Metabolism in Vitro of Cartilage Proteoglycans in Rat (Pre)chondrocytes from Different Embryonic Regions

Abstract

Diabetes in the mother may cause disturbances in the chondrocyte development in the embryo. A rat model was used to investigate whether this was reflected in the production of proteoglycans by cells from two embryonic regions. One of these regions is resistant (limb bud) and the other susceptible (mandibular arch) to malformation in diabetic pregnancy.

Chondroitin sulphate proteoglycans from cultures of day-12 rat embryo limb bud and mandibular arch chondrocytes were extracted with guanidine-HCI and analyzed by gel chromatography after in vitro ³⁵S-sulphate-labeling. Two sizes of proteoglycans (K_av 0.26 and 0.66 on CL-2B Sepharose) were found in both types of chondrocytes and in all media. The polysaccharide chain length was the same (Kav 0.36 on CL-6B Sepharose) for both proteoglycans.

Elevated levels of D-glucose or β-hydroxybutyric acid had no effect on either proteoglycan size or proportion, nor on polysaccharide chain length. However, there were differences (in all culture conditions) between limb bud and mandibular arch cultures in that the larger proteoglycan accounted for 80 % of total radioactivity in the limb bud cultures, 53 % in the mandibular arch cultures, and only 25–29 % in the media from both types of cultures. Furthermore, different ratios between radioactive proteoglycans in medium and matrix suggested markedly different efficiencies for matrix formation in the two cell types. These findings indicate differences in the metabolism of the proteoglycans in these two cell types which may be related to the induction of mandibular malformation in diabetic pregnancy.