Young Adult Chondrocytes Proliferate Rapidly and Produce a Cartilaginous Tissue at the Gel-Media Interface in Agarose Cultures

Abstract

Primary chondrocytes cultured in agarose can escape the gel, accumulate at the interface between agarose and the culture medium, and form an outgrowing tissue. These outgrowths can appear as voluminous cartilage-like nodules that have never been previously investigated. In the present study, bovine articular chondrocytes from three age groups (fetal, young adult, aged) were seeded and cultured in agarose to test the hypothesis that hyaline-like cartilage outgrowths develop at the interface by appositional growth, in an age-dependant manner. Macroscopic appearance, cell content, cell division, cytoskeletal morphology, and extracellular matrix (ECM) composition were analyzed. Fetal chondrocytes produced a fibrous interfacial tissue while aged chondrocytes produced ECM-poor cell clusters. In contrast young adult chondrocytes produced large cartilaginous outgrowths, rich in proteoglycan and collagen II, where cells in the central region displayed a chondrocyte morphology. Cell proliferation was confined to the peripheral edge of these outgrowths, where elongated cell morphology, cell-cell contacts, and cell extensions toward the culture medium were seen. Thus these voluminous cartilaginous outgrowths formed in an appositional growth process and only for donor chondrocytes from young adult animals. This system offers an interesting ability to proliferate chondrocytes in a manner that results in a chondrocyte morphology and a cartilaginous ECM in central regions of the outgrowing tissue. It also provides an in vitro model system to study neocartilage appositional growth.

Chondrocyte Morphology in Stiff and Soft Agarose Gels and the Influence of Fetal Calf Serum

“…f). In order to clarify the mechanism of cluster formation, preliminary experiments were performed with BrdU labeling of cultured chondrocytes in both strengths of agarose gels using methods previously described (Tran‐Khanh et al, ). The results indicated a marked difference in BrdU labeling pattern, with the majority of cells cultured in soft gels labeled as BrdU positive but with almost no BrdU positive staining detected amongst chondrocytes cultured in stiff gels (Karim A. unpublished results).…”

Subchondral chitosan/blood implant-guided bone plate resorption and woven bone repair is coupled to hyaline cartilage regeneration from microdrill holes in aged rabbit knees

“…Many patients needing cartilage repair therapy aged 40e65 years old, are considered too young for a joint replacement, and too old to respond well to standard therapies 1,2 . Treatments that work in skeletally immature rabbits (2e6 months old), which have a high spontaneous rate of regeneration compared to rabbits over 8 months old 3e6 , may prove to be ineffective in middle-aged patient knees, which have low remodeling rates, declining mesenchymal stem cell populations, and low intrinsic capacity for chondrocytes to synthesize collagen type II 7 . Rabbits attain skeletal maturity with closed epiphyses at 7 months, but rabbits over 8 months old are needed to analyze osteochondral repair reactions in fully mature epiphyses 8 .…”

The Economics and Regulation of PRP in the Evolving Field of Orthopedic Biologics

“…The limited regenerative capacity of articular cartilage [42,43] and need for non-surgical treatment alternatives [44] have spurred a number of clinical investigations into the efficacy of PRP and other autologous cell therapies for the treatment of osteoarthritis (OA) [45]. A 2013 review by Khoshbin [46].…”