MSC populations for cartilage regeneration

Adult mesenchymal stem cells (MSCs) have an excellent capacity to repair tissues since they can proliferate and differentiate to form various tissues, cartilage included. Moreover, MSCs are potentially accessible in high quantities with low donor site morbidity and reasonable cartilage-forming capacity. In 1998, Johnstone et al. (Exp Cell Res 238(1):265-272) were the first that proposed an effective protocol to chondrogenically differentiate MSCs by using transforming growth factor-ß (TGF-ß), now used by many groups in the world and since then hardly changed. However, MSCs are a heterogeneous population, and the amount and type of cartilage formed are strongly influenced by intra- and inter-donor variation. In this chapter, we mainly focused on surface markers and their modulation by growth factors. We aim to first clarify the characteristics and the embryonic origin of cartilage progenitor cells (chondroprogenitor), then to summarize the characteristics and the contribution to cartilage repair by MSCs from different origins both in vivo and in vitro, and finally, to show a few examples of promoting articular cartilage phenotype by growth factor administration, in relation to the modulation of surface marker expression. With the exception of the next section focused on embryology, our interest was posed specifically on MSCs from human origin.