Exp Clin Endocrinol Diabetes 2013; 121 - P50
DOI: 10.1055/s-0033-1336723

Bone marrow-derived MSC enhance survival of injured β-cells by preserving Akt signalling via humoral factors

C Liu 1, L Lang 1, M Schmid 1, C Jäger 1, S Sojka 1, J Baumann 1, G Päth 1, J Seufert 1
  • 1Uniklinik Freiburg, Innere Medizin II – Endokrinologie/Diabetologie, Freiburg, Germany

Introduction: Own previous work has verified in vitro that human bone marrow-derived MSC with telomerase overexpression (hMSC-TERT) migrate towards injured rat INS-1E β-cells and increase their viability. Both cell lines were considered a valid model since they closely resemble primary rat (plastic-adherent) MSC and islets. Here we investigated whether humoral factors by cocultured hMSC-TERT reduce apoptosis and induce proliferation in INS-1E. Since AKT signalling plays a very central role for survival and proliferation in β-cells, we further analysed whether humoral hMSC-TERT-derived factors rescue p-AKT levels during β-cell injury.

Methods: hMSC-TERT were cocultured in inserts with 0.4 µm pores that allow only soluble factors but not cells to pass the membrane. Apoptosis was measured by Annexin-V FACS and caspases 3/7 activity assay. Viability was measured by MTS assay. Active (phosphorylated) p-AKT levels were detected by Western blot. Proliferation was analysed by counting cell numbers and Ki-67+ nuclei.

Results: Cocultured hMSC-TERT significantly reduced ALX and STZ-induced apoptosis in INS-1E. The degree of this reduction was similar to enhancement of viability. LD50 dosages of ALX (6.6 mM) and STZ (0.66 mM) completely deplete p-AKT levels within 2 and 8h, respectively. This loss of p-AKT was substantially prevented by cocultured hMSC-TERT that have been preactivated over night by injured INS-1E while hMSC-TERT without preactivation have only small effects. Furthermore, chronic coculture of hMSC-TERT enhanced proliferation of INS-1E to significant levels after 5 days. HEK293 human kidney cells and MRC5 human fibroblasts were used as controls to verify specificity of MSC-mediated effects.

Conclusions: MSC-derived factors promote survival of injured β-cells by reduction of apoptosis via protection of p-AKT levels. Modulation of AKT signalling may further be responsible for increased viability and enhanced proliferation in untreated β-cells.