Use of Decellularized SMILE (Small-Incision Lenticule Extraction) Lenticules for Engineering the Corneal Endothelial Layer: A Proof-of-Concept

Addition of Microscale Topographies to Silk Fibroin Film Modulates Corneal Endothelial Cell Behavior

Biomimicry in tissue engineering has been used to improve the function of a structure by closely replicating the native architecture. One such method is the introduction of micro- and nanotopographical patterns on biomaterials that mimic the native extracellular environment to enhance cell behavior and function before and after clinical transplantation. Earlier studies from our laboratory had shown that silk fibroin films offer promising potential for corneal endothelial regeneration because of their optimum optical, mechanical, and functional properties. In this study, we hoped to improve upon the design by incorporating micropatterns that are present in the native tissue on the surface of silk films. Fibroin protein from Antheraea assamensis worms was used to prepare films with and without patterns (hexagons and microgrooves) on their surface. The mechanical and optical properties of these films were analyzed by measuring the Young's modulus and light transmittance in the visible spectrum. Cell adhesion and proliferation were determined using the MTT assay and Ki67 staining, respectively. Morphometric analysis of cell shape and size was performed using the ImageJ software, and the expression of markers was visualized and quantified using immunostaining and Western blot. Patterned films demonstrated enhanced elasticity, roughness, and hydrophilicity compared to flat films. No significant difference was observed in cell adhesion between the flat and patterned films. The percentage of proliferating cells was significantly reduced on the patterned films, especially on hexagons. The cell area and circularity on flat films were comparable to microgrooves, whereas cells on hexagons displayed larger and more variable sizes. Notably, the expression of Na-K ATPase (a critical pump protein) was significantly higher in cells grown on microgrooves than on other substrates. These findings suggest that incorporating simple micropatterns on the surface of silk fibroin films can improve the morphology and functional quality of corneal endothelial cells, providing insights into the development of biomaterial-based strategies for endothelial transplantation.

Evolving indications and surgical trends in keratoplasty: a 7-year analysis from a Chinese tertiary referral center

BACKGROUND

The objectives of this study were to investigate the epidemiological characteristics and spectrum of corneal primary diseases among keratoplasty patients in the southern region of Liaoning Province and to study the changing trends in keratoplasty types and corneal graft materials.

METHODS

The medical records of 537 patients who underwent keratoplasty at the Department of Ophthalmology of Dalian Third People's Hospital from 2017 to 2023 were retrospectively analyzed. Patient demographic (age and sex), primary corneal disease type, keratoplasty type and corneal graft material data were statistically analyzed.

RESULTS

A total of 537 patients who underwent keratoplasty during the 7 years study period were included. The average age of the patients was 56.35±15.93 years, ranging from 5 to 90 years. There were 348 male patients (64.8%) and 189 female patients (35.2%), with a ratio of 1.84:1. Among the primary corneal diseases, infectious keratitis was the most common (243, 45.25%), followed by corneal leukoma (73, 13.59%), corneal endothelial decompensation (48, 8.94%), traumatic corneal injury (36, 6.70%), corneal graft rejection (34, 6.33%), immune corneal ulcer (33, 6.15%), keratoconus (32, 5.96%), corneal dystrophy and degeneration (28, 5.21%), and corneal tumor (10, 1.86%). Among infectious keratitis cases, the detailed etiology was as follows: fungal keratitis (154, 63.37%), bacterial keratitis (54, 22.22%), viral keratitis (34, 13.99%), and Acanthamoeba keratitis (1, 0.41%). According to the classification of ker atoplasty types, the most common was PKP (265, 49.35%), followed by DALK (129, 24.02%), ALK (116, 21.60%), and EK (27, 5.03%). PKP is still the main surgical method for corneal transplantation, but the proportions of patients who undergo DALK, ALK, and EK are increasing. The corneal graft materials were classified as fresh human donor corneal grafts (297, 55.31%), dehydrated human donor corneal grafts (166, 30.91%), corneal stromal lenticules (4, 0.74%), and bioengineered corneal grafts (70, 13.04%).

CONCLUSION

Owing to factors such as economic development and industrial distribution, infectious keratitis is the primary cause of keratoplasty in the southern Liaoning region of China, followed by corneal leukoma and corneal endothelial decompensation. Fungal infection is the leading cause of infectious keratitis. The primary keratoplasty type has shifted from PKP to corneal composition transplantation. The range of materials utilized for corneal grafts has expanded significantly and now includes corneal stroma lenticules and bioengineered corneal grafts, in addition to human donor corneal grafts. The present study delineates the evolving surgical patterns and material innovations related to keratoplasty, providing insights for regional ophthalmic policy-making.

Advances in Regenerative Medicine, Cell Therapy, and 3D Bioprinting for Corneal, Oculoplastic, and Orbital Surgery

Advances in regenerative medicine, cell therapy, and 3D bioprinting are reshaping the landscape of ocular surgery, offering innovative approaches to address complex conditions affecting the cornea, ocular adnexal structures, and the orbit. These technologies hold the potential to enhance treatment precision, improve functional outcomes, and address limitations in traditional surgical and therapeutic interventions.The cornea, as the eye's primary refractive and protective barrier, is particularly well-suited for regenerative approaches due to its avascular and immune-privileged nature. Cell-based therapies, including limbal stem cell transplantation as well as stromal keratocyte and corneal endothelial cell regeneration, are being investigated for their potential to restore corneal clarity and function in conditions such as limbal stem cell deficiency, keratoconus, and endothelial dysfunction. Simultaneously, 3D bioprinting technologies are enabling the development of biomimetic corneal constructs, potentially addressing the global shortage of donor tissues and facilitating personalized surgical solutions.In oculoplastic and orbital surgery, regenerative strategies and cell therapies are emerging as possible alternatives to conventional approaches for conditions such as eyelid defects, meibomian gland dysfunction, and Graves' orbitopathy. Stem cell-based therapies and bioengineered scaffolds are showing potential in restoring lacrimal glands' function as well as reconstructing complex ocular adnexal and orbital structures. Moreover, 3D-printed orbital implants and scaffolds offer innovative solutions for repairing traumatic, post-tumor resection, and congenital defects, with the potential for improved biocompatibility and precision.Molecular and gene-based therapies, including exosome delivery systems, nanoparticle-based interventions, and gene-editing techniques, are expanding the therapeutic arsenal for ophthalmic disorders. These approaches aim to enhance the efficacy of regenerative treatments by addressing underlying pathophysiological mechanisms of diseases. This chapter provides an overview of these advancements and the challenges of translating laboratory discoveries into effective therapies in clinical practice.

Biologicals and Biomaterials for Corneal Regeneration and Vision Restoration in Limbal Stem Cell Deficiency

The mammalian cornea is decorated with stem cells bestowed with the life-long task of renewing the epithelium, provided they remain healthy, functional, and in sufficient numbers. If not, a debilitating disease known as limbal stem cell deficiency (LSCD) can develop causing blindness. Decades after the first stem cell (SC) therapy is devised to treat this condition, patients continue to suffer unacceptable failures. During this time, improvements to therapeutics have included identifying better markers to isolate robust SC populations and nurturing them on crudely modified biological or biomaterial scaffolds including human amniotic membrane, fibrin, and contact lenses, prior to their delivery. Researchers are now gathering information about the biomolecular and biomechanical properties of the corneal SC niche to decipher what biological and/or synthetic materials can be incorporated into these carriers. Advances in biomedical engineering including electrospinning and 3D bioprinting with surface functionalization and micropatterning, and self-assembly models, have generated a wealth of biocompatible, biodegradable, integrating scaffolds to choose from, some of which are being tested for their SC delivery capacity in the hope of improving clinical outcomes for patients with LSCD.

Emerging alternatives to keratoplasty for corneal endothelial cell dysfunction

PURPOSE OF REVIEW

While effective for treating endothelial dysfunction, keratoplasty has shortcomings including limited access to donor tissue for much of the world. Thus, alternative strategies are under development. This review explores the main advancements achieved in this field during 2022-2023.

RECENT FINDINGS

Recent publications further support the validity of intracameral cultivated allogeneic endothelial cell injection and Descemet stripping only, while emphasizing the benefits of adjunctive Rho-associated kinase inhibitor (ROCKi) therapy. New donor-independent artificial implants, such as EndoArt, show favorable results. Multiple pharmacologic agents, especially ROCKi, show promise as monotherapies, yet none are currently approved for human treatment. Multiple regenerative and genetic therapies are being investigated but all are still in preclinical stages.

SUMMARY

A plethora of innovative alternatives to keratoplasty for endothelial disease is in development. Among these, surgical methods are still the mainstay of treatment and closest to clinical application, though further studies to establish their benefits over keratoplasty are needed. Albeit promising, pharmacologic, regenerative, and genetic approaches require validation and are farther from clinical application.

Chemical, Physical, and Biological Corneal Decellularization Methods: A Review of Literature

The cornea is one of the most commonly transplanted tissues worldwide. It is used to restore vision when severe visual impairment or blindness occurs in patients with corneal diseases or after trauma. Due to the global shortage of healthy donor corneas, decellularized corneal tissue has significant potential as an alternative to corneal transplantation. It preserves the native and biological ultrastructure of the cornea and, therefore, represents the most promising scaffold. This article discusses different methods of corneal decellularization based on the current literature. We searched PubMed.gov for articles from January 2009 to December 2023 using the following keywords: corneal decellularization, decellularization methods, and corneal transplantation. Although several methods of decellularization of corneal tissue have been reported, a universal standardised protocol of corneal decellularization has not yet been introduced. In general, a combination of decellularization methods has been used for efficient decellularization while preserving the optimal properties of the corneal tissue.

In Vitro Profiling of the Extracellular Matrix and Integrins Expressed by Human Corneal Endothelial Cells Cultured on Silk Fibroin-Based Matrices

Developing a scaffold for culturing human corneal endothelial (HCE) cells is crucial as an alternative cell therapeutic approach to bridge the growing gap between the demand and availability of healthy donor corneas for transplantation. Silk films are promising substrates for the culture of these cells; however, their tensile strength is several-fold greater than the native basement membrane which can possibly influence the dynamics of cell-matrix interaction and the extracellular matrix (ECM) secreted by the cells in long-term culture. In our current study, we assessed the secretion of ECM and the expression of integrins by the HCE cells on Philosamia ricini (PR) and Antheraea assamensis (AA) silk films and fibronectin-collagen (FNC)-coated plastic dishes to understand the cell-ECM interaction in long-term culture. The expression of ECM proteins (collagens 1, 4, 8, and 12, laminin, and fibronectin) on silk was comparable to that on the native tissue. The thicknesses of collagen 8 and laminin at 30 days on both PR (4.78 ± 0.55 and 5.53 ± 0.51 μm, respectively) and AA (4.66 ± 0.72 and 5.71 ± 0.61 μm, respectively) were comparable with those of the native tissue (4.4 ± 0.63 and 5.28 ± 0.72 μm, respectively). The integrin expression by the cells on the silk films was also comparable to that on the native tissue, except for α3 whose fluorescence intensity was significantly higher on PR (p ≤ 0.01) and AA (p ≤ 0.001), compared to that on the native tissue. This study shows that the higher tensile strength of the silk films does not alter the ECM secretion or cell phenotype in long-term culture, confirming the suitability of using this material for engineering the HCE cells for transplantation.