kondroblastien

Kondroblasten, known in English as chondroblasts, are immature cartilage-forming cells derived from mesenchymal stem cells. They reside in developing cartilage and in the perichondrium that surrounds cartilage templates. Their main role is to synthesize and secrete the cartilaginous extracellular matrix, rich in collagen type II and proteoglycans, which gives cartilage its unique resilience and load-bearing properties.

During chondrogenesis, kondroblasten proliferate and produce matrix to expand the cartilage template. As the surrounding matrix accumulates, these cells become embedded in lacunae and mature into chondrocytes. In endochondral ossification, the cartilage laid down by kondroblasten acts as a temporary scaffold that is later replaced by bone, a process essential for the formation of most long bones and the skeletal axis.

In growing individuals, kondroblasten are active at sites of longitudinal growth, such as the epiphyseal (growth) plates, contributing to bone lengthening by forming organized columns of cells that differentiate into chondrocytes. In mature cartilage, their activity diminishes, and maintenance is carried out primarily by resident chondrocytes within lacunae, with limited replenishment from progenitor cells in the perichondrium under certain conditions.

Regulation of kondroblast activity involves a network of transcription factors and signaling pathways, including Sox9, TGF-β, BMPs, FGFs, PTHrP, and Indian hedgehog, as well as mechanical cues from joint loading. Disruptions in chondrogenic activity can impact cartilage formation, growth, and repair.