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Over-expression of Spock2 in mice leads to altered lung alveolar development and worsens lesions induced by hyperoxia.

SPOCK2 was previously associated with genetic susceptibility to bronchopulmonary dysplasia in a French population of very preterm neonates. Its expression increases during lung development and is increased after exposure of rat pups to hyperoxia as compared to controls bred in room air. To further investigate the role of SPOCK2 during lung development, we designed two mouse models, one that uses a specific anti-Spock2 antibody and one that reproduces the hyperoxia-induced Spock2 expression with a transgenic mouse model resulting in a conditional and lung-targeted over-expression of Spock2. When mice were bred under hyperoxic conditions, treatment with anti-Spock2 antibodies significantly improved alveolarization. Lung over-expression of Spock2 altered alveolar development in pups bred in room air and worsened hyperoxia-induced lesions. Neither treatment with anti-Spock2 antibody, nor over-expression of Spock2 were associated to abnormal activation of mmp2. These two models did not alter the expression of known players in alveolar development. This study brings strong arguments for the deleterious role of SPOCK2 on lung alveolar development especially after lung injury, suggesting its role in BPD susceptibility. These effects are not mediated by a deregulation in metalloproteases activity and in expression of factors essential to normal alveolarization. The balance between type 1 and 2 epithelial alveolar cells may be involved.