Background/Purpose: Osteoarthritis (OA) is a disease that is characterized by the breakdown or loss of articular cartilage due to biomechanical and biochemical changes in the joints of the knees, hips and hands. Chondrocytes, the cells present in articular cartilage, have traditionally been thought to be exclusively responsible for inducing the calcification observed in OA, and therefore are believed to play an essential role in the development of OA pathogenesis. However, recent reports suggest that meniscal degeneration and calcification are correlated with articular cartilage degeneration in the knee of OA patients. Joint calcification correlates greatly with OA, as 70% of OA patients show an increase in calcium crystal deposition compared to non-OA patients. There are two main types of crystals present in advanced OA patients: calcium pyrophosphate dehydrate (CPPD) and basic calcium phosphate (BCP). However, it is still unclear which tissue (cartilage or meniscus) produce these calcium crystals. The role of meniscal cells in calcification is poorly understood at present, thus the purpose of this study is to determine the role of meniscal cells in the pathogenesis of osteoarthritis (OA) in the knee. Our central hypothesis states that meniscal cells play an unrecognized role in the development of OA in part by inducing calcification in the meniscus.

Methods: Tissue was collected from menisci and articular cartilage obtained from OA patients undergoing joint replacement surgery. Calcium Crystals were detected using alizarin red and Eosin Y staining. Cell were isolated from OA menisci and articular cartilage tissue. The cells were treated with and without extracellular ATP (a calcification inducer) and calcification medium for seven days in a monolayer culture. Alizarin Red staining was used to detect calcification present in a monolayer. Images were obtained using Sony Imaging software with an inverted scope and alizarin red was quantified measuring HCL absorbance at 405 wavelength using a microplate reader. ⁴⁵Calcium Assay was used to quantify calcification induced by chondrocytes and meniscal cells in the presence and absence of extracellular ATP. The cells were cultured in a monolayer environment for 5 days. ⁴⁵Calcium was measured as counts per minute using a liquid scintillation counter.

Results: Our data, using a ⁴⁵Calcium assay and alizarin red staining, suggest that meniscal cells, similar to chondrocytes, induce the formation of calcium crystals in the presence of extracellular ATP and calcification medium, with meniscal cells inducing calcification at a slightly higher rate than chondrocytes. Additionally, OA patients have been shown to contain many types of calcium crystals in the knee cartilage, with BCP and CPPD crystals being the most abundant. Both of which have been implicated in the development and progression of knee OA. Our preliminary data shows the meniscus of OA patients contains both BCP and CPPD crystals of which about 44% are CPPD crystals.

Conclusion: Our results suggest meniscal cells like chondrocytes induce calcium crystal formation and both BCP and CPPD crystals are present in the meniscus of OA patients.

---

« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-role-of-meniscal-cells-in-osteoarthritis-calcification/