Expression of bone morphogenetic proteins by Dupuytren's fibroblasts

Abstract

Purpose: Dupuytren's fibroblasts, or myofibroblasts, are the primary cell type in Dupuytren's disease. Growth factors play a role in the differentiation of fibroblasts to myofibroblasts. Myofibroblasts are specialized fibroblasts that display morphologic and biochemical features similar to smooth muscle cells. Cytokines, adhesion molecules, and extracellular matrix components are all thought to play a role in myofibroblast transdifferentiation. Recent research has shown that specific cytokines, such as transforming growth factor beta1 (TGF-beta1), can modulate myofibroblast expression. We hypothesize that bone morphogenetic proteins (BMPs) play a role in the modulation of Dupuytren's fibroblasts.

Methods: Dupuytren's fibroblasts and normal palmar fascia fibroblasts (control) were analyzed for messenger RNA expression of BMPs (BMP-1, -2, -3, -4, -5, -6, -7, -8, -9, -10 and -11), their receptors (BMPR-IA, BMPR-IB, and BMPR-II), and their antagonists (follistatin and noggin) by reverse-transcription polymerase chain reaction (PCR). Western blot analysis and immunostaining also were used to confirm the differential expression of BMP-4.

Results: With reverse-transcription PCR the expression profile for normal palmar fascia fibroblasts versus Dupuytren's fibroblasts was found to show similar expression of BMP-1 and -11; qualitatively decreased expression of BMP-6, BMP-8, BMPR-IA, BMPR-IB, and BMPR-II in Dupuytren's fibroblasts; and no expression of BMP-4 in Dupuytren's fibroblasts. There was no expression of BMP-2, -3, -5, -7, -9, and -10 in both the control fibroblasts and Dupuytren's fibroblasts. In line with the messenger RNA expression pattern BMP-4 was detected in only the control fibroblasts and not in the Dupuytren's fibroblasts, whereas BMP-8 (chosen for comparison purposes) was detectable in both cell populations. Immunostaining for BMP-8 and BMP-4 confirmed our findings with reverse-transcription PCR and Western blot analysis.

Conclusions: This study reports on the expression of BMPs in Dupuytren's fibroblasts. We characterized the expression of BMPs in both normal palmar fascia fibroblasts and in Dupuytren's fibroblasts through reverse-transcription PCR, Western blot analysis, and immunostaining. The most significant difference in expression profiles was in the expression of BMP-4; that is, BMP-4 was expressed in the normal fibroblasts but not in the Dupuytren's fibroblasts. Whether BMP-4 is necessary and/or sufficient for maintaining a normal palmar fascia fibroblast phenotype is not yet known. Further studies are needed to elucidate the exact role of BMPs, and especially BMP-4, in Dupuytren's fibroblasts.