Mechanisms of cartilage growth: Modulation of balance between proteoglycan and collagen in vitro using chondroitinase ABC

Abstract

Objective. To examine the cartilage growthassociated effects of a disruption in the balance between the swelling pressure of glycosaminoglycans (GAGs) and the restraining function of the collagen network, by diminishing GAG content prior to culture using enzymatic treatment with chondroitinase ABC.Methods. Immature bovine articular cartilage explants from the superficial and middle layers were analyzed immediately or after incubation in serumsupplemented medium for 13 days. Other explants were treated with chondroitinase ABC to deplete tissue GAG and also either analyzed immediately or after incubation in serum-supplemented medium for 13 days. Treatment-and incubation-associated variations in tissue volume, contents of proteoglycan and collagen network components, and tensile mechanical properties were assessed.

Bioengineering Cartilage Growth, Maturation, and Form

“…The bulk of the immature cartilage is often described as having a fairly isotropic structure with chondrocytes arranged at random (25,26). However, cell density may decrease with depth, particularly near the articular surface (25), whereas GAG and collagen concentrations and tensile and compressive moduli may increase (27,28). On the other hand, mature articular cartilage possesses distinct superficial, middle, and deep zones.…”

“…3). It has been hypothesized that changes in cartilage size and in maturation (as quantified by the tensile properties) could result by altering the balance of proteoglycan and collagen metabolism (27,41,42). Culturing immature cartilage explants with fetal bovine serum (FBS), insulin-like growth factors-1, or bone morphogenetic protein-7 (BMP-7) resulted in an expansive growth phenotype characterized by large increases in size, stimulation of proteoglycan in excess of collagen, and decreases in tensile stiffness and strength (42).…”

“…Alternatively, culture with TGF-␤1 promoted cartilage homeostasis with little change in size, composition, or mechanical properties (42). The identification of biochemical stimuli which promote maturation in immature cartilage explants has been elusive, though depletion of proteoglycans by chondroitinase-ABC treatment before culture resulted in increased tensile stiffness (27). These distinct treatments to promote expansion, homeostasis, or maturation may find use in tissue engineering cartilage of specific size or maturity.…”

Articular cartilage tensile integrity: Modulation by matrix depletion is maturation-dependent

“…An indirect, but dramatic contribution of the proteoglycan component to the tensile properties or cartilage has also been demonstrated. Chondroitinase ABC (C-ABC) treatment, which specifically depolymerizes chondroitin and dermatan sulfate GAG chains [10], resulted in a reduction of the initial slope of the stress-strain curve [11,12] and an increase in the overall tensile modulus of cartilage [13][14][15] and tensile strength in tendon [16]. In addition, collagen to proteoglycan ratio correlated strongly with equilibrium tensile modulus of cartilage [17].…”

The effect of tissue-engineered cartilage biomechanical and biochemical properties on its post-implantation mechanical behavior

“…Indeed, previous experimental studies showed significant influences of the synthesis rate of PGs and collagen on mechanical properties of the cartilage explants (Asanbaeva et al 2007) and TE constructs (Bian et al 2009). Effects of such phenomena on post-implantation mechanical performance of TE implants have not been reported so far, and it is unknown how different synthesis rate of the PGs and collagen during TE process may change mechanical conditions in TE implants after implantation.…”