Human fetal and adult bone marrow-derived mesenchymal stem cells use different signaling pathways for the initiation of chondrogenesis.

Cartilage injuries and osteoarthritis are leading causes of disability in developed countries. The regeneration of damaged articular cartilage using cell transplantation or tissue engineering holds much promise but requires the identification of an appropriate cell source with a high proliferative propensity and consistent chondrogenic capacity. Human fetal mesenchymal stem cells (MSCs) have been isolated from a range of perinatal tissues, including first-trimester bone marrow, and have demonstrated enhanced expansion and differentiation potential. However, their ability to form mature chondrocytes for use in cartilage tissue engineering has not been clearly established. Here, we compare the chondrogenic potential of human MSCs isolated from fetal and adult bone marrow and show distinct differences in their responsiveness to specific growth factors. Transforming growth factor beta 3 (TGFβ3) induced chondrogenesis in adult but not fetal MSCs. In contrast, bone morphogenetic protein 2 (BMP2) induced chondrogenesis in fetal but not adult MSCs. When fetal MSCs co-stimulated with BMP2 and TGFβ3 were used for cartilage tissue engineering, they generated tissue with type II collagen and proteoglycan content comparable to adult MSCs treated with TGFβ3 alone. Investigation of the TGFβ/BMP signaling pathway showed that TGFβ3 induced phosphorylation of SMAD3 in adult but not fetal MSCs. These findings demonstrate that the initiation of chondrogenesis is modulated by distinct signaling mechanisms in fetal and adult MSCs. This study establishes the feasibility of using fetal MSCs in cartilage repair applications and proposes their potential as an in vitro system for modeling chondrogenic differentiation and skeletal development studies.