In vitro analysis of integrin expression in stem cells from bone marrow and cord blood during chondrogenic differentiation

Abstract

The use of adult mesenchymal stem cells (MSC) in cartilage tissue engineering has been implemented in the field of regenerative medicine and offers new perspectives in the generation of transplants for reconstructive surgery. The extracellular matrix (ECM) plays a key role in modulating function and phenotype of the embedded cells and contains the integrins as adhesion receptors mediating cell–cell and cell–matrix interactions. In our study, characteristic changes in integrin expression during the course of chondrogenic differentiation of MSC from bone marrow and foetal cord blood were compared. MSC were isolated from bone marrow biopsies and cord blood. During cell culture, chondrogenic differentiation was performed. The expression of integrins and their signalling components were analysed with microarray and immunohistochemistry in freshly isolated MSC and after chondrogenic differentiation. The fibronectin-receptor (integrin a5b1) was expressed by undifferentiated MSC, expression rose during chondrogenic differentiation in both types of MSC. The components of the vitronectin/osteopontin-receptors (avb5) were not expressed by freshly isolated MSC, expression rose with ongoing differentiation. Receptors for collagens (a1b1, a2b1, a3b1) were weakly expressed by undifferentiated MSC and were activated during differentiation. As intracellular signalling components integrin linked kinase (ILK) and CD47 showed increasing expression with ongoing differentiation. For all integrins, no significant differences could be found in the two types of MSC. Integrin-mediated signalling seems to play an important role in the generation and maintenance of the chondrocytic phenotype during chondrogenic differentiation. Especially the receptors for fibronectin, vitronectin, osteopontin and collagens might be involved in the generation of the ECM. Intracellularly, their signals might be transduced by ILK and CD47. To fully harness the potential of these cells, future studies should be directed to ascertain their cellular and molecular characteristics for optimal identification, isolation and expansion.

Expansion on Extracellular Matrix Deposited by Human Bone Marrow Stromal Cells Facilitates Stem Cell Proliferation and Tissue-Specific Lineage Potential

“…31 Although integrin a5b1 (the fibronectin receptor) was expressed in undifferentiated stem cells, its expression rose during chondrogenic differentiation in hBMSCs. 27 The decrease of integrin a5b1 in hBMSCs might suggest that ECM expansion could rejuvenate hBMSCs into an undifferentiated state.…”

“…Data were shown as average -SD for n = 4. differentiation. 27 Therefore, the upregulation of integrins a2 and b5 may account for enhanced chondrogenic potential in ECM-expanded hBMSCs. Integrins also played a crucial role in chondrogenesis such as integrin b 1 30 and interacted with type II collagen through integrin a 2 when differentiating to mature chondrocytes.…”

“…Integrin b5, also termed an osteopontin receptor, was constantly expressed in BMSCs. 27 An osteopontin receptor might be involved in the processes of cellular migration and proliferation. 28 Further, this receptor might assist in the cellular differentiation in vitro.…”

Fibronectin and stem cell differentiation – lessons from chondrogenesis

“…Both fibronectin and its main cell surface receptor integrin a5b1 are expressed during condensation and throughout differentiation (Djouad et al, 2007;Goessler et al, 2009). In order to assemble cartilage matrix that is rich in type II collagen, integrins a1b1 and a2b1 -which act as collagen receptors -are also highly expressed during differentiation (Goessler et al, 2009).…”

“…In order to assemble cartilage matrix that is rich in type II collagen, integrins a1b1 and a2b1 -which act as collagen receptors -are also highly expressed during differentiation (Goessler et al, 2009). Numerous signaling pathways that lie downstream of integrins or are activated by chondrogenic factors have been linked to various stages of this process.…”