SFRP4 and systemic sclerosis: Thus, ANGPTL7/C2orf40/SFRP4-expressing cells (subcluster 7, Figs. 2a and 3a) represent a population of papillary fibroblasts, a second SFRP4+ population found only in SSc skin, characterized below, representing myofibroblasts (Fig. 3a).