Inhibitory Effects Of AcSDKP On Growth Of Murine Bone Marrow Mesenchymal Stem Cells In Vitro

N-Acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is a physiological regulator. It has been shown to inhibit the proliferation of the hematopoietic stem/progenitor cells and other cell types. This low molecular weight peptide naturally prevents the entry of cells into S phase and maintains them in the G0/G1 phases of cell cycle. This inhibition was entirely reversible and absent of toxicity. Bone marrow mesenchymal stem cells (MSCs) are thought to be the common precursors of cell lineages in bone and bone marrow, including osteoblasts, chondrocytes, adipocytes and hematopoietic- supporting stroma. Bone marrow MSCs also may contribute themselves to the constitution and function of hematopoietic microenvironment. The operational hypothesis of this work was that AcSDKP can regulate the growth of MSCs. The present study was performed to evaluate effects of the tetrapeptide on the growth of murine bone marrow MSCs in vitro cultures with or without its addition using the cell clonogenic assays and the related experimental techniques.The findings of this study provided support for our hypothesis. The- s"addition of AcSDKP dramatically reduced the number and size of murine bone marrow MSC colonies in vitro. The peak inhibitory activity was observed at l(T12mol/L AcSDKP, and the activity declined at higher or lower concentrations. Little or no effect was seen at 10-10mol/L and 10-14 mol/L of AcSDKP. The dose-response curve was biphasic. Furthermore, The tetrazolium salt-based colorimetric assay (MTT test) also evidenced that AcSDKP can depress growth of the bone marrow MSCs in dose-dependent manner. If AcSDKP is withdrawn following exposure of the tetrapeptide to the same cultures for 72h, the number of MSC colonies significantly returned towards control. The number of MSC colonies increased as time periods of AcSDKP exposure to the cultures were shortened. These results indicated that the inhibitory effect of AcSDKP is reversible. However, even if the time period of AcSDKP exposure was cut down to 12h, the colony number still was considerably less than that of the control group without the addition of the tetrapeptide, implying it might has an inhibitory action for the MSCs adhesion to the plastics. AcSDKP resulted significantly in the decrease in the number of MSC colonies in the murine bone marrow cultures with 10% ~ 30% neonate bovine serum, but not at 40%, suggesting the tetrapeptide can exert its negatively regulatory role indirectly, by blocking stimulator action on MSCs.In conclusion, this study obtains the first evidence that AcSDKP is able to inhibit the in vitro growth of bone marrow MSCs. And this inhibitory effect is biphasic and dose-dependent, time-dependent, and reversible. AcSDKP may exert its influence on MSCs by interfering with stimulators of cell proliferation. It would appear that this low-molecularweight peptide attenuates MSC adhesion. Therefore, our data provide valuable information for the research into the negative regulation of MSCs growth.