Ocular surface rehabilitation: Application of human amniotic membrane in high-risk penetrating keratoplasties

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.

Precise longitudinal monitoring of corneal change through in vivo confocal microscopy in a rat dry eye disease model

Purpose

While lacrimal gland removal is commonly used in animal models to replicate dry eye disease, research into systematically monitoring dry eye disease's longitudinal pathological changes is limited. In vivo confocal microscopy (Heidelberg Retina Tomograph 3 with a Rostock Cornea Module, Heidelberg Engineering Inc., Franklin, MA) can non-invasively reveal corneal histopathological structures. To monitor dry-eye-disease-related changes in corneal structures, we developed a precise monitoring method using in vivo confocal microscopy in a rat double lacrimal gland removal model.

Methods

Five Sprague-Dawley rats (age 8-9 weeks, male) underwent double lacrimal gland removal. Modified Schirmer's tear test, blink tests, and in vivo confocal microscopy images were acquired pre-surgery and at 1, 2, and 4 weeks post-surgery. Three individual stromal nerves were selected per eye as guide images, and images of the corresponding sub-basal nerve plexus area were acquired via volume acquisition. The same area was re-imaged in subsequent weeks.

Results

After double lacrimal gland removal, tear production was reduced by 60%, and the blink rate increased 10 times compared to pre-surgery. Starting from 1 week after surgery, in vivo confocal microscopy showed increased sub-basal nerve plexus nerve fiber density with inflammatory cell infiltration at the sub-basal nerve plexus layer and remained at an elevated level at 2 and 4 weeks post-surgery.

Conclusions

We demonstrated that our precise monitoring method revealed detailed changes in the corneal nerves, the epithelium, and the stroma.

Prevention of Corneal Myofibroblastic Differentiation In Vitro Using a Biomimetic ECM Hydrogel for Corneal Tissue Regeneration

Corneal scarring is one of the major causes of blindness, affecting millions worldwide. Despite recent advancements in surgical strategies, there is an unmet need for a clinically feasible material and methods to prevent scarring following corneal injury. In this study, we report the potential utility of a hydrogel derived from cadaveric animal corneas, using a decellularized corneal matrix hydrogel (abbreviated as dCMH), which is prepared by a simple method. This hydrogel is easily injectable, biocompatible, and has the ability to maintain good shape-retention properties at 37 °C, which make it suitable for in vivo applications. Furthermore, our gene expression studies and immunofluorescence studies indicate that dCMH maintains the morphology and function of keratocytes in vitro and prevents their transdifferentiation to myofibroblasts. From the above results, it is evident that dCMH maintains the keratocytes with the ability to regenerate the corneal defect without scar. We thus suggest a simple yet effective approach for corneal tissue decellularization and that dCMH can be a promising material for prophylaxis against blinding scar formation in an injured cornea.

Human Amniotic Membrane: A review on tissue engineering, application, and storage

Human amniotic membrane (hAM) has been employed as scaffolding material in a wide range of tissue engineering applications, especially as a skin dressing and as a graft for corneal treatment, due to the structure of the extracellular matrix and excellent biological properties that enhance both wound healing and tissue regeneration. This review highlights recent work and current knowledge on the application of native hAM, and/or production of hAM-based tissue-engineered products to create scaffolds mimicking the structure of the native membrane to enhance the hAM performance. Moreover, an overview is presented on the available (cryo) preservation techniques for storage of native hAM and tissue-engineered products that are necessary to maintain biological functions such as angiogenesis, anti-inflammation, antifibrotic and antibacterial activity.

Cost utility analysis of cryopreserved amniotic membrane versus topical cyclosporine for the treatment of moderate to severe dry eye syndrome

BACKGROUND

The purpose is to perform a cost effectiveness analysis amniotic membrane vs. topical medications in the use of treating dry eye disease. A cost effectiveness analysis comparing amniotic membrane + other topical medications to topical cyclosporine A + other topical medications was evaluated using accepted decision tree modeling software.

METHODS

TreeAge Pro 2019 software was used to evaluate the base case costs over a one year timeframe. Sensitivity analysis was performed on those variables which had the greatest effect on choosing one therapy versus the other based on cost. Monte Carlo simulation was run 1,000 times to determine the most effective, least costly alternative. Costs were evaluated from a societal level (direct + indirect). Quality of life utility scores were evaluated using known time tradeoffs from prior studies (scale 0-1; with 1 being perfect vision).

RESULTS

Over a one year timeframe, the base case demonstrated that amniotic membrane + topical medications was the less expensive alternative and provided for incremental utilities versus topical cyclosporine + other medications (Cost/utility: $18,275/0.78 vs. $20,740/0.74). If examining direct costs only, topical cyclosporine was the least expensive option over a one year timeframe: $4,112 vs. $10,300. Sensitivity analysis demonstrated that in order for topical cyclosporine to be the less expensive alternative the following variables would need to be: < 68 days productivity lost; < $161 productivity lost/day; > 79% of amniotic membrane implants would need to be re-implanted at month 4 (for whatever reason); > $2677 per amniotic membrane implant procedure (Medicare reimbursement rate); > 96% positive response to topical cyclosporine A at month 4; > 58% positive response to topical cyclosporine A at month 6 and; < 54% probability clinical improvement with amniotic membrane. Monte Carlo simulation demonstrated that amniotic membrane was the less costly, most effective alternative 91.5% of the time.

CONCLUSION

Based on improved outcomes using amniotic membrane, patient productivity was improved resulting in lower societal costs (less days lost from work). When considering the untoward effects of dry eye disease on societal costs, an improvement of the dry eye disease condition was accomplished most often with amniotic membrane.

The Positive Effects of the Human Amniotic Membrane on the Healing of Staple Line After Sleeve Gastrectomy Applied Long-Evans Rat Model

BACKGROUND

The staple line leakage is a dangerous complication of sleeve gastrectomy. Various strategies have been tried to reduce the leakage risk. The amniotic membrane (AmM) is the inner layer of the placental membranes and has anti-inflammatory, anti-fibrosis, and anti-scarring effects, and it also has lower immune characteristics which are another essential characteristic of AmM concerning its utility for grafting. In this study, we aimed to investigate the impact of AmM on the staple line healing process of sleeve gastrectomy model in rats.

MATERIALS AND METHODS

We used twenty-eight Long-Evans rats in this study. Sleeve gastrectomy was performed with tristapler. Fourteen rats served as controls, AmM was applied staple line of the other fourteen. Fourteen animals were sacrificed (seven from the AmM applied group and the other seven from the control group) on the third postoperative day. And, the other fourteen animals were sacrificed (seven from the AmM applied group and seven from the control group) on the seventh postoperative day. The tissue around the staple line was evaluated microscopically and macroscopically, bursting pressures and hydroxyproline levels were also measured.

RESULTS

The bursting pressure and hydroxyproline measurements of the AmM applied group was significantly higher on the seventh postoperative day (p = 0.015, p = 0.012) Fibroblast activity and neoangiogenesis of the AmM applied group was also significantly higher on the seventh postoperative day (p = 0.004, p = 0.002).

CONCLUSION

This study showed that covering of staple line of sleeve gastrectomy model in rats significantly provided higher bursting pressures and increased hydroxyproline levels, fibroblast activity, and neoangiogenesis which may potentially lead a better staple line healing. We think further investigations are needed on this issue.

Sustained release of decorin to the surface of the eye enables scarless corneal regeneration

Disorganization of the transparent collagenous matrix in the cornea, as a consequence of a variety of infections and inflammatory conditions, leads to corneal opacity and sight-loss. Such corneal opacities are a leading cause of blindness, according to the WHO. Public health programs target prevention of corneal scarring, but the only curative treatment of established scarring is through transplantation. Although attempts to minimize corneal scarring through aggressive control of infection and inflammation are made, there has been little progress in the development of anti-scarring therapies. This is owing to eye drop formulations using low viscosity or weak gelling materials having short retention times on the ocular surface. In this study, we report an innovative eye drop formulation that has the ability to provide sustained delivery of decorin, an anti-scarring agent. The novelty of this eye drop lies in the method of structuring during manufacture, which creates a material that can transition between solid and liquid states, allowing retention in a dynamic environment being slowly removed through blinking. In a murine model of Pseudomonaskeratitis, applying the eye drop resulted in reductions of corneal opacity within 16 days. More remarkably, the addition of hrDecorin resulted in restoration of corneal epithelial integrity with minimal stromal opacity endorsed by reduced α-smooth muscle actin (αSMA), fibronectin, and laminin levels. We believe that this drug delivery system is an ideal non-invasive anti-fibrotic treatment for patients with microbial keratitis, potentially without recourse to surgery, saving the sight of many in the developing world, where corneal transplantation may not be available.

An eye drop formulation that applies anti-scarring drugs to the surface of the eye helps reverse infection-induced corneal damage in mice. Hill et al. from the University of Birmingham, UK, formulated a fluid gel loaded with a wound-healing protein called decorin that conforms to the ocular surface and is cleared gradually through blinking. With colleagues in California, they applied the therapeutic eye drop to mice with bacterial eye infections that trigger sight-threatening corneal scarring. Within a matter of days, the team saw improvements in corneal transparency, with reductions in scar tissue and reconstitution of healthy cells. Such a drug delivery system, if successful in humans, could help save many people’s sight and reduce the need for corneal transplantation.

Accelerated Restoration of Ocular Surface Health in Dry Eye Disease by Self-Retained Cryopreserved Amniotic Membrane

PURPOSE

To evaluate the clinical efficacy of self-retained cryopreserved amniotic membrane in treating dry eye disease.

METHODS

Retrospective review of 10 patients treated with self-retained cryopreserved amniotic membrane (PROKERA® Slim [PKS], Bio-Tissue, Miami, FL) for moderate-to-severe dry eye refractory to conventional maximal medical treatments. Patients' symptoms, use of medications, conjunctival inflammation, corneal staining, and visual acuity were compared before and after treatment.

RESULTS

PKS was placed in 15 eyes of the 10 patients for 4.9 ± 1.5 days. All patients experienced symptomatic relief for a period of 4.2 ± 4.7 months (P<.001). Such improvement was accompanied by reduction of OSDI scores (P<.001), use of topical medications (P<.001), conjunctival hyperemia (P<.001), corneal staining (P<.001), and improvement of the visual acuity (P=.06). Linear regression analysis estimated that the optimal duration of PKS placement was 5 days to achieve an average symptom-free duration of 4 months in patients with dry eye. Surprisingly, PKS placement also generated improvement in the contralateral eyes.

CONCLUSION

This pilot study suggests that self-retained cryopreserved amniotic membrane via PKS can be used to treat moderate dry eye diseases and warrants further prospective controlled studies.