Cell Type-Specific Extracellular Vesicles and Their Impact on Health and Disease.

Extracellular vesicles (EVs), a diverse group of cell-derived exocytosed particles, are pivotal in mediating intercellular communication due to their ability to selectively transfer biomolecules to specific cell types. EVs, composed of proteins, nucleic acids, and lipids, are taken up by cells to affect a variety of signaling cascades. Research in the field has primarily focused on stem cell-derived EVs, with a particular focus on mesenchymal stem cells, for their potential therapeutic benefits. Recently, tissue-specific EVs or cell type-specific extracellular vesicles (CTS-EVs), have garnered attention for their unique biogenesis and molecular composition because they enable highly targeted cell-specific communication. Various studies have outlined the roles that CTS-EVs play in the signaling for physiological function and the maintenance of homeostasis, including immune modulation, tissue regeneration, and organ development. These properties are also exploited for disease propagation, such as in cancer, neurological disorders, infectious diseases, autoimmune conditions, and more. The insights gained from analyzing CTS-EVs in different biological roles not only enhance our understanding of intercellular signaling and disease pathogenesis but also open new avenues for innovative diagnostic biomarkers and therapeutic targets for a wide spectrum of medical conditions. This review comprehensively outlines the current understanding of CTS-EV origins, function within normal physiology, and implications in diseased states.

Extracellular-Vesicle-Based Therapeutics in Neuro-Ophthalmic Disorders.

Extracellular vesicles (EVs) have been recognized as promising candidates for developing novel therapeutics for a wide range of pathologies, including ocular disorders, due to their ability to deliver a diverse array of bioactive molecules, including proteins, lipids, and nucleic acids, to recipient cells. Recent studies have shown that EVs derived from various cell types, including mesenchymal stromal cells (MSCs), retinal pigment epithelium cells, and endothelial cells, have therapeutic potential in ocular disorders, such as corneal injury and diabetic retinopathy. EVs exert their effects through various mechanisms, including promoting cell survival, reducing inflammation, and inducing tissue regeneration. Furthermore, EVs have shown promise in promoting nerve regeneration in ocular diseases. In particular, EVs derived from MSCs have been demonstrated to promote axonal regeneration and functional recovery in various animal models of optic nerve injury and glaucoma. EVs contain various neurotrophic factors and cytokines that can enhance neuronal survival and regeneration, promote angiogenesis, and modulate inflammation in the retina and optic nerve. Additionally, in experimental models, the application of EVs as a delivery platform for therapeutic molecules has revealed great promise in the treatment of ocular disorders. However, the clinical translation of EV-based therapies faces several challenges, and further preclinical and clinical studies are needed to fully explore the therapeutic potential of EVs in ocular disorders and to address the challenges for their successful clinical translation. In this review, we will provide an overview of different types of EVs and their cargo, as well as the techniques used for their isolation and characterization. We will then review the preclinical and clinical studies that have explored the role of EVs in the treatment of ocular disorders, highlighting their therapeutic potential and the challenges that need to be addressed for their clinical translation. Finally, we will discuss the future directions of EV-based therapeutics in ocular disorders. Overall, this review aims to provide a comprehensive overview of the current state of the art of EV-based therapeutics in ophthalmic disorders, with a focus on their potential for nerve regeneration in ocular diseases.

A Light-Curable and Tunable Extracellular Matrix Hydrogel for In Situ Suture-Free Corneal Repair.

Corneal injuries are a major cause of blindness worldwide. To restore corneal integrity and clarity, there is a need for regenerative bio-integrating materials for in-situ repair and replacement of corneal tissue. Here, we introduce Light-curable COrnea Matrix (LC-COMatrix), a tunable material derived from decellularized porcine cornea extracellular matrix containing un-denatured collagen and sulfated glycosaminoglycans. It is a functionalized hydrogel with proper swelling behavior, biodegradation, and viscosity that can be cross-linked in situ with visible light, providing significantly enhanced biomechanical strength, stability, and adhesiveness. Cross-linked LC-COMatrix strongly adheres to human corneas ex vivo and effectively closes full-thickness corneal perforations with tissue loss. Likewise, in vivo, LC-COMatrix seals large corneal perforations, replaces partial-corneal stromal defects and bio-integrates into the tissue in rabbit models. LC-COMatrix is a natural ready-to-apply bio-integrating adhesive that is representative of native corneal matrix with potential applications in corneal and ocular surgeries.

Simultaneous fluorescence imaging of distinct nerve and blood vessel patterns in dual Thy1-YFP and Flt1-DsRed transgenic mice.

Blood vessels and nerve tissues are critical to the development and functionality of many vital organs. However, little is currently known about their interdependency during development and after injury. In this study, dual fluorescence transgenic reporter mice were utilized to observe blood vessels and nervous tissues in organs postnatally. Thy1-YFP and Flt1-DsRed (TYFD) mice were interbred to achieve dual fluorescence in the offspring, with Thy1-YFP yellow fluorescence expressed primarily in nerves, and Flt1-DsRed fluorescence expressed selectively in blood vessels. Using this dual fluorescent mouse strain, we were able to visualize the networks of nervous and vascular tissue simultaneously in various organ systems both in the physiological state and after injury. Using ex vivo high-resolution imaging in this dual fluorescent strain, we characterized the organizational patterns of both nervous and vascular systems in a diverse set of organs and tissues. In the cornea, we also observed the dynamic patterns of nerve and blood vessel networks following epithelial debridement injury. These findings highlight the versatility of this dual fluorescent strain for characterizing the relationship between nerve and blood vessel growth and organization.

3D printing for low cost, rapid prototyping of eyelid crutches.

Blepharoptosis or ptosis is a common and potentially debilitating clinical problem. Long-term surgical treatment for ptosis caused by progressive myopathies can be challenging due to potential recurrence and complications associated with facial muscle weakness. When surgical treatment is no longer effective, an eyelid crutch can be used as an alternative intervention. This report demonstrates how 3D printing was used to rapidly design, prototype, and manufacture new custom-fit eyelid crutches at a low cost.

Potential lymphangiogenesis therapies: Learning from current antiangiogenesis therapies-A review.

In recent years, lymphangiogenesis, the process of lymphatic vessel formation from existing lymph vessels, has been demonstrated to have a significant role in diverse pathologies, including cancer metastasis, organ graft rejection, and lymphedema. Our understanding of the mechanisms of lymphangiogenesis has advanced on the heels of studies demonstrating vascular endothelial growth factor C as a central pro-lymphangiogenic regulator and others identifying multiple lymphatic endothelial biomarkers. Despite these breakthroughs and a growing appreciation of the signaling events that govern the lymphangiogenic process, there are no FDA-approved drugs that target lymphangiogenesis. In this review, we reflect on the lessons available from the development of antiangiogenic therapies (26 FDA-approved drugs to date), review current lymphangiogenesis research including nanotechnology in therapeutic drug delivery and imaging, and discuss molecules in the lymphangiogenic pathway that are promising therapeutic targets.

Fluorescent reporter transgenic mice for in vivo live imaging of angiogenesis and lymphangiogenesis.

The study of lymphangiogenesis is an emerging science that has revealed the lymphatic system as a central player in many pathological conditions including cancer metastasis, lymphedema, and organ graft rejection. A thorough understanding of the mechanisms of lymphatic growth will play a key role in the development of therapeutic strategies against these conditions. Despite the known potential of this field, the study of lymphatics has historically lagged behind that of hemangiogenesis. Until recently, significant strides in lymphatic studies were impeded by a lack of lymphatic-specific markers and suitable experimental models compared to those of the more immediately visible blood vasculature. Lymphangiogenesis has also been shown to be a key phenomenon in developmental biological processes, such as cell proliferation, guided migration, differentiation, and cell-to-cell communication, making lymphatic-specific visualization techniques highly desirable and desperately needed. Imaging modalities including immunohistochemistry and in situ hybridization are limited by the need to sacrifice animal models for tissue harvesting at every experimental time point. Moreover, the processes of mounting and staining harvested tissues may introduce artifacts that can confound results. These traditional methods for investigating lymphatic and blood vasculature are associated with several problems including animal variability (e.g., between mice) when replicating lymphatic growth environments and the cost concerns of prolonged, labor-intensive studies, all of which complicate the study of dynamic lymphatic processes. With the discovery of lymphatic-specific markers, researchers have been able to develop several lymphatic and blood vessel-specific, promoter-driven, fluorescent-reporter transgenic mice for visualization of lymphatics in vivo and in vitro. For instance, GFP, mOrange, tdTomato, and other fluorescent proteins can be expressed under control of a lymphatic-specific marker like Prospero-related homeobox 1 (Prox1), which is a highly conserved transcription factor for determining embryonic organogenesis in vertebrates that is implicated in lymphangiogenesis as well as several human cancers. Importantly, Prox1-null mouse embryos develop without lymphatic vessels. In human adults, Prox1 maintains lymphatic endothelial cells and upregulates proteins associated with lymphangiogenesis (e.g., VEGFR-3) and downregulates angiogenesis-associated gene expression (e.g., STAT6). To visualize lymphatic development in the context of angiogenesis, dual fluorescent-transgenic reporters, like Prox1-GFP/Flt1-DsRed mice, have been bred to characterize lymphatic and blood vessels simultaneously in vivo. In this review, we discuss the trends in lymphatic visualization and the potential usage of transgenic breeds in hemangiogenesis and lymphangiogenesis research to understand spatial and temporal correlations between vascular development and pathological progression.

Acute corneal epithelial debridement unmasks the corneal stromal nerve responses to ocular stimulation in rats: implications for abnormal sensations of the eye.

It is widely accepted that the mechanisms for transducing sensory information reside in the nerve terminals. Occasionally, however, studies have appeared demonstrating that similar mechanisms may exist in the axon to which these terminals are connected. We examined this issue in the cornea, where nerve terminals in the epithelial cell layers are easily accessible for debridement, leaving the underlying stromal (axonal) nerves undisturbed. In isoflurane-anesthetized rats, we recorded extracellularly from single trigeminal ganglion neurons innervating the cornea that are excited by ocular dryness and cooling: low-threshold (<2°C cooling) and high-threshold (>2°C) cold-sensitive plus dry-sensitive neurons playing possible roles in tearing and ocular pain. We found that the responses in both types of neurons to dryness, wetness, and menthol stimuli were effectively abolished by the debridement, indicating that their transduction mechanisms lie in the nerve terminals. However, some responses to the cold, heat, and hyperosmolar stimuli in low-threshold cold-sensitive plus dry-sensitive neurons still remained. Surprisingly, the responses to heat in approximately half of the neurons were augmented after the debridement. We were also able to evoke these residual responses and follow the trajectory of the stromal nerves, which we subsequently confirmed histologically. The residual responses always disappeared when the stromal nerves were cut at the limbus, suggesting that the additional transduction mechanisms for these sensory modalities originated most likely in stromal nerves. The functional significance of these residual and enhanced responses from stromal nerves may be related to the abnormal sensations observed in ocular disease.NEW & NOTEWORTHY In addition to the traditional view that the sensory transduction mechanisms exist in the nerve terminals, we report here that the proximal axons (stromal nerves in the cornea from which these nerve terminals originate) may also be capable of transducing sensory information. We arrived at this conclusion by removing the epithelial cell layers of the cornea in which the nerve terminals reside but leaving the underlying stromal nerves undisturbed.

Prox1-GFP/Flt1-DsRed transgenic mice: an animal model for simultaneous live imaging of angiogenesis and lymphangiogenesis.

The roles of angiogenesis in development, health, and disease have been studied extensively; however, the studies related to lymphatic system are limited due to the difficulty in observing colorless lymphatic vessels. But recently, with the improved technique, the relative importance of the lymphatic system is just being revealed. We bred transgenic mice in which lymphatic endothelial cells express GFP (Prox1-GFP) with mice in which vascular endothelial cells express DsRed (Flt1-DsRed) to generate Prox1-GFP/Flt1-DsRed (PGFD) mice. The inherent fluorescence of blood and lymphatic vessels allows for direct visualization of blood and lymphatic vessels in various organs via confocal and two-photon microscopy and the formation, branching, and regression of both vessel types in the same live mouse cornea throughout an experimental time course. PGFD mice were bred with CDh5CreERT2 and VEGFR2lox knockout mice to examine specific knockouts. These studies showed a novel role for vascular endothelial cell VEGFR2 in regulating VEGFC-induced corneal lymphangiogenesis. Conditional deletion of vascular endothelial VEGFR2 abolished VEGFA- and VEGFC-induced corneal lymphangiogenesis. These results demonstrate the potential use of the PGFD mouse as a powerful animal model for studying angiogenesis and lymphangiogenesis.

LIM Homeobox Domain 2 Is Required for Corneal Epithelial Homeostasis.

The cornea requires constant epithelial renewal to maintain clarity for appropriate vision. A subset of stem cells residing at the limbus is primarily responsible for maintaining corneal epithelium homeostasis. Trauma and disease may lead to stem cell deficiency and therapeutic targeting to replenish the stemness capacity has been stalled by the lack of reliable corneal epithelial stem cell markers. Here we identified the location of Lhx2 in mice (mLhx2) cornea and conjunctival tissue using an Lhx2eGFP reporter model and in human tissues (hLHX2). Lhx2 localized to the basal cells of central cornea, the conjunctiva and the entire limbal epithelium in humans and mice. To ascribe a functional role we generated Lhx2 conditional knockout (cKO) mice and the phenotypic effects in corneas were analyzed by slit lamp microscopy, in cell-based assays and in a model of corneal epithelium debridement. Immunodetection on corneal sections were used to visualize conjunctivalization, a sign of limbal barrier failure. Lhx2cKO mice produced reduced body hair and spontaneous epithelial defects in the cornea that included neovascularization, perforation with formation of scar tissue and opacification. Cell based assays showed that Lhx2cKO derived corneal epithelial cells have a significantly lower capacity to form colonies over time and delayed wound-healing recovery when compared to wildtype cells. Repeated corneal epithelial wounding resulted in decreased re-epithelialization and multiple cornea lesions in Lhx2cKO mice compared to normal recovery seen in wildtype mice. We conclude that Lhx2 is required for maintenance of the corneal epithelial cell compartment and the limbal barrier.

Anti-Infective and Anti-Inflammatory Pharmacotherapies.

Ocular infection and inflammation are common and are associated with myriad ocular conditions ranging from mild disease to blinding conditions. There are numerous anti-invectives with spectra against inciting pathogens. Given the potential for ocular infections to rapidly progress initial broad spectrum therapy is usually required, with therapy tailored as microbiological identification and sensitivities become available. The emergence of antibiotic resistance has become a major health problem. Anti-inflammatory therapy can be institutes to prevent ocular symptoms and end-organ damage. A therapy should be selected which is potent enough to interrupt the inflammatory cascades in play, but which avoids potential side effects. Glucocorticoids, NSAIDs, and biological agents may be used singularly or in combination. New drug delivery devices may allow for better local treatment of chronic ocular inflammation.

VEGF-B selectively regenerates injured peripheral neurons and restores sensory and trophic functions.

VEGF-B primarily provides neuroprotection and improves survival in CNS-derived neurons. However, its actions on the peripheral nervous system have been less characterized. We examined whether VEGF-B mediates peripheral nerve repair. We found that VEGF-B induced extensive neurite growth and branching in trigeminal ganglia neurons in a manner that required selective activation of transmembrane receptors and was distinct from VEGF-A-induced neuronal growth. VEGF-B-induced neurite elongation required PI3K and Notch signaling. In vivo, VEGF-B is required for normal nerve regeneration: mice lacking VEGF-B showed impaired nerve repair with concomitant impaired trophic function. VEGF-B treatment increased nerve regeneration, sensation recovery, and trophic functions of injured corneal peripheral nerves in VEGF-B-deficient and wild-type animals, without affecting uninjured nerves. These selective effects of VEGF-B on injured nerves and its lack of angiogenic activity makes VEGF-B a suitable therapeutic target to treat nerve injury.

Endostatin's emerging roles in angiogenesis, lymphangiogenesis, disease, and clinical applications.

BACKGROUND: Angiogenesis is the process of neovascularization from pre-existing vasculature and is involved in various physiological and pathological processes. Inhibitors of angiogenesis, administered either as individual drugs or in combination with other chemotherapy, have been shown to benefit patients with various cancers. Endostatin, a 20-kDa C-terminal fragment of type XVIII collagen, is one of the most potent inhibitors of angiogenesis. SCOPE OF REVIEW: We discuss the biology behind endostatin in the context of its endogenous production, the various receptors to which it binds, and the mechanisms by which it acts. We focus on its inhibitory role in angiogenesis, lymphangiogenesis, and cancer metastasis. We also present emerging clinical applications for endostatin and its potential as a therapeutic agent in the form a short peptide. MAJOR CONCLUSIONS: The delicate balance between pro- and anti-angiogenic factors can be modulated to result in physiological wound healing or pathological tumor metastasis. Research in the last decade has emphasized an emerging clinical potential for endostatin as a biomarker and as a therapeutic short peptide. Moreover, elevated or depressed endostatin levels in diseased states may help explain the pathophysiological mechanisms of the particular disease. GENERAL SIGNIFICANCE: Endostatin was once sought after as the 'be all and end all' for cancer treatment; however, research throughout the last decade has made it apparent that endostatin's effects are complex and involve multiple mechanisms. A better understanding of newly discovered mechanisms and clinical applications still has the potential to lead to future advances in the use of endostatin in the clinic.

Clinical Experience With PROSE Fitting: Significance of Diagnosis and Age.

OBJECTIVE: To compare ease of adoption of the BostonSight Prosthetic Replacement of the Ocular Surface Ecosystem device, a custom-fit scleral lens, by patients in different age and diagnosis groups. METHODS: In this prospective study, patients were categorized by age as younger than 60 or 60 years and older and by diagnosis as corneal irregularity (CI) or ocular surface disease (OSD). Ease of adoption of the scleral device was assessed by (1) number of devices and visits required to complete the fitting process, (2) time needed for device insertion and removal, (3) adaptation to the device, as assessed by daily wear time and by time needed to achieve full-time wear (defined as 8 hours per day), and (4) patients' subjective rating of ease of device insertion and removal. The length of the fitting process was also assessed. RESULTS: There was no significant difference in the number of devices and visits needed between age group younger than 60 and age group of 60 and older or between CI and OSD groups. Patients in all groups achieved full-time wear in less than 2 weeks. Average wear time per week did not differ significantly between age or diagnosis groups. Similarly, the time needed for daily insertion and removal during the fitting period, as well as patients' subjective rating of ease of device insertion and removal, did not differ between age or diagnosis categories. The length of the fitting process was significantly longer in the OSD group compared with the CI group (P<0.001); however, factors not related to ease of adoption of the scleral device may be responsible for this difference. CONCLUSIONS: Patients in both younger and older patient groups adopted the use of a scleral device with equal ease, as did patients in the CI and OSD diagnosis groups.

Boston Keratoprosthesis: Outcomes and Complications: A Report by the American Academy of Ophthalmology.

OBJECTIVE: To review the published literature on safety and outcomes of the Boston type I keratoprosthesis (BI-KPro) for the surgical treatment of corneal opacification not amenable to human cadaveric corneal transplantation. METHODS: Searches of peer-reviewed literature were conducted in PubMed and the Cochrane Library in December 2012, July 2013, and January 2014 without date restrictions. The searches were limited to studies published in English and yielded 587 citations. The abstracts of these articles were reviewed, 48 articles were selected for possible clinical relevance, and 22 were determined to be relevant for the assessment objectives. Nine studies were rated as level II evidence and 13 studies were rated as level III evidence. Excluded were level III evidence, case reports, review articles, letters, editorials, and case series with fewer than 25 eyes. RESULTS: In 9 articles, a best-corrected Snellen visual acuity (BCSVA) of 20/200 or better occurred in 45% to 89% of eyes. Five articles described a BCSVA of 20/50 or better in 43% to 69% of eyes, and 4 articles found a BCSVA of 20/40 or better in 11% to 39% of eyes. Retention rates of the BI-KPro ranged from 65% to 100%. Reasons for loss of vision after BI-KPro implantation most commonly included corneal melts resulting from exposure keratopathy, endophthalmitis, and infectious keratitis or corneal ulceration. The 2 most common complications after surgery were retroprosthetic membrane formation (range, 1.0%-65.0%; mean ± standard deviation [SD], 30.0±19.0%) and elevated intraocular pressure (range, 2.4%-64.0%; mean ± SD, 27.5±18.1%). The 2 most common posterior segment complications were endophthalmitis (range, 0%-12.5%; mean ± SD, 4.6±4.6%) and vitritis (range, 0%-14.5%; mean ± SD, 5.6±4.7%). CONCLUSIONS: The reviewed articles on BI-KPro use suggest that the device improves vision in cases of severe corneal opacification that were not amenable to corneal transplantation using human cadaveric keratoplasty techniques. A number of severe anterior and posterior segment complications can develop as follow-up continues, making ongoing close observation paramount for patients undergoing this surgery. These complications include infection, device extrusion, and permanent vision loss.

Vascular endothelial growth factor promotes anatomical and functional recovery of injured peripheral nerves in the avascular cornea.

Peripheral nerve injury is a major neurological disorder that can cause severe motor and sensory dysfunction. Neurogenic effects of vascular endothelial growth factor (VEGF) have been found in the central nervous system, and we examined whether VEGF could promote anatomical and functional recovery of peripheral nerves after injury using an avascular corneal nerve injury model. We found that VEGF enhanced neurite elongation in isolated trigeminal ganglion neurons in a dose-dependent manner. This effect was suppressed by neutralizing antibodies for VEGF receptor (VEGFR) 1 and 2 or neuropilin receptor 1 or by VEGFR2 inhibitors (SU 1498 and Ki 8751). In vivo, mice receiving sustained VEGF via implanted pellets showed increased corneal nerve regeneration after superficial injury compared with those receiving vehicle. VEGF injected subconjunctivally at the time of injury accelerated reinnervation, the recovery of mechanosensation, and epithelial wound healing. Endogenous VEGF expression was up-regulated in the corneal epithelium and stroma after wounding. Thus, VEGF can mediate peripheral neuron growth but requires the activation of multiple VEGF receptor types. In addition, VEGF can accelerate the return of sensory and trophic functions of damaged peripheral nerves. Wounding induces the expression of VEFG, which may modulate physiological nerve repair.

Magnetic systems for tarsorrhaphy.

PURPOSE: Paralytic lagophthalmos can cause exposure keratopathy. Current treatments have difficulties: extrusion, migration, allergic reaction, anatomical disruption, and technically difficult surgeries. The goal of this study was to design, create, and assess a new method for eyelid closure using magnets. METHODS: This experimental study is approved by institutional review board. Creation of eyelid model and magnet systems: A model of the eyelid and eyeball was constructed to determine the necessary magnetic strength. Neodymium magnets were cast in silicone mold carriers. Assessment of temporary magnet systems in humans: 1) a magnet was affixed to the upper and lower eyelids, and 2) a magnet was affixed to the upper eyelid and another to eyeglasses. Parameters evaluated were eyelid positions and success of eyelid closure in healthy adult volunteers. RESULTS: Magnetic force required to create the average eyelid opening force was calculated from the eyelid model to be equivalent to 4 magnets. The magnet system affixed to upper and lower eyelids resulted in complete eyelid closure in 5 of 5 normal controls, while the magnet system affixed to the upper eyelid and to spectacles resulted in complete eyelid closure in 10 of 13 normal controls. CONCLUSIONS: Magnetic systems for eyelid closure were designed that used either magnets affixed to both upper and lower eyelids or an upper eyelid magnetic component combined with a magnetic element in the lower rim of spectacles. Both were effective in eyelid closure in a model eye and normal controls. These systems may ultimately provide a simplified, safer, and less invasive method to treat paralytic lagophthalmos.

Neurotrophic keratopathy: General features and new therapies.

Neurotrophic keratopathy is an uncommon degenerative corneal disorder characterized by compromised corneal sensory innervation resulting in the formation of epithelial defects and nonhealing corneal ulcers. Various treatment modalities are available to stabilize disease progression, improve patient well-being, and prevent vision loss. For eligible patients, medical and surgical reinnervation have emerged as pioneering therapies, holding promise for better management. We present a comprehensive review of the disorder, providing an update relevant to ophthalmologists on pathogenesis, diagnosis, treatment options, and novel therapies targeting pathophysiological pathways.

Options and adjuvants in surgery for pterygium: a report by the American Academy of Ophthalmology.

OBJECTIVE: To assess the outcomes and safety of current surgical options and adjuvants in the treatment of primary and recurrent pterygium. METHODS: Literature searches of the PubMed and the Cochrane Library databases were last conducted in January 2011 using keywords and were restricted to randomized controlled trials reporting on surgical intervention for pterygium. The searches were limited to articles published in English and yielded 120 citations. Citation abstracts, and if necessary the full text, were reviewed to identify randomized controlled trials that reported recurrence as an outcome measure and had a mean follow-up of at least 6 months. Fifty-one studies comparing bare sclera excision, conjunctival or limbal autograft, intraoperative mitomycin C, postoperative mitomycin C, and amniotic membrane transplantation for primary and recurrent pterygia fit these inclusion criteria. RESULTS: Four studies demonstrated that the conjunctival or limbal autograft procedure is more efficacious than amniotic membrane placement. Use of conjunctival or limbal autografts or mitomycin C during or after pterygium excision reduced recurrence compared with bare sclera excision alone in most studies of primary or recurrent pterygium. The outcomes of conjunctival or limbal autograft were similar to outcomes for intraoperative mitomycin C in the few studies that directly compared the 2 techniques. There is evidence that increased concentration and duration of exposure to intraoperative mitomycin C is associated with increased efficacy. Of the adjuvants studied, only mitomycin C was associated with vision-threatening complications, including scleral thinning, ulceration, and delayed conjunctival epithelialization; there is some evidence of increasing complications with increased concentration and duration of exposure. There is conflicting evidence as to whether increasing age is protective against recurrence, but the morphologic features of the pterygium were shown to affect the recurrence rate. CONCLUSIONS: Evidence indicates that bare sclera excision of pterygium results in a significantly higher recurrence rate than excision accompanied by use of certain adjuvants. Conjunctival or limbal autograft was superior to amniotic membrane graft surgery in reducing the rate of pterygium recurrence. Among other adjuvants, there is evidence that mitomycin C and conjunctival or limbal autografts reduce the recurrence rate after surgical excision of a pterygium. Furthermore, the data indicate that using a combination of conjunctival or limbal autograft with mitomycin C further reduces the recurrence rate after pterygium excision compared with conjunctival or limbal autograft or mitomycin C alone. Additional studies are necessary to determine the long-term effects, optimal route of administration, and dose and duration of treatment for mitomycin C. Factors such as availability of resources, primary or recurrent status of pterygium, age of patient, and surgeon or patient preference may influence the surgeon's choice of adjuvant because there are insufficient data to recommend a specific adjuvant as superior. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

The effect of decellularization protocols on characterizations of thermoresponsive and light-curable corneal extracellular matrix hydrogels.

To compare the effects of two decellularization protocols on the characteristics of fabricated COrnea Matrix (COMatrix) hydrogels. Porcine corneas were decellularized with Detergent (De) or Freeze-Thaw (FT)-based protocols. DNA remnant, tissue composition and α-Gal epitope content were measured. The effect of α-galactosidase on α-Gal epitope residue was assessed. Thermoresponsive and light-curable (LC) hydrogels were fabricated from decellularized corneas and characterized with turbidimetric, light-transmission and rheological experiments. The cytocompatibility and cell-mediated contraction of the fabricated COMatrices were assessed. Both protocols reduced the DNA content to < 0.1 µg/mg (native, > 0.5 µg/mg), and preserved the collagens and glycosaminoglycans. The α-Gal epitope remnant decreased by > 50% following both decellularization methods. We observed more than 90% attenuation in α-Gal epitope after treatment with α-galactosidase. The thermogelation half-time of thermoresponsive COMatrices derived from De-Based protocol (De-COMatrix) was 18 min, similar to that of FT-COMatrix (21 min). The rheological characterizations revealed significantly higher shear moduli of thermoresponsive FT-COMatrix (300.8 ± 22.5 Pa) versus De-COMatrix 178.7 ± 31.3 Pa, p < 0.01); while, this significant difference in shear moduli was preserved after fabrication of FT-LC-COMatrix and De-LC-COMatrix (18.3 ± 1.7 vs 2.8 ± 2.6 kPa, respectively, p < 0.0001). All thermoresponsive and light-curable hydrogels have similar light-transmission to human corneas. Lastly, the obtained products from both decellularization methods showed excellent in vitro cytocompatibility. We found that FT-LC-COMatrix was the only fabricated hydrogel with no significant cell-mediated contraction while seeded with corneal mesenchymal stem cells (p < 0.0001). The significant effect of decellularization protocols on biomechanical properties of hydrogels derived from porcine corneal ECM should be considered for further applications.