Critical role of FcR gamma-chain, LAT, PLC gamma 2 and thrombin in arteriolar thrombus formation upon mild, laser-induced endothelial injury in vivo

Objective: The role of collagen receptor complex GPVI-FcR gamma-chain, PLC gamma 2 and LAT in laser-induced thrombosis is unclear. Controversy surrounds whether collagen is exposed in this model or whether thrombosis is dependent on thrombin. This study hypothesized that collagen exposure plays a critical role in thrombus formation in this model, which was tested by investigating contributions of FcR gamma-chain, LAT, PLC gamma 2 and thrombin. Methods: Thrombi were monitored using intravital microscopy in anesthetized wild-type and FcR gamma-chain, LAT and PLC gamma 2 knockout mice. Hirudin (thrombin inhibitor) was administered to wild-type and FcR gamma-chain knockout mice. Results: Significantly reduced thrombus formation was observed in FcR gamma-chain and PLC gamma 2 knockouts with a greater decrease observed in LAT knockouts. Dramatic reduction was observed in wild-types treated with hirudin, with abolished thrombus formation only observed in FcR gamma-chain knockouts treated with hirudin. Conclusions: GPVI-FcR gamma-chain, LAT and PLC gamma 2 are essential for thrombus generation and stability in this laser-induced model of injury. More importantly, a greater role for LAT was identified, which may reflect a role for it downstream of a second matrix protein receptor. However, inhibition of platelet activation by matrix proteins and thrombin generation are both required to maximally prevent thrombus formation.