Imaging And Anatomical Research Of The Related Structures Of Fetal Embryonic Cerebrospinal Fluid System

Background:The birth of malformed children is a heavy burden to families and society.Accordingly,the birth rate of defective children in China is as high as 4-6% of the total births,which indicates that there are 800-1.2 million malformed children have been born for each single year.Central nervous system malformations are common neonatal malformations with an incidence of about 3%-4%,and the incidence of such malformations is higher in cases of spontaneous abortion.Ventriculomegaly(VM)is a common developmental malformation of the ventricles in fetal central nervous system developmental anomalies.The possible mechanisms causing fetal cerebral development malformations may be:(1)obstruction of the cerebrospinal flow(CSF);(2)hypersecretion of the CSF;(3)defective filtration of the CSF;(4)and altered development of the intracranial architecture.Monitoring the changes during the development of the cerebral ventricles can further evaluate the development of the fetal brain.Nonetheless,to minimize diagnostic errors,it is essential to clarify the characteristic regularity of the ventricular morphological changes at different gestational ages.Cerebrospinal fluid(CSF)features its functions of protecting and cushioning the central nervous system(CNS),supporting nutrition and removing metabolites for the CNS,and thus maintaining the balance of the CNS.The CSF is mainly produced by the cerebral ventricular choroid plexus(CHP),while the ependymal epithelial and the capillaries produce the rest small amount.The CSF circulation starts initiates from the lateral ventricle,the CSF which produced by the lateral ventricle flows to the third ventricle through the interventricular foramen,and then merges with the CSF produced by the third ventricle,subsequently enters the fourth ventricle through the aqueduct.Following that,the CSF then pours into the subarachnoid space through the median foramen and the lateral foramen,and flows alongside the subarachnoid space,penetrates into the dural sinus through the arachnoid granules,and finally flows back into the blood circulation.Whenever the CSF flow is blocked,it eventually leads to hydrocephalus.Up to date,it was commonly recognized that the power sources of the CSF: arteriovenous and cardiac pulsatile movements;respiration;and the body positions.More recently,increasing research suggested that the myodural bridge(MDB)acts as one of the power sources of the CSF circulation as well.Since the CHP contributes the most to the production of CSF,the establishment of CSF circulation is mainly regulated by the development of the CHP.However so far,the information regarding anatomical and functional development of human CHP and the whole CSF circulation system remains limited due to the difficulties for sample collection etc.The present study mainly focused on the developmental regularities of fetal CSF circulation system,as well as the proteomic factors regarding the functional establishment of the CSF,aiming to elucidate the developmental regulations of the human fetal CSF system,which has a significant clinical outcome.Part 1:Ultrasonic imaging research of the developmental regularity of fetal CSF related structures: the regularly changes of the ventricular index monitored by ultrasoundObjective: 1)Monitoring the fetal ventricular changes as GA increases by ultrasound,and then analyzes the regularity of fetal central nervous system development with gestational age.2)To establish an improved diagnostic indicative index reference for ultrasound examination of the fetal cerebral ventricles based on the morphological characteristics throughout fetal nervous system development.Materials and methods: Key ultrasonic morphological indicators of fetal ventricular development,which includes frontal horn width(FHW),occipital horn width(OHW),width of 3rd ventricle,cavity of septum pellucidum(CSP),width and length of 4th ventricle and thalamo-occipital distance(TOD)had been measured and analyzed collectively.All data of the indicators was collected on singleton pregnant woman between 16-39 weeks of gestational age(GA),between November 2017 and June 2021 at the Hospital.Results:1.The morphological changes of the lateral ventricles with GA:OHW and FHW showed a decreasing tendency with increasing GA in both of two research groups.Compared with the cross-sectional study,the trend of OHW and FHW changing with increasing GA in the cohort study was more obvious.2.The morphological changes of TOD with GA:In both research groups,TOD showed increasing tendency as GA increased.However,the increasing tendency of TOD was fair in cohort study,while the increasing tendency of TOD was weak in cross section study according to the r values3.The morphological changes of the 3rd and 4th ventricles with GA:In both of cross section and cohort studies,dimensions of 3rd ventricle,CSP,as well as 4th ventricle all showed a clear increment as GA increased.In cohort study,the tendencies of the same indicators(dimensions of 3rd,4th ventricle,and CSP),was more significant compared to the relative data in cross section study according to the r values.4.The FHW and TOD showed significant asymmetry during the pregnancyConclusion:1.The human brain primarily develops in fetal stages;CUS provides a convenient,safe and repeatable method to measure the ventricular dimensions in fetuses.2.The results of the present study revealed the morphological change regularities during the GA.At the same time,the data of the present study could be taken as an improvement and expansion to the current diagnostic index.Additionally,according to the data of the present study,TOD could be considered as an important clinical indicator for evaluating lateral ventricle development.3.In both research groups,the tendency with increasing gestation age was similar,the cohort study showing a more obvious trend for each index to change with the increasing gestation age.Part II:Developmental anatomical research of the fetal CSF systemObjective:To further study the anatomical regularity of fetal cerebral ventricular development with GA.To discover the developmental primitive point of human cerebral ventricular CHP in the early gestation.To explore the functional development of human cerebral structure in the early gestation by evaluating the expression levels of key related proteins.Materials and methods: A total of 10 fetuses with normal abortion(non-cerebral malformation factors)at 9-36 weeks of gestation were collected for the morphological and functional study regarding the human embryonic CSF system.Morphological staining and immunohistochemical stains were performed to elucidate the morphological and structural characteristic regularities of fetal embryonic CSF system development.Results:1.Fetal ventricular CHP epithelial cells developed with GA and showed certain developmental changes of both the cell types and morphology.2.The CHP epithelial cells in different ventricles developed systematically with an order in time,the CHP of the 4th ventricle developed first at 7-week of GA,followed by the lateral ventricle,the 3rd ventricle CHP developed at last.3.Since 7-week of GA,the expressions of functional proteins could be initially observed within fetal ventricular CHP epithelial cells,implying the functional maturation of fetal CHP epithelium.Conclusion:1.Both of the morphology and cell types of fetal CHP epithelial cells showed certain developmental regularities with the increase of GA.2.As the major regulator of CSF circulation,the fetal ventricular CHP epithelium showed a regularly functional maturation with the increase of GA.3.Both of the morphological and functional maturations of CHP started from 7-week of GA.Part IIIUltrasonic imaging study of the asymmetric development of fetal lateral ventriclesObjective: To explore the causative factors of asymmetric development of fetal lateral ventricles and its relative clinical significance.Materials & methods:1.72 pregnant women at 20-36 weeks of gestation voluntarily participated in this study.The indicators(OHW,FHW,TOD)were monitored by ultrasound and correlated with fetal position and other key factors to investigate the patterns of asymmetry between the two sides of the lateral ventricles and its clinical significance.2.A total of 10 fetuses with normal abortion(non-cerebral malformation factors)at 7-36 weeks of gestation were collected to elucidate the morphological and structural developmental regularities of fetal lateral ventricles.The differences in the morphology of the left and right lateral ventricles,as well as the expression levels of key proteins regulating the CSF circulation were observed and analyzed.Results:1.Amongst the ultrasound monitoring index factors of fetal lateral ventricles,the average values of OHW,FHW and TOD of the left side were statistically greater than those of the right side.Moreover,in the fetal position of the right occipital anterior,the data of left side FHW was statistically larger than the right side.In the fetal position of left occipital anterior and right occipital transverse,the data of left side TOD was statistically larger than the right side.2.There is no observable difference in the morphology of the CHP on both sides of the fetal lateral ventricles.Except AQP1,Na~~+-K~+-ATPase,KCNE and PCNA showed enhanced expression levels in left lateral ventricle.Conclusion:1.The development of fetal lateral ventricles showed an asymmetry during the GA.The index factors of FHW and TOD were statistically larger in the left side.2.For fetal ultrasonic examination,the fetal position of right occipital anterior is prior for FHW;the fetal positions of left occipital anterior and right occipital transverse are prior for TOD.3.The CHP of fetal lateral ventricles showed a balanced morphology and cell types during the development,despite of the asymmetry in ventricular sizes of left and right brain hemisphere.4.The functional asymmetry is consistent with the general asymmetry of fetal lateral ventricles.