scopolamine-induced tissue damage assessment in dry eye rat models

Dysfonctionnement de la glande lacrymale induit par la scopolamine chez le rat

By 2021, approximately 12% of people are significantly affected by dry eyes1, making it one of the most common chronic eye diseases. Dry eye can be divided into two types: aqueous-deficient dry eye (ADDE) and evaporative dry eye (EDE)2, depending on the different factors that affect the disease. ADDE is further divided into Sj&#246;gren&#39;s syndrome (SS) and non-SS, but the majority of dry eye patients are non-SS patients in clinical3. Chronic dry eye symptoms seriously affect the visual quality of patients. Currently, the conventional treatment of DED involves the application of artificial tears to lubricate the ocular surface and physical therapy of the eyelids. However, dry eye syndrome may not offer a complete cure in many cases. Therefore, studying the pathogenesis of dry eye disease is crucial for the development of new therapies and drugs. Animal models of dry eye syndrome provide a foundation for further research.
There are many ways to construct animal models of dry eye syndrome4, including changing tear secretion levels by altering hormone levels. For example, removing the testes of rats can reduce androgen secretion, increase tear secretion, and decrease the concentration of free secretory component (SC) and IgA in tears5,6. Another method is to indicate autoimmune reactions in the lacrimal gland by removing the eye surface nerves that control the gland. Additionally, directly reducing tear secretion can be achieved by surgically removing the lacrimal gland7. Changing environmental conditions can also accelerate tear evaporation. For example, culturing animals in low humidity and dry ventilation conditions can establish a model of excessive evaporative dry eye8, which can be combined with other methods to increase the severity of dry eye. The main drugs used to induce dry eye experimental models are atropine and scopolamine9. As parasympathetic inhibitors, both can induce pharmacological blockade of cholinergic (muscarinic) receptors in the lacrimal gland and inhibit tear secretion. Compared with dry eyes caused by atropine muscle injection10, scopolamine has a stronger inhibitory effect on secretion glands, a longer duration of drug action, and weaker effects on cardiac, small intestinal, and bronchial smooth muscles. It is one of the most mature drugs for dry-eye animal models.
Different methods can be used to induce dry eye with scopolamine, such as subcutaneous injection, drug pump, or patch application4,11,12. In order to reduce the frequency of drug administration to experimental animals, many researchers apply transdermal patches to the tails of mice or use drug pumps. However, both of these methods have limitations. For example, the absorption of transdermal patches needs to take into account the individual absorption of mice, which can lead to inconsistent drug dosage. Although drug pumps can accurately control the dosage of each administration, they are not always compatible with the drug being delivered or the concentration being used. They also need to be placed surgically &#8211; which is more invasive to the animal, requiring an anesthetic event, and there is potential for post-surgical complications such as dehiscence. Subcutaneous injection, although more cumbersome, can ensure accurate dosage for each administration and maintain consistency in drug administration among different rats. At the same time, it has a lower cost and is suitable for conducting a large number of animal experiments.
This study applies repeated subcutaneous injection of scopolamine to establish a dry eye rat model. We analyze dry eye indicators such as corneal defects, tear secretion levels, and pathological morphology of the cornea, conjunctiva, and lacrimal gland. By combining drug concentration, pathological manifestations, and dry eye symptoms, we further elaborate on the dry eye rat model in detail, providing more accurate experimental data for the study of dry eye treatment and pathological mechanisms. We also describe the modeling process in detail for future researchers.

Pleins feux sur l’auteur : Les défis de la mise au point de modèles animaux sur la sécheresse oculaire et les orientations futures de la recherche

Un modèle de rat de sécheresse oculaire avec un dysfonctionnement de la glande lacrymale induit par la scopolamine

The process of developing a dry eye animal model is a long one. It requires continuous subcutaneous injection of scopolamine in the hind legs of rice to suppress the secretion of the lacrymal gland in rice. So, experimenters need to have enough patience to administer the medication regularly over a long period of time.Our protocol is a very useful method that can created different degrees of dry eye models based on different drug concentrations. It can make it easiest for the future researchers to study the treatment of dry eye disease. Our team will continue to explore the field of lacrimal gland regeneration, very excited to work on reconstructing 3D and conducting transplantation experiments.Our ultimate goal is to develop more advanced and efficient treatment options for individuals suffering from dry eye syndrome.

Évaluation des lésions tissulaires induites par la scopolamine dans des modèles de rats à œil sec

Pour commencer, maintenez le corps d’un rat stable et étirez sa patte arrière. Tamponnez le site d’injection avec de l’alcool. Insérez ensuite une seringue d’un millilitre, munie d’une aiguille de calibre 26 à la base du pli cutané entre le pouce et l’index.Tirez sur le piston de la seringue pour aspirer l’aiguille. Retirez et repositionnez l’aiguille si nécessaire. Injecter 0,5 millilitre de chlorure de sodium à 0,9 % avec ou sans bromhydrate de scopolamine en un seul mouvement régulier.Pour effectuer le test de sécrétion de larmes, coupez d’abord la moitié d’une bande de papier filtre le long de la ligne centrale. Coupez la tête de la bande pour la rendre lisse. Placez la bande de papier filtre sur le tiers externe du sac conjonctival de la paupière inférieure du rat.Après cinq minutes, utilisez une pince à épiler pour serrer la bande de papier filtre dans un micro tube à centrifuger. Placez une marque sur la paroi du tube pour enregistrer le volume de la déchirure. Pour colorer la cornée de l’œil du rat, déposez 0,5 microlitre de solution de fluorescéine sodique à 0,5 % dans le sac conjonctival inférieur de chaque œil.Après trois minutes, observez la cornée sous lumière bleue. Retirez la conjonctive bulbaire des yeux d’un rat euthanasié. Exciser la cornée du côté droit de chaque rat, et la fixer immédiatement dans du paraformaldéhyde à 4%.Découpez l’épiderme céphalique du tissu sous-cutané le long de la ligne reliant l’oreille et le coin externe de l’œil. Ensuite, élargissez l’incision des deux côtés et isolez la glande extra-orbitaire jaunâtre. Ensuite, retirez complètement la fourrure du rat et séparez la glande orbitaire supplémentaire avec une solution de chlorure de sodium à 0,9 %.La sécrétion lacrymale du groupe scopolamine a été considérablement réduite. La scopolamine n’a causé aucun défaut épithélial cornéen, comme en témoigne l’absence de coloration cornéenne. L’épithélium cornéen des groupes scopolamine était relativement plus mince que celui du groupe témoin.Le groupe 7,5 a également montré une connexion intracellulaire lâche et une structure vaculaire dans la couche basale. Les groupes témoins avaient des épithéliums cornéens significativement plus épais. La scopolamine semblait provoquer des changements inflammatoires dans les glandes lacrymales, indiquant une lésion fonctionnelle des glandes lacrymales.Une réduction de la substance mucineuse a été observée dans les groupes 2.5 et cinq, avec une infiltration de lymphocytes libres. De plus, le groupe 7.5 présentait une disposition irrégulière des cellules avec des cellules épithéliales de forme irrégulière. La scopolamine a également provoqué des changements morphologiques dans la conjonctive.

Research

JoVE Journal

Medicine

Scopolamine-Induced Tissue Damage Assessment in Dry Eye Rat Models

A Rat Dry Eye Model with Lacrimal Gland Dysfunction Induced by Scopolamine

Aqueous-deficient dry eye (ADDE) is a type of dry eye disease that can result in the reduction of tear secretion quantity and quality. Prolonged abnormal ...

Recherche

Médecine