RESUMO
Proper sight is not possible without a smooth, transparent cornea, which is highly exposed to environmental threats. The abundant corneal nerves are interspersed with epithelial cells in the anterior corneal surface and are instrumental to corneal integrity and immunoregulation. Conversely, corneal neuropathy is commonly observed in some immune-mediated corneal disorders but not in others, and its pathogenesis is poorly understood. Here we hypothesized that the type of adaptive immune response may influence the development of corneal neuropathy. To test this, we first immunized OT-II mice with different adjuvants that favor T helper (Th)1 or Th2 responses. Both Th1-skewed mice (measured by interferon-γ production) and Th2-skewed (measured by interleukin-4 production) developed comparable ocular surface inflammation and conjunctival CD4+ T cell recruitment but no appreciable corneal epithelial changes upon repeated local antigenic challenge. Th1-skewed mice showed decreased corneal mechanical sensitivity and altered corneal nerve morphology (signs of corneal neuropathy) upon antigenic challenge. However, Th2-skewed mice also developed milder corneal neuropathy immediately after immunization and independently of ocular challenge, suggestive of adjuvant-induced neurotoxicity. All these findings were confirmed in wild-type mice. To circumvent unwanted neurotoxicity, CD4+ T cells from immunized mice were adoptively transferred to T cell-deficient mice. In this setup, only Th1-transferred mice developed corneal neuropathy upon antigenic challenge. To further delineate the contribution of each profile, CD4+ T cells were polarized in vitro to either Th1, Th2, or Th17 cells and transferred to T cell-deficient mice. Upon local antigenic challenge, all groups had commensurate conjunctival CD4+ T cell recruitment and macroscopic ocular inflammation. However, none of the groups developed corneal epithelial changes and only Th1-transferred mice showed signs of corneal neuropathy. Altogether, the data show that corneal nerves, as opposed to corneal epithelial cells, are sensitive to immune-driven damage mediated by Th1 CD4+ T cells in the absence of other pathogenic factors. These findings have potential therapeutic implications for ocular surface disorders.
Assuntos
Células Th1 , Células Th2 , Camundongos , Animais , Adjuvantes Imunológicos , Córnea , Imunidade Adaptativa , InflamaçãoRESUMO
An asymptomatic 26-year-old woman underwent confocal microscopy as part of a control population for a research study. Images revealed reduced sub-basal corneal nerve density and multiple activated dendritic cells. Three years later, she presented with a self-limited cutaneous vasculitis in her lower extremities which prompted an evaluation for autoimmune diseases. Laboratory testing revealed positive antinuclear antibodies (1:320, thick granular pattern), and anti-SSA/SSB (SSA, 53.6 U/mL, moderately positive; SSB, 142.7 U/mL, strongly positive). Two weeks later, she presented with ocular pain and an ophthalmologic examination revealed ocular surface staining. An ocular ultrasound was consistent with posterior scleritis. Based on this picture, a diagnosis of Sjögren syndrome (SS) was made. SS is a chronic autoimmune disease that can present with symptoms that diminish the patient's quality of life. Confocal microscopy might be a valuable tool for the early diagnosis of disease.
Assuntos
Síndrome de Sjogren , Humanos , Feminino , Adulto , Síndrome de Sjogren/diagnóstico , Qualidade de Vida , Córnea , Microscopia Confocal , Anticorpos AntinuclearesRESUMO
Neurotrophic keratopathy (NK) is a degenerative corneal disease produced by different factors, including infection, trauma, and neurogenesis, that lead to trigeminal nerve damage and impaired corneal sensitivity. Extensive epithelial breakdown, impaired corneal epithelial healing and corneal ulceration, stromal melting, and perforation are main NK features. The proliferation of the corneal epithelium is endogenously regulated by a balance between adrenergic cAMP-dependent and cholinergic cGMP-dependent pathways. A careful balance of epitheliotropic neuromediators and neurotrophic factors expressed by corneal nerves and epithelial cells, respectively, is required to maintain corneal homeostasis. Even in its early stages, NK can cause reduced vision secondary to epithelial disturbance. Diagnosing NK is challenging, requiring the acquisition of a thorough clinical history and a comprehensive neurological and ophthalmic examination. Following suspicion of a clinical NK diagnosis, corneal sensitivity must be assessed qualitatively with the wisp of the cotton-tipped applicator and quantitatively through Cochet-Bonnet esthesiometry (CBE). A myriad of therapies is used for NK, and new, more specific modalities are being developed and investigated. Medical treatment with topical recombinant human nerve growth factor and surgical treatment through corneal neurotization are promising therapies aiming to target NK pathophysiology. Coexistent ocular surface disorders must be managed concomitantly to improve its prognosis. This review describes the up-to-date knowledge of the molecular basis regarding the pathogenesis of NK, and the novel target-specific therapeutic approaches based on this molecular mechanism.
Assuntos
Doenças da Córnea , Distrofias Hereditárias da Córnea , Epitélio Corneano , Ceratite , Doenças do Nervo Trigêmeo , Córnea , Doenças da Córnea/diagnóstico , Doenças da Córnea/terapia , HumanosRESUMO
In vivo confocal microscopy (IVCM) is becoming an indispensable tool for studying corneal physiology and disease. Enabling the dissection of corneal architecture at a cellular level, this technique offers fast and noninvasive in vivo imaging of the cornea with images comparable to those of ex vivo histochemical techniques. Corneal nerves bear substantial relevance to clinicians and scientists alike, given their pivotal roles in regulation of corneal sensation, maintenance of epithelial integrity, as well as proliferation and promotion of wound healing. Thus, IVCM offers a unique method to study corneal nerve alterations in a myriad of conditions, such as ocular and systemic diseases and following corneal surgery, without altering the tissue microenvironment. Of particular interest has been the correlation of corneal subbasal nerves to their function, which has been studied in normal eyes, contact lens wearers, and patients with keratoconus, infectious keratitis, corneal dystrophies, and neurotrophic keratopathy. Longitudinal studies have applied IVCM to investigate the effects of corneal surgery on nerves, demonstrating their regenerative capacity. IVCM is increasingly important in the diagnosis and management of systemic conditions such as peripheral diabetic neuropathy and, more recently, in ocular diseases. In this review, we outline the principles and applications of IVCM in the study of corneal nerves in various ocular and systemic diseases.