Background/Purpose: Caveolin-1 (Cav-1) deficiency has recently been shown to participate in the pathogenesis of tissue fibrosis in Systemic Sclerosis (SSc). Although the mechanisms involved have not been fully elucidated, it has been shown that Cav-1 deficiency can induce the phenotypic conversion of quiescent fibroblasts into activated myofibroblasts, the effector cells responsible for the fibrotic process in SSc. It has also been shown that Cav-1 deficiency mediates the phenotypic conversion of endothelial cells (EC) into myofibroblasts through endothelial-mesenchymal transition (EndoMT). Furthermore, Cav-1 deficiency causes a synergistic stimulation of TGF-β-induced EndoMT. The objective of this study was to examine the differences in global gene expression patterns of Cav-1 knock-out (KO) and wild-type murine lung EC regarding genes participating in the EndoMT process.

Methods: Pulmonary EC were isolated from wild-type (WT) and cav-1 knockout (cav-1 KO) mice employing immunomagnetic methods with sequential anti-CD31 and anti-CD102 antibody selection followed by in vitroculture and treatment with TGF-β1. To assess the differences in gene expression we performed microarray analysis of RNA isolated from cultured early passage lung EC from wild-type and cav-1 KO mice, employing the Affymetrix mouse cDNA array. Pathway analysis was performed employing Ingenuity software.

Results: A large number of differentially expressed genes were identified in lung EC from cav-1 KO mouse in comparison to EC from wild-type controls, including several unexpected extracellular matrix proteins such as decorin (58-fold higher), dermatopontin (28-fold higher), and versican (17-fold higher), as well as fibroblast growth factor 7 (30-fold higher), and some metalloproteinases, such as, matrix metalloproteinase 3 which was increased 12-fold. Of interest was also the observation that podoplanin a small glycoprotein considered to be specifically expressed in EC of lymphatic origin and which is highly increased in a variety of malignant cells was elevated 17-20 fold in samples from the cav-1 KO mouse lung EC. Numerous genes involved in the EndoMT process were also found to be upregulated in the cav-1 KO mice lung EC compared with the wild-type (WT) controls.  Cav-1 deficiency caused a synergistic stimulation of the TGF-β-induced gene expression patterns although some unique genes appeared to be induced by TGF-β treatment of the Cav-1 KO cells but not by treatment of the WT cells.

Conclusion: Cav-1 deficiency results in remarkable changes in the global gene expression patterns of murine lung EC and potentiates the stimulatory effects of TGB-β1 inducing the differential expression of numerous pro-fibrotic genes and of genes involved in EndoMT. These results provide novel information about the mechanisms responsible for the participation of Cav-1 in SSc pathogenesis and further suggest that modulation of Cav-1 expression or activity/function may be a novel therapeutic target for SSc. 

Supported by NIH grant RO1 AR055660

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/analysis-of-global-gene-expression-of-pulmonary-endothelial-cells-from-caveolin-1-knock-out-mice/