HPV-Associated Squamous Cell Carcinoma of the Eyelid: Diagnostic Utility of p16 Immunohistochemistry and mRNA In Situ Hybridization.

BACKGROUND: High-risk (HR) Human papillomavirus (HPV) has been implicated in pathogenesis of squamous cell carcinomas (SCC) at several sites with mucocutaneous junctions, including the head and neck. SCC is the second most common eyelid malignancy. However, its association with transcriptionally active HR-HPV has not been adequately studied. METHODS: Two index cases of eyelid HPV-associated SCC are described in detail. A retrospective cohort of eyelid SCC was examined for p16 immunoexpression. Cases demonstrating p16 positivity or equivocal staining were subjected to high-risk HPV mRNA in situ hybridization (ISH). Quantitative real-time PCR (qPCR) was performed in mRNA ISH-positive cases for HPV genotyping. RESULTS: The two index patients were older adult females, with upper eyelid tumours. On histology, both tumours were non-keratinizing SCC with trabecular and nested architecture reminiscent of oropharyngeal HPV-associated non-keratinizing SCC, prompting p16 immunohistochemistry, which was positive. HR-HPV mRNA ISH was positive, and qPCR detected HPV16 in both cases. Three of 20 (15%) archival cases showed p16 immunopositivity and two (10%) showed equivocal staining. However, mRNA ISH was negative. All cases showing p16 immunostaining and lacking HR-HPV were keratinizing SCCs. Thus, 9% of all eyelid SCC examined demonstrated HR-HPV. CONCLUSION: The prevalence of HR-HPV in eyelid SCC is low in Indian patients. HPV-associated SCC may mimic commoner eyelid carcinomas as it lacks overt keratinization. In basaloid-appearing eyelid carcinomas, p16 immunopositivity should be followed by reflex HR-HPV mRNA ISH, as p16 immunohistochemistry alone has low specificity. The prognostic role, if any, of HPV association needs further evaluation.

Lipidomic analysis of meibomian gland secretions from the tree shrew: Identification of candidate tear lipids critical for reducing evaporation.

Lipids secreted from the meibomian glands form the outermost layer of the tear film and reduce its evaporation. Abnormal changes in the quantities or compositions of lipids present in meibomian gland secretions (meibum) are known to lead to dry eye disease, although the underlying mechanism is not yet well understood. The tree shrew is the non-primate mammal most closely related to humans. To assess the utility of the tree shrew as a model for the study of dry eye disease, we analyzed the lipid profile of tree shrew meibum using an untargeted ESI-MS and MS/MSall shotgun approach. The resulting lipidome shared many similarities with human meibum, while displaying some interesting differences. For example, several classes of lipids, including wax esters, cholesteryl esters, diesters, and (O-acyl)-ω-hydroxy fatty acids, had relatively longer chain lengths in tree shrew meibum. These increases in length may promote more effective reduction of tear evaporation in the tree shrew, which likely underlies the much longer blinking interval of this mammal. Our results suggest that the tree shrew could be an effective model for the study of dry eye.

Sialidase Unmasks Mucin Domain Epitopes of Lubricin.

Lubricin is a secreted, mucin-like glycoprotein and proteoglycan abundant in synovial fluid that provides boundary lubrication and prevents cell adhesion in synovial joints. The antilubricin S6.79 monoclonal antibody recognizes an O-linked glycopeptide epitope in lubricin's mucin domain. The central, long mucin domain of lubricin is extensively O-glycosylated with Gal(ß1-3)GalNAc-O-Ser/Thr, and about two thirds of the O-glycosylated sites are capped with sialic acid. Our aim was to determine whether removal of sialic acid by sialidase could improve the detection of lubricin in a number of human tissues using the S6.79 monoclonal antibody. Sialidase treatment caused a dramatic increase in antibody reactivity in human pericardium, splenic capsule and trabeculae, plasma, serum, eye sleep extract, and liver sinusoids. Sialidase had minimal effect on S6.79 antibody reactivity with lubricin in synovial fluid and synovial tissue. These observations suggest that the origin of lubricin in blood may be different from that in synovial fluid and that desialylation of lubricin is essential for unmasking epitopes within the mucin domain.

The relationship between tear meniscus regularity and conjunctival folds.

PURPOSE: To investigate the capability of a new portable digital meniscometer (PDM) to measure tear meniscus radius (TMR) and tear meniscus height (TMH) at different locations along the lower lid and to evaluate relationships between tear meniscus regularity and the degree of lid-parallel conjunctival folds (LIPCOFs). METHODS: Using the PDM, the TMR and TMH of 42 subjects were measured at three locations along the lower lid of one eye: central, perpendicularly below the pupil center (TMR-C, TMH-C), and temporal (TMR-T, TMH-T) and nasal (TMR-N, TMH-N), perpendicularly below the limbus. Nasal and temporal LIPCOF grades were recorded. Correlations between the measurements were analyzed using the Pearson coefficient (or Spearman rank in nonparametric data), and the differences were evaluated by paired t tests or analysis of variance and post hoc Fisher least significant difference test. RESULTS: Temporal TMR was 0.041 mm flatter (p = 0.002) and TMH-T was 0.063 mm higher (p < 0.001), whereas TMR-N was 0.026 mm flatter (p = 0.038) and TMH-N was 0.046 mm higher (p < 0.001) than TMR-C and TMH-C. Temporal LIPCOF grades were significantly correlated to temporal alterations in TMH (r = 0.590; p < 0.001) and TMR (r = 0.530; p < 0.001), and nasal LIPCOF grades were significantly correlated to nasal alterations in TMH (r = 0.492; p = 0.001) and TMR (r = 0.350; p = 0.023). CONCLUSIONS: The PDM is able to noninvasively detect significant differences in TMR and TMH along the lower lid. The flatter TMR and higher TMH at the nasal and temporal locations are associated with increased LIPCOF. Because increased LIPCOF scores may affect tear film disruption along the lower lid, measuring TMR and TMH at the central position below the pupil may provide the best intersubject reliability.

Confirmation of the presence of squalene in human eyelid lipid by heteronuclear single quantum correlation spectroscopy.

(1)H-NMR spectroscopy has been used to quantify squalene in meibum and sebum. Squalene has many beneficial properties and its loss on the surface of skin upon ultraviolet light exposure or in the tear film with dry eye could be detrimental. In this study, we confirm the NMR proton resonance assignments of squalene, squalene in human meibum, and in human eyelid lipid using heteronuclear single quantum correlation spectroscopy. Our results confirm the presence of squalene in eyelid lipid. We speculate that the squalene in eyelid lipid could be secreted from sebaceous glands. The NMR resonances between 5.2 and 5.0 ppm, characteristic of the =CH of squalene, were resolved in the spectrum of human meibum and used to estimate that 1 % or less of squalene is present in meibum. However, the resonance assignments of squalene in meibum were not confirmed. The characteristics of squalene including its anti-inflammatory, antioxidant, and antibacterial qualities suggest that the presence of a squalene film is beneficial. Its loss in human meibum from patients with dry eye could be detrimental and contribute to the symptoms observed in these patients.

"SP-G", a putative new surfactant protein--tissue localization and 3D structure.

Surfactant proteins (SP) are well known from human lung. These proteins assist the formation of a monolayer of surface-active phospholipids at the liquid-air interface of the alveolar lining, play a major role in lowering the surface tension of interfaces, and have functions in innate and adaptive immune defense. During recent years it became obvious that SPs are also part of other tissues and fluids such as tear fluid, gingiva, saliva, the nasolacrimal system, and kidney. Recently, a putative new surfactant protein (SFTA2 or SP-G) was identified, which has no sequence or structural identity to the already know surfactant proteins. In this work, computational chemistry and molecular-biological methods were combined to localize and characterize SP-G. With the help of a protein structure model, specific antibodies were obtained which allowed the detection of SP-G not only on mRNA but also on protein level. The localization of this protein in different human tissues, sequence based prediction tools for posttranslational modifications and molecular dynamic simulations reveal that SP-G has physicochemical properties similar to the already known surfactant proteins B and C. This includes also the possibility of interactions with lipid systems and with that, a potential surface-regulatory feature of SP-G. In conclusion, the results indicate SP-G as a new surfactant protein which represents an until now unknown surfactant protein class.

Measuring and predicting eyelid spectral transmittance.

The purpose of the present study was to objectively quantify the spectral transmittance of the eyelid. Reported here are data acquired using a technique that was developed to provide practical and accurate measurements of eyelid transmittance across the visible portion of the electromagnetic spectrum. The empirical data were analyzed in terms of the absorption and scattering characteristics of the constituents of skin to develop a method for predicting eyelid transmission. Results showed that the eyelid has a much higher optical density at short wavelengths than previously published. The mean ± standard deviation (s.d.) optical density of the eyelid from 450 to 650 nm was 2.1 ± 0.3 with an optical density range among subjects of approximately 1.0. The study results indicate that skin pigmentation is poorly correlated with eyelid transmission; eyelid transmission is most affected by wavelength-independent macromolecules in the eyelid as well as its overall thickness.

Quantification of human sebum on skin and human meibum on the eye lid margin using Sebutape®, spectroscopy and chemical analysis.

PURPOSE: The purpose of this study was to determine if the variability in the amount of lid margin meibum is from donor-to-donor or from day-to-day variations and to determine if meibum from donors with meibomian gland dysfunction (MGD) had altered levels of casual eyelid meibum or skin sebum. METHODS: Lipid absorbent Sebutape(®) was used to collect sebum or meibum. Samples were collected from six donors without dry eye and 21 donors with MGD. Lipid absorbed to Sebutape(®) was quantified using infrared and visible absorbance spectroscopy. RESULTS: The amount of sebum from donors with MGD and donors without MGD was not significantly different. The amount of casual meibum from normal donors was 50% lower than that for donors with MGD using the spectroscopic assay, but was not significantly different using the chemical assay. The frequency and bandwidth of the infrared carbonyl band from sebum samples was significantly higher than that for meibum samples which indicates the carbonyls are in a different "dielectric" environment. The average relative standard deviation for the casual level of meibum and the level of sebum suggests that the 49% relative standard deviation of casual meibum measured once for each subject using a meibometer may have been due to day-to-day variations and not necessarily due to variations between individuals. The values measured using two different assays were correlated and therefore reliable. CONCLUSIONS: The idea that tear film instability is associated with the quantity of lid margin lipid is not supported by this study because the quantity did not change with MGD. The amount of forehead sebum was not a bio-marker for MGD. Sebutape(®) is an excellent vehicle to remove tenths of a milligram of meibum from the eyelid and sebum from skin for experimental analysis.

PCR-quality DNA isolation from human bronchial aspirates and buccal and eyelid swabs by a simple procedure based on alkaline lysis.

There are only a few systematic reports about DNA extraction from routine diagnostic cytological specimens. An inevitable drawback of such techniques is increased spending of time and funds required for obligatory DNA purification. To implement a simple protocol for human DNA isolation from cytological specimens related to lung cancer, bronchial aspirates together with samples collected by swabbing of the inner cheek and eyelid were used. By combining alkaline and temperature lyses it was possible to isolate DNA solution ready for PCR in less than an hour. Testing the method used for amplification of sex chromatin gene fragments showed that it is highly efficient. The presented protocol preserves high-quality DNA that is suitable for PCR-based assays.

The structure and possible functions of the milkfish Chanos chanos adipose eyelid.

Basic histological sections (with different staining methods) and scanning electron microscopy (SEM) examinations showed that there were three distinctive layers in the adipose eyelid of milkfish Chanos chanos, which is found in the cephalie region and covers the entire eye. The outer and inner layers were epithelial tissues and the middle layer was composed of connective tissue formed by type I collagen fibrils. No adipose tissue was found in any of the three layers of the so-called adipose eyelid. Examination by transmission spectrophotometer showed that the adipose tissue could filter out ambient light with a wavelength shorter than 305 nm. A photoretinoscope was used to investigate whether the adipose eyelid influenced the mechanism of eye focusing. Eye diopter values did not differ before or after eyelid removal, which indicated that the adipose eyelid did not play a role in eye focusing. In light of these findings, it is suggested that the adipose eyelid serves to block exposure of harmful ultraviolet light into eyes and may also to offer some protection against impact to the eye in the aquatic environment.

Lymphatic vessels in human eyelids: an immunohistological study in dermatochalasis and chalazion.

We investigated lymphatic morphology and expression of endothelin (ET-1) axis molecules in human eyelids affected by an inflammatory state (chalazion) and an age-related degenerative condition (dermatochalasis). Lymphatics were immunohistologically detected by D2-40/LYVE-1 staining. Absorbing lymphatic vessels were localized in papillary dermis and around skin appendages with distinctive morphology. In chalazion, D2-40 reactive flattened lymphatic profiles were compressed by inflammatory infiltrate; in dermatochalasis, large fully opened lymphatics were observed, with a significantly wider total area (lymphatic lumina/200x field; p < 0.05). The lymphatic density (number/200x field) in the two groups was within the same range. Lymphatic dilation is possibly dependent on reduction and fragmentation of the dermal elastic network as well as of oxytalanic fibers in the papillary dermis of dermatochalasis, as shown by Weigert's reaction. Multifunctional peptide ET-1, involved in vasomotion, inflammation and connective proliferation, was faintly and discontinuously localized on lymphatics, as was its type A receptor. In contrast, the consistent expression of type B receptor indicates that lymphatic endothelium is a physiological target for ET-1, whose effects are modulated by multiple pathophysiological conditions. Thus, vasoactive factors play a role in the physiology of richly vascularized eyelids, and therefore, morphofunctional characterization of lymphatic vessels may be useful in suggesting treatment options.

On the lipid composition of human meibum and tears: comparative analysis of nonpolar lipids.

PURPOSE: To qualitatively compare the nonpolar lipids present in meibomian gland (MG) secretions (samples T1) with aqueous tears (AT) collected from the lower tear menisci of healthy, non-dry eye volunteers using either glass microcapillaries (samples T2) or Schirmer test strips (samples T3). METHODS: Samples T1 to T3 were analyzed with the use of high-pressure liquid chromatography/positive ion mode atmospheric pressure chemical ionization mass spectrometry. Where possible, the unknown lipids were compared with known standards. RESULTS: Samples T1 had the simplest lipid composition among all the tested specimens. Samples T2 and T3 were similar to each other but were noticeably different from samples T1. In addition to all the compounds detected in samples T1, lower molecular weight wax esters and other compounds were found in samples T2 and T3. No appreciable amounts of fatty acid amides (e.g., oleamide), ceramides, or monoacyl glycerols were routinely detected. The occasionally observed minor signals of oleamide (m/z 282) in samples T3 were attributed to the contamination of the samples with common plasticizers routinely found in plastic ware extractives and organic solvents. CONCLUSIONS: The MG is a prominent source of lipids for the tear film. However, it would have been a mistake to exclude from consideration other likely sources of lipids such as conjunctiva, cornea, and tears produced by the lacrimal glands. These data showed that lipids in AT are more complex than MG secretions, which necessitates more cautious interpretation of the functions of the latter in the tear film.

Organ representation areas of different internal organs localized on the eyebrows & eyelids by the Bi-Digital O-Ring Test electromagnetic resonance phenomenon between 2 identical molecules--Part I: Detection of increased markers for cancer & heart disease from white hairs on the eyebrows and marked decrease in the markers after taking one optimal dose of DHEA.

Organ representation areas of different internal organs were localized on the eyebrows for the first time in 2005 and localized on the surrounding tissue around the eye in 2008 using the Bi-Digital O-Ring Test (BDORT) electromagnetic resonance phenomenon between 2 identical tissue. The appearance of white hairs at specific organ representation areas of eyebrows represent an abnormal condition of the specific internal organ if the BDORT grading is (-)4 or a higher negative value. When one of these white hairs on the eyebrows is examined at any location along its entire length by the BDORT, if the grading is a very abnormal negative value of (-)6 or a higher (-) value, significantly abnormal conditions exist or existed at the corresponding time at the specific location of the hair. The heart representation area on the eyebrow is located nearest to the bridge of the nose on each side, where abnormally increased BNP (Brain Natriuretic Peptide) and cardiac Troponin I content is detected on the part of the white hair where the BDORT grading is (-)6 or a higher negative value. In the very abnormal part of the white hair representing the heart, Asbestos, TXB2, and PLGF (Placental Growth Factor) are markedly increased, while DHEA is markedly reduced. If Integrin alpha5beta1 and Oncogene C-fos Ab2 are more than 5-10 ng (BDORT units), malignancy can be suspected. When one optimal dose of DHEA, 8.5 mg, was taken once, normal body tissue telomere was increased from less than 1 ng (during which time the patient experienced extreme tiredness and frequent urination), to 525 ng (BDORT units), not only did severe tiredness & frequent urination completely disappear, but also the white hair representing the left ventricle changed to black hair, and the semi-transparent white hair representing the kidney changed to a non-transparent white hair, with significant decreases in the abnormal parameters. Thus, it is possible to detect unrecognized serious heart conditions or early-stage cancer that are currently present or that were present in the recent past by examining the white hairs of the eyebrows, and these diseases can be improved by one optimal dose of DHEA or Astragalus.

A mathematical model of tear mixing under the lower lid.

PURPOSE: The degree of tear mixing in various parts of eyes plays an important role in determining some important aspects of tear dynamics. This study develops a mathematical model of tear mixing in the lower conjunctival sac. METHOD: Tear mixing in the lower conjunctival sac is modeled using Taylor dispersion. The concentration of instilled solutes is obtained numerically from an equation set that integrates the mass balance of solutes in the lower conjunctival sac and the exposed tear film. RESULTS: The time for dye to appear in the exposed tear film and the time for maximal dye concentration after instillation into the lower conjunctival sac vary for different amplitudes and frequencies of lid motion. The time scales for mixing are in qualitative agreement with experiments reported in the literature. CONCLUSION: This study supports the hypothesis that the tear mixing in the lower conjunctival sac is driven by Taylor dispersion caused by lid/globe movements during blinking.

Nerve growth factor and corneal wound healing in dogs.

Nerve growth factor in the tear film and corneal epithelium is hypothesized to play an important role in ocular surface maintenance and corneal wound healing. The purpose of this study was to determine the expression of nerve growth factor and its high affinity (trkA) receptor in tears, cornea, and lacrimal glands of normal dogs, the modulation of nerve growth factor and its trkA receptor during corneal wound healing, and the effect of topical nerve growth factor application on canine corneal epithelial wound healing. In the first of three experiments, the nerve growth factor content of tears, corneal epithelium, lacrimal gland, and 3rd eyelid gland was determined in normal dogs by enzyme-linked immunosorbent assay and the expression of nerve growth factor and its trkA receptor were evaluated in the cornea and lacrimal glands by immunohistochemistry. In a second experiment, unilateral corneal epithelial defects were created, and tissues were evaluated for changes in nerve growth factor or trkA expression for 1 week. In a third experiment, bilateral corneal epithelial defects were created and the right eyes in each animal were treated 4 times daily with either recombinant human nerve growth factor, murine nerve growth factor, or nerve growth factor-blocking antibody. The results of this study showed that nerve growth factor levels in normal dog tears, corneal epithelium, third eyelid gland and lacrimal gland were 15.4+/-4.6 ng ml(-1), 33.5+/-12.3, 52.4+/-17.4 and 48.8+/-9.4 ng g(-1), respectively. NGF and trkA receptors were identified by immunohistochemistry in all tissues examined. After unilateral corneal wounding, nerve growth factor concentration increased in the tears bilaterally for 3 days, especially in the wounded eye, and then returned to pre-wounding values. Nerve growth factor content, and immunohistochemical staining for nerve growth factor and trkA, increased significantly in the ipsilateral cornea epithelium following unilateral wounding. Nerve growth factor concentrations in lacrimal and third eyelid glands also increased bilaterally (p<0.01) after unilateral wounding. Time to wound closure and rate of epithelial migration did not differ significantly between nerve growth factor-treated, nerve growth factor antibody-treated, and control eyes. In conclusion, nerve growth factor is present under resting physiologic conditions in normal canine tears, and nerve growth factor and its trkA receptor are present under resting conditions in normal canine corneal epithelium, lacrimal gland and third eyelid gland. Nerve growth factor is elevated in the tears, cornea, and lacrimal glands after corneal epithelial wounding; however, topical application of nerve growth factor, or its blocking antibody does not modulate corneal wound healing in the normal dog eye.

An immunohistochemical study of the extracellular matrix of the tarsal plate in the upper eyelid in human beings.

The superior tarsus is a plate of tissue that stiffens the upper eyelid, gives it support and determines its form. The purpose of the present study was to relate the composition of its extracellular matrix to its function and to report regional differences that may influence the activity of its Meibomian glands. Fourteen methanol-fixed specimens were cryosectioned for immunohistochemistry and labelled with a panel of monoclonal antibodies against a wide range of collagens, glycosaminoglycans and proteoglycans. Labelling was detected with avidin-biotin-peroxidase. A further six specimens were formalin-fixed for routine histology. The tarsal plate immunolabelled strongly for types I, III and VI collagen and for aggrecan, versican, tenascin, cartilage oligomeric matrix protein (COMP) together with a variety of glycosaminoglycans (notably chondroitin 6 sulphate). A region of strong labelling for aggrecan, dermatan sulphate and chondroitin 6 sulphate immediately surrounded the Meibomian glands. The site of labelling corresponded to a layer of acellular and amorphous matrix seen histologically that we have termed the 'territorial matrix'. The results suggested that the tarsal plate is a specialized connective tissue that is neither purely fibrous nor cartilaginous, yet has an aggrecan content that probably contributes to its stiffness. Its unique character highlights the challenge in choosing an ideal mechanical substitute. As patients with rheumatoid arthritis often have problems relating to tear film deficiency, the ability of aggrecan or COMP to act as autoantigens may be significant. An immune reaction directed against these molecules could alter tarsal gland function by interfering with the interaction between the glands and their territorial matrix.

Human glands of Moll: histochemical and ultrastructural characterization of the glands of Moll in the human eyelid.

The function of the human gland of Moll of the eyelid is not exactly known. We studied the secretory and cytoskeletal components of these apocrine glands in males and females by immunohistochemical methods, and the ultrastructural organization of the glandular cells with an electron microscope. The glands of Moll are exclusively located at the margin of the eyelids and their ducts empty into the lash follicle. Immunohistochemical staining for actin and cytokeratins CK19 and CK7 points to the involvement of actin in the pinching-off mechanism of the apical cell protrusion during apocrine secretion and to a stabilizing role for the cytokeratins in this apical region of the glandular cells. The presence of the bacteriolytic enzyme lysozyme, the membrane-associated mucin 1, and the immunoglobulin A and its secretory component within the gland suggest a function in local immune defense. The presence of a variety of sugar components in the secretory product was verified by lectin histochemistry and periodic acid Schiff and Alcian blue stain. We suppose that these apocrine glands are active from birth in producing agents against pathogenic microorganisms in the eyelid shaft and on the ocular surface.

Air pollutants and tear film stability--a method for experimental evaluation.

Instability of the pre-ocular tear film causes symptoms of dry eyes. Tear film instability may be caused by exposure to air pollutants, but identification of causative agents is often difficult. We describe an in vitro technique for assessment of putative agents on the surface activity of Meibomian lipids. The lipids were obtained from bovine eyelids and dissolved in chloroform. Surface activity of the solution was assessed on a Wilhelmy balance. After addition of benzalkonium chloride, minimum surface tension of the lipids increased and maximum surface tension fell. After addition of quartz particles, both maximum and minimum surface tension increased. The method can be used to screen substances suspected to cause dry eyes, providing a basis for selection of substances for in vivo studies.

Systematic immunolocalization of retinoid receptors in developing and adult mouse eyes.

PURPOSE: To determine the localization of retinoic acid receptors (RAR) alpha, beta, and gamma and retinoid X receptors (RXR) alpha, beta, and gamma in developing and adult mouse eyes at the level of single cells. METHODS: Immunohistochemistry was performed on paraformaldehyde-lysine-periodate-fixed cryosections of mouse eyes, from embryonic day 10.5 to adulthood, with polyclonal antibodies directed against each receptor isoform. Histologic sections from null mutant mice for each receptor served as negative controls. RESULTS: RARalpha was present ubiquitously in the prenatal eye and preferentially located in the posnatal retina and ciliary body. RARbeta was detected predominantly in the periocular mesenchyme and ciliary body. RARgamma was distributed in the periocular mesenchyme, choroid, sclera, cornea, conjunctiva, and lids. RXRalpha was found preferentially in the prenatal periocular mesenchyme and retina and in the postnatal ciliary body, cornea, and conjunctiva. RXRbeta was ubiquitous at all the stages. RXRgamma was detected mainly in subsets of prenatal retinal cells and in postnatal ganglion cells as well as a subset of photoreceptor cells that were characterized as cones in adults. CONCLUSIONS: RARalpha, beta, and gamma and RXRalpha and gamma exhibit specific and dynamic patterns of distribution in ocular tissues throughout the course of development. The abundance of RARbeta, RARgamma, and RXRalpha in the periocular mesenchyme suggests that this tissue represents an important site of retinoid actions during eye development and in adulthood.

Epidermal and dermal phospholipids of the human eyelid: a 31P nuclear magnetic resonance spectroscopy study.

The phospholipids of the skin are difficult to quantify because they represent only a small fraction of the skin tissue. In this study, 31P nuclear magnetic resonance, which permits precise profiling of these phospholipids, was used to compare the phospholipids of upper eyelid epidermal and dermal lipid extracts (n = 13 profiles). Phospholipid profiles included alkylacylphosphatidylcholine (AAPC), dihydrosphingomyelin (DHSM), diphosphatidylglycerol (cardiolipin), ethanolamine plasmalogen (EPLAS), lysophosphatidylcholine, phosphatidic acid, phosphatidylcholine (PC), phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, sphingomyelin, and uncharacterized phospholipids (U1 and U2, particularly enriched in the epidermis). The computed phospholipid metabolic index (n = 86 indexes) findings can be summarized as follows: a lower content of the en-ol and ether phospholipids in the epidermis relative to the dermis, internal compensation among the component phospholipids so as to maintain the choline functional group ratio, and a greater concentration of hydroxyl-containing functional groups in the epidermis. A membrane index (fmem) value of -0.37 for the epidermis deviated considerably from the value of -0.06 characteristic of living membranes and the dermis. The production of the reduced phosphatides, EPLAS and AAPC, indicates the use of alternative pathways between the two tissues. Relative to the dermis, increased PC in the epidermis coupled with decreased DHSM, EPLAS, and AAPC are factors enabling the epidermis of eyelid tissue to be an effective water barrier.