Expression changes and significance of ATP-binding cassette transporter B5 in pterygium

Background Limbal stem cells (LSCs) deficiency leads to many ocular surface diseases, such as pterygium and so on.ATP-binding cassette transporter B5 (ABCB5) is a recently discovered marker of LSCs.Understanding the expression changes of ABCB5 in pterygium tissue has an important clinical significance for pterygium. Objective This study was to investigate the expression changes of ABCB5 in pterygium tissue. Methods Thirty-seven pterygium tissue specimens were collected from primary pterygium patients who received pterygium surgery, and 22 normal conjunctival tissue specimens were obtained from the strabismus patients and retinal detachment patients during surgery in 474 Hospital of Chinese PLA from January 2015 to November 2015.Immunochemistry was employed to detect the expression and location of ABCB5 in the specimens, and the protein and mRNA expressions of ABCB5 were detected by Western blot and real-time fluorescence quantitative PCR, respectively.The results were compared between normal conjunctival tissues and pterygium tissue. Results ABCB5 protein was expressed in the cytoplasm and nuclei of stratified squamous epithelium of 22 normal counjunctival tissue specimens, especially in the basal layer cells, and showed obvious polarity in normal conjunctiva.In pterygium group, ABCB5 protein was positively expressed in 91.89% specimens (34/37) and the expression was absent in 8.11% specimens (3/37). The relative expression levels of ABCB5 protein were 0.90±0.31 and 0.59±0.41, and those of ABCB5 mRNA were 1.01±0.26 and 0.65±0.32 in the normal conjunctival tissues and pterygium tissue, respectively, showing significant differences between them (protein: t=-0.266, P=0.011; mRNA: t=-4.560, P=0.000). Conclusions Down-regulation of ABCB5 in pterygium indicates the decreasing and losing of LSCs, which may play an important role in the development of pterygium.ABCB5 may be a useful indicator for the prediction of development and recurrence of pterygium and has an important implication for treating evaluation, and it may also be a target for the management of pterygium. Key words: ATP-binding cassette transporters; Biomarkers/metabolism; Corneal limbus/cytology; Stem cells; Pterygium/pathology