Comparison of the effects of corneal and lacrimal gland denervation on the lacrimal functional unit of rats / Comparação dos efeitos da denervação da córnea e da glândula lacrimal na unidade funcional lacrimal de ratos

ABSTRACT Purpose: This study aimed to compare the changes in the lacrimal functional unit in the following two models of neurogenic dry eye syndrome: sensory denervation of the cornea versus autonomic denervation of the lacrimal gland. Methods: The neural network supports the lacrimal functional unit. It can be divided into afferent (sensory) and efferent (autonomic) pathways and is affected by severe diseases that compromise the lacrimal functional unit. Male Wistar, 8-week-old rats were divided into the following three groups: 1) control naïve (n=16 animals); 2) autonomic denervation: where rats were subjected to right lacrimal gland nerve ablation and evaluated after 1 and 2 months (1M and 2M) after the procedure (n=7 animals per subgroup, autonomic denervation 1M and autonomic denervation 2M, respectively); 3) sensory denervation induced by 0.2% benzalkonium chloride eye drops, twice a day for 7 days in the right eye (n=10 animals). The corneal sensitivity was measured using the eye wipe test with capsaicin (10 µM). The quantitative real-time PCR was performed to compare the mRNA expressions of proinflammatory cytokines, such as Il-1β, Il-6, Tnf, Mmp9, in the cornea, trigeminal ganglion, and lacrimal gland. In addition, the mRNA of the promitotic factors in the lacrimal gland, such as Bmp7, Runx1, Runx3, Fgf10, and Smad1, was compared. Results: Sensory denervation induced corneal hyperalgesia (p=0.001). Sensory denervation and autonomic denervation increased the mRNA of proinflammatory cytokines in the cornea and lacrimal gland (p<0.05), but only sensory denervation increased the mRNA levels of Il-1β and Tnf in the trigeminal ganglion (p<0.05) compared with the control naïve. Conclusions: Autonomic denervation and sensory denervation models can have common features, such as inflammation of different parts of the lacrimal functional unit. However, hyperesthesia and inflammatory markers in the trigeminal ganglion because of sensory denervation and the expression of regenerative mediators in the lacrimal gland owing to autonomic denervation are the distinguishing features of these diseases that can be explored in future studies assessing dry eye syndrome secondary to neural damage of the lacrimal functional unit.

RESUMO Objetivo: O nosso objetivo neste estudo foi comparar as alterações na unidade funcional lacrimal em dois modelos de síndrome do olho seco neurogênica: desnervação sensorial da córnea versus desnervação autonômica da glândula lacrimal. Métodos: A rede neural é um importante suporte para a unidade funcional lacrimal. Pode ser dividido em vias aferentes (sensoriais) e eferentes (autonômicas), sujeitas a doenças graves que comprometem a unidade funcional lacrimal. Ratos Wistar machos, com 8 semanas de idade, foram divididos em três grupos: 1) Controle naïve (n=16 animais); 2) Desnervação autonômica: onde os ratos foram submetidos à ablação do nervo da glândula lacrimal direita e avaliados após um e dois meses (1 M a 2 M) do procedimento (n=7 animais por subgrupo, desnervação autonômica 1M e desnervação autonômica 2M, respectivamente); 3) Desnervação sensorial induzida por colírio a 0,2% de cloreto de benzalcônio, duas vezes ao dia por 7 dias no olho direito (n=10 animais). A sensibilidade da córnea foi medida pelo teste de movimento pata-olho com capsaicina (10 µM). A PCR quantitativa em tempo real foi aplicada para comparar a expressão relativa de mRNA de citocinas pró-inflamatórias: Il1b, Il6, Tnf, Mmp9, na córnea, gânglio trigêmio e glândula lacrimal. O mRNA dos agentes pró-mitóticos Bmp7, Runx1, Runx3, Fgf10 e Smad1 foram comparados na glândula lacrimal. Resultados: A desnervação sensorial induziu hiperalgesia da córnea (p=0,001). Desnervação sensorial e desnervação autonômica aumentaram o mRNA de citocinas pró-inflamatórias no córnea e glândula lacrimal (p<0,05), mas apenas desnervação sensorial aumentou o mRNA de Il1b e Tnf no gânglio trigêmio (p<0,05) quando comparado ao controle naïve. Conclusões: Os modelos de desnervação autonômica e desnervação sensorial podem ter características comuns, como inflamação de diferentes partes da unidade funcional lacrimal. No entanto, a hiperestesia e os marcadores inflamatórios no gânglio trigêmio de desnervação sensorial e a expressão de mediadores regenerativos na glândula lacrimal na desnervação autonômica são características que distinguem essas doenças, podendo ser investigadas em estudos futuros que abordam o olho seco secundário ao dano neural da unidade funcional lacrimal.

Dry eye - a review.

Of the myriad reasons for visits to an ophthalmologist, one of the most common maladies afflicting patients is Dry Eye Disease (DED), which can cause mild discomfort in the early stages and endstage ocular surface damage in its more severe forms. Dry eye is a problem of utmost importance, more in the developed rather than developing nations. Various aspects of the manifestation, including the tear osmolarity, ocular surface homeostasis and the role of ocular surface epithelial stem cells in maintaining the ocular surface homeostasis have been discussed. The objective tests to assess and grade dry eye have been noted. A systematic approach to the affected eye and the patient has also been outlined. The major categories of medications used along with the methods of delivery are specified in this review. A systematic approach in understanding the type and grade of Dry Eye Disease is mandatory for good clinical response. Along with clinical management the doctor should also stress on environmental changes that exaggerates dryness.

Current Trends in the Recognition and Treatment of Dry Eye: A Survey of Ophthalmologists

PURPOSE: Based on the questionnaires for dry eyes in 2006, we have investigated the current status and new trends in the recognition and management of the dry eye. METHODS: We ask the 15 questionnaires to 197 ophthalmologists. After reorganizing the data based on each questions, we compared the result with the most current studies in Korea and other countries as well. Then, we report the current trends in the diagnosis and treatment of dry eye. RESULTS: Dry eye patients account for take up about 20-30% of total outpatients and it is currently accepted etiology that dry eye inflammation is related to the function of the immune system. Patient's symptoms and slit lamp examination are important for diagnosis. An anti-inflammatory therapy is needed for patients with moderate to severe dry eye. CONCLUSIONS: Increasingly, there are positive attitudes toward accepting that persistent dry eye is an inflammatory disease; therefore, there are increases in use of an anti-inflammatory agent for treatment.

Current Concepts and Therapeutic Management of Dry Eye

The majority of dry eye symptoms are due to a chronic inflammation of the lacrimal functional unit resulting in a loss of tear film integrity and normal function. The tear secretion is controlled by the lacrimal functional unit consisting of the ocular surface (cornea, conjunctiva, and meibomian glands), the main lacrimal gland, and the interconnecting innervation. A lack of systemic androgen support to the lacrimal gland has been shown to be a facilitating factor in the initiation of ocular inflammation. If any portion of this functional unit is compromised, lacrimal gland support to the ocular surface is impeded. In this review, the classification and treatment of dry eye syndrome will be presented according to the A Delphi approach.