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Optimizing a Novel, Serum‐Free, Three‐Dimensional Culture System of Primary Human Osteoarthritic Chondrocytes: A Clinically Relevant Platform to Test and Develop Osteoarthritis Therapeutics

Osteoarthritis (OA), a progressive and degenerative disease, affects millions of aging adults and results in the loss of cartilage. In healthy joints, articular cartilage provides a smooth and cushioned surface that allows bones to glide over each other with little friction. However, when OA begins to develop, degradation of the cartilage extracellular matrix begins to outweigh its synthesis. Production of growth factors, cytokines, and matrix‐degrading enzymes increases. Development of OA therapeutics is the gold standard in orthopedic medicine, but the complexity of the joint makes it a difficult system to manipulate. In this study, we optimize our novel, serum‐free, three‐dimensional culture system for human osteoarthritic articular chondrocytes (HOACs) obtained from patients with end‐stage osteoarthritis who have undergone a total knee arthroplasty. We altered the parameters of culture size, tissue harvest sites and the number of cultures pooled to determine whether clinically‐relevant endpoints are within measurable ranges. In previous studies, sides of greatest and least pathology, as determined from gross examination of the femoral condyles and tibial plateau, were separated and cells were isolated and plated within serum‐free, three‐dimensional alginate cultures on 35 mm plates at a plating density of 2.5×106 cells/milliliter. In this study, we combine both sides of the joint tissue (greatest and least pathology) together to increase the number of cells and cultures obtained from each patient. In addition, we scaled down the size of the cultures to 22 mm plates at a plating density of 1.8×106 cells/milliliter. The scaled‐down, serum‐free, three‐dimensional alginate cultures were maintained for five days, media fractions collected on the second and fifth day of the culture and the alginate‐associated matrix collected at termination of the cultures on day five. Intact and degraded collagens were measured by immunoassay. Both collagens type I and type II, intact and degraded, were detectable within the scaled‐down culture system. Pooling three cultures together provided adequate measurable material of the clinically‐relevant endpoints. Collagen I intact and degraded values were lower than collagen II intact and degraded regardless of the number of cultures pooled (n= 2, 3 or 4). In summary, our optimization techniques have provided more cultures per patient thus enabling measurement of clinically‐relevant endpoints of OA and a screening system to test potential OA therapeutics.