Mesenchymal stem cells (MSC) reduce necrosis and apoptosis of pancreatic INS-1E beta cells during alloxan and streptozotocin exposure

 

Introduction:

MSC are of interest for cell therapy since they secrete tissue regenerative and immunomodulatory factors which restore the local microenvironment. Own previous results demonstrated protection of viability and p-Akt concentrations in ALX- and STZ-treated INS-1E rat insulinoma cells by cocultured human telomerase immortalized MSC (hMSC-TERT). Here we investigated the effects of hMSC-TERT on apoptosis in INS-1E.

Methods:

Cocultures used inserts with 1 µm pores that allow only humoral factors to pass. INS-1E were exposed for 24h to the beta cell-toxic compounds ALX and STZ in the presence or absence of hMSC-TERT and analysed for annexin V+ cells and activation of caspases.

Results:

Both substances substantially upregulated numbers of annexin V+ cells within 2h but only STZ induced effector caspases 3 and 7 (24h) indicating that ALX induced necrosis. Time lines displayed that STZ-induced activation of caspases 3 and 7 rises after 6h. This involved extrinsic apoptosis-related caspase 8 and intrinsic apoptosis-related caspase 9 which contributed to about 40 and 60% to total apoptosis (24h), respectively. Annexin V+ cells and activation of caspases 3 and 7 as well as 8 and 9 were significantly reduced by cocultured hMSC-TERT.

Conclusion:

These data indicate that cocultured MSC protect beta cells from both necrosis and apoptosis. Current investigations further analyse the potential relevance of apoptosis-related factors such as AIF, Bcl-2, Bcl-xL, Bak, Bax and Bad to further define the underlying molecular mechanisms.

Supported by: Brigitte Bull Stiftung, China Scholarship Council (CSC) stipend to W. Zhang.