TGFB1 and osteogenesis imperfecta: In agreement with this idea, ex-vivo treatment of OI fibroblasts with losartan had no effect on SMAD2 phosphorylation nor did losartan affect genes associated with the renin-angiotensin pathway and only minimal effects on genes associated with the TGFβ family, their modulators, or genes directly downstream of TGFβ or the MAPK pathway.