维甲酸诱导腭裂发生中转化生长因子-β信号通路相关分子表达的研究

目的研究维甲酸诱导腭裂发生中转化生长因子-β信号通路相关分子的表达。方法采用器官体外培养法进行腭板培养,实验分为对照组和全反式维甲酸（all trans retinoic acid,ATRA）组。分别培养24h、48h、72h后,苏木索一伊红染色观察两组腭板在不同时间点的融合情况,原位末端转的凋亡,免疫组化检测各组腭板中caspase-9、转化生长因子-β3（transforming growth factor-β3,TGF-β3）．转化生长因子-β受体Ⅱ（transforming growth factor type-Ⅱ receptor,TGFβ RⅡ）、维甲酸核受体理（retirmic acid receptor α,RARα）、维甲酸核受体β（retinoi cacid receptorp,RARβ）及维甲酸X受体α（retinoi cacid X receptor α,RXRα）的表达。结果成功建立维甲酸诱导腭裂模型,培养24h、48h、72h后,对照组腭板的融合数分别为4个、8个、8个,而ATRA组未见腭板融合,差异具有统计学意义（P〈0.05）。与对照组相比,ATRA组凋亡率和caspase-9表达上升（P〈0．05）。ATRA能明显抑制TGFβRⅡ的表达（P〈0．05）,但对于TGF-β3的作用却较小。ATRA可明显上调RARD的表达,并抑制RXRa在间充质中的表达。结论ATRA可能通过诱导腭突间充质细胞的凋亡及转化生长因子-β信号通路相关分子和维甲酸受体的表达改变,而诱导腭裂形成。     

叶酸对小鼠腭突间充质细胞增殖的影响

目的:从细胞水平对维A酸致小鼠腭裂畸形作用和叶酸是否有拮抗维A酸的致畸作用及其机制进行研究。方法:给予孕鼠过量维A酸,诱导胚胎腭裂模型,不完全消化法提取孕期第14天、17天(GD14、17)的胚胎腭突间充质细胞(EPM cells)进行培养并鉴定细胞;采用四甲基偶氮唑盐(MTT)法检测加入不同浓度叶酸与未加入叶酸细胞增殖的情况。采用SPSS16.0软件包对数据进行统计学处理。结果:①在GD10、GD12管饲孕鼠50 mg/kg维A酸,可致胎鼠腭裂畸形;②不完全消化法提纯EPM细胞,纯度达到98%;③维A酸导致GD14的EPM细胞增殖受到抑制,20 μg/mL、40 μg/mL浓度叶酸可拮抗这种抑制作用。结论:①过量维A酸可致小鼠腭裂畸形,腭突间充质细胞增殖受抑制是其致畸机制之一;②叶酸可拮抗维A酸对小鼠GD14 EPM细胞增殖的抑制作用。     

Expression and function of patatin-like phospholipase domain-containing 2 in cleft palate induced by retinoic acid

Cleft palate is a common maxillofacial congenital malformation, and its mechanism still has not been fully illustrated. Recently, lipid metabolic defects have been observed in cleft palate. Patatin-like phospholipase domain-containing 2 (Pnpla2) is an important lipolytic gene. However, its effect on the formation of cleft palate remains unknown. In this research, we explored the expression of Pnpla2 in the palatal shelves of control mice. We also studied mice with cleft palates induced by retinoic acid and its effect on the embryonic palatal mesenchyme (EPM) cells phenotype. We found that Pnpla2 was expressed in the palatal shelves of both the cleft palate and control mice. Pnpla2 expression was lower in cleft palate mice than in the control mice. Experiments with EPM cells showed that knockdown of Pnpla2 inhibited cell proliferation and migration. In conclusion, Pnpla2 is linked to palatal development. We have indicated that low expression of Pnpla2 affects palatogenesis by inhibiting the proliferation and migration of EPM cells.     

维甲酸诱导小鼠腭裂发病机制的实验研究

目的 观察维甲酸（retinoic acid,RA)诱导胚鼠腭突发育的形态学变化，探讨胚鼠腭部转化生长因子（transforming growth factor,TGF)β1、TGFβ3、表皮生长因子（epidermal growth factor,EGF)及BCL2的表达在RA诱导腭裂发病机制中的意义。方法 采用显微镜观察胚腭的发育过程，原位杂交和免疫组化检测TGFβ1、TGFβ3、EGF及BCL2基因在胚腭中的表达。结果 RA引起双侧腭突的形成，使双侧腭突不能接触或接触后不能融合形成中嵴上皮带，以及可调控TGFβ1、TGFβ3、EGF及BCL2在鼠胚腭部的表达。结论 RA抑制中嵴上皮细胞（MEPM）增殖，引起双侧腭突的形成，诱导MEE细胞殿堂分化，使双侧腭突不能接触融合，而最终导致腭裂形成及TGFβ1、TGFβ3、EGF在鼠胚腭部表达的变化与RA诱导腭裂的形成密切相关。     

Inhibition of human embryonic palatal mesenchymal cell cycle by secalonic acid D: a probable mechanism of its cleft palate induction

OBJECTIVE: To assess the mechanism(s) of cleft palate induction by secalonic acid D (SAD) in human embryonic palatal mesenchymal (HEPM) cells and compare them with those evaluated in the murine embryonic palate. DESIGN: Effect of SAD on HEPM cell proliferation was studied by obtaining dose response curves for cell numbers, uptake of 3H-thymidine and the expression of proliferating cell nuclear antigen (PCNA). Effects of SAD on cell cycle were assessed by flowcytometry. Cell-labeling with 3H-glucosamine and immunoblot analysis were conducted to study SAD effects on the synthesis of glycosaminogycans (GAG) and the expression of fibronectin and tenascin, respectively. RESULTS: SAD induced a concentration-dependent decrease in HEPM cell number and 3H-thymidine uptake beginning at 0.1 microg of SAD/ml. Expression of PCNA and progression of cell cycle from G1 to S phase were inhibited following SAD exposure. Cell viability was significantly reduced only at 7.5 microg/ml of SAD or higher indicating that the reduction in cell numbers by SAD at lower concentrations is likely due to reduced proliferation and at higher concentrations due to both reduced proliferation and cell death. Synthesis of extra cellular matrix components (GAGs, fibronectin or tenascin) by HEPM cells, however, was not inhibited by SAD. CONCLUSION: The results of these studies confirmed those of our previous studies with mice and the MEPM cells that SAD may induce cleft palate by reducing numbers of palatal mesenchymal cells by inhibition of their proliferation thereby leading to a reduction in the size of the developing palate shelves.     

腭裂相关基因mcpr1在不同组织细胞中的表达

目的：初步探讨新基因mcpr1在腭突外胚间充质细胞、下颌突外胚间充质细胞、牙囊细胞等中的表达情况。方法：取妊娠12.5d的胎鼠第3代腭研究会外胚间充质细胞及实验室已成功培养的人牙髓细胞、牙周膜细胞、牙囊细胞及下颌外胚间充质细胞，利用已制备的MCPR1多克隆抗体，进行细胞免疫组织化学染色，分析MCPR1的表达情况。结果：腭寄突外胚间充质细胞组织块培养法培养，稳定传至3代，免疫组化结果示腭突外胚间充质细胞及人牙击膜细胞强阳性表达，在下颌突外胚间充质细胞，牙囊细胞及牙髓细胞表达较弱。结论：MCPR1在不同来源的细胞中广泛表达，但表达水平不同。进一步提示MCPR1可能参与不同组织器官的发生发展，在胚胎发育的不同时期具有不同的表达模式。     

C57BL/6N系小鼠腭裂模型的建立及扫描电镜观察

观察腭裂形成过程及腭突正常发育中形态发生、组织学变化。方法１６只妊娠１０天的Ｃ５７ＢＬ／６Ｎ系小鼠随机分为实验组、对照组、于ＧＤ１３＾１４,（１３ｄ１４ｈ略写为３＾１４以下类同）,ＧＤ１３＾３２,ＧＤ１４＾８,ＧＤ１４＾２２,ＧＤ１５＾８,ＧＤ１５＾２２,ＧＤ１６＾８剖腹取鼠头部标本分别做扫描电镜及ＨＥ染色。     

RNA干扰原代培养胚胎腭间充质细胞Smad2/3基因对atRA阻滞细胞周期作用的影响

目的：证实atRA可以通过Smad2/3作用于p21,从而导致胚胎腭间充质细胞周期受阻而出现腭裂。方法：原代培养胎鼠胚胎腭间充质细胞并进行鉴定。采用RNA干扰原代培养胚胎腭间充质细胞Smad2/3基因后,Western印迹检测Smad2/3、pSmad2、pSmad3和p21的蛋白表达水平及干扰后细胞周期的变化。采用SPSS11.0软件包对数据进行单因素方差分析和t检验。结果：经过免疫组化鉴定,证实原代培养C57BL/6N胎鼠腭突间充质细胞成功,并且Smad2/3siRNA可以有效干扰Smad2/3在原代培养MEPM细胞中的表达。Western印迹检测结果证实,Smad2/3siRNA可以通过敲减atRA诱导的Smad2/3表达增高现象,继而降低atRA诱导的p21表达增高现象。此外,Smad2/3siRNA在一定程度上降低了atRA诱导的胎鼠腭突间充质细胞G1期阻滞现象。结论：Smad2/3通过p21参与atRA诱导的胚胎腭突间充质细胞G1期阻滞现象。     

Collagen Membranes Adsorb the Transforming Growth Factor‐β Receptor I Kinase‐Dependent Activity of Enamel Matrix Derivative

Background: Enamel matrix derivative (EMD) and collagen membranes (CMs) are simultaneously applied in regenerative periodontal surgery. The aim of this study is to evaluate the ability of two CMs and a collagen matrix to adsorb the activity intrinsic to EMD that provokes transforming growth factor (TGF)‐β signaling in oral fibroblasts. Methods: Three commercially available collagen products were exposed to EMD or recombinant TGF‐β1, followed by vigorous washing. Oral fibroblasts were either seeded directly onto collagen products or were incubated with the respective supernatant. Expression of TGF‐β target genes interleukin (IL)‐11 and proteoglycan 4 (PRG4) was evaluated by real time polymerase chain reaction. Proteomic analysis was used to study the fraction of EMD proteins binding to collagen. Results: EMD or TGF‐β1 provoked a significant increase of IL‐11 and PRG4 expression of oral fibroblasts when seeded onto collagen products and when incubated with the respective supernatant. Gene expression was blocked by the TGF‐β receptor I kinase inhibitor SB431542. Amelogenin bound most abundantly to gelatin‐coated culture dishes. However, incubation of palatal fibroblasts with recombinant amelogenin did not alter expression of IL‐11 and PRG4. Conclusion: These in vitro findings suggest that collagen products adsorb a TGF‐β receptor I kinase‐dependent activity of EMD and make it available for potential target cells.     

Cleft palate formation after palatal fusion occurs due to the rupture of epithelial basement membranes

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces cleft palate and hydronephrosis in the mouse embryo. Cleft palate occurs due to failure in palatal grow, but the underlying mechanisms are unclear. We investigated the mechanisms of cleft palate development in TCDD-exposed mouse embryos. We administered olive oil (control group) or TCDD diluted in olive oil (40 μg/kg) via gastric tubes to pregnant mice on gestational day (GD) 12. Embryos of control and TCDD-exposed groups were removed from pregnant mice on GD 14 and GD 15, respectively. One mouse embryo from the control group had anteroposterior palatal fusion. Palatal fusion was observed in three TCDD-exposed mouse embryos. Palates of TCDD-exposed mice fused from the interior to the middle of the palates, while the palates were separated in the posterior region. The middle of the embryonic palatal shelves in TCDD-exposed animals was narrow and split at the fusional position. At this position, palatal and blood cells were dispersed from the palatal tissue and the epithelium was split, with a discontinuous basement membrane. The results suggest that decreased intercellular adhesion or insufficient tissue strength of the palatal shelves may be involved in the development of cleft palate following palatal fusion.     

Nucleofection is highly efficient for transfecting genes into murine embryonic palatal mesenchymal cells in primary culture

Non-syndromic cleft of the lip and/or palate is one of the most common birth defects in humans. Embryonic palatal mesenchymal (EPM) cells are an attractive source for investigating embryonic palatal development. In this study, we developed a highly efficient transfection method for murine EPM (MEPM) cells. MEPM cells were transfected with the plasmid pEGFP-N1 using two non-viral methods: nucleofection and lipofection. Nucleofection provided a much better rate of gene transfer than lipofection particularly in MEPM cells. The methylenetetrahydrofolate reductase (MTHFR) gene is an important candidate for involvement in the pathogenesis of this birth defect. The RNA interference plasmid of MTHFR was constructed and nucleofected into MEPM cells. Successful transfection resulted in a remarkable reduction in the expression of MTHFR. Taken together, the results indicate that nucleofection is highly efficient for MEPM cell transfection, and that this approach may be useful for investigating gene function in the process of palatogenesis.     

5,10‐Methylenetetrahydrofolate reductase single nucleotide polymorphisms and gene–environment interaction analysis in non‐syndromic cleft lip/palate

Non‐syndromic cleft lip/palate (NSCL/P) is a common congenital defect in Mexico. Periconceptional intake of folic acid (FA) may reduce the risk of this malformation. Although the 5,10‐methylenetetrahydrofolate reductase (MTHFR) enzyme participates in folate metabolism, several studies failed to find any association between NSCL/P and the MTHFR C677T and A1298C polymorphisms. However, interactions among NSCL/P, MTHFR gene polymorphisms, and FA intake have not been explored in Mexican populations. This case–control study included 132 patients with NSCL/P and 370 controls from Mexico City. Maternal FA consumption during pregnancy was examined, as were the MTHFR C677T and A1298C polymorphisms and gene–FA interactions. Maternal FA intake during the periconceptional period was lower in cases (1.5%) than in controls (13%), with the risk of delivering a child with NSCL/P lower in mothers who consumed FA (OR = 0.29, 95% CI: 0.19–0.44). In addition, the risk of NSCL/P was lower in children with the TT than the CC genotype of MTHFR C677T (OR = 0.39, 95% CI: 0.23–0.68), after Bonferroni correction and exclusion of stratification. No evidence of gene–FA interaction was found. These results indicate that maternal FA intake and the TT genotype of the MTHFR C677T polymorphism in children independently reduced the risk of NSCL/P in our population.     

atRA对C57BL/6N小鼠腭突间充质细胞周期分布的影响及其作用机制

目的：在全反式维A酸（all-trans retinoic acid,atRA）诱导建立腭裂小鼠模型的基础上,检测胎鼠体内胚胎腭突间充质细胞的周期分布,并检测相关周期蛋白的变化情况,为进一步阐明维A酸（retinoic acid,RA）诱导腭裂机制提供新的线索。方法：以atRA建立C57BL/6N胎鼠腭裂模型,采用流式细胞术及免疫组化检测小鼠胚胎腭突间充质细胞的周期分布,通过实时定量RT-PCR和Western印记法检测p21和pRb在胎鼠胚胎腭突间充质中的mRNA和蛋白表达水平。采用SPSS11.0软件包对数据进行单因素方差分析和t检验。结果：流式细胞术及免疫组化检测发现,在小鼠妊娠日（gestation day,GD）第10天时给予atRA,可以诱导胎鼠胚胎腭突间充质细胞在一定妊娠阶段出现G1期细胞周期阻滞,同时也使胎鼠胚胎腭突间充质内p21和pRb的表达水平出现改变。而妊娠第12天（GD12）时给予atRA则无此现象。结论：p21与pRb参与了GD10时给予atRA诱导组胎鼠胚胎腭突间充质细胞G1期阻滞的发生。     

腭裂相关基因mcpr1在小鼠腭突发育及腭裂发生中的表达研究

目的检测mcpr1基因的蛋白在正常腭突及小鼠腭裂模型腭突发育中的时空表达模式。方法实验组管饲含全反式维甲酸的植物油诱导建立小鼠腭裂模型,对照组小鼠管饲植物油。2组取胎龄12、13、14、16 d的胎鼠各3只,包埋切片,HE染色观察2组胎鼠腭部发育的形态学变化,免疫组织化学方法观察MCPR1蛋白在2组胎鼠腭突中的表达差异。结果成功建立小鼠腭裂模型。切片HE染色观察发现实验组双侧腭突体积较对照组小,两侧腭突未接触;而对照组腭突融合,腭骨形成。免疫组织化学检查结果表明对照组小鼠胎龄12 d时MCPR1蛋白在腭突上皮细胞呈强阳性表达;而实验组小鼠胎龄12 d时腭突间充质细胞内MCPR1蛋白的表达较强,实验组胎龄16 d小鼠仅在上皮细胞附近的间充质细胞中有阳性表达。同一时间点比较,MCPR1蛋白的表达在实验组均强于对照组（P〈0.05）。结论 MCPR1蛋白的表达变化随腭部发育存在时空表达差异。     

Sox4基因在小鼠腭突发育过程中的表达

目的 探讨Sox4基因在BALB/c正常小鼠与腭裂模型腭突胚胎上皮中的表达差异,初步研究该基因在腭突发育过程中的作用.方法 维甲酸诱导实验组BALB/c孕鼠,建立胎鼠腭裂模型,对照组孕鼠给予等量玉米油喂养.在GD13(gestation day 13)、GD14、GD15将各组孕鼠处死,获取胎鼠标本,应用免疫细胞化学方法检测Sox4蛋白在实验组及对照组胎鼠腭突中的表达.结果 实验组及对照组GD13-GD15腭突被覆的上皮中均为阳性表达,在GD13,二组腭突无明显形态差别.在GD14对照组中胚胎腭中线处可见腭突上皮开始接触融合,胚胎腭中线上皮带(medial epithelial seam,MES)表达阳性.GD14实验组中腭突未发生接触及融合.GD15对照组可见腭中线上皮带基本消失,MES部分消失,中线处为阳性,间充质中也可见阳性表达,实验组依然未发生融合,腭突末端被覆上皮呈阳性表达.用平均光密度值对 Sox4蛋白进行半定量检测得出,GD13实验组与对照组无明显差异, GD14实验组表达高于对照组,GD15对照组表达较高.组内比较对照组Sox4表达峰值出现在GD14,实验组相邻两组间对比无差异.结论 Sox4在腭裂与正常腭突中GD14-GD15的表达存在明显差异,在腭突融合期发挥调节作用.     

Conditioned Medium of Demineralized Freeze‐Dried Bone Activates Gene Expression in Periodontal Fibroblasts In Vitro

Background: Demineralized bone matrix (DBM) is used for the treatment of osseous defects. Conditioned medium from native bone chips can activate transforming growth factor (TGF)‐β signaling in mesenchymal cells. The aim of this study is to determine whether processing of native bone into DBM affects the activity of the conditioned medium. Methods: Porcine cortical bone blocks were subjected to defatting, different concentrations of hydrochloric acid, and various temperatures. DBM was lyophilized, ground, and placed into culture medium. Human gingiva and periodontal fibroblasts were exposed to the respective conditioned medium obtained from DBM (DBCM). Changes in the expression of TGF‐β target genes were determined. Results: DBCM altered the expression of TGF‐β target genes (e.g., adrenomedullin, pentraxin 3, KN motif and ankyrin repeat domains 4, interleukin 11, NADPH oxidase 4, and BTB [POZ] domain containing 11) by at least five‐fold. The response was observed in fibroblasts from both sources. Defatting lowered the activity of DBCM. The TGF‐β receptor type I kinase inhibitor SB431542 [4‐(4‐(benzo[d][1,3]dioxol‐5‐yl)‐5‐(pyridin‐2‐yl)‐1H‐imidazol‐2‐yl)benzamide] but not the inhibitor of bone morphogenetic protein receptor dorsomorphin, blocked the effects of DBCM on gene expression. Moreover, conditioned medium obtained from commercial human DBM modulated the expression of TGF‐β target genes. Conclusion: The findings suggest that the DBCM can activate TGF‐β signaling in oral fibroblasts.     

Deficient cell proliferation in palatal shelf mesenchyme of CL/Fr mouse embryos

How secondary palate formation is affected in the cleft lip genotype remains poorly understood. The purpose of this study was to analyze regional patterns of cell proliferation in CL/Fr mouse embryos with or without cleft lip. Pairs of palatal shelves were dissected at E13.5 from CL/Fr normal embryos (CL/Fr-N), CL/Fr embryos with bilateral cleft lip (CL/Fr-BCL), and a control strain of C57BL embryos (C57BL). The explants were examined histologically after 48 hrs of organ culture. Cell kinetics for proliferation in the palatal shelves was examined at E13.5 by the bromodeoxyuridine method in vivo. The CL/Fr-BCL palates fused as well as the CL/Fr-N palates in vitro. There were inter-group differences in the absolute number of BrdU-positive cells and the ratio of positive/(positive+negative) cells in the palate's mesenchyme (C57BL > CL/Fr-N > CL/Fr-BCL) and epithelium (C57BL > CL/Fr-N = CL/Fr-BCL). These findings indicate that a cleft palate follows reduced cell proliferation of secondary palatal mesenchyme in CL/Fr mice.     

Genetic background influences the capacity for medial edge epithelium disintegration and phenotype of cleft palate in TGFβ3 knockout mice

ObjectivesCleft palate is a frequent congenital craniofacial malformation of unknown etiology. Transforming growth factor (TGF) β3 is required for palatal shelf fusion. Although TGFβ3 knockout (KO) mice are widely used mouse models for cleft palate, cleft palate phenotypes differ among these mice. This study aimed to determine the effects of genetic background on the cleft palate phenotype in mice.MethodsWe produced TGFβ3 KO congenic mouse strains with five different genetic backgrounds. The phenotypes of the congenic strains were determined by visual examination. The capacity for disintegration of the medial edge epithelium (MEE) and basement membrane (BM) of palatal shelves of all five mouse strains was analyzed by using immunofluorescence staining after single palatal shelf suspension culture. The relationship between phenotype and disappearance of the MEE and BM was analyzed.ResultsAlthough the five congenic strains carried the same defective Tgfb3 gene, the fetal palate phenotypes differed among strains. The loss of the MEE cells and BM also differed with the genetic background, and the degree of such loss correlated with the cleft palate phenotype.ConclusionsThe cleft palate phenotype in mice is influenced by the genetic background, which governs the capacity for MEE and BM disintegration.     

Temporal and spatial expression of Pax9 and Sonic hedgehog during development of normal mouse palates and cleft palates in TGF-beta3 null embryos

Transforming growth factor-beta (TGF-beta3) gene disruption causes cleft secondary palate. Pax9 and Sonic hedgehog (Shh) genes are involved in the patterning of vertebrate embryonic tissues, including the facial skeleton. We investigated the expression of Pax9 and Shh genes during normal mouse palate development and in the developing cleft palates of TGF-beta3 null embryos. Whole mount in situ hybridization was conducted with use of Pax9 and Shh riboprobes for TGF-beta3 null, heterozygous and wild type mice at E12.5-E16.5. Histological analysis was processed by section in situ hybridization. In the wild type, Pax9 and Shh were expressed in the palate between E12.5-E15.5. Shh expression in the secondary palate was restricted to the rugae and the soft palate. Pax9 expression was predominantly in the palatal medial edge between E14.5 and E15.5. These patterns suggest that Shh and Pax9 may have different functions during palate development. In TGF-beta3 null mice, both genes expression patterns in the palate were different to those in wild type mice. In TGF-beta3 null mice, Pax9 expression was much reduced in the palatal medial edge at the critical time of palatal fusion (E14.5-E15.5). Shh expression in the palates of TGF-beta3 null mice was reduced throughout E12.5-E15.5, whilst Shh expression in heterozygous did not appear down regulated compared with the wild type. These results indicate that Pax9 and Shh expression are altered when the TGF-beta3 gene is deleted and suggest that Pax9 and Shh may be involved in the TGF-beta3 regulation of normal palatal fusion.     

腭发育不同时期维甲酸对腭突细胞增殖和凋亡的影响

目的研究维甲酸对小鼠腭突融合期细胞增殖和细胞凋亡的影响。方法在SPF级C57BL/6J近交系母鼠妊娠10 d和12 d给予维甲酸（RA）建立小鼠腭裂模型,利用BrdU免疫组化方法和脱氧核糖核苷酸末端转移酶介导的缺口末端标记法（TUNEL）检测胚胎15 d（即腭突融合期）小鼠腭突中细胞增殖及细胞凋亡的表达和分布。结果10 d给药组腭胚间充质细胞及腭中嵴上皮细胞中BrdU阳性细胞率和TUNEL阳性细胞率均低于对照组,12 d给药组和对照组BrdU阳性细胞率和TUNEL阳性细胞差异无统计学意义。结论维甲酸作用于腭发育的不同时期对腭突细胞增殖及凋亡水平有不同的影响,作用于腭突发生前期可引起腭间充质细胞增殖抑制、凋亡过度而发生腭裂,作用于腭突快速生长期可能影响腭中嵴上皮细胞的上皮间充质转化和迁移等其他转归形式。