Nerve terminals and epithelial cell variety in the human lacrimal gland

Improvement of radiotherapy-induced lacrimal gland injury by induced pluripotent stem cell-derived conditioned medium via MDK and inhibition of the p38/JNK pathway

Radiation therapy is the most widely used and effective treatment for orbital tumors, but it causes dry eye due to lacrimal gland damage. Induced pluripotent stem cell-derived conditioned medium (iPSC-CM) has been shown to rescue different types of tissue damage. The present study investigated the mechanism of the potential radioprotective effect of IPS cell-derived conditioned medium (iPSC-CM) on gamma-irradiation-induced lacrimal gland injury (RILI) in experimental mice. In this study, we found that iPSC-CM ameliorated RILI. iPSC-CM markedly decreased radiotherapy induced inflammatory processes, predominantly through suppressing p38/JNK signaling. Further signaling pathway analyses indicated that iPSC-CM could suppress Akt (Protein Kinase B, PKB) phosphorylation. High levels of midkine (MDK) were also found in iPSC-CM and could be involved in lacrimal gland regeneration by promoting cell migration and proliferation. Thus, our study indicates that inhibiting the p38/JNK pathway or increasing the MDK level might be a therapeutic target for radiation-induced lacrimal gland injury.

Duct system of the rabbit lacrimal gland: structural characteristics and role in lacrimal secretion

PURPOSE

To develop a nomenclature for the lacrimal duct system in the rabbit, based on the anatomic and structural characteristics of each duct segment, and to provide RT-PCR and immunofluorescence data to support the notion that the duct system plays important roles in lacrimal function.

METHODS

Paraffin-embedded lacrimal glands (LGs) were stained with hematoxylin and eosin (H&E) and evaluated with a stereomicroscope. Cryosections of LG were stained with cresyl violet, and acinar cells and ductal epithelial cells were isolated from each duct segment by laser capture microdissection (LCM). mRNA levels from these cells were analyzed by real-time RT-PCR. Standard protocol was followed for immunofluorescence detection of ionic transporters.

RESULTS

The lacrimal duct system was divided into six segments on the basis of morphologic characteristics: the intercalated, intralobular, interlobular, intralobar, interlobar, and main excretory ducts. Although the morphologic features change incrementally along the entire duct system, the gene expression of ionic transporters and aquaporins, including AE3, AQP4, AQP5, CFTR, ClC2gamma, KCC1, NHE1, NKAalpha1, NKAbeta1, NKAbeta2, NKAbeta3, and NKCC1 varied greatly among duct segments. Immunofluorescence results were generally in accordance with the abundance of mRNAs along the acinus-duct axis.

CONCLUSIONS

Most LG research has focused on the acinar cells, with relatively little attention being paid to the lacrimal ducts. The lack of knowledge regarding the lacrimal ducts was so profound that a precise nomenclature had not been established for the duct system. The present data establish a nomenclature for each segment of the lacrimal duct system and provide evidence that ducts play critical roles in lacrimal secretion.

Connections between the lacrimal gland and sensory trigeminal neurons: a WGA/HRP study in the cynomolgous monkey

The sensory innervation of the lacrimal gland (LG) in the cynomolgous monkey was studied using the retrograde wheat germ agglutinin/horsereadish peroxidase (WGA/HRP) tracer technique. A small solidified piece of WGA/HRP was implanted in the LG. Labelled sensory first-order neurons were found in the ipsilateral trigeminal ganglion (TG) and in the ipsilateral mesencephalic trigeminal nucleus (MTN). The distribution of labelled TG neurons was restricted to ophthalmic and maxillary ganglionic parts. Sensory innervation of LG by primary afferents is not only restricted to TG; an MTN involvement has also been found. This may imply that there is a central sensory role in the production and release of tears.

[Dry eye disease as a complex dysregulation of the functional anatomy of the ocular surface. New concepts for understanding dry eye disease]

INTRODUCTION

Dry eye disease is a disorder of the tear film that results in epithelial damage and in a disruption of the normal homeostasis at the ocular surface. It is widespread and causes symptoms ranging from discomfort to blindness.

METHODS

A review of the existing literature was used to compare different past and recent concepts for the understanding of dry eye disease with a focus on aspects of the integrating functional anatomy of the ocular surface.

RESULTS

The understanding of the pathogenesis of dry eye disease has proceeded from the mere recognition of a lack of tears to a consideration of their quality and to the concept of wetting of the ocular surface. However, several other aspects as epithelial differentiation, innervation, hormonal status or immune protection contribute to the intact functional anatomy of the ocular surface. Recently it has been recognized that immunologically regulated mechanisms of inflammation represent a primary or secondary pathogenetic factor for dry eye disease. This is conceivably regulated by the cells of the physiological mucosal immune defence system, the eye-associated lymphoid tissue (EALT). Androgens represent an important trophic factor for the ocular surface and their deficiency predisposes to inflammation.

CONCLUSION

Dry eye disease represents a complex dysregulation of the functional anatomy of the ocular surface that can start from different alterations (e.g. insufficient secretion, defects in wetting or innervation). Immune-based inflammation is able to interconnect and negatively reinforce these different pathomechanisms, resulting in a vicious circle.

Analysis of contact lens intolerance by exploring neuroanatomic integration of ocular surface defense

This paper reviews the anatomic, neuronal and mechanical factors that affect contact lens wear, and outlines several areas where compromised ocular surface defense arising from dysfunctional neuroanatomic integration might be the source of or a contributor to contact lens intolerance. Suggestions for clinical work-up by analyzing neuroanatomic integration are presented as a logical way to dissect this complex problem.

Histology, histochemistry and fine structure of the lacrimal and nictitans gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia)

The anatomical, histological, histochemical and ultrastructural characteristics of the lacrimal gland (LG) and nictitans gland (NG) of the armadillo Chaetophractus villosus were described. The histochemical and histological features of both glands in male and female adult animals were compared. The tissues were processed with conventional techniques for light and transmission electron microscopy. Fixed specimens were submitted to a battery of tests for glycans, glycosaminglycans, glycoconjugates, proteins, and lipids. The LG of the armadillo may be considered within the set of glandulae lacrimales superior in which primates, carnivores, perisodactyls and artiodactyls are included. The localization of the NG was similar to that of other mammals. Lacrimal and NG were histologically and histochemically identical. The secretory endpieces consisted of three cell types: (1) Mucous cells (MC) with different types of mucous secretory granules with neutral and sialic acid-containing glycoconjugates (GCs). (2)Seromucous cells (SMC) showing a variety of moderately electron dense secretory granules with flocculent material with carboxylated acidic, neutral, and sialic acid-containing GCs. Intercellular canaliculi with junctional complexes and basolateral intercellular spaces were frequent. (3) Serous cells (SC) with electron dense secretory granules. Histochemically, they showed the strongest reaction for proteins and neutral, weakly acid and carboxylated acidic GCs. The epithelium of the intra- and inter-lobular excretory ducts showed secretory activity, junctional complexes, and wide basolateral intercellular spaces with lateral folds. The endpieces and ducts were surrounded by myoepithelial cells. The stroma was characterized by fenestrated endothelium, unmyelinated axons, and abundant plasma cells. MC, SMC, and the duct system were richly innervated by hypolemmal nerve terminals.

Effect of a somatostatin analogue (SMS 201-995) on tear secretion in rats

PURPOSE

In this study we investigated the effect of a somatostatin analogue, octreotide, (SMS 201-995) on tear secretion in rats.

METHOD

The animals were anaesthetized intraperitoneally (ip) with urethan (1.2 g/kg) The drugs were injected subcutaneously (sc.). Tear samples were collected by folding a 5 mm section of the Schirmer strip over the lower lid margin to absorb tear fluid from the lower conjunctival sac for 5 mm. Forty animals were divided into four groups (n = 10). Group I (control) received 1 ml of saline, group 2 received 100 microg/kg of SMS 201-995, group 3 received 50 microg/kg of acetylcholine (Ach), group 4 received 100 microg/kg of SMS 201-995 and 30 min later 50 microg/kg of Ach. At t = 0 the local anesthetic proparacain HCI was instilled onto the ocular surface to minimize reflex secretion. Baseline secretion was measured before administering the various treatments.

RESULTS

While Ach alone significantly increased tear secretion, SMS 201-995 reduced it compared to saline (control) (p<0.0001, p<0.001, respectively). SMS 201-995 combined with Ach decreased tear secretion compared to Ach alone (p<0.03).

CONCLUSION

SMS 201-995 significantly inhibits Ach stimulated tear secretion in rats.

Distribution pattern of nervous tissue and peptidergic nerve fibers in accessory lacrimal glands

PURPOSE

Demonstration of the distribution pattern of nervous tissue and the occurrence of neuropept human accessory lacrimal glands by means of immunohistochemical methods.

METHODS

Paraffin sections of tissue samples were incubated with antisera against protein gene product (PGP), S-100 protein (S-100), calcitonin gene-related peptide (CGRP) and substance P (SP). The immunoreactions were visualized using both species-specific secondary antibodies and a streptavidin-biotin-peroxidase complex (ABC method).

RESULTS

PGP- and S-100-immunoreactive nerve fibers were distributed in the entire intertubular stroma. In addition, myoepithelial cells, a few clusters of tubulus cells, groups of wandering cells, and scattered cells of the excretory duct system were S-100-immunoreactive. CGRP- and SP-immunoreactivity was found in a few nerve fibers in the intertubular glandular stroma with an association to secretory tubules, blood vessels, intralobular ducts and excretory duct.

CONCLUSIONS

These observations are in agreement with findings in the main lacrimal gland.

Differential distribution of neuronal markers and neuropeptides in the human lacrimal gland

BACKGROUND

The present study was undertaken in an attempt to broaden the spectrum of known neuronal markers and neuropeptides in the main lacrimal gland of the human by light-microscopic immunohistochemistry.

METHODS

Using antisera against the neuronal markers protein gene product (PGP) and S-100 protein (S-100), the distribution of nerve fibers in the human main lacrimal gland was studied. Vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and tyrosine hydroxylase (TH) were identified by their specific antisera.

RESULTS

The nerve fibers are distributed throughout the interstice between the glandular tubules. Associations were also found between nerve fibers and both the interlobular ductal system and blood vessels (mainly arterioles). Within the glandular lobules isolated groups of secretory cells stained positive for S-100 protein. Nerve fibers situated in the glandular interstice between the tubules showed predominantly positive immunoreactions for the neuropeptide VIP, while only very few fibers stained positive for CGRP, NPY and the catecholamine marker TH. Nerve fibers associated with interlobular blood vessels were mainly CGRP and NPY positive and stained only very rarely for VIP. The epithelia of interlobular ducts and excretory ducts were associated with CGRP-immunoreactive nerve fibers.

CONCLUSION

The neuropeptides identified in the lacrimal gland indicate the complexity with which a variety of biologic signals regulate and modulate the lacrimal gland.

Cell biology of the harderian gland

The harderian gland is an orbital gland of the majority of land vertebrates. It is the only orbital gland in anuran amphibians since the lacrimal gland develops later during phylogenesis in some reptilian species. Perhaps because it is not found in man, little interest was paid to this gland until about four decades ago. In recent years, however, the scientific community has shown new interest in analyzing the ontogenetic and morphofunctional aspects of the harderian gland, particularly in rodents, which are the preferred experimental model for physiologists and pathologists. One of the main characteristics of the gland is the extreme variety not only in its morphology, but also in its biochemical properties. This most likely reflects the versatility of functions related to different adaptations of the species considered. The complexity of the harderian gland is further shown in its control by many exogenous and endogenous factors, which vary from species to species. The information gained so far points to the following functions for the gland: (1) lubrication of the eye and nictitating membrane, (2) a site of immune response, particularly in birds, (3) a source of pheromones, (4) a source of saliva in some chelonians, (5) osmoregulation in some reptiles, (6) photoreception in rodents, (7) thermoregulation in some rodents, and (8) a source of growth factors.

Innervation and mast cells of the rat exorbital lacrimal gland: the effects of age

The distribution of nerves and mast cells was studied in the lacrimal glands of 3-5-, 14- and 24-month-old rats, using light microscopic histochemical and immunohistochemical techniques. In 14-month and, to a greater extent, in 24-month-old rats there were signs of chronic inflammation and patchy destruction of acinar, ductal and vascular tissue. The glands of the three different age groups contained acetylcholinesterase (AChE), vasoactive intestinal polypeptide (VIP)-, neuropeptide Y (NPY)-, calcitonin gene-related peptide (CGRP)-, tyrosine hydroxylase-, substance P- and the phosphoprotein B-50-immunoreactive nerves. B-50-immunoreactive nerves were distributed around acini, blood vessels and ducts, in a similar manner to VIP and AChE. Substance P- and CGRP-immunoreactive nerves were sparsely distributed in interlobular connective tissue and around ducts and blood vessels. Tyrosine hydroxylase- and NPY-containing nerves were found around blood vessels. The 3-5- and 14-month-old rats had a similar pattern of innervation, however, by 24 months there was a reduction in the number and intensity of immunoreactive nerves. The loss of nerves was particularly associated with damage to the gland. Mast cells were also found in the lacrimal, mostly associated with neurovascular tissue. These could be histochemically labelled with alcian blue/safranin or toluidine blue and were immunohistochemically labelled with histamine and serotonin. Substance P-, CGRP-, VIP- and NPY-immunoreactive nerves were found apposed to mast cells. A large increase in mast cells was observed in 24-month compared to 3-5-month-old rats and these were found throughout the acinar tissue. These results show that a decrease in innervation and also chronic inflammation, with mast cell infiltration, occurs in aged rats. These findings may be contributing factors to reduced tear output in aging.

Major ocular glands (harderian gland and lacrimal gland) of the musk shrew (Suncus murinus) with a review on the comparative anatomy and histology of the mammalian lacrimal glands

The Harderian gland of the musk shrew Suncus murinus is elongated anteroposteriorly from in front of the eye to behind the ear. The gland is divided into two portions: an anterior portion (A portion) and a posterior portion (P portion). The single secretory duct of the gland emerges from the anterior end of the P portion, receives several secretory ducts of the A portion during the course along it, runs around the ventral aspect of the eyeball, and finally opens into the anterior corner of conjunctival sacs. The two portions of the gland show a fundamentally similar histological structure, having a poorly developed intraglandular duct system and wide tubular alveoli. The quantity of lipid vacuoles and stromal connective tissue in the A portion is greater than in the P portion. The lipid vacuoles in both portions are surrounded by unit membranes, but their contents appear different. The lacrimal gland of the musk shrew is located along the ventral side of the P portion of the Harderian gland. The lacrimal duct emerges from its anterior end, runs around the ventral and anterior aspects of the ear, crosses the A portion of the Harderian gland, and finally opens at the posterior corner of conjunctival sacs. The lobules of the lacrimal gland comprise a branched duct system and terminal acini with two types of secretory cells: 1) acidic cells positive both for the periodic acid-Schiff reaction (PAS) and for Alcian blue (AB) and 2) neutral cells positive for PAS and negative for AB. Both cell types tend to make separate acini, but when present in the same acinus, the acidic cells occupy relatively peripheral positions in the acinus. Both cell types lack intercellular canaliculi. On the basis of the present study as well as previous descriptions in the literature, the author suggests that the mammalian lacrimal glands can be divided into two sets: 1) a Glandula lacrimalis superior with multiple secretory ducts associated with the upper eyelid and 2) a Glandula lacrimalis inferior with a single secretory duct opening into the lateral corner of the conjunctival sacs. These glands have a fundamentally similar histological structure; but in the rabbit, which possesses both sets of lacrimal glands, they are different. On the other hand, the secretory cells of lacrimal glands generally have no intercellular secretory canaliculi, which are characteristically present between the serous secretory cells of the salivary glands.

Nervous control of membrane conductance in mouse lacrimal acinar cells

Intracellular microelectrode recordings were made from superfused in vitro preparations of mouse lacrimal gland. The lacrimal acinar cell had a mean resting membrane potential of -44.1 +/- 0.5 mV and a mean input resistance of 3.5 +/- 0.15 M omega. Electrical field stimulation (FS) had similar effects to ACh applied by microionophoresis, both evoking a biphasic membrane hyperpolarization (up to 15 mV) accompanied by a reduction in input resistance. The equilibrium potential values (EFS and EACh) for the responses to brief duration FS and ACh ionophoresis ranged between -45 and -75 mV and depended on the time at which measurements were made following the onset of stimulation. Superfusion of ACh or adrenaline also caused membrane hyperpolarization and increased membrane conductance. Estimations of EFS and EACh made during prolonged periods of FS and ACh superfusion yielded mean values of -53.9 +/- 1.9 mV and -53.4 +/- 1.5 mV respectively. FS evoked a response in all preparations tested with maximal effects seen at 40 Hz frequency. The mean latency of the FS-evoked hyperpolarization (40 Hz) was 270 +/- 21 ms and that for the ACh ionophoretic response was 400 +/- 65 ms. Low frequency FS (0.5-5 Hz) also induced membrane hyperpolarization and responses to single shock stimuli were occasionally observed. The FS-evoked hyperpolarization was abolished following the blockade of nerve conduction by superfusion of either Na-free or tetrodotoxin-containing media. Effects of FS were not seen in the presence of atropine. Neostigmine potentiated the FS- and ACh-evoked hyperpolarizations.(ABSTRACT TRUNCATED AT 250 WORDS)

Histologic and immunohistologic comparison of main and accessory lacrimal tissue

Main and accessory lacrimal tissues from autopsy and biopsy specimens were compared histologically and immunohistologically. Formaldehyde-fixed, paraffin-embedded specimens were studied by light microscopy with hematoxylinand-eosin and PAS staining. Glutaraldehyde-fixed, Epon-embedded specimens were sectioned at 1 micron, stained with alkaline Giemsa, and studied by light microscopy. Specimens fixed in a solution of alcohol and acetic acid were stained by immunofluorescence techniques for lactoferrin, lysozyme, secretory component, and the immunoglobulins IgG, IgA, IgM, IgD, and IgE. The main and the accessory lacrimal tissues were identical histologically and had identical distributions of secretory products and immunoglobulin-containing plasma cells. The finding of myoepithelial cells in 1-micron sections of accessory lacrimal tissue indicates autonomic innervation in that tissue. This finding, in conjunction with the identical immunohistology, indicates a common source for unstimulated and stimulated tears.