Differential expression of annexins I and II in normal and malignant human mammary epithelial cells

Abstract. Collagen-binding proteins ( CBPs ) of rat mammary tumors are identical to Ca²⁺-binding annexins [49]. We have now isolated a protein of 38 kDa from the human mammary tumor cell line ALAB by collagen type I affinity chromatography as well as by extraction of calcium-binding proteins. The 38-kDa band of both preparations was identified as annexin II (calpactin I) by its reaction with an annexin II-specific monoclonal antibody in Western blot analysis. Annexin I (lipocortin I) was not detectable in these cells. Two other human cell lines, the SV40-transformed cell line SV3 and cell line HBL-100, both established from normal mammary glands, were also positive for annexin II and negative for annexin I.
In vivo expression of annexins was investigated by immunohistological staining of normal and malignant human mammary tissue. The annexin II-specific mAb reacted with normal and tumor parenchyme whereas the annexin I-specific mAb reacted with acini and ductal myoepithelium of the normal mammary gland but showed no reaction with tumor tissue. Immunolocalization studies also showed annexin II expression in both normal and tumor stroma while only tumor stromal cells were found to be reactive with the antibody against annexin I. The differential expression of annexins in normal and malignant human mammary tissue suggests special functions of these proteins in the mammary gland.     

Muscarinic acetylcholine receptor structure in acinar cells of mammalian exocrine glands

Characterization of muscarinic acetylcholine receptors in acinar cells from rat pancreas and lacrimal and parotid glands was achieved by binding of the reversible muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) and the specific alkylating reagent [3H]propylbenzilylcholine mustard (PrBCM) to intact acini or dispersed acinar cells. Binding studies with [3H]QNB showed that acinar cells from pancreas contain 26,400, from parotid 21,400, and from lacrimal gland 25,700 binding sites/cell. To assess molecular size of the receptor in each gland, acini were prepared by digestion with purified collagenase and singly dispersed acinar cells were prepared by a combination of digestion with crude collagenase, hyaluronidase, and alpha-chymotrypsin and divalent cation chelation using EDTA. Muscarinic receptors on acini or dispersed cells were covalently labeled with 5 nM [3H]PrBCM, solubilized directly in hot sodium dodecyl sulfate buffer, and resolved by polyacrylamide gel electrophoresis. When solubilized acini were electrophoresed, a major labeled peak was observed on gels along with a smaller peak of lower apparent molecular weight. For pancreatic acini, the apparent molecular weights of these peaks were 117,600 and 85,700; for parotid acini, 104,800 and 74,500; and for lacrimal acini, 87,200 and 63,100. Addition of muscarinic antagonists to the labeling medium abolished both peaks. When dispersed acinar cells were labeled, the larger peak was eliminated, and all radioactivity was concentrated in a single peak: 87,600 for pancreas, 78,000 for parotid gland, and 62,800 for lacrimal gland. Digestion of prelabeled acini with the mixture of enzymes used to produce dispersed acinar cells similarly shifted all radioactivity into this second peak. Limited digestion of acini or dispersed cells with 1 mg/ml of papain resulted in the disappearance of these higher molecular weight peaks and the appearance of a broad peak at Mr = 40,000. Cells of nonepithelial origin, IM-9 lymphocytes and NG108 neuroblastoma X glioma hybrids, also were labeled with [3H]PrBCM and electrophoresed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intracellular distinction between peroxidase and catalase in exocrine cells of rat lacrimal gland: a biochemical and cytochemical study.

The lacrimal gland (Glandula orbitalis externa) of rat contains both peroxidase and catalase and was used as a model for biochemical and cytochemical distinction between peroxidase and catalase. Both enzymes were isolated by ammonium sulfate precipitation from tissue homogenates, and the effects of fixation with glutaraldehyde and various conditions of incubation were investigated colorimetrically using DAB as hydrogen donor. The lacrimal gland peroxidase is strongly inhibited by glutaraldehyde treatment. In contrast, for catalase the fixation with glutaraldehyde is the prerequistie for demonstration of its peroxidatic activity. The maximal peroxidatic activity was obtained after treatment of catalase with 3% glutaraldehyde, higher concentrations being inhibitory. For lacrimal gland peroxidase, the maximal rate of oxidation of DAB is at pH 6.5, whereas for catalase it is at pH 10.5. The optimal concentration of H2O2 for lacrimal gland peroxidase is at 10(-3)M and for peroxidatic activity of catalase at 10(-1)M. These optimal conditions obtained biochemically were applied to tissue sections of rat lacrimal gland. After the fixation of tissue with a low concentration of glutaraldehyde and incubation in the DAB medium at neutral pH containing 10(-3)M H2O2 (Peroxidase medium), the reaction product was localized in the cisternae of the rough endoplasmic reticulum, in elements of the Golgi apparatus, and in secretory granules. After the fixation of tissue with 3% glutaraldehyde and incubation in the DAB-medium containing 10(-1)M H2O2 and at pH 10.5 (catalase medium), the staining in the endoplasmic reticulum, the Golgi-apparatus and in secretory granules was completely inhibited and reaction product was localized exclusively in small (0.2-0.5 mu) particles similar to small peroxisomes described in various other cell-types.     

Human neoplastic submandibular intercalated duct cells express an acinar phenotype when cultured on a basement membrane matrix

Abstract. Culture of the human neoplastic submandibular gland intercalated duct cell line, HSG, on the basement membrane extract Matrigel induces dramatic morphologic changes and cytodifferentiation. Transmission electron microscopy demonstrated an acinar cell phenotype with polarized cells containing a well-developed Golgi apparatus, multiple microvilli-like projections from the apical surfaces into a lumenal-like area, and numerous granule-like organelles. Amylase, an acinar cell marker, was detected by both immunocytochemical and Northern blot analyses. A 50% reduction in [³H]thymidine incorporation by cells cultured on Matrigel, as compared to cells cultured on tissue culture plates, confirmed the differentiated phenotype of the cells. Multiple components of Matrigel appear to contribute to the morphologic differentiation of the HSG cells since antibodies to both laminin and collagen IV, as well as the lamininderived bioactive peptide containing SIKVAV, have potent inhibitory effects on HSG cell organization on Matrigel. Collectively, these data indicate that culture of HSG cells on Matrigel is a useful model to study salivary gland acinar development.     

Carbonic anhydrase isozyme VI in rat lacrimal gland

Using monoclonal antibody specific to rat carbonic anhydrase isozyme VI (CA VI), the isozyme was localized in the lacrimal gland. A minority of acini (less than 10% of the total) contained a few immunoreactive acinar cells. Enzyme histochemistry indicated that the CA VI-positive cells were the only cells possessing CA in the lacrimal acini. In the acinar cells, the reaction product for CA VI was distributed in the secretory granules and cytosol between secretory granules. Except for mitochondrial enzyme (CA V) activity, the intracellular distribution of enzyme activity was similar to that of CA VI immunoreactivity, suggesting that rat lacrimal acinar cells contain only CA VI and CA V. CA VI in the secretory granules was discharged into the acinar lumen and is considered to carry out its function on the surface of the conjunctiva and cornea. The cytosolic CA VI may function in situ and be involved in electrolyte and water secretion by the acinar cells. Polyclonal antibody to rat erythrocyte CA (CA I and CA II) stained only the interlobular ducts. In contrast, all the ductal elements exhibited CA enzyme activity. This discrepancy between immunohistochemistry and enzyme histochemistry suggests the presence of CA isozyme(s) other than CA I, CA II and CA VI in the lacrimal duct.     

Age-dependent changes in cell proliferation and cell death in the periodontal tissue and the submandibular gland in mice: a comparison with other tissues and organs

This study investigated the age-dependent changes in the number of BrdU- and TUNEL-positive cells in murine gingival tissue and submandibular gland, and compared the findings with those in other tissues and organs. The cell proliferative activity was decreased after 20 weeks of age in epithelial cells of the gingiva, tongue, buccal mucosa and skin. A decreased cell proliferative activity was also associated with aging in the liver and kidney parenchymal cells. Meanwhile, cell death showed peculiar changes in gingival subepithelial tissue, and mucous and serous acini of the submandibular gland. An increase of TUNEL-positive cells was demonstrated in gingival subepithelial tissue after 20-week-old of age. A significant increase of TUNEL-positive cells was also found in the mucous acinar cells in the 20-week-old mice and in the serous acini after 20 weeks. The fluctuation in the number of TUNEL-positive cells in the subepithelial tissue of the skin, and BrdU- and TUNEL-positive staining ratios in the liver was smaller than that in other tissue and organs throughout life. This study may provide useful information for better understanding the influence of aging on the functional alteration that occurs in the gingival tissue and submandibular gland of the elderly.     

An experiment of the combined treatment of traditional Lei-huo-jiu therapy with Chinese medicine for the lacrimal gland of Sjögren’s syndrome

This experiment chooses nonobese diabetic (NOD) mouse as the animal model of Sjögren’s syndrome and investigates the morphologic changes, the expression of inflammatory factors and growth factors of this mouse’s lacrimal gland in response to a combined treatment of traditional Lei-huo-jiu therapy alone and in combination with Chinese medicine. The methods were to (1) use a morphological approach to directly observe pathological changes of the lacrimal gland in response to combined treatment and (2) to detect the level of tumor necrosis factor (TNF)-α, interleukin (IL)-1, and nuclear factor kappa B (NF-κB) in lacrimal gland tissue caused by the combined treatments using a immunohistochemical approach. There is a reduction of the mast cell’s degranulation and modulation of the level of cytokines in TNF-α, IL-1, and NF-κB in the combined therapy group. The combined treatment of traditional Lei-huo-jiu therapy with Chinese medicine can improve the pathological changes of the lacrimal gland tissue of the NOD mouse through modulating the level of TNF-α, IL-1, and NF-κB which results in improved tear secretion and function of the lacrimal gland.     

An experiment of the combined treatment of traditional Lei-huo-jiu therapy with Chinese medicine for the lacrimal gland of Sjögren’s syndrome

This experiment chooses nonobese diabetic (NOD) mouse as the animal model of Sjögren’s syndrome and investigates the morphologic changes, the expression of inflammatory factors and growth factors of this mouse’s lacrimal gland in response to a combined treatment of traditional Lei-huo-jiu therapy alone and in combination with Chinese medicine. The methods were to (1) use a morphological approach to directly observe pathological changes of the lacrimal gland in response to combined treatment and (2) to detect the level of tumor necrosis factor (TNF)-α, interleukin (IL)-1, and nuclear factor kappa B (NF-κB) in lacrimal gland tissue caused by the combined treatments using a immunohistochemical approach. There is a reduction of the mast cell’s degranulation and modulation of the level of cytokines in TNF-α, IL-1, and NF-κB in the combined therapy group. The combined treatment of traditional Lei-huo-jiu therapy with Chinese medicine can improve the pathological changes of the lacrimal gland tissue of the NOD mouse through modulating the level of TNF-α, IL-1, and NF-κB which results in improved tear secretion and function of the lacrimal gland.     

Morphological criteria of early embryonal histogenesis exemplified by the development of the auxiliary ocular apparatus in humans]

In 50 human embryos at the age of 21 days--12 weeks of development, including the stages X-XXIII and beginning of the fetal period according to Carnegie's classification, spatial-temporal regularities on rearrangement of cellular material in the mesenchymal derivatives of the ocular auxiliary apparatus have been investigated. The main attention has been paid to ascertain the moments, when the first signs of differences appear in the previously homogenous cellular material of the differentiating mesenchyme around the ocular cup and in the eyelids, taking into account appearance of derivates in the ocular auxiliary apparatus: sclera, oculomotor muscles, stroma of the lacrimal gland, cartilagenous laminae in the eyelids and in the orbicular muscle. Regularities of cytochemical differentiation of the mesenchyme and its derivatives have been studied, taking into account the organ's changing topography. Morphometrical investigations of cells in the anlages mentioned are expanded and correlated with the time of their cytochemical differentiation. Correlation of the morphometrical and cytochemical data with the histological investigations has been performed.     

Early markers of regeneration following ductal ligation in rat submandibular gland

Rat submandibular glands can recover their function and secretory protein content following ductal ligation-induced atrophy. Morphological studies have established that following ligation, deligation of the gland allows the regeneration of new salivary gland tissue. However, little is known about changes happening during early regeneration following intra-oral duct ligation, which does not damage the parasympathetic nerves. Glands that had been 2 weeks ligated or 2 weeks ligated + 3 days deligated were compared. Tissue was prepared for histological, immunohistochemical (SMG-B and Ki-67) and immunocytochemical analyses (smooth muscle actin, aquaporin 5). Haematoxylin and eosin staining of deligated glands showed that some acini regained their cytoplasmic volume; moreover, the loss of Alcian blue/periodic acid-Schiff’s staining from the lumen of ducts suggested successful deligation. The deligated gland was characterized by atypical acinar-ductal branched structures, which were less frequent in the ligated gland and rarely seen in normal unoperated tissue. Myoepithelial cells were also investigated since changes in their morphology reflected changes in the acini morphology not readily detected by conventional staining. Actin staining revealed the presence of some shrunken acini in the atrophic tissue, whereas they had regained their normal morphology in the deligated gland suggesting that the acini were recovering. Some acini during deligation regained aquaporin 5 expression, which had decreased during atrophy. SMG-B protein, located in the pro-acinar cell during gland development and usually found in the intercalated duct cells in the adult, was detected in the newly formed acini of the deligated gland. This study suggests that morphological markers of regeneration appear as early as 3 days following ligation removal. The authors thank the Wellcome Trust for funding.     

The presence of carbonic anhydrase in orbital glands. An enzyme-histochemical study in cynomolgus monkeys and rabbits

The distribution of carbonic anhydrase (CA) was studied in the lacrimal gland of the cynomolgus monkey as well as in the lacrimal, infra-orbital and harderian glands of the rabbit. In the lacrimal gland of the cynomolgus monkey, a number of acini with positive staining were found; however, another group of acini did not stain. In the positively stained acinar cells, large amounts of reaction product were located in the cytoplasm, but only weak staining was observed in the membranes. In the endothelial cells of capillaries a strong staining reaction was only seen in those vessels which were adjacent to the acinar cells containing CA. In the lacrimal and infra-orbital glands of the rabbit, there was intense staining of the cell membranes in all acinar cells and weak staining of the cytoplasm in a few acinar cells. Stained capillaries were also found here, but these were not as numerous as in the lacrimal gland of the cynomolgus monkey. In the harderian gland of the rabbit, there was no staining in the white lobe. In the red lobe the acinar cells displayed distinct staining exclusively in the basolateral membranes. There was no staining of capillaries in the harderian gland. In none of the glands studied was there staining of the epithelial cells of the excretory ducts. The functional significance of these findings is discussed.     

Novel fiber-dependent entry mechanism for adenovirus serotype 5 in lacrimal acini

The established mechanism for infection of most cells with adenovirus serotype 5 (Ad5) involves fiber capsid protein binding to coxsackievirus-adenovirus receptor (CAR) at the cell surface, followed by penton base capsid protein binding to alpha(v) integrins, which triggers clathrin-mediated endocytosis of the virus. Here we determined the identity of the capsid proteins responsible for mediating Ad5 entry into the acinar epithelial cells of the lacrimal gland. Ad5 transduction of primary rabbit lacrimal acinar cells was inhibited by excess Ad5 fiber or knob (terminal region of the fiber) but not excess penton base. Investigation of the interactions of recombinant Ad5 penton base, fiber, and knob with lacrimal acini revealed that the penton base capsid protein remained surface associated, while the knob domain of the fiber capsid protein was rapidly internalized. Introduction of rabbit CAR-specific small interfering RNA (siRNA) into lacrimal acini under conditions that reduced intracellular CAR mRNA significantly inhibited Ad5 transduction, in contrast to a control (nonspecific) siRNA. Preincubation of Ad5 with excess heparin or pretreatment of acini with a heparinase cocktail each inhibited Ad5 transduction by a separate and apparently additive mechanism. Functional and imaging studies revealed that Ad5, fiber, and knob, but not penton base, stimulated macropinocytosis in acini and that inhibition of macropinocytosis significantly reduced Ad5 transduction of acini. However, inhibition of macropinocytosis did not reduce Ad5 uptake. We propose that internalization of Ad5 into lacrimal acini is through a novel fiber-dependent mechanism that includes CAR and heparan sulfate glycosaminoglycans and that the subsequent intracellular trafficking of Ad5 is enhanced by fiber-induced macropinocytosis.     

The presence of carbonic anhydrase in orbital glands

Summary The distribution of carbone anhydrase (CA) was studied in the lacrimal gland of the cynomolgus monkey as well as in the lacrimal, infra-orbital and harderian glands of the rabbil. In the lacrimal gland of the cynomolgus monkey a number of acini with positive staining were found; however, another group of acini did not stain. In the positively stained acinar cells, large amounts of reaction product were located in the cytoplasm, but only weak staining was observed in the membranes. In the endothelial cells of capillaries a strong staining reaction was only seen in those vessels which were adjacent to the acinar cells containing CA. In the lacrimal and infra-orbital glands of the rabbit, there was intense staining of the cell membranes in all acinar cells and weak staining of the cytoplasm in a few acinar cells. Stained capillaries were also found here, but these were not as numerous as in the lacrimal gland of the cynomolgus monkey. In the harderian gland of the rabbit, there was no staining in the white lobe. In the red lobe the acinar cells displayed distinct staining exclusively in the basolateral membranes. There was no staining of capillaries in the harderian gland. In none of the glands studied was there staining of the epithelial cells of the excretory ducts. The functional significance of these findings is discussed.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday     

Accumulation of Secretory Vesicles in the Lacrimal Gland Epithelia Is Related to Non-Sjögren's Type Dry Eye in Visual Display Terminal Users

Previous observations in a rat model of a non-Sjögren''s syndrome (non-SS) type of dry eye seen in users of visual display terminals (VDT) indicated that secretory vesicle (SV) accumulation in the lacrimal gland epithelia contributes to the condition. Here, to examine this possibility in humans, we compared the lacrimal gland histology and percent SV area in the cytoplasm of acinar epithelial cells using light microscopy and transmission electron microscopy, in patients with VDT work-related non-SS dry-eye (VDT group), SS-induced dry-eye, and autopsied normal controls. In addition, the VAMP8 (vesicle-associated membrane protein 8, an exocrine-pathway molecule) and Rab3D (mature vesicle marker) were histochemically examined in lacrimal gland tissue sections. The lacrimal gland acini were larger in the VDT group than in the SS group, and the percent SV area was significantly higher in the VDT group than in the normal controls (P = 0.021) or SS group (P = 0.004). Immunostaining revealed abnormal distributions of VAMP8 in the VDT and SS groups. Rab3D was more strongly expressed in the cytoplasm of acinar epithelial cells in the VDT group than in that of normal controls. The duration of VDT use was significantly longer in the VDT group than in the other groups. These findings suggest that excessive SV accumulation in the acinar epithelia may contribute to the reduced tear secretion in VDT users.     

Alligator tears: a reevaluation of the lacrimal apparatus of the crocodilians

The Harderian gland is a poorly understood anterior ocular gland that occurs in most terrestrial vertebrates. Numerous extraorbital functions have been ascribed to the Harderian gland, principally based on its association with the nasolacrimal duct. Few studies have centered on archosaurs and the majority of those available focused solely on the Harderian gland of birds. Little is known about the lacrimal apparatus of the crocodilians. We examined the lacrimal apparatus of several specimens of Alligator mississippiensis anatomically, histologically, and histochemically and studied the embryogenesis of this system. The nasolacrimal duct possesses a distal secretory area, which is more convoluted than that of typical mammals or lepidosaurs. The alligator Harderian gland possesses a unique combination of characteristics found in lepidosaurs, birds, and mammals. Like that of both mammals and lepidosaurs, it is a large, tuboloacinar gland that appears to secrete both mucoprotein and lipids. However, the presence of blood vessels and immune cells is reminiscent of that of the avian Harderian gland. The immunogenesis of the alligator Harderian gland appears to be tied to the development of the vascular system. The presence of a distinct palpebral gland in the anterior aspect of the ventral eyelid is a feature unique to alligators. Based on position, this gland does not appear to be homologous to the anterior lacrimal gland of lepidosaurs. Lymphatic aggregations were also found in the palpebral gland. The presence of interstitial immune cells in the orbital glands of alligators suggests that the alligator lacrimal apparatus, like that of birds, may play a role in the head-associated lymphatic tissue system.     

Intracellular distinction between peroxidase and catalase in exocrine cells of rat lacrimal gland: A biochemical and cytochemical study

Summary The lacrimal gland (Glandula orbitalis externa) of rat contains both peroxidase and catalase and was used as a model for biochemical and cytochemical distinction between peroxidase and catalase. Both enzymes were isolated by ammonium sulfate precipitation from tissue homogenates, and the effects of fixation with glutaraldehyde and various conditions of incubation were investigated colorimetrically using DAB as hydrogen donor. The lacrimal gland peroxidase is strongly inhibited by glutaraldehyde treatment. In contrast, for catalase the fixation with glutaraldehyde is the prerequisite for demonstration of its peroxidatic activity. The maximal peroxidatic activity was obtained after treatment of catalase with 3% glutaraldehyde, higher concentrations being inhibitory. For lacrimal gland peroxidase, the maximal rate of oxidation of DAB is at pH 6.5, whereas for catalase it is at pH 10.5. The optimal concentration of H₂O₂ for lacrimal gland peroxidase is at 10⁻³ M and for peroxidatic activity of catalase at 10⁻¹ M. These optimal conditions obtained biochemically were applied to tissue sections of rat lacrimal gland. After the fixation of tissue with a low concentration of glutaraldehyde and incubation in the DAB medium at neutral pH containing 10⁻³ M H₂O₂ (Peroxidase medium), the reaction product was localized in the cisternae of the rough endoplasmic reticulum, in elements of the Golgi apparatus, and in secretory granules. After the fixation of tissue with 3% glutaraldehyde and incubation in the DAB-medium containing 10⁻¹ M H₂O₂ and at pH 10.5 (catalase medium), the staining in the endoplasmic reticulum, the Golgi-apparatus and in secretory granules was completely inhibited and reaction product was localized exclusively in small (0.2–0.5 μ) particles similar to small peroxisomes described in various other cell-types. This work was presented in part at the twenty-fifth Annual Meeting of the Histochemical Society, April 5–6, 1974. Atlantic City, N.J., J. Histochem. Cytochem.22, 288 (1974).     

Manipulating the Murine Lacrimal Gland

The lacrimal gland (LG) secretes aqueous tears necessary for maintaining the structure and function of the cornea, a transparent tissue essential for vision. In the human a single LG resides in the orbit above the lateral end of each eye delivering tears to the ocular surface through 3 - 5 ducts. The mouse has three pairs of major ocular glands, the most studied of which is the exorbital lacrimal gland (LG) located anterior and ventral to the ear. Similar to other glandular organs, the LG develops through the process of epithelial branching morphogenesis in which a single epithelial bud within a condensed mesenchyme undergoes multiple rounds of bud and duct formation to form an intricate interconnected network of secretory acini and ducts. This elaborate process has been well documented in many other epithelial organs such as the pancreas and salivary gland. However, the LG has been much less explored and the mechanisms controlling morphogenesis are poorly understood. We suspect that this under-representation as a model system is a consequence of the difficulties associated with finding, dissecting and culturing the LG. Thus, here we describe dissection techniques for harvesting embryonic and post-natal LG and methods for ex vivo culture of the tissue.     

Primary Rat Lacrimal Cells Undergo Acinar-like Morphogenesis on Reconstituted Basement Membrane and Express Secretory Component under Androgen Stimulation

Single cells or small cell clusters, isolated from the rat lacrimal gland, were incubated on reconstituted basement membrane (matrigel) in a well-defined serum-free medium. During the first days of culture, cells reassociated and reorganized in structures resembling acini. These multicellular structures, maintained in culture for 2 weeks, consisted of well-polarized cuboidal cells surrounding a central lumen and exhibiting apically located microvilli. Myoepithelial cells were observed at the periphery of the acinar structures. Both in the native lacrimal and in the cultured aggregates, epithelial cells displayed strong immunoreactivity for cytokeratin 8, while myoepithelial cells were immunoreactive for vimentin and α-smooth muscle isoactin. These data indicate that the cultured aggregates closely mimic thein vivoarchitecture of lacrimal glands both by morphology and immunohistochemistry. We further demonstrated the presence of an intact androgen receptor and the ability of the cultured aggregates to respond to androgens with increased secretion of the secretory component. Comparable androgen responses were observed in lacrimal gland cultures of 5-week-old male and female rats. In conclusion, we report a morphologically and functionally differentiated culture system of primary rat lacrimal cells, in which androgen-regulated gene expression was observed. This culture model provides a unique experimental paradigm for studying the effects of hormones, cytokines, and growth factors on the morphogenesis, growth, and functional differentiation of lacrimal glands.