Mechanism Of Vitamin A Nuclear Receptors On Keratinization In Meibomian Gland

Purpose: Chalazion is one of the most common eye disease in young children.It is well known that the blockage of meibomian gland ducts is the main cause leading to a chalazion.Previous studies showed that Chalazia were closely associated with hyperkeratosis of meibomian gland epithelia.However,the mechanism is unclear.Recent studies found that the hyperkeratosis of the epithelial cells had an association with Vitamin A(VA)deficiency.Our previous study found that the average serum vitamin A levels of children with chalazia were significantly lower than that of normal children.Further,we found that the meibomian gland epithelia of the MVAD rat existed hyperkeratosis in our preliminary experiment.So we speculate that VA deficiency may lead to abnormal expression of the genes involving in keratinization of meibomian gland via VA nuclear receptors.Methods: The marginal VA deficiency(MVAD)models were stabilished with Sprague–Dawley(SD)rats.Then,Morphological structurof meibomian gland was observed by HE staining.RARs and RXRs m RNA and protein expression amounts were detected by polymerase chain reaction(PCR),immunofluorescence and western blotting,respectively.MVAD models were established and randomly assigned to MVAD and vitamin A supplement(VAS).The protein expression level of CRABP2,FABP5 was detected by immunofluorescence con-focal technology.Illumina technology was used to sequence high-throughput genes in three groups.The differentially expressed genes were analyzedb by Gene Ontology(GO)enrichment.The target genes associated with hyperkeratosis were verified by q PCR.Results: The MVAD animal models can be established successfully and stably by classic vitamin A deficient diet.HE staining showed meibomian gland ductal epithelial was thinner(P < 0.05)and secretory cell nuclei was smaller(P < 0.01)in MVAD group.In addition,hyperkeratosis in the meibomian gland epithelium and keratinocytes in the duct obviously appeared in MVAD group.RXR-? showed highest m RNA amounts among all RA receptors.RXR-? showed overtly decreased m RNA amounts in animals with MVAD.In addition,compared with normal rats,MVAD rats had starkly lower RXR-? and RXR-? expression levels.The protein expression of CRABP2 and FABP5 was significantly increased in MVAD groups,and the relative expression level of CRABP2/FABP5 was significantly increased.The relative expression of CRABP2/FABP5 were decrease in VAS group.Illumina high-throughput gene sequencing and GO enrichment analysis of differentially expressed genes showed that Krt1,Krt7,Krt8,Krt10,Krt16 and Krt17 had the highest significance.Except for Krt17 was obvious up-regulated,other genes were down-regulated,in addition,Krt17 expression level were decreased in VAS by PCR verification.Conclusions: Vitamin A deficiency model using classic vitamin A deficient diet showed high stability and repeatability.The histological structure of meibomian gland in SD rats was highly similar to that of human's,which was suitable for the basic research of human meibomian gland diseases.MVAD causes excessive maturation of meibomian gland acinar cells,and the hyperkeratosis may be regulated by genes associated with keratinization.VA regulated the Krt gene level by the relative expression of CRABP2/FABP5 and RXR-? signaling pathway,which is the main mechanism for VA to regulate the normal keratinization process of meibomian gland epithelium.f...