Effect Of Morphology And Express Of Platelet-derived Growth Factor-A Of Mild Vitamin A Deficiency On Rat Lung Development

ObjectiveTo investigate the effect of morphology and express of platelet-derived growth factor-A (PDGF-A) of mild vitamin A deficiency (MVAD) on rat lung development in three periods. Methods24 female Sprague-Dawley rats were divided into MVAD group and control group randomly. MVAD model was established in pregnant rats. The fetal/neonatal lungs of MVAD group and control group were obtained at the embryo 16, 20 days and postnatal 1 day, which Paraffin sections and electron microscopic sections were made from. The paraffin sections were stained by hematoxylin and eosin (HE) for light microscopy, Masson's trichrome staining for collagen and Orcein staining were also performed, and the ultramicrostructure changes were observed by electron microscope. The RT-PCR and immunohistochemistry methods were used to detect the mRNA and protein level of PDGF-A gene. The difference of lung morphogenesis and the express of PDGF-A between MVAD group and control group was studied.Results1. HE staining showed that at embryo 16d compared with branching lumens of bronchus in control group the round ones in MVAD group was immature; At embryo 20d, compared with control group, it had fewer alveolar numbers, smaller alveolar space, and thicker alveolar septum (P<0.01); At postnatal 1d MVAD group showed the large variation. Some areas showed the dilatation of many alveolar spaces, the thinner septum (P<0.01) and destruction of the septal walls, while the others showed atelectasis, interstitial hyperemia and thicker septum.2. Masson's trichrome staining showed MVAD group had smaller areas of collagen fibers that were thinner and sparser than control group at the same magnification (P<0.01).3. Orcein staining showed that in MVAD group compared with control group there were sparser distributed and weakly stained elastic fibers in airway wall and alveolar wall, while in vascular wall the thinner ones had focal architecture distortion and fiber fracture.4. Under the electronic microscope, compared with control group, epithelial cells with fewer microvilli showed sparse alignment between which there were some vacuolus at embryo 16d; Lamellar body in typeâ…¡alveolar epithelial cells, cellular organs such as bioblast in endochylema and microvilli on epithelial cells were deficient at embryo 20d and postnatal 1d.5. The RT-PCR results showed the mRNA expression of PDGF-A gene in rat lung tissue was down-regulated in MVAD group compared with control group (P<0.01).6. Immunohistochemistry results showed that PDGF-A was expressed in bronchial epithelium,alveolar epithelium and vascular endothelium of neonatal 1d rat lungs. The expression of PDGF-A in MVAD group were much lower compared with control group (P<0.01). Conclusions1. Vitamin A played an important role in lung development. Mild vitamin A deficiency led to the dysplasia of rat lung.2. MVAD led to immature development of prenatal lung and appearance of atelectasis and emphysema in neonatal rat lung that resulted from the immature typeâ…¡alveolar epithelial cells and deficiency of collagen fibers and elastic fibers.3. MVAD led to the down-regulated expression of PDGF-A which might be involved in the mechanism of lung hypoplasia.