Ocular surface repair using decellularized porcine conjunctiva

Therapeutic application of decellularized porcine small intestinal submucosa scaffold in conjunctiva reconstruction

The objective of this study was to investigate the biological feasibility and surgical applicability of decellularized porcine small intestinal submucosa (DSIS) in conjunctiva reconstruction. A total of 52 Balb/c mice were included in the study. We obtained the DSIS by decellularization, evaluated the physical and biological properties of DSIS in vitro, and further evaluated the effect of surgical transplantation of DSIS scaffold in vivo. The histopathology and ultrastructural analysis results showed that the scaffold retained the integrity of the fibrous morphology while removing cells. Biomechanical analysis showed that the elongation at break of the DSIS (239.00 ± 12.51%) were better than that of natural mouse conjunctiva (170.70 ± 9.41%, P < 0.05). Moreover, in vivo experiments confirmed the excellent biocompatibility of the decellularized scaffolds. In the DSIS group, partial epithelialization occurred at day-3 after operation, and the conjunctival injury healed at day-7, which was significantly faster than that in human amniotic membrane (AM) and sham surgery (SHAM) group (P < 0.05). The number and distribution of goblet cells of transplanted DSIS were significantly better than those of the AM and SHAM groups. Consequently, the DSIS scaffold shows excellent biological characteristics and surgical applicability in the mouse conjunctival defect model, and DSIS is expected to be an alternative scaffold for conjunctival reconstruction.

Research progress of photo-crosslink hydrogels in ophthalmology: A comprehensive review focus on the applications

Hydrogel presents a three-dimensional polymer network with high water content. Over the past decade, hydrogel has developed from static material to intelligent material with controllable response. Various stimuli are involved in the formation of hydrogel network, among which photo-stimulation has attracted wide attention due to the advantages of controllable conditions, which has a good application prospect in the treatment of ophthalmic diseases. This paper reviews the application of photo-crosslink hydrogels in ophthalmology, focusing on the types of photo-crosslink hydrogels and their applications in ophthalmology, including drug delivery, tissue engineering and 3D printing. In addition, the limitations and future prospects of photo-crosslink hydrogels are also provided.

Polymers and Biomaterials for Posterior Lamella of the Eyelid and the Lacrimal System

The application of biopolymers in the reconstruction of the posterior lamella of the eyelid and the lacrimal system marks a significant fusion of biomaterial science with clinical advancements. This review assimilates research spanning 2015 to 2023 to provide a detailed examination of the role of biopolymers in reconstructing the posterior lamella of the eyelid and the lacrimal system. It covers the anatomy and pathophysiology of eyelid structures, the challenges of reconstruction, and the nuances of surgical intervention. This article progresses to evaluate the current gold standards, alternative options, and the desirable properties of biopolymers used in these intricate procedures. It underscores the advancements in the field, from decellularized grafts and acellular matrices to innovative natural and synthetic polymers, and explores their applications in lacrimal gland tissue engineering, including the promise of 3D bioprinting technologies. This review highlights the importance of multidisciplinary collaboration between material scientists and clinicians in enhancing surgical outcomes and patient quality of life, emphasizing that such cooperation is pivotal for translating benchtop research into bedside applications. This collaborative effort is vital for restoring aesthetics and functionality for patients afflicted with disfiguring eyelid diseases, ultimately aiming to bridge the gap between innovative materials and their clinical translation.

Decellularized Porcine Conjunctiva in Treating Severe Symblepharon

This prospective study aimed to evaluate the effectiveness of decellularized porcine conjunctiva (DPC) in the management of severe symblepharon. Sixteen patients with severe symblepharon were enrolled in this study. After symblepharon lysis and Mitomycin C (MMC) application, tarsus defects were covered with residual autologous conjunctiva (AC), autologous oral mucosa (AOM), or DPC throughout the fornix, and DPC was used for all the exposed sclera. The outcomes were classified as complete success, partial success, or failure. Six symblepharon patients had chemical burns and ten had thermal burns. Tarsus defects were covered with DPC, AC, and AOM in two, three, and eleven cases, respectively. After an average follow-up of 20.0 ± 6 months, the anatomical outcomes observed were complete successes in twelve (three with AC+DPC, four with AC+AOM+DPC, and five with AOM+DPC) (75%) cases, partial successes in three (one with AOM+DPC and two with DPC+DPC) (18.75%) cases, and failure in one (with AOM+DPC) (6.25%) case. Before surgery, the depth of the narrowest part of the conjunctival sac was 0.59 ± 0.76 mm (range, 0-2 mm), tear fluid quantity (Schirmer II tests) was 12.5 ± 2.26 mm (range, 10-16 mm), and the distance of the eye rotation toward the opposite direction of the symblepharon was 3.75 ± 1.39 mm (range, 2-7 mm). The fornix depths increased to 7.53 ± 1.64 mm (range, 3-9 mm), eye movement was significantly improved, and the distance of eye movement reaching 6.56 ± 1.24 mm (range, 4-8 mm) 1 month after the operation; the postoperative Schirmer II test (12.06 ± 2.90 mm, range, 6-17 mm) was similar to that before surgery. Goblet cells were finally found in fifteen patients by conjunctival impression cytology in the transplantation area of DPC, except for one patient who failed. DPC could be considered an alternative for ocular surface reconstruction of severe symblepharon. Covering tarsal defects with autologous mucosa is necessary for extensive reconstruction of the ocular surface.

Influence of Storage Conditions on Decellularized Porcine Conjunctiva

Porcine decellularized conjunctiva (PDC) represents a promising alternative source for conjunctival reconstruction. Methods of its re-epithelialization in vitro with primary human conjunctival epithelial cells (HCEC) have already been established. However, a long-term storage method is required for a simplified clinical use of PDC. This study investigates the influence of several storage variants on PDC. PDC were stored in (1) phosphate-buffered saline solution (PBS) at 4 °C, (2) in glycerol-containing epithelial cell medium (EM/gly) at −80 °C and (3) in dimethyl sulfoxide-containing epithelial cell medium (EM/DMSO) at −196 °C in liquid nitrogen for two and six months, respectively. Fresh PDC served as control. Histological structure, biomechanical parameters, the content of collagen and elastin and the potential of re-epithelialization with primary HCEC under cultivation for 14 days were compared (n = 4–10). In all groups, PDC showed a well-preserved extracellular matrix without structural disruptions and with comparable fiber density (p ≥ 0.74). Collagen and elastin content were not significantly different between the groups (p ≥ 0.18; p ≥ 0.13, respectively). With the exception of the significantly reduced tensile strength of PDC after storage at −196 °C in EM/DMSO for six months (0.46 ± 0.21 MPa, p = 0.02), no differences were seen regarding the elastic modulus, tensile strength and extensibility compared to control (0.87 ± 0.25 MPa; p ≥ 0.06). The mean values of the epithelialized PDC surface ranged from 51.9 ± 8.8% (−196 °C) to 78.3 ± 4.4% (−80 °C) and did not differ significantly (p ≥ 0.35). In conclusion, all examined storage methods were suitable for storing PDC for at least six months. All PDC were able to re-epithelialize, which rules out cytotoxic influences of the storage conditions and suggests preserved biocompatibility for in vivo application.

[Methods of surgical reconstruction of the conjunctiva]

Reconstruction of the conjunctiva is required for restoration of damaged ocular surface and is an essential part of that process. Traumas, chemical and thermal burns, multiple surgical intervention can seriously damage the integrity of conjunctival tissue and promote the growth of fibrous tissue, scarring of contractures and their shortening, as well as other complications such as trichiasis, erosion and ulcers on the cornea. When a larger area is affected, there may not be enough donor tissue to replace the defect, in which case the tissue grafts are required to be large enough. Modern modifications of surgical techniques and the continued development of tissue engineering, as well as advancements in stem cell research offer promising novel alternatives for solution of those problems. This article reviews the existing surgical methods of conjunctival reconstruction.

Application of Decellularized Porcine Sclera in Repairing Corneal Perforations and Lamellar Injuries

Scleras are mainly used for the treatment of glaucoma, eyelid damage, and scleral ulcers. Given that the sclera and cornea collectively constitute the complete external structure of the eyeball and both have the same tissue and cell origin, we attempted to identify scleral materials to treat lamellar and penetrating corneal injuries. Based on research in our center, antigenic components in decellularized porcine sclera (DPS) were removed using a simplified decellularization method, leaving the collagen structure and active components undamaged. DPS preserved the mechanical properties and did not significantly inhibit the proliferation and replication of human corneal epithelial cells. In vivo, the graft epithelium healed well after lamellar and penetrating scleral grafting, and the graft thickness did not change evidently. DPS can resist suture traction during scleral transplantation and maintain anterior chamber stability until day 28 post-operatively, especially in penetrating repairs. No obvious immune rejection of lamellar or penetrating scleral grafts was found 28 days after DPS transplantation. This study shows that DPS could be used as an alternative material for the emergency repair of corneal perforations and lamellar injuries, representing another application of sclera.

Aspartic acid and epidermal growth factor modified decellularized rabbit conjunctiva for conjunctival reconstruction

Conjunctival reconstruction is an indispensable part of ocular surface regeneration. Decellularized matrix has been considered as an ideal conjunctival substitution for conjunctival reconstruction. In the present study, we report the use of a decellularized rabbit conjunctiva (DRC) for conjunctival reconstruction in the rabbit surgical trauma model. Prepared by the phospholipase A₂ decellularized method, the DRC was nearly DNA free while the collagen structure and natural extracellular matrix (ECM) were well preserved. In order to improve the performance of DRC, aspartic acid (Asp) was used as a spacer arm to crosslink epidermal growth factor (EGF) on the DRC to obtain DRC-Asp-EGF. The conjunctival epithelial cells cultured on the DRC-Asp-EGF showed a higher survival rates and a greater potential to differentiate into conjunctival goblet cells (CGCs) than those on the DRC. Finally, three groups were set to evaluate the transplantation effects in the rabbit surgical trauma model for 28 days: DRC-Asp-EGF group, amniotic membrane (AM) group, and ungrafted group. The DRC-Asp-EGF group was completely re-epithelized, and more CGCs were regenerated than the AM group, while no significant improvements were observed in the ungrafted group. Intact collagen structure, angiogenesis, and no scar formation were also observed in the DRC-Asp-EGF group. These results suggest that DRC-Asp-EGF is a feasible and effective transplant for conjunctival reconstruction and ocular surface regeneration.

Sutureless transplantation using a semi-interpenetrating polymer network bioadhesive for ocular surface reconstruction

The conjunctiva covers the largest area of ocular surface and is responsible for tear balance and clear vision. After trauma or surgery, the conjunctiva is prone to scarring and contracture. Transplantation with suture often implies numerous complications, such as inflammation, suture erosion, granuloma. And the suture needs to be removed, which means a secondary trauma. In this study, a (GMO) for sutureless conjunctival transplantation was developed based on a semi-interpenetrating polymer network (sIPN) consisting of gelatin methacrylate (GelMA) and oxidized hyaluronic acid (OHA). The maximum adhesion strength was 157 ± 17 kPa, and the burst pressure was 357 ± 29 kPa, which was 15 times higher than the human intraocular pressure (IOP). GMO bioadhesive hydrogel significantly improved surgical efficiency and secured the collagen scaffold firmly to a rabbit conjunctival defect. The sutureless transplantation approach revealed the promoted tissue repair without scar. In conclusion, GMO bioadhesive may be an attractive alternative to suture for ocular surface reconstruction by avoiding suture-related complications and improving clinical outcome. STATEMENT OF SIGNIFICANCE: Conjunctival tissue is prone to scarring and contracture after trauma, and surgery with sutures often implies numerous complications. In this study, the ocular surface reconstruction was achieved by sutureless transplantation of conjunctival scaffold using bioadhesive hydrogel. The prepared GMO bioadhesive based on the semi-interpenetrating network of gelatin methacrylate (GelMA) and oxidized hyaluronic acid (OHA) had favorable adhesion and mechanical properties. The sutureless transplantation approach significantly improved the operation efficiency, avoided suture-related complications, and promoted the regeneration of conjunctiva. This study highlights the great potential of the sutureless repair strategy for clinical application in ocular surface reconstruction.

Efficacy and Safety of Amniotic Membrane Transplantation Combined with Closure of Tenon Capsule and Bulbar Conjunctival Space in the Treatment of Primary Pterygium

Objective

The aim of the study is to evaluate the safety and effectiveness of amniotic membrane transplantation combined with the closure of the tenon capsule and bulbar conjunctival space.

Methods

This study retrospectively included 100 patients with primary pterygium who received closed bulbar conjunctiva and tenon capsule space combined with amniotic membrane transplantation in our hospital from January 2020 to June 2021 as the experimental group and 100 patients with routine treatment in the same period as the control group. The postoperative efficacy evaluation and postoperative complications of the two groups were compared, so as to comprehensively evaluate the safety and effectiveness of this method.

Results

The results showed that the postoperative complications of the two groups were significantly improved by Fisher's exact test (χ² = 14.510, P = 0.006 < 0.05). The comparison results showed that the treatment group showed significant advantages in six indexes compared with the observation group and the difference between the two groups was statistically significant (P < 0.05) of in the NRS score, Prabhasawat score, inspection of the ocular surface comprehensive analyzer, corneal fluorescein staining, conjunctival fluorescein staining in the operation area, breakup time of tear film examination of the two groups at 3, 7 and 14 days, and 1, 6 and 12 months after the operation.

Conclusions

Amniotic membrane transplantation combined with the closure of the tenon capsule and bulbar conjunctival space is safer than conventional surgery in the treatment of primary pterygium. It has a shorter recovery time, higher safety, and a positive curative effect. It can be considered to popularize this operation in clinic.

[Conjunctival reconstruction-State of the art of regenerative treatment forms beyond the limbus]

BACKGROUND

The demands on conjunctival replacement tissues are high: they need to be elastic, clinically compatible, surgically feasible and support goblet cell growth.

OBJECTIVE

This article provides an overview of currently applied conjunctival replacement tissues and those under investigation.

METHOD

Current publications on clinically applied conjunctival replacement tissues and substrates which are the subject of scientific research and those already tested in animal models are presented and discussed.

RESULTS

Replacement tissues in clinical use are autologous and allogenic conjunctiva, nasal and oral mucous membranes, amniotic membrane and decellularized tissues. Autologous conjunctiva shows good results but is not suitable for large defects due to limited availability. In these cases autologous nasal and oral mucous membranes can be used; however, success is limited in cases of autoimmune diseases. Amniotic membranes are frequently applied clinically but goblet cell growth is limited. Different decellularized tissues are used clinically and goblet cell growth was found in vivo. Robust comparative studies are not yet available. Biological matrices such as fibrin, collagen, elastin, gelatin or hyaluronate and synthetic tissues from the group of polyesters are being investigated in the laboratory and in animal models. These studies show good epithelialization and goblet cell growth in vivo.

CONCLUSION

Transplantation of conjunctiva, nasal and oral mucous membranes and amniotic membranes show satisfactory clinical results but exhibit individual weaknesses. Further studies in animal models and clinical settings are required to further evaluate the benefits of other matrices, such as cell-free tissues or other biological and synthetic matrices.

Crosslinked Decellularized Porcine Pericardium as a Substrate for Conjunctival Reconstruction

Seeking for suitable conjunctival reconstruction substitutes to overcome the limitations of current substitutes, such as amniotic membrane, is urgent. Decellularized tissues have become a promising strategy for tissue engineering. In this study, we prepared decellularized porcine pericardium (DPP) scaffolds by the phospholipase A2 method and crosslinked them with aspartic acid (Asp) and human endothelial growth factor (hEGF) to enhance biological performance on the DPP, obtaining DPP-Asp-hEGF scaffolds. In vitro DPP showed lower apoptosis, highly desirable, well preservation of extracellular matrix components, and favorable macro-microstructure, which was confirmed by histology, immunofluorescence, electron microscopy, collagen and DNA quantification, and cytotoxicity assay, compared to the native porcine pericardium (NPP). The crosslinked efficacy of the DPP-Asp-hEGF was furtherer verified by in vitro experiments with Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Through animal models of conjunctiva defect model, the DPP-Asp-hEGF revealed a closed, multilayer epithelium with an equal amount of goblet cells and no indication for conjunctival scarring after 28 days, compared to amniotic membrane (AM) groups and sham groups. These results suggested that DPP-Asp-hEGF can offer a good conjunctival reconstructive substitute both in structure and in function.

Biological tissues and components, and synthetic substrates for conjunctival cell transplantation

The conjunctiva is the largest component of the ocular surface. It can be damaged by various pathological processes leading to scarring, loss of tissue and dysfunction. Depending on the amount of damage, restoration of function may require a conjunctival graft. Numerous studies have investigated biological and synthetic substrates in the search for optimal conditions for the ex vivo culture of conjunctival epithelial cells that can be used as tissue grafts for transplantation. These substrates have advantages and disadvantages that are specific to the characteristics of each material; the development of an improved material remains a priority. This review is the second of a two-part review in The Ocular Surface. In the first review, the structure and function of the conjunctiva was evaluated with a focus on the extracellular matrix and the basement membrane, and biological and mechanical characteristics of the ideal substrate with recommendations for further studies. In this review the types of biological and synthetic substrates used for conjunctival transplantation are discussed including substrates based on the extracellular matrix. .

Decellularized porcine cornea-derived hydrogels for the regeneration of epithelium and stroma in focal corneal defects

PURPOSE

Hydrogels derived from decellularized tissues provide superior biocompatibility, tenability and tissue-specific extracellular matrix (ECM) components. Based on the preparation of decellularized porcine cornea (DPC), here we developed an injectable and transparent hydrogel for the regeneration of epithelium and stroma in focal corneal defects.

METHODS

The DPC-derived hydrogel was prepared with N-cyclohexyl-N'-(2-morpholinethyl) carbodiimide metho-p-toluenesulfonate/N-hydroxysuccinimide (CMC/NHS) as cross-linkers. The characteristics of the hydrogel were analyzed and its cytocompatibility was assessed by Live/Dead and Cell Counting Kit (CCK)-8 assays. Immunofluorescence staining, quantitative PCR and Western blot analyses were performed to assess the relative protein and gene expression in corneal fibroblasts on hydrogel. The safety and efficiency of the hydrogel for repairing focal corneal defects in rabbit were measured by slit-lamp, anterior segment optical coherence tomography (AS-OCT), confocal microscopy and histological analyses.

RESULTS

The DPC-derived hydrogel cross-linked with CMC/NHS assumed favorable transparency, exhibited distinct mechanical properties and preserved the ECM components of native porcine cornea (NPC). In vitro experiments showed that the hydrogel maintained the phenotype, supported the proliferation and promoted the ECM synthesis of corneal fibroblasts. When injected onto rabbit corneas, the hydrogel rapidly covered, solidified and formed a smooth surface on the focal defect. Corneal epithelium was fully regenerated within 3 days. The thickness of the corneal epithelium and stroma was restored at 12 weeks after surgery without significant inflammation or scar formation. Notably, the hydrogel showed no harmful effects on the resident stroma and endothelium.

CONCLUSIONS

The DPC-derived hydrogel may represent a promising biomaterial for corneal epithelial and stromal regeneration.