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

Effect of Decellularized Amniotic Membrane on the Tendon-Bone Integration in Rotator Cuff Repair: A Comparative Rat Model Study

OBJECTIVE

Rotator cuff retear after arthroscopy repair is a difficult complication that is often due to poor tendon-bone healing. Decellularized amniotic membrane (DAM) has a variety of bioactive substances which have great potential to enhance tendon-bone healing. However, DAM has three layers, of which the middle basement layer is dense and thick. Whether DAM will hinder tendon-bone healing of rotator cuff after surgical repair is unclear. Our study aims to investigate the effect of DAM on tendon-bone healing of the rotator cuff after surgical repair.

METHODS

Thirty-three Sprague-Dawley (SD) rats were selected to establish unilateral supraspinatus (ST) tear models and were randomly treated with only suturing repair (OSR group, n = 11), and suturing repair with DAM placed between the ST and bone (DAM group, n = 11). In the normal control group (NCT group, n = 11), the supraspinatus was only exposed but not detached or repaired. After 4 weeks the rats were sacrificed. The assessment of specimens was conducted by micro-CT analysis, histopathological evaluation, and biomechanical testing.

RESULTS

The DAM group had a significantly higher ultimate load to failure, new bone volume, and histological evaluation at 4 weeks after surgery than the OSR group. When comparing the DAM group to the NCT group, the DAM group performed slightly worse in biomechanical testing, micro-CT analysis, and histological evaluation.

CONCLUSION

When placed between tendon and bone at the rotator cuff footprint, DAM, despite its dense and thick basement layer, does not impede tendon-bone healing after surgical repair for rotator cuff injury, but rather promotes increased healing quality and biomechanical properties. However, the healing quality and biomechanical properties are still lower than that of the normal rotator cuff, and further improvement should be made to the application strategy of a DAM.

Transplanted artificial amnion membrane enhanced wound healing in third-degree burn injury diabetic mouse model

Introduction

Wound healing is severely compromised in patients with diabetes owing to factors such poor blood circulation, delayed immune response, elevated blood sugar levels, and neuropathy. Although the development of new wound healing products and prevention of serious complications such as infections in wounds have received substantial interest, wound healing remains a challenge in regenerative medicine. Burn wounds, especially third-degree burns, are difficult to treat because they are associated with immune and inflammatory reactions and distributive shock. Wound care and treatment that protects the burn site from infection and allows wound healing can be achieved with bioengineered wound dressings. However, few studies have reported effective dressings for third-degree burn wounds, making it important to develop new dressing materials.

Methods

In this study, we developed an artificial amniotic membrane (AM) using epithelial and mesenchymal cells derived from human amnion as a novel dressing material. The artificial AM was applied to the wound of a diabetic third-degree burn model and its wound healing ability was evaluated.

Results

This artificial amnion produced multiple growth factors associated with angiogenesis, fibroblast proliferation, and anti-inflammation. In addition, angiogenesis and granulation tissue formation were promoted in the artificial AM-treated mouse group compared with the control group. Furthermore, the inflammatory phase was prolonged in the control group.

Conclusions

Our preliminary results indicate that the artificial AM might be useful as a new dressing for refractory ulcers and third-degree burns. This artificial AM-based material represents great potential for downstream clinical research and treatment of diabetes patients with third-degree burns.

Decellularization of various tissues and organs through chemical methods

Due to the increase in demand for donor organs and tissues during the past 20 years, new approaches have been created. These methods include, for example, tissue engineering in vitro and the production of regenerative biomaterials for transplantation. Applying the natural extracellular matrix (ECM) as a bioactive biomaterial for clinical applications is a unique approach known as decellularization technology. Decellularization is the process of eliminating cells from an extracellular matrix while preserving its natural components including its structural and functional proteins and glycosaminoglycan. This can be achieved by physical, chemical, or biological processes. A naturally formed three-dimensional structure with a biocompatible and regenerative structure is the result of the decellularization process. Decreasing the biological factors and antigens at the transplant site reduces the risk of adverse effects including inflammatory responses and immunological rejection. Regenerative medicine and tissue engineering applications can benefit from the use of decellularization, a promising approach that provides a biomaterial that preserves its extracellular matrix.

Efficacy of Fresh Versus Preserved Amniotic Membrane Grafts for Ocular Surface Reconstruction: Meta-analysis

Amniotic membrane transplantation is commonly employed in ophthalmology to mend corneal epithelial and stromal defects. Its effectiveness in restoring the ocular surface has been widely acknowledged in clinical practice. Nevertheless, there is ongoing debate regarding the comparative effectiveness of using fresh amniotic membranes versus preserved ones. The objective of this meta-analysis was to ascertain whether there is a disparity in the effectiveness of fresh versus preserved amniotic membrane in the restoration of the ocular surface in clinical practice. The study utilized the following keywords: "fresh amniotic membrane," "preserved amniotic membrane," "amniotic membrane transplantation," and "ocular surface reconstruction." The study conducted a comprehensive search for relevant studies published until April 18, 2024. Seven different databases, namely PubMed, Web of Science, Embase, Cochrane, China Knowledge, China Science and Technology Journal VIP database, and Wanfang database, were utilized. The search was performed using the keywords "fresh amniotic membrane," "preserved amniotic membrane," "amniotic membrane transplantation," and "ocular surface reconstruction." The process of literature review and data extraction was carried out separately by two researchers, and all statistical analyses were conducted using Review Manager 5.4.1. The final analysis comprised nine cohort studies, encompassing a total of 408 participants. The statistics included six outcome indicators: visual acuity (relative risk [RR] = 1.07, 95% confidence interval [CI] = 0.93-1.24, I2 = 0); amniotic membrane viability (RR = 1.00, 95% CI = 0.93-1.08, I2 = 0); ocular congestion resolution (RR = 1.11, 95% CI = 0.97-1.26, I2 = 0); fluorescent staining of amniotic membranes on the second day after the operation (RR = 1.31, 95% CI = 0.80-2.14, I2 = 11); postoperative recurrence rate (RR = 1.01, 95% CI = 0.50-2.03, I2 = 0); and premature lysis of amniotic membrane implants (RR = 0.96, 95% CI = 0.49-1.88, I2 = 0). The findings indicated that there was no statistically significant disparity between fresh and preserved amniotic membranes across any of the measured variables. There is no substantial disparity in the effectiveness of fresh and preserved amniotic membrane transplants in restoring the ocular surface, and both yield favorable and consistent outcomes.

Current State and Challenges of Tissue and Organ Cryopreservation in Biobanking

Recent years have witnessed significant advancements in the cryopreservation of various tissues and cells, yet several challenges persist. This review evaluates the current state of cryopreservation, focusing on contemporary methods, notable achievements, and ongoing difficulties. Techniques such as slow freezing and vitrification have enabled the successful preservation of diverse biological materials, including embryos and ovarian tissue, marking substantial progress in reproductive medicine and regenerative therapies. These achievements highlight improved post-thaw survival and functionality of cryopreserved samples. However, there are remaining challenges such as ice crystal formation, which can lead to cell damage, and the cryopreservation of larger, more complex tissues and organs. This review also explores the role of cryoprotectants and the importance of optimizing both cooling and warming rates to enhance preservation outcomes. Future research priorities include developing new cryoprotective agents, elucidating the mechanisms of cryoinjury, and refining protocols for preserving complex tissues and organs. This comprehensive overview underscores the transformative potential of cryopreservation in biomedicine, while emphasizing the necessity for ongoing innovation to address existing challenges.

Characterization of Amnion-Derived Membrane for Clinical Wound Applications

Human amniotic membrane (hAM), the innermost placental layer, has unique properties that allow for a multitude of clinical applications. It is a common misconception that birth-derived tissue products, such as dual-layered dehydrated amnion-amnion graft (dHAAM), are similar regardless of the manufacturing steps. A commercial dHAAM product, Axolotl Biologix DualGraft™, was assessed for biological and mechanical characteristics. Testing of dHAAM included antimicrobial, cellular biocompatibility, proteomics analysis, suture strength, and tensile, shear, and compressive modulus testing. Results demonstrated that the membrane can be a scaffold for fibroblast growth (cellular biocompatibility), containing an average total of 7678 unique proteins, 82,296 peptides, and 96,808 peptide ion variants that may be antimicrobial. Suture strength results showed an average pull force of 0.2 N per dHAAM sample (equating to a pull strength of 8.5 MPa). Tensile modulus data revealed variation, with wet samples showing 5× lower stiffness than dry samples. The compressive modulus and shear modulus displayed differences between donors (lots). This study emphasizes the need for standardized processing protocols to ensure consistency across dHAAM products and future research to explore comparative analysis with other amniotic membrane products. These findings provide baseline data supporting the potential of amniotic membranes in clinical applications.

Cell therapy in the cornea: The emerging role of microenvironment

The cornea is an ideal testing field for cell therapies. Its highly ordered structure, where specific cell populations are sequestered in different layers, together with its accessibility, has allowed the development of the first stem cell-based therapy approved by the European Medicine Agency. Today, different techniques have been proposed for autologous and allogeneic limbal and non-limbal cell transplantation. Cell replacement has also been attempted in cases of endothelial cell decompensation as it occurs in Fuchs dystrophy: injection of cultivated allogeneic endothelial cells is now in advanced phases of clinical development. Recently, stromal substitutes have been developed with excellent integration capability and transparency. Finally, cell-derived products, such as exosomes obtained from different sources, have been investigated for the treatment of severe corneal diseases with encouraging results. Optimization of the success rate of cell therapies obviously requires high-quality cultured cells/products, but the role of the surrounding microenvironment is equally important to allow engraftment of transplanted cells, to preserve their functions and, ultimately, lead to restoration of tissue integrity and transparency of the cornea.

Assessment of the proteome profile of decellularized human amniotic membrane and its biocompatibility with umbilical cord-derived mesenchymal stem cells

Extracellular matrix-based bio-scaffolds are useful for tissue engineering as they retain the unique structural, mechanical, and physiological microenvironment of the tissue thus facilitating cellular attachment and matrix activities. However, considering its potential, a comprehensive understanding of the protein profile remains elusive. Herein, we evaluate the impact of decellularization on the human amniotic membrane (hAM) based on its proteome profile, physicochemical features, as well as the attachment, viability, and proliferation of umbilical cord-derived mesenchymal stem cells (hUC-MSC). Proteome profiles of decellularized hAM (D-hAM) were compared with hAM, and gene ontology (GO) enrichment analysis was performed. Proteomic data revealed that D-hAM retained a total of 249 proteins, predominantly comprised of extracellular matrix proteins including collagens (collagen I, collagen IV, collagen VI, collagen VII, and collagen XII), proteoglycans (biglycan, decorin, lumican, mimecan, and versican), glycoproteins (dermatopontin, fibrinogen, fibrillin, laminin, and vitronectin), and growth factors including transforming growth factor beta (TGF-β) and fibroblast growth factor (FGF) while eliminated most of the intracellular proteins. Scanning electron microscopy was used to analyze the epithelial and basal surfaces of D-hAM. The D-hAM displayed variability in fibril morphology and porosity as compared with hAM, showing loosely packed collagen fibers and prominent large pore areas on the basal side of D-hAM. Both sides of D-hAM supported the growth and proliferation of hUC-MSC. Comparative investigations, however, demonstrated that the basal side of D-hAM displayed higher hUC-MSC proliferation than the epithelial side. These findings highlight the importance of understanding the micro-environmental differences between the two sides of D-hAM while optimizing cell-based therapeutic applications.

Introduction to Amniotic Membranes in Maxillofacial Surgery-A Scoping Review

Background: Amniotic membrane (AM) holds significant promise in various medical fields due to its unique properties and minimal ethical concerns. This study aims to explore the diverse applications of the human amniotic membrane (HAM) in maxillofacial surgery. Methodology: A comprehensive search was conducted on databases, namely Google Scholar, PubMed, and Scopus, from January 1985 to March 2024. Articles in English, Polish, and Spanish were included, focusing on keywords related to amniotic membrane and oral surgery. Results: Various preservation methods for HAM were identified, namely fresh, decellularized, cryopreserved, lyophilized, and air-dried formats. Clinical studies demonstrated the efficacy of HAM in repairing oral mucosal defects, vestibuloplasty, oronasal fistula closure, cleft palate treatment, bone defect repair, and medication-related osteonecrosis of the jaw (MRONJ). Surgeon evaluations highlighted the ease of handling but noted challenges in suturing and stability during application. Conclusions: Amniotic membranes offer a versatile and effective option in maxillofacial surgery, promoting wound healing, reducing inflammation, and providing a scaffold for tissue regeneration. Further research, including randomized trials and comparative studies, is warranted to validate the efficacy and optimize the utilization of HAM in clinical practice.

An important detail that is still not clear in amniotic membrane applications: How do we store the amniotic membrane best?

The use of fresh amniotic membrane (AM) is not a viable option, as it has many disadvantages. Preserving the AM reduces the risk of cross-infection and maintains its effectiveness for a long time. In order to maximize the therapeutic effects of the AM, the basic need is to preserve its vitality and the bioactive molecules it contains. However, the effect of preservation procedures on cell viability and growth factors is a still matter of debate. Optimum preservation method is expected to be cost-effective, easily-accessible, and most importantly, to preserve the effectiveness of the tissue for the longest time. However, each preservation technique has its advantages and disadvantages over the other, and each one compromises the vitality and bioactive molecules of the tissue to some extent. Therefore, the best method of preservation is still controversial, and the question of 'how to preserve the AM best?' has not yet been definitively answered.

Development of Novel Polysaccharide Membranes for Guided Bone Regeneration: In Vitro and In Vivo Evaluations

INTRODUCTION

Guided bone regeneration (GBR) procedures require selecting suitable membranes for oral surgery. Pullulan and/or dextran-based polysaccharide materials have shown encouraging results in bone regeneration as bone substitutes but have not been used to produce barrier membranes. The present study aimed to develop and characterize pullulan/dextran-derived membranes for GBR.

MATERIALS AND METHODS

Two pullulan/dextran-based membranes, containing or not hydroxyapatite (HA) particles, were developed. In vitro, cytotoxicity evaluation was performed using human bone marrow mesenchymal stem cells (hBMSCs). Biocompatibility was assessed on rats in a subcutaneous model for up to 16 weeks. In vivo, rat femoral defects were created on 36 rats to compare the two pullulan/dextran-based membranes with a commercial collagen membrane (Bio-Gide®). Bone repair was assessed radiologically and histologically.

RESULTS

Both polysaccharide membranes demonstrated cytocompatibility and biocompatibility. Micro-computed tomography (micro-CT) analyses at two weeks revealed that the HA-containing membrane promoted a significant increase in bone formation compared to Bio-Gide®. At one month, similar effects were observed among the three membranes in terms of bone regeneration.

CONCLUSION

The developed pullulan/dextran-based membranes evidenced biocompatibility without interfering with bone regeneration and maturation. The HA-containing membrane, which facilitated early bone regeneration and offered adequate mechanical support, showed promising potential for GBR procedures.

The Preparation and Clinical Efficacy of Amnion-Derived Membranes: A Review

Biological tissues from various anatomical sources have been utilized for tissue transplantation and have developed into an important source of extracellular scaffolding material for regenerative medicine applications. Tissue scaffolds ideally integrate with host tissue and provide a homeostatic environment for cellular infiltration, growth, differentiation, and tissue resolution. The human amniotic membrane is considered an important source of scaffolding material due to its 3D structural architecture and function and as a source of growth factors and cytokines. This tissue source has been widely studied and used in various areas of tissue repair including intraoral reconstruction, corneal repair, tendon repair, microvascular reconstruction, nerve procedures, burns, and chronic wound treatment. The production of amniotic membrane allografts has not been standardized, resulting in a wide array of amniotic membrane products, including single, dual, and tri-layered products, such as amnion, chorion, amnion-chorion, amnion-amnion, and amnion-chorion-amnion allografts. Since these allografts are not processed using the same methods, they do not necessarily produce the same clinical responses. The aim of this review is to highlight the properties of different human allograft membranes, present the different processing and preservation methods, and discuss their use in tissue engineering and regenerative applications.

Biological importance of human amniotic membrane in tissue engineering and regenerative medicine

The human amniotic membrane (hAM) is the innermost layer of the placenta. Its distinctive structure and the biological and physical characteristics make it a highly biocompatible material in a variety of regenerative medicine applications. It also acts as a supply of bioactive factors and cells, which indicate the advantages over other tissues. In this review, we firstly discussed the biological properties of hAM-derived cells in vivo or in vitro, along with their stemness of markers, pointing out a promising source of stem cells for regenerative medicine. Then, we systematically summarized current knowledge on the collection, preparation, preservation, and decellularization of hAM, as well as their characteristics helping to improve the understanding of applications in tissue engineering. Finally, we highlighted the recent advances in which hAM has undergone additional modifications to achieve an adequate perspective of regenerative medicine applications. More investigations are required in utilizing appropriate modifications to enhance the therapeutic effectiveness of hAM in the future.

Emerging Strategies for the Biofabrication of Multilayer Composite Amniotic Membranes for Biomedical Applications

The amniotic membrane (AM) is the innermost part of the fetal placenta, which surrounds and protects the fetus. Due to its structural components (stem cells, growth factors, and proteins), AMs display unique biological properties and are a widely available and cost-effective tissue. As a result, AMs have been used for a century as a natural biocompatible dressing for healing corneal and skin wounds. To further increase its properties and expand its applications, advanced hybrid materials based on AMs have recently been developed. One existing approach is to combine the AM with a secondary material to create composite membranes. This review highlights the increasing development of new multilayer composite-based AMs in recent years and focuses on the benefits of additive manufacturing technologies and electrospinning, the most commonly used strategy, in expanding their use for tissue engineering and clinical applications. The use of AMs and multilayer composite-based AMs in the context of nerve regeneration is particularly emphasized and other tissue engineering applications are also discussed. This review highlights that these electrospun multilayered composite membranes were mainly created using decellularized or de-epithelialized AMs, with both synthetic and natural polymers used as secondary materials. Finally, some suggestions are provided to further enhance the biological and mechanical properties of these composite membranes.

Human Acellular Amniotic Membrane as Skin Substitute and Biological Scaffold: A Review of Its Preparation, Preclinical Research, and Clinical Application

Human acellular amniotic membrane (HAAM) has emerged as a promising tool in the field of regenerative medicine, particularly for wound healing and tissue regeneration. HAAM provides a natural biological scaffold with low immunogenicity and good anti-infective and anti-scarring results. Despite its potential, the clinic application of HAAM faces challenges, particularly with respect to the preparation methods and its low mechanical strength. This review provides a comprehensive overview of HAAM, covering its preparation, sterilization, preclinical research, and clinical applications. This review also discusses promising decellularization and sterilization methods, such as Supercritical Carbon Dioxide (SC-CO2), and the need for further research into the regenerative mechanisms of HAAM. In addition, we discuss the potential of HAAM as a skin dressing and cell delivery system in preclinical research and clinical applications. Both the safety and effectiveness of HAAM have been validated by extensive research, which provides a robust foundation for its clinical application.

Positive effect of acellular amniotic membrane dressing with immobilized growth factors in skin wound healing

The human amniotic membrane dressing has been shown to accelerate the wound healing process in the clinic. In this study, heparin was conjugated to a human Acellular Amniotic Membrane (hAAM) to provide affinity binding sites for immobilizing growth factors. To study the acceleration of the wound healing process, we bound epidermal growth factor and fibroblast growth factor 1 to heparinized hAAMs (GF-Hep-hAAMs). The heparinized hAAMs (Hep-hAAMs) were characterized by toluidine blue staining and infrared spectroscopy. The quality control of hAAM was performed by hematoxylin staining, swelling capacity test and biomechanical evaluation. The cytotoxicity, adhesion, and migration in vitro assays of GF-Hep-hAAMs on L-929 fibroblast cells were also studied by MTT assay, scanning electron microscopy, and scratch assay, respectively. Finally, in vivo skin wound healing study was performed to investigate the wound closure rate, re-epithelization, collagen deposition, and formation of new blood vessels. The results showed that GF-Hep-hAAMs enhance the rate of wound closure and epidermal regeneration in BALB/c mice. In conclusion, GF-Hep-hAAMs could accelerate the wound healing process, significantly in the first week.

An in vitro comparison of human corneal epithelial cell activity and inflammatory response on differently designed ocular amniotic membranes and a clinical case study

Amniotic membrane (AM) is a naturally derived biomaterial with biological and mechanical properties important to Ophthalmology. The epithelial side of the AM promotes epithelialization, while the stromal side regulates inflammation. However, not all AMs are equal. AMs undergo different processing with resultant changes in cellular content and structure. This study evaluates the effects of sidedness and processing on human corneal epithelial cell (HCEC) activity, the effect of processing on HCEC inflammatory response, and then a case study is presented. Three differently processed, commercially available ocular AMs were selected: (1) Biovance®3L Ocular, a decellularized, dehydrated human AM (DDHAM), (2) AMBIO2®, a dehydrated human AM (DHAM), and (3) AmnioGraft®, a cryopreserved human AM (CHAM). HCECs were seeded onto the AMs and incubated for 1, 4 and 7 days. Cell adhesion and viability were evaluated using alamarBlue assay. HCEC migration was evaluated using a scratch wound assay. An inflammatory response was induced by TNF-α treatment. The effect of AM on the expression of pro-inflammatory genes in HCECs was compared using quantitative polymerase chain reaction (qPCR). Staining confirmed complete decellularization and the absence of nuclei in DDHAM. HCEC activity was best supported on the stromal side of DDHAM. Under inflammatory stimulation, DDHAM promoted a higher initial inflammatory response with a declining trend across time. Clinically, DDHAM was used to successfully treat anterior basement membrane dystrophy. Compared with DHAM and CHAM, DDHAM had significant positive effects on the cellular activities of HCECs in vitro, which may suggest greater ocular cell compatibility in vivo.

Preparation and Characterization of Polylactic Acid/Nano Hydroxyapatite/Nano Hydroxyapatite/Human Acellular Amniotic Membrane (PLA/nHAp/HAAM) Hybrid Scaffold for Bone Tissue Defect Repair

Bone tissue engineering is a novel and efficient repair method for bone tissue defects, and the key step of the bone tissue engineering repair strategy is to prepare non-toxic, metabolizable, biocompatible, bone-induced tissue engineering scaffolds of suitable mechanical strength. Human acellular amniotic membrane (HAAM) is mainly composed of collagen and mucopolysaccharide; it has a natural three-dimensional structure and no immunogenicity. In this study, a polylactic acid (PLA)/Hydroxyapatite (nHAp)/Human acellular amniotic membrane (HAAM) composite scaffold was prepared and the porosity, water absorption and elastic modulus of the composite scaffold were characterized. After that, the cell-scaffold composite was constructed using newborn Sprague Dawley (SD) rat osteoblasts to characterize the biological properties of the composite. In conclusion, the scaffolds have a composite structure of large and small holes with a large pore diameter of 200 μm and a small pore diameter of 30 μm. After adding HAAM, the contact angle of the composite decreases to 38.7°, and the water absorption reaches 249.7%. The addition of nHAp can improve the scaffold's mechanical strength. The degradation rate of the PLA+nHAp+HAAM group was the highest, reaching 39.48% after 12 weeks. Fluorescence staining showed that the cells were evenly distributed and had good activity on the composite scaffold; the PLA+nHAp+HAAM scaffold has the highest cell viability. The adhesion rate to HAAM was the highest, and the addition of nHAp and HAAM could promote the rapid adhesion of cells to scaffolds. The addition of HAAM and nHAp can significantly promote the secretion of ALP. Therefore, the PLA/nHAp/HAAM composite scaffold can support the adhesion, proliferation and differentiation of osteoblasts in vitro which provide sufficient space for cell proliferation, and is suitable for the formation and development of solid bone tissue.

Reporting Criteria for Clinical Trials on Medication-Related Osteonecrosis of the Jaw (MRONJ): A Review and Recommendations

Medication-related osteonecrosis of the jaw (MRONJ) is a complication caused by anti-resorptive agents and anti-angiogenesis drugs. Since we wanted to write a protocol for a randomized clinical trial (RCT), we reviewed the literature for the essential information needed to estimate the size of the active patient population and measure the effects of therapeutics. At the same time, we designed a questionnaire intended for clinicians to collect detailed information about their practices. Twelve essential criteria and seven additional items were identified and compiled from 43 selected articles. Some of these criteria were incorporated in the questionnaire coupled with data on clinical practices. Our review found extensive missing data and a lack of consensus. For example, the success rate often combined MRONJ stages, diseases, and drug treatments. The occurrence date and evaluation methods were not harmonized or quantitative enough. The primary and secondary endpoints, failure definition, and date coupled to bone measurements were not well established. This information is critical for writing a RCT protocol. With this review article, we aim to encourage authors to contribute all their findings in the field to bridge the current knowledge gap and provide a stronger database for the coming years.

Human amniotic membrane application in oral surgery—An ex vivo pilot study

Objectives: The purpose of this pilot porcine study was to explore and illustrate the surgical application of human amniotic membrane (hAM) in an ex vivo model of medication-related osteonecrosis of the jaw (MRONJ).

Material and methods: Five oral and maxillofacial surgeons participated to this study. MRONJ was simulated on porcine mandible specimens. hAM was applied using four different techniques: implantation with complete coverage, implantation with partial coverage, apposition and covering graft material. At the same time, the surgeons evaluated how well the hAM handled and its physical properties during the surgery.

Results: Surgeons found that hAM had suitable mechanical properties, as it was easy to detach from the support, handle, bind to the defect and bury. hAM was also found to be strong and stable. The “implantation with complete coverage” and “implantation with partial coverage” techniques were the preferred choices for the MRONJ indication.

Conclusion: This study shows that hAM is a graft material with suitable properties for oral surgery. It is preferable to use it buried under the gingiva with sutures above it, which increases its stability. This technical note aims to educate surgeons and provide them with details about the handling of hAM in oral surgery.

Clinical relevance: Two surgical techniques for hAM application in MRONJ were identified and illustrated. hAM handling and physical properties during surgery were reported.

General consensus on multimodal functions and validation analysis of perinatal derivatives for regenerative medicine applications

Perinatal tissues, such as placenta and umbilical cord contain a variety of somatic stem cell types, spanning from the largely used hematopoietic stem and progenitor cells to the most recently described broadly multipotent epithelial and stromal cells. As perinatal derivatives (PnD), several of these cell types and related products provide an interesting regenerative potential for a variety of diseases. Within COST SPRINT Action, we continue our review series, revising and summarizing the modalities of action and proposed medical approaches using PnD products: cells, secretome, extracellular vesicles, and decellularized tissues. Focusing on the brain, bone, skeletal muscle, heart, intestinal, liver, and lung pathologies, we discuss the importance of potency testing in validating PnD therapeutics, and critically evaluate the concept of PnD application in the field of tissue regeneration. Hereby we aim to shed light on the actual therapeutic properties of PnD, with an open eye for future clinical application. This review is part of a quadrinomial series on functional/potency assays for validation of PnD, spanning biological functions, such as immunomodulation, anti-microbial/anti-cancer, anti-inflammation, wound healing, angiogenesis, and regeneration.

Questions about Residual Cell Viability in Cryopreserved Human Amniotic Membrane and Its Impact on Clinical Applications

We questioned the relevance of evaluating residual cell viability in human amniotic membrane (hAM) after its cryopreservation since cell survival is controversial and its ability to act as a matrix (including the presence of growth factors and cytokines) appears to be most important for tissue regeneration purposes. We also discussed the usefulness of osteodifferentiating amniotic cells in whole hAM for bone repair applications. We have evidence that determining residual cell viability after cryopreservation and hAM osteodifferentiation is not justified.

Development of a vascular substitute produced by weaving yarn made from human amniotic membrane

Because synthetic vascular prostheses perform poorly in small-diameter revascularization, biological vascular substitutes are being developed as an alternative. Although their in vivo results are promising, their production involves long, complex, and expensive tissue engineering methods. To overcome these limitations, we propose an innovative approach that combines the human amniotic membrane (HAM), which is a widely available and cost-effective biological raw material, with a rapid and robust textile-inspired assembly strategy. Fetal membranes were collected after cesarean deliveries at term. Once isolated by dissection, HAM sheets were cut into ribbons that could be further processed by twisting into threads. Characterization of the HAM yarns (both ribbons and threads) showed that their physical and mechanical properties could be easily tuned. Since our clinical strategy will be to provide an off-the-shelf allogeneic implant, we studied the effects of decellularization and/or gamma sterilization on the histological, mechanical, and biological properties of HAM ribbons. Gamma irradiation of hydrated HAMs, with or without decellularization, did not interfere with the ability of the matrix to support endothelium formation in vitro. Finally, our HAM-based, woven tissue-engineered vascular grafts (TEVGs) exhibited clinically relevant mechanical properties. Thus, this study demonstrates that human, completely biological, allogeneic, small-diameter TEVGs can be produced from HAM, thereby avoiding costly cell culture and bioreactors.

Tips and Tricks and Clinical Outcome of Cryopreserved Human Amniotic Membrane Application for the Management of Medication-Related Osteonecrosis of the Jaw (MRONJ): A Pilot Study

Medication-related osteonecrosis of the jaw (MRONJ) is a complication of certain pharmacological treatments such as bisphosphonates, denosumab, and angiogenesis inhibitors. There are currently no guidelines on its management, particularly in advanced stages. The human amniotic membrane (hAM) has low immunogenicity and exerts anti-inflammatory, antifibrotic, antimicrobial, antiviral, and analgesic effects. It is a source of stem cells and growth factors promoting tissue regeneration. hAM acts as an anatomical barrier with suitable mechanical properties (permeability, stability, elasticity, flexibility, and resorbability) to prevent the proliferation of fibrous tissue and promote early neovascularization at the surgical site. In oral surgery, hAM stimulates healing and facilitates the proliferation and differentiation of epithelial cells in the oral mucosa and therefore its regeneration. We proposed using cryopreserved hAM to eight patients suffering from cancer (11 lesions) with stage 2–3 MRONJ on a compassionate use basis. A collagen sponge was added in some cases to facilitate hAM grafting. One or three hAMs were applied and one patient had a reapplication. Three patients had complete closure of the surgical site with proper epithelialization at 2 weeks, and two of them maintained it until the last follow-up. At 1 week after surgery, three patients had partial wound dehiscence with partial healing 3 months later and two patients had complete wound dehiscence. hAM reapplication led to complete healing. All patients remained asymptomatic with excellent immediate significant pain relief, no infections, and a truly positive impact on the patients’ quality of life. No adverse events occurred. At 6 months of follow-up, 80% of lesions had complete or partial wound healing (30 and 50%, respectively), while 62.5% of patients were in stage 3. Radiological evaluations found that 85.7% of patients had stable bone lesions (n = 5) or new bone formation (n = 1). One patient had a worsening MRONJ but remained asymptomatic. One patient did not attend his follow-up radiological examination. For the first time, this prospective pilot study extensively illustrates both the handling and surgical application of hAM in MRONJ, its possible association with a collagen sponge scaffold, its outcome at the site, the application of multiple hAM patches at the same time, and its reapplication.

Placental Tissues as Biomaterials in Regenerative Medicine

Placental tissues encompass all the tissues which support fetal development, including the placenta, placental membrane, umbilical cord, and amniotic fluid. Since the 1990s there has been renewed interest in the use of these tissues as a raw material for regenerative medicine applications. Placental tissues have been extensively studied for their potential contribution to tissue repair applications. Studies have attributed their efficacy in augmenting the healing process to the extracellular matrix scaffolds rich in collagens, glycosaminoglycans, and proteoglycans, as well as the presence of cytokines within the tissues that have been shown to stimulate re-epithelialization, promote angiogenesis, and aid in the reduction of inflammation and scarring. The compositions and properties of all birth tissues give them the potential to be valuable biomaterials for the development of new regenerative therapies. Herein, the development and compositions of each of these tissues are reviewed, with focus on the structural and signaling components that are relevant to medical applications. This review also explores current configurations and recent innovations in the use of placental tissues as biomaterials in regenerative medicine.

Cryopreservation of human amniotic membrane for ocular surface reconstruction: a comparison between protocols

PURPOSE

To compare the effects on adhesive and structural properties of newer preservation conditions to those obtained with an established, standardized protocol (dimethyl sulfoxide at -180 °C). In attempt to simplify and enhance the safety of the procedure, we tested dextran-based freezing medium and a dry condition (no medium) at temperatures of -80 °C.

METHODS

Five patches of human amniotic membrane were obtained from three different donors. For each donor, five preservation condition were tested: dimethyl sulfoxide at -180 °C, dimethyl sulfoxide at -80 °C, dextran-based medium at -180 °C, dextran-based medium at -80 °C and dry freezing at -80 °C (no medium). At the end of four months storage period, adhesive properties and structure were analyzed.

RESULTS

None of the newer preservation protocols showed differences in adhesive and structural properties of the tissues. The stromal layer always kept its adhesiveness, while both structure and basement membrane were not altered by any the preservation protocol.

CONCLUSIONS

Switching from liquid nitrogen cryopreservation to -80 °C would reduce manipulation, simplify the procedure, making it also cheaper. The use of dextran-based freezing medium or no medium at all (dry condition) would avoid the potential toxicity of the dimethyl sulfoxide-based freezing media.

Applications of the amniotic membrane in tissue engineering and regeneration: the hundred-year challenge

The amniotic membrane (Amnio-M) has various applications in regenerative medicine. It acts as a highly biocompatible natural scaffold and as a source of several types of stem cells and potent growth factors. It also serves as an effective nano-reservoir for drug delivery, thanks to its high entrapment properties. Over the past century, the use of the Amnio-M in the clinic has evolved from a simple sheet for topical applications for skin and corneal repair into more advanced forms, such as micronized dehydrated membrane, amniotic cytokine extract, and solubilized powder injections to regenerate muscles, cartilage, and tendons. This review highlights the development of the Amnio-M over the years and the implication of new and emerging nanotechnology to support expanding its use for tissue engineering and clinical applications.

Effect of Amniotic Membrane/Collagen-Based Scaffolds on the Chondrogenic Differentiation of Adipose-Derived Stem Cells and Cartilage Repair

Objectives: Repairing articular cartilage damage is challenging. Clinically, tissue engineering technology is used to induce stem cell differentiation and proliferation on biological scaffolds to repair defective joints. However, no ideal biological scaffolds have been identified. This study investigated the effects of amniotic membrane/collagen scaffolds on the differentiation of adipose-derived stem cells (ADSCs) and articular cartilage repair.

Methods: Adipose tissue of New Zealand rabbits was excised, and ADSCs were isolated and induced for differentiation. An articular cartilage defect model was constructed to identify the effect of amniotic membrane/collagen scaffolds on cartilage repair. Cartilage formation was analyzed by imaging and toluene blue staining. Knee joint recovery in rabbits was examined using hematoxylin and eosin, toluidine, safranine, and immunohistochemistry at 12 weeks post-operation. Gene expression was examined using ELISA, RT-PCR, Western blotting, and immunofluorescence.

Results: The adipose tissue was effectively differentiated into ADSCs, which further differentiated into chondrogenic, osteogenic, and lipogenic lineages after 3 weeks’ culture in vitro. Compared with platelet-rich plasmon (PRP) scaffolds, the amniotic membrane scaffolds better promoted the growth and differentiation of ADSCs. Additionally, scaffolds containing the PRP and amniotic membrane efficiently enhanced the osteogenic differentiation of ADSCs. The levels of COL1A1, COL2A1, COL10A1, SOX9, and ACAN in ADSCs + amniotic membrane + PRP group were significantly higher than the other groups both in vitro and in vivo. The Wakitani scores of the ADSC + amniotic membrane + PRP group were lower than that in ADSC + PRP (4.4 ± 0.44**), ADSC + amniotic membrane (2.63 ± 0.38**), and control groups (6.733 ± 0.21) at week 12 post-operation. Osteogenesis in rabbits of the ADSC + amniotic membrane + PRP group was significantly upregulated when compared with other groups. Amniotic membranes significantly promoted the expression of cartilage regeneration-related factors (SOX6, SOX9, RUNX2, NKX3-2, MEF2C, and GATA4). The ADSC + PRP + amniotic membrane group exhibited the highest levels of TGF-β, PDGF, and FGF while exhibiting the lowest level of IL-1β, IL6, and TNF-α in articular cavity.

Conclusion: Amniotic membrane/collagen combination-based scaffolds promoted the proliferation and cartilage differentiation of ADSCs, and may provide a new treatment paradigm for patients with cartilage injury.

Various administration forms of decellularized amniotic membrane extract towards improving corneal repair

Amniotic membrane (AM) transplantation is often used as a treatment for corneal repair, but AM is prone to dissolving and shedding after surgery; multiple transplants will cause pain and financial burden. In this work, human amniotic membrane was firstly decellularized to obtain an AM extracellular matrix (dAM). This dAM was homogenized and extracted to obtain the dAM extract (simplified as dAME). Different forms of administration for corneal injury were performed as liquid drops (diluted dAME), in situ gels (using temperature-dependent Poloxamer 407 as the matrix), and tablets (poly(vinyl alcohol) as the matrix). The cytocompatibility of dAME was evaluated using corneal epithelial cells, corneal stromal cells and fibroblasts as cell models. The results showed that dAME is biocompatible to all these cells. Cells exhibited normal morphology and growth state at a dAME concentration of up to 160 μg mL^-1. In vivo, dAME exhibited increased wound healing efficiency in severe corneal injury, being characterized with a shorter healing time for epithelium and a faster recovery for stromal opacity and thickness, compared with those of the control eyes. Different forms of administration have different effects on corneal repair; among them, in situ gels achieved the best therapeutic efficiency. Their biological mechanism was detected via quantitative real-time polymerase chain reaction (qRT-PCR) technology. It was confirmed that dAME plays important roles in promoting the mRNA expression of leucine-rich and immunoglobulin-like domains 1 (LRIG1) and in inhibiting the mRNA of transforming growth factor-β1 (TGF-β1).

Adipose-Derived Stromal Cells and Mineralized Extracellular Matrix Delivery by a Human Decellularized Amniotic Membrane in Periodontal Tissue Engineering

Periodontitis is a prevalent disease characterized by the loss of periodontal supporting tissues, bone, periodontal ligament, and cementum. The application of a bone tissue engineering strategy with Decellularized Human Amniotic Membrane (DAM) with adipose-derived stromal cells (ASCs) has shown to be convenient and valuable. This study aims to investigate the treatments of a rat periodontal furcation defect model with DAM, ASCs, and a mineralized extracellular matrix (ECM). Rat ASCs were expanded, cultivated on DAM, and with a bone differentiation medium for four weeks, deposited ECM on DAM. Periodontal healing for four weeks was evaluated by micro-computed tomography and histological analysis after treatments with DAM, ASCs, and ECM and compared to untreated defects on five consecutive horizontal levels, from gingival to apical. The results demonstrate that DAM preserves its structure during cultivation and healing periods, supporting cell attachment, permeation, bone deposition on DAM, and periodontal regeneration. DAM and DAM+ASCs enhance bone healing compared to the control on the gingival level. In conclusion, DAM with ASC or without cells and the ECM ensures bone tissue healing. The membrane supported neovascularization and promoted osteoconduction.

Chorion and amnion/chorion membranes in oral and periodontal surgery: A systematic review

The aim of this study was to perform a systematic review on the clinical applications where chorion membrane (CM) and amnion/chorion membrane (ACM) were used for oral tissue regeneration procedures. Selection of articles was carried out by two evaluators in Pubmed and Scopus databases, and Outcomes (PICO) method was used to select the relevant articles. Clinical studies reporting the use of CM or ACM for oral soft and hard tissue regeneration were included. The research involved 21 studies conducted on 375 human patients. Seven clinical applications of CM and ACM in oral and periodontal surgery were identified: gingival recession treatment, intrabony and furcation defect treatment, alveolar ridge preservation, keratinized gum width augmentation around dental implants, maxillary sinus membrane repair, and large bone defect reconstruction. CM and ACM were compared to negative controls (conventional surgeries without membrane) or to the following materials: collagen membranes, dense polytetrafluoroethylene membranes, platelet-rich fibrin membranes, amnion membranes, and to a bone substitute. Several studies support the use of CM and ACM as an efficient alternative to current techniques for periodontal and oral soft tissue regeneration procedures. However, further studies are necessary to increase the level of evidence and especially to demonstrate their role for bone regeneration.

Surgical Application of Human Amniotic Membrane and Amnion-Chorion Membrane in the Oral Cavity and Efficacy Evaluation: Corollary With Ophthalmological and Wound Healing Experiences

Due to its intrinsic properties, there has been growing interest in human amniotic membrane (hAM) in recent years particularly for the treatment of ocular surface disorders and for wound healing. Herein, we investigate the potential use of hAM and amnion-chorion membrane (ACM) in oral surgery. Based on our analysis of the literature, it appears that their applications are very poorly defined. There are two options: implantation or use as a cover material graft. The oral cavity is submitted to various mechanical and biological stimulations that impair membrane stability and maintenance. Thus, some devices have been combined with the graft to secure its positioning and protect it in this location. This current opinion paper addresses in detail suitable procedures for hAM and ACM utilization in soft and hard tissue reconstruction in the oral cavity. We address their implantation and/or use as a covering, storage format, application side, size and number, multilayer use or folding, suture or use of additional protective covers, re-application and resorption/fate. We gathered evidence on pre- and post-surgical care and evaluation tools. Finally, we integrated ophthalmological and wound healing practices into the collected information. This review aims to help practitioners and researchers better understand the application of hAM and ACM in the oral cavity, a place less easily accessible than ocular or cutaneous surfaces. Additionally, it could be a useful reference in the generation of new ideas for the development of innovative protective covering, suturing or handling devices in this specific indication. Finally, this overview could be considered as a position paper to guide investigators to fulfill all the identified criteria in the future.

Applications of Human Amniotic Membrane for Tissue Engineering

An important component of tissue engineering (TE) is the supporting matrix upon which cells and tissues grow, also known as the scaffold. Scaffolds must easily integrate with host tissue and provide an excellent environment for cell growth and differentiation. Human amniotic membrane (hAM) is considered as a surgical waste without ethical issue, so it is a highly abundant, cost-effective, and readily available biomaterial. It has biocompatibility, low immunogenicity, adequate mechanical properties (permeability, stability, elasticity, flexibility, resorbability), and good cell adhesion. It exerts anti-inflammatory, antifibrotic, and antimutagenic properties and pain-relieving effects. It is also a source of growth factors, cytokines, and hAM cells with stem cell properties. This important source for scaffolding material has been widely studied and used in various areas of tissue repair: corneal repair, chronic wound treatment, genital reconstruction, tendon repair, microvascular reconstruction, nerve repair, and intraoral reconstruction. Depending on the targeted application, hAM has been used as a simple scaffold or seeded with various types of cells that are able to grow and differentiate. Thus, this natural biomaterial offers a wide range of applications in TE applications. Here, we review hAM properties as a biocompatible and degradable scaffold. Its use strategies (i.e., alone or combined with cells, cell seeding) and its degradation rate are also presented.

Comparison of amniotic membrane versus the induced membrane for bone regeneration in long bone segmental defects using calcium phosphate cement loaded with BMP-2

Thanks to its biological properties, the human amniotic membrane (HAM) combined with a bone substitute could be a single-step surgical alternative to the two-step Masquelet induced membrane (IM) technique for regeneration of critical bone defects. However, no study has directly compared these two membranes. We first designed a 3D-printed scaffold using calcium phosphate cement (CPC). We assessed its suitability in vitro to support human bone marrow mesenchymal stromal cells (hBMSCs) attachment and osteodifferentiation. We then performed a rat femoral critical size defect to compare the two-step IM technique with a single-step approach using the HAM. Five conditions were compared. Group 1 was left empty. Group 2 received the CPC scaffold loaded with rh-BMP2 (CPC/BMP2). Group 3 and 4 received the CPC/BMP2 scaffold covered with lyophilized or decellularized/lyophilized HAM. Group 5 underwent a two- step induced membrane procedure with insertion of a polymethylmethacrylate (PMMA) spacer followed by, after 4 weeks, its replacement with the CPC/BMP2 scaffold wrapped in the IM. Micro-CT and histomorphometric analysis were performed after six weeks. Results showed that the CPC scaffold supported the proliferation and osteodifferentiation of hBMSCs in vitro. In vivo, the CPC/BMP2 scaffold very efficiently induced bone formation and led to satisfactory healing of the femoral defect, in a single-step, without autograft or the need for any membrane covering. In this study, there was no difference between the two-step induced membrane procedure and a single step approach. However, the results indicated that none of the tested membranes further enhanced bone healing compared to the CPC/BMP2 group.

Use of Amniotic Membrane and Its Derived Products for Bone Regeneration: A Systematic Review

Thanks to their biological properties, amniotic membrane (AM), and its derivatives are considered as an attractive reservoir of stem cells and biological scaffolds for bone regenerative medicine. The objective of this systematic review was to assess the benefit of using AM and amniotic membrane-derived products for bone regeneration. An electronic search of the MEDLINE-Pubmed database and the Scopus database was carried out and the selection of articles was performed following PRISMA guidelines. This systematic review included 42 articles taking into consideration the studies in which AM, amniotic-derived epithelial cells (AECs), and amniotic mesenchymal stromal cells (AMSCs) show promising results for bone regeneration in animal models. Moreover, this review also presents some commercialized products derived from AM and discusses their application modalities. Finally, AM therapeutic benefit is highlighted in the reported clinical studies. This study is the first one to systematically review the therapeutic benefits of AM and amniotic membrane-derived products for bone defect healing. The AM is a promising alternative to the commercially available membranes used for guided bone regeneration. Additionally, AECs and AMSCs associated with an appropriate scaffold may also be ideal candidates for tissue engineering strategies applied to bone healing. Here, we summarized these findings and highlighted the relevance of these different products for bone regeneration.

Decellularized Human Chorion Membrane as a Novel Biomaterial for Tissue Regeneration

Although some placenta-derived products are already used for tissue regeneration, the human chorion membrane (HCM) alone has been poorly explored. In fact, just one study uses decellularized HCM (dHCM) with native tissue architecture (i.e., without extracellular matrix (ECM) suspension creation) as a substrate for cell differentiation. The aim of this work is to fully characterize the dHCM for the presence and distribution of cell nuclei, DNA and ECM components. Moreover, mechanical properties, in vitro biological performance and in vivo biocompatibility were also studied. Our results demonstrated that the HCM was successfully decellularized and the main ECM proteins were preserved. The dHCM has two different surfaces, the reticular layer side and the trophoblast side; and is biocompatible both in vitro and in vivo. Importantly, the in vivo experiments demonstrated that on day 28 the dHCM starts to be integrated by the host tissue. Altogether, these results support the hypothesis that dHCM may be used as a biomaterial for different tissue regeneration strategies, particularly when a membrane is needed to separate tissues, organs or other biologic compartments.

Assessment of fresh and preserved amniotic membrane for guided bone regeneration in mice

Thanks to its biological properties, the human amniotic membrane (HAM) can be used as a barrier membrane for guided bone regeneration (GBR). However, no study has assessed the influence of the preservation method of HAM for this application. This study aimed to establish the most suitable preservation method of HAM for GBR. Fresh (F), cryopreserved (C) lyophilized (L), and decellularized and lyophilized (DL) HAM were compared. The impact of preservation methods on collagen and glycosaminoglycans (GAG) content was evaluated using Masson's trichrome and alcian blue staining. Their suture retention strengths were assessed. In vitro, the osteogenic potential of human bone marrow mesenchymal stromal cells (hBMSCs) cultured on the four HAMs was evaluated using alkaline phosphatase staining and alizarin red quantification assay. In vivo, the effectiveness of fresh and preserved HAMs for GBR was assessed in a mice diaphyseal bone defect after 1 week or 1 month healing. Micro-CT and histomorphometric analysis were performed. The major structural components of HAM (collagen and GAG) were preserved whatever the preservation method used. The tearing strength of DL-HAM was significantly higher. In vitro, hBMSCs seeded on DL-HAM displayed a stronger ALP staining, and alizarin red staining quantification was significantly higher at Day 14. In vivo, L-HAM and DL-HAM significantly enhanced early bone regeneration. One month after the surgery, only DL-HAM slightly promoted bone regeneration. Several preserving methods of HAM have been studied for bone regeneration. Here, we have demonstrated that DL-HAM achieved the most promising results for GBR.