Transcriptional Analysis of Articular Cartilage in Knee Osteoarthritis: Relationship with Obesity

Objective: To examine the changes in tibial plateau cartilage in relation to body mass index (BMI) in patients with end-stage osteoarthritis (OA). Design: Knees were obtained from 23 OA patients (3 non-obese, 20 obese) at the time of total knee replacement. RNA prepared from cartilage was probed for differentially expressed (DE) gene transcripts using RNA microarrays and validated via real-time PCR. Differences with regard to age, sex, and between medial and lateral compartments were also queried. Results: Microarrays revealed that numerous transcripts were significantly DE between non-obese and obese patients (1.5-fold) using pooled and separate data from medial and lateral compartments. Correlation analyses showed that 706 transcripts (459 positively, 247 negatively) were significantly correlated with BMI. Among these, HS3ST6, HSD17B12, and FAM26F were positively correlated while STAC3, PRSS21, and EDA were negatively correlated. Differentially correlated transcripts represented important biological processes e.g. cellular metabolic processes, anatomical structure morphogenesis and cellular response to growth factors. Although age and sex had some effect on transcript expression, most intriguing results were observed for comparison between medial and lateral compartments. Transcripts (MMP13, CLEC3A, MATN3, EPYC, SCARNA5, COL2A1) elevated in the medial compartment represented skeletal system development, cartilage development, collagen and proteoglycan metabolism, and extracellular matrix organization. Likewise, transcripts (SELE, CTSS, VSIG4, F13A1, and STEAP4) repressed in medial compartment represented host immune response, cell migration, wound healing, cell proliferation and response to cytokines. PCR data confirmed expression of DE transcripts. Conclusions: This study supports molecular interaction between obesity and OA and implies that BMI is an important determinant of transcript-level changes in cartilage.

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