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.
