An immunofluorescence study of chondrogenesis in murine mandibular ectomesenchyme

The temporal and spatial distribution of type I collagen, type II collagen, cartilage-specific proteoglycan (CSPG) and fibronectin in mouse mandible is described. CD-1 mouse embryos of 12-, 15-, and 18-day gestation were used, and matrix molecules were localized using indirect immunofluorescence. On day 12, accumulation of type II collagen, CSPG, and fibronectin within regions of condensed mesenchyme was noted. On day 15, intense staining for type II collagen and CSPG occurred. Fibronectin was less brilliant with its greatest concentration near the perichondrium. On day 18, the cartilage matrix was undergoing osseous replacement concurrent with loss of type II collagen and CSPG. Type I collagen was seen in the perichondrium, membranous bone and sub-basement membrane region in specimens of all ages. Synthesis and expression of extracellular matrix molecules reflect patterns of differentiation in mandibular mesenchyme.