Bone morphogenetic proteins(BMP) are closely associated with multiple organ damage and various factors leading to BMP signaling pathway disorders can cause many diseases.So research on the BMP signaling pathway during embryonic development and organ damage in the process of dynamic change and the interaction with the receptor regulation relationship will further explore the mechanism of functions of BMP and control its signal transduction activity which has important significance to prevent the onset of the disease.

Objective To investigate the ultrastructural alteration in brain tissues as well as the expression of bone morphogenetic protein(BMP) 4 and its effects on regulating myelination in the process of white matter injury development.Methods A total of 152 Sprague-Dawley newborn rats(3 days old) were randomly divided into white matter injury group(n=76) or control group(n=76).The white matter injury model was established by ligation of the right common carotid artery and hypoxic exposure(8% O2 and 92%N2),and samples were collected at 3d,7d,14d and 21d after operation.Morphological changes of the brain tissues were observed under a light microscope,while myelination was analyzed using a transmission electron microscope.The expression and location of BMP4 and myelin basic protein(MBP),a marker for myelination,was detected by immunohistochemistry staining,expression levels of BMP4 and MBP proteins were analyzed by Western blotting,and BMP4 mRNA expression was measured by real-time PCR.Results Observed under the light microscope,the cellular structure was clear,fibers arranged closely and orderly in the white matter of the control group.Whereas in the white matter injury group,sparse cells,loose mesh shaped white matter,and disorderly oriented fibers were observed.In the control group,myelin sheath had regular morphology,uniform density,and same thickness,observed using the transmission electron microscope.While in the white matter injury group,the myelin sheath was loosened,thinned,lamellar separated,and boundary obscured.Using immunohistochemistry staining,Western blot,and real-time PCR analyses,it was found that the protein and mRNA expression of BMP4 had no significant change with the increase of age in the control group,while it was rapidly increased with the extending of ischemic time in the white matter injury group.Comparing with the control group,the expression of BMP4 was significantly increased since 3d after operation in the white matter injury group(P<0.05),and the difference between two groups became more significant with the extending of ischemic time.The expression of MBP protein was analyzed by immunohistochemistry staining and Western blot,and a gradual increase was found in both groups with the increase of age.However,the expression of MBP protein was significantly decreased on 14d and 21d after operation in the white matter injury group compared with the control group(P<0.05).Conclusion Myelination disorders exists in white matter injury induced by ischemia-anoxemia.Meanwhile,the expression of BMP4 is significantly increased in the white matter injury group,indicating a possibility that BMP4 involves in the regulation of myelination disorders in white matter injury.