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The amniotic membrane (AM) has a long history of use in the treatment of various diseases of the ocular surface. It contains pluripotent cells, highly organized collagen, anti-fibrotic and anti-inflammatory cytokines, immune-modulators, growth factors, and matrix proteins. It is used to promote corneal healing in severely damaged eyes. Recently, AM extract and AM extract eye drops have been successfully used in clinical applications, including dry eye and chemical burns. We provide an overview on the recent progress in the preparation, mechanisms of action, and use of AM extract/AM extract eye drops for corneal and external eye diseases.

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. 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.

Amniotic membrane transplantation (AMT) is an effective treatment for refractory macular hole closure, yet the underlying mechanism supporting that effectiveness remains unclear. Here, we investigated the role of retinal regeneration in this process using an in vivo rabbit retinal-hole (RH) model in which AMT was performed on one of the holes. Histological and immunofluorescence examinations with anti-glial fibrillary acidic protein and anti-glutemine synthetase antibodies were conducted to evaluate cell migration and hole closure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the tissues after implantation. Optical coherence tomography scans revealed that AMT promoted RH closure. Histological analyses demonstrated that retinal pigment epithelium (RPE) cells migrated onto the AM, and immunofluorescence analyses showed that retinal glial cells, including Müller cells, contributed to RH closure. SEM and TEM findings revealed cellular coverage and extracellular matrix formation at the AMT site, suggesting successful integration with the surrounding retinal tissue. Furthermore, the loss of mitochondrial cristae within the RPE caused by the creation of RH was suppressed by AMT. In summary, AMT promoted RH closure in a rabbit model by serving as a scaffold for retinal cell migration and by preserving RPE integrity, although regeneration of the retinal-layers was not observed.

BackgroundThe classification of macular hole closure patterns (MHCPs) currently relies on time domain OCT allowing only “open” and “closed” statuses or is based on inner foveal contour shape. Both classification types give no information on retinal layer reconstitution. Novel sophisticated surgical techniques lead to previously unknown MHCPs, outdating existing classifications and urging new ones. The purpose of the present study is to introduce a new classification allowing proper description of all MHCPs resulting from newer surgeries and based on the restoration of retinal layers.MethodsRetrospective analysis of patients undergoing MH surgery with five different surgical techniques was performed. MHCPs were classified according to spectral domain optical coherence tomography (SD-OCT). Type 0: open MH (0A: flat margin, 0B: elevated, 0C: oedematous); type 1: closed MHs (1A: reconstitution all retinal layers; 1B interruption of the external layers; 1C interruption of internal layers); type 2: MH closed with autologous or heterologous filling tissue interrupting the normal foveal layered anatomy (2A: filling tissue through all layers; 2B reconstitution of normal inner retinal layers; 2C reconstitution of normal outer retinal layers; 2D H-shaped bridging of filling tissue).ResultsClosure rate was 95.2% (241/253). Surgical technique and vision correlated to closure pattern (p < 0.001). Type 1 MHCPs had the best post-operative visual acuity (VA) compared with type 2 and type 0 (p < 0.001). MHCPs 1A and 1C performed better than all others. MHCP at months 1 and 3 changed in 42/254 (16.5%) and remained stable in 212/254 (83.5%). Improvement in vision was higher in eyes with shifting closure pattern (0.57 ± 0.33 vs 0.51 ± 0.48 logMAR; p 0.021).ConclusionMHCP classification based on retinal layer restoration properly comprises post-operative anatomic morphologies. MHCPs correlate the surgical technique and post-operative visual outcomes.

Regenerative medicine aims to repair and regenerate damaged cells, tissues, and organs in order to restore function. Regeneration can be obtained either by cell replacement or by stimulating the body's own repair mechanisms. Importantly, a favorable environment is required before any regenerative signal can stimulate resident stem/stromal cells, and regeneration is possible only after the resolution of injury-induced inflammation. An exacerbated immune response is often present in cases of degenerative, inflammatory-based diseases. Here we discuss how amniotic membrane cells, and their derivatives, can contribute to the resolution of many diseases with altered immune response by acting on different inflammatory mediators.

Corneal alkali burns persist as a significant challenge in our field, often leading to a prolonged treatment course with various sight-threatening problems. This work, of utmost importance, aimed to apply the photo-tissue bonding technique (PTB) to weld the amniotic membrane (AM) to the corneal surface versus an amniotic membrane graft (AMG) and explore its safety in saving corneal protein against alkali burn. Methods Twenty-seven rabbits with an induced corneal ulcer using 1 mol/L NaOH solution. Nine rabbits were used as an ulcer group without treatment, and the rest (n = 18) were subjected to two treatment protocols with AM. The first was attaching the AM to the corneal ulcer through photo-tissue bonding using 532 nm and rose Bengal stain as a photosynthesizing agent. The second was using cyanoacrylate glue as a tissue adhesive. The corneal total protein (TP), refractive index (RI), DNA fragmentation, and oxidative stress index (OSI) were evaluated. Results: The cornea’s TP showed a significant decrease (p˂0.001) immediately, 1 week, and 2 weeks after ulcer induction (-58.9%, -64.4%, and − 72.6%, respectively). The treatment with AM PTB showed improvement immediately (-45.2%, p˂0.001), after one week (-27.4%, p˂0.01), and after two weeks (-14.38%, p˂0.05). Moreover, the treatment with AMG showed improvement after the same periods with percentage changes of -52.05%, (p˂0.001), -41.8% (p˂0.001), and − 32.2%, (p˂0.01) with respect to the control. Moreover, RI of corneal protein showed improvement after two weeks of treatment with AM PTB (3%, p˃0.05) and AMG (7%, p˃0.05), respectively. The corneal protein DNA base pairs improved 88.49% for AM PTB and 82.35% for the AMG group. The oxidative stress was shifted towards an antioxidative state in AM PTB (-3.9%, P > 0.05) and the AMG group (15.9%, P < 0.05). Conclusion: The AM PTB technique used in corneal ulcers showed promising improvement in total corneal proteins, refractive index, DNA fragmentation, and OSI than AMG using cyanoacrylate glue. These results strongly support the use of AM PTB for ophthalmic purposes, suggesting its potential to enhance clinical research and practice for patients with corneal ulcers and ocular surface diseases.

Background Diabetic wounds threaten the health and quality of life of patients and their treatment remains challenging. ADSC-derived exosomes have shown encouraging results in enhancing diabetic wound healing. However, how to use exosomes in wound treatment effectively is a problem that needs to be addressed at present. Methods A diabetic mouse skin wound model was established. ADSC-derived exosomes (ADSC-Exos) were isolated, and in vitro application of exosomes was evaluated using human umbilical vein endothelial cells (HUVECs) and human dermal fibroblasts (HDFs). After preparation and characterization of a scaffold of human acellular amniotic membrane (hAAM) loaded with ADSC-Exos in vitro, they were transplanted into wounds in vivo and wound healing phenomena were observed by histological and immunohistochemical analyses to identify the wound healing mechanism of the exosome-hAAM composites. Results The hAAM scaffold dressing was very suitable for the delivery of exosomes. ADSC-Exos enhanced the proliferation and migration of HDFs and promoted proliferation and tube formation of HUVECs in vitro. In vivo results from a diabetic skin wound model showed that the hAAM-Exos dressing accelerated wound healing by regulating inflammation, stimulating vascularization, and promoting the production of extracellular matrix. Conclusion Exosome-incorporated hAAM scaffolds showed great potential in promoting diabetic skin wound healing, while also providing strong evidence for the future clinical applications of ADSC-derived exosomes.

Background Human amniotic membrane (AM) transplantation has been applied to treat ocular surface diseases, including corneal trauma. The focus of much deliberation is to balance the mechanical strength of the amniotic membrane, its resistance to biodegradation, and its therapeutic efficacy. It is commonly observed that the crosslinked human decellularized amniotic membranes lose the functional human amniotic epithelial cells (hAECs), which play a key role in curing the injured tissues. Methods and results In this study, we crosslinked human decellularized amniotic membranes (dAM) with genipin and re-planted the hAECs onto the genipin crosslinked AM. The properties of the AM were evaluated based on optical clarity, biodegradation, cytotoxicity, and ultrastructure. The crosslinked AM maintained its transparency. The color of crosslinked AM deepened with increasing concentrations of genipin. And the extracts from low concentrations of genipin crosslinked AM had no toxic effect on human corneal epithelial cells (HCECs), while high concentrations of genipin exhibited cytotoxicity. The microscopic observation and H&E staining revealed that 2 mg/mL genipin-crosslinked dAM (2 mg/mL cl-dAM) was more favorable for the attachment, migration, and proliferation of hAECs. Moreover, the results of the CCK-8 assay and the transwell assay further indicated that the living hAECs’ tissue-engineered amniotic membranes could facilitate the proliferation and migration of human corneal stromal cells (HCSCs) in vitro. Conclusions In conclusion, the cl-dAM with living hAECs demonstrates superior biostability and holds significant promise as a material for ocular surface tissue repair in clinical applications.

Asherman’s syndrome is an endometrial regeneration disorder resulting from injury to the endometrial basal layer, causing the formation of scar tissue in the uterus and cervix. This usually leads to uterine infertility, menstrual disorders, and placental abnormalities. While stem cell therapy has shown extensive progress in repairing the damaged endometrium and preventing intrauterine adhesion, issues of low engraftment rates, rapid senescence, and the risk of tumorigenesis remain to be resolved for efficient and effective application of this technology in endometrial repair. This study addressed these challenges by developing a co-culture system to generate multi-lineage endometrial organoids (MLEOs) comprising endometrial epithelium organoids (EEOs) and endometrial mesenchymal stem cells (eMSCs). The efficacy of these MLEOs was investigated by seeding them on a biocompatible scaffold, the human acellular amniotic membrane (HAAM), to create a biological graft patch, which was subsequently transplanted into an injury model of the endometrium in rats. The results indicated that the MLEOs on the HAAM patch facilitated endometrial angiogenesis, regeneration, and improved pregnancy outcomes. The MLEOs on the HAAM patch could serve as a promising strategy for treating endometrial injury and preventing Asherman’s syndrome.

Gelatin-methacryloyl (GelMA) is a highly adaptable biomaterial extensively utilized in skin regeneration applications. However, it is frequently imperative to enhance its physical and biological qualities by including supplementary substances in its composition. The purpose of this study was to fabricate and characterize a bi-layered GelMA-gelatin scaffold using 3D bioprinting. The upper section of the scaffold was encompassed with keratinocytes to simulate the epidermis, while the lower section included fibroblasts and HUVEC cells to mimic the dermis. A further step involved the addition of amniotic membrane extract (AME) to the scaffold in order to promote angiogenesis. The incorporation of gelatin into GelMA was found to enhance its stability and mechanical qualities. While the Alamar blue test demonstrated that a high concentration of GelMA (20%) resulted in a decrease in cell viability, the live/dead cell staining revealed that incorporation of AME increased the quantity of viable HUVECs. Further, gelatin upregulated the expression of KRT10 in keratinocytes and VIM in fibroblasts. Additionally, the histological staining results demonstrated the formation of well-defined skin layers and the creation of extracellular matrix (ECM) in GelMA/gelatin hydrogels during a 14-day culture period. Our study showed that a 3D-bioprinted composite scaffold comprising GelMA, gelatin, and AME can be used to regenerate skin tissues.