Expression of PDGF-BB and PDGFR in UCD-200 comb biopsies. A–F Immunofluorescence staining for PDGF-BB (green), PDGFR (red) and their MERGED, in hHC (A-C) and in SSc patients (D-F). The expression of PDGF-BB and PDGFR was significantly higher in SSc patients than in hHC. I–T – Immunofluorescence staining for PDGF-BB (green), PDGFR (red) and their MERGED, in cHC (I–K) and in UCD-200 with erythema (L–N), edema (O–Q) and necrosis (R–T). PDGF-BB is expressed only by EC. PDGFR is widely expressed by pericytes of dermal vessels and in fibroblasts. Their increased expression paralleled the severity of comb lesions. (G and U) Densitometric analysis of immunofluorescence intensity for human (G) and chicken (U) PDGF-BB. Each open square (□) represents the value of both 1 HC and 1 SSc; each solid square (■) represents the value of 1 SSc patient and 1 UCD-200, respectively. Our results are expressed as median (range) of the immunofluorescence optical density (arbitrary units). The expression of PDGFBB was significantly higher in SSc patients than in hHC (hHC vs. SSc: ***p < 0.0001). No difference was observed between cHC and the UCD-200 with erythema; however, a significant difference was observed when both cHC and UCD-200 with erythema were compared with the other 2 groups (PDGF-BB, erythema vs. edema: **p = 0.0002; edema vs. necrosis: ***p < 0.0001), mirroring the severity of comb lesions. H, V – Densitometric analysis of the intensity of immunofluorescence staining of human (H) and chicken (V) PDGFR. Each open dot (○) represents the PDGFR value of both 1 hHC and 1 cHC; each solid dot (●) represents the PDGF value of 1 SSc patient and 1 UCD-200 sample. Our results are expressed as median (range) of the immunofluorescence optical density (arbitrary units). The expression of PDGFR in SSc patients was significantly higher than in hHC (hHC vs. SSc: ***p < 0.0001). No difference was observed between cHC and the UCD-200 with erythema; however, a significant difference was observed when both cHC and UCD-200 with erythema were compared with the other 2 groups (PDGFR, erythema vs. edema: ***p < 0.0001; edema vs. necrosis: **p = 0.0002), mirroring the severity of comb lesions