Adult mesenchymal progenitor cells (MPCs) are adherent stromal cells of non-haematopoietic origin derived from bone marrow and other tissues. Upon limited in vitro expansion, they retain their self-renewal capacity as well as their potential to differentiate into tissues of mesenchymal lineage, such as bone, cartilage, muscle, tendon and connective tissues. Amongst these tissues, cartilage is the only one with insufficient self-renewal capacity, thus MPCs would qualify as an excellent tool for therapeutic regeneration of focal cartilage lesions. However, optimal in vitro manipulation of MPCs is a prerequisite; identification and a better understanding of the molecular mechanisms regulating their differentiation pathways are needed. Despite wide usage of rats as a mammalian experimental model for preclinical fracture healing and orthopaedic tissue regeneration studies, basal gene and protein expression profiles of the osteo-chondrogenic differentiation lineages of adult rat MPCs have rarely been investigated. Therefore, this study was carried out for a quantitative RT-PCR based time-course profiling of osteo- and chondrogenesis related gene expression in undifferentiated and differentiated rat adult MPCs. In addition, with an antibody array analysis TIMP-1, MCP-1 and VEGFα-164 were detected in the culture supernatant and CINC-2 and β-NGF in the cell lysate of MPCs according to their differentiation commitment. Identification of differentially expressed genes and proteins along the osteo-chondrogenic lineage provides a foundation for a more reproducible and reliable quality and differentiation control of rat bone marrow-derived MPCs used for osteochondrogenic differentiation studies.

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