| Sj gren syndrome (SS) is a chronic autoimmune disease that mainly involves thesalivary and lacrimal glands. It could be classified into secondary sj gren syndrome (sSS) andprimary sj gren syndrome (pSS) according to other organs suffered or not. It has been studiedthat the incidence of SS is about1%and the ratio of male to female is1:9. According to the2007International Dry Eye Disease Workshop (DEWS): inflammation of the ocular surfaceand hyperosmolar of tear film are key factors in the onset and development of dry eye.Sj gren’s syndrome belongs to aqueous-deficient dry eye according to the pathology of dryeye.Recent years, many mouse models have been designed to investigate the mechanism ofdry eye. Although the animal model showed decreased tear secretion and damaged ocularsurface epithelium, the unstable and complex processes make them not perfectly mimic thecharacteristic of human dry eye, which is chronic, aggravated and repeated onset. If there isan animal model that could mimic human dry eye and show a chronic process so thatresearchers could study the mechanism of dry eye at different stages, it may be helpful toprevent, diagnose and treat dry eye and provide an useful animal model for clinical drugresearch.Non-obese (NOD) mouse is an animal model of autoimmune diabetes. It could developepancreatitis spontaneously because of nineteen diabetes susceptibility loci (named Idd) on thechromosome. Although it could develop dry eye, it could not be reasoned from SS because ofdiabetes. It has been reported that two of the nineteen chromosomal intervals (Idd3and Idd5,lied in No.3and No.1chromosome, respectively) are correlated with sialadenitis. Cha et al.applied C57BL/6J mouse and NOD mouse cross and then intercross till getting the congenicmouse that carrying Idd3and Idd5at the same time, named C57BL/6.NOD-Aec1Aec2mouse.Nguyen et al. studied the salivary glands of C57BL/6.NOD-Aec1Aec2mouse and found it destroyed with aging, accompanying an increased expression of inflammatory cytokines. It isconsidered to be an ideal mouse model of SS. However, histopathological changes of theocular surface in this mouse have not been studied comprehensively at present. So the studywas performed in the following three parts:Part1. Evaluation of the ocular surface signs of dry eye in C57BL/6.NOD-Aec1Aec2mouseIn order to investigate the changes of dry eye signs in this SS mouse with aging, weapplied fasting blood-glucose testing, Schirmer I test I (SIt I) and ocular surface staining atthe age of the fourth, the eighth, the twelfth, the sixteenth, and the twentieth week inC57BL/6.NOD-Aec1Aec2mouse (as experimental group) and C57BL/6J mouse (as controlgroup) orderly. Results in this study revealed that:1. The differences of fasting blood valuebetween two group at each time point was not significant (P>0.05).2. The scores offluorescein and lissamine green staining were not significant between the two group at the ageof4week (P>0.05), and tear secretion was not significant at8-week age (P>0.05).3.Decreased tear secretion and increased scores of ocular surface staining were observed inexperimental group with aging (P<0.05). Corneal epithelial cells dropped gradually andpeaked at16week-age, and positive staining of central corneal epithelium disappeared at20week-age. No significant changes were observed in C57BL/6J mouse with aging (P>0.05).Part2. Evaluation of the changes of histopathology of ocular surface inC57BL/6.NOD-Aec1Aec2mouseUsing hematoxylin-eosin (H&E) staining, periodic acid-schiff (PAS) staining and scanelectron microscopy observation, we measured the thickness of central corneal epithelium andnumber of conjunctival goblet cells, accessed the structure of lacrimal gland and cornealepithelium at each time point of the two group. Results in this study revealed that:1. Centralcorneal epithelium was consisted of four to five layers of cell and cells arranged orderly in thetwo group at the age of4week. Lacrimal gland also showed a normal structure withoutlymphocyte infiltration. Many microvilli arranged regularly on the surface of cornealepithelial cells of the two group at the age of4week. The thickness of central cornealepithelium and number of conjunctival goblet cells were not significant between two group at the age of8week (P>0.05).2. From12week on, corneal epithelial cells began to drop,thickness of central corneal epithelium and number of conjunctival goblet cells decreasedgradually with aging in experimental group(P<0.05). Lymphocytes infiltrated into thelacrimal gland at12week-age, and duct and acinar cells were destroyed and replaced bylymphocytes completely at the age of16week in C57BL/6.NOD-Aec1Aec2mouse.Decreased microvilli and dropped epithelium cells were also observed with aging in SSmouse, and collagenous fibers of the central corneal were exposed after epithelial cellsdropped completely at the age of20week. No changes occurred in C57BL/6J mouse at alltime points (P>0.05).Part3. Evaluation of the pathogenesis of dry eye in C57BL/6.NOD-Aec1Aec2mouseImmunohistochemistry(IHC) and semi-quantitative reverse transcription polymerasechain reaction (RT-PCR) were applied to detect the relative expression of interleukin-17(IL-17) and forkhead box protein3(Foxp3+) in lacrimal gland in the study. Results in thispart revealed that:1. The differences of relative expression of IL-17and Foxp3+in thelacrimal gland were not significant between the two group at the age of4week with IHC(P>0.05), while C57BL/6.NOD-Aec1Aec2mouse showed a gentle higher expression thanC57BL/6J mouse with RT-PCR (P<0.05).2. From12week age on, the relative expression ofIL-17and Foxp3+in the lacrimal gland of C57BL/6.NOD-Aec1Aec2mouse increasedgradually (P<0.05) both in IHC and semi-PCR with aging. IL-17showed cytoplasmic andextracellular location, while Foxp3+showed nucleus location. No significant changes wereobserved from4week to20week in C57BL/6J mouse (P>0.05).We concluded that:1. C57BL/6.NOD-Aec1Aec2is an ideal mouse model for studyingthe mechanism of human sj gren syndrome because it could mimic the onset anddevelopment of human pSS spontaneously and aggravated with aging.2. Immuneimbalance due to highly expression of IL-17and inability of Treg cell to suppress IL-17in thelacrimal gland may be a potential reason for dry eye in C57BL/6.NOD-Aec1Aec2mouse. |
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