Dimensional growth and extracellular matrix accumulation by neonatal rat mandibular condyles in long‐term culture

Abstract

Mandibular condyles in organ culture commonly have been used as a model system for examination of the factors that influence skeletal growth and development. The work reported here complements previously published histological studies by providing quantitative temporal information on growth and matrix accumulation. Condyles maintained for as long as 5 weeks in serum-free and 1% serum-supplemented culture media were found to remain viable and metabolically active as demonstrated by continued dimensional growth as well as cell and matrix accumulation. Growth occurred by a combination of cell proliferation, matrix synthesis and accumulation, and cell hypertrophy (with the latter two mechanisms dominating). Increases in tissue volume correlated directly with increased glycosaminoglycan content; both increased 7-fold over 5 weeks. In comparison with serum-free culture, after 35 days in medium containing 1% serum, glycosaminoglycan content was 24% lower and collagen content was 36% higher, whereas dry weight, condyle length, and DNA content were not significantly different; in addition, histological observation suggested that, for samples cultured with serum, chondrogenic phenotype had been lost from some regions. The temporal behavior for all growth parameters exhibited a transient phase 1-2 weeks in duration followed by a steady-state period in which dimensions and tissue constituents or content increased at a constant or near constant rate. Comparison of the rates of incorporation of [35S]sulfate with glycosaminoglycan content in serum-free cultures suggests that the loss of glycosaminoglycan occurs only initially or is negligible; therefore, under these baseline conditions, cartilage glycosaminoglycan content reflects the biosynthetic rate. The high degree of reproducibility seen during steady-state growth suggests that these data provide reliable baseline information and further supports the notion that this model system is useful for investigation of the effects of specific physical factors on in vitro growth and development.

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

“…In the case of the first phenotype, incubation with 20% FBS resulted in expansive cartilage growth ( Figure 7B) characterized by a marked increase in tissue thickness and wet weight ( Figures 1A and B) and in the content of GAG and collagen ( Figures 2B and C). The result was a reduction in the concentrations of GAG, collagen, and Pyr (Figures 2B-D) and a concomitant diminution in tensile mechanical integrity (Figures 5 and 6), similar to previous findings on growth of immature cartilage in serum-supplemented medium (19)(20)(21). These findings suggest that a free-swelling, serum-supplemented culture environment induces remodeling and reorganization of the tissue matrix that facilitates a relatively loose and weak collagen network and allows tissue expansion.…”

“…In contrast to this type of in vivo growth and maturation, growth of cartilage explants in vitro in serum-supplemented medium results in a net deposition of proteoglycan that is greater than that of collagen, along with a decrease in mechanical integrity. For explants of immature cartilage, incubation in serum-supplemented medium results in an increase of tissue volume, maintenance of proteoglycan concentration, and a decrease in the concentrations of collagen and Pyr crosslinks (19)(20)(21). These changes in composition are associated with a decrease in tensile modulus and strength (21).…”

Investigations into Growth and Differentiation in the Cartilage of the Condylar Process in the Domestic Pig

“…Die Anwendung des histomorphometrisch-stereologischen Untersuchungsverfahrens stellt somit eine Vereinfachung dar. Nach Bosshardt-Luehrs & Luder [2] Similar results were recorded in studies of rats [3,17,18]. It was shown that, with a high growth rate (up to day 45 postpartum in the rat), cell volume increase and matrix synthesis contribute to growth in a ratio of 2 : 1.…”

Thyroid hormone-induced chondrocyte terminal differentiation in rat femur organ culture

“…Several investigations have demonstrated that cartilage increases in weight and size in serum-free medium (Cole et al 1992;Burch and Lebovitz 1982;Garcia and Gray 1995;Shurtz-Swirski et al 1989). The absence of the elongation of the diaphysis in our system may be a consequence of the composition of the culture medium.…”

“…In the rat mandibular condyle organ culture, the cartilage enlarges dramatically with time without b-glycerophosphate in culture, whereas the size of the bony portion remains the same (Garcia and Gray 1995).…”