until sacrifice at either 3 weeks or 20 weeks post-injury. Histologic analyses and immunohistochemical staining (IHC) of the femoral head articular cartilage were performed, along with CT analysis to assess subchondral bone remodeling. We observed that mice receiving abductor injury exhibited significant OA severity with loss of Type II Collagen staining compared to sham control mice at 20 weeks post-surgery, comparable MMPI13 expression was observed between injury and sham groups. No significant differences in subchondral bone were found on CT after 20 weeks following injury. Our study suggests a link between abductor dysfunction and the development of hip OA, which are common pathomorphologies encountered in routine orthopaedic clinical practice. Further, this novel animal model may provide a valuable tool for future investigations into the pathogenesis and treatment of hip OA.

pathology↗