TGFB1 and systemic sclerosis: Although TGF-β1 was induced by Gremlin-1, TGF-β1 itself did not induce Gremlin-1, therefore we sought to determine if IL-13 induced Gremlin-1 as IL-13 is a known pro-fibrotic molecule particularly elevated in SSc (O’Reilly, 2013).