Bovine bone marrow mesenchymal stem cells (MSCs) cultured in condensate culture, spontaneous and independent for any external biostimulants, undergo chondrogenic differentiation. In the present study, the bovine MSC chondrogenesis pathway was studied by analyzing stage-specific gene expression using quantitative 'Real Time' reverse transcriptase polymerase chain reaction (qRT-PCR). Results showed that bovine MSCs underwent complete chondrogenesis; the initial stage was characterized by expression of sox 9 messenger ribonucleic acid (mRNA), followed by high transcription of chondrocyte specific genes, collagen type II and IX, biglycan and cartilage oligomeric matrix protein, and the final prehypertrophic and/or hypertrophic stage was distinguished by increased expression of collagen type X. From day 7 to day 14 of differentiation increased mRNA expression of the transforming growth factors beta1 and beta2, basic fibroblast growth factor (FGF 2), bone morphogenic protein 6 (BMP 6), insulin-like growth factors 1, parathyroid hormone related peptide and indian hedgehog (Ihh) were detected. These results suggest that these well know chondrogenic growth factors may play a role in bovine chondrogenesis in autocrine and/or paracrine manner. On day 21 of the culture, FGF 2, BMP 6 and Ihh were highly expressed, compared to cells cultured in monolayer manner, which suggests a possible function in maintaining the terminal stage of differentiation. This data extends our knowledge about the unusual species-specific bovine MSC chondrogenesis, allowing us to define the phenotype of the differentiated cells. Furthermore, this study contributes to our in understanding of known chondrogenic-growth factors in autocrine and/or paracrine manner playing a role in the spontaneous differentiation.

The LEC rat is reported to exhibit hypersensitivity to X-irradiation, deficiency in DNA double-strand break repair, and radio-resistant DNA synthesis. This character of the LEC rat has been thought to be due to abnormal G1 arrest in cells after X-irradiation. In this report, we re-investigated the effect of X-irradiation on the cell cycle in primary-cultured fibroblasts. Primary-cultured fibroblasts derived from LEC and BN rats were exposed to 4 Gy of X-ray and their cell cycle analysis was performed with a flow cytometer. Fibroblasts derived from both rats showed normal response of the cell cycle, indicating the arrest at both G1- and G2/M-phase and no difference in the cell cycle population between fibroblasts derived from both rats. In contrast, when the same analysis was performed using the cell line, L7 and W8, which had been established from the lung fibroblasts of LEC and control WKAH rats, respectively, by immortalizing with SV40 T-antigen, L7 cells but not W8 cells showed impaired G1 arrest and abnormal cell cycle. These results suggest that fibroblasts derived from LEC rats possess the normal cell cycle response after X-irradiation, if they are kept naive as not immortalized with SV40 T-antigen.