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Purpose:
Dermal fibroblasts from patients with systemic sclerosis (SSc) and hypertrophic scars (HS) share important fibrotic characteristics including dysregulated TGFβ and CTGF signaling and increased synthesis of extracellular matrix constitutents. Our objective was to compare the transcriptosome of fibroblasts from immune-mediated (SSc) vs a non-autoimmune mediated (HS) fibrotic skin disease to gain insight into disease SSc pathogenesis.
Methods:
RNA was isolated from early passage (<4) dermal fibroblasts from middle-aged Caucasian subjects (8 each, healthy donors, diffuse SSc, thermal injury patients with HS) profiled with the Illumina Human Ref 8 BeadChips. Differentially expressed genes were ascertained using the Optimal Discovery Procedure (J.D. Storey), and random variance t-test (Dudoit et al) in BRB Array Tools (NCI).
Results:
Analysis of the expression data show that there are at least 975 genes that are differentially expressed between normal, SSc and HS fibroblasts at a nominal p=4x10-4 and FDR<0.1%. By setting the FDR at a stringent level (<5%), we found there were 646 genes differentially expressed in SSc vs normal fibroblasts, compared to >6,000 genes differentially expressed in SSc vs HS fibroblasts.
Unsupervised hierarchical clustering of genes demonstrated genes unique and common to each of these conditions (Figure 1). Other genes having significantly (p<0.001) increased expression in SSc vs HS genes include COL1A1 and COL1A2 (3 to 6 fold) collagen genes, SMADs2/3 (2-fold), CTGF (4-fold), LTBP2-4 (2-4 fold), SPARC (5-fold), and FBN1 (3-fold).
Pathway analysis demonstrated highly significant differential regulation (Hotelling test p<1x10-7) of >100 known pathways when SSc fibroblast are compared to HS fibroblasts. In contrast only, 7 highly differentially regulated pathways were found in SSc compared to normal fibroblasts. Among these are pathways relevant to receptor-type tyrosine kinase signaling (CBL, EGFR, PDGF, G alpha i), regulation of mitogen-activated protein kinases (MAPK) and immune responses (TGFβ, NFAT and IL-6).
Conclusion:
Despite their similar pro-fibrotic characteristics, at the molecular level, SSc dermal fibroblasts are more similar to normal fibroblasts than HS fibroblasts. The pattern of gene activation in SSc fibroblasts is much more restricted than in HS fibroblasts. This suggests that SSc fibroblast activation is a result of dysregulation of a specific set of genes involved in wound healing rather than a generalized activation of the fibrotic response.
Dermal fibroblasts from patients with systemic sclerosis (SSc) and hypertrophic scars (HS) share important fibrotic characteristics including dysregulated TGFβ and CTGF signaling and increased synthesis of extracellular matrix constitutents. Our objective was to compare the transcriptosome of fibroblasts from immune-mediated (SSc) vs a non-autoimmune mediated (HS) fibrotic skin disease to gain insight into disease SSc pathogenesis.
Methods:
RNA was isolated from early passage (<4) dermal fibroblasts from middle-aged Caucasian subjects (8 each, healthy donors, diffuse SSc, thermal injury patients with HS) profiled with the Illumina Human Ref 8 BeadChips. Differentially expressed genes were ascertained using the Optimal Discovery Procedure (J.D. Storey), and random variance t-test (Dudoit et al) in BRB Array Tools (NCI).
Results:
Analysis of the expression data show that there are at least 975 genes that are differentially expressed between normal, SSc and HS fibroblasts at a nominal p=4x10-4 and FDR<0.1%. By setting the FDR at a stringent level (<5%), we found there were 646 genes differentially expressed in SSc vs normal fibroblasts, compared to >6,000 genes differentially expressed in SSc vs HS fibroblasts.
Unsupervised hierarchical clustering of genes demonstrated genes unique and common to each of these conditions (Figure 1). Other genes having significantly (p<0.001) increased expression in SSc vs HS genes include COL1A1 and COL1A2 (3 to 6 fold) collagen genes, SMADs2/3 (2-fold), CTGF (4-fold), LTBP2-4 (2-4 fold), SPARC (5-fold), and FBN1 (3-fold).
Pathway analysis demonstrated highly significant differential regulation (Hotelling test p<1x10-7) of >100 known pathways when SSc fibroblast are compared to HS fibroblasts. In contrast only, 7 highly differentially regulated pathways were found in SSc compared to normal fibroblasts. Among these are pathways relevant to receptor-type tyrosine kinase signaling (CBL, EGFR, PDGF, G alpha i), regulation of mitogen-activated protein kinases (MAPK) and immune responses (TGFβ, NFAT and IL-6).
Conclusion:
Despite their similar pro-fibrotic characteristics, at the molecular level, SSc dermal fibroblasts are more similar to normal fibroblasts than HS fibroblasts. The pattern of gene activation in SSc fibroblasts is much more restricted than in HS fibroblasts. This suggests that SSc fibroblast activation is a result of dysregulation of a specific set of genes involved in wound healing rather than a generalized activation of the fibrotic response.
P. Gourh, None; X. Zhou, None; S. Assassi, None; F.C. Arnett, None; F.K. Tan, None.