Integrins a2ß1 and a11ß1 regulate the survival of mesenchymal stem cells on collagen I

Popov C, Radic T, Haasters F, Prall WC, Aszodi A, Gullberg D, Schieker M, Docheva D.
Source: Cell Death Dis.
Publication Date: (2011)
Issue: 28;2: e186
Research Area:
Basic Research
Cells used in publication:
Mesenchymal stem cell (MSC), human
Species: human
Tissue Origin: bone marrow
Although mesenchymal stem cells (MSCs) are the natural source for bone regeneration, the exact mechanisms governing MSC crosstalk with collagen I have not yet been uncovered. Cell adhesion to collagen I is mostly mediated by three integrin receptors - a1ß1, a2ß1 and a11ß1. Using human MSC (hMSC), we show that a11 subunit exhibited the highest basal expression levels but on osteogenic stimulation, both a2 and a11 integrins were significantly upregulated. To elucidate the possible roles of collagen-binding integrins, we applied short hairpin RNA (shRNA)-mediated knockdown in hMSC and found that a2 or a11 deficiency, but not a1, results in a tremendous reduction of hMSC numbers owing to mitochondrial leakage accompanied by Bcl-2-associated X protein upregulation. In order to clarify the signaling conveyed by the collagen-binding integrins in hMSC, we analyzed the activation of focal adhesion kinase, extracellular signal-regulated protein kinase and serine/threonine protein kinase B (PKB/Akt) kinases and detected significantly reduced Akt phosphorylation only in a2- and a11-shRNA hMSC. Finally, experiments with hMSC from osteoporotic patients revealed a significant downregulation of a2 integrin concomitant with an augmented mitochondrial permeability. In conclusion, our study describes for the first time that disturbance of a2ß1- or a11ß1-mediated interactions to collagen I results in the cell death of MSCs and urges for further investigations examining the impact of MSCs in bone conditions with abnormal collagen I.