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1 From the Department of Ophthalmology, Tokyo Dental College, Chiba, Japan; the 2 Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan; the 3 Oral Health Science Center, Tokyo Dental College, Chiba, Japan; and the 4 2nd Department of Internal Medicine, Saitama Medical Center, Saitama, Japan.
| Abstract |
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METHODS. Four patients with MD and 5 with SS were recruited, on whom were performed Schirmer test I (Schirmer test without anesthesia), Schirmer test with nasal stimulation, and vital staining of the ocular surface. The lacrimal gland was then biopsied and the tissues stained with CD3, CD4, CD8, B220, APO2.7, Fas, and Fas ligand (Fas-L) antibodies.
RESULTS. Although regular Schirmer test results in the MD group were less than 10 mm, those with nasal stimulation, 38.1 ± 3.4 mm, were significantly greater than the SS group. There were minimal ocular surface changes in MD. Morphologic staining with hematoxylin and eosin was identical in both groups, but the acinar cells were stained with APO2.7 only in the SS group. There was strong Fas and Fas-L staining in SS patients but not in those with MD.
CONCLUSIONS. Lacrimal gland acinar cells in those with MD maintained their function and were not programmed for cell death. The sicca syndrome was not observed in MD patients. Although the pathology is similar for MD and SS, the difference in acinar cell apoptosis and function can explain clinical differences.
| Introduction |
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From the ophthalmologists perspective, the ocular surface features of MD and SS differ from each other. SS can involve advanced squamous metaplasia, causing greatly diminished lacrimal function and loss of both basic and reflex tearing,5 6 resulting in depletion of tear components essential to the ocular surface epithelium. In contrast, MD patients respond well to stimulation by secreting reflex tears, as described in the original paper of Mikulicz.7 We speculated that MD patients maintain lacrimal gland function despite the similarities in pathology to SS.
We recently speculated that lacrimal gland acinar cells in SS undergo programmed cell death.8 9 Normal-looking acinar cells may or may not be functional depending on the status of this apoptosis. In the present study, we compared the lacrimal gland function and pathologic changes of MD and SS.
| Methods |
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We diagnosed dry eye according to the criteria previously
reported11
: symptoms of dry eye, abnormalities of tear
dynamics as determined by either one of the following tests: Schirmer
test I (Schirmer test without anesthesia;
5 mm), clearance test
(
8x), cotton thread test (
10 mm) or tear break-up time (BUT;
5
seconds), and ocular surface abnormalities as manifested by rose bengal
(
3) or fluorescein vital staining (
3). Rose bengal stains the
conjunctiva and cornea, whereas fluorescein is only evaluated in the
cornea. Patients who satisfied the three criteria noted above were said
to have "dry eye."11
This study followed the tenets of
the Declaration of Helsinki and informed consent was obtained.
Patient Selection
Four MD patients (1 male, 3 female; [mean ± SD], 59 ± 4 years) were referred to our Department of Ophthalmology, Tokyo
Dental College, Ichikawa General Hospital, between 1991 and 1997. Five
consecutive SS patients were recruited at the same institution between
January 1997 and March 1997.
Tear Dynamics
We evaluated tear dynamics by measuring the tear BUT and
performing the Schirmer test without anesthesia. Maximum tear
production was determined by the Schirmer test with nasal stimulation.
Briefly, the patients underwent the Schirmer test I (Schirmer test
without anesthesia) for 5 minutes.5
A small cotton
swab was then inserted into the patients nose toward the entrance of
the ethmoid sinus and was kept in place for 5 minutes while a Schirmer
strip was placed in the conjunctival sac.6
Ocular Surface Evaluation
Using our double staining method, we put 2 µl of
preservative-free combined solution of 1% rose bengal and 1%
fluorescein into the conjunctival sac.12
The degree of
rose bengal staining in the temporal and nasal conjunctiva and cornea
was quantified on a scale of 0 to 3, so that the maximum score from
each eye was 9. Fluorescein staining was also rated from 0 to 9 but
only in the cornea.
We used the method of Tseng13 to evaluate squamous metaplasia, performing impression cytology in 2 patients with MD and 4 with SS.
Lacrimal Gland Biopsy
In the 4 MD patients, we performed a biopsy of the
lacrimal gland through the skin, whereas in the SS patients, the
lacrimal gland was biopsied from the conjunctival sac in the routine
manner. After the patients were topically anesthetized (0.4%
benoxynate; Benoxyl; Santen Pharmaceuticals, Osaka, Japan), we resected
a (1 mm x 1 mm) palpebral portion of the lacrimal gland through
the temporal upper tarsus.14
The procedure took only 2 to
3 minutes, after which a pressure patch was applied for 5 minutes to
prevent bleeding.15
16
Topical antibiotics (Tarivid;
Santen Pharmaceuticals) were used 4 times a day for 3 days after the
biopsy. We fixed the specimens in formalin (n = 4 in
MD, n = 5 in SS) and OTC (n = 3 in MD,
n = 4 in SS) and performed the histologic
examination according to the criteria of Xu et al.14
and
Greenspan.16
Lacrimal gland biopsy is a common and recommended examination criteria of Japanese Sjögrens Syndrome Research Group and is supported by the Japanese Ministry of Health and Welfare. Details of this and other procedures and possible complications were fully explained to the patients before the biopsy and other tests.
Immunohistochemistry
After fixation for 10 minutes with cold acetone, we blocked for 20
minutes the lacrimal gland frozen sections (3 MD and 5 SS ones) with
phosphate-buffered saline containing 10% normal goat serum. (The
lacrimal gland specimens of the first patient were not made into frozen
section, and only the formalin-fixed specimen was available.) The
samples were then incubated for 30 minutes with monoclonal antibodies
(mAb) anti-CD4, anti-CD8, anti-CD21 (Becton Dickinson, San Jose, CA),
anti-CD103 (Pharmingen, San Diego, CA), APO2.7 (Immunotech, Marseille
Cedex, France), anti-Fas (UB2; MBL, Nagoya, Japan). AntiFas ligand
(antiFas-L; N-20; Santa Cruz Biotechnology, Santa Cruz, CA)
monoclonal antibody was used as a first antibody. The first antibodies
were detected with horseradish peroxidaseconjugated goat anti-mouse
IgG antibody, fluorescein isothiocyanateconjugated goat anti-mouse
IgG antibody (Bio Source, Camarilo, CA), or Oregon green
514conjugated goat anti-rabbit IgG antibody (Molecular Probes,
Leiden, the Netherlands). After washing with phosphate-buffered saline,
we treated the sections with a solution of 0.05% 3,3,-diaminobenzidine
and 0.005% H2O2 in
TrisHCl buffer (0.05 M, pH 7.6) for 5 minutes, washed them with
distilled water, and counterstained them with hematoxylin. To
quantitatively compare the expression of APO2.7 reactive protein, Fas,
and Fas-L, we used a laser image analyzer equipped with a confocal
optical system (model ACAS 570; Meridian Instruments, Okemos,
MI) to visualize the sections stained with immunofluorescein. The
following ACAS parameters were used: wavelength = 488 nm, dichroic
filter = 510 nm, step size = 1.0 µl, laser power = 200
mW, and scan strength = 10%. Background fluorescence was
determined by fluorescence density measurement of lacrimal gland
section from non-SS patients stained with control IgG and fluorescein
or Oregon greenconjugated secondary antibody. The average of positive
signal intensity was determined by measurement of 5 fields scanned in
the lacrimal gland by the ACAS 570.
The same biopsy specimens were used for both light microscopy and immunochemistry.
Statisical Analysis
The unpaired Students t-test was used in this study.
| Results |
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The staining with APO2.7 of acinar cells in SS, but not in MD (Fig. 5A) , suggests that although both diseases involve lymphocyte infiltration, only the acinar cells in the former undergo apoptosis. Staining with the APO2.7 antibody is thought to indicate the early phase of apoptosis that is observed in the acinar cells of SS patients (Fig. 5B ). In contrast, the acinar cells of MD patients did not stain with the APO2.7 antibody.
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| Discussion |
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MD was first described in 1937 as a benign, asymptomatic, symmetrical enlargement of the lacrimal and salivary glands.17 Histologic examination revealed atrophy of the acinar parenchyma and diffuse replacement by lymphoid tissue. In 1953, Morgan and Castleman described the relation between MD and SS, emphasizing the identical morphologic appearance of the salivary and lacrimal glands of the two diseases.2 3 This is compatible with our results, including the identification of the CD4+-, CD8+-, and CD21+-infiltrating lymphocytes. They also noted similar symptoms and associated conditions (including keratoconjunctivitis sicca, xerostomia, and rheumatoid arthritis) and concluded that the condition characterized by chronic enlargement of the salivary and lacrimal glands, which had previously been called MD, may be a less highly developed variant of a larger symptom complex, SS. Here we propose that, although the two diseases look similar histopathologically, there are important functional differences in the lacrimal gland.
Lacrimal gland function has long been evaluated by the Schirmer test I (Schirmer test without anesthesia).18 However, this simple test cannot measure maximal lacrimal gland production and, thus, cannot differentiate between SS and other forms of dry eye.5 We have emphasized the importance of the modified Schirmer II test with nasal stimulation, which assesses reflex tearing.6 When the lacrimal gland maintains the capacity for reflex tearing, as it does in MD, the ocular surface epithelium can receive essential tear components and maintain its morphology.19 The squamous metaplasia in SS is at least partially caused by the lack of these tear components.
The distinction between lymphocyte infiltration and tissue destruction has been noted in graft rejection and other transplant-related conditions and in autoimmune diseases.20 21 22 23 24 25 Although almost all cases involve lymphocyte infiltration, only some show tissue destruction and functional impairment (rejection or recurrence of the disease); lymphocyte infiltration and tissue destruction should, thus, be considered a separate process. Lymphocyte recruitment from the blood vessels into the tissue is mediated by the integrin families, chemokines, and cytokines. Whether the lymphocytes remain in the tissue depends on the adhesion between the lymphocytes and the tissue. Because some lymphocytes in the tissue do not express Fas-L, perforin, or granzyme, they do not contribute directly to tissue destruction.26 The evidence for the nondestructive nature of the lacrimal gland lymphocytes in MD is both functional (the preservation of reflex tearing) and immunohistochemical (the lack of apoptotic features in the acinar cells).
Although the inability of SS patients to produce reflex tears is not well understood, staining by APO2.7 in the acinar cells suggests that those cells are in the very early stage of mitochondrial dysfunction in apoptotic cell death.27 The inability of TdT-dUTP terminal nick-end label staining to detect differences between SS and non-SS lacrimal glands (data not shown) also suggests that the apoptosis is in the early phase.
Tissue destruction is caused by cytolytic T cells mediated through perforin or Fas lytic pathways.28 We showed that infiltrated lymphocytes in SS, but not MD, express a large amount of Fas and Fas-L, although further study is necessary to determine the role of Fas and Fas-L in acinar cell destruction.23 The limited expression of Fas and Fas-L in the lacrimal gland of MD patients may explain why the massive lymphocyte infiltration is not accompanied by acinar cell destruction.
Because morphologic appearance alone may give an equivocal diagnosis, some of the new biopsy parameters we have identified should be considered when evaluating these patients. In particular, if the sicca syndrome is to be taken as pathohomonic of SS, then exocrine gland dysfunction should be emphasized over lymphocyte infiltration in making the diagnosis. Although patients with MD have lymphocyte infiltration in the exocrine glands, they do not lose glandular function, possibly because of no destruction of acinar cells.
Missing components in tears may cause ocular surface disorders;
however, there is another possibility that some inflammatory components
such as interferon-
, which is produced by infiltrated lymphocytes in
SS, might worsen the ocular surface condition. These areas should be
studied further in the future.
| Acknowledgements |
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| Footnotes |
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Submitted for publication April 28, 1998; revised August 6 and October 9, 1998; accepted November 12, 1998.
Commercial relationships policy: C5(KT, HF).
Corresponding author: Kazuo Tsubota, Department of Ophthalmology, Tokyo Dental College, 11-13 Sugano 5 Chome, Ichikawa-shi, Chiba, Japan 272-8513. tsubota{at}tdc.ac.jp
| References |
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