[The mechanism of bone marrow-derived mesenchymal stem cells excessive senescence in severe aplastic anemia mouse model].

Objective: To explore the mechanism of excessive senescence in bone marrow-derived mesenchymal stem cells (BM-MSC) of mouse model with severe aplastic anemia (SAA) . Methods: 40 BALB/c mice were randomly assigned to two groups of control ( n =20) and AA ( n =20) . SAA mouse model was induced by intraperitoneal injection with IFN-γ and intragastric infusion with busulfan. BM-MSC were isolated and cultured from bone marrow of SAA and healthy mice. The cell morphology was observed by inverted microscope and cell cytoskeleton was stained by Rhodamine-Phalloidin; The level of proliferation was analyzed by CCK-8 method, and cell cycle was tested by flow cytometry. Senescence-associated β-galactosidase (SA-β-gal) assay was used to detect senescent BM-MSC; The expression of mTOR protein was detected by Western blot method. Results: BM-MSC from normal mice presented spindle-shaped, clear boundaries and stress fibers were arranged in parallel, neat. while BM-MSCs from SAA mice presented cell volume increases, tiled, ill-shaped and the stress fiber appeared to be disordered. The decreased activity of proliferation [more cells restricted in G(0)/G(1) phase [ (77.461±1.567) % vs (46.045±2.055) %, t =-34.384, P <0.001], increased percentage of SA-β-gal positive cells [ (75±11) % vs (28±8) %, t =15.454, P <0.001] and notably enhanced expression of mTOR of BM-MSC from SAA mice were observed when compared with those from normal mice. Conclusion: This study clarified senescent BM-MSCs from SAA model mice, which could be caused by the excessive activation of mTOR pathway.