ABSTRACT
<p><b>OBJECTIVE</b>To explore the effective method for enrichment of rat peripheral blood-derived mesenchymal stem cells(PBMSC) and study the cell biological characteristics.</p><p><b>METHODS</b>Peripheral mononuclear cells were isolated by density gradient centrifugation from blood of 4 week old rats after G-CSF mobilization. Thereafter, the fibroblast-like cells were acquired by plastic-adherent culture, and the proliferation curve was assayed. For analyzing surface markers of the second generation cultured isolated PBMSC, both flow cytometry(CD90, CD44, CD29, CD45, CD11b and CD79a) and immunocytochemical staining(CD73, CD105, CD34 and HLA-DR) methods were used. Furthermore, the differentiation capacities of PBMSC into osteocytes, chondrocytes and adipocytes were identified.</p><p><b>RESULTS</b>(1) The adherent cells displayed typical colony-forming unit fibroblast(CFU-F) growth pattern after 6-7 day of primary culture and reached 80% confluence after 21 days of culture. The passaged PBMSC possessed high proliferative capacity and spindle growth pattern and was able to grown into exponential phase next day with a doubling time of 39.2 h. (2) PBMSC expressed mesenchymal markers such as CD90, CD44, CD29, CD73 and CD105, but failed to expressed markers of CD45, CD11b, CD79a, CD34 and HLA-DR. (3) After 21 days of culture in osteogenic, chondrogenic and adipogenic differentiation media, calcifying nodules, intracellular glycosaminoglycans and lipid droplets could be found by alizarin red, alcian blue and oil red-O staining, respectively.</p><p><b>CONCLUSION</b>PBMSC can be enriched from rat peripheral blood with high purity and abundance by our methods. The growth and phenotypic characteristics of the isolated PBMSC are consistent with that of well-known MSC, and these cells possess the capability to multi-lineage mesoderm differentiation.</p>