Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Fibroblast-Specific Activation of TGF-Beta in Transgenic Mice Recapitulates a Histological Phenotype of Hypoxic Pulmonary Hypertension In Vivo
Derrett-Smith1, Emma, Shi-wen1, Xu, Baliga2, Reshma S., Khan1, Korsa, Abraham1, David, Denton1, Christopher P.
Vascular complications of systemic sclerosis (SSc) are a major cause of mortality and morbidity and are initiated by endothelial injury. The transgenic mouse strain TbRIIDk-fib expresses a kinase-deficient type II TGF-b receptor linked to a fibroblast-specific promoter leading to balanced ligand-dependent upregulation of TGF-b signalling. We have examined changes in pulmonary vascular structure and signalling in this model of systemic sclerosis and compared responses to hypoxic stress with wildtype control mice.
Transgenic (n=6) or littermate wildtype mice (n=6) were exposed to hypoxic stress (10% O2 for 21 days) and pulmonary vascular responses were compared with normoxic transgenic and control animals (n=6 in each group). We evaluated vascular and perivascular architecture by H&E and special stains, and used immunohistochemistry to examine TGF-b and endothelin expression. Vascular smooth muscle cell (vSMC) proliferation and biochemical phenotype was also studied in vitro by culturing under hypoxic and normoxic conditions, including signalling responses to exogenous TGF-b1 and endothelin-1.
Increased TGF-b1 immunostaining was confirmed in transgenic lung vessels with an associated reduction in endothelin receptor A expression in cultured vSMCs (mean wildtype copy number 2517±1261, mean transgenic copy number 315±73, p<0.05). There was no change in these variables between normoxic or hypoxic mouse tissues. As previously reported, in normoxic transgenic mice medial thickness was significantly increased in pulmonary arterial vessels compared with wildtype littermates. After exposure to hypoxia there was significant thickening of the pulmonary vascular smooth muscle cell layer in wildtype mice but no further increase in transgenic vessel wall thickness. These results are summarised in Figure 1. There was increased extracellular matrix deposition and marked perivascular infiltration with mononuclear inflammatory cells in hypoxic transgenic mice compared with hypoxic wildtype littermate animals (mean cell number per high power field in wildtype lung 128.8±21.9, in transgenic lung 176.0±20.3, p<0.05).
In this study we confirm that the pulmonary vascular phenotype previously reported in this mouse model of scleroderma recapitulates the histological response of wildtype littermates to hypoxia, an established murine model of pulmonary hypertension. Our results support a role for TGF-b overactivity in the pulmonary vasculopathy of systemic sclerosis.
To cite this abstract, please use the following information:
Derrett-Smith, Emma, Shi-wen, Xu, Baliga, Reshma S., Khan, Korsa, Abraham, David, Denton, Christopher P.; Fibroblast-Specific Activation of TGF-Beta in Transgenic Mice Recapitulates a Histological Phenotype of Hypoxic Pulmonary Hypertension In Vivo [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1054