BACKGROUND:
Transforming growth factor (TGF)-ß1 produced in airway epithelia has been suggested as a contributor to the airway remodeling observed in asthma patients. The protein tyrosine phosphatase SHP2 is a demonstrable modulator of TGF-ß1 production and thus a potential regulator of airway remodeling.
OBJECTIVES: To define the signal event by which SHP2 regulates asthmatic responses in airway epithelial cells by using a mouse model of experimental OVA-induced airway remodeling.

METHODS: The airways of Shp2(flox/flox) mice were infected with recombinant adenovirus vectors expressing a Cre recombinase-green fluorescence protein (GFP) fusion protein as part of allergen provocation studies using mice sensitized with ovalbumin (OVA) and repeatedly challenged with OVA. Several endpoint pathologies were assessed, including airway hyper-responsiveness (AHR), lung inflammatory score, peribronchial collagen deposition, and a-smooth muscle actin (SMA) hyperplasia. In vitro studies using airway epithelial cells (BEAS-2B) were used to investigate the role of SHP2 in the regulation of pulmonary remodeling events, including the expression of collagen, a-SMA, and TGF-ß1.

RESULTS: Chronic OVA challenges in wild-type mice resulted in airway remodeling and lung dysfunction (e.g., increased inflammatory scores, collagen deposition (fibrosis), smooth muscle hyperplasia, and a significant increase in AHR). These endpoint pathology metrics were each significantly attenuated by conditional shp2 gene knockdown in airway epithelia. In vitro studies using BEAS-2B cells also demonstrated that the level of TGF-ß1 production by these cells correlated with the extent of shp2 gene expression.

CONCLUSIONS: SHP2 activities in airway epithelial cells appear to modulate TGF-ß1 production and, in turn, regulate allergic airway remodeling following allergen provocation.

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