Study on the role of FAK/Twist1 in skull and dura mater during brain growth and development in SD rats
Objective To investigate the growth and development of skull in rapidly growing SD rats and it's relationship to FAK-Twist1 signaling pathway in the skull and dura mater.Methods We selected young rats and started from 1 week after birth to document the cranial length and cranial width using a soft ruler.An electronic scale and electronic balance were used to weigh the body weight and brain weight of rats.A graduated cylinder was used to weigh the volume of brain tissue.Western blotting was performed to detect the expression changes of FAK in the skull and Twist1 in the dura mater.Immunohistochemistry and immunofluorescence were used to observe the cell morphology of the skull and dura mater tissues and the expression differences of FAK-Twist1 in different parts.Results(1)The cranial length and width of the rat skull increased gradually from 1 to 7 weeks(Fcraniv length=420.20、Fcranial width=47.27,both P＜0.001).Compared with the first week,the length and width of the skull increased significantly in the second week(all P＜0.05),and the two lines increased by 94.4％and 90.0％of the whole skull development(1-12 weeks)respectively in the seventh week;(2)The body weight and brain weight of rats increased gradually from 1 to 7 weeks(Fbody weight=485.20、Fbrain weight=126.00,both P＜0.001).Compared with the first week,there was a significant increase in body weight and brain weight in the second week(all P＜0.05).In the seventh week,body weight and brain weight increased by 60.4％and 51.2％of the whole development respectively;(3)The brain volume of rats increased gradually from 1 to 7 weeks(F=852.80,P＜0.001),rapidly from 1 to 3 weeks,and relatively slowly after 3 weeks.Compared with the first week,the brain volume increased by 60.45％of the whole development in the seventh week;(4)The results of WB showed,at weeks 1-7,the expression of FAK in the skull tissue gradually increased(F=15.80,P＜0.001),and FAK was significantly increased in week 7 compared with week 1(P＜0.01).FAK in the dura mater tissue showed a trend of first decreasing and then increasing,reaching its highest value in week 4 compared to week 1,with statistical significance(P＜0.05).The correlation coefficients between FAK expression level and cranial length and cranial width were 0.95 and 0.96,respectively(both P＜0.001),showing positively correlated relationships;(5)Cranial suture observation results showed that the skull growth of neonatal SD rats was mainly longitudinal at the 1st,4th and 7th week after birth,and cranial suture was gradually clear and completely closed at the 7th week;(6)The results of immunocombination and immunofluorescence showed that Twist1 was mainly expressed in the dura,the highest expression in the first week,and then gradually decreased(Fhistochemistry=22.10,Ffluorescence=36.82,both P＜0.01).FAK was mainly expressed in the skull,and its expression level was decreased at week 4 compared to week 1(P＜0.01),and then gradually increased.Conclusions From 1 to 7 weeks after rats birth,the expression of FAK in the skull and dura is positively correlated with the growth and development of the skull,while the expression of Twist1 in the skull and dura decreases with the growth and suture closure of the skull.FAK/Twist1 in the skull and dura may jointly regulate the growth and development of the skull and suture closure of the young rat.
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