Keratoprosthesis Research Articles

Histological, histochemical, and immunohistochemical characterization of NANOULCOR nanostructured fibrin-agarose human cornea substitutes generated by tissue engineering.

Human artificial corneas (HAC) generated by tissue engineering recently demonstrated clinical usefulness in the management of complex corneal diseases. However, the biological mechanisms associated to their regenerative potential need to be elucidated. In the present work, we generated HAC using nanostructured fibrin-agarose biomaterials with cultured corneal epithelial and stromal cells, and we compared the structure and histochemical and immunohistochemical profiles of HAC with control native corneas (CTR-C) and limbus (CTR-L) to determine the level of biomimicry of the HAC with these two native organs. HAC tissues consisted of a stratified epithelium and a cellular stromal substitute. The interface between stroma and epithelium was similar to that of CTR-C, without the finger-shaped palisades of Vogt found in CTR-L, and contained a poorly developed basement membrane as determined by PAS histochemistry. Analysis of the stromal layer revealed that HAC contained significantly lower amounts of extracellular matrix components (collagen, proteoglycans, decorin, keratocan, and lumican) than CTR-C and CTR-L, with all samples being devoid of elastic and reticular fibers. At the epithelial level, HAC were strongly positive for several cytokeratins, although KRT5 was lower in HAC as compared to CTR-C and CTR-L. The expression of crystallin lambda was lower in HAC than in control tissues, whereas crystallin alpha-a was similar in HAC and CTR-C. No differences were found among HAC and controls for the cell-cell junction proteins CX43 and TJP1. When specific markers were analyzed, we found that HAC expression profile of KRT3, KRT19, KRT15, and ΔNp63 was more similar to CTR-L than to CTR-C. These results suggest that HAC generated in the laboratory could be structurally and functionally more biomimetic to the structure found at the corneal limbus than to the central cornea, and open the door to the use of these artificial tissues in patients with limbal deficiency.

3D-printed artificial cornea featuring aligned fibrous structure and enhanced mechanical strength

The global shortage of donor eye bank tissue has significantly impeded advancements in biomaterial for corneal implantation. To address this issue, we have developed a 3D-printed artificial cornea using a composite hydrogel of sodium alginate (SA) and cellulose nanofibers (CNF), crosslinked with poly-L-lysine-co-L-glutamic acid (PLL80GA20, PG) and calcium chloride (CaCl2, CC). The 2 wt% SA/CNF composite hydrogel offers several advantages, including low toxicity, cost-effectiveness, excellent printability, and high mechanical strength, even with low crosslinker concentrations. The PG was synthesized via ring-opening polymerization of L-glutamate N-carboxyl anhydride (BGNCA) and L-lysine N-carboxyl anhydride (CBZNCA). The purity of the monomers was verified through DSC analysis, revealing a melting point of 97 ℃. The molecular weight of the synthesized PG was determined to be 47 kDa. A dual crosslinking strategy was employed, starting with electrostatic crosslinking, followed by ionic crosslinking using varying concentrations of PG and CC at different effective charge concentrations of 6.25 mM, 12.25 mM, and 25 mM. The hydrogel and 3D-printed cornea were comprehensively evaluated for chemical structure, surface functional groups, water content, mechanical strength, orientation, cytotoxicity, biocompatibility, and transparency. Notably, the inclusion of PG significantly enhanced the mechanical properties of the 3D-printed cornea, with the hydrogel achieving a storage modulus of 2,360 kPa at 6.25 mM of PG/CC, while maintaining over 95% water content. The artificial cornea demonstrated 86% transparency, and the cell viability showed 96% viable on Day 7 with degradation rate of 35.9% in 28 days. The superior hydrophilicity, transparency, and mechanical strength of the printed hydrogel highlights its potential for the development of full-thickness corneal structures, making it a promising candidate for future corneal implants.

A new approach of aspheric intralamellar keratoprostheses optic design made with poly(2-hydroxy ethylmethacrylate) hydrogel

Keratoprosthesis (KPro) is a surgical procedure largely confined to end-stage corneal blindness correction, where artificial cornea substitutes the native tissue. Though the problem of bio integration was addressed partially by strategic utilization of synthetic polymers and native tissue, major challenges like optical performance and design-associated post-operative complications of KPro were overlooked. Herein, a novel intralamellar KPro design is conceptualized to address these challenges using a light-transparent poly(2-hydroxy ethylmethacrylate) (pHEMA) hydrogel with good shape memory. pHEMA-based optics’ theoretically modelled refractive surfaces for both phakic and aphakic conditions were investigated against the standard Navarro model and optimized to new aspheric geometries having high optical functionality utilizing the Zemax OpticStudio software. The optical clear aperture size standardized achieved a 15% improvement in the illumination field. The introduction of asphericity on the two refractive surfaces of the optic on both models resulted in substantial improvements in the spot spread confinement on the retina, spatial resolution, and Seidel aberration. The design simulation study shows that the developed materials’ optical characteristics coupled with newly optimized refractive surface geometries can indeed deliver very high visual performance. Furthermore, the procedure can be adapted to analyze and optimize the optical performance of a KPro, intraocular lens, or contact lens.

Design and Biocompatibility of a Novel, Flexible Artificial Cornea.

We sought to introduce the materials, design, and biocompatibility of a flexible and suturable artificial corneal device. Single-piece, fully synthetic, optic-skirt design devices were made from compact perfluoroalkoxy alkane. The skirt and the optic wall surfaces were lined with a porous tissue ingrowth material using expanded polytetrafluoroethylene. Full-thickness macroapertures around the skirt perimeter were placed to facilitate nutrition of the recipient cornea. Material properties including the skirt's modulus of elasticity and bending stiffness, optic light transmission, wetting behavior, topical drug penetrance, and degradation profile were evaluated. The final prototype suitable for human use has a transparent optic with a diameter of 4.60mm anteriorly, 4.28mm posteriorly, and a skirt outer diameter of 6.8mm. The biomechanical and optical properties of the device closely align with the native human cornea with an average normalized device skirt-bending stiffness of 4.7kPa·mm4 and light transmission in the visible spectrum ranging between 92% and 96%. No optical damage was seen in the 36 devices tested in fouling experiments. No significant difference was observed in topical drug penetrance into the anterior chamber of the device implanted eye compared with the naïve rabbit eye. The flexibility and biocompatibility of our artificial cornea device may offer enhanced tissue integration and decreased inflammation, leading to improved retention compared with rigid keratoprosthesis designs. We have developed a fully synthetic, flexible, suturable, optic-skirt design prototype artificial cornea that is ready to be tested in early human feasibility studies.

A novel intralamellar semi‐bioresorbable keratoprosthesis—Part A: Design conception, material perspective, and device manufacturing

AbstractCorneal diseases are a significant cause of visual impairment and blindness. The first‐line treatment for corneal opacity is penetrating keratoplasty (human donor cornea transplantation). At present, keratoprosthesis (KPro), an artificial cornea, is the last resort for correcting end‐stage corneal blindness and is usually supported by donor tissue. This article describes a new intralamellar tissue‐free KPro design concept and its preparation method. Wherein, an injection‐molding route is adopted to create a mechanically and structurally stable near‐KPro geometry using a photo‐polymerized poly(2‐hydroxyethyl methacrylate) (pHEMA) with 4% Bisphenol A dimethacrylate (BisMA) crosslinked (PC4) hydrogel composition. Prior to this, the physico‐mechanical properties of crosslinked hydrogels matching corneal tissue are identified, and the surface morphological characteristics of silk cocoon membranes are ascertained in choosing suitable KPro materials. Cytocompatibility tests on PC4 and silk‐incorporated PC4 hydrogels using rabbit corneal fibroblast cell‐line evidenced enhancement in cell growth on silk‐PC4 surfaces. Furthermore, near KPro geometry is surface‐profiled to create a one‐of‐a‐kind design with clear optics and a silk‐bioactivated composite‐based haptic‐flange hydrogel network containing site‐specific submillimeter‐scale perforations to improve tissue integration. Considering this unique KPro geometry, the optic‐haptic‐flange construct is a tissue‐free semi‐bioresorbable hydrogel device presumed to provide stability under the influence of intraocular pressure (IOP) and eyelid shear. Through this study, it is identified new KPro materials facilitate significant cytocompatibility while complimented with site‐specific novel design would offer tissue ingrowth with gradual resorption of silk, leaving behind a stable intralamellar tissue integrated with hydrogel when implanted in the corneal niche.

3D bioprinting of stromal cells-laden artificial cornea based on visible light-crosslinkable bioinks forming multilength networks

3D bioprinting has the potential for the rapid and precise engineering of hydrogel constructs that can mimic the structural and optical complexity of a healthy cornea. However, the use of existing light-activated bioinks for corneal printing is limited by their poor cytocompatibility, use of cytotoxic photoinitiators (PIs), low photo-crosslinking efficiency, and opaque/colored surface of the printed material. Herein, we report a fast-curable, non-cytotoxic, optically transparent bioprinting system using a new water-soluble benzoyl phosphinate-based PI and photocrosslinkable methacrylated hyaluronic acid (HAMA). Compared with commercially available PIs, the newly developed PI, lithium benzoyl (phenyl) phosphinate (BP), demonstrated increased photoinitiation efficiency under visible light and low cytotoxicity. Using a catalytic amount of BP, the HA-based bioinks quickly formed 3D hydrogel constructs under low-energy visible-light irradiation (405 nm, <1 J cm−2). The mechanical properties and printability of photocurable bioinks were further improved by blending low (10 kDa) and high (100 kDa) molecular weight (MW) HAMA by forming multilength networks. For potential applications as corneal scaffolds, stromal cell-laden dome-shaped constructs were fabricated using MW-blended HAMA/BP bioink and a digital light processing printer. The HA-based photocurable bioinks exhibited good cytocompatibility (80%–95%), fast curing kinetics (<5 s), and excellent optical transparency (>90% in the visible range), potentially making them suitable for corneal tissue engineering.

Development of a novel bioartificial cornea using 3D bioprinting based on electrospun micro-nanofibrous decellularized extracellular matrix

Corneal damage contributes to blindness in millions of people. Simulating natural corneas with artificial corneas is challenging due to material and manufacturing limitations, including poor mechanical properties, complex manufacturing processes, and ocular histocompatibility. In this study, electrospun micro-nanofibrous decellularized extracellular matrix (dECM) is combined with digital light processing 3D bioprinting and validated as a bioartificial cornea for the first time. Electrospinning gives the material a controllable shape, and the electrospun micro-nanofibrous dECM, with preserved inherent biochemical components, can better mimic the natural ECM native microenvironment. An efficient platform can be developed for creating novel structural materials, when combined with intelligent manufacturing. Artificial biological corneas developed using this method showed five-fold improvements in mechanical properties (248.5 ± 35.67 kPa vs. 56.91 ± 3.68 kPa, p < 0.001), superior guidance for cell organization and adhesion, and better maintenance of the cellular phenotype of keratocytes. In animal studies, in vivo transplantation of this artificial cornea showed better regeneration, which accelerated corneal epithelialization and maintained corneal transparency. This method has potential for biomedical applications, and bioartificial corneas manufactured by this method have ideal properties as an alternative to lamellar keratoplasty, with promise for clinical transformation.

Challenges of obtaining cultured corneal endothelial cells for regenerative purposes

Human posterior corneal epithelium (corneal endothelium) has limited proliferative activity both in vivo and in vitro. Disease or dysfunction in these cells leads to impaired corneal transparency of varying degrees of severity, up to blindness. Currently, the only effective standard treatment for corneal endothelial dysfunction is transplantation of donor cornea that contains a pool of healthy and functionally active cells. However, there is a global shortage of donor corneas, which has led to an unmet clinical need and the fact that only 1 patient out of 10 in need receives surgical treatment. Therefore, creation of cellular constructs and artificial human corneas containing healthy endothelium is a very urgent challenge facing modern ophthalmic transplantology. This review presents the current state of affairs, challenges and prospects for obtaining cultured corneal endothelial cells (CECs) in vitro for transplantation purposes.

Advances in tissue engineering and 3D bioprinting for corneal regeneration

Blindness resulting from corneal damage affects millions of people worldwide. The scarcity of corneal donors adds a layer of complexity to patient treatment. Consequently, exploring artificial cornea substitutes has become imperative in the realm of clinical research. Scientific advancements have ushered in a plethora of innovative solutions, including keratoprostheses or decellularized cornea scaffolds. The development of three-dimensional (3D) printing has further expanded the horizons of research in this field, delving into the feasibility of bioprinted corneas and yielding numerous promising outcomes. However, the manufacturing of corneal products via 3D printing poses a substantial challenge, demanding a meticulous selection of materials and techniques to ensure the transparency and preservation of the optical and mechanical properties of the artificial cornea. In the review, we present the artificial cornea substitutes. Additionally, we aim to provide a concise overview of the 3D printing techniques and materials applicable to corneal bioprinting.

Artificial corneas ‐ Recent developments

Many regenerative medicine technologies have now entered the clinical realm with the help of biomaterials. Biomaterials, in conjunction with therapeutic stem or immune cells or cell products, are used to engineer tissues for in vivo testing platforms (organs‐on‐chips) or clinical use. However, biomaterials can also be used to stimulate in situ tissue regeneration to avoid adverse immune reactions. In ophthalmology, human donor corneas have served well for corneal transplant surgery. However, the massive shortage of suitable donor tissue combined with the expense and technical challenges of eye banking leaves a substantial proportion of the world's population without access to treatment. Here, we discuss the development of novel biomaterials for corneal implants that stimulate in situ tissue regeneration and the pathway to getting these into clinical trials. The results of clinical and pre‐clinical trials will be discussed.

Novel strategy for multi-material 3D bioprinting of human stem cell based corneal stroma with heterogenous design

Three-dimensional (3D) bioprinting offers an automated, customizable solution to manufacture highly detailed 3D tissue constructs and holds great promise for regenerative medicine to solve the severe global shortage of donor tissues and organs. However, uni-material 3D bioprinting is not sufficient for manufacturing heterogenous 3D constructs with native-like microstructures and thus, innovative multi-material solutions are required. Here, we developed a novel multi-material 3D bioprinting strategy for bioprinting human corneal stroma. The human cornea is the transparent outer layer of your eye, and vision loss due to corneal blindness has serious effects on the quality of life of individuals. One of the main reasons for corneal blindness is the damage in the detailed organization of the corneal stroma where collagen fibrils are arranged in layers perpendicular to each other and the corneal stromal cells grow along the fibrils. Donor corneas for treating corneal blindness are scarce, and the current tissue engineering (TE) technologies cannot produce artificial corneas with the complex microstructure of native corneal stroma. To address this, we developed a novel multi-material 3D bioprinting strategy to mimic detailed organization of corneal stroma. These multi-material 3D structures with heterogenous design were bioprinted by using human adipose tissue -derived stem cells (hASCs) and hyaluronic acid (HA) -based bioinks with varying stiffnesses. In our novel design of 3D models, acellular stiffer HA-bioink and cell-laden softer HA-bioink were printed in alternating filaments, and the filaments were printed perpendicularly in alternating layers. The multi-material bioprinting strategy was applied for the first time in corneal stroma 3D bioprinting to mimic the native microstructure. As a result, the soft bioink promoted cellular growth and tissue formation of hASCs in the multi-material 3D bioprinted composites, whereas the stiff bioink provided mechanical support as well as guidance of cellular organization upon culture. Interestingly, cellular growth and tissue formation altered the mechanical properties of the bioprinted composite constructs significantly. Importantly, the bioprinted composite structures showed good integration to the host tissue in ex vivo cornea organ culture model. As a conclusion, the developed multi-material bioprinting strategy provides great potential as a biofabrication solution for manufacturing organized, heterogenous microstructures of native tissues. To the best of our knowledge, this multi-material bioprinting strategy has never been applied in corneal bioprinting. Therefore, our work advances the technological achievements in additive manufacturing and brings the field of corneal TE to a new level.

Biocompatibility and Transplantation Efficacy of the C-Clear Artificial Cornea in a Rabbit Chemical Burn Model.

We investigated the bioavailability and stability of a C-Clear artificial cornea in a rabbit chemical burn model. Thirty-six rabbits were divided into a control group (n = 16) and a chemical burn group that used NaOH solution (n = 20). After lamellar dissection, the central posterior lamella was excised using a 3 mm diameter trephine, and an artificial cornea was transplanted into the lamellar pocket. After 2 weeks, the central anterior lamella was excised using a 3 mm diameter trephine to secure a clean visual axis. We examined the anterior segment of the eyes weekly for 12 weeks after transplantation. Successful subjects whose artificial corneas were maintained stably for 12 weeks were euthanized and underwent histologic examinations. Artificial corneas remained stable for up to 12 weeks in 62.5 and 50% of rabbits in the control and chemical burn groups, respectively. Two rabbits in the chemical burn group showed the formation of a retroprosthetic membrane, and one rabbit with visual axis blockage underwent membrane removal using a Nd:YAG laser. In histologic examinations, adhesion between artificial cornea and peripheral corneal stoma was observed. In conclusion, we confirmed structural stability and biocompatibility of the C-Clear artificial cornea for up to 12 weeks after implantation in control and chemical burn groups.

Preparation and Characterization of a Photo-Crosslinked Methacryloyl-Collagen Composite Film to Promote Corneal Nerve Regeneration via Surface Grafting of Taurine Molecules.

Blindness is frequently caused by corneal abnormalities, and corneal transplantation is the most effective treatment method. It is extremely important to develop high-quality artificial corneas because there are not enough donor corneas accessible for cornea transplantation. One of the most-often utilized materials is collagen, which is the primary component of natural cornea. Collagen-based corneal repair materials have good physicochemical properties and excellent biocompatibility, but how to promote the regeneration of the corneal nerve after keratoplasty is still a big challenge. In this research, in order to promote the growth of nerve cells on a collagen (Col) substrate, a novel collagen-based material was synthesized starting from the functionalization of collagen with unsaturated methacryloyl groups that three-dimensionally photopolymerize to a 3D network of chemically crosslinked collagen (ColMA), onto which taurine molecules were eventually grafted (ColMA-Tr). The physicochemical properties and biocompatibility of the Col, ColMA and ColMA-Tr films were evaluated. By analyzing the results, we found that all the three samples had good moisture retention and aq high covalent attachment of methacryloyl groups followed by their photopolymerization improved the mechanical properties of the ColMA and ColMA-Tr. Most importantly, compared with ColMA, the taurine-modified collagen-MA film significantly promoted the growth of nerve cells and corneal epithelial cells on its surface. Our preliminary results suggest that this novel ColMA-Tr film may have potential use in cornea tissue engineering in the future.

Comparative Analysis of Optical Quality of Monofocal, Enhanced Monofocal, Multifocal, and Extended Depth of Focus Intraocular Lenses: A Mobile Model Eye Study.

To use the revised model eye to observe and compare how the world is perceived by patients with monofocal intraocular lens (IOL), Eyhance, bifocal IOL, and Symfony, and check its performance. The new mobile model eye consists of an artificial cornea, an IOL, a wet cell, an adjustable lens tube, a lens tube, an objective lens, a tube lens, and a digital single-lens reflex camera. We collected photographs of distant buildings and streets at night, videos of the focusing process, and videos of United States Air Force resolution target from 6m to 15 cm and analyzed them quantitatively. In this revised model eye using an objective lens, an artificial cornea similar to the human cornea could be used. Using a digital single-lens reflex camera, high-resolution imaging was possible without an additional computer. Fine focusing was possible using an adjustable lens tube. For monofocal IOL, the contrast modulation was 0.39 at 6m and decreased consistently. It was nearly 0 as the model eye got closer than 1.6m. For Eyhance, the contrast modulation was 0.40 at 6m. It then decreased and increased again. At 1.3 m, it was 0.07 and then decreased again. For Symfony, the contrast modulation was 0.18 at 6m. Symfony showed the characteristics of a bifocal IOL with low add diopter. Halos (234 pixels) were observed around lights, although smaller than those seen with bifocal IOL (432 pixels). We could objectively observe and compare how patients with monofocal IOL, Eyhance, bifocal IOL, and Symfony perceived the world using this revised model eye. Data obtained by this new mobile model eye can be used to help patients select their IOLs before cataract surgeries.

Scaffolds for drug delivery and tissue engineering: The role of genetics.

Scaffolds are implants commonly used to deliver cells, drugs, and genes into the body. Their regular porous structure ensures the proper support for cell attachment, proliferation, differentiated function, and migration. Techniques to fabricate a scaffold include leaching, freeze-drying, supercritical fluid technology, thermally induced phase separation, rapid prototyping, powder compaction, sol-gel, and melt molding. Gene delivery from the scaffold represents a versatile approach to influence the environment for managing cell function. Scaffolds can be used for various tissue engineering purposes, e.g. bone formation, periodontal regeneration, cartilage development, artificial corneas, heart valves, tendon repair, or ligament replacement. Moreover, they are also instrumental in cancer therapy, inflammation, diabetes, heart disease, and wound dressings. Scaffolds provide a platform to extend the delivery of drugs and genetic materials at a controlled timeframe, besides potentially being used to prevent infection upon surgery and other chronic diseases, provided that they can be formulated with specific medicines. This review discusses the need to design advanced functional scaffolds with the potential for modified drug delivery and tissue engineering in a synergistic approach. Special attention is given to works published in 2023 to generate the bibliometric map.

Application of biomaterials and nanotechnology in corneal tissue engineering.

Corneal diseases are among the most common causes of blindness worldwide. Regardless of the etiology, corneal opacity- or globe integrity-threatening conditions may necessitate corneal replacement procedures. Several procedure types are currently available to address these issues, based on the complexity and extent of injury. Corneal allograft or keratoplasty is considered to be first-line treatment in many cases. However, a significant proportion of the world's population are reported to have no access to this option due to limitations in donor preparation. Thus, providing an appropriate, safe, and efficient synthetic implant (e.g., artificial cornea) may revolutionize this field. Nanotechnology, with its potential applications, has garnered a lot of recent attention in this area, however, there is seemingly a long way to go. This narrative review provides a brief overview of the therapeutic interventions for corneal pathologies, followed by a summary of current biomaterials used in corneal regeneration and a discussion of the nanotechnologies that can aid in the production of superior implants.

3D bioprinting of corneal decellularized extracellular matrix: GelMA composite hydrogel for corneal stroma engineering.

Millions of individuals across the world suffer from corneal stromal diseases that impair vision. Fortunately, three-dimensional (3D) bioprinting technology which has revolutionized the field of regenerative tissue engineering makes it feasible to create personalized corneas. In this study, an artificial cornea with a high degree of precision, smoothness, and programmable curvature was prepared by using digital light processing (DLP) 3D bioprinting in one piece with no support structure, and the construct was then confirmed by optical coherence tomography (OCT). On the basis of this approach, we developed a novel corneal decellularized extracellular matrix/gelatin methacryloyl (CECM-GelMA) bioink that can produce complex microenvironments with highly tunable mechanical properties while retaining high optical transmittance. Furthermore, the composite hydrogel was loaded with human corneal fibroblasts (hCFs), and in vitro experiments showed that the hydrogel maintained high cell viability and expressed core proteins. In vivo tests revealed that the hydrogel might promote epithelial regeneration, keep the matrix aligned, and restore clarity. This demonstrates how crucial a role CECM plays in establishing a favorable environment that encourages the transformation of cell function. Therefore, artificial corneas that can be rapidly customized have a huge potential in the development of in vitro corneal matrix analogs.

Keratoprosthesis in dry eye disease.

Bilateral corneal blindness with severe dry eye disease (DED), total limbal stem cell deficiency with underlying corneal stromal scarring and vascularization, combined with adnexal complications secondary to chronic cicatrizing conjunctivitis is a highly complex situation to treat. In such eyes, procedures such as penetrating keratoplasty alone or combined with limbal stem cell transplantation are doomed to fail. In these eyes, keratoprosthesis (Kpro) or an artificial cornea is the most viable option, eliminating corneal blindness even in eyes with autoimmune disorders such as Stevens-Johnson syndrome, ocular mucous membrane pemphigoid, Sjogren's syndrome, and nonautoimmune disorders such as chemical/thermal ocular burns, all of which are complex pathologies. Performing a Kpro in these eyes also eliminates the need for systemic immunosuppression and may provide relatively early visual recovery. In such eyes, the donor cornea around the central cylinder of the Kpro needs to be covered with a second layer of protection to avoid desiccation and progressive stromal melt of the underlying cornea, which is a common complication in eyes with severe DED. In this review, we will focus on Kpro designs that have been developed to survive in eyes with the hostile environment of severe DED. Their outcomes in such eyes will be discussed.

Development of stromal differentiation patterns in heterotypical models of artificial corneas generated by tissue engineering.

Purpose: We carried out a histological characterization analysis of the stromal layer of human heterotypic cornea substitutes generated with extra-corneal cells to determine their putative usefulness in tissue engineering. Methods: Human bioartificial corneas were generated using nanostructured fibrin-agarose biomaterials with corneal stromal cells immersed within. To generate heterotypical corneas, umbilical cord Wharton's jelly stem cells (HWJSC) were cultured on the surface of the stromal substitutes to obtain an epithelial-like layer. These bioartificial corneas were compared with control native human corneas and with orthotypical corneas generated with human corneal epithelial cells on top of the stromal substitute. Both the corneal stroma and the basement membrane were analyzed using histological, histochemical and immunohistochemical methods in samples kept in culture and grafted in vivo for 12months in the rabbit cornea. Results: Our results showed that the stroma of the bioartificial corneas kept ex vivo showed very low levels of fibrillar and non-fibrillar components of the tissue extracellular matrix. However, in vivo implantation resulted in a significant increase of the contents of collagen, proteoglycans, decorin, keratocan and lumican in the corneal stroma, showing higher levels of maturation and spatial organization of these components. Heterotypical corneas grafted in vivo for 12months showed significantly higher contents of collagen fibers, proteoglycans and keratocan. When the basement membrane was analyzed, we found that all corneas grafted in vivo showed intense PAS signal and higher contents of nidogen-1, although the levels found in human native corneas was not reached, and a rudimentary basement membrane was observed using transmission electron microscopy. At the epithelial level, HWJSC used to generate an epithelial-like layer in ex vivo corneas were mostly negative for p63, whereas orthotypical corneas and heterotypical corneas grafted in vivo were positive. Conclusion: These results support the possibility of generating bioengineered artificial corneas using non-corneal HWJSC. Although heterotypical corneas were not completely biomimetic to the native human corneas, especially ex vivo, in vivo grafted corneas demonstrated to be highly biocompatible, and the animal cornea became properly differentiated at the stroma and basement membrane compartments. These findings open the door to the future clinical use of these bioartificial corneas.

Probing mechanisms and improving management of glaucoma following Boston keratoprosthesis surgery.

Corneal blindness is a leading cause of visual impairment worldwide. The most common treatment is to replace the diseased cornea with standard corneal transplantation. In eyes at high risk of graft failure, the Boston keratoprosthesis type 1 (KPro) can be used to restore vision and is currently the most frequently used artificial cornea in the world. However, glaucoma is a well-known complication of KPro surgery and is the most important threat to vision in KPro-implanted eyes. This chronic disease is influenced by elevated intraocular pressure (IOP) and damages the optic nerve, leading to progressive vision loss. In KPro patients, glaucoma is highly prevalent and extremely challenging to manage, yet its exact cause remains unknown.