Early molecular events during in vitro chondrogenesis

Cartilaginous tissues are found in many parts of the body, and as three different types: elastic, hyaline, and fibrocartilage. Elastic cartilage is found in the external ear, the auditory tube, and the epiglottis; fibrocartilage is found mainly in the intervertebral discs and in the menisci; and hyaline cartilage is found covering the articular surfaces of synovial joints. The functional difference between these tissues is determined by the composition of their extracellular matrix (ECM). Human adult mesenchymal stromal cells (MSCs) may resemble the mesenchymal cells from which cartilage and bone are formed during embryogenesis. Developmental chondrogenesis has been carefully studied and well reviewed, based mostly on studies in rodents and humans with developmental disorders of cartilage and bone. Recently, data were published based on studies of human fetal tissues. This chapter reviews current knowledge about the early molecular changes observed during in vitro chondrogenesis and then compares this with in vivo chondrogenesis.