Changes in integrin expression during chondrogenesis in vitro: An immunomorphological study

Abstract

Integrins are receptors composed of ligand-specific α-chains and cell type-specific β-chains which are involved in cell-cell and cell-matrix interactions. The distribution of α1- and α3-integrins as well as collagen Types I and II, was investigated by immunofluorescence and immunoelectron microscopy during chondrogenesis in organ culture after various culture periods. Mesenchymal cells from limb buds of Day 12 mouse embryos were grown at high density. Within the first 2 days of the culture period, only α1- integrin could be detected. Formation of cartilage-specific matrix on Day 3 was accompanied by the occurrence of α3-integrin. On Day 7, α3 was present only in cartilage nodules, whereas α1 was strongly expressed in the perichondrium and was more or less homogeneously distributed in the surrounding mesenchyme. On Day 14, α1-integrin was again detectable in cartilage. We suggest that the change in collagen formation from Type 1 to Type II during chondrogenesis is accompanied by a change in integrin expression from α1 to α3. Conversely, dedifferentiation of chondrocytes in aging cartilage is accompanied by the occurrence of collagen Type I and α1- integrin. Therefore, a strict correlation between the collagen type synthesized by the cells and the appropriate receptor presented by the cells is suggested.