Study Of Surface Marker Antigens In Different Passages Of Mesenchymal Stem Cells FromTwo Different Mice Strains

Introduction: The purpose of this study was to cultivate bone marrow cells from two different mouse strains (NMRI and Balb/c) and to examine them in terms of expression of ten surface antigens from primary culture to passage 3.
Material and Methods: 6-8 weeks old either NMRI or Balb/c mice were sacrificed and their bone marrows were harvested and cultivated .Two weeks after culture initiation, the cells were tripsinized and about half of them subcultured in a new culture dish and the other half was prepared for flow cytometry in order to examine the expression of ten hematopoietic and endothelial markers including CD135, CD44, CD31, Thy1.2, CD11b, CD45, CD34, Vcam1, Sca-1and c-Kit. The cell cultures were examined till passage 3 for the given markers and there after the passage-3 cells from each strain were investigated for differentiation into bone and fat cells in vitro.
Results: In primary culture, the cell population was heterogeneous in which different morphology including flat, spindle and polygonal cells were observed.In passage 3 the culture mainly consisted of spindle cells. According to our result passage-3 cells from Balb/c mice seemed to be slightly longer than that of NMRI cells. Flow cytometric analysis showed that CD 44 was expressed in more than 90% of the cells in all examined passages. Although Thy1.2 was not expressed in primary culture, it was observed in about half to one fifth of the cells in passage 3.CD31 was not expressed on cells throughout the culture periods and the expression of CD135, CD45 and CD11b were gradually decreased from primary culture to passage C-kit, Sca1 and CD34 expression was slightly increased during the culture period. The two mice strains showed some differences in expressing certain markers. In contrast to Balb/c cells, some cells of NMRI strain expressed VCAM antigen. Furthermore, the two mice strains were different in that they showed varying pattern of sca-1 and Thy1.2 expressions during cultivation period.Passage-3 cells from both strains were easily differentiated into bone and fat cells in appropriate culture conditions.
Conclusion: Our results showed that mesenchymal cell cultures never become homogenous in terms of the markers expressed on the cell surfaces at least from primary culture to passage 3, although it gradually becomes morphologically homogenous during this period. The two mouse strains were somewhat different in terms of their morphology in culture and certain surface antigens.