A randomized, controlled study to evaluate the efficacy of intra-articular, autologous adipose tissue injections for the treatment of mild-to-moderate knee osteoarthritis compared to hyaluronic acid: a study protocol

BACKGROUND

Osteoarthritis (OA) is a highly debilitating joint disease that causes progressive, irreversible damage to articular cartilage. OA takes a massive toll on society that has grown in recent decades, but no therapy has been shown to halt or reverse the progression of the disease. The critical need for better treatments and increased interest cellular therapies has spawned a new generation of "minimally manipulated" cell treatments. Autologous adipose tissue injections are among the most controversial of these new treatments. Despite a lack of clinical evidence, adipose tissue injections are often marketed as "stem cell" injections with wide-ranging regenerative benefits. The purpose of this study is to estimate the effect size of the treatment by comparing the efficacy of autologous fat to hyaluronic acid (HA). As a secondary aim, we will test for preliminary evidence of efficacy of autologous fat vs. HA.

METHODS

This is a prospective, single-center, parallel-group, randomized, controlled trial. Participants (n = 54) will receive either a single intra-articular, ultrasound-guided injection of autologous adipose tissue or a single intra-articular, ultrasound-guided injection of HA (1:1 ratio). Outcome data will be obtained at baseline, week-6 and month-6. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain domain (WOMAC-A) will be used as the primary outcome measure. Secondary clinical outcome measures include WOMAC (full), clinical anchors (pain, function, and stiffness), and the 29-point Patient-Reported Outcomes Measurement Information System (PROMIS®) profile. We will also take synovial fluid samples and assess sway velocity using a force plate, as well as analyze excess/discard adipose tissue to gain a better understanding of how intra-articular adipose tissue injections influence the biochemical environment of the joint.

DISCUSSION

Given the widespread use of intra-articular fat injections in the United States, it is critical that randomized, controlled human studies evaluating efficacy and biological activity be performed. This study is the first step in addressing this unmet need, but it is not without limitations. The most notable limitations of this study are its small size and lack of blinding, which predisposes the study to both investigator and participant bias.

TRIAL REGISTRATION

NCT03242707 // HS-17-00365 // Registration Date (First Posted): August 8, 2018.

Pregnancy probabilistically augments potential precursors to chronic, immune-mediated or autoimmune lacrimal gland infiltrates

PURPOSE

This study asked whether pregnancy, a risk factor for dry eye disease associated with both chronic, immune-mediated- and autoimmune etiologies, augments development of clusters of coordinately functioning cells (CCFC) that may be precursors to pathological lacrimal gland infiltrates.

METHODS

Lacrimal glands were from six virgin- and six term-pregnant rabbits of the same age and environmental exposure history. Seventy-two immune response-related gene transcripts were assayed by real time RT-PCR. Principal component (PC) analysis identified transcript signatures of CCFC contributing negative (^⊖) or positive (^⊕) PC loadings and determined gland PC projections, which reflect levels of CCFC development.

RESULTS

Three CCFC were of interest as potential precursors to pathological infiltrates. CCFC 1^⊖ was suggestive of an ectopic lymphoid structure with resting T cells and B cells. CCFC 1^⊕ was suggestive of an immune-mediated infiltrate with T_H1 cells and mature, cytotoxic B cells. CCFC 2^⊖ was suggestive of an ectopic lymphoid structure with activated T cells, mature B cells, germinal center, and plasmacytes. CCFC 4^⊖ and CCFC 5^⊖ also included plasmacytes. Pregnancy augmented CCFC 1^⊖ in some glands; augmented CCFC 1^⊕ in others; and augmented CCFC 2^⊖, CCFC 4^⊖, and CCFC 5^⊖ different combinations.

CONCLUSIONS

Potential precursors of pathological infiltrates form in the lacrimal glands by the time of sexual maturity. Pregnancy augments lacrimal gland plasmacyte populations, and it can augment development of potential precursors to either chronic, immune-mediated infiltrates or autoimmune infiltrates of various phenotypes. Systemic and strictly local, probabilistic phenomena interact with pregnancy to determine which combinatorial phenotypes are favored.

Multiple Natural and Experimental Inflammatory Rabbit Lacrimal Gland Phenotypes

Purpose

To investigate lacrimal gland (LG) immunophysiological and immune-mediated inflammatory process (IMIP) phenotype diversity.

Methods

Ex vivo matured dendritic cells (mDC) were loaded with acinar cell microparticles (M_P). Peripheral blood lymphocytes (PBL) were activated in mixed cell reactions with mDC and injected directly into autologous, unilateral LG (1° ATD-LG) of two rabbit cohorts, one naïve, one immunized with a LG lysate membrane fraction (P_i). Autoimmune IgG titers were assayed by ELISA, MCR PBL stimulation indices (SI) by [³H]-thymidine incorporation. Schirmer tests without and with topical anesthetic (STT-I, STT-I_A) and rose Bengal (RB) staining tests were performed. H&E and immunohistochemically stained sections were examined. RNA yields and selected transcript abundances were measured. Immune cell number and transcript abundance data were submitted to Principal Component Analysis (PCA).

Results

Immunizing P_i dose influenced SI but not IgG titers. STT scores were decreased, and rose Bengal scores increased, by day 118 after immunization. Previous immunization exacerbated scores in 1° ATD-eyes and exacerbated 1° ATD-LG atrophy. IMIP were evident in 2° ATD-LG as well as 1° ATD-LG. PCA described diverse immunophysiological phenotypes in control LG and diverse IMIP phenotypes in ATD-LG. IgG titers and SI pre-adoptive transfer were significantly associated with certain post-adoptive transfer IMIP phenotype features, and certain LG IMIP features were significantly associated with RB and STT I_A scores.

Conclusions

The underlying variability of normal states may contribute to the diversity of experimental IMIP phenotypes. The ability to generate and characterize diverse phenotypes may lead to phenotype-specific diagnostic and therapeutic paradigms.

Potentially pathogenic immune cells and networks in apparently healthy lacrimal glands

Lacrimal glands of people over 40 years old frequently contain lymphocytic infiltrates. Relationships between histopathological presentation and physiological dysfunction are not straightforward. Data from rabbit studies have suggested that at least two immune cell networks form in healthy lacrimal glands, one responding to environmental dryness, the other to high temperatures. New findings indicate that mRNAs for several chemokines and cytokines are expressed primarily in epithelial cells; certain others are expressed in both epithelial cells and immune cells. Transcript abundances vary substantially across glands from animals that have experienced the same conditions, allowing for correlation analyses, which detect clusters that map to various cell types and to networks of coordinately functioning cells. A core network--expressing mRNAs including IL-1α, IL-6, IL-17A, and IL-10--expands adaptively with exposure to dryness, suppressing IFN-γ, but potentially causing physiological dysfunction. High temperature elicits concurrent increases of mRNAs for prolactin (PRL), CCL21, and IL-18. PRL is associated with crosstalk to IFN-γ, BAFF, and IL-4. The core network reacts to the resulting PRL-BAFF-IL-4 network, creating a profile reminiscent of Sjögren's disease. In a warmer, moderately dry setting, PRL-associated increases of IFN-γ are associated with suppression of IL-10 and augmentations of IL-1α and IL-17, creating a profile reminiscent of severe chronic inflammation.

Diverse mediators modulate the chloride ion fluxes that drive lacrimal fluid production

PURPOSE

To learn whether locally expressed and systemic mediators might modulate the cholinergically induced transepithelial Cl(-) fluxes that underlie lacrimal fluid production.

METHODS

Reconstituted epithelial monolayers were exposed to a submaximal dose of the muscarinic agonist, carbachol (CCh), or to one of several paracrine mediators for 18 hours, then acutely stimulated with an optimal dose of CCh. Secretory Cl(-) fluxes were assessed as negative short-circuit currents (ISC).

RESULTS

Exposure to IL-6 at concentrations of 1 and 10 ng/mL and IL-1β at 10 ng/mL significantly decreased CCh-induced Cl(-) secretion. Prolactin decreased CCh-induced Cl(-) secretion, but the extent of the decrease diminished as the prolactin concentration increased from 20 to 200 ng/mL. CCh, 10 μM, prevented CCh, 100 μM, from eliciting Cl(-) secretion. Exposure to histamine, 10 mM, prevented formation of confluent monolayers. Exposure to histamine, 1 mM, decreased CCh-induced Cl(-) secretion, whereas exposure to 5-HT, 1 mM, potentiated CCh-induced Cl(-) secretion.

CONCLUSIONS

Chronic exposure to inflammatory cytokines may significantly impair cholinergically induced lacrimal fluid production. Concentrations of prolactin within the high range of normal values also may impair fluid production, but this effect is reversed at levels associated with pregnancy. Autonomic neurotransmitters and paracrine mediators that signal through different G protein-coupled receptors appear to exert varying influences, which range from complete suppression to potentiation of cholinergically induced fluid production. Thus, some hormones and paracrine mediators may impair secretion in apparently homeostatic glands as well as diseased glands, whereas mediators produced by certain immune cell infiltrates may actually enhance fluid formation.

Distinct dacryoadenitides autoadoptively transferred to rabbits by different subpopulations of lymphocytes activated ex vivo

PURPOSE

To test whether CD4+ T cells proliferate in mixed cell reactions with autologous lacrimal gland (LG) acinar cells and whether these cells can autoadoptively transfer disease.

METHODS

Purified acinar cells were gamma irradiated and cocultured with peripheral blood lymphocytes. Activated CD4+ T cells were sorted by fluorescence-activated cell sorting (FACS). Unfractionated activated peripheral blood lymphocytes (UF), CD4+-enriched and CD4+-depleted T cells from an autologous mixed cell reaction were injected into the donor rabbit's remaining LG. After 4 weeks, ocular examinations were performed, and the rabbits were euthanized; LGs were removed for histopathology, immunohistochemistry, and real-time reverse transcription-polymerase chain reaction studies.

RESULTS

CD4 T cells increased in the autologous mixed cell reaction from 20% to 80%. Tear production decreased in the induced disease/UF (ID/UF) group and declined even more in the ID/CD4+-enriched group. Tear breakup times decreased and rose bengal staining increased in all groups. All LGs exhibited significant histopathology and increased messenger RNAs for tumor necrosis factor α. The ID/UF group exhibited the largest increases of CD4+ and rabbit T-lymphocyte antigen-positive cells. The ID/CD4+-enriched group contained fewer infiltrating CD4 cells but more eosinophils, severely altered acinar morphology, and increased fibrosis. LG of the ID/CD4+-depleted group exhibited large increases of CD18, major histocompatibility complex II, and CD4+ cells. Messenger RNAs for interleukin 2, interleukin 4, and CD4+ increased in the ID/CD4+-enriched group compared with the CD4+-depleted group.

CONCLUSIONS

Autoreactive CD4+ effector cells activated ex vivo and autoadoptively transferred, caused what seems to be a distinct dacryoadenitis. The CD4+-depleted cell fraction also contained pathogenic effector cells capable of inducing disease.

Adeno-associated virus-mediated IL-10 gene transfer suppresses lacrimal gland immunopathology in a rabbit model of autoimmune dacryoadenitis

PURPOSE

To evaluate the effect of adeno-associated virus (AAV) vector-mediated viral (v)IL-10 gene expression on lacrimal gland (LG) immunopathology and ocular surface disease in a rabbit model of induced autoimmune dacryoadenitis (ID).

METHODS

Autologous peripheral blood lymphocytes, activated in a mixed-cell reaction when cocultured with purified rabbit lacrimal epithelial cells, induce a Sjögren's-like autoimmune dacryoadenitis when injected directly back into the donor animal's inferior LG. Four weeks after disease induction, AAV vector expressing the vIL-10 gene under control of a tetracycline-inducible promoter was injected into the inferior LG of the treatment group (ID/Rx), and doxycycline was fed orally to induce transgene expression. The ID group serving as control also received doxycycline. All LGs were removed 16 weeks after disease induction.

RESULTS

Clinical symptoms showed overall improvement in the ID/Rx group compared with the ID group. Histopathologic examination of the ID group's LG revealed scattered large lymphocytic foci and areas of altered or distorted acini, whereas the ID/Rx group had scattered small lymphocytic foci. The number of CD18(+) cells was almost fivefold lower in the ID/Rx group than in the ID group. Although the total number of RTLA(+) cells did not differ between the groups, the CD4/CD8 ratio was 16-fold smaller in the ID/Rx group.

CONCLUSIONS

Animals with experimentally induced autoimmune dacryoadenitis appeared to benefit from AAV-mediated vIL-10 gene transfer therapy. Quantitative immunohistochemical analysis suggested that the therapy might not have been simply immunosuppressive but rather supported the induction of CD8(+) regulatory cells.

Microporous poly(L-lactic acid) membranes fabricated by polyethylene glycol solvent-cast/particulate leaching technique

With the eventual goal of developing a tissue-engineered tear secretory system, we found that primary lacrimal gland acinar cells grown on solid poly(L-lactic acid) (PLLA) supports expressed the best histiotypic morphology. However, to be able to perform vectorial transport functions, epithelia must be supported by a permeable substratum. In the present study, we describe the use of a solvent-cast/particulate leaching technique to fabricate microporous PLLA membranes (mpPLLAm) from PLLA/polyethylene glycol blends. Scanning electron microscopy revealed pores on both the air-cured ( approximately 4 microm) and glass-cured sides (<2 microm) of the mpPLLAm. Diffusion studies were performed with mpPLLAm fabricated from 57.1% PLLA/42.9% polyethylene glycol blends to confirm the presence of channelized pores. The data reveal that glucose, L-tryptophan, and dextran (a high molecular weight glucose polymer) readily permeate mpPLLAm. Diffusion of the immunoglobulin G through the mpPLLAm decreased with time, suggesting the possible adsorption and occlusion of the pores. Cells cultured on the mpPLLAm (57.1/42.9 wt%) grew to subconfluent monolayers but retained histiotypic morphological and physiological characteristics of lacrimal acinar cells in vivo. Our results suggest that mpPLLAm fabricated using this technique may be useful as a scaffold for a bioartificial lacrimal gland device.

Long-term topical cyclosporine treatment improves tear production and reduces keratoconjunctivitis in rabbits with induced autoimmune dacryoadenitis

PURPOSE

To use a rabbit model of induced autoimmune dacryoadenitis to evaluate the efficacy of topical ophthalmic cyclosporine A (CsA).

METHODS

Autoimmune dacryoadenitis was induced by injecting autologous peripheral blood lymphocytes, which had been activated in a mixed cell reaction with acinar cells isolated from one inferior lacrimal gland (LG), back into the donor animal's remaining inferior LG. Schirmer's test, tear breakup time, and rose Bengal staining were assessed. Animals with established disease were treated topically with either CsA or Endura twice daily for 5 months.

RESULTS

Without treatment tear production and tear stability were abnormal for 6 months, and clear signs of ocular surface defects were evident. Severe immune cell infiltration was observed in the LG. Long-term CsA treatment increased tear production only slightly, but the severity of LG histopathology decreased noticeably. CD4(+) T-cell infiltration of the LG was decreased and infiltration by MHC class II-expressing cells was also decreased. For the Endura-treated group tear production did not improve, rose Bengal scores remained high, and histopathology showed infiltration comparable to the untreated group, but by the end of the study the tear breakup time did improve.

CONCLUSIONS

The rabbit model of autoimmune dacryoadenitis had signs of chronic dry eye disease 6 months after induction of disease. Tear production improved slightly with CsA treatment and CD4(+) T-cell infiltration decreased significantly in the LG. This suggests that some Sjögren's patients may benefit from long-term CsA treatment.

Suppression of lymphocyte proliferation and regulation of dendritic cell phenotype by soluble mediators from rat lacrimal epithelial cells

Lacrimal epithelial cells appear to constitutively secrete autoantigens to their underling stroma. The present experiments address the hypothesis that they also secrete soluble factors that regulate immune responses. Epithelial cells, spleen cells and lymphocytes were obtained from rabbits or rats and cultured in various configurations. Monocytes from rat bone marrow were matured to dendritic cells (DC) ex vivo. Proliferation was measured by [3H]-thymidine incorporation; surface MHC Class II and CD86 using flow cytometry; and mRNA relative abundances using real time RT-PCR. Microporous culture inserts containing rat lacrimal cells inhibited proliferation of rabbit lymphocytes co-cultured with autologous lacrimal cells and of rat lymphocytes co-cultured with TNF-alpha-stimulated DC. They inhibited CD86 and MHC Class II surface expression by maturating DC and reversed surface expression of CD86 but not MHC Class II by partially matured DC. Subsequent exposure of partially matured DC to mediators from rat lacrimal cells reversed the ability to stimulate lymphocyte proliferation. TGF-beta(1) and IL-10 mRNAs increased somewhat when rat lacrimal cells were isolated but decreased markedly in rabbit lacrimal cells. Antibodies to TGF-beta prevented soluble factors from rat lacrimal cells from inhibiting proliferation of rabbit lymphocytes co-cultured with rabbit lacrimal cells, but recombinant TGF-beta alone did not mimic the soluble factors. IL-10 immunopositivity was detected in epithelial cells of interlobular ducts and occasional interstitial cells in rabbit lacrimal gland. Rat lacrimal epithelial cells secrete TGF-beta and other factors that synergize to suppress lymphocyte proliferation and regulate DC maturation. Interlobular duct epithelial cells in rabbit lacrimal glands may express similar functions.

Autoimmune dacryoadenitis and keratoconjunctivitis induced in rabbits by subcutaneous injection of autologous lymphocytes activated ex vivo against lacrimal antigens

Autologous peripheral blood lymphocytes (PBL), activated in a mixed cell reaction when co-cultured with purified rabbit lacrimal epithelial cells, are known to induce a Sjögren's-like autoimmune dacryoadenitis and keratoconjunctivitis when injected directly back into the donor animal's inferior lacrimal gland (LG). This study shows that autoreactive lymphocytes injected subcutaneously in a site away from the LG is capable of inducing an autoimmune disease in a rabbit. Induced disease (ID) develops more slowly, taking 4weeks as compared to 2weeks in the direct injection model. Initially, both clinical symptoms and histopathology are less pronounced than in the direct injection ID model, but later the immunocytochemistry shows the same CD4+/CD8+ ratio of 4:1 for both injection methods. The finding that lymphocytes activated against lacrimal antigens can travel or home from the injection site back to the inferior and superior LG, as well as the conjunctiva, suggests that these anatomical sites may have common epitopes that induce pathogenic CD4+ T cells that produce a Sjögren's-like syndrome.

Animal models of dry eye

BACKGROUND

The causes of dry eye include lacrimal gland insufficiency, meibomian gland dysfunction, impairment of the neuronal innervation and environmental stress - all leading to irritation of the ocular surface. Several animal models have been developed to imitate different pathophysiologic mechanisms in the development of dry eye. Understanding the characteristics and limitations of these models will help researchers choose the right models to address specific problems and develop new treatment modalities in dry eye.

METHODS

Medline searches were performed to identify English language articles relating to different animal models of dry eye. Manual cross-referencing was also performed and some historical articles were included.

RESULTS AND CONCLUSION

A huge variety of animal models exists, mimicking different pathophysiologic mechanisms which can cause dry eye. The mouse is the model most commonly used to study autoimmune mechanisms, because of the diversity of different knockout and transgenic strains and good availability of antibodies. For studying dry eye signs, rabbit or dog models are more suitable, because they present decreased tear secretion and ocular surface changes, have longer lifespans, and offer better accessibility of the ocular surface. For studying special causes of dry eye, such as defects of neuronal reflex loops, environmental changes, or evaporative dry eye, the model of choice should recapitulate the underlying pathophysiologic mechanism.

Sjogrens syndrome as failed local immunohomeostasis: prospects for cell-based therapy

Sjogrens syndrome has been estimated to affect between 0.2% and 2% or more of the population. It is an autoimmune disease with the hallmark histopathology of focal, periductal, and perivascular CD4(+) cell infiltration of the lacrimal and salivary glands. The immunohistopathology is typically associated with severe lacrimal and salivary dysfunctions, which contribute to debilitating ocular surface and oral symptoms. The quality of life of patients with Sjogrens syndrome often is degraded further by serious, multisystemic manifestations, and they are subject to a forty-fold increased risk of developing B cell lymphomas. In normal lacrimal glands, secretory epithelial cells, autoimmune effector lymphocytes, and regulatory lymphocytes can be seen as collaborating to maintain a local immunohomeostasis. The epithelium contributes by secreting immunomodulatory paracrine factors and also by continuously exposing autoantigens, which thereby become available for uptake by professional antigen presenting cells (APCs). Local or systemic perturbations may initiate autoimmune pathophysiology by impairing the replacement of normally-turning-over regulatory cells, by altering epithelial production of immunomodulatory paracrine factors, by inducing intact epithelial cells to begin secreting previously cryptic epitopes (epitopes that previously were not available to bind to major histocompatibility complex (MHC) molecules and so could not be recognized by T cell antigen receptors), and by inducing epithelial cells to begin expressing MHC Class II molecules and presenting formerly cryptic epitopes directly to CD4(+) cells. This process has been modeled ex vivo with mixed cell reactions comprised of isolated epithelial cells and autologous lymphocytes. This development has occurred as studies of anterior chamber-associated immune deviation (ACAID) and other immunoregulatory phenomena have elucidated the origins and functions of several different kinds of regulatory lymphocytes and shown that regulatory lymphocytes can be generated ex vivo. It now is possible to envision strategies for exploiting each possible mode of epithelial autoantigen exposure to produce therapeutic regulatory cells that might be capable of re-establishing normal immunohomeostasis. Consideration of the hypothetical therapies identifies a number of basic questions that warrant investigation.

Traffic of endogenous, transduced, and endocytosed prolactin in rabbit lacrimal acinar cells

The rabbit lacrimal gland undergoes an immunophysiological transformation during pregnancy, reminiscent of that of the mammary gland as it prepares to deliver secretory IgA into the nascent fluid product. The contents of TGF-beta and prolactin (PRL) within ductal epithelial cells increase, and their primary localizations shift from the apical to the basal cytoplasm, suggesting a transformation from exocrine to paracrine secretion. Studies with ex vivo acinar cell models demonstrated that elevated PRL suppresses traffic of secretory proteins into the regulated exocrine apparatus and directs them into a novel, induced, regulated paracrine apparatus [Wang, Y., Chiu, C.T., Nakamura, T., Walker, A.M., Petridou, B., Trousdale M.D., Hamm-Alvarez S.F., Schechter J.E., Mircheff A.K., 2007. Elevated prolactin redirects secretory vesicle traffic in rabbit lacrimal acinar cells. Am. J. Physiol. Endocrinol. Metab. 292, E1122-E1134]. However, it was not clear whether PRL itself entered the induced paracrine apparatus. In the present study, confocal immunofluorescence microscopy revealed that natively expressed PRL and over-expressed PRL co-localized with PRL receptors (PRLR); rab11, a marker for the recycling endosome; gamma-adaptin, a marker for the Golgi complex and trans-Golgi network; and rab7, a marker for the autophagic lysosomal apparatus. Natively expressed, over-expressed, and endocytosed PRL also co-localized with rab4 and rab5A, markers for the early endosome, and with rab3D, a marker for regulated exocrine secretory vesicles. Endocytosed PRL was stored in intact form and released in response to stimulation with carbachol. Subcellular fractionation analysis detected relative excesses of PRL over PRLR in fractions that contained fragments of the recycling endosome and fractions that contained both secretory vesicle fragments and prelysosomal and autolysosomal fragments. EM-gold microscopy demonstrated PRL within small vesicles, consistent with endosomes or secondary lysosomes, and in large vesicles, consistent with regulated secretory vesicles. The secretory vesicles were preponderantly localized in the apical cytoplasm of control cells, and in the basal cytoplasm of PRL over-expressing cells. These results indicate that when lacrimal epithelial cells synthesize PRL, and when they endocytose it from their ambient medium, they traffic it both into the endosomes that constitute the constitutive transcytotic paracrine apparatus and also into regulated secretory vesicles, which are associated with the exocrine apparatus at low PRL levels and with the induced paracrine apparatus at high PRL levels.

Transepithelial bioelectrical properties of rabbit acinar cell monolayers on polyester membrane scaffolds

In our quest to develop a tissue-engineered tear secretory system, we have tried to demonstrate active transepithelial ion fluxes across rabbit lacrimal acinar cell monolayers on polyester membrane scaffolds to evaluate the bioelectrical properties of the cultured cells. Purified lacrimal gland acinar cells were seeded onto polyester membrane inserts and cultured to confluency. Morphological properties of the cell monolayers were evaluated by transmission electron microscopy and immunofluorescence staining for Na(+),K(+)-ATPase and the tight junction-associated protein occludin. Sections revealed cell monolayers with well-maintained epithelial cell polarity, i.e., presence of apical (AP) secretory granules, microvilli, and junctional complexes. Na(+),K(+)-ATPase was localized on both the basal-lateral and apical plasma membranes. The presence of tight cell junctions was demonstrated by a positive circumferential stain for occludin. Bioelectrical properties of the cell monolayers were studied in Ussing chambers under short-circuit conditions. Active ion fluxes were evaluated by inhibiting the short-circuit current (I(sc)) with a Na(+),K(+)-ATPase inhibitor, ouabain (100 microM; basal-lateral, BL), and under Cl(-)-free buffer conditions after carbachol stimulation (CCh; 100 microM). The directional apical secretion of Cl(-) was demonstrated through pharmacological analysis, using amiloride (1 mM; BL) and bumetanide (0.1 mM; BL), respectively. Regulated protein secretion was evaluated by measuring the beta-hexosaminidase catalytic activity in the AP culture medium in response to 100 microM basal CCh. In summary, rabbit lacrimal acinar cell monolayers generate a Cl(-)-dependent, ouabain-sensitive AP --> BL I(sc) in response to CCh, consistent with current models for Na(+)-dependent Cl(-) secretion.

Calcium-activated endoplasmic reticulum stress as a major component of tumor cell death induced by 2,5-dimethyl-celecoxib, a non-coxib analogue of celecoxib

A drawback of extensive coxib use for antitumor purposes is the risk of life-threatening side effects that are thought to be a class effect and probably due to the resulting imbalance of eicosanoid levels. 2,5-Dimethyl-celecoxib (DMC) is a close structural analogue of the selective cyclooxygenase-2 inhibitor celecoxib that lacks cyclooxygenase-2-inhibitory function but that nonetheless is able to potently mimic the antitumor effects of celecoxib in vitro and in vivo. To further establish the potential usefulness of DMC as an anticancer agent, we compared DMC and various coxibs and nonsteroidal anti-inflammatory drugs with regard to their ability to stimulate the endoplasmic reticulum (ER) stress response (ESR) and subsequent apoptotic cell death. We show that DMC increases intracellular free calcium levels and potently triggers the ESR in various tumor cell lines, as indicated by transient inhibition of protein synthesis, activation of ER stress-associated proteins GRP78/BiP, CHOP/GADD153, and caspase-4, and subsequent tumor cell death. Small interfering RNA-mediated knockdown of the protective chaperone GRP78 further sensitizes tumor cells to killing by DMC, whereas inhibition of caspase-4 prevents drug-induced apoptosis. In comparison, celecoxib less potently replicates these effects of DMC, whereas none of the other tested coxibs (rofecoxib and valdecoxib) or traditional nonsteroidal anti-inflammatory drugs (flurbiprofen, indomethacin, and sulindac) trigger the ESR or cause apoptosis at comparable concentrations. The effects of DMC are not restricted to in vitro conditions, as this drug also generates ER stress in xenografted tumor cells in vivo, concomitant with increased apoptosis and reduced tumor growth. We propose that it might be worthwhile to further evaluate the potential of DMC as a non-coxib alternative to celecoxib for anticancer purposes.

Elevated prolactin redirects secretory vesicle traffic in rabbit lacrimal acinar cells

During pregnancy, lymphocytes infiltrating the rabbit lacrimal gland disperse to the interacinar space from their normal focal concentrations, basal fluid secretion decreases, pilocarpine-induced fluid secretion increases, and stimulated fluid protein concentration decreases. Ductal epithelial cell prolactin (PRL) content increases and redistributes from the apical to the basal-lateral cytoplasm. A replication-incompetent adenovirus vector for rabbit PRL (AdPRL) was used to test the hypothesis that increased intracrine/autocrine PRL signaling alters secretory protein traffic in an ex vivo lacrimal acinar cell model. AdPRL had no discernable influence on microtubules or actin microfilaments or their responses to carbachol (CCh). Endogenous and transduced PRLs exhibited similar, nonpolarized, punctate distributions. Cells secreted PRL consititutively and at increased rates in response to CCh. In contrast, constitutive secretion of beta-hexosaminidase was negligible, suggesting that the constitutive pathway for PRL is relatively inaccessible to typical secretory proteins. AdPRL had no significant effect on total secretion of beta-hexosaminidase or syncollin-green fluorescent protein (GFP), a chimeric secretory protein construct. However, it reversed the polarized distributions of vesicles containing rab3D and syncollin-GFP. Live-cell imaging indicated that AdPRL redirected CCh-dependent syncollin-GFP exocytosis from the apical plasma membrane to the basal-lateral membrane. Elevated concentrations of exogenous rabbit PRL in the ambient medium elicited similar changes. These observations suggest that elevated PRL, as occurs in the physiological hyperprolactinemia of pregnancy, induces lacrimal epithelial cells to express a mixed exocrine/endocrine phenotype that secretes fluid to the acinus-duct lumen but secretes proteins to the underlying tissue space. This phenotype may contribute to the pregnancy-associated immunoarchitecture.

Tissue-engineered tear secretory system: functional lacrimal gland acinar cells cultured on matrix protein-coated substrata

Dry eye is a general term that refers to a myriad of ophthalmic disorders resulting in the inadequate wetting of the corneal surface by the tear film. Dry eyes are typically treated by the application of artificial tears. However, patients with lacrimal insufficiencies such as Stevens-Johnson syndrome, chemical and thermal injuries, or ocular cicatricial pemphigoid have very limited options because of the short duration and action of lubricating agents. As a therapeutic strategy, we are working to develop a bioengineered tear secretory system for such patients. This article describes the growth and physiological properties of purified rabbit lacrimal gland acinar cells (pLGACs) on several matrix protein-coated polymers such as silicone, collagen I, copolymers of poly-D,L-lactide-co-glycolide (PLGA; 85:15 and 50:50), poly-L-lactic acid (PLLA), and Thermanox plastic cell culture coverslips. Monolayers of acinar cells were established on all of the polymeric substrata. An assay of beta-hexosaminidase activity in the supernatant medium showed significant increases in protein secretion, following stimulation with 100 microM carbachol on matrix protein-coated and uncoated polymers such as silicone, PLGA 85:15, and PLLA. Our study demonstrates that PLLA supported the morphological and physiological properties of purified rabbit lacrimal gland epithelial cells more successfully than the others.

Current status of gene delivery and gene therapy in lacrimal gland using viral vectors

Gene delivery is one of the biggest challenges in the field of gene therapy. It involves the efficient transfer of transgenes into somatic cells for therapeutic purposes. A few major drawbacks in gene delivery include inefficient gene transfer and lack of sustained transgene expression. However, the classical method of using viral vectors for gene transfer has circumvented some of these issues. Several kinds of viruses, including retrovirus, adenovirus, adeno-associated virus, and herpes simplex virus, have been manipulated for use in gene transfer and gene therapy applications. The transfer of genetic material into lacrimal epithelial cells and tissues, both in vitro and in vivo, has been critical for the study of tear secretory mechanisms and autoimmunity of the lacrimal gland. These studies will help in the development of therapeutic interventions for autoimmune disorders such as Sjögren's syndrome and dry eye syndromes which are associated with lacrimal dysfunction. These studies are also critical for future endeavors which utilize the lacrimal gland as a reservoir for the production of therapeutic factors which can be released in tears, providing treatment for diseases of the cornea and posterior segment. This review will discuss the developments related to gene delivery and gene therapy in the lacrimal gland using several viral vector systems.

Characterization of β-hexosaminidase secretion in rabbit lacrimal gland

The present study was aimed at validating the use of the lysosomal enzyme beta-hexosaminidase as a marker of secretory function in cultured rabbit lacrimal gland acinar cells. The secretory response and morphological characteristics of isolated acinar cells cultured in a serum-free medium supplemented with an extracellular matrix extract were monitored over time as part of optimization of our culturing protocol. Secreted beta-hexosaminidase activity was analyzed and compared with that of another lysosomal enzyme, cathepsin B, as well as protein secreted into the media, w or w/o the presence of secretagogues or protein kinase C activators and inhibitors. Lacrimal gland fluid was obtained from pilocarpine stimulated rabbits, and the activities of beta-hexosaminidase and cathepsin B were measured. A membrane fraction and a soluble fraction were obtained from isolated acinar cells and used for kinetic studies of beta-hexosaminidase in comparison with that released from cultured cells, in the lacrimal gland fluid and in serum. Optimal secretory response was obtained when the cells had been in culture for 2-3 days, coinciding with the formation of acinus-like structures. Stimulation of the cultured cells by carbachol or phorbol esters resulted in a more than 3-fold increase of beta-hexosaminidase release over basal, whereas no effect on cathepsin B release could be detected. Treatment with the protein kinase C inhibitor, chelerythrine chloride, significantly decreased the carbachol and phorbol ester-stimulated secretion. Cathepsin B could not be detected in rabbit lacrimal fluid, but beta-hexosaminidase was easily measured in quantities corresponding to as low as 0.4 microl of tear fluid. Using 4-methylumbelliferyl N-acetyl-beta-D-glucosaminide as a substrate for beta-hexosaminidase, the K(m) in lacrimal gland fluid (1.22+/-0.15 mM) was not significantly different from that of the membrane-associated fraction, the soluble fraction, rabbit serum or activity secreted from cultured cells. Beta-hexosaminidase is secreted by rabbit lacrimal gland, in vivo, and by acinar cells in primary culture, whereas cathepsin B is not secreted under the conditions described. Beta-hexosaminidase therefore provides a versatile marker for secretion in studies of tear production utilizing the rabbit as a model. Our results also indicate that PKC is an important regulator of rabbit lacrimal gland secretion.

Interacting influences of pregnancy and corneal injury on rabbit lacrimal gland immunoarchitecture and function

PURPOSE

Previous reports indicated that pregnancy and corneal injury (CI) trigger alterations of lacrimal gland (LG) growth factor expression and redistributions of lymphocytes from periductal foci to acini. The purpose of this study was to test our hypothesis that pregnancy would exacerbate the changes induced by CI.

METHODS

Corneas were injured with scalpel blades, and, 2 weeks later, LGs were collected for immunocytochemistry and Western blot analysis. Lacrimal fluid was collected under basal- and pilocarpine-stimulated conditions for protein determination and Western blot analyses.

RESULTS

There were significant increases of immunoreactivity for prolactin, TGF-beta1, and EGF in duct cells during pregnancy and after CI, most prominent in pregnant animals with CI. Pregnancy decreased baseline lacrimal fluid secretion, whereas CI did not have a noticeable effect; pregnancy and CI combined resulted in increased fluid production. Pregnancy and CI each increased pilocarpine-induced lacrimal fluid production, whereas protein concentrations were decreased. Prolactin, TGF-beta1, and EGF were detected in LG by Western blot analysis but were minimally detectable in lacrimal fluid. RTLA+ and CD18+ cells were redistributed from periductal to interacinar sites during pregnancy and after CI, most prominent in pregnant animals with CI.

CONCLUSIONS

Like pregnancy, CI is associated with redistribution of immune cells from periductal to interacinar sites and enhanced immunoreactivity of prolactin, TGF-beta1, and EGF in ductal cells. Although baseline lacrimal fluid secretion varied, the glands of all three experimental groups produced significant amounts of fluid in response to pilocarpine, but protein concentrations were decreased.

Mucosal Immunity and Self-Tolerance in the Ocular Surface System

This paper articulates a new working hypothesis that explains many of the pathophysiological conditions described under the common rubric "dry eye" as altered states of mucosal immune regulation. A central principle of mucosal immune physiology is that the parenchymal tissues at the effector sites, i.e., the sites at which secretory antibodies are produced, maintain local signaling milieus that support differentiation of IgA+ plasmablasts and survival of IgA+ plasmacytes. These local signaling milieus also support robust regulatory networks that maintain tolerance to commensual microbes, benign antigens, and parenchymal autoantigens. The regulatory networks are mediated by cycles of interactions between successive generations of dendritic cells, which normally mature with tolerogenic functions, and regulatory T cells, which normally reinforce the system's ability to generate new tolerogenic dendritic cells. The systemic endocrine environment controls expression of the local signaling milieu in the mammary gland and in the prostate and male urethral glands. Emerging evidence indicates that the local signaling milieu in the lacrimal gland also is determined, in part, by the systemic endocrine environment. This working hypothesis suggests explanations for the excess incidence of Sjogren syndrome among women and for the mechanisms of several different immunophysiological states in addition to Sjogren syndrome that, like Sjogren syndrome, are associated with the classical symptoms and signs of dry eye. It also comprises a promising rationale for specific new approaches to therapy.

Expression of TNF inhibitor gene in the lacrimal gland promotes recovery of tear production and tear stability and reduced immunopathology in rabbits with induced autoimmune dacryoadenitis

BACKGROUND

The most common cause of ocular morbidity in developed countries is dry eye, many cases of which are due to lacrimal insufficiency. Dry eye affects approximately 10 million in the United States, most of whom are women. In the U.S. alone, an estimated 2 million Sjögren's syndrome patients have dysfunctional lacrimal glands and severe dry eye, and there is no satisfactory treatment. These patients would benefit if their lacrimal tissue function could be restored.

METHODS

The effect of adenovirus-mediated transfer of tumor necrosis factor (TNF)-alpha inhibitor gene on induced autoimmune dacryoadenitis was evaluated in a rabbit model. Soluble transgene protein was detected in tears by ELISA for 7 days following transduction.

RESULTS

Two weeks after induction of disease with activated lymphocytes, tear production, as determined by Schirmer testing, was reduced by about 40%, while tear film stability, as measured by tear breakup time (BUT), declined by 43%. Adenovirus-mediated gene therapy using AdTNFRp55-Ig given 2 weeks after disease induction, resulted in the return of tear production to normal levels by week 4. In the treated disease group, tear BUT improved significantly by week 4. Rose bengal scores, an indicator of corneal surface defects, increased after disease induction and declined after gene therapy. In the lacrimal gland, the CD4 to CD8 T cell ratio was 4:1 in the disease group compared to 1:2 in the treated group. Infiltration of T cells and CD18+ cells was reduced approximately 50% after gene therapy.

CONCLUSION

We concluded that therapeutic levels of soluble TNF inhibitor were achieved in the lacrimal gland and on the corneal surface. Anti-inflammatory cytokine gene expression might offer a potential therapeutic modality for the treatment of autoimmune dacryoadenitis, once suitable vectors become available.

Accumulation of catalytically active proteases in lacrimal gland acinar cell endosomes during chronic ex vivo muscarinic receptor stimulation

Chronic muscarinic stimulation induces functional quiescence (Scand J Immunol 2003;58:550-65) and alters the traffic of immature cathepsin B (Exp Eye Res 2004;79:665-75) in lacrimal acinar cells. To test whether active proteases aberrantly accumulate in the endosomes, cell samples were cultured 20 h with and without 10-microm carbachol (CCh), incubated with [125I]-bovine serum albumin and then lysed and analysed by subcellular fractionation. CCh decreased total cysteine protease and cathepsin S activities in the isolated lysosome, redistributing them to early endocytic and biosynthetic compartments. CCh decreased [125I] accumulation in all compartments of cells loaded in the absence of protease inhibitors; the cysteine protease inhibitor, leupeptin, prevented the endosomal decrease but not the lysosomal decrease. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and autoradiography demonstrated [125I]-labelled proteolytic products in endomembrane compartments of both control and CCh-stimulated cells, even in the presence of leupeptin, but analysis indicated that CCh increased the amount in endosomes. Two-dimensional fractionation analyses suggest that the CCh-induced redistributions result from blocks in traffic to the late endosome from both the early endosome and the trans-Golgi network. Therefore, we conjecture that chronic muscarinic acetylcholine receptor stimulation leads to aberrant proteolytic processing of autoantigens in endosomes, from whence previously cryptic epitopes may be secreted to the underlying interstitial space.

Altered traffic to the lysosome in an ex vivo lacrimal acinar cell model for chronic muscarinic receptor stimulation

Evidence suggests that lacrimal and salivary epithelial cells constitutively expose potentially pathogenic autoantigens, but that active regulatory networks normally suppress pathological autoimmune responses . Events that potentially disrupt the regulatory networks include increased exposure of constitutive autoantigens and induced exposure of previously cryptic autoantigen epitopes. Chronic muscarinic receptor (MAChR) stimulation in an ex vivo rabbit lacrimal acinar cell model induces functional and biochemical alterations reminiscent of the functional quiescence associated with Sjogren's syndrome . Chronic MAChR stimulation also elicits changes in the compartmental distribution of beta-hexosaminidase, a product that normally is dually targeted into the lysosomal pathway and the regulated apical secretory pathway. Here, we use subcellular fractionation analyses to further explore the nature of the stimulation-induced traffic changes and to identify effectors that might mediate this change. Overnight stimulation of primary cultured rabbit lacrimal gland acinar cells with 10 microM carbachol (CCh) significantly decreased the abundance of mature cathepsin B in the pre-lysosome and lysosome; decreased the abundance of preprocathepsin B in fractions containing the TGN and late endosome; increased the abundance of procathepsin B in fractions containing the basal-lateral membrane; and increased the accumulation of endocytosed [(125)I]-EGF in the recycling endosome. Alterations in distribution or abundance of traffic effectors included: increased abundances of rab5A and rab6 in the TGN; decreased overall abundance of gamma-adaptin; remarkably increased relative abundance of membrane phase-associated actin; redistribution of cytoplasmic dynein from biosynthetic and proximal endocytic compartments to the lysosome; and redistribution of p150(Glued) from the lysosome to biosynthetic or proximal endocytic compartments. We conclude that chronic MAChR stimulation blocks traffic from the early endosome and the TGN to the lysosome, causing lysosomal proteins to reflux to the TGN, endosomes, and basal-lateral membrane. These traffic alterations may be mediated through action on one or more of the effectors noted.

Role of the microtubule cytoskeleton in traffic of EGF through the lacrimal acinar cell endomembrane network

We have previously documented a novel biphasic traffic pattern for epidermal growth factor (EGF) in the acinar epithelial cell of the lacrimal gland. Different from the typical paradigm observed in many other cell types, EGF initially accumulates in the acinar basal-lateral recycling endosome, then is re-directed to the prelysosomes and lysosomes and degraded. While the cellular content of intact EGF decreases by 40% between 20 and 120 m of continuous incubation at 37 degrees C, the EGF receptor (EGFR) content decreases only modestly [J. Cell Physiol. 199 (2004) 108]. The purpose of the present study was to investigate the role of the microtubule cytoskeleton in this traffic. Primary cultured rabbit lacrimocytes were incubated with [(125)I]-EGF, lysed, and analyzed by subcellular fractionation on sorbitol density gradients. Nocodazole treatment appeared to slightly decrease the initial uptake rate but to have no significant effect on the total amount of [(125)I] accumulation. However, it enhanced accumulation of [(125)I]-EGF and EGFR in the basal-lateral recycling endosome, and it enhanced accumulation of prepro- and pro- cathepsin B in fractions containing late endosomes and prelysosomes. Nocodazole permitted the time-dependent release of [(125)I]-EGF from the recycling endosome, but it partially inhibited [(125)I]-EGF degradation and decreased accumulation of [(125)I]-labeled degradation products in the lysosome. The microtubule-based molecular motors, cytoplasmic dynein and kinesin, were localized in compartments containing the late endosomes, prelysosomes, and lysosomes, consistent with the suggestion that microtubule-based molecular motors play important roles in traffic within the lysosomal pathway. Confocal fluorescence microscopy imaging of FITC-EGF substantiated the effects observed in biochemical studies by demonstrating that nocodazole increased accumulation in a peripheral compartment and decreased traffic to a perinuclear compartment. These data suggest that initial accumulation in the basal-lateral recycling endosome and subsequent release from the recycling endosome to the late endosomes and prelysosome are not microtubule-dependent. On the other hand, microtubule-based motors are more critical for traffic from the prelysosome to the lysosome.

Prophylactic effect of IL-10 gene transfer on induced autoimmune dacryoadenitis

PURPOSE

To evaluate the effect of viral IL-10 on the lacrimal gland immunopathologic response in the ocular surface disease, induced autoimmune dacryoadenitis.

METHODS

Disease was induced in rabbits by injecting inferior lacrimal glands with peripheral blood lymphocytes activated by 5 days of coculture with autologous acinar cells in a mixed-cell reaction. In the treated group, an adenoviral vector carrying the vIL-10 gene was concurrently injected with activated lymphocytes. Tears were collected periodically for quantitation of IL-10 by ELISA. Two weeks after disease induction, tear production, tear film breakup time, and rose bengal staining score were determined. Sectioned glands were immunostained for expression of CD4, CD8, rabbit thymic lymphocyte antigen (RTLA), CD18 and major histocompatibility complex class II.

RESULTS

The titer of vIL-10 in tears was at its maximum on day 3, started to decline by day 7, and was undetectable by day 14. In the diseased group, the tear production rate and tear film breakup time were significantly decreased, and rose bengal staining was significantly increased. Diseased glands had immune cell infiltrates containing CD4+, RTLA+, and CD18+ cells, and major histocompatibility complex class II expression was increased. These changes were significantly ameliorated by expression of vIL-10.

CONCLUSIONS

In vivo transduction of the lacrimal gland with AdvIL-10 resulted in the transient appearance of vIL-10 in tears. The presence of vIL-10 partially suppressed the appearance of Sjögren-syndrome-like features of reduced tear production, accelerated tear breakup, ocular surface disease, and immunopathologic response. Anti-inflammatory cytokine gene expression may offer a therapeutic modality for the treatment of autoimmune dacryoadenitis, once suitable vectors become available.

Novel biphasic traffic of endocytosed EGF to recycling and degradative compartments in lacrimal gland acinar cells

The purpose of this study was to delineate the traffic patterns of EGF and EGF receptors (EGFR) in primary cultured acinar epithelial cells from rabbit lacrimal glands. Uptake of [(125)I]-EGF exhibited saturable and non-saturable, temperature-dependent components, suggesting both receptor-mediated and fluid phase endocytosis. Accumulation of [(125)I] was time-dependent over a 120-min period, but the content of intact [(125)I]-EGF decreased after reaching a maximum at 20 min. Analytical fractionation by sorbitol density gradient centrifugation and phase partitioning indicated that within 20 min at 37 degrees C [(125)I] reached an early endosome, basal-lateral recycling endosome, pre-lysosome, and lysosome. Small components of the label also appeared to reach the Golgi complex and trans-Golgi network. Intact [(125)I]-EGF initially accumulated in the recycling endosome; the content in the recycling endosome subsequently decreased, and by 120 min increased amounts of [(125)I]-labeled degradation products appeared in the pre-lysosomes and lysosomes. Confocal microscopy imaging of FITC-EGF and LysoTrackerRed revealed FITC enriched in a dispersed system of non-acidic compartments at 20 min and in acidic compartments at 120 min. Both confocal immunofluorescence microscopy and analytical fractionation indicated that the intracellular EGFR pool was much larger than the plasma membrane-expressed pool at all times. Cells loaded with [(125)I]-EGF released a mixture of intact EGF and [(125)I]-labeled degradation products. The observations indicate that in lacrimal acinar cells, EGFR and EGF-EGFR complexes continually traffic between the plasma membranes and a system of endomembrane compartments; EGF-stimulation generates time-dependent signals that initially decrease, then increase, EGF-EGFR traffic to degradative compartments.

Biochemical changes contributing to functional quiescence in lacrimal gland acinar cells after chronic ex vivo exposure to a muscarinic agonist

Profound secretory dysfunction can be associated with relatively modest lymphocytic infiltration of the lacrimal and salivary glands of Sjögren's syndrome (SjS) patients. SjS patients' sera contain autoantibodies to M3 muscarinic acetylcholine receptors (MAChR) that have variously been reported to have agonistic and antagonistic effects. We sought to identify consequences of chronic agonist stimulation by maintaining acinar cells from rabbit lacrimal glands for 20 h in the presence or absence of 10 microM carbachol (CCh). Exposure to CCh diminished the cells' ability to elevate cytosolic Ca2+ and secrete beta-hexosaminidase in response to acute stimulation with 100 microM CCh, but it enhanced their secretory responses to phenylephrine and ionomycin. Secretory vesicles appeared normal by electron microscopy, but confocal fluorescence microscopy revealed depletion of the secretory vesicle membrane marker, rab3D, and decreased ability to recruit secretory transport vesicles in response to acute 100 microM CCh. Additionally, the apical cortical actin cytoskeleton was disrupted and diminished compared to the basal-lateral cortical network. Subcellular fractionation analyses revealed that total membrane phase protein content was increased. The contents of beta-hexosaminidase and MAChR relative to total protein were not significantly altered, and MAChR abundance in the plasma membrane fraction was increased as the result of redistribution from endomembrane pools. However, relative cellular contents of the heterotrimeric guanosine triphosphate (GTP)-binding proteins, Gq and G11, were decreased. Additional biochemical changes included decreased contents of 47 kDa Gs and Gi3, protein kinase Calpha and rab3D and polymeric immunoglobulin (Ig) receptors; internalization of Na,K-ATPase from the plasma membranes to endomembrane compartments and decreased content of beta-hexosaminidase in the lysosomes. The observations demonstrate that chronic exposure to a MAChR agonist induces refractoriness to optimal stimulation, without causing receptor downregulation, by downregulating postreceptor-signalling mediators and effectors. The cells' secretory mechanisms for IgA and electrolytes also appear to be impaired, as does their ability to properly sort proteins to the lysosomes.

Impairing actin filament or syndapin functions promotes accumulation of clathrin-coated vesicles at the apical plasma membrane of acinar epithelial cells

In this article, we investigate the contributions of actin filaments and accessory proteins to apical clathrin-mediated endocytosis in primary rabbit lacrimal acini. Confocal fluorescence and electron microscopy revealed that cytochalasin D promoted apical accumulation of clathrin, alpha-adaptin, dynamin, and F-actin and increased the amounts of coated pits and vesicles at the apical plasma membrane. Sorbitol density gradient analysis of membrane compartments showed that cytochalasin D increased [14C]dextran association with apical membranes from stimulated acini, consistent with functional inhibition of apical endocytosis. Recombinant syndapin SH3 domains interacted with lacrimal acinar dynamin, neuronal Wiskott-Aldrich Syndrome protein (N-WASP), and synaptojanin; their introduction by electroporation elicited remarkable accumulation of clathrin, accessory proteins, and coated pits at the apical plasma membrane. These SH3 domains also significantly (p </= 0.05) increased F-actin, with substantial colocalization of dynamin and N-WASP with the additional filaments. Coelectroporation with the VCA domain of N-WASP blocked the increase in F-actin and reversed the morphological changes indicative of impaired apical endocytosis. We suggest that transient modulation of actin polymerization by syndapins through activation of the Arp2/3 complex via N-WASP coordinates dynamin-mediated vesicle fission at the apical plasma membrane of acinar epithelia. Trapping of assembled F-actin intermediates during this process by cytochalasin D or syndapin SH3 domains impairs endocytosis.

Cytoplasmic dynein participates in apically targeted stimulated secretory traffic in primary rabbit lacrimal acinar epithelial cells

A major function of the acinar cells of the lacrimal gland is the production and stimulated release of tear proteins into ocular surface fluid. We investigate the participation of cytoplasmic dynein in carbachol-stimulated traffic to the apical plasma membrane in primary rabbit lacrimal acinar epithelial cells. Confocal fluorescence microscopy revealed a major carbachol-induced, microtubule-dependent recruitment of cytoplasmic dynein and the dynactin complex into the subapical region. Colocalization studies, sorbitol density gradient/phase partitioning analysis and microtubule-affinity purification of membranes showed that some dynein and dynactin complex were associated with VAMP2-enriched membranes. Adenovirus-mediated overexpression of p50/dynamitin inhibited the recruitment and colocalization of dynein, the dynactin complex and VAMP2 in the subapical region. Nocodazole treatment and p50/dynamitin overexpression also depleted subapical stores of rab3D in resting acini, suggesting that dynein activity was also involved in maintenance of rab3D-enriched secretory vesicles. These data implicate cytoplasmic dynein in stimulated traffic to the apical plasma membrane in these secretory epithelial cells.

Tumor necrosis factor inhibitor gene expression suppresses lacrimal gland immunopathology in a rabbit model of autoimmune dacryoadenitis

PURPOSE

To evaluate the effect of tumor necrosis factor (TNF) inhibitor protein on lacrimal gland immunopathology and ocular surface disease resulting from induced dacryoadenitis.

METHODS

Autoimmune dacryoadenitis was induced in rabbits by injecting the lacrimal glands with peripheral blood lymphocytes (PBLs) activated by 5 days of coculture with autologous acinar cells in a mixed cell reaction. In the treated group, an adenoviral vector carrying the TNF inhibitor gene (AdTNFRp55-Ig) was concurrently injected with AMCR-PBL. Tear production was monitored by Schirmer test, and tears were collected for detection of TNF-inhibitor protein. Frozen sections of the glands were immunostained for expression of CD4, CD8, rabbit thymic lymphocyte antigen (RTLA), and CD18. Histological sections of lacrimal glands were examined using the TUNEL technique to monitor apoptosis.

RESULTS

Soluble TNF-inhibitor protein was detected by ELISA in tears, with titers at a maximum on day 3, declining by day 7, and undetectable by day 14. Tear production declined in the induced dacryoadenitis group but did not change when glands had been treated with AdTNFRp55-Ig simultaneously with disease induction. Tear break-up time and rose bengal staining properties were not altered by treatment. Fourteen days after the glands were injected with activated PBLs, focal mononuclear cell infiltrates were observed around ducts and venules, some of which assumed the high endothelial phenotype, and between acini. Immune cells in the infiltrates stained positive for CD4, RTLA, and CD18. Glands that received AdTNFRp55-Ig concurrently with activated PBLs had decreased numbers of CD4 cells, CD18 cells, RTLA, and apoptotic cells.

CONCLUSIONS

In vivo transduction of the lacrimal gland with AdTNFRIp55-Ig resulted in transient expression in the gland and the appearance of TNF-inhibitor protein in tears. The presence of soluble TNF-inhibitor protein partially suppressed the appearance of Sjögren's syndrome-like features of reduced tear production and the immunohistopathology associated with induced autoimmune dacryoadenitis but not tear break-up time and ocular surface disease. This may reflect immunoregulation in the lacrimal gland but not in the conjunctiva.

Lacrimal histopathology and ocular surface disease in a rabbit model of autoimmune dacryoadenitis

PURPOSE

To study the effects of induced autoimmune dacryoadenitis on lacrimal gland function, histopathology, and ocular surface disease in a rabbit model.

METHODS

One lacrimal gland was surgically excised from each experimental rabbit, and epithelial cells were purified, cultured, irradiated, and then cocultured with autologous peripheral blood lymphocytes (PBLs) for 5 days. Autoimmune dacryoadenitis was induced by injecting the autologous mixed cell reactions (AMCRs) into the rabbit's remaining lacrimal gland. Normal rabbits and rabbits with both lacrimal glands injected with nonstimulated PBLs were examined as controls. Eyes were evaluated biweekly for 8 weeks by slit-lamp biomicroscopy, Schirmer testing, tear break-up time measurement, and rose bengal examination. Sections of lacrimal glands removed at 8 weeks post-operation were immunostained using antibodies against rabbit class II major histocompatibility complex molecule (MHC-II), CD4, CD8, CD18, and rabbit thymic lymphocyte antigen (RTLA). Relative numbers of positively stained cells were quantified with a ChromaVision image analysis system.

RESULTS

During an 8-week period, a continuous decrease in tear production and stability, accompanied by a continuous increase in rose bengal staining, occurred in eyes in which AMCR-PBL had been injected into the ipsilateral lacrimal glands. Similar, though generally less severe, changes occurred in eyes contralateral to the AMCR-PBL-injected eyes. No obvious changes by 8 weeks in these parameters were found in eyes in which the lacrimal glands had been injected with nonstimulated PBLs or in the lacrimal gland-excised eyes contralateral to normal eyes. Interstitial cells in normal lacrimal glands expressed CD18 and RTLA antigens, but few expressed CD4, CD8, or MHC-II. Focal mononuclear cell infiltrates were only found in lacrimal glands from animals with induced autoimmune dacryoadenitis. These cells were predominantly positive for CD4 (7.3-fold increase), RTLA (7.8-fold increase), or CD18 (42-fold increase). MHC-II expression in interstitial and ductal epithelial cells was also significantly greater in these animals than in control animals. The mononuclear cell infiltrates were frequently found enveloping venules, some of which appeared to be high endothelial cell venules. The ductal epithelium also contained CD4 and CD8 immunopositivity, within the epithelium, at the lumenal surface, or surrounding the ducts. Occasionally CD4 and CD8 immunopositive cells could be identified within the acinar lumens.

CONCLUSIONS

Injection of activated PBLs (i.e., AMCR-PBLs) in the lacrimal gland induces autoimmune dacryoadenitis with immunopathologic features similar to those of Sjögren's syndrome. The lacrimal immunopathology is accompanied by typical clinical manifestations of dry eye syndrome. The persistent significant dry eye does not appear to result just from failure of the diseased gland but from a more general dysfunction of the surface secretory tissues.

Diverse perturbations may alter the lacrimal acinar cell autoantigenic spectra

Lacrimal gland acinar cell autoantigens in Sjögren's syndrome include both intracellular proteins and plasma membrane proteins, to which the immune system normally must be tolerant. Attention has largely focused on the roles apoptotic cell death may play in exposing sequestered autoantigens and novel surface epitopes. We hypothesize that perturbations of ongoing membrane traffic in intact, functioning cells may also increase autoantigen exposure. We review the vesicular traffic between acinar cell basal-lateral plasma membranes (blm) and endomembrane compartments, then describe experiments in which isolated acinar cells were stimulated with epidermal growth factor (EGF), lysed, and analyzed by sorbitol gradient centrifugation. Whereas the cholinergic agonist, carbachol, impairs traffic from the trans-Golgi network to prelysosomes, causing Golgi, secretory, and lysosomal proteins to reflux into domains of the trans-Golgi network that communicate with the blm and to accumulate in the blm, EGF specifically causes a 2.6-fold (P < 0.05) increase in the beta-hexosaminidase content of the blm fraction, apparently by impairing traffic from early endosomes to prelysosome. We, therefore, suggest that a variety of physiologic stimuli may alter the spectra of autoantigens acinar cells secrete to the interstitium, express in their blm, and present via MHC Class II molecules after proteolytic processing.

Expression of IL-10 and TNF-inhibitor genes in lacrimal gland epithelial cells suppresses their ability to activate lymphocytes

PURPOSE

To determine whether the expression of either interleukin-10 (IL-10) or tumor necrosis factor (TNF) inhibitor genes in transduced rabbit lacrimal gland epithelial cells suppresses lymphocyte proliferation in an autologous mixed cell reaction, an apparent in vitro model of autoimmune dacryoadenitis.

METHODS

Purified lacrimal gland epithelial cells, transduced with an adenovirus vector carrying either viral IL-10 or TNF-inhibitor genes, were used to study their effects on the proliferation of autologous lymphocytes as monitored by 3H-thymidine incorporation in a mixed cell reaction. After transduction, both epithelial cells and lymphocytes were cultured separately for 2 days and then epithelial cells were irradiated. Equal numbers of both cell types were then cocultured together for 5 days. Cocultures were pulsed with 3H-thymidine and isotope incorporation was determined. Gene expression was detected by enzyme-linked immunosorbent assay and Western blots.

RESULTS

Lymphocyte proliferation was stimulated by epithelial cells and 3H-thymidine incorporation was significantly greater in these cocultures than in controls. The proliferation was significantly diminished in the presence of transduced cells producing either IL-10 or TNF inhibitor.

CONCLUSIONS

Transduction of lacrimal gland epithelial cells with adenovirus vectors encoding for either IL-10 or TNF-inhibitor proteins leads to expression of functional proteins capable of suppressing lymphocyte proliferation. Thus, lacrimal gland epithelial cells are a plausible target for gene therapy methods meant to produce immunoregulatory proteins.

Growth of purified lacrimal acinar cells in Matrigel raft cultures

The objective of this study was to develop a tissue culture system which closely mimics the in situ lacrimal gland for improved study of lacrimal acinar cell physiology. Highly purified preparations of lacrimal acinar cells from adult female New Zealand White rabbits were isolated and grown in suspension culture in the form of Matrigel 'rafts', i.e., aggregates of acinar cells enclosed within a Matrigel coating. The rafts were seeded onto Matrigel-coated culture plates and their growth was followed for up to 28 days. Immunohistochemistry was used to demonstrate the cellular sites of prolactin (PRL), epidermal growth factor (EGF), basic fibroblast growth factor (FGF-2), secretory component (SC) and major histocompatibility complex class-II molecules (MHC-II) within the acinar cells. By 3 days the cultures contained numerous, well-formed acini enclosed within the Matrigel. The acinar epithelial cells demonstrated histotypic polarity, with large, pale-staining, secretory granules aggregated adjacent to the lumen, and exocytotic release of secretory material into the lumen. From 5-10 days the pale-staining secretory granules decreased in number, while the lumenal contents of the acini increased in staining density. Throughout the culturing period as the pale-staining, secretory granules decreased in number, smaller more densely stained, secretory granules increased in number. The number of cells and size of acinar clusters increased steadily throughout the culturing period, and acini frequently achieved dimensions in excess of 0.5 mm. Increases in the size of acinar clusters were often accompanied by an increase in the size of the lumen. Frequently the lumen and its contents bulged asymmetrically towards one edge of the acinus. Immunhistochemistry demonstrated PRL and EGF within the lumens and within the apical cytoplasm of the acinar cells. Acini were strongly immunopositive for SC throughout the 28 day culture period, whereas immunopositivity for MHC-II molecules was strong initially, but diminished dramatically by 21 days. Immunostaining for FGF-2 was most intense on days 1 and 3, with staining throughout the cytoplasm, but became progressively more localized to the periphery of the acini as the culture period lengthened. In cultures of 1-28 days duration, Western blots of cell lysates demonstrated a major band (approximately 40 kDa) for PRL in 3-28 day preparations; a major band (approximately 80 kDa) for SC in 3 day and 7 day preparations that decreased in intensity in 14-28 day preparations; and a major band (approximately 23 kDa) for MHC-II protein in 1-21 day preparations that decreased in intensity in 28 day preparations. Lysosomes increased in number with time in culture, becoming a dominant cytoplasmic feature in 21 and 28 day cultures. Carbachol stimulation of 4 day rafts resulted in increased release of beta-hexosaminidase and SC from the rafts. The authors conclude that Matrigel rafts containing purified lacrimal gland acinar cells offer a highly advantageous system for study of lacrimal acinar cell function and one that correlates well with the in situ gland.