Augmented dried versus cryopreserved amniotic membrane as an ocular surface dressing

Bilateral Sutureless Application of Human Dehydrated Amniotic Membrane with a Specialised Bandage Contact Lens for Moderate-to-Severe Dry Eye Disease: A Prospective Study with 1-Month Follow-Up

Purpose

To assess changes in symptoms and ocular surface signs following a bilateral sutureless treatment of dehydrated amniotic membrane (dAM) under a specialised bandage contact lens (sBCL) in patients with moderate-to-severe dry eye disease (DED).

Patients and Methods

In this prospective pre-post interventional study, 35 patients diagnosed with moderate-to-severe DED, with an Ocular Surface Disease Index (OSDI) score >30 on current treatment, were enrolled. Assessments were conducted at baseline (day -30), after 30 days run-in with no additional treatment (day 0 - control), and 30 days post sBCL+dAM treatment (day 30 - treatment). Intervention involved two successive bilateral 4-5 day sutureless applications of dAM (17mm diameter, with a 6 mm central aperture, Omnigen® VIEW) under an 18mm sBCL (OmniLenz®). Symptomatology and ocular signs were measured using OSDI, Dry Eye Questionnaire-5 (DEQ-5), Symptom Assessment iN Dry Eye (SANDE), and other ocular surface health indicators including non-invasive breakup time, corneal and conjunctival staining, and lid wiper epitheliopathy length and width (LWE).

Results

While symptomatology remained stable during the 30-day no-treatment run-in, 1-month post-dAM treatment, there was a significant reduction in OSDI scores (from 55.8 to 32.3, p<0.001), DEQ-5 (from 14.6 to 10.0, p<0.001), SANDE frequency (from 65.2 to 43.6, p<0.001), and SANDE severity (from 59.8 to 41.1, p<0.001). Additionally, there was a notable decrease in the width of LWE staining, from grade 2 (50-75% of the lid wiper) to grade 1 (25-50% of the lid wiper) (p=0.011).

Conclusion

A bilateral 8-10-day treatment duration with dAM applied with sBCL demonstrated a 31 to 42% improvement in symptomatology and a decrease in ocular surface signs of mechanical stress. This innovative bilateral treatment approach offers a promising treatment modality for patients with refractory moderate-to-severe DED.

Silica nanoparticles enhance the cyto- and hemocompatibility of a multilayered extracellular matrix scaffold for vascular tissue regeneration

PURPOSE

The limited availability of autologous vessels for vascular bypass surgeries is a major roadblock to treating severe cardiovascular diseases. Based on this clinical priority, our group has developed a novel engineered vascular graft by rolling human amniotic membranes into multilayered extracellular matrixes (ECM). When treated with silica nanoparticles (SiNP), these rolled scaffolds showed a significant improvement in their structural and mechanical properties, matching those from gold standard autologous grafts. However, it remained to be determined how cells respond to SiNP-treated materials. As a first step toward understanding the biocompatibility of SiNP-dosed biomaterials, we aimed to assess how endothelial cells and blood components interact with SiNP-treated ECM scaffolds.

METHODS

To test this, we used established in vitro assays to study SiNP and SiNP-treated scaffolds' cyto and hemocompatibility.

RESULTS

Our results showed that SiNP effects on cells were concentration-dependent with no adverse effects observed up to 10 μg/ml of SiNP, with higher concentrations inducing cytotoxic and hemolytic responses. The SiNP also enhanced the scaffold's hydrophobicity state, a feature known to inhibit platelet and immune cell adhesion. Accordingly, SiNP-treated scaffolds were also shown to support endothelial cell growth while preventing platelet and leukocyte adhesion.

CONCLUSION

Our findings suggest that the addition of SiNP to human amniotic membrane extracellular matrixes improves the cyto- and hemocompatibility of rolled scaffolds and highlights this strategy as a robust mechanism to stabilize layered collagen scaffolds for vascular tissue regeneration.

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.

Amniotic membrane transplantation: structural and biological properties, tissue preparation, application and clinical indications

The amniotic membrane is a single epithelial layer of the placenta. It has anti-inflammatory, anti-scarring, anti-angiogenic and possibly bactericidal properties. The basement membrane of the amniotic membrane acts as a substrate to encourage healing and re-epithelialisation. It has been used in many ocular surface diseases including persistent epithelial defects (corneal or conjunctival), chemical or thermal burns, limbal stem cell deficiency, cicatrising conjunctivitis, ocular graft versus host disease, microbial keratitis, corneal perforation, bullous keratopathy, dry eye disease, corneal haze following refractive surgery and cross-linking, band keratopathy, ocular surface neoplasia, pterygium surgery, and ligneous conjunctivitis. This review provides an up-to-date overview of amniotic membrane transplantation including the structural and biological properties, preparation and application, clinical indications, and commercially available products.

INTRARETINAL HUMAN AMNIOTIC MEMBRANE AFTER MACULAR HOLE REPAIR

PURPOSE

To describe a unique complication of macular hole repair surgery using a subretinal human amniotic membrane plug.

METHODS

Retrospective, interventional case report.

RESULTS

A 71-year-old man presented with a chronic full-thickness macular hole in his left eye. Conventional 23-gauge pars plana vitrectomy with internal limiting membrane peeling and implantation of a subretinal human amniotic membrane plug was performed. In the postoperative period, centripetal growth of external retinal layers was observed under the plug. Six months after the surgery, the human amniotic membrane plug was completely integrated into the retina.

CONCLUSION

This is the first reported case of intraretinal integration of a human amniotic membrane plug after macular hole repair surgery.

Inter-placental variability is not a major factor affecting the healing efficiency of amniotic membrane when used for treating chronic non-healing wounds

This study aimed to evaluate the efficacy of cryopreserved amniotic membrane (AM) grafts in chronic wound healing, including the mean percentage of wound closure per one AM application, and to determine whether the healing efficiency differs between AM grafts obtained from different placentas. A retrospective study analyzing inter-placental differences in healing capacity and mean wound closure after the application of 96 AM grafts prepared from nine placentas. Only the placentas from which the AM grafts were applied to patients suffering from long-lasting non-healing wounds successfully healed by AM treatment were included. The data from the rapidly progressing wound-closure phase (p-phase) were analyzed. The mean efficiency for each placenta, expressed as an average of wound area reduction (%) seven days after the AM application (baseline, 100%), was calculated from at least 10 applications. No statistical difference between the nine placentas' efficiency was found in the progressive phase of wound healing. The 7-day average wound reduction in particular placentas varied from 5.70 to 20.99% (median from 1.07 to 17.75) of the baseline. The mean percentage of wound surface reduction of all analyzed defects one week after the application of cryopreserved AM graft was 12.17 ± 20.12% (average ± SD). No significant difference in healing capacity was observed between the nine placentas. The data suggest that if there are intra- and inter-placental differences in AM sheets' healing efficacy, they are overridden by the actual health status of the subject or even the status of its individual wounds.

[High energy proton therapy for extraocular tumors, neurotrophic keratitis and functional consequence: A series of 3 cases]

INTRODUCTION

High energy proton therapy (HEP) is a form of radiation therapy using protons for extraocular tumors. Its ballistic properties are theoretically advantageous, but the real impact on the surrounding ocular tissues during cerebral and ENT irradiation is poorly documented. We describe three consecutive patients with corneal damage following such irradiation.

MATERIALS/METHODS

Post-proton therapy neurotrophic keratitis (NK) is defined as corneal hypo/anesthesia responsible for an alteration of corneal trophicity and graded according to the Mackie classification, in terms of a prospective ophthalmological follow-up protocol for all patients with extraocular tumors treated with HEP.

RESULTS

Among 193 patients treated with HEP between 2018 and 2021 for extraocular tumors, three patients developed severe neurotrophic keratitis, i.e. 1.6% of treated patients. According to the Mackie classification, the three patients showed grade 3 NK less than one year after the conclusion of their HEP. These three patients underwent amniotic membrane grafting. They were placed on autologous serum eye drops. Two of the three patients had to be eviscerated. The dose to the cornea was greater than 50 Gray (Gy)_Relative biological effectiveness (RBE) in the three cases.

DISCUSSION

The diagnosis and etiological origin of neurotrophic keratitis are often difficult to establish. In these cases, the imputability of radiation therapy, proton therapy in our cases, in the development of neurotrophic keratitis was plausible based on the dosimetry of the patients, all of whom had anterior tumors with a poor prognosis requiring high tumoricidal doses.

CONCLUSION

Further studies to establish the impact of proton therapy on corneal sensitivity are necessary. However, this feedback and the multidisciplinary management of tumors can help to limit the risk of some complications of radiation therapy. Early diagnosis allows for appropriate management and could possibly minimize the anatomical and functional ocular complications of neurotrophic keratitis.

Quantification of Analgesic and Anti-Inflammatory Lipid Mediators in Long-Term Cryopreserved and Freeze-Dried Preserved Human Amniotic Membrane

The aim of this study was to compare concentrations of endogenous N-acylethanolamine (NAE) lipid mediators-palmitoylethanolamide (PEA), oleoylethanolamide (OEA), and anandamide (AEA)-in fresh, decontaminated, cryopreserved, and freeze-dried amniotic membrane (AM) allografts, thereby determining whether AM's analgesic and anti-inflammatory efficiency related to NAEs persists during storage. The concentrations of NAEs were measured using ultra-high-performance liquid chromatography-tandem mass spectrometry. Indirect fluorescent immunohistochemistry was used to detect the PEA PPAR-α receptor. The concentrations of PEA, OEA, and AEA were significantly higher after decontamination. A significant decrease was found in cryopreserved AM compared to decontaminated tissue for PEA but not for OEA and AEA. However, significantly higher values for all NAEs were detected in cryopreserved samples compared to fresh tissue before decontamination. The freeze-dried AM had similar values to decontaminated AM with no statistically significant difference. The nuclear staining of the PPAR-α receptor was clearly visible in all specimens. The stability of NAEs in AM after cryopreservation was demonstrated under tissue bank storage conditions. However, a significant decrease, but still higher concentration of PEA compared to fresh not decontaminated tissue, was found in cryopreserved, but not freeze-dried, AM. Results indicate that NAEs persist during storage in levels sufficient for the analgesic and anti-inflammatory effects. This means that cryopreserved AM allografts released for transplant purposes before the expected expiration (usually 3-5 years) will still show a strong analgesic effect. The same situation was confirmed for AM lyophilized after one year of storage. This work thus contributed to the clarification of the analgesic effect of NAEs in AM allografts.

Management of limbal stem cell deficiency by amnion-assisted conjunctival epithelial redirection using vacuum-dried amniotic membrane and fibrin glue

PURPOSE

To study the outcome of a modified amnion-assisted conjunctival epithelial redirection (ACER) technique using vacuum-dried amnion (Omnigen) and fibrin glue for managing total limbal stem cell deficiency (LSCD).

METHOD

A retrospective, interventional case series of all patients with total LSCD who underwent limbal stem cell transplant (LSCT) using the modified ACER procedure between 2016 and 2019. The outcome was defined as: (1) success: complete corneal re-epithelialisation without conjunctivalisation; (2) partial success: sub-total corneal re-epithelialisation with partial non-progressive conjunctivalisation sparing the visual axis and (3) failure: conjunctivalisation affecting the visual axis.

RESULTS

Ten patients (six men), with a mean age of 46.2±18.4 years, were included. The mean follow-up was 23.0±13.9 months. Causes of LSCD were chemical eye injury (30%), congenital aniridia-related keratopathy (30%), ocular surface malignancy (20%), Steven-Johnson syndrome (10%) and contact lens overuse (10%). 50% were bilateral. The time from diagnosis to ACER (for acquired causes) was 45.6±44.4 months. 80% of patients achieved a complete/partial success following ACER and 20% of patients required repeat LSCT. Auto-LSCT was associated with a significantly higher chance of success than allo-LSCT (p=0.048). The mean best-corrected-visual-acuity (logMAR) improved significantly from 1.76±0.64 preoperatively to 0.94±0.94 at final follow-up (p=0.009). Omnigen was available off-the-shelf stored at room temperature and its transparency enabled visualisation of the healing epithelium beneath.

CONCLUSION

LSCT using the modified ACER serves as an effective ocular surface reconstruction technique in managing total LSCD and improving vision. Vacuum-dried amnion provides advantages of easy handling, transparency and storage at room temperature.

The developments in amniotic membrane transplantation in glaucoma and vitreoretinal procedures

The main reasons why Amniotic Membrane (AM) is transplanted in Ophthalmology are: to provide a substrate for cellular growth and to provide tectonic support or as a biological bandage and barrier that protects the wound to facilitate an environment for wound healing. The application of AM is well-documented in corneal disorders of various aetiologies [1], however, research within the field has highlighted how it can be used in conjunctival disorders and most recently, in glaucoma and vitreoretinal procedures. This review explores the preservation modalities of AM and summarises the current literature regarding AM transplantation in Glaucoma and Vitreoretinal conditions. AM transplantation in conjunction with trabeculectomy was reported to be used in two different surgical techniques. They differ in relation to the position of the implant: below the scleral flap or over the entire exposed sclera. The results of these studies suggest that AM transplant is a safe procedure that helps in the improvement of the intraocular pressure when associated with trabeculectomies. Moreover, it enhances trabeculectomies success rates when used along with mitomycin C [2]. The use of AM is also described for managing leaking blebs. It is mentioned to be a suitable alternative to conjunctival advancement. Regarding AM transplantation in glaucoma shunt or valve surgeries, the current literature is relatively limited. However, AM has been described as a good tectonic support for shunt procedures [3]. Successful results are described in the literature for surgical treatments using AM plug for vitreoretinal procedures. In particular macular hole closure and rhegmatogenous retinal detachment. In conclusion, AM transplant is a very promising and versatile adjutant therapy. However, further studies are also required for a better understanding and refinement of surgical techniques.

Transcriptomic Landscape and Functional Characterization of Human Induced Pluripotent Stem Cell-Derived Limbal Epithelial Progenitor Cells

Limbal stem cell deficiency (LSCD) is a complex, multifactorial disease affecting limbal epithelial progenitor cells (LEPC), which are essential for maintaining corneal stability and transparency. Human induced pluripotent stem cell-derived (hiPSC-) LEPC are a promising cell source for the treatment of LSCD. However, their similarity to native tissue-derived (T-) LEPC and their functional characterization has not been studied in detail. Here, we show that hiPSC-LEPC and T-LEPC have rather similar gene expression patterns, colony-forming ability, wound-healing capacity, and melanosome uptake. In addition, hiPSC-LEPC exhibited lower immunogenicity and reduced the proliferation of peripheral blood mononuclear cells compared with T-LEPC. Similarly, the hiPSC-LEPC secretome reduced the proliferation of vascular endothelial cells more than the T-LEPC secretome. Moreover, hiPSC-LEPC successfully repopulated decellularized human corneolimbal (DHC/L) scaffolds with multilayered epithelium, while basal deposition of fibrillary material was observed. These findings suggest that hiPSC-LEPC exhibited functional properties close to native LEPC and that hiPSC-LEPC-DHC/L scaffolds might be feasible for transplantation in patients suffering from LSCD in the future. Although hiPSC-LEPC-based stem cell therapy is promising, the current study also revealed new challenges, such as abnormal extracellular matrix deposition, that need to be overcome before hiPSC-LEPC-based stem cell therapies are viable.

Surgical Management of Peripheral Ulcerative Keratitis: Update on Surgical Techniques and Their Outcome

Peripheral ulcerative keratitis (PUK) is an inflammatory, necrotic condition in the peripheral cornea which may end in corneal perforation and visual morbidity if not treated adequately. PUK can occur due to infectious or non-infectious causes. Early cases need medical therapy, both locally and systemically (for some cases). However, advanced PUK may necessitate surgical removal of inciting cause of the pathology and maintaining tectonic stability. Such surgical treatment, including corneal transplantations, may be used in an emergency setting or for visual rehabilitation following preliminary stabilization of the affected cornea. The outcome of these surgeries need to be analyzed to understand the long-term visual prognosis of such eyes. This is an attempt to analyze surgical modalities in the management of PUK and their outcomes.

Healing of a chronic ulcer of the lower limb of venous origin with fresh human amniochorionic membrane allograft

In its fresh state, the amniochorionic membrane contains various multipotential cells, growth factors, and extracellular matrix proteins that contribute to the healing of chronic vascular ulcers. To demonstrate its effectiveness, a fresh human placental membrane allograft was applied to a chronic venous ulcer in the lower limb of an 89-year-old female patient with a 12 x 10 cm ulcerated lesion of 40 years of evolution in the malleolar area of her left lower limb. Sixty days after the graft, the ulcer was healed in 100% of its surface and a light pink scar on the edges indicated possible pigmentation. Fresh human amniochorionic membrane allograft is a therapeutic alternative for the healing of refractory chronic vascular ulcers of the lower extremities.

Pilot study of a glue-less, suture-less amniotic membrane for pterygium excision

PURPOSE

Pterygium is a non-cancerous, fibrovascular growth of the bulbar conjunctiva that can cause visual disturbance, ocular pain, and cosmetic concerns. Surgical management is required in certain cases, which consists of excising the pterygium and associated Tenon's, then overlaying the bare sclera with an autograft or amniotic membrane using glue or sutures. The purpose of this study is to assess outcomes of pterygium repair using a newly developed self-adhesive amniotic membrane that does not require glue or sutures for fixation.

METHODS

Chart review of pterygium excision using a new self-adhesive amniotic membrane from a single surgical practice from 2012-2018. Descriptive statistics from 51 primary cases of pterygium excision were included.

RESULTS

Pterygium recurrence occurred in 3 of the 51 self-adhesive amniotic membrane cases studied, resulting in a recurrence rate of 5.9%. Pterygium excision with the self-adhesive amniotic membrane had high rate of pyogenic granuloma formation of 27%. Self-adhesive amniotic membranes were found to perform comparably to more widely used techniques for pterygium excision, namely amniotic membranes and conjunctival autographs with glue or sutures. However, the self-adhesive grafts are associated with substantially more pyogenic granuloma formation.

CONCLUSION

Self-adhesive amniotic membranes offer comparable efficacy for preventing pterygium recurrence in comparison to other amniotic membranes and the conjunctival autograft. The incidence of pyogenic granuloma formation is higher in self-adhesive grafts compared to other widely used options.

Epiretinal large disc of blue-stained lyophilized amniotic membrane to treat complex macular holes: a 1-year follow-up

PURPOSE

To report the long-term outcomes of large diameter epiretinal lyophilized amniotic membranes (lAMs) in recurrent or persistent macular holes (MHs) with or without rhegmatogenous retinal detachment (RRD), in a prospective interventional case series.

METHODS

Ten eyes of 10 patients underwent pars plana vitrectomy for MH-associated RRD (n = 5) or persistent MH without RRD (n = 5), in a university Hospital. A 3 or 4 mm diameter disc of lAM, stained with 0.06% trypan blue, was inserted with a catheter through a sclerotomy and positioned over the MH. Gas or silicone-oil tamponade was used. At 1 year, the main outcome was anatomic success defined as complete MH closure. Secondary outcomes were best corrected visual acuity (BCVA) recovery, changes in ellipsoid zone (EZ) and external limiting membrane (ELM) defects, complications. Mean follow-up was 13.8 ± 2.9 months (range, 12-18).

RESULTS

Mean baseline data were minimum and maximum diameters, respectively, 945 ± 330 and 1507 ± 717 μm; axial length 26.58 ± 3.38 mm; and number of prior surgeries 1.4 ± 0.96. At 1 year, anatomic success was achieved in eight eyes (80%), and two had reduced diameter of MH. All RRDs were reattached without recurrence. Mean logMAR BCVA improved from 1.92 ± 0.58 to 1.17 ± 0.57 (p < 0.001), with nine eyes (90%) achieving ≥0.3 logMAR improvement. Mean EZ and ELM defects decreased (p = 0.004, p = 0.003, respectively). Postoperative complications were RRD (n = 1) reattached by subsequent surgery, lAM slightly retracted under silicone (n = 1), foveal atrophy after early lAM displacement (n = 1).

CONCLUSION

A 1-year follow-up highlighted that epiretinal large discs of blue-stained lAM can help safely close refractory MHs, and provide satisfactory visual recovery.

Human Acellular Amniotic Matrix with Previously Seeded Umbilical Cord Mesenchymal Stem Cells Restores Endometrial Function in a Rat Model of Injury

Background

Abnormal endometrial repair after injury results in the formation of intrauterine adhesions (IUA) and a thin endometrium, which are key causes for implantation failure and infertility. Stem cell transplantation offers a potential alternative for some cases of severe Asherman's syndrome that cannot be treated with surgery or hormonal therapy. Umbilical cord-derived mesenchymal stem cells (UCMSCs) have been reported to repair the damaged endometrium. However, there is no report on the effects of UCMSCs previously seeded on human acellular amniotic matrix (AAM) on endometrial injury.

Methods

Absolute ethanol was injected into rat uteri to damage the endometrium. UCMSCs previously seeded on AAM were surgically transplanted. Using a variety of methods, the treatment response was assessed by endometrial thickness, endometrial biomarker expression, endometrial receptivity, cell proliferation, and inflammatory factors.

Results

Endometrial thickness was markedly improved after UCMSC-AAM transplantation. The expression of endometrial biomarkers, namely, vimentin, cytokeratin, and integrin β3, in treated rats increased compared with untreated rats. In the UCMSC-AAM group, the VEGF expression decreased, whereas that of MMP9 increased compared with the injury group. Moreover, in the AAM group, the MMP9 expression increased. The expression of proinflammatory factors (IL-2, TNFα, and IFN-γ) in the UCMSC-AAM group decreased compared with the untreated group, whereas the expression of anti-inflammatory factors (IL-4, IL-10) increased significantly.

Conclusions

UCMSC transplantation using AAM as the carrier can be applied to treat endometrial injury in rats. The successful preparation of lyophilized AAM provides the possibility of secondary infectious disease screening and amniotic matrix quality detection, followed by retrospective analysis. The UCMSC-AAM complex may promote the better application of UCMSCs on the treatment of injured endometrium.

Corneal Epithelial Stem Cells-Physiology, Pathophysiology and Therapeutic Options

In the human cornea, regeneration of the epithelium is regulated by the stem cell reservoir of the limbus, which is the marginal region of the cornea representing the anatomical and functional border between the corneal and conjunctival epithelium. In support of this concept, extensive limbal damage, e.g., by chemical or thermal injury, inflammation, or surgery, may induce limbal stem cell deficiency (LSCD) leading to vascularization and opacification of the cornea and eventually vision loss. These acquired forms of limbal stem cell deficiency may occur uni- or bilaterally, which is important for the choice of treatment. Moreover, a variety of inherited diseases, such as congenital aniridia or dyskeratosis congenita, are characterized by LSCD typically occurring bilaterally. Several techniques of autologous and allogenic stem cell transplantation have been established. The limbus can be restored by transplantation of whole limbal grafts, small limbal biopsies or by ex vivo-expanded limbal cells. In this review, the physiology of the corneal epithelium, the pathophysiology of LSCD, and the therapeutic options will be presented.

Experimental evaluation of safety and efficacy of plasma-treated poly-ε-caprolactone membrane as a substitute for human amniotic membrane in treating corneal epithelial defects in rabbit eyes

Purpose:

To evaluate biocompatibility and safety of plasma-treated poly-ε-caprolactone (pPCL) membrane compared to the human amniotic membrane in the healing of corneal epithelial defects in an experimental model.

Methods:

This is a prospective, randomized animal study including 12 rabbits. Circular epithelial injury measuring 6 mm in diameter was induced over the central cornea of one eye in twelve rabbits. The rabbits were randomized into two groups; in group A, the defect was covered with human amniotic membrane, while in group B, an artificial membrane made of bio-polymer plasma-treated poly-ε-caprolactone was grafted. Six rabbits were euthanized after 1 month and the other six after 3 months and the corneal epithelium was evaluated histopathologically and with immunohistochemistry.

Results:

Light microscopy of the corneal tissue performed after 1 month and 3 months demonstrated similar findings with no significant complications in either group. Immunohistochemistry with anti-CK-3 antibody showed characteristic corneal phenotype in the healed epithelium. In eyes grafted with pPCL membrane, epithelial healing as estimated by a decrease in size of the defect was significantly better than the group treated with the human amniotic membrane at all time periods monitored (P < 0.05), except day 1 (P = 0.83). The percentage reduction in the size of the epithelial defect was also significantly more in the pPCL membrane group as compared to the human amniotic membrane at all time periods (P < 0.05 at all observations) post-implantation except day 1 (P = 0.73).

Conclusion:

Plasma-treated poly-ε-caprolactone membrane is safe, biocompatible, and effective in the healing of corneal epithelial defects in rabbits.

Bio-Fabrication of Human Amniotic Membrane Zinc Oxide Nanoparticles and the Wet/Dry HAM Dressing Membrane for Wound Healing

The preparation of unique wet and dry wound dressing products derived from unprocessed human amniotic membrane (UP-HAM) is described. The UP-HAM was decellularized, and the constituent proteins were cross-linked and stabilized before being trimmed and packed in sterile Nucril-coated laminated aluminium foil pouches with isopropyl alcohol to manufacture processed wet human amniotic membrane (PW-HAM). The dry type of PD-HAM was prepared by decellularizing the membrane, UV irradiating it, lyophilizing/freeze-drying it, sterilizing it, and storing it at room temperature. The UP-HAM consists of a translucent yellowish mass of flexible membranes with an average thickness of 42 μm. PW-HAM wound dressings that had been processed, decellularized, and dehydrated had a thinner average thickness of 30 μm and lacked nuclear-cellular structures. Following successful decellularization, discrete bundle of fibrous components in the stromal spongy layers, microvilli and reticular ridges were still evident on the surface of the processed HAM, possibly representing the location of the cells that had been removed by the decellularization process. Both wet and dry HAM wound dressings are durable, portable, have a shelf life of 3–5 years, and are available all year. A slice of HAM dressing costs 1.0 US$/cm². Automation and large-scale HAM membrane preparation, as well as storage and transportation of the dressings, can all help to establish advanced technologies, improve the efficiency of membrane production, and reduce costs. Successful treatment of wounds to the cornea of the eye was achieved with the application of the HAM wound dressings. The HAM protein analysis revealed 360 μg proteins per gram of tissue, divided into three main fractions with MWs of 100 kDa, 70 kDa, and 14 kDa, as well as seven minor proteins, with the 14 kDa protein displaying antibacterial properties against human pathogenic bacteria. A wide range of antibacterial activity was observed after treatment with 75 μg/ml zinc oxide nanoparticles derived from human amniotic membrane proteins (HAMP-ZnO NP), including dose-dependent biofilm inhibition and inhibition of Gram-positive (S. aureus, S. mutans, E. faecalis, and L. fusiformis) and Gram-negative bacteria (S. sonnei, P. aeruginosa, P. vulgaris, and C. freundii).

Freeze-Dried Versus Cryopreserved Amniotic Membranes in Corneal Ulcers Treated by Overlay Transplantation: A Case-Control Study

PURPOSE

The purpose of this study was to assess cryopreserved amniotic membrane (C-AM) versus chorion-free freeze-dried amniotic membrane (FD-AM) overlay transplantation for corneal ulcers in a French tertiary ophthalmology hospital.

METHODS

Between March and July 2020, when C-AMs were not available because of the COVID-19 pandemic, 28 corneal ulcers underwent FD-AM overlay transplantation and were retrospectively compared with 22 corneal ulcers treated with C-AM during the same period in 2018. All patients had at least 3 months of follow-up, and those who underwent combined surgeries were excluded. Ulcers were assessed at baseline and then at 72 hours, 1 month, and 3 months. Population demographics, follow-up time, ulcer etiologies, epithelial defect size, ulcer depth, and complications were also recorded.

RESULTS

Baseline characteristics and clinical features of both groups were comparable. There was no statistically significant difference in the number of overlay AM transplantations (P = 0.52) or early detachments (P = 0.57). At 3 months, the corneal healing rate was almost the same in both groups (89% and 91% for FD-AM and C-AM, respectively; P = 0.87). Complications were equally uncommon (11% and 9%, respectively; P = 0.92). In logistic regression, the type of the membrane did not influence corneal healing at 1 month (P = 0.42) or 3 months (P = 0.99), regardless of the depth of the ulcer. However, whatever the type of AM used, the deeper the ulcer was, the less likely it was to heal at 3 months (P = 0.02).

CONCLUSIONS

This is the first study that provides positive insight into the effectiveness of FD-AM compared with C-AM when used as overlay transplantation for treating corneal ulcers.

Amniotic membrane transplantation for infectious keratitis: a systematic review and meta-analysis

Infectious keratitis (IK) is the 5th leading cause of blindness globally. Broad-spectrum topical antimicrobial treatment is the current mainstay of treatment for IK, though adjuvant treatment or surgeries are often required in refractory cases of IK. This systematic review aimed to examine the effectiveness and safety of adjuvant amniotic membrane transplantation (AMT) for treating IK. Electronic databases, including MEDLINE, EMBASE and Cochrane Central, were searched for relevant articles. All clinical studies, including randomized controlled trials (RCTs), non-randomized controlled studies and case series (n > 5), were included. Primary outcome measure was time to complete corneal healing and secondary outcome measures included corrected-distance-visual-acuity (CDVA), uncorrected-distance-visual-acuity (UDVA), corneal vascularization and adverse events. A total of twenty-eight studies (including four RCTs) with 861 eyes were included. When compared to standard antimicrobial treatment alone, adjuvant AMT resulted in shorter mean time to complete corneal healing (− 4.08 days; 95% CI − 6.27 to − 1.88; p < 0.001) and better UDVA (− 0.26 logMAR; − 0.50 to − 0.02; p = 0.04) at 1 month follow-up in moderate-to-severe bacterial and fungal keratitis, with no significant difference in the risk of adverse events (risk ratio 0.80; 0.46–1.38; p = 0.42). One RCT demonstrated that adjuvant AMT resulted in better CDVA and less corneal vascularization at 6 months follow-up (both p < 0.001). None of the RCTs examined the use of adjuvant AMT in herpetic or Acanthamoeba keratitis, though the benefit was supported by a number of case series. In conclusion, AMT serves as a useful adjuvant therapy in improving corneal healing and visual outcome in bacterial and fungal keratitis (low-quality evidence). Further adequately powered, high-quality RCTs are required to ascertain its therapeutic potential, particularly for herpetic and Acanthamoeba keratitis. Future standardization of the core outcome set in IK-related trials would be invaluable.

Management of Persistent Corneal Epithelial Defects with Human Amniotic Membrane-derived Dry Matrix

Objective

To report the outcomes of using human amniotic membrane-derived dry matrix (AMDDM) in the management of persistent corneal epithelial defects (PEDs) of various etiologies.

Methods

A cohort study of 84 patients age range 7 to 92 years with 93 PEDs were treated with AMDDM (Omnigen^® using OmniLenz^® at two centers (Queen Victoria Hospital and Maidstone Hospital) in the UK. The main outcome measures were healing response of PED and time to heal after application of AMDDM.

Results

A total of 106 applications of AMDDM were recorded for 81 patients (52 males, 29 females) with a spectrum of different etiologies. Fifty-eight percent of the eyes showed complete healing, and 28% showed partial decrease of the size of PEDs with average treatment length recorded as 22.4±12.3 days. In patients with limbal stem cell deficiency (n=44; aniridia=12, chemical injury=9, Stevens–Johnson syndrome=10), 50% of PEDs showed complete healing and 27% showed partial healing. In patients with microbial keratitis (n=21) (bacterial: 13, fungal: 4, herpetic: 3, acanthamoeba: 1) 57% of PEDs showed complete healing and 33% were partially healed. In patients with keratoplasty (n=16), 56% of PEDs showed complete healing and 31% were partially healed. Vision remained stable in 59% and improved in 27% of the study the population.

Conclusion

AMDDM can be easily applied in the clinical setting and has demonstrated its efficiency as a new tool to treat persistent epithelial defects.

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.

Biomechanical Modulation Therapy-A Stem Cell Therapy Without Stem Cells for the Treatment of Severe Ocular Burns

Ocular injuries caused by chemical and thermal burns are often unmanageable and frequently result in disfigurement, corneal haze/opacification, and vision loss. Currently, a considerable number of surgical and pharmacological approaches are available to treat such injuries at either an acute or a chronic stage. However, these existing interventions are mainly directed at (and limited to) suppressing corneal inflammation and neovascularization while promoting re-epithelialization. Reconstruction of the ocular surface represents a suitable but last-option recourse in cases where epithelial healing is severely impaired, such as due to limbal stem cell deficiency. In this concise review, we discuss how biomechanical modulation therapy (BMT) may represent a more effective approach to promoting the regeneration of ocular tissues affected by burn injuries via restoration of the limbal stem cell niche. Specifically, the scientific basis supporting this new therapeutic modality is described, along with our growing understanding of the role that tissue biomechanics plays in stem cell fate and function. The potential impact of BMT as a future treatment option for the management of injuries affecting tissue compliance is also further discussed.

Case Series Describing the Use of Low-Temperature Vacuum-Dehydrated Amnion (Omnigen) for the Treatment of Corneal Ulcers in Cats and Dogs: 46 Cases (2016-2017)

Amniotic membrane is widely used in the treatment of ocular surface disorders in human and veterinary patients. Preservation and storage of amnion has proven challenging, prompting the development of new preservation techniques. Omnigen, a novel low-temperature vacuum-dehydrated amnion, is reported to possess enhanced structural properties and biochemical stability in vitro, but its clinical use in veterinary patients is not well described. This study aims to document and describe the varied use of Omnigen for the surgical treatment of corneal ulceration in cats and dogs. A total of 45 patients (46 eyes) were recruited from the clinical record system of the Royal Veterinary College (London) between January 2016 and December 2017. Brachycephalic breeds were over-represented (37/45; 82.2%). Omnigen was used as a standalone graft in 5/46 (10.9%) eyes, as a supplementary graft in 29/46 (63.0%) eyes and as a patch in 12/46 (26.1%) eyes. Graft failure occurred in 10/46 eyes (21.7%). At final examination 43/46 eyes (93.5%) had healed and 31/33 eyes (93.9%) were visual. This study demonstrates the successful use of Omnigen for the surgical treatment of corneal ulceration in cats and dogs. Further studies are needed to clarify its properties and benefits in the clinical field.

Amniotic membrane allografts maintain key biological properties post SCCO2 and lyophilization processing

Amniotic membrane (AM) has been shown to enhance corneal wound healing due to the abundance of growth factors, cytokines, and extracellular matrix (ECM) proteins inherent to the tissue. As such, AM has garnered widespread clinical utility as a biological dressing for a number of ophthalmic and soft tissue applications. The preparation, sterilization, and storage procedures used to manufacture AM grafts are extremely important for the conservation of inherent biological components within the membrane. Current processing techniques use harsh chemicals and sterilization agents that can compromise the fundamental wound healing properties of AM. Furthermore, commercially available cryopreserved AM products require specific storage conditions (e.g., ultra-low freezers) thereby limiting their clinical availability in austere environments. Supercritical carbon dioxide (SCCO₂) technology allows for the sterilization of biological tissues without the resulting degradation of integral ECM proteins and other factors often seen with current tissue sterilization processes. With this study we demonstrate that lyophilized AM, sterilized using SCCO₂, maintains similar biochemical properties and biocompatibility as that of commercially available AM products requiring specialized cold storage conditions.

Amniotic Membrane Transplantation in Ophthalmology: An Updated Perspective

Aim

The aim of this paper is to provide a succinct literature review of the different clinical applications for AMT usage in an ophthalmic setting, ranging from commonly used applications to less mainstream approaches. The hope is that this review enables the reader to have a better understanding of the biological properties of amnion as well as the indications and scenarios in which AMT can be used, whilst presenting relevant evidence from within the literature which may be of interest. We also provide an update on the methods of preservation of amniotic membrane and the application methodologies.

Methods

Literature search. A PubMed search was performed using the search terms “amniotic membrane transplant”, “amnion AND cornea”, amnion AND ophthalmology”, “amnion AND ocular surface” and “Amnion AND eye”. A full review of the literature using the PubMed database was conducted up until 01/05/20. The articles used were written in English, with all articles accessed in full. Both review articles and original articles were used for this review. All full publications related to ophthalmology were considered.

Non-toxic freezing media to retain the stem cell reserves in adipose tissues

Subcutaneous adipose tissue is a rich source of stromal vascular fraction (SVF) and adipose-derived stromal/stem cells (ASCs) that are inherently multipotent and exhibit regenerative properties. In current practice, lipoaspirate specimens harvested from liposuction surgeries are routinely discarded as a biohazard waste due to a lack of simple, cost effective, and validated cryopreservation protocols. The aim of this study is to develop a xenoprotein-free cryoprotective agent cocktail that will allow for short-term (up to 6 months) preservation of lipoaspirate tissues suitable for fat grafting and/or stromal/stem cell isolation when stored at achievable temperatures (-20 °C or -80 °C). Lipoaspirates donated by three consenting healthy donors undergoing elective cosmetic liposuction surgeries were suspended in five freezing media (FM1: 10% DMSO and 35% BSA; FM2: 2% DMSO and 43% BSA; FM3: 10% DMSO and 35% lipoaspirate saline; FM4: 2% DMSO and 6% HSA; and FM5: 40% lipoaspirate saline and 10% PVP) all suspended in 1X DMEM/F12 and frozen using commercially available freezers (-20 °C or -80 °C) and stored at least for a 1 month. After 1 month of freezing storage, SVF cells and ASCs were isolated from the frozen-thawed lipoaspirates by digestion with collagenase type I. Cell viability was evaluated by fluorescence microscopy after staining with acridine orange and ethidium bromide. The SVF isolated from lipoaspirates frozen at -80 °C retained comparable cell viability with the tested freezing media (FM2, FM3, FM4) comparable with the conventional DMSO and animal serum media (FM1), whereas the FM5 media resulted in lower viability. In contrast, tissues frozen and stored at -20 °C did not yield live SVF cells after thawing and collagenase digestion. The surface marker expression (CD90, CD29, CD34, CD146, CD31, and CD45) of ASCs from frozen lipoaspirates at -80 °C in different cryoprotectant media were also evaluated and no significant differences were found between the groups. The adipogenic and osteogenic differentiation potential were studied by histochemical staining and gene expression by qRT-PCR. Oil Red O staining for adipogenesis revealed that the CPA media FM1, FM4 and FM5 displayed robust differentiation. Alizarin Red S staining for osteogenesis revealed that FM1 and FM4 media displayed superior differentiation in comparison to other tested media. Measurement of adipogenic and osteogenic gene expression by qRT-PCR provided similar outcomes and indicated that FM4 CPA media comparable with FM1 for adipogenesis and osteogenesis.

Engineering a Corneal Stromal Equivalent Using a Novel Multilayered Fabrication Assembly Technique

To overcome the serious shortage of donor corneas for transplantation, alternatives based on tissue engineering need to be developed. Decellularized corneas are one potential alternative, but their densely packed collagen architecture inhibits recellularization in vitro. Therefore, a new rapid method of recellularizing these constructs to ensure high cellularity throughout the collagen scaffold is needed. In this study, we developed a novel method for fabricating corneal constructs by using decellularized porcine corneal sheets assembled using a bottom-up approach by layering multiple sheets between cell-laden collagen I hydrogel.

Corneal lenticules were cut from porcine corneas by cryosectioning, then decellularized with detergents and air-dried for storage as sheets. Human corneal stromal cells were encapsulated in collagen I hydrogel and cast between the dried sheets. Constructs were cultured in serum-free medium supplemented with ascorbic acid and insulin for 2 weeks. Epithelial cells were then seeded on the surface and cultured for an additional week. Transparency, cell viability, and phenotype were analyzed by qPCR, histology, and immunofluorescence. Constructs without epithelial cells were sutured onto an ex vivo porcine cornea and cultured for 1 week.

Lenticules were successfully decellularized, achieving dsDNA values of 13 ± 1.2 ng/mg dry tissue, and were more resistant to degradation than the collagen I hydrogels. Constructs maintained high cell viability with a keratocyte-like phenotype with upregulation of keratocan, decorin, lumican, collagen I, ALDH3A1, and CD34 and the corneal epithelial cells stratified with a cobblestone morphology. The construct was amenable to surgical handling and no tearing occurred during suturing. After 7 days ex vivo, constructs were covered by a neoepithelium from the host porcine cells and integration into the host stroma was observed.

This study describes a novel approach toward fabricating anterior corneal substitutes in a simple and rapid manner, obtaining mature and suturable constructs using only tissue-derived materials.

Repeated Freezing Procedures Preserve Structural and Functional Properties of Amniotic Membrane for Application in Ophthalmology

For decades, the unique regenerative properties of the human amniotic membrane (hAM) have been successfully utilized in ophthalmology. As a directly applied biomaterial, the hAM should be available in a ready to use manner in clinical settings. However, an extended period of time is obligatory for performing quality and safety tests. Hence, the low temperature storage of the hAM is a virtually inevitable step in the chain from donor retrieval to patient application. At the same time, the impact of subzero temperatures carries an increased risk of irreversible alterations of the structure and composition of biological objects. In the present study, we performed a comprehensive analysis of the hAM as a medicinal product; this is intended for a novel strategy of application in ophthalmology requiring a GMP production protocol including double freezing–thawing cycles. We compared clinically relevant parameters, such as levels of growth factors and extracellular matrix proteins content, morphology, ultrastructure and mechanical properties, before and after one and two freezing cycles. It was found that epidermal growth factor (EGF), transforming growth factor beta 1 (TGF-β1), hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), hyaluronic acid, and laminin could be detected in all studied conditions without significant differences. Additionally, histological and ultrastructure analysis, as well as transparency and mechanical tests, demonstrated that properties of the hAM required to support therapeutic efficacy in ophthalmology are not impaired by dual freezing.

Preparation of Dried Amniotic Membrane for Corneal Repair

Amniotic membrane transplantation is an established therapeutic and biological adjunct for several clinical situations, including treatment of diabetic foot ulcers and ocular surface disease. However, poorly standardized and validated clinical preparation and storage procedures can render the final product highly variable and an unpredictable biomaterial. We have therefore developed a novel, standardized method for processing and dry-preserving amniotic membrane, minimizing biochemical, compositional, and structure damage to produce a potentially superior membrane suitable for clinical use. The intellectual property associated with this methodology was patented by the University of Nottingham and licensed to NuVision^® Biotherapies which formed the basis of the Tereo^® manufacturing process which is used to manufacture Omnigen^®.

Effect of glycerol concentrations and temperatures on epidermal growth factor protein expression in preserved canine amniotic membrane

Amniotic membrane has been widely applied as a biological graft in both medical and veterinary practice. In ophthalmology, epidermal growth factor (EGF) in human amniotic membrane (HAM) promotes corneal epithelial cell proliferation and migration, thus it facilitates corneal wound healing. In dogs, with limited cryopreserved HAM availability, different cold glycerol preserving protocols have been developed for the storage canine amniotic membrane (CAM). This study aimed to study protein expression of EGF in CAM preserved with different concentrations of glycerol and storage temperatures, using enzyme-linked immunosorbent assay. CAM preserved in 50% glycerol and 99.5% glycerol and kept at 4 and - 20 °C for 7-30 days were compared. We found that preserving membrane with 50% glycerol at - 20 °C has significantly higher EGF protein expression compared with that at 4 °C (p < 0.05). There was a trend that the storage in 50% glycerol achieved higher EGF protein expression than 99.5% glycerol at both 4 °C and - 20 °C. In conclusion, 50% glycerol at - 20 °C was the best condition to preserve CAM in our study. Therefore, there is likely an alternative method to maintain level of EGF protein expression in preserved CAM.

A cellular and proteomic approach to assess proteins extracted from cryopreserved human amnion in the cultivation of corneal stromal keratocytes for stromal cell therapy

Background

Human corneal stromal keratocytes propagated in culture media supplemented with human amnion extract (AME) can correct early corneal haze in an animal model. Clinical application of cultivated keratocytes is limited by infectious disease screening before amnion products can be used in humans. It remains unclear if AME from cryopreserved versus fresh human amnion can support human keratocyte propagation, and which components of the extract promote keratocyte growth.

Methods

Three placentas were collected for the preparation of fresh and cryopreserved amnion tissues followed by homogenization and protein extraction. AME protein profiles were studied using isobaric tagging for relative and absolute quantitation (iTRAQ) proteomics. Enriched gene ontology (GO) terms and functional classes were identified. Primary human keratocytes from 4 donor corneas were cultured in media supplemented with fresh AME (F-AME) or cryopreserved AME (C-AME). Cell viability, proliferation and keratocyte marker expression were examined by confocal immunofluorescence and flow cytometry.

Results

AME proteomics revealed 1385 proteins with similar expression levels (between 0.5- and 2-fold) between F- and C-AME, while 286 proteins were reduced (less than 0.5-fold) in C-AME. Enriched GO term and biological pathway analysis showed that those proteins with comparable expression between F-AME and C-AME were involved in cell metabolism, epithelial-mesenchymal transition, focal adhesion, cell-extracellular matrix interaction, cell stress regulation and complement cascades. Human corneal stromal keratocytes cultured with F-AME or C-AME showed similar morphology and viability, while cell proliferation was mildly suppressed with C-AME (P > 0.05). Expression of aldehyde dehydrogenase 3A1 (ALDH3A1) and CD34 was similar in both cultures.

Conclusion

AME from cryopreserved amnion had limited influence on keratocyte culture. It is feasible to use protein extract from cryopreserved amnion to propagate human keratocytes for potential translational applications.

Nanofiber-reinforced decellularized amniotic membrane improves limbal stem cell transplantation in a rabbit model of corneal epithelial defect

Human amniotic membrane (AM) offers unique advantages as a matrix to support the transplantation of limbal stem cells (LSCs) due to its inherent pro-regenerative and anti-inflammatory properties. However, the widespread use of AM in clinical treatments of ocular surface disorders is limited by its weak mechanical strength and fast degradation, and high cost associated with preserving freshly isolated AM. Here we constructed a composite membrane consisting of an electrospun bioabsorbable poly(ε-caprolactone) (PCL) nanofiber mesh to significantly improve the ultimate tensile strength, toughness, and suture retention strength by 4-10-fold in comparison with decellularized AM sheet. The composite membrane showed extended stability and conferred longer-lasting coverage on wounded cornea surface compared with dAM. The composite membrane maintained the pro-regenerative and immunomodulatory properties of dAM, promoted LSC survival, retention, and organization, improved re-epithelialization of the defect area, and reduced inflammation and neovascularization. This study demonstrates the translational potential of our composite membrane for stem cell-based treatment of ocular surface damage. STATEMENT OF SIGNIFICANCE: Human decellularized amniotic membrane (dAM) has been widely shown as a biodegradable and bioactive matrix for regenerative tissue repair. However, the weak mechanical property has limited its widespread use in the clinic. Here we constructed a composite membrane using a layer of electrospun poly(ε-caprolactone) (PCL) nanofiber mesh to reinforce the dAM sheet through covalent interfacial bonding, while retaining the unique bioactivity of dAM. In a rabbit model of limbal stem cell (LSC) deficiency induced by alkaline burn, we demonstrated the superior property of this PCL-dAM composite membrane for repairing damaged cornea through promoting LSC transplantation, improving re-epithelialization, and reducing inflammation and neovascularization. This new composite membrane offers great translational potential in supporting stem cell-based treatment of ocular surface damage.

Validation and assessment of an antibiotic-based, aseptic decontamination manufacturing protocol for therapeutic, vacuum-dried human amniotic membrane

Amniotic membrane (AM) is used to treat a range of ophthalmic indications but must be presented in a non-contaminated state. AM from elective caesarean sections contains natural microbial contamination, requiring removal during processing protocols. The aim of this study was to assess the ability of antibiotic decontamination of AM, during processing by innovative low-temperature vacuum-drying. Bioburden of caesarean section AM was assessed, and found to be present in low levels. Subsequently, the process for producing vacuum-dried AM (VDAM) was assessed for decontamination ability, by artificially loading with Staphylococcus epidermidis at different stages of processing. The protocol was highly efficient at removing bioburden introduced at any stage of processing, with antibiotic treatment and drying the most efficacious steps. The antibacterial activity of non-antibiotic treated AM compared to VDAM was evaluated using minimum inhibitory/biocidal concentrations (MIC/MBC), and disc diffusion assays against Meticillin-resistant Staphylococcus aureus, Meticillin-resistant S. epidermidis, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. Antibacterial activity without antibiotic was low, confirmed by high MIC/MBC, and a no inhibition on agar lawns. However, VDAM with antibiotic demonstrated effective antibacterial capacity against all bacteria. Therefore, antibiotic decontamination is a reliable method for sterilisation of AM and the resultant antibiotic reservoir is effective against gram-positive and –negative bacteria.

An update on chemical eye burns

Ocular chemical injuries vary in severity, with the more severe end of the spectrum having profound visual consequences and medicolegal implications. Grading of ocular injuries is critical for determining acute treatment and visual prognosis. Poor immediate management results in more challenging treatment of acute disease. Similarly, poorly controlled acute disease results in more treatment-resistant chronic ocular disease. Despite several decades of research and public health initiatives, simple and effective interventions such as wearing protective eyewear and immediate irrigation of eyes remain as key challenges. Education and prevention are therefore important public health messages. Hurdles in the acute management of disease include poor evidence-base for commonly used treatments (e.g. based on experimental animal studies), reduced treatment adherence rates and high clinic non-attendance rates. The evolution of treatment strategies, particularly limbal stem cell transplantation, has revolutionised the visual and cosmetic outcomes in chronic phases of disease. It is therefore increasingly important to consider tertiary referral for patients with limbal stem cell failure or vision-limiting corneal scarring.

Comparison of the impact of preservation methods on amniotic membrane properties for tissue engineering applications

Human amniotic membrane (hAM) is considered as an attractive biological scaffold for tissue engineering. For this application, hAM has been mainly processed using cryopreservation, lyophilization and/or decellularization. However, no study has formally compared the influence of these treatments on hAM properties. The aim of this study was to develop a new decellularization-preservation process of hAM, and to compare it with other conventional treatments (fresh, cryopreserved and lyophilized). The hAM was decellularized (D-hAM) using an enzymatic method followed by a detergent decellularization method, and was then lyophilized and gamma-sterilized. Decellularization was assessed using DNA staining and quantification. D-hAM was compared to fresh (F-hAM), cryopreserved (C-hAM) and lyophilized/gamma-sterilized (L-hAM) hAM. Their cytotoxicity on human bone marrow mesenchymal stem cells (hBMSCs) and their biocompatibility in a rat subcutaneous model were also evaluated. The protocol was effective as judged by the absence of nuclei staining and the residual DNA lower than 50 ng/mg. Histological staining showed a disruption of the D-hAM architecture, and its thickness was 84% lower than fresh hAM (p < 0.001). Despite this, the labeling of type IV and type V collagen, elastin and laminin were preserved on D-hAM. Maximal force before rupture of D-hAM was 92% higher than C-hAM and L-hAM (p < 0.01), and D-hAM was 37% more stretchable than F-hAM (p < 0.05). None of the four hAM were cytotoxic, and D-hAM was the most suitable scaffold for hBMSCs proliferation. Finally, D-hAM was well integrated in vivo. In conclusion, this new hAM decellularization process appears promising for tissue engineering applications.

Comparison of cytokine expression and ultrastructural alterations in fresh-frozen and dried electron beam-irradiated human amniotic membrane and chorion

The purpose of the current study was to compare the effects of drying and fresh-freezing on human amniotic membrane (HAM) and amnion/chorion membrane (HACM) in terms of histological and structural characteristics and cytokine levels. HAM and HACM samples, obtained from six placentae, were investigated. HAM and HACM were dried, electron beam-irradiated (dehydration group; d-HAM/d-HACM), or fresh-frozen (freezing group; f-HAM/f-HACM). Luminex assay was used to assay the levels of 15 cytokines. The ultrastructural characteristics of HAM and HACM were evaluated using light and transmission electron microscopies. Total cytokine contents did not show the statistical difference between dehydration and fresh-freezing process. Significantly higher levels of total cytokines were observed in HACM than in HAM. Epidermal growth factor (EGF) level was significantly higher in d-HAM than in the other samples. The levels of most of the other growth factors were higher in HACM than in HAM, but there was no statistical difference between the dehydration process and the fresh-freezing process. The levels of the cytokines, other than the growth factors, were higher in HACM than in HAM, and higher concentrations of cytokines were observed in the freezing group than in the dehydration group. Histological examination revealed that the dehydration group had thinner tissues than the freezing group, but the structural stability, including the basement membrane, did not differ between the two groups. Microscopic structures such as microvilli and nuclei were well-preserved in the freezing group, based on the results of the transmission electron microscopy. Our dehydration process maintained the histological structure of HAM/HACM and a variety of growth factors and cytokines were identified. Especially, the HAM, processed with the dehydration method, had a higher EGF level than that processed with the fresh-freezing method. Therefore, dehydration method can be used to effectively promote wound repair.

Anti-inflammatory potential of human corneal stroma-derived stem cells determined by a novel in vitro corneal epithelial injury model

BACKGROUND

An in vitro injury model mimicking a corneal surface injury was optimised using human corneal epithelial cells (hCEC).

AIM

To investigate whether corneal-stroma derived stem cells (CSSC) seeded on an amniotic membrane (AM) construct manifests an anti-inflammatory, healing response.

METHODS

Treatment of hCEC with ethanol and pro-inflammatory cytokines were compared in terms of viability loss, cytotoxicity, and pro-inflammatory cytokine release, in order to generate the in vitro injury. This resulted in an optimal injury of 20% (v/v) ethanol for 30 s with 1 ng/mL interleukin-1 (IL-1) beta. Co-culture experiments were performed with CSSC alone and with CSSC-AM constructs. The effect of injury and co-culture on viability, cytotoxicity, IL-6 and IL-8 production, and IL1B, TNF, IL6, and CXCL8 mRNA expression were assessed.

RESULTS

Co-culture with CSSC inhibited loss of hCEC viability caused by injury. Enzyme linked immunosorbent assay and polymerase chain reaction showed a significant reduction in the production of IL-6 and IL-8 pro-inflammatory cytokines, and reduction in pro-inflammatory cytokine mRNA expression during co-culture with CSSC alone and with the AM construct. These results confirmed the therapeutic potential of the CSSC and the possible use of AM as a cell carrier for application to the ocular surface.

CONCLUSION

CSSC were shown to have a potentially therapeutic anti-inflammatory effect when treating injured hCEC, demonstrating an important role in corneal regeneration and wound healing, leading to an improved knowledge of their potential use for research and therapeutic purposes.

An experimental study of amniotic lacrimal duct stents in the treatment of perimenopausal female rabbits with dry eye

The aim of the present study was to investigate the effects of an amniotic membrane lacrimal stent in the treatment of dry eye syndrome in a perimenopausal rabbit model. In total, 48 healthy female rabbits were randomly divided into four groups (12 rabbits/group): Group A, sham-operated group; group B, negative control group; group C, sham-implantation group; and group D, implantation with amniotic membrane lacrimal stents. A Schirmer I test (SIT), corneal fluorescein staining, optical coherence tomography angiography and corneal confocal microscopy were conducted and the biomechanical properties of the amniotic membrane were measured prior to and 2, 4 and 6 weeks after the operations. There were marked differences in the amount of tear secretion and the SIT following the operation compared with prior to the operation. The amount of tear secretion of group B and C was significantly reduced (F=8.894; P=0.0017). Compared with groups A, B and C, group D demonstrated a significant increase in the amount of tear secretion and a significant reduction in SIT (P<0.05). However, there was no statistical difference between the tear secretion of the A, B and C groups (P>0.05). The cornea epithelial of groups A and D was significantly thinner compared with groups B and C. The superior part [superior temporal (ST)5, superior (S)5, superior nasal (SN)5, ST6, S6 and SN6] was significantly thinner compared with the central part of the cornea epithelium. The corneal epithelia of all groups were thin in the center and thick at the edge. At 6 weeks after the operation, group D exhibited a markedly decreased number of anterior stromal luminescent cells, compared with groups A, B and C. Furthermore, the bending degree of corneal stromal neural trunks was significantly improved, and the density, branches and curvature of corneal epithelium sub-basal nerves ameliorated to a certain extent (P<0.05). Amniotic membrane lacrimal stents demonstrated specific therapeutic effects on dry eye in perimenopausal female rabbits.

How to minimize pterygium recurrence rates: clinical perspectives

The main treatment for pterygium is surgical removal. However, pterygium surgery is concerned with high rates of postoperative recurrence. Predicting factors of recurrence are not fully understood, yet, but they probably depend on a multitude of patient-related, clinical, and/or surgical factors. Several adjuvant treatments have been proposed to reduce postoperative pterygium recurrence, including different antimetabolites, antiangiogenetic factors, and radiation therapy. The purpose of this review is to collect the current evidence regarding application and limits of different therapeutic approaches for preventing postoperative recurrence of pterygium, giving insights and perspectives for better management of this disease. In the light of the current evidence, pterygium surgery cannot disregard wound coverage with conjunctival autografting or rotational flap combined with adjuvant treatments. The rotational flap technique is associated with shorter surgical time rates and prevents graft displacement and necrosis, given its vascular pedicle. Amniotic membrane may still be reserved in case of great conjunctival defects or insufficient conjunctiva. Repeated subconjunctival antivascular endothelial growth factor injections can be considered as an effective and safe adjuvant treatment. Moreover, management of postoperative pain is crucial. Innovative treatment strategies will probably target different molecular pathways, considering recent findings regarding pterygium pathogenesis, to improve better understanding and develop universally shared guidelines. Great importance shall be dedicated to the identification of novel molecular biomarkers and favoring factors of recurrence, in order to achieve a customized surgical treatment for each patient and obtain maximal reduction of postoperative recurrence.

Properties of viable lyopreserved amnion are equivalent to viable cryopreserved amnion with the convenience of ambient storage

Human amniotic membrane (AM) has a long history of clinical use for wound treatment. AM serves as a wound protective barrier maintaining proper moisture. AM is anti-inflammatory, anti-microbial and antifibrotic, and supports angiogenesis, granulation tissue formation and wound re-epithelialization. These properties of AM are attributed to its native extracellular matrix, growth factors, and endogenous cells including mesenchymal stem cells. Advances in tissue preservation have helped to overcome the short shelf life of fresh AM and led to the development of AM products for clinical use. Viable cryopreserved amnion (VCAM), which retains all native components of fresh AM, has shown positive outcomes in clinical trials for wound management. However, cryopreservation requires ultra-low temperature storage and shipment that limits widespread use of VCAM. We have developed a lyopreservation technique to allow for ambient storage of living tissues. Here, we compared the structural, molecular, and functional properties of a viable lyopreserved human amniotic membrane (VLAM) with properties of VCAM using in vitro and in vivo wound models. We found that the structure, growth factors, and cell viability of VLAM is similar to that of VCAM and fresh AM. Both, VCAM and VLAM inhibited TNF-α secretion and upregulated VEGF expression in vitro under conditions designed to mimic inflammation and hypoxia in a wound microenvironment, and resulted in wound closure in a diabetic mouse chronic wound model. Taken together, these data demonstrate that VLAM structural and functional properties are equivalent to VCAM but without the constraints of ultra-low temperature storage.

Biochemical characterization of pure dehydrated binate amniotic membrane: role of cytokines in the spotlight

AIM

Placental allografts used for tissue regeneration differ in membrane compositions and processing techniques. A uniquely folded dehydrated binate amniotic membrane (DBAM) was biochemically characterized to evaluate its potential role in wound healing.

METHODS

Histology, Luminex-based immunoassay and standard in vitro cell biology techniques were employed.

RESULTS

Histological staining confirmed that the DBAM was chorion free with epithelial cell layer of the respective amnion membranes facing outward. DBAM had quantifiable levels of relevant cytokines that induced proliferation and migration while bolstering secretory activity of the cells. DBAM retained biological efficacy at a broad range of temperatures.

CONCLUSION

Cytokines in DBAM stimulate bone marrow stromal and stem cells that may lead to tissue regeneration and wound healing in a clinical setup.

Successful Regenerative Endodontic Procedure of a Nonvital Immature Permanent Central Incisor Using Amniotic Membrane as a Novel Scaffold

Successful regenerative endodontic procedure was performed in nonvital immature permanent central incisor (Stage-4 root development) using human amniotic membrane (HAM) as a novel scaffold. The treatment was performed according to the American Association of Endodontics guidelines with minimal canal instrumentation, 1% Sodium hypochlorite as irrigant and calcium hydroxide as intracanal medicament. During the second appointment, HAM was placed as a scaffold and Biodentine™ was layered over the HAM with glass ionomer cement and resin composite as coronal seal. Preoperative and post-operative cone beam computed tomography (at three years) was taken to assess the treatment outcome. The resolution of disease process and increase in canal width, as well as positive response to pulp sensitivity tests, were observed by the end of three years. There was approximately 78–86% reduction in the volume of periapical lesion size. This case report confirms that HAM can be used as a scaffold material for successful regenerative endodontic procedure (REP).