| BACKGROUND and AIMBone marrow mesenchymal stem cells (MSC) are thought to be involved in mesenchymal tissue maintenance and repair. Depletion of stem cells has been suggested to contribute to degenerative diseases affecting a number of tissues including brain, liver, skin and bone, and may also be involved in the degeneration associated with aging. Many functions of mouse bone marrow mesenchymal stem cell (BMSC) have changed with the age increased, included the decrease of colony form unit function, the decrease of osteogenic, adipogenic and chondroblast differentiation function.,the decrease of proliferation function, decrease of telomerase function and the length of the telomere. Recent researches found that cell fusion achieve effective reprogramming of cells function. BMSC can fusion with intestinal stem cell, liver cell, cardiomyocyte , then change their function . We do this research to investigate the function change of aged BMSC fused with young BMSC in mice.METHODSEstablished young (Y age: 2-3 months) and old (O age: 18-24 months) C57BL/6 mice BMSC which labeled with PKH26 membrane fluorescent kit (red) with young and old green fluorescent protein (GFP) transgenic C57BL/6 mice BMSC fusion model by using polyethylene glycol 1500 (PEG 1500). Cell fusion rate and cell surface markers were detected by flow cytometry. Fluorescence microscopy was used to detect fused cell morphology and nuclear characteristics. In this study, we examined age dependent changes in BMSC proliferation and differentiation potential in Y group, O group, and another three fusion groups (Y-Y group, Y-O group, O-O group). Compared the five groups'proliferation potential by counting cell number at days 2, 4, 6, and 8. The osteogenic and adipogenic differentiation potential of the five groups were determined by using standard differentiation procedures.RESULTSWe can get 30.45%±4.13% fusion cells by using PEG, the percentage of the fusion rate in the three fused groups were no significant difference, the detail numbers were (29.41%±3.00% vs. 30.54%±1.20% vs. 31.41%±6.63%) , P>0.05. Fused BMSC coincided with the common BMSC were reactive to the BMSC lineage-specific CD44, Sca-1 surface markers and negative for the hematopoietic stem cells (HSCs) lineage-specific surface markers such as CD34,CD117,CD31,CD45. Y-O group percentage of increase cell number compared to O-O group were significantly greater at days 2, 4, 6, and 8, the detail numbers were (122.2%±4.6%) vs. (104.64%±1.25%);(213.25%±15.29%) vs.(130.02%±6.82%);(318.46%±19.86%) vs. (179.4%±9.54%);(439.98%±24.09%) vs. (240.03%±28.07%);P <0.05. Quantifying the positive area stained with Alizarin Red which represented osteogenic differentiation potential of BMSC showing significantly higher percentage in Y-O group compared to O-O group (25.46%±1.52%) vs. (13.85%±1.69 %), P <0.01. Y-O group also have more higher percentage of the positive area stained with Oil Red O which represented adipogenic differentiation potential of BMSC than O-O group (12.99%±2.61%) vs. (6.03%±1.71%), P <0.05.CONCLUSIONS1. At the same conditions, the functions of mouse BMSC decreased with the age increased, included proliferation function , osteogenic, adipogenic differentiation function.2. After cell fusion, fusion cells can maintain the BMSC special characteristics.3. Aged bone marrow stem cells can be rejuvenated by cell fusion with young bone marrow stem cells, particularly proliferation and osteogenic, adipogenic differentiation potential.
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