Efficacy and Safety of Plasma Rich in Growth Factor in Patients with Congenital Aniridia and Dry Eye Disease.

Congenital aniridia is a rare bilateral ocular malformation characterized by the partial or complete absence of the iris and is frequently associated with various anomalies, including keratopathy, cataract, glaucoma, and foveal and optic nerve hypoplasia. Additionally, nearly 50% of individuals with congenital aniridia experience symptoms of ocular dryness. Traditional treatment encompasses artificial tears and autologous serum. This study aimed to assess the effectiveness and safety of using platelet rich in growth factors (PRGF) plasma in patients with congenital aniridia and ocular dryness symptoms. METHODS: The included patients underwent two cycles of a 3-month PRGF treatment. At 6 months, symptomatology was evaluated using the OSDI and SANDE questionnaires, and ocular surface parameters were analyzed. RESULTS: The OSDI and SANDE values for frequency and severity demonstrated statistically significant improvements (p < 0.05). Ocular redness, corneal damage (corneal staining), and tear volume (Schirmer test) also exhibited statistically significant improvements (p < 0.05). No significant changes were observed in visual acuity or in the grade of meibomian gland loss. CONCLUSION: The use of PRGF in patients with congenital aniridia and ocular dryness symptoms led to significant improvements in symptomatology, ocular redness, and ocular damage. No adverse effects were observed during the use of PRGF.

Immunocytochemical Analysis of Crocin against Oxidative Stress in Trigeminal Sensory Neurons Innervating the Cornea.

Corneal diseases are a major cause of vision loss, often associated with aging, trauma and disease. Damage to corneal sensory innervation leads to discomfort and pain. Environmental stressors, such as short-wavelength light, can induce oxidative stress that alters mitochondrial function and affects cell and tissue homeostasis, including corneal innervation. Cellular antioxidant mechanisms may attenuate oxidative stress. This study investigates crocin, a derivative of saffron, as a potential antioxidant therapy. In vitro rat trigeminal sensory ganglion neurons were exposed to both sodium azide and blue light overexposure as a model of oxidative damage. Crocin was used as a neuroprotective agent. Mitochondrial and cytoskeletal markers were studied by immunofluorescence analysis to determine oxidative damage and neuroprotection. In vivo corneal innervation degeneration was evaluated in cornea whole mount preparations using Sholl analyses. Blue light exposure induces oxidative stress that affects trigeminal neuron mitochondria and alters sensory axon dynamics in vitro, and it also affects corneal sensory innervation in an in vivo model. Our results show that crocin was effective in preserving mitochondrial function and protecting corneal sensory neurons from oxidative stress. Crocin appears to be a promising candidate for the neuroprotection of corneal innervation.

Altered Clock Gene Expression in Female APP/PS1 Mice and Aquaporin-Dependent Amyloid Accumulation in the Retina.

Alzheimer's disease (AD), the most prevalent form of dementia, is a neurodegenerative disorder characterized by different pathological symptomatology, including disrupted circadian rhythm. The regulation of circadian rhythm depends on the light information that is projected from the retina to the suprachiasmatic nucleus in the hypothalamus. Studies of AD patients and AD transgenic mice have revealed AD retinal pathology, including amyloid-ß (Aß) accumulation that can directly interfere with the regulation of the circadian cycle. Although the cause of AD pathology is poorly understood, one of the main risk factors for AD is female gender. Here, we found that female APP/PS1 mice at 6- and 12-months old display severe circadian rhythm disturbances and retinal pathological hallmarks, including Aß deposits in retinal layers. Since brain Aß transport is facilitated by aquaporin (AQP)4, the expression of AQPs were also explored in APP/PS1 retina to investigate a potential correlation between retinal Aß deposits and AQPs expression. Important reductions in AQP1, AQP4, and AQP5 were detected in the retinal tissue of these transgenic mice, mainly at 6-months of age. Taken together, our findings suggest that abnormal transport of Aß, mediated by impaired AQPs expression, contributes to the retinal degeneration in the early stages of AD.

Impact of Plasma Rich in Growth Factors (PRGF) Eye Drops on Ocular Redness and Symptomatology in Patients with Dry Eye Disease.

Background and Objectives: Dry eye disease (DED) is a common and very symptomatic pathology that affects normal daily activity. The aim of the study was to evaluate the efficacy of plasma rich in growth factors (PRGF) added to one routine treatment protocol for DED (artificial tears substitutes, lid hygiene, and anti-inflammatory therapy). Materials and Methods: Patients were divided into two groups of treatment: standard treatment group (n = 43 eyes) and PRGF group (n = 59). Patients' symptomatology (inferred from OSDI and SANDE questionnaires), ocular inflammation, tear stability, and ocular surface damage were analyzed at baseline and after 3 months of treatment. Results: OSDI test scores were significantly lower in both groups (p < 0.001). SANDE frequency test scores also improved statistically, with differences between groups (p = 0.0089 SANDE frequency and p < 0.0119 SANDE severity). There was a greater reduction in ocular redness (ocular inflammation) in the PRGF group (p < 0.0001) and fluorescein tear break-up time was significantly improved in the PRGF group (p = 0.0006). No significant changes were found in terms of ocular surface damage. No adverse events were obtained in either group. Conclusions: The addition of PRGF to the standard treatment of DED, according to the results obtained, proved to be safe and produced an improvement in ocular symptomatology and signs of inflammation, particularly in moderate and severe cases, when compared to standard treatment.

Disturbed circadian rhythm and retinal degeneration in a mouse model of Alzheimer's disease.

The circadian clock is synchronized to the 24 h day by environmental light which is transmitted from the retina to the suprachiasmatic nucleus (SCN) primarily via the retinohypothalamic tract (RHT). Circadian rhythm abnormalities have been reported in neurodegenerative disorders such as Alzheimer's disease (AD). Whether these AD-related changes are a result of the altered clock gene expression, retina degeneration, including the dysfunction in RHT transmission, loss of retinal ganglion cells and its electrophysiological capabilities, or a combination of all of these pathological mechanisms, is not known. Here, we evaluated transgenic APP/PS1 mouse model of AD and wild-type mice at 6- and 12-month-old, as early and late pathological stage, respectively. We noticed the alteration of circadian clock gene expression not only in the hypothalamus but also in two extra-hypothalamic brain regions, cerebral cortex and hippocampus, in APP/PS1 mice. These alterations were observed in 6-month-old transgenic mice and were exacerbated at 12 months of age. This could be explained by the reduced RHT projections in the SCN of APP/PS1 mice, correlating with downregulation of hypothalamic GABAergic response in APP/PS1 mice in advanced stage of pathology. Importantly, we also report retinal degeneration in APP/PS1 mice, including Aß deposits and reduced choline acetyltransferase levels, loss of melanopsin retinal ganglion cells and functional integrity mainly of inner retina layers. Our findings support the theory that retinal degeneration constitutes an early pathological event that directly affects the control of circadian rhythm in AD.

Recovery of Corneal Innervation after Treatment in Dry Eye Disease: A Confocal Microscopy Study.

PURPOSE: To analyze the changes in corneal innervation by means of in vivo corneal confocal microscopy (IVCM) in patients diagnosed with Evaporative (EDE) and Aqueous Deficient Dry Eye (ADDE) and treated with a standard treatment for Dry Eye Disease (DED) in combination with Plasma Rich in Growth Factors (PRGF). METHODS: Eighty-three patients diagnosed with DED were enrolled in this study and included in the EDE or ADDE subtype. The primary variables analyzed were the length, density and number of nerve branches, and the secondary variables were those related to the quantity and stability of the tear film and the subjective response of the patients measured with psychometric questionnaires. RESULTS: The combined treatment therapy with PRGF outperforms the standard treatment therapy in terms of subbasal nerve plexus regeneration, significantly increasing length, number of branches and nerve density, as well as significantly improving the stability of the tear film (p < 0.05 for all of them), and the most significant changes were located in the ADDE subtype. CONCLUSIONS: the corneal reinnervation process responds in a different way depending on the treatment prescribed and the subtype of dry eye disease. In vivo confocal microscopy is presented as a powerful technique in the diagnosis and management of neurosensory abnormalities in DED.

Improved Tool for Predicting Skin Irritation on Reconstructed Human Epidermis Models Based on Electrochemical Impedance Spectroscopy.

The rabbit skin irritation test has been the standard for evaluating the irritation potential of chemicals; however, alternative methods that do not use animal testing are actively encouraged. Reconstructed human epidermis (RhE) models mimic the biochemical and physiological properties of the human epidermis and can be used as an alternative method. On RhE methods, the metabolic activity of RhE models is used to predict skin irritation, with a reduction in metabolic activity indicating a reduced number of viable cells and linking cell death to skin irritation processes. However, new challenges have emerged as the use of RhE models increases, including the need for non-invasive and marker-free methodologies to assess cellular states. Electrochemical impedance spectroscopy (EIS) is one such methodology that can meet these requirements. In this study, our results showed that EIS can differentiate between irritant and non-irritant chemicals, with a significant increase in the capacitance values observed in the irritant samples. A ROC curve analysis showed that the prediction method based on EIS met OECD TG 439 requirements at all time points and had 95% within-laboratory reproducibility. Comparison with the MTT viability assay showed that prediction using EIS achieved higher sensitivity, specificity, and accuracy. These results suggest that EIS could potentially replace animal testing in the evaluation of irritation potential and could be a valuable addition to in vitro testing strategies.

Synthetic Heparan Sulfate Mimetic Polymer Enhances Corneal Nerve Regeneration and Wound Healing after Experimental Laser Ablation Injury in Mice.

(1) Background: Abnormal corneal wound healing compromises visual acuity and can lead to neuropathic pain. Conventional treatments usually fail to restore the injured corneal tissue. In this study, we evaluated the effectiveness of a synthetic heparan sulfate mimetic polymer (HSmP) in a mouse model of corneal wound healing. (2) Methods: A surgical laser ablation affecting the central cornea and subbasal nerve plexus of mice was used as a model of the wound-healing assay. Topical treatment with HSmP was contrasted to its vehicle and a negative control (BSS). Corneal repair was studied using immunofluorescence to cell proliferation (Ki67), apoptosis (TUNEL assay), myofibroblast transformation (αSMA), assembly of epithelial cells (E-cadherin) and nerve regeneration (ß-tubulin III). (3) Results: At the end of the treatment, normal epithelial cytoarchitecture and corneal thickness were achieved in HSmP-treated animals. HSmP treatment reduced myofibroblast occurrence compared to eyes irrigated with vehicle (p < 0.01) or BSS (p < 0.001). The HSmP group showed 50% more intraepithelial nerves than the BSS or vehicle groups. Only HSmP-treated corneas improved the visual quality to near transparent. (4) Conclusions: These results suggest that HSmP facilitates the regeneration of the corneal epithelium and innervation, as well as restoring transparency and reducing myofibroblast scarring after laser experimental injury.

Exosomes Released by Corneal Stromal Cells Show Molecular Alterations in Keratoconus Patients and Induce Different Cellular Behavior.

Exosomes have been related to various disorders, but their study in relation to ocular pathologies has been limited. In this article, we analyze exosomes produced by corneal stromal cells from healthy individuals and from patients with keratoconus. The proteomic study allowed for the identification of 14 new proteins with altered expression, related to molecules previously associated with the pathology. miRNA analysis detected 16 altered species, including miR-184, responsible for familial severe keratoconus. The prediction of its potential biological targets identified 1121 genes, including some related to this pathology. Exosomes produced by keratoconic cells induced a marked increase in the migration of stromal cells and corneal epithelium, while those produced by healthy cells had no effect on stromal cells. Both types of nanovesicles reduced the proliferation of stromal and corneal cells, but those produced by healthy cells had less effect. Exosomes produced by healthy cells had concentration-dependent effects on the transcription of genes encoding proteoglycans by keratoconus cells, with a relative normalization observed at concentrations of 240 µg/mL. These results show the alteration of stromal exosomes in keratoconus and suggest an influence on the development of the pathology, although the use of healthy exosomes could also have therapeutic potential.

Polymerizable Skin Hydrogel for Full Thickness Wound Healing.

The skin is the largest organ in the human body, comprising the main barrier against the environment. When the skin loses its integrity, it is critical to replace it to prevent water loss and the proliferation of opportunistic infections. For more than 40 years, tissue-engineered skin grafts have been based on the in vitro culture of keratinocytes over different scaffolds, requiring between 3 to 4 weeks of tissue culture before being used clinically. In this study, we describe the development of a polymerizable skin hydrogel consisting of keratinocytes and fibroblast entrapped within a fibrin scaffold. We histologically characterized the construct and evaluated its use on an in vivo wound healing model of skin damage. Our results indicate that the proposed methodology can be used to effectively regenerate skin wounds, avoiding the secondary in vitro culture steps and thus, shortening the time needed until transplantation in comparison with other bilayer skin models. This is achievable due to the instant polymerization of the keratinocytes and fibroblast combination that allows a direct application on the wound. We suggest that the polymerizable skin hydrogel is an inexpensive, easy and rapid treatment that could be transferred into clinical practice in order to improve the treatment of skin wounds.

In-house performance assessment of 3D QobuR-Reconstructed Human Cornea-Like Epithelium (RhCE) for the evaluation of eye hazard.

To replace the Draize eye irritation test (OECD Test Guideline 404), several test methods based on reconstructed cornea-like epithelium (RhCE) have been developed and adopted in the OECD TG 492. The objective of this study was to stablish the experimental procedures and evaluate the performance assessment of QobuR-RhCE, an in-house RhCE model to be used for the evaluation of eye hazard. We define the essential structural, functional and procedural elements of the test method components to help assuring that the proposed test method is based on the same concepts as the validated reference methods. Performance assessment was evaluated in accordance with the revised performance standards for the assessment of proposed similar or modified in vitro reconstructed human cornea-like epithelium and the minimum list of reference chemicals was evaluated. As result, the proposed method scored 93.3% sensibility, 60% specificity, 76.7% accuracy and 96.7% within-laboratory reproducibility (WLR), providing a similar performance in comparison to the validated reference methods. Additionally, we describe a secondary endpoint based on Transepithelial Electrical Resistance (TEER) that could be of use to better discriminate between irritants and non-irritants. Taken together the results indicate that the QobuR-RhCE test method is an accurate screening tool that can be used as a standalone alternative to evaluate ocular irritation.

Cell Surface Glycosaminoglycans as Receptors for Adhesion of Candida spp. to Corneal Cells.

The most common causal agents of fungal keratitis are yeasts of the Candida genus. Adhesion constitutes the first stage of pathogenesis. Previous studies have shown that glycosaminoglycans from the corneal cell surface play an essential role in bacterial keratitis, although little is known about their role in fungal infections. The objective of this work is to analyze the role that glycosaminoglycans (GAGs) play in the adhesion of fungi of the Candida genus to corneal epithelial cells. The participation of GAGs in the adhesion of fungi was studied through the specific inhibition of the synthesis of these molecules by enzymatic digestion using specific lyases and the silencing of various genes involved in heparan sulfate sulfation. The results seem to indicate that glycosaminoglycans act to some extent as receptors for this fungus, although there are differences between fungal species. Treatment with inhibitors partially reduced the adherence of fungal species. Digestion of cell surface heparan sulfate further reduced the adherence of Candida albicans and Candida glabrata compared to chondroitin sulfate, indicating that the binding is preferentially mediated by heparan sulfate. Degradation of both heparan sulfate and chondroitin sulfate produced similar effects on the adherence of Candida parapsilosis. However, adhesion of C. albicans hyphae is not dependent on GAGs, suggesting the expression of other adhesins and the recognition of other receptors present in corneal cells. Our results open the door to new strategies for stopping the adhesion of pathogenic fungi, and their subsequent invasion of the cornea; thus, reducing the probability of the keratitis development.

Human Stem Cell Transplantation for Retinal Degenerative Diseases: Where Are We Now?

Background and Objectives: Irreversible visual impairment is mainly caused by retinal degenerative diseases such as age-related macular degeneration and retinitis pigmentosa. Stem cell research has experienced rapid progress in recent years, and researchers and clinical ophthalmologists are trying to implement this promising technology to treat retinal degeneration. The objective of this systematic review is to analyze currently available data from clinical trials applying stem cells to treat human retinal diseases. Materials and Methods: We performed a systematic literature search in PubMed to identify articles related with stem cell therapies to retinal diseases published prior to September 2021. Furthermore, a systematic search in ClinicalTrials (NIH U.S. National Library of Medicine) was performed to identify clinical trials using stem cells to treat retinal diseases. A descriptive analysis of status, conditions, phases, interventions, and outcomes is presented here. Conclusions: To date, no available therapy based on stem cell transplantation is approved for use with patients. However, numerous clinical trials are currently finishing their initial phases and, in general, the outcomes related to implantation techniques and their long-term safety seem promising. In the next few years, we expect to see quantifiable results pertaining to visual function improvement.

Small fiber neuropathy in the cornea of Covid-19 patients associated with the generation of ocular surface disease.

PURPOSE: To describe the association between Sars-CoV-2 infection and small fiber neuropathy in the cornea identified by in vivo corneal confocal microscopy. METHODS: Twenty-three patients who had overcome COVID-19 were recruited to this observational retrospective study. Forty-six uninfected volunteers were also recruited and studied as a control group. All subjects were examined under in vivo confocal microscopy to obtain images of corneal subbasal nerve fibers in order to study the presence of neuroma-like structures, axonal beadings and dendritic cells. The Ocular Surface Disease Index (OSDI) questionnaire and Schirmer tear test were used as indicators of Dry Eye Disease (DED) and ocular surface pathology. RESULTS: Twenty-one patients (91.31%) presented alterations of the corneal subbasal plexus and corneal tissue consistent with small fiber neuropathy. Images from healthy subjects did not indicate significant nerve fiber or corneal tissue damage. Eight patients reported increased sensations of ocular dryness after COVID-19 infection and had positive DED indicators. Beaded axons were found in 82.60% of cases, mainly in patients reporting ocular irritation symptoms. Neuroma-like images were found in 65.22% patients, more frequently in those with OSDI scores >13. Dendritic cells were found in 69.56% of patients and were more frequent in younger asymptomatic patients. The presence of morphological alterations in patients up to 10 months after recovering from Sars-CoV-2 infection points to the chronic nature of the neuropathy. CONCLUSIONS: Sars-CoV-2 infection may be inducing small fiber neuropathy in the ocular surface, sharing symptomatology and morphological landmarks with DED and diabetic neuropathy.

Alterations in the Expression of the Genes Responsible for the Synthesis of Heparan Sulfate in Brains With Alzheimer Disease.

The saccharide chains of heparan sulfate appear to be involved in several aspects Alzheimer disease (AD) pathogenesis. Their structural complexity is due to the expression of different isoenzymes. We studied the differential transcription of heparan sulfate chain biosynthesis in AD brains, analyzing different brain regions in patients with different extents of AD pathology. The transcriptomic study was performed by RT-PCR using samples of amygdala, anterior hippocampus, posterior hippocampus, claustrum, calcarine fissure, globus pallidus and cerebellum from patients with mild, moderate, or severe AD, as well as healthy individuals. Certain heparan sulfate epitopes were also detected by immunohistochemistry. Several genes, across all stages of heparan sulfate synthesis, showed altered transcription in different brain regions of AD patients. The numbers of alterations were greater in in moderate versus mild AD patients. In severe patients, there were fewer alterations in genes related to early stages of biosynthesis, and overexpression of genes involved in late stages. The alterations correlated with progressive brain atrophy, although alterations were more common in the cerebellum. Detection of some heparan sulfate epitopes by immunohistochemistry was consistent with previous studies. In conclusion, transcriptional alterations in the biosynthetic genes of heparan sulfate depend on the brain region and the degree of AD pathology.

Development and Optimization of Freeze-Dried Eye Drops Derived From Plasma Rich in Growth Factors Technology.

Purpose: To investigate whether plasma rich in growth factors (PRGF) eye drops maintain their biological potential after a freeze drying process. The addition of a lyoprotectant like trehalose was also evaluated. Methods: Blood from three healthy donors was collected to obtain eye drops by PRGF technology. The resultant eye drops were divided in four groups: PRGF, freeze-dried PRGF (PRGF lyo), and PRGF lyophilized mixed with 2,5% trehalose (PRGF lyo+2.5T) or 5% trehalose (PRGF lyof+5T). Chemical and biological characteristics were evaluated. Photorefractive keratectomy was performed on C57BL/6 mice which were divided in three treatment groups: control, PRGF, and PRGF lyo. Corneal wound healing and haze formation were evaluated macroscopically. Eyes were collected at 1, 2, 3, and 7 days after surgery, and were processed for histologic studies. Results: The pH values of PRGF samples increased significantly after the lyophilization process. Osmolarity levels increased significantly in PRGF samples mixed with trehalose in comparison with PRGF samples without protectants. The freeze drying process maintained growth factors levels as well as the biological properties of PRGF eye drops even without the use of lyoprotectants. PRGF lyo treatment significantly decreased the re-epithelialization time and haze formation in photorefractive keratectomy-treated corneas regarding PRGF and control groups. Furthermore, the PRGF lyo group significantly decreased the number of smooth muscle actin-positive cells in comparison with the control group at each time of the study and at days 2 and 3 in the PRGF group. Conclusions: The freeze drying process preserves the protein and growth factor content as well as the biological properties of PRGF eye drops, even without the use of protectants. Freeze-dried PRGF eye drops accelerate corneal tissue regeneration after photorefractive keratectomy in comparison with the control group. Translational Relevance: Our study shows the feasibility to preserve the biological capability of PRGF eye drops as freeze-dried formulation, avoiding the addition of protectants.

Los cambios estructurales de la retina, ¿nuevos biomarcadores de los trastornos mentales? Una revisión sistemática y síntesis temática de la literatura / Could structural changes in the retinal layers be a new biomarker of mental disorders? A systematic review and thematic synthesis

Recientemente se ha planteado que las alteraciones de las capas de la retina podrían ser un biomarcador de determinados trastornos mentales, al derivar esta de la misma capa embrionaria que el cerebro y estar conectada con este a través del nervio óptico. El objeto del presente artículo es ofrecer una revisión sistemática de la literatura y una síntesis temática sobre el estado actual de las alteraciones de las capas de la retina identificadas mediante tomografía de coherencia óptica en los pacientes con esquizofrenia, trastorno bipolar y depresión mayor. Para ello se realizó una búsqueda sistemática de la literatura, la lectura crítica de los artículos seleccionados y la síntesis temática de los resultados. Los pacientes con esquizofrenia son los que presentan más alteraciones, seguidos de los pacientes con trastorno bipolar, siendo muy escasos los hallazgos en la depresión. La capa de fibras nerviosas de la retina es la capa retiniana con más alteraciones en la esquizofrenia y en el trastorno bipolar, mientras que ningún estudio en depresión mayor encontró alteraciones en ella. De los parámetros clínicos, la duración de la enfermedad correlaciona significativa e inversamente con el grosor de las distintas capas en todos los trastornos. A la hora de interpretar estos datos es necesario tener en cuenta las limitaciones y diferencias de los estudios, especialmente el tiempo medio de evolución de los trastornos. Dado que este era muy diferente entre los 3 trastornos (más del doble en el caso de la esquizofrenia respecto a la depresión mayor), las diferencias en los resultados encontrados podrían deberse más al efecto del tiempo de evolución que al trastorno en sí. En conclusión, los hallazgos de la tomografía de coherencia óptica son esperanzadores, ya que podrían proporcionar biomarcadores de la neurodegeneración y/o neuroprogresión tanto de la esquizofrenia como del trastorno bipolar

It has recently been suggested that alterations of the layers of the retina could be a biomarker of specific mental disorders since they originate in the same embryonic layer as the brain and both are interconnected through the optic nerve. The purpose of this article is to offer a systematic review of the literature and a thematic synthesis on the current state of the alterations of the retina layers identified by optical coherence tomography in patients with schizophrenia, bipolar disorder and major depression. For this purpose, we performed a bibliographic search, a systematic review of the studies and a thematic synthesis of the reported findings. Patients with schizophrenia have more abnormal findings followed by patients with bipolar disorder, with very few findings in depression. The nerve fiber layer is the retinal layer with more abnormal findings both in schizophrenia and in bipolar disorder, while no study in major depression found alterations in it. Of the clinical parameters, the duration of the illness correlates significantly and inversely with the thickness of the different layers in all disorders. When interpreting these data, it is necessary to take into account the limitations and differences of the studies, especially the mean length of the disorders. Given that this was very different among the 3 disorders (more than doubled in the case of schizophrenia respect to major depression), the differences in the results found could be due more to the effect of the length of illness than to the disorder itself. In summary, optical coherence tomography findings are promising, since they could provide biomarkers of neurodegeneration and/or neuroprogression of both schizophrenia and bipolar disorder

Could structural changes in the retinal layers be a new biomarker of mental disorders? A systematic review and thematic synthesis. / Los cambios estructurales de la retina, ¿nuevos biomarcadores de los trastornos mentales? Una revisión sistemática y síntesis temática de la literatura.

It has recently been suggested that alterations of the layers of the retina could be a biomarker of specific mental disorders since they originate in the same embryonic layer as the brain and both are interconnected through the optic nerve. The purpose of this article is to offer a systematic review of the literature and a thematic synthesis on the current state of the alterations of the retina layers identified by optical coherence tomography in patients with schizophrenia, bipolar disorder and major depression. For this purpose, we performed a bibliographic search, a systematic review of the studies and a thematic synthesis of the reported findings. Patients with schizophrenia have more abnormal findings followed by patients with bipolar disorder, with very few findings in depression. The nerve fiber layer is the retinal layer with more abnormal findings both in schizophrenia and in bipolar disorder, while no study in major depression found alterations in it. Of the clinical parameters, the duration of the illness correlates significantly and inversely with the thickness of the different layers in all disorders. When interpreting these data, it is necessary to take into account the limitations and differences of the studies, especially the mean length of the disorders. Given that this was very different among the 3 disorders (more than doubled in the case of schizophrenia respect to major depression), the differences in the results found could be due more to the effect of the length of illness than to the disorder itself. In summary, optical coherence tomography findings are promising, since they could provide biomarkers of neurodegeneration and/or neuroprogression of both schizophrenia and bipolar disorder.

Functional and Morphologic Alterations in Mechanical, Polymodal, and Cold Sensory Nerve Fibers of the Cornea Following Photorefractive Keratectomy.

Purpose: To define the characteristics and time course of the morphologic and functional changes experienced by corneal sensory nerves after photorefractive keratectomy (PRK). Methods: Unilateral corneal excimer laser photoablation was performed in 54 anesthetized 3- to 6-month-old mice; 11 naïve animals served as control. Mice were killed 0, 3, 7, 15, and 30 days after PRK. Excised eyes were placed in a recording chamber superfused at 34°C. Electrical nerve impulse activity of single sensory terminals was recorded with a micropipette applied onto the corneal surface. Spontaneous and stimulus-evoked (cold, heat, mechanical, and chemical stimuli) nerve terminal impulse (NTI) activity was analyzed. Corneas were fixed and stained with anti-ß-Tubulin III antibody to measure nerve density and number of epithelial nerve penetration points of regenerating subbasal leashes. Results: Nerve fibers and NTI activity were absent in the injured area between 0 and 7 days after PRK, when sparse regenerating nerve sprouts appear. On day 15, subbasal nerve density reached half the control value and abnormally responding cold-sensitive terminals were recorded inside the lesion. Thirty days after PRK, nerve density was almost restored, active cold thermoreceptors were abundant, and polymodal nociceptor activity first reappeared. Conclusions: Morphologic regeneration of subbasal corneal nerves started shortly after PRK ablation and was substantially completed 30 days later. Functional recovery appears faster in cold terminals than polymodal terminals, possibly reflecting an incomplete damage of the more extensively branched cold-sensitive axon terminals. Evolution of postsurgical discomfort sensations quality may be associated with the variable regeneration pattern of each fiber type.

Morphological and functional changes in TRPM8-expressing corneal cold thermoreceptor neurons during aging and their impact on tearing in mice.

Morphological and functional alterations of peripheral somatosensory neurons during the aging process lead to a decline of somatosensory perception. Here, we analyze the changes occurring with aging in trigeminal ganglion (TG), TRPM8-expressing cold thermoreceptor neurons innervating the mouse cornea, which participate in the regulation of basal tearing and blinking and have been implicated in the pathogenesis of dry eye disease (DED). TG cell bodies and axonal branches were examined in a mouse line (TRPM8BAC -EYFP) expressing a fluorescent reporter. In 3 months old animals, about 50% of TG cold thermoreceptor neurons were intensely fluorescent, likely providing strongly fluorescent axons and complex corneal nerve terminals with ongoing activity at 34°C and low-threshold, robust responses to cooling. The remaining TRPM8+ corneal axons were weakly fluorescent with nonbeaded axons, sparsely ramified nerve terminals, and exhibited a low-firing rate at 34°C, responding moderately to cooling pulses as do weakly fluorescent TG neurons. In aged (24 months) mice, the number of weakly fluorescent TG neurons was strikingly high while the morphology of TRPM8+ corneal axons changed drastically; 89% were weakly fluorescent, unbranched, and often ending in the basal epithelium. Functionally, 72.5% of aged cold terminals responded as those of young animals, but 27.5% exhibited very low-background activity and abnormal responsiveness to cooling pulses. These morpho-functional changes develop in parallel with an enhancement of tear's basal flow and osmolarity, suggesting that the aberrant sensory inflow to the brain from impaired peripheral cold thermoreceptors contributes to age-induced abnormal tearing and to the high incidence of DED in elderly people.