Amnion-derived hydrogels as a versatile platform for regenerative therapy: from lab to market

In recent years, the amnion (AM) has emerged as a versatile tool for stimulating tissue regeneration and has been of immense interest for clinical applications. AM is an abundant and cost-effective tissue source that does not face strict ethical issues for biomedical applications. The outstanding biological attributes of AM, including side-dependent angiogenesis, low immunogenicity, anti-inflammatory, anti-fibrotic, and antibacterial properties facilitate its usage for tissue engineering and regenerative medicine. However, the clinical usage of thin AM sheets is accompanied by some limitations, such as handling without folding or tearing and the necessity for sutures to keep the material over the wound, which requires additional considerations. Therefore, processing the decellularized AM (dAM) tissue into a temperature-sensitive hydrogel has expanded its processability and applicability as an injectable hydrogel for minimally invasive therapies and a source of bioink for the fabrication of biomimetic tissue constructs by recapitulating desired biochemical cues or pre-defined architectural design. This article reviews the multi-functionality of dAM hydrogels for various biomedical applications, including skin repair, heart treatment, cartilage regeneration, endometrium regeneration, vascular graft, dental pulp regeneration, and cell culture/carrier platform. Not only recent and cutting-edge research is reviewed but also available commercial products are introduced and their main features and shortcomings are elaborated. Besides the great potential of AM-derived hydrogels for regenerative therapy, intensive interdisciplinary studies are still required to modify their mechanical and biological properties in order to broaden their therapeutic benefits and biomedical applications. Employing additive manufacturing techniques (e.g., bioprinting), nanotechnology approaches (e.g., inclusion of various bioactive nanoparticles), and biochemical alterations (e.g., modification of dAM matrix with photo-sensitive molecules) are of particular interest. This review article aims to discuss the current function of dAM hydrogels for the repair of target tissues and identifies innovative methods for broadening their potential applications for nanomedicine and healthcare.

Potential Therapeutic Effects of Human Amniotic Epithelial Cells on Gynecological Disorders Leading to Infertility or Abortion

The induction of feto-maternal tolerance, fetal non-immunogenicity, and the regulation of mother's immune system are essential variables in a successful pregnancy. Fetal membranes have been used as a source of stem cells and biological components in recent decades. Human amniotic epithelial cells (hAEC) have stem/progenitor characteristics like those found in the amniotic membrane. Based on their immunomodulatory capabilities, recent studies have focused on the experimental and therapeutic applications of hAECs in allograft transplantation, autoimmune disorders, and gynecological problems such as recurrent spontaneous abortion (RSA), recurrent implantation failure (RIF), and premature ovarian failure (POF). This review discusses some of the immunomodulatory features and therapeutic potential of hAECs in preventing infertility, miscarriage, and implantation failure by controlling the maternal immune system.

Evaluation of the effect of a gel made with amniotic fluid formulation on the healing of diabetic foot ulcers: A triple-blind clinical trial

Aim

The aim of this study was to evaluate the effect of a gel made with amniotic fluid (AF) formulation on wound healing in diabetic foot ulcers.

Methods

This clinical trial was performed on 92 type 2 diabetic patients referring to the Diabetes Clinic of Golestan Hospital of Ahvaz, southwest of Iran in 2019-2020. Patients were randomly divided into three groups of intervention and one placebo group. The wounds of the three intervention groups were dressed with gauze impregnated with an AF formulation gel while wounds of the control group were dressed with plain gauze without any topical agent. Chi-square tests and generalized estimating equations (GEE) with a significance level of 0.05 were used to analyze the data.

Results

At the end of the eighth week of intervention, there was a statistically significant difference among the four groups in terms of wound grade, wound color, condition of the tissues surrounding the wound, the overall condition of the wound, and the duration of wound healing (P < 0.05).

Conclusions

Based on our experience with the patients in the present study, we believe that AF represents a useful and safe option for the treatment of chronic diabetic foot ulcers.

Clinical trial registration

https://en.irct.ir/trial/51551, Identifier: IRCT20201010048985N1.

Comparing the standard surgical dressing with dehydrated amnion and platelet-derived growth factor dressings in the healing rate of diabetic foot ulcer: A randomized clinical trial

AIMS

The management of diabetic foot ulcers is a challenging issue due to the pathophysiological background, delay in healing, and prevalence of diabetes. The purpose of this study was to compare the therapeutic effects of the three methods of diabetic wound care: surgical debridement and dressing, dressing with dehydrated amnion powder, and dressing with platelet-derived growth factor gel.

METHODS

In this multi-arm parallel-group randomized trial, 243 patients with a minimum 4-week medical history of diabetic foot ulcers with Wagner's grades 1 and 2, no infection, and adequate tissue blood flow were randomly assigned to one of three 81-person groups: surgical debridement (the standard method), dehydrated amnion dressing, or platelet-derived growth factor dressing. The follow-up period lasted 12 weeks. The percentage area reduction (PAR) was measured as the final target. SPSS version 25 was used to perform statistical analysis on the data.

RESULTS

All three study groups were comparable in terms of the type of ulcer, the area of ulcer, Wagner's grade, the period, and the ulcer's size. The PAR in the surgical debridement, platelet-derived growth factor, and dehydrated amnion groups were 7.4%, 14.8%, and 49.3% in week 4; 20.1%, 35.8%, and 79% in week 6; 43.7%, 56.8%, 86.4% in week 8; and 50%, 61.7%, and 87.6% in weeks 10 and 12, respectively. The observed differences were statistically significant (p < 0.05) over the entire period.

CONCLUSION

The study concluded that dehydrated amnion dressing, when compared to platelet-derived growth factor dressing and surgical debridement, resulted in better-improved healing in diabetic foot ulcer patients.

The healing dynamics of non-healing wounds using cryo-preserved amniotic membrane

We evaluated the effect of the application of cryo‐preserved amniotic membrane on the healing of 26 non‐healing wounds (18 patients) with varying aetiologies and baseline sizes (average of 15.4 cm²), which had resisted the standard of care treatment for 6 to 456 weeks (average 88.8 weeks). Based on their average general responses to the application of cryo‐preserved AM, we could differentiate three wound groups. The first healed group was characterised by complete healing (100% wound closure, maximum treatment period 38 weeks) and represented 62% of treated wounds. The wound area reduction of at least 50% was reached for all wounds in this group within the first 10 weeks of treatment. Exactly 19% of the studied wounds responded partially to the treatment (partially healed group), reaching less than 25% of closure in the first 10 weeks and 90% at maximum for extended treatment period (up to 78 weeks). The remaining 19% of treated wounds did not show any reaction to the AM application (unhealed defects). The three groups have different profiles of wound area reduction, which can be used as a guideline in predicting the healing prognosis of non‐healing wounds treated with a cryo‐preserved amniotic membrane.

Healing hard-to-heal diabetic foot ulcers: the role of dehydrated amniotic allograft with cross-linked bovine-tendon collagen and glycosaminoglycan matrix

The treatment of diabetic foot ulcers is complex and costly with an increased risk for infection, which may even lead to amputation. This prospective case series aims to assess the effectiveness of a dehydrated amniotic membrane allograft combined with a bilayer dermal matrix for healing complicated foot ulcers in patients with comorbidities. A total of six patients with complicated full-thickness ulcers and comorbidities, such as diabetes and peripheral vascular disease were treated with this technique. Each wound was measured intraoperatively just before graft application, at 14 days after application, and then at weeks 4, 8, and 12. Changes in wound volume and area were compared over time. One patient had complete wound closure by week eight, a second patient by week 12. The other four patients had wounds that decreased in size during the course of 12 weeks. The mean decrease in wound volume was 73.5% post-removal of the bilayer dermal matrix after two weeks of application. At week 12, the mean decrease in wound area and volume were 93.2% and 97.1%, respectively. This case series provides initial evidence that the combination of dehydrated amniotic membrane allograft with bilayer dermal matrix promotes complete wound closure in patients with comorbidities that may impede wound healing. Further clinical trials are needed to confirm these results.

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.

Human Amnion Chorion Membrane Allografts in the Treatment of Chronic Diabetic Foot Ulcers: A Literature Review

OBJECTIVE

To discuss human amnion chorion (placental) membrane allograft (HACMA) use for the treatment of chronic diabetic foot ulcers (DFUs) and to evaluate the effectiveness, cost, and product waste of this therapy.

DATA SOURCES

PubMed, Cochrane, and OVID databases.

STUDY SELECTION

Twenty-four articles pertaining to HACMA and DFUs published from 2016 to 2020 were selected.

DATA EXTRACTION

The data collected included type of wound care product, study design, study size, baseline size of DFU, cost, product wastage, number of applications, and wound healing outcomes.

DATA SYNTHESIS

Human amnion chorion membrane allografts in the treatment of chronic DFUs have led to a reduction in healing time and increased the overall percentage of healing, making them more effective in treating DFUs compared with standard of care. These products are offered in multiple sizes with various shelf lives and methods of storage, making them accessible, easy to use, less wasteful, and lower in cost compared with other commercially available products. Promising evidence demonstrates that HACMAs are beneficial in treating complex, high-grade DFUs with exposed tendon or bone.

CONCLUSIONS

Human amnion chorion membrane allografts are effective in treating chronic DFUs with a greater percentage of complete wound closure and a reduction in healing time versus standard of care.

Systematic review on the rational use of amniotic membrane allografts in diabetic foot ulcer treatment

Background

Diabetic foot ulcer is a complication with multiple aetiological factors which has a significant impact to patients’ lives and costs to the healthcare system. The potential of human amniotic membrane to act as an allograft has been studied in relation to this condition. Aim of this study is to evaluate the current scientific evidence on its effectiveness in healing diabetic foot ulcers.

Methods

Pubmed, Cochrane library, and Google scholar were searched using the search terms, “Amnion” OR “Placenta” AND “Diabetic foot”. (MeSH terms) in the title or the abstract field from 1st of January 2000 to 30th March 2020. The quality of published reports was assessed using standard methods. We searched for experimental and observational studies in terms of randomized control trials, prospective cohort, retrospective cohort studies and case series.

Results

When searched with Mesh terms, 12 citations in PubMed, 22 citations in Cochrane library and 30 in other data bases were found. After screening the studies and their reference lists, 12 studies met the inclusion criteria and the others were excluded. There were 8 randomized control trials (RCTs), 2 prospective studies and 2 retrospective studies employing different preparation methods of the amniotic membranes. A wide variation in study end points were noted. Majority of the RCTs (n = 7) were concluded with significantly higher wound closure rate compared to the conventional treatment groups. In prospective and retrospective studies, it was shown that large chronic ulcers which were resistant to closure with standard therapy achieved wound closure with amniotic membrane allografts. A meta-analysis could not be performed due to study heterogeneity, and publication bias was not assessed due to the small number of available studies which was not sufficient for accurate comparison.

Conclusion

Even though, the studies had some inherent heterogeneity due to different preparation methods, different study end points and outcome measurements. According to our review the current studies using amniotic membrane allografts give reliable evidence of reduction in healing time over conventional methods.

Biological characterization of dehydrated amniotic membrane allograft: Mechanisms of action and implications for wound care

There is a growing clinical demand in the wound care market to treat chronic wounds such as diabetic foot ulcers. Advanced cell and tissue-based products (CTPs) are often used to address challenging chronic wounds where healing has stalled. These products contain active biologics such as growth factors and cytokines as well as structural components that support and stimulate cell growth and assist in tissue regeneration. This study addresses the in vitro biologic effects of a clinically available dehydrated amniotic membrane allograft (DAMA). The broad mechanism of action results from DAMA's biologic composition that leads to stimulation of cell migration cell proliferation, and reduction of pro-inflammatory cytokines. Results show that DAMA possesses growth factors and cytokines such as EGF, FGF, PDGFs, VEGF, TGF-β, IL-8, and TIMPs 1 and 2. Furthermore, in vitro experiments demonstrate that DAMA stimulates cell proliferation, cell migration, secretion of collagen type I, and the reduction of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. This study findings are consistent with the clinical benefits previously published for DAMA and other CTPs in chronic wounds suggesting that the introduction of DAMA to non-healing, complex wounds helps to improve the wound milieu by providing essential structural components, cytokines, and growth factors to create an appropriate environment for wound healing.

Therapeutic Potential of Human Amniotic Epithelial Cells on Injuries and Disorders in the Central Nervous System

Despite recent advances in neurosurgery and pharmaceuticals, contemporary treatments are ineffective in restoring lost neurological functions in patients with injuries and disorders of the central nervous system (CNS). Therefore, novel and effective therapies are urgently needed. Recent studies have indicated that stem cells, including embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs), could repair/replace damaged or degenerative neurons and improve functional recovery in both preclinical and clinical trials. However, there are many unanswered questions and unsolved issues regarding stem cell therapy in terms of potency, stability, oncogenicity, immune response, cell sources, and ethics. Currently, human amniotic epithelial cells (hAECs) derived from the amnion exhibit considerable advantages over other stem cells and have drawn much attention from researchers. hAECs are readily available, pose no ethical concerns, and have little risk of tumorigenicity and immunogenicity. Mounting evidence has shown that hAECs can promote neural cell survival and regeneration, repair affected neurons, and reestablish damaged neural connections. It is suggested that hAECs may be the most promising candidate for cell-based therapy of neurological diseases. In this review, we mainly focus on recent advances and potential applications of hAECs for treating various CNS injuries and neurodegenerative disorders. We also discuss current hurdles and challenges regarding hAEC therapies.

Advances in perinatal stem cells research: a precious cell source for clinical applications

Perinatal tissues possess numerous types of stem (stromal) cells, which are considered effective candidates for cell therapy. These tissues possess common characteristics of both embryonic and adult stem cells, and cell therapists have begun to use perinatal stem cells to treat several diseases. Despite their benefits, these cells are considered biological waste and usually discarded after delivery. This review highlights the characteristics and potential clinical applications in regenerative medicine of perinatal stem cell sources - cord blood hematopoietic stem cells, umbilical cord mesenchymal stem cells, amniotic membrane stem cells, amniotic fluid stem cells, amniotic epithelial cells and chorionic mesenchymal stem cells.

Experience in Using Fetal Membranes: The Present and New Perspectives

INTRODUCTION

The placenta is an accessible source of tissues for transplantation. Placental transplants have been used in wound treatment because of the basic function of the placenta and its nutritious properties and structure.

PATIENTS AND METHODS

The aim of this work is to present the clinical usage of fetal membranes, including human amnion, on the basis of the burn treatment center's experience. The clinical use of amnion and different types of placental transplants are described. The initial results of research work within the MEDPIG project are presented regarding the application of placenta from transgenic pigs as a source of tissues for transplantation.

RESULTS

From August 2011 to March 2017, 252,592 cm² of biostatic human amnion transplants were prepared in our tissue bank. During this period they were transplanted to 528 patients, including 10 patients with Lyell syndrome. Initial studies were conducted in which placentas were collected from 5 transgenic pigs and 27,426 cm² of amniotic grafts were prepared from them.

DISCUSSION

The authors' own experience as well as the literature confirm the extraordinary efficiency of transplants prepared from placental tissues, especially from the amniotic membrane.

CONCLUSIONS

The clinical effects confirm the effectiveness of using human amnion in wound treatment. Amniotic transplant is a new treatment standard in toxic epidermal necrolysis TEN (Lyell's syndrome), which has found confirmation in very good clinical outcomes. The collected placentas from transgenic animals enabled the preparation of significantly more grafts than in the case of human material, which is a great advantage of this source of placenta over human tissues.

Efficacy and Time Sensitivity of Amniotic Membrane treatment in Patients with Diabetic Foot Ulcers: A Systematic Review and Meta-analysis

INTRODUCTION

Diabetic foot ulcers (DFUs) are complex chronic wounds which have a major long-term impact on the morbidity, mortality and quality of patients. The objective of this study was to assess the efficacy and time sensitivity of human amnion/chorion membrane treatment in patients with chronic DFUs.

METHODS

The Cochrane Library, PubMed, Embase and Web of Science databases were systematically searched to identify relevant articles up to 10 April 2017. All randomized controlled trials (RCTs) comparing human amnion/chorion membrane + standard therapy and standard therapy alone in patients with DFUs were included in the analysis. Eligible studies were reviewed and data extracted into standard form. The Cochrane Collaboration's tool for assessing the risk of bias was used. Review manager version 5.3 software was used for statistical analysis. Data were analyzed using a random effect model.

RESULTS

Overall, the initial search of the four databases identified 352 published studies; of these, seven RCTS were ultimately included in the meta-analysis. The overall test effect in the group assessed at 4 weeks was Z = 4.14 [P < 0.0001; odds ratio (OR) 0.05; 95% confidence interval (CI) 0.01-0.21]. The overall test effect in the group assessed at 6 weeks was Z = 4.28 (P < 0.0001; OR 0.07; 95% CI 0.02-0.23). The overall effect in the group assessed at 12 weeks was Z = 4.96 (P < 0.00001; OR 0.10; 95% CI 0.04-0.24. The results showed that patients receiving amniotic membrane + standard therapy had far fewer incomplete healing wounds than those receiving standard of care alone. Assessment of the wound healing state at 4 and 6 weeks revealed that the wound healing state was almost the same, but there was a net difference of wound healing state at 12 weeks.

CONCLUSION

Human amnion/chorion membrane + standard of care treatment heals DFUs significantly faster than standard of care alone. When using the amnion in patients with DFUs, the optimal times to assess progress in wound healing should be 4 and 12 weeks.