Amniotic membrane properties and current practice of amniotic membrane use in ophthalmology in Slovenia

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.

Processing methods for human amniotic membrane as scaffold for tissue engineering with mesenchymal stromal human cells

Tissue engineering is an interdisciplinary field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function. The aims of this work were to compare chemically and physically processed human Amniotic Membranes (hAM) and analyze the cytocompatibility and proliferation rate (PR) of two primary human mesenchymal stromal cell lines, from different sources and donor conditions seeded over these scaffolds. The evaluated hAM processes were: cold shock to obtain a frozen amniotic membrane (FEAM) with remaining dead epithelial cells, denudation of hAM with trypsin for 20/10 min (DEAM20/10) or treatment with sodium dodecyl sulfate to decellularized hAM (DAM). All samples were sterilized with gamma radiation. The selection of the treated hAM to then generate composites was performed by scanning and transmission electron microscopy and characterization by X-ray diffraction, selecting DEAM10 and FEAM as scaffolds for cell seeding. Two sources of primary human stromal cells were used, both developed by our researchers, human Dental Pulp Stem Cells (hDPSC) from living donors and human Mesenchymal Stromal Cells (hMSC) from bone marrow isolated from brain dead donors. This last line of cells conveys a novel source of human cells that, to our knowledge, have not been tested as part of this type of construct. We developed four in vitro constructs without cytotoxicity signs and with different PR depending on the scaffolds and cells. hDPSC and hMSC grew over both FEAM and DEAM10, but DEAM10 allowed higher PR.

The use of platelet lysate to increase the growth-stimulating effect of the amniotic membrane <i>in vitro</i>

AIM: To work out the technique of saturation of the preserved amniotic membrane (AM) with platelet rich plasma (PRP) lysate and to evaluate the growth-stimulating effect of a combination of AM and PRP lysate in vitro. MATERIALS AND METHODS: In the experiment, AM samples preserved in 3 ways were used: silicate drying, lyophilization, cryopreservation. PRP lysate was prepared on the basis of volunteers blood. During the exposure of AM with PRP lysate, the optimal saturation time of canned AM with lysate was determined, the volume of lysate that 1 cm2 of AM could adsorb was estimated. The growth-stimulating effect of AM transplants was evaluated in the culture of human buccal epithelium. The dynamics of cell growth was evaluated after 1, 2 and 3 days from the moment of sowing. RESULTS: In the presence of PRP lysate, the mass of silicatedried AM increased 4.2 times, lyophilized AM 4.8 times, cryopreserved AM 1.8 times. AM samples obtained by lyophilization adsorbed PRP lysate most effectively. Five minutes of exposure with PRP lysate are enough to fully saturate the AM. AM without PRP lysate did not give a growth-stimulating effect. CONCLUSIONS: When comparing experiments with PRP lysate without AM and AM with PRP lysate, it was found that the greatest stimulation of cell growth occurred when using lyophilized AM and PRP lysate. Saturation of cryopreserved AM with PRP lysate was ineffective, and when using silicate-dried AM impregnated with PRP lysate, the greatest growth-stimulating effect was observed on the 1st day.

The biological effect of a combination of platelet lysate and amniotic membrane in buccal epithelium culture

Purpose: To study the biological effect of a combination of platelet lysate and amniotic membrane, preserved by various techniques, on human buccal epithelium culture. Materials and methods. Human amnion transplants were preserved using 3 methods: silicate drying, lyophilization, cryopreservation. The blood of healthy volunteers was used as a source of platelets. Platelet-rich plasma (PRP) with a platelet content over 1000 thousand/mcl and more was isolated from the donors blood, frozen at -80 °С and defrosted at 0–4 °С to prepare platelet lysate. Growth-stimulating effect of the amnion transplants was studied in different groups: control group 1 — without amnion and without PRP lysate; control group 2 — PRP lysate without amnion; experimental group 1 — amnion without PRP lysate; experimental group 2 — amnion samples combined with PRP lysate. The study was carried out on the example of human buccal epithelium culture of 3–5 passages. The dynamics of cell growth was evaluated after 1, 2 and 3 days from the moment of seeding. The number of cells and their viability were evaluated using original methods based on vital cell staining and their examination in a fluorescent microscope. Results. All samples of preserved amnions were non-toxic and did not damage the structural and functional characteristics of the buccal epithelium. On the other hand, the use of amnion without PRP lysate did not have a growth-stimulating effect on cells. Among the amnion samples combined with PRP lysate, the combination of lyophilized amnion and PRP lysate was the most effective during the entire study period. Conclusions. Silicate drying, lyophilization and cryopreservation of the amniotic membrane makes it possible to obtain biocompatible and non-toxic transplants, based on human amnion. Lyophilized amnions are the most optimal for saturating PRP lysate. The combination of lyophilized amnion and PRP lysate stimulates cell growth in vitro without violating their structural integrity.

Case Report: Freeze-Dried Human Amniotic Membrane Allograft for the Treatment of Chronic Wounds: Results of a Multicentre Observational Study

An inability of the human body to heal acute wounds under certain conditions results in the formation of chronic ulcers. Chronic wounds not only cause significant pain and discomfort for patients but also serve as an entry for microorganisms into the human body, which can result in serious life-threatening problems and become a significant burden for the patients and society. The current work present results of a multicentre prospective observational study demonstrating the use of a lyophilized amniotic membrane (AM) in the treatment of chronic wounds (various etiologies). Lyophilized AM produced under the commercial brand Amnioderm® was used as an allograft material for therapy of chronic wounds, in addition to chronic ulcer standard-of-care (SoC) protocols. The duration of wounds considered for the application of AM ranged between 2 months and 11 years. In total, 16 patients were enrolled to the study, of which eight were completely healed, six demonstrated a significantly reduced ulcer size, and two did not respond to the AM therapy. The current study unambiguously demonstrates an effective alternative to the standard of chronic wound care and confirms a significant effect of the AM application for chronic wound management as a new SoC.

Antimicrobial Activity of Human Fetal Membranes: From Biological Function to Clinical Use

The fetal membranes provide a supportive environment for the growing embryo and later fetus. Due to their versatile properties, the use of fetal membranes in tissue engineering and regenerative medicine is increasing in recent years. Moreover, as microbial infections present a crucial complication in various treatments, their antimicrobial properties are gaining more attention. The antimicrobial peptides (AMPs) are secreted by cells from various perinatal derivatives, including human amnio-chorionic membrane (hACM), human amniotic membrane (hAM), and human chorionic membrane (hCM). By exhibiting antibacterial, antifungal, antiviral, and antiprotozoal activities and immunomodulatory activities, they contribute to ensuring a healthy pregnancy and preventing complications. Several research groups investigated the antimicrobial properties of hACM, hAM, and hCM and their derivatives. These studies advanced basic knowledge of antimicrobial properties of perinatal derivatives and also provided an important insight into the potential of utilizing their antimicrobial properties in a clinical setting. After surveying the studies presenting assays on antimicrobial activity of hACM, hAM, and hCM, we identified several considerations to be taken into account when planning future studies and eventual translation of fetal membranes and their derivatives as antimicrobial agents from bench to bedside. Namely, (1) the standardization of hACM, hAM, and hCM preparation to guarantee rigorous antimicrobial activity, (2) standardization of the antimicrobial susceptibility testing methods to enable comparison of results between various studies, (3) investigation of the antimicrobial properties of fetal membranes and their derivatives in the in vivo setting, and (4) designation of donor criteria that enable the optimal donor selection. By taking these considerations into account, future studies will provide crucial information that will enable reaching the optimal treatment outcomes using the fetal membranes and their derivatives as antimicrobial agents.

Case Report: Wound Closure Acceleration in a Patient With Toxic Epidermal Necrolysis Using a Lyophilised Amniotic Membrane

Background: Toxic epidermal necrolysis (TEN) is a rare life-threatening disease that mainly affects the skin and mucous membranes, resulting from a toxic delayed-type hypersensitivity (DTH) reaction (type IV reaction) to the presence of foreign antigens such as drugs. The clinical symptoms are caused by pathophysiological processes leading to massive apoptosis of keratinocytes in the dermo-epidermal junction. This results in the formation of a bulla and subsequent separation of the entire epidermis with the exposure of the dermis. The current approach in the local therapy of TEN prefers the use of biological dressings, which helps provide several critical requirements for defect healing; in particular, it helps in the acceleration of the spontaneous wound closure (re-epithelialization) of the skin defect and the reduction of the risk of development of various complications and infections, such as the risk of pathological scar maturation. This paper is a case report of the use of a lyophilized amniotic membrane (AM) for accelerating wound healing in a patient with TEN. Case Presentation: We report a case of an 8-year-old girl transferred to our center with a histologically confirmed diagnosis of TEN. Despite the application of immunosuppressive therapy consisting of corticosteroids and intravenous immunoglobulins, we have observed disease progression and exfoliation of up to 60% of the total body surface area (TBSA). In the facial area, which is cosmetically privileged, we decided to use the lyophilized amniotic membrane (Amnioderm®) to cover up approximately 2% of the TBSA. Within 2 days after the application, we observed accelerated reepithelialisation, with rapid wound closure. We have not observed any side effects nor infections during the subsequent phases of wound healing. Skin defects in non-facial areas of the body were treated with synthetic dressings. When compared to the areas covered with the lyophilized AM, the healing process was prolonged. Conclusions: To our knowledge, this is the first case study using a lyophilized amniotic membrane in the treatment of a patient with TEN. The AM application in the cosmetically-privileged area (face), proved to be very efficient in the treatment of TEN patients. The use of this allogeneic material demonstrated excellent biocompatibility and caused a unique acceleration of epithelialization and wound healing, yielding also excellent long-term results. The current study opens broad possibilities for clinical application of the used material, the improvement of current therapy of patients with TEN and better outcomes and recovery of patients.

Perinatal Derivatives: Where Do We Stand? A Roadmap of the Human Placenta and Consensus for Tissue and Cell Nomenclature

Progress in the understanding of the biology of perinatal tissues has contributed to the breakthrough revelation of the therapeutic effects of perinatal derivatives (PnD), namely birth-associated tissues, cells, and secreted factors. The significant knowledge acquired in the past two decades, along with the increasing interest in perinatal derivatives, fuels an urgent need for the precise identification of PnD and the establishment of updated consensus criteria policies for their characterization. The aim of this review is not to go into detail on preclinical or clinical trials, but rather we address specific issues that are relevant for the definition/characterization of perinatal cells, starting from an understanding of the development of the human placenta, its structure, and the different cell populations that can be isolated from the different perinatal tissues. We describe where the cells are located within the placenta and their cell morphology and phenotype. We also propose nomenclature for the cell populations and derivatives discussed herein. This review is a joint effort from the COST SPRINT Action (CA17116), which broadly aims at approaching consensus for different aspects of PnD research, such as providing inputs for future standards for the processing and in vitro characterization and clinical application of PnD.

Human Amniotic Membrane and Amniotic Membrane-Derived Cells: How Far Are We from Their Use in Regenerative and Reconstructive Urology?

Human amniotic membrane (hAM) is the innermost layer of fetal membranes, which surrounds the developing fetus and forms the amniotic cavity. hAM and hAM-derived cells possess many properties that make them suitable for use in regenerative medicine, such as low immunogenicity, promotion of epithelization, anti-inflammatory properties, angiogenic and antiangiogenic properties, antifibrotic properties, antimicrobial properties, and anticancer properties. Many pathological conditions of the urinary tract lead to organ damage or complete loss of function. Consequently, the reconstruction or replacement of damaged organs is needed, which makes searching for new approaches in regenerative and reconstructive urology a necessity. The use of hAM for treating defects in kidneys, ureters, urinary bladder, and urethra was tested in vitro in cell cultures and in vivo in mice, rats, rabbits, cats, dogs, and also in humans. These studies confirmed the advantages and the potential of hAM for use in regenerative and reconstructive urology as stated above. However, they also pointed out a few concerns we have to take into consideration. These are (1) the lack of a standardized protocol in hAM preparation and storage, (2) the heterogeneity of hAM, and especially (3) low mechanical strength of hAM. Before any wider use of hAM for treating urological defects, the protocols for preparation and storage will need to be standardized, followed by more studies on larger animals and clinical trials, which will altogether extensively assess the potential of hAM use in urological patients.

Supportive properties of basement membrane layer of human amniotic membrane enable development of tissue engineering applications

Human amniotic membrane (HAM) has been widely used as a natural scaffold in tissue engineering due to many of its unique biological properties such as providing growth factors, cytokines and tissue inhibitors of metalloproteinases. This study aimed at finding the most suitable and supportive layer of HAM as a delivery system for autologous or allogeneic cell transplantation. Three different layers of HAM were examined including basement membrane, epithelial and stromal layers. In order to prepare the basement membrane, de-epithelialization was performed using 0.5 M NaOH and its efficiency was investigated by histological stainings, DNA quantification, biomechanical testing and electron microscopy. Adipose-derived stromal cells (ASCs) and a human immortalized keratinocyte cell line (HaCaT) were seeded on the three different layers of HAM and cultured for 3 weeks. The potential of the three different layers of HAM to support the attachment and viability of cells were then monitored by histology, electron microscopy and (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Moreover, mechanical strengths of the basement membrane were assessed before and after cell culture. The results indicated that the integrity of extra cellular matrix (ECM) components was preserved after de-epithelialization and resulted in producing an intact basement amniotic membrane (BAM). Moreover, all three layers of HAM could support the attachment and proliferation of cells with no visible cytotoxic effects. However, the growth and viability of both cell types on the BAM were significantly higher than the other two layers. We conclude that growth stimulating effectors of BAM and its increased mechanical strength after culturing of ASCs, besides lack of immunogenicity make it an ideal model for delivering allogeneic cells and tissue engineering applications.

Optimizing amniotic membrane tissue banking protocols for ophthalmic use

Amniotic membrane (AM) due to its anti-inflammatory, anti-scarring and anti-angiogenic properties is used as corneal and wound grafts. When developing AM tissue banks, cell viability, membrane morphology and genomic stability should be preserved following cryopreservation. To analyze the changes rendered to the AM during the process of cryopreservation by comparing different combinations of standard cryopreservation media; fetal bovine serum (FBS), dimethyl sulfoxide (DMSO), Dulbecco's modified eagle's medium (DMEM) and glycerol at -80 °C and at -196 °C for a period of 6 weeks and at 4 °C in 70 % alcohol for 6 weeks. Following informed consent, placentae of healthy term pregnancies delivered by elective Cesarean section were collected and AM separated into 5 × 5 cm size sections and under sterile conditions stored in 9:1 DMSO:FBS and 1:1 DMEM:Glycerol at -196 and -80 °C for 6 weeks. Similar sections were also stored at 4 °C in 70 % alcohol for 6 weeks. After storage periods following were assessed; AM epithelial cell viability by trypan blue vital stain, epithelial cell proliferation capacity by cell doubling time, membrane morphology by haematoxylin and eosin (H&E) stain and genomic stability by conventional G-banded karyotyping. Human amniotic epithelial cells were cultured in DMEM and 10 % FBS in humidified atmosphere of 5 % carbon dioxide at 37 °C and were characterized using RT-PCR for Octamer-binding protein 4 (Oct-4) and glucose-6-phosphate dehydrogenase (G6PD) genes. All the above parameters were also assessed in fresh AM. AM obtained from 4 term placentae. Mean cell count and mean cell doubling times in days respectively; for fresh AM 3.8 × 10(6); 1.59, after 6 weeks in DMSO:FBS at -196 °C 3.0 × 10(6); 2.38 and at -80 °C 2.1 × 10(6); 1.60, in DMEM:Glycerol at -196 °C 3.6 × 10(6); 2.33 at -80 °C 23 × 10(6); 1.66 and at 4 °C 3.3 × 10(6); 2.14. Histology analysis of the fresh AM showed an intact epithelial monolayer, thick basement membrane (BM) and avascular stromal matrix. Amniotic membranes stored at -196 °C showed morphology similar to fresh AM in both preservation media and AM stored at -80 °C showed disruption of the stromal matrix. At 4 °C the epithelial monolayer showed flattening. Fresh AM karyotype was 46XX. Analyzable spreads for karyotype were not obtained from stored AMs. Human amniotic epithelial cells were positive for both Oct-4 and G6PD genes. AM is best preserved at -196 °C either in 1:9 DMSO:FBS or 1:1 DMEM:Glycerol. In both conditions cell viability and membrane integrity were shown to be preserved up to 6 weeks. Since analyzable chromosome spreads from cell cultures were not obtained, genomic stability could not be assessed.

Ophthalmic indications of amniotic membrane transplantation in Mexico: an eight years Amniotic Membrane Bank experience

Amniotic membrane, the inner layer of the placenta, has biological properties (e.g. promotes epithelization, reduces fibrosis, secretes antimicrobial products and inhibits immune responses) which make it a useful option for several ophthalmologic procedures, especially those involving the ocular surface. Its use in eye surgery has been reported by other authors. To our knowledge, there is a lack of descriptive studies on surgical indications using amniotic membrane in Mexican population. Here we describe the eight years Amniotic Membrane Bank experience in Mexico, including a detailed protocol of the donors selection, tissue harvesting, preparation, storage and distribution of amniotic membrane since its establishment in 2007. Moreover, we describe the Ophthalmological indications of amniotic membrane transplantation of the total of 1686 amniotic membranes fragments used during eight years. The five most common indications for amniotic membrane transplantation were pterygium (46 %), corneal ulcers (12.6 %), conjunctival surface repair (11.1 %), neoplasms (7.4 %), and persistent epithelial defects (7.3 %). In addition, we compared the indications of amniotic membrane use in two different types of Institutions: general hospitals and ophthalmologic reference hospitals. We found interesting differences between the indications and use rates between these institutions, although pterygium was the most frequent pathology that amniotic membrane fragments were used in both institutions, there was up to a five-fold increase in the use of amniotic membrane for correction of persistent epithelial defects in reference hospitals which could be explained due to the more complex and severe ophthalmological pathologies admitted in reference hospitals. In conclusion, Amniotic Membrane is used in a numerous ocular pathologies and especially on pterygium in our Mexican population.

Epithelial-Mesenchymal Interactions in Urinary Bladder and Small Intestine and How to Apply Them in Tissue Engineering

Reciprocal interactions between the epithelium and mesenchyme are essential for the establishment of proper tissue morphology during organogenesis and tissue regeneration as well as for the maintenance of cell differentiation. With this review, we highlight the importance of epithelial-mesenchymal cross talk in healthy tissue and further discuss its significance in engineering functional tissues in vitro. We focus on the urinary bladder and small intestine, organs that are often compromised by disease and are as such in need of research that would advance effective treatment or tissue replacement. To date, the understanding of epithelial-mesenchymal reciprocal interactions has enabled the development of in vitro biomimetic tissue equivalents that have provided many possibilities in treating defective, damaged, or even cancerous tissues. Although research of the past several years has advanced the field of bladder and small intestine tissue engineering, one must be aware of its current limitations in successfully and above all safely introducing tissue-engineered constructs into clinical practice. Special attention is in particular needed when treating cancerous tissues, as initially successful tumor excision and tissue reconstruction may later on result in cancer recurrence due to oncogenic signals originating from an altered stroma. Recent rather poor outcomes in pioneering clinical trials of bladder reconstructions should serve as a reminder that recreating a functional organ to replace a dysfunctional one is an objective far more difficult to reach than initially foreseen. When considering effective tissue engineering approaches for diseased tissues in humans, it is imperative to introduce animal models with dysfunctional or, even more importantly, cancerous organs, which would greatly contribute to predicting possible complications and, hence, reducing risks when translating to the clinic.