Role of pericellular matrix in development of a mechanically functional neocartilage

Abstract

The role of the chondrocyte pericellular matrix (PCM) was examined in a three-dimensional chondrocyte culture system to determine whether retention of the native pericellular matrix could stimulate collagen and proteoglycan accumulation and also promote the formation of a mechanically functional hyaline-like neocartilage. Porcine chondrocytes and chondrons, consisting of the chondrocyte with its intact pericellular matrix, were maintained in pellet culture for up to 12 weeks. Sulfated glycosaminoclycans and type II collagen were measured biochemically. Immunocytochemistry was used to examine collagen localization as well as cell distribution within the pellets. In addition, the equilibrium compressive moduli of developing pellets were measured to determine whether matrix deposition contributed to the mechanical stiffness of the cartilage constructs. Pellets increased in size and weight over a 6-week period without apparent cell proliferation. Although chondrocytes quickly rebuilt a PCM rich in type VI collagen, chondron pellets accumulated significantly more proteoglycan and type II collagen than did chondrocyte pellets, indicating a greater positive effect of the native PCM. After 5 weeks in chondron pellets, matrix remodeling was evident by microscopy. Cells that had been uniformly distributed throughout the pellets began to cluster between large areas of interterritorial matrix rich in type II collagen. After 12 weeks, clusters were stacked in columns. A rapid increase in compressive strength was observed between 1 and 3 weeks in culture for both chondron and chondrocyte pellets and, by 6 weeks, both had achieved 25% of the equilibrium compressive stiffness of cartilage explants. Retention of the in vivo PCM during chondrocyte isolation promotes the formation of a mechanically functional neocartilage construct, suitable for modeling the responses of articular cartilage to chemical stimuli or mechanical compression.

Effect of sterilisation by gamma irradiation on the ability of polycaprolactone (PCL) to act as a scaffold material

“…Growth medium (500 μL of Opti-MEM supplemented with 2% foetal bovine serum, 2.7 mM CaCl 2 , 25 μg/mL L-ascorbate-2-monophosphate; Sigma-Aldrich Poole, Dorset, UK) with a penicillin/streptomycin mix (Invitrogen, Paisley, UK) was used, as described in Graff et al (2002) [13]. A sample of the medium (3 ml) was added to each of the wells the cells were cultured in incubator at 37°C with 5% CO 2 for 10 days.…”

Hyaluronic Acid-Binding Scaffold for Articular Cartilage Repair

“…27 Previous studies have suggested that pericellular GAG molecules can aid in the organization and deposition of Type II collagen during chondrogenesis. 28 This may explain the marked increase in Type II collagen deposition by 6 weeks compared to control materials. The cell-secreted proteoglycans, bound to the HA-interactive scaffold through their HA cores, may aid in the deposition and organization of Type II collagen.…”

Micromechanical properties of chondrocytes and chondrons: relevance to articular cartilage tissue engineering

“…In cases of severe articular cartilage pathology, tissue replacement may become necessary. In the laboratory, it is now possible to engineer cartilage of clinically relevant dimensions and properties [Graff et al 2003;Hu and Athanasiou 2006;Kang et al 2006], and this may have profound implications for orthopedics in the near future.…”

“…In contrast, scaffoldless procedures have also been employed to grow articular cartilage outside the body with the goal of then transplanting the neotissue into the defective region. Pellet culture [Graff et al 2003] and aggregate culture [Horton et al 1987;Furukawa et al 2003] techniques have been implemented to grow articular cartilage constructs and tested under various mechanical conditions. Another scaffoldless approach, known as the self-assembling process, has recently been validated by Hu and Athanasiou [Hu and Athanasiou 2006] to produce cartilage tissue constructs with biomechanical and biochemical properties nearing those of native tissue.…”

“…Considering these biochemical and biomechanical functional roles, it is no surprise that the PCM has received special attention in tissue engineering of articular cartilage and research toward maintaining a healthy, well-developed ECM [Larson et al 2002;Kelly et al 2004;Graff et al 2003;Fraser et al 2006].…”