Use of a hyperdried cross-linked amniotic membrane as initial therapy for corneal perforations

The landscape of clinical trials in corneal regeneration: A systematic review of tissue engineering approaches in corneal disease

The limited availability of a healthy donor cornea and the incidence of allograft failure led researchers to seek other corneal substitutes via tissue engineering. Exploring the trend of clinical trials of the cornea with the vision of tissue engineering provides an opportunity to reveal future potential corneal substitutes. The results of this clinical trial are beneficial for future study designs to overcome the limitations of current therapeutic approaches. In this study, registered clinical trials of bio-based approaches were reviewed for corneal regeneration on March 22, 2024. Among the 3955 registered trials for the cornea, 392 trials were included in this study, which categorized in three main bio-based scaffolds, stem cells, and bioactive macromolecules. In addition to the acellular cornea and human amniotic membrane, several bio-based materials have been introduced as corneal substrates such as collagen, fibrin, and agarose. However, some synthetic materials have been introduced in recent studies to improve the desired properties of bio-based scaffolds for corneal substitutes. Nevertheless, new insights into corneal regenerative medicine have recently emerged from cell sheets with autologous and allogeneic cell sources. In addition, the future perspective of corneal regeneration is described through a literature review of recent experimental models.

Comparison of the effects of preservation methods on structural, biological, and mechanical properties of the human amniotic membrane for medical applications

Amniotic membrane (AM), the innermost layer of the placenta, is an exceptionally effective biomaterial with divers applications in clinical medicine. It possesses various biological functions, including scar reduction, anti-inflammatory properties, support for epithelialization, as well as anti-microbial, anti-fibrotic and angio-modulatory effects. Furthermore, its abundant availability, cost-effectiveness, and ethical acceptability make it a compelling biomaterial in the field of medicine. Given the potential unavailability of fresh tissue when needed, the preservation of AM is crucial to ensure a readily accessible and continuous supply for clinical use. However, preserving the properties of AM presents a significant challenge. Therefore, the establishment of standardized protocols for the collection and preservation of AM is vital to ensure optimal tissue quality and enhance patient safety. Various preservation methods, such as cryopreservation, lyophilization, and air-drying, have been employed over the years. However, identifying a preservation method that effectively safeguards AM properties remains an ongoing endeavor. This article aims to review and discuss different sterilization and preservation procedures for AM, as well as their impacts on its histological, physical, and biochemical characteristics.

Modification of the Human Amniotic Membrane Using Different Cross-Linking Agents as a Promising Tool for Regenerative Medicine

Human amniotic membranes (hAMs) obtained during cesarean sections have proven to be clinically useful as an interesting biomaterial in a wide range of tissue engineering applications such as ocular surface reconstruction, burn treatments, chronic wounds, or bedsore ulcers. It presents antimicrobial properties, promotes epithelization, reduces inflammation and angiogenesis, contains growth factors, and constitutes the reservoir of stem cells. However, variability in hAM stiffness and its fast degradation offers an explanation for the poor clinical applications and reproducibility. In addition, the preparatory method of hAM for clinical use can affect its mechanical properties, and these differences can influence its application. As a directly applied biomaterial, the hAM should be available in a ready-to-use manner in clinical settings. In the present study, we performed an analysis to improve the mechanical properties of hAM by the addition of various reagents used as protein cross-linkers: EDC/NHS, PEG-dialdehyde, PEG-NHS, dialdehyde starch, and squaric acid. The effect of hAM modification using different cross-linking agents was determined via infrared spectroscopy, thermal analyses, mechanical properties analyses, enzymatic degradation, and cytotoxicity tests. The use of PEG-dialdehyde, PEG-NHS, dialdehyde starch, and squaric acid increases the mechanical strength and elongation at the breaking point of hAM, while the addition of EDC/NHS results in material stiffening and shrinkage. Also, the thermal stability and degradation resistance were evaluated, demonstrating higher values after cross-linking. Overall, these results suggest that modification of human amniotic membrane by various reagents used as protein cross-linkers may make it easier to use hAM in clinical applications, and the presented study is a step forward in the standardization of the hAM preparation method.

A comprehensive review on methods for promotion of mechanical features and biodegradation rate in amniotic membrane scaffolds

Amniotic membrane (AM) is a biological tissue that surrounds the fetus in the mother's womb. It has pluripotent cells, immune modulators, collagen, cytokines with anti-fibrotic and anti-inflammatory effect, matrix proteins, and growth factors. In spite of the biological characteristics, some results have been released in preventing the adhesion on traumatized surfaces. Application of the AM as a scaffold is limited due to its low biomechanical resistance and rapid biodegradation. Therefore, for using the AM during surgery, its modification by different methods such as cross-linking of the membrane collagen is necessary, because the cross-linking is an effective way to reduce the rate of biodegradation of the biological materials. In addition, their cross-linking is likely an efficient way to increase the tensile properties of the material, so that they can be easily handled or sutured. In this regard, various methods related to cross-linking of the AM subsuming the composite materials, physical cross-linking, and chemical cross-linking with the glutraldehyde, carbodiimide, genipin, aluminum sulfate, etc. are reviewed along with its advantages and disadvantages in the current work.

Tumor Targeting by Conditioned Medium Derived From Human Amniotic Membrane: New Insight in Breast Cancer Therapy

Objectives:

Traditional breast cancer treatments have challenges including inefficiency, multidrug resistance, severe side effects, and targeting non-specifically. The development of alternative treatment strategies has attracted a great deal of interest. Using the amniotic membrane has become a promising and convenient new approach for cancer therapy. This study aimed to evaluate the anti-cancer ability of conditioned medium extracted from the human amniotic membrane (hAM-CM) on breast cancer cells.

Methods:

Conditioned medium was collected after 48 h incubation of hAM in epithelial up manner. MTT, cell cycle, apoptosis, colony formation, and sphere assays were used to determine the impact of hAM-CM on breast cancer cell lines. The effects of hAM-CM on the migration and invasion of breast cancer cells were determined using scratch wound healing and transwell assays, respectively.

Results:

Based on the results, cell viability was significantly decreased by hAM-CM in a dose-dependent manner. The hAM-CM remarkably induced apoptosis and necrosis of cancer cells. Moreover, cell migration and invasion potential of cancer cells decreased after the hAM-CM treatment. Further, both the number of colonies and their morphologies were affected by the treatment. In the treated group, a significant decrease in the number of colonies along with an obvious change in their morphologies from holoclone shape to a dominant paracolone structure was observed.

Conclusion:

Our results indicate that the conditioned medium derived from the human amniotic membrane able to inhibit proliferation and metastasis of tumor cells and can be considered a natural and valuable candidate for breast cancer therapy.

Significance of Crosslinking Approaches in the Development of Next Generation Hydrogels for Corneal Tissue Engineering

Medical conditions such as trachoma, keratoconus and Fuchs endothelial dystrophy can damage the cornea, leading to visual deterioration and blindness and necessitating a cornea transplant. Due to the shortage of donor corneas, hydrogels have been investigated as potential corneal replacements. A key factor that influences the physical and biochemical properties of these hydrogels is how they are crosslinked. In this paper, an overview is provided of different crosslinking techniques and crosslinking chemical additives that have been applied to hydrogels for the purposes of corneal tissue engineering, drug delivery or corneal repair. Factors that influence the success of a crosslinker are considered that include material composition, dosage, fabrication method, immunogenicity and toxicity. Different crosslinking techniques that have been used to develop injectable hydrogels for corneal regeneration are summarized. The limitations and future prospects of crosslinking strategies for use in corneal tissue engineering are discussed. It is demonstrated that the choice of crosslinking technique has a significant influence on the biocompatibility, mechanical properties and chemical structure of hydrogels that may be suitable for corneal tissue engineering and regenerative applications.

Lamellar Keratoplasty Combined with Amniotic Membrane Transplantation for the Treatment of Corneal Perforations: A Clinical and In Vivo Confocal Microscopy Study

Purpose

To evaluate the clinical and in vivo confocal microscopy outcome of lamellar keratoplasty combined with amniotic membrane transplantation for the treatment of corneal perforations.

Methods

In this retrospective, noncomparative, and interventional case series, 13 eyes of 13 patients with corneal perforation were included. All eyes were treated with lamellar keratoplasty combined with amniotic membrane transplantation for corneal reconstruction. Age, underlying etiology, location, size of corneal ulcer, size of corneal perforation, hospitalization days and follow-up time, and corneal confocal microscopy were investigated. Aqueous leakage, anterior chamber formation, epithelial healing time, and visual acuity (VA) were monitored after operation.

Results

The cause of corneal perforation (n = 13) was classified as infectious (n = 13) was classified as infectious (n = 13) was classified as infectious (

Conclusion

Lamellar keratoplasty combined with amniotic membrane transplantation may be an alternative, safe, and effective surgical therapy in the treatment of corneal perforations in the absence of a fresh donor cornea. We recommend this surgery to treat with the size of corneal perforation of <4 mm in diameter no matter peripheral or central corneal perforation, especially who had immune-related diseases.

Comparison of hyperdry amniotic membrane transplantation and conjunctival autografting for primary pterygium

Background

The purpose of this study was to evaluate the safety and effectiveness of the hyperdry amniotic membrane transplantation compared with conjunctival autografting for the treatment of primary pterygium.

Methods

One hundred and forty-one eyes from 130 patients with primary pterygium were treated with excision followed by hyperdry amniotic membrane or conjunctival autografting after random selection. Seventy-nine eyes from 71 patients received hyperdry amniotic membrane transplantation (HD-AM group), and 62 eyes from 59 patients received conjunctival autografting (CG group). Patients were followed up at one week and one, three, six, and 12 months post-surgery. Recurrence rate, postoperative complications, and final follow-up patient visits were prospectively evaluated.

Results

The mean follow-up duration was 12.56 ± 4.35 months in the HD-AM group and 12.85 ± 3.90 months in the CG group. Recurrences were detected in four eyes (5.06%) in the HD-AM group and 13 eyes (20.97%) in the CG group. A statistically significant difference in frequency of recurrence between the two groups (P = 0.003) was observed. The cumulative non-recurrence rates at six and 12 months in all patients stratified by age and sex were not significantly different (P = 0.642 and P = 0.451, respectively, by log-rank test). Graft retraction and necrosis were not detected in the two groups during the follow-up period.

Conclusion

Hyperdry amniotic membrane transplantation was effective in preventing pterygium recurrence when compared with conjunctival autografting and can be considered a preferable and safe grafting procedure for primary pterygium.

Trial registration

Current Controlled Trials ISRCTN16900270, Retrospectively registered (Date of registration: 3 May 2018).

Concise Review: Altered Versus Unaltered Amniotic Membrane as a Substrate for Limbal Epithelial Cells

Limbal stem cell deficiency (LSCD) can result from a variety of corneal disorders, including chemical and thermal burns, infections, and autoimmune diseases. The symptoms of LSCD may include irritation, epiphora, blepharospasms, photophobia, pain, and decreased vision. There are a number of treatment options, ranging from nonsurgical treatments for mild LSCD to various forms of surgery that involve different cell types cultured on various substrates. Ex vivo expansion of limbal epithelial cells (LEC) involves the culture of LEC harvested either from the patient, a living relative, or a cadaver on a substrate in the laboratory. Following the transfer of the cultured cell sheet onto the cornea of patients suffering from LSCD, a successful outcome can be expected in approximately three out of four patients. The phenotype of the cultured cells has proven to be a key predictor of success. The choice of culture substrate is known to affect the phenotype. Several studies have shown that amniotic membrane (AM) can be used as a substrate for expansion of LEC for subsequent transplantation in the treatment of LSCD. There is currently a debate over whether AM should be denuded (i.e., de-epithelialized) prior to LEC culture, or whether this substrate should remain intact. In addition, crosslinking of the AM has been used to increase the thermal and mechanical stability, optical transparency, and resistance to collagenase digestion of AM. In the present review, we discuss the rationale for using altered versus unaltered AM as a culture substrate for LEC. Stem Cells Translational Medicine 2018;7:415-427.

Patch Grafting Using a Cryopreserved Descemet Stripping Automated Endothelial Keratoplasty Flap for Treating Corneal Perforation

A 73-year-old woman with a corneal perforation of undetermined etiology was treated with corneal patch grafting. A residual partial-thickness corneal button obtained during a previous Descemet stripping automated endothelial keratoplasty (DSAEK) surgery and stored at -80°C in Optisol GS for 3 months was used as a patch graft. Five days postoperatively, the anterior chamber was reformed and the perforation was masked by the donor cornea. During the next several weeks, gradual displacement of the anterior edge of the donor cornea in the limbal direction occurred. Seven weeks postoperatively, further displacement of the donor cornea resulted in unmasking of the perforated area. At this time, the corneal defect was closed by stromal scar tissue and corneal epithelium. Five months postoperatively, best corrected visual acuity was 1.0 without marked astigmatism and intraocular pressure was 9 mm Hg in the left eye. From this case, we learned that cryopreserved DSAEK flaps stored longer than reported previously can be used as patch grafts to treat emergency conditions. Scar tissue can fill a corneal stromal defect 1 mm in diameter during temporary patch grafting for less than 2 months.

New Amniotic Membrane Based Biocomposite for Future Application in Reconstructive Urology

Objective

Due to the capacity of the amniotic membrane (Am) to support re-epithelisation and inhibit scar formation, Am has a potential to become a considerable asset for reconstructive urology i.e., reconstruction of ureters and urethrae. The application of Am in reconstructive urology is limited due to a poor mechanical characteristic. Am reinforcement with electrospun nanofibers offers a new strategy to improve Am mechanical resistance, without affecting its unique bioactivity profile. This study evaluated biocomposite material composed of Am and nanofibers as a graft for urinary bladder augmentation in a rat model.

Material and Methods

Sandwich-structured biocomposite material was constructed from frozen Am and covered on both sides with two-layered membranes prepared from electrospun poly-(L-lactide-co-E-caprolactone) (PLCL). Wistar rats underwent hemicystectomy and bladder augmentation with the biocomposite material.

Results

Immunohistohemical analysis (hematoxylin and eosin [H&E], anti-smoothelin and Masson’s trichrome staining [TRI]) revealed effective regeneration of the urothelial and smooth muscle layers. Anti-smoothelin staining confirmed the presence of contractile smooth muscle within a new bladder wall. Sandwich-structured biocomposite graft material was designed to regenerate the urinary bladder wall, fulfilling the requirements for normal bladder tension, contraction, elasticity and compliance. Mechanical evaluation of regenerated bladder wall conducted based on Young’s elastic modulus reflected changes in the histological remodeling of the augmented part of the bladder. The structure of the biocomposite material made it possible to deliver an intact Am to the area for regeneration. An unmodified Am surface supported regeneration of the urinary bladder wall and the PLCL membranes did not disturb the regeneration process.

Conclusions

Am reinforcement with electrospun nanofibers offers a new strategy to improve Am mechanical resistance without affecting its unique bioactivity profile.

Stem cells from fetal membranes and amniotic fluid: markers for cell isolation and therapy

Stem cell therapy is in constant need of new cell sources to conceive regenerative medicine approaches for diseases that are still without therapy. Scientists drew the attention toward amniotic membrane and amniotic fluid stem cells, since these sources possess many advantages: first of all as cells can be extracted from discarded foetal material it is inexpensive, secondly abundant stem cells can be obtained and finally, these stem cell sources are free from ethical considerations. Many studies have demonstrated the differentiation potential in vitro and in vivo toward mesenchymal and non-mesenchymal cell types; in addition the immune-modulatory properties make these cells a good candidate for allo- and xenotransplantation. This review offers an overview on markers characterisation and on the latest findings in pre-clinical or clinical setting of the stem cell populations isolated from these sources.

Augmented dried versus cryopreserved amniotic membrane as an ocular surface dressing

Purpose

Dried amniotic membrane (AM) can be a useful therapeutic adjunct in ophthalmic surgery and possesses logistical advantages over cryopreserved AM. Differences in preservation techniques can significantly influence the biochemical composition and physical properties of AM, potentially affecting clinical efficacy. This study was established to investigate the biochemical and structural effects of drying AM in the absence and presence of saccharide lyoprotectants and its biocompatibility compared to cryopreserved material.

Methods

AM was cryopreserved or dried with and without pre-treatment with trehalose or raffinose and the antioxidant epigallocatechin (EGCG). Structural and visual comparisons were assessed using electron microscopy. Localisation, expression and release of AM biological factors were determined using immunoassays and immunofluorescence. The biocompatibility of the AM preparations co-cultured with corneal epithelial cell (CEC) or keratocyte monolayers were assessed using cell proliferation, cytotoxicity, apoptosis and migration assays.

Results

Drying devitalised AM epithelium, but less than cryopreservation and cellular damage was reduced in dried AM pre-treated with trehalose or raffinose. Dried AM alone, and with trehalose or raffinose showed greater factor retention efficiencies and bioavailability compared to cryopreserved AM and demonstrated a more sustained biochemical factor time release in vitro. Cellular health assays showed that dried AM with trehalose or raffinose are compatible and superior substrates compared to cryopreserved AM for primary CEC expansion, with increased proliferation and reduced LDH and caspase-3 levels. This concept was supported by improved wound healing in an immortalised human CEC line (hiCEC) co-cultured with dried and trehalose or raffinose membranes, compared to cryopreserved and fresh AM.

Conclusions

Our modified preservation process and our resultant optimised dried AM has enhanced structural properties and biochemical stability and is a superior substrate to conventional cryopreserved AM. In addition this product is stable and easily transportable allowing it to be globally wide reaching for use in clinical and military sectors.

Application of 2-octyl-cyanoacrylate for corneal perforation and glaucoma filtering bleb leak

BACKGROUND

This paper reports on the efficacy of a tissue adhesive, 2-octyl-cyanoacrylate, in the treatment of corneal perforation and glaucoma filtering bleb leak.

METHODS

Two eyes from two patients with corneal perforation or laceration and two eyes from two patients with bleb leak were included. The patients underwent application of 2-octyl-cyanoacrylate onto the perforated or leaking site, and a hydrogel contact lens was applied as a bandage. We also evaluated the in vitro cell toxicity of 2-octyl-cyanoacrylate in HeLa cells.

RESULTS

The two cases of corneal perforation were repaired within 22 days with one application of the tissue adhesive. The two cases of bleb leak were repaired with 2-4 applications of the tissue adhesive over 134 (range 17-134) days). There were no recurrences or adverse effects during a mean follow-up period of 12.7 months. In vitro testing revealed that 2-octyl-cyanoacrylate was markedly toxic to HeLa cells.

CONCLUSION

Four patients with corneal perforation or bleb leak were successfully managed using 2-octyl-cyanoacrylate tissue adhesive. This simple and easy surgical technique may become an alternative therapeutic option for corneal perforation or bleb leak, although several applications of this tissue adhesive may be required. Although 2-octyl-cyanoacrylate was toxic to HeLa cells, no adverse clinical effects were noted using this adhesive.

Applications of amniotic membrane and fluid in stem cell biology and regenerative medicine

The amniotic membrane (AM) and amniotic fluid (AF) have a long history of use in surgical and prenatal diagnostic applications, respectively. In addition, the discovery of cell populations in AM and AF which are widely accessible, nontumorigenic and capable of differentiating into a variety of cell types has stimulated a flurry of research aimed at characterizing the cells and evaluating their potential utility in regenerative medicine. While a major focus of research has been the use of amniotic membrane and fluid in tissue engineering and cell replacement, AM- and AF-derived cells may also have capabilities in protecting and stimulating the repair of injured tissues via paracrine actions, and acting as vectors for biodelivery of exogenous factors to treat injury and diseases. Much progress has been made since the discovery of AM and AF cells with stem cell characteristics nearly a decade ago, but there remain a number of problematic issues stemming from the inherent heterogeneity of these cells as well as inconsistencies in isolation and culturing methods which must be addressed to advance the field towards the development of cell-based therapies. Here, we provide an overview of the recent progress and future perspectives in the use of AM- and AF-derived cells for therapeutic applications.

Amniotic fluid and amniotic membrane stem cells: marker discovery

Amniotic fluid (AF) and amniotic membrane (AM) have been recently characterized as promising sources of stem or progenitor cells. Both not only contain subpopulations with stem cell characteristics resembling to adult stem cells, such as mesenchymal stem cells, but also exhibit some embryonic stem cell properties like (i) expression of pluripotency markers, (ii) high expansion in vitro, or (iii) multilineage differentiation capacity. Recent efforts have been focused on the isolation and the detailed characterization of these stem cell types. However, variations in their phenotype, their heterogeneity described by different groups, and the absence of a single marker expressed only in these cells may prevent the isolation of a pure homogeneous stem cell population from these sources and their potential use of these cells in therapeutic applications. In this paper, we aim to summarize the recent progress in marker discovery for stem cells derived from fetal sources such as AF and AM, using novel methodologies based on transcriptomics, proteomics, or secretome analyses.