intimal hyperplasia intimal hyperplasia intimal hyperplasia is the thickening of the tunica intima of a blood vessel as a complication of a reconstruction procedure or endarterectomy. intimal hyperplasia is the universal response of a vessel to injury, it is a restenosis and this is an important reason of late bypass graft failure, particularly in vein and synthetic vascular grafts. cause intimal hyperplasia is due to a dysfunction of endothelial cells which results in a reprogramming of the vascular smooth muscle cells (vsmcs). as a result, vsmcs proliferate and change their phenotype. possible treatment a possible treatment to avoid this could be hydrogen sulfide. hydrogen sulfide (h2s) works as a vasculoprotective gasotransmitter in human body but is also tested to reduced intimal hyperplasia. there are different kinds of h2s donors: nahs (the reference in scientific literature despite the fact it is too toxic to use it in human patients) and sts (already used in patient to treat cyanide poisoning).