Immunohistochemical characterization of epithelial cells in human lacrimal glands. II. Inflammatory and neoplastic lesions of lacrimal glands

Immunohistological Study of Palpebral Lobe of the Lacrimal Gland in Severe Dry Eyes Secondary to Stevens-Johnson Syndrome

PURPOSE

To detect the immunohistochemical changes in the main lacrimal glands of patients suffering from chronic ocular sequelae of Stevens-Johnson syndrome (SJS).

METHODS

Histological sections of biopsies from the lacrimal gland of three chronic SJS patients (mean age, 33 years; 2 males) with severe dry eye disease (Schirmer = 0 mm) were assessed using double immunofluorescence techniques. Changes in the expression of secretory proteins lactoferrin (Lf), lysozyme (Ly), aquaporin 5 (AQP5), S-100, and early apoptosis marker (Annexin V) were studied.

RESULTS

Different morphological expressions of secretory proteins were present in the three samples. One sample had maintained the immunoreactivity for Lf, Ly, S-100, similar to healthy controls. Two samples had significantly reduced immunoreactivity for anti-Lf, anti-Ly, and S-100, the weakest being in the sample with distorted lobular architecture and mild interlobular fibrosis. AQP5 had a distinct vesicular intracytoplasmic immunoreactivity suggesting defective trafficking and integration of the protein to the apical membrane. There was no S-100 immunostaining in the acinar or ductal epithelium, whereas interstitial nerve fibers scattered in the periacinar region showed reduced immunoreactivity for S-100. There was strong Annexin V immunoreactivity in the nuclei of epithelial cells in the majority of acinar and ductal epithelia of all the samples, with distorted nuclear morphology in one sample.

CONCLUSION

Defective trafficking of AQP5 and variable expression of Ly, Lf, S-100 are the notable findings in the lacrimal glands of chronic SJS patients along with signs of early apoptosis. It suggests that the palpebral lobe of the lacrimal gland is involved in the pathological processes occurring in the conjunctiva of SJS patients.

Histatin-1 Expression in Human Lacrimal Epithelium

Background

Study of human lacrimal cell biology is limited by poor access to tissue samples, heterogeneous cell composition of tissue and a lack of established lacrimal epithelial markers. In order to further our understanding of lacrimal cell biology, we sought to find a better marker for human lacrimal epithelial cells, compared to what has been reported in the literature.

Methods

We utilized human Muller’s muscle conjunctival resection (MMCR) specimens containing accessory lacrimal gland (ALG) and cadaveric main lacrimal gland (MLG) as sources of lacrimal tissue. Candidate markers were sought using human ALG tissue from MMCR specimens, isolated by laser capture microdissection (LCM). Affymetrix® analysis was performed on total RNA isolated from FFPE samples to profile transcription in ALG. MMCR tissue sections were assessed by immunofluorescence using antibodies for histatin-1, lactoferrin, E-cadherin (E-cad) and alpha-smooth muscle actin (ASMA). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis was performed to analyze the expression of histatin-1, E-cad and lactoferrin from cadaveric MLG.

Results

Histatin-1 is expressed in ALG and MLG, localizes to lacrimal epithelium, and to a greater degree than do other putative lacrimal epithelial markers.

Conclusions

Histatin-1 is a good marker for human lacrimal epithelium in ALG and MLG and can be used to identify lacrimal cells in future studies.

Myoepithelial Cells: Their Origin and Function in Lacrimal Gland Morphogenesis, Homeostasis, and Repair

Lacrimal gland (LG) is an exocrine tubuloacinar gland that secretes the aqueous layer of the tear film. LG epithelium is composed of ductal, acinar, and myoepithelial cells (MECs) bordering the basal lamina and separating the epithelial layer from the extracellular matrix. Mature MECs have contractile ability and morphologically resemble smooth muscle cells; however, they exhibit features typical for epithelial cells, such as the presence of specific cytokeratin filaments. Increasing evidence supports the assertion that myoepithelial cells (MECs) play key roles in the lacrimal gland development, homeostasis, and stabilizing the normal structure and polarity of LG secretory acini. MECs take part in the formation of extracellular matrix gland and participate in signal exchange between epithelium and stroma. MECs have a high level of plasticity and are able to differentiate into several cell lineages. Here, we provide a review on some of the MEC characteristics and their role in LG morphogenesis, maintenance, and repair.

Regulatory pathways in lacrimal gland epithelium

Tears are a complex fluid that continuously cover the exposed surface of the eye, namely the cornea and conjunctiva. Tears are secreted in response to the multitude of environmental stresses that can harm the ocular surface such as cold, mechanical stimulation, physical injury, noxious chemicals, as well as infections from various organisms. Tears also provide nutrients and remove waste from cells of the ocular surface. Because of the varied function of tears, tears are complex and are secreted by several different tissues. Tear secretion is under tight neural control allowing tears to respond rapidly to changing environmental conditions. The lacrimal gland is the main contributor to the aqueous portion of the tear film and the regulation of secretion from this gland has been well studied. Despite multiple redundencies in pathways to stimulate secretion from the lacrimal gland, defects can occur resulting in dry eye syndromes. These diseases can have deleterious effects on vision. In this review, we summarize the latest information regarding the regulatory pathways, which control secretion from the lacrimal gland, and their roles in the pathogenesis of dry eye syndromes.