Background: 

The tyrosine phosphatase SHP-2 regulates growth factor dependent angiogenesis and functions both as phosphatase and adapter protein. We investigated, whether SHP-2 plays a role in hypoxia induced vessel growth and which functions of SHP-2 is involved in this process.

Methods: 

Overexpression of SHP-2 wildtype (SHP-WT), catalytically inactive (SHP-CS), constitutively active (SHP-E76A) or active SHP-2 with lost adapter function (SHP-Y2F) was achieved by lentiviral transduction of cultured human microvascular endothelial cells (HMEC). Proliferation was assessed by MTT reduction. Cells were exposed to hypoxia (pO₂ 36mmHg) for 4h or 24h. HIF-1a was detected by western blot and angiogenesis assessed by aortic ring sprouting in matrigel ex vivo.

Results: 

Expression of SHP-E76A or SHP-Y2F resulted in a 1.7-fold increase in proliferation during normoxia as well as hypoxia (both p<0.01, n=36). SHP-E76A also enhanced HIF-1a expression (p<0.05 compared to SHP-WT, n=4) and aortic vessel growth (p<0.01, n=5). Expression of SHP-Y2F had no significant impact on proliferation and HIF-1a expression during hypoxia or hypoxia-reoxygenation (H/R) but enhanced proliferation under normoxia (p<0.001, n=24). Expression of SHP-CS, on the contrary, reduced proliferation and aortic sprouting during normoxia (p<0.05, n=24), hypoxia (p<0.05, n=36) and after H/R (p<0.01, n=36). Hypoxia inducible factor 1a (HIF-1a) expression was also reduced (p<0.05, n=4).

Conclusion: 

The phosphatase activity of SHP-2 is important for endothelial cell proliferation and vessel sprouting upon hypoxia or H/R, likely by upregulation of HIF1a. The adapter function of SHP-2 appears not to be functionally important in this context. Thus, stimulation of SHP-2 catalytic activity may be a promising tool for angiogenesis induction in ischemic conditions.