Several of the highly upregulated genes in cluster 4 were recognizable as genes previously shown to correlate with the severity of SSc disease, such as THBS1 (refs. 41,42), TNC43, CTGF42, THY1 (ref. 36), CDH11 (ref. 32), and CCL2 (ref. 44, Supplementary Data 8). Here, CCL2 is linked to systemic sclerosis.