Evaluation of human amniotic membrane as a wound dressing for split-thickness skin-graft donor sites

Advanced Biomaterials and Topical Medications for Treating Diabetic Foot Ulcers: A Systematic Review and Network Meta-Analysis

Significance: With the increasing diabetic population worldwide, diabetic foot ulcers (DFUs) are a significant concern. This study aimed to compare the efficacy of skin substitutes, biomaterials, and topical agents with standard care. Recent Advances: A meta-analysis was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed, EMBASE, and Web of Science were searched using the following keywords: diabetes mellitus AND skin graft OR tissue replacement OR dressing OR drug. Two independent reviewers performed data collection and quality assessment of the eligible studies. The primary outcome was the 12- to 16-week healing rates and the secondary outcome was recurrence rates. Critical Issues: Thirty-eight randomized controlled trials, including 3,862 patients, were analyzed. The studies exhibited low heterogeneity (τ2 = 0.10) without significant asymmetry (Egger's test, p = 0.8852). After pooling direct and indirect estimates, placenta-based tissue products exhibited the best wound healing probability (p-score = 0.90), followed by skin substitutes with living cells (p-score = 0.70), acellular skin substitutes (p-score = 0.56), and advanced topical dressings (p-score = 0.34) compared with standard of care. The recurrence analysis showed significant improvement in the intervention group compared with the control group (11.21% vs. 15.15%). Future Directions: This network meta-analysis provides the relative effectiveness and rank of biomaterials and topical dressings in DFU healing. The results could help clinical decision making.

A Prospective Multicenter Study of a Weekly Application Regimen of Viable Human Amnion Membrane Allograft in the Management of Nonhealing Diabetic Foot Ulcers

Background

Diabetic foot ulcers (DFUs) pose a significant clinical challenge for providers and patients, and often precede devastating complications such as infection, hospitalization, and amputation. Therefore, advanced treatment options are needed to facilitate the healing of chronic DFUs and improve outcomes in this high-risk population. Cryopreserved viable human amnion membrane allograft (vHAMA) has shown great promise in the treatment of recalcitrant DFUs as a supplement to standard of care (SOC). Placental grafts are rich in extracellular matrix proteins, growth factors, and cytokines, which can induce angiogenesis and dermal fibroblast proliferation, resulting in accelerated healing.

Methods

In this prospective, multicenter single arm trial, 20 patients with nonhealing DFUs received weekly application of vHAMA, in addition to SOC, for up to 12 weeks. The primary study endpoint was proportion of healed wounds at 12 weeks. Secondary endpoints included proportion of wounds healed at 6 weeks, time to heal, and percentage area wound reduction. Subjects were evaluated for ulcer healing and assessed for adverse events at every treatment visit.

Results

At study conclusion, 85% of patients receiving vHAMA healed. Ten wounds healed (50%) by 6 weeks, and 17 wounds (85%) healed by 12 weeks. The mean time to heal was 46.6 days (95% CI: 35.1-58.0), and the average number of vHAMAs used was 5.4 (SD: 3.25). The mean PAR was 86.3% (SD: 40.51).

Conclusions

Aseptically processed, cryopreserved vHAMA should be considered as a safe and effective option for DFUs refractory to SOC therapy.

Outcome of Application of Cryopreserved Amniotic Membrane Grafts in the Treatment of Chronic Nonhealing Wounds of Different Origins in Polymorbid Patients: A Prospective Multicenter Study

To compare the therapeutic efficacy of cryopreserved amniotic membrane (AM) grafts and standard of care (SOC) in treating nonhealing wounds (NHW) through a prospective multicenter clinical trial, 42 patients (76% polymorbid) with 54 nonhealing wounds of various etiologies (mainly venous) and an average baseline size of 20 cm2 were included. All patients were treated for at least 6 weeks in the center before they were involved in the study. In the SOC group, 29 patients (36 wounds) were treated. If the wound healed less than 20% of the baseline size after 6 weeks, the patient was transferred to the AM group (35 patients, 43 wounds). Weekly visits included an assessment of the patient's condition, photo documentation, wound debridement, and dressing. Quality of life and the pain degree were subjectively reported by patients. After SOC, 7 wounds were healed completely, 1 defect partially, and 28 defects remained unhealed. AM application led to the complete closure of 24 wounds, partial healing occurred in 10, and 9 remained unhealed. The degree of pain and the quality of life improved significantly in all patients after AM application. This study demonstrates the effectiveness of cryopreserved AM grafts in the healing of NHW of polymorbid patients and associated pain reduction.

Investigating the joint application of negative pressure wound treatment and tissue therapy for chronic wounds in patients with diabetes

This study aimed to investigate the effectiveness of combined negative pressure wound therapy (NPWT) and human amniotic membrane in patients with chronic wounds associated with diabetes. A total of five patients with type 2 diabetes, including ischemic and mixed forms of diabetic foot syndrome, presenting with ischemic wounds of the lower extremities were included in this study. Patients with uncorrected limb ischemia were excluded. The treatment protocol included diabetes compensation (treatment with fractional insulin therapy), anticoagulant, metabolic therapy and angiotropic therapy, physical treatment methods, osteoporosis therapy with calcium preparations, and wound-specific interventions. The primary treatment approach involved the application of a vacuum bandage to the transplanted human amniotic membrane, which improved the adaptation of the flap to the wound surface, allowed the removal of excess wound exudate, and stimulated angiogenesis and reparative properties. The combined approach of NPWT and biotherapy was a safe and effective cure for diabetic wounds, promoting faster wound healing, reducing the need for autodermoplasty, and possibly reducing the necessity for high-level amputations.

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

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

Preparation of human amniotic membrane for transplantation in different application areas

The human amniotic membrane (hAM) is the inner layer of the placenta and plays protective and nutritional roles for the fetus during pregnancy. It contains multiple growth factors and proteins that mediate unique regenerative properties and enhance wound healing in tissue regeneration. Due to these characteristics hAM has been successfully utilized in ophthalmology for many decades. This material has also found application in a variety of additional therapeutic areas. Particularly noteworthy are the extraordinary effects in the healing of chronic wounds and in the treatment of burns. But hAM has also been used successfully in gynecology, oral medicine, and plastic surgery and as a scaffold for in vitro cell culture approaches. This review aims to summarize the different graft preparation, preservation and storage techniques that are used and to present advantages and disadvantages of these methods. It shows the characteristics of the hAM according to the processing and storage methods used. The paper provides an overview of the currently mainly used application areas and raises new application possibilities. In addition, further preparation types like extracts, homogenates, and the resulting treatment alternatives are described.

The importance of inflammation control for the treatment of chronic diabetic wounds

Diabetic chronic wounds cause massive levels of patient suffering and economic problems worldwide. The state of chronic inflammation arises in response to a complex combination of diabetes mellitus-related pathophysiologies. Advanced treatment options are available; however, many wounds still fail to heal, exacerbating morbidity and mortality. This review describes the chronic inflammation pathophysiologies in diabetic ulcers and treatment options that may help address this dysfunction either directly or indirectly. We suggest that treatments to reduce inflammation within these complex wounds may help trigger healing.

The Effects of Zataria multiflora Cream on Split-Thickness Skin Graft Donor-Site Management: A Randomized, Blinded, Placebo-Controlled Study

Purpose: The wound healing process involves a complex series of biological events. Skin grafts have several uses as a reconstructive method. There are several dressings for the skin graft donor site, but the optimum dressing agents that provide all the requirements at the same time are unclear. This prospective, randomized, placebo-controlled clinical trial aimed to evaluate the therapeutic effect of Zataria multiflora cream in the wound healing process of partial-thickness skin graft donor sites and compared it with a placebo. Materials and Methods: This clinical trial study was performed on patients who underwent split-thickness skin grafts. Enrolled patients applied Z. multiflora cream and placebo controlled (petrolatum ointment) twice a day, from the day of intervention at the skin graft donor sites in two parts, separately. On 7, 14, 21, and 28 days after surgery, the wound healing process was evaluated, photographed, and scored according to the Bates-Jensen assessment tool. Evidence of infection was evaluated. The main agent and placebo were compared during the wound healing process. Results: Decreases in wound surface area and total score were significantly greater in the Z. multiflora group (p < 0.05). The wounds of 30% of patients in the second week and 90% of patients in the third week were completely epithelialized in the Z. multiflora group. These values were 3.3% and 36.7% for the control group, respectively, and so, the healing rate was ∼9-fold in the second week and 2.45-fold in the third week in the Z. multiflora group compared with the control group (p < 0.05). Conclusion: Wound healing and reepithelialization accelerated significantly in the first, second, third, and fourth week after intervention in the Z. multiflora treatment group, due to modulating the inflammatory phase and improving the proliferative phase. Clinical Trial Registration Number: IRCT20210624051695N1.

A comprehensive review on methods for promotion of mechanical features and biodegradation rate in amniotic membrane scaffolds

Amniotic membrane (AM) is a biological tissue that surrounds the fetus in the mother's womb. It has pluripotent cells, immune modulators, collagen, cytokines with anti-fibrotic and anti-inflammatory effect, matrix proteins, and growth factors. In spite of the biological characteristics, some results have been released in preventing the adhesion on traumatized surfaces. Application of the AM as a scaffold is limited due to its low biomechanical resistance and rapid biodegradation. Therefore, for using the AM during surgery, its modification by different methods such as cross-linking of the membrane collagen is necessary, because the cross-linking is an effective way to reduce the rate of biodegradation of the biological materials. In addition, their cross-linking is likely an efficient way to increase the tensile properties of the material, so that they can be easily handled or sutured. In this regard, various methods related to cross-linking of the AM subsuming the composite materials, physical cross-linking, and chemical cross-linking with the glutraldehyde, carbodiimide, genipin, aluminum sulfate, etc. are reviewed along with its advantages and disadvantages in the current work.

Human Amniotic Epithelial Cells Secretome: Components, Bioactivity, and Challenges

Human amniotic epithelial cells (hAECs) derived from placental tissue have received significant attention as a promising tool in regenerative medicine. Several studies demonstrated their anti-inflammatory, anti-fibrotic, and tissue repair potentials. These effects were further shown to be retained in the conditioned medium of hAECs, suggesting their paracrine nature. The concept of utilizing the hAEC-secretome has thus evolved as a therapeutic cell-free option. In this article, we review the different components and constituents of hAEC-secretome and their influence as demonstrated through experimental studies in the current literature. Studies examining the effects of conditioned medium, exosomes, and micro-RNA (miRNA) derived from hAECs are included in this review. The challenges facing the application of this cell-free approach will also be discussed based on the current evidence.

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.

Effect of dermal fibroblasts and mesenchymal stem cells seeded on an amniotic membrane scaffold in skin regeneration: A case series

BACKGROUND

Skin wound healing has always been a challenging subject as it involves the coordinated functioning of various cells and molecules. Any disorder in wound healing can cause healing failure and result in chronic wounds. In this study, we hypothesized that co-cultured dermal fibroblasts (DFs) and Wharton's jelly mesenchymal stem cells (WJ-MSCs) seeded on an acellular amniotic membrane scaffold could be used to promote skin regeneration in chronic ulcers.

MATERIALS AND METHODS

In this case series, the chronic wounds of five diabetic patients aged between 30 and 60 years were treated with co-cultured WJ-MSCs and DFs seeded on an acellular amniotic membrane. Treatment was applied and the wound healing process was evaluated every three days for nine days, with the patients being subsequently followed up for one month. The wound healing percentage, time taken for the wound to heal, and wound size were monitored.

RESULTS

The mean wound healing rate (WHR) increased progressively in all lesions. The mean percentage of wound healing after transplantation of the biological scaffold enriched with WJ-MSCs and autologous DFs after treatment was 93.92%, respectively. The healing percentage significantly increased after three days; significant decreases in wound size and healing time were recorded after six and nine days of treatment, respectively (p < 0.002); and total skin regeneration and re-epithelialization were achieved by the ninth day of treatment. There were no side effects or complications.

CONCLUSION

Given the current problems and complications presented by chronic wounds, Novel Clinical approaches involving cell therapy and tissue engineering can be regarded as an attractive therapeutic option for the treatment of chronic and difficult-to-heal wounds.

Split-thickness skin graft donor-site morbidity: A systematic literature review

The purpose of this systematic literature review is to critically evaluate split-thickness skin graft (STSG) donor-site morbidities. The search of peer-reviewed articles in three databases from January 2009 to July 2019 identified 4271 English-language publications reporting STSG donor-site clinical outcomes, complications, or quality of life. Of these studies, 77 met inclusion criteria for analysis. Mean time to donor-site epithelialization ranged from 4.7 to 35.0 days. Mean pain scores (0-10 scale) ranged from 1.24 to 6.38 on postoperative Day 3. Mean scar scores (0-13 scale) ranged from 0 to 10.9 at Year 1. One study reported 28% of patients had donor-site scar hypertrophy at 8 years. Infection rates were generally low but ranged from 0 to 56%. Less frequently reported outcomes included pruritus, wound exudation, and esthetic dissatisfaction. Donor-site wounds underwent days of wound care and were frequently associated with pain and scarring. Widespread variations were noted in STSG donor-site outcomes likely due to inconsistencies in the definition of outcomes and utilization of various assessment tools. Understanding the true burden of donor sites may drive innovative treatments that would reduce the use of STSGs and address the associated morbidities.

Biological versus non-biological dressings in the management of split-thickness skin-graft donor sites: a systematic review and meta-analysis

OBJECTIVE

There are currently no definitive guidelines regarding the management of split-thickness skin-graft (STSG) donor sites. The literature reports biological and non-biological dressings as the two main groups; however, there is no conclusive evidence regarding the ideal type. A systematic review and meta-analysis of existing clinical trials was performed to compare biological and non-biological dressings in managing STSG donor sites.

METHOD

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement standards was used to conduct this study. Electronic databases including MEDLINE, Embase, CINAHL and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched by two authors (SR and BL). Data analysis was performed with RevMan 5.3.

RESULTS

In total, 10 studies, consisting of eight randomised controlled trials and two observational assessments, were identified. Wound healing time was faster with biological dressings compared to non-biological dressings (mean difference -5.44 days; p<0.05). A higher epithelialisation rate was also noted for biological dressings. There was no difference in the infection rate between the two study groups (odds ratio [OR] 0.39; 95% confidence interval [CI] 0.15-1.04) or wound exudation (OR 0.31; 95% CI 0.01-8.28). The pain level experienced during dressing changes in both groups was reported to be similar.

CONCLUSION

The rate of epithelialisation and wound healing is greater for STSG donor sites when treated with biological dressings, but they offer no difference in terms of reducing pain, limiting infection or exudation.

Development of Contact Lens-Shaped Crosslinked Amniotic Membranes for Sutureless Fixation in the Treatment of Ocular Surface Diseases

Purpose

To develop a new method of manufacturing contact lens-shaped crosslinked amniotic membranes (AMs) using glutaraldehyde (GA) and dialdehyde starch (DAS) as crosslinking agents.

Methods

Amniotic membranes were placed on a curved plastic mold and crosslinked with either 4.5% DAS or 1% GA, after which their physical properties and biological safety were evaluated.

Results

The tensile strength of the GA- and DAS-crosslinked samples was much increased compared with that of normal AMs. Neither crosslinking process affected AM transparency. Although the GA-crosslinked AM showed better enzymatic resistance, its physiological structure was severely damaged after the crosslinking process. On the other hand, compared with the GA-crosslinked AM, the DAS-crosslinked AM showed higher growth factor concentrations and better biocompatibility, similar to normal AMs. In addition, the DAS-crosslinked AM was effective in the recovery of corneal epithelial wounds and was well maintained over 3 days without decentration or degradation on the ocular surface in human subjects.

Conclusions

Contact lens-shaped AMs were successfully prepared with crosslinking agents. Crosslinking with DAS did not affect the structural properties or biological activity of the AMs, and the improved mechanical properties helped the AM to maintain its curved shape. This crosslinking method allowed us to transplant AMs into patients’ eyes without sutures.

Translational Relevance

Sutureless fixation of contact lens-shaped AMs would be very convenient and safe for the treatment of corneal surface disease.

The Healing Effect of Amniotic Membrane in Laryngeal Defects in Rabbit Model

OBJECTIVE

Fibrosis and scar formation following laryngeal repairing is a major concern. This study evaluated the efficacy of applying amniotic membrane (AM) as a biologic dressing to reduce fibrosis and inflammation and promote cartilage repair.

STUDY DESIGN

Experimental animal study.

METHODS

Nine male white Dutch rabbits were selected. A standard defect (5 mm) was created in right and left thyroid lamina. In the right side, two layers of AM were applied while the left side was kept intact for future comparison. Histologic examination with criteria of inflammation, fibrosis, and cartilage regeneration was performed 2, 4, and 6 weeks following AM application. All procedures were done according to animal ethics rules.

RESULTS

Histologic and gross examination showed that AM application was able to reduce inflammation and fibrosis and improve cartilage regeneration significantly.

CONCLUSION

As a useful intervention, AM application can reduce inflammation and fibrosis and enhance cartilage regeneration, following laryngeal defect repair.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:E527-E533, 2021.

Hyaluronic Acid (HA)-Based Silk Fibroin/Zinc Oxide Core-Shell Electrospun Dressing for Burn Wound Management

Burn injuries represent a major life-threatening event that impacts the quality of life of patients, and places enormous demands on the global healthcare systems. This study introduces the fabrication and characterization of a novel wound dressing made of core-shell hyaluronic acid-silk fibroin/zinc oxide (ZO) nanofibers for treatment of burn injuries. The core-shell configuration enables loading ZO-an antibacterial agent-in the core of nanofibers, which in return improves the sustained release of the drug and maintains its bioactivity. Successful formation of core-shell nanofibers and loading of zinc oxide are confirmed by transmission electron microscopy, Fourier-transform infrared spectroscopy, and energy dispersive X-ray. The antibacterial activity of the dressings are examined against Escherichia coli and Staphylococcus aureus and it is shown that addition of ZO improves the antibacterial property of the dressing in a dose-dependent fashion. However, in vitro cytotoxicity studies show that high concentration of ZO (>3 wt%) is toxic to the cells. In vivo studies indicate that the wound dressings loaded with ZO (3 wt%) substantially improves the wound healing procedure and significantly reduces the inflammatory response at the wound site. Overall, the dressing introduced herein holds great promise for the management of burn injuries.

Human Amniotic Membrane: A New Option for Graft Donor Sites - Systematic Review and Meta-analysis

There are currently no standardised guidelines on the optimum dressing used for graft donor sites. The aim was to compare the outcomes of human amniotic membrane (HAM) vs routine dressings in split-thickness skin graft (STSG) donor site healing. A systematic review and meta-analysis was performed and a search of electronic information was conducted to identify all randomised controlled trials comparing the outcomes of HAM vs routine dressings in STSG donor sites. Wound healing and infection rate were primary outcome measures. Secondary outcome measures included severity of pain, discharge from donor site, the number of dressing changes, pruritus, and comfort. Fixed effect modelling was used for the analysis. Four studies enrolling 157 patients were identified. There was a significant difference between HAM and routine groups with wound healing time (P < .0001) and proportion of wounds healed by day 12 (P = .01). There was no significant difference between the two groups in infection rates (P = .27). For all secondary outcomes, HAM had improved results. HAM dressings are a superior option when compared with routine dressings used in current clinical practice for STSG donor sites as they improve wound healing and do not increase the infection rate.

Evaluation of Tissue-engineered Skin on Base of Human Amniotic Membrane for Wound Healing

Human amniotic membranes (hAMs) have shown promising results in recent studies aimed at improving wound healing through several mechanisms. We wanted to investigate its properties as a scaffold by adding autologous cells to treat full-thickness skin defects and hypothesized that recultivated hAM would show an even improved wound healing by accelerating the epidermal closure of the wound.

Gamma-treated placental amniotic membrane allograft as the adjuvant treatment of unresponsive diabetic ulcer of the foot

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Unresponsive diabetic ulcer is ulcer that does not reduce in size within a month.

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It is caused by senescent cells, absence of growth factors, and other cellular abnormalities.

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To maximize wound healing, skin substitute can be used to prevent infection and dessication.

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Amniotic membrane favoured healing of unresponsive and non-healing ulcers.

Introduction

Diabetic ulcer of the foot is a major cause of morbidity and is a leading cause of hospitalization in patients with diabetes, and causes productivity and financial losses that lower the quality of life of the patient. The wound is categorized as responsive and unresponsive wound, which occurs in debilitated patients as seen in diabetes mellitus. The delay in wound repair can be caused by senescent cells, absence of growth factors, and other cellular abnormalities.

Method

This is a retrospective, single-centre case series with non-consecutive cases. Patients with diabetic ulcer of the foot managed using gamma-treated placental amniotic membrane, with the minimum follow up of 1 month in academic practice setting were recruited.

Result

Three patients with 4 weeks period of oozing ulcers and signs of inflammation were included in this case series. Two layers of amniotic membrane dressing was applied weekly after cleaning and debridement for 3 weeks. Wound size and secretion were documented by taking photographs every week. At the end of the third week, the wound healed.

Discussion

Placental amniotic membranes are composed of cells, extra-cellular matrix (ECM), and a complex of regulatory cytokines which promote cell proliferation, cell modulation, and cytokine secretion by variety of cell types involved in wound healing. Our study showed that the treatment of diabetic ulcer wound using amniotic membrane was successful in achieving wound healing in unresponsive, chronic wound of diabetic ulcer of the foot.

Conclusion

Our results clearly indicated the usefulness of the application of amniotic membranes in treatment of diabetic ulcer of the foot. Amniotic membrane favoured healing of unresponsive and non-healing ulcers.

Amniotic membrane for treating skin graft donor sites: A systematic review and meta-analysis

OBJECTIVE

To evaluate the efficacy and safety of amniotic membrane (AM) for the healing of split-thickness skin graft donor sites (STSGDS).

METHOD

Electronic search of PubMed, Cochrane library and EMBASE for randomized controlled trials (RCTs) or non-randomized clinical trials (NRCTs) of AM therapy in STSGDS. Review Manager5.3 was utilized to analyze and present the data.

RESULTS

Seven studies with 219 patients were included. Compared with other treatments, the mean difference (MD) in healing time was -3.87 days (95% CI -4.39, -3.35; P < 0.00001); Relative risk for the healing rate was 1.61 (95% CI 0.0.47-5.47; P = 0.44); There was no statistical difference in the sensation of pain (P > 0.05); The relative risk for infection rate was 0.66 (95% CI 0.29, 2.18; I² = 0%; P = 0.65).

CONCLUSION

This systematic review and meta-analysis indicate that it is effective and safe to use AM for treating STSGDS.

Development of a tissue-engineered skin substitute on a base of human amniotic membrane

Allogenic graft material and tissue engineering have recently shown promising results for the improvement of both esthetic and functional outcomes in the treatment of large skin defects. We chose human amniotic membrane as a cellular scaffold in order to develop a skin substitute for later in vivo uses. Various methods of de-epithelialization of the human amniotic membrane were evaluated by histological analysis including hematoxylin–eosin and laminin staining, optic coherence tomography, and scanning electron microscopy with 0.25/0.02% trypsin/ethylenediaminetetraacetic acid treatment and mechanical cell removal showing an almost complete loss of the epithelium and a mainly intact basement membrane. Novel examination of human amniotic membrane by optic coherence tomography was feasible, but difficulties were experienced in handling and interpretation of the tissue as no comparable data exist. Subsequently, we developed an air–liquid interface cell culture to cultivate keratinocytes and fibroblasts on the de-epithelialized human amniotic membrane. We achieved a mostly keratinized surface on the epidermal side with a confluent fibroblast network on the chorion side.

A randomized, double-blind, phase I clinical trial of fetal cell-based skin substitutes on healing of donor sites in burn patients

BACKGROUND

Due to limited graft donor sites in extensive burns, re-harvesting of a single donor area is very common. Given the importance of fetal fibroblasts in accelerating fetal wound healing, fetal cell-based skin substitutes have emerged as a novel therapeutic modality for regenerating damaged skin. In this trial, we aimed to evaluate the safety, feasibility and potential efficacy of application of amniotic membranes seeded with fetal fibroblasts for accelerating donor sites healing in burn patients.

METHODS

In this randomized, double-blind, phase I clinical trial, 10 patients with total burn surface area of 10-55% were enrolled. Three equal parts (10×10cm) were selected in donor site of each patient and covered by Vaseline gauze (control group), amniotic membrane (AM group), or amniotic membrane seeded with fetal fibroblasts (AM-F group). Adverse events, pain intensity scores, and wound sizes were recorded on days 4, 8, 11, 14, and 20 post-treatment. Also, histological assessments were done on days 0 and 14 after the surgery.

RESULTS

All patients underwent surgery, and no adverse events occurred during the procedure and follow-up period. Significantly lower pain intensity and higher healing rates were observed in AM-F and AM groups compared to the control group. Moreover, mean complete re-epithelializatin in AM-F and AM groups were 10.1±2.4 and 11.3±2.9 days, showing that the healing process was significantly accelerated compared to the control group with mean closure time of 14.8±1.6 days. Histological assessment showed lower inflammatory cells infiltration in AM-F and AM groups compared to control group.

CONCLUSIONS

This study indicated the safety of transplantation of amniotic membrane seeded with fetal fibroblasts for treatment of donor sites in burn patients; however, preliminary assessments showed no benefits for this therapeutic modality over amniotic membrane alone. Thus, to draw accurate conclusions, further trials in larger populations should be conducted.

LEVEL OF EVIDENCE

This study is assigned as level I.

Human Amniotic Membrane with Aligned Electrospun Fiber as Scaffold for Aligned Tissue Regeneration

Fabrication of composite scaffolds is one of the strategies proposed to enhance the functionality of tissue-engineered scaffolds for improved tissue regeneration. By combining multiple elements together, unique biomimetic scaffolds with desirable physical and mechanical properties can be tailored for tissue-specific applications. Despite having a highly porous structure, the utility of electrospun fibers (EF) as scaffold is usually hampered by their insufficient mechanical strength. In this study, we attempted to produce a mechanically competent scaffold with cell-guiding ability by fabricating aligned poly lactic-co-glycolic acid (PLGA) fibers on decellularized human amniotic membrane (HAM), known to possess favorable tensile and wound healing properties. Decellularization of HAM in 18.75 μg/mL of thermolysin followed by a brief treatment in 0.25 M sodium hydroxide efficiently removed the amniotic epithelium and preserved the ultrastructure of the underlying extracellular matrix. The electrospinning of 20% (w/v) PLGA 50:50 polymer on HAM yielded beadless fibers with straight morphology. Subsequent physical characterization revealed that EF-HAM scaffold with a 3-min fabrication had the most aligned fibers with the lowest fiber diameter in comparison with EF-HAM 5- and 7-min scaffolds. Hydrated EF-HAM scaffolds with 3-min deposition had a greater tensile strength than the other scaffolds despite having thinner fibers. Nevertheless, wet HAM and EF-HAMs regardless of the fiber thicknesses had a significantly lower Young's modulus, and hence, a higher elasticity compared with dry HAM and EF-HAMs. Biocompatibility analysis showed that the viability and migration rate of skeletal muscle cells on EF-HAMs were similar to control and HAM alone. Skeletal muscle cells seeded on HAM were shown to display random orientation, whereas cells on EF-HAM scaffolds were oriented along the alignment of the electrospun PLGA fibers. In summary, besides having good mechanical strength and elasticity, EF-HAM scaffold design decorated with aligned fiber topography holds a promising potential for use in the development of aligned tissue constructs.

Human Amniotic Membrane: A Versatile Scaffold for Tissue Engineering

The human amniotic membrane (hAM) is a collagen-based extracellular matrix derived from the human placenta. It is a readily available, inexpensive, and naturally biocompatible material. Over the past decade, the development of tissue engineering and regenerative medicine, along with new decellularization protocols, has recast this simple biomaterial as a tunable matrix for cellularized tissue engineered constructs. Thanks to its biocompatibility, decellularized hAM is now commonly used in a broad range of medical fields. New preparation techniques and composite scaffold strategies have also emerged as ways to tune the properties of this scaffold. The current state of understanding about the hAM as a biomaterial is summarized in this review. We examine the processing techniques available for the hAM, addressing their effect on the mechanical properties, biodegradation, and cellular response of processed scaffolds. The latest in vitro applications, in vivo studies, clinical trials, and commercially available products based on the hAM are reported, organized by medical field. We also look at the possible alterations to the hAM to tune its properties, either through composite materials incorporating decellularized hAM, chemical cross-linking, or innovative layering and tissue preparation strategies. Overall, this review compiles the current literature about the myriad capabilities of the human amniotic membrane, providing a much-needed update on this biomaterial.

Human Amniotic Membrane Is Not Suitable for the Grafting of Colon Lesions and Prevention of Adhesions in a Xenograft Rat Model

INTRODUCTION

New biological materials are needed for specific applications in reconstructive bowel surgery and for the prevention of adhesion formation. Amniotic membranes (AMs) are assumed to have a number of unique characteristics that enhance the ingrowth of the surrounding tissue. The aim of the present study was to provide proof of these qualities in a xenograft model.

MATERIALS AND METHODS

A multilayer human AM (HAM) was applied to repair defined colon wall defects in Sprague-Dawley rats (n = 18). The control group was repaired with a suture (n = 6). The animals were killed humanely at 7, 21, and 42 days after implantation. Adhesions and perioperative complications were examined. Histological and immunohistological analyses were performed to assess a number of parameters, including degradation of the HAM, inflammation, graft rejection, and smooth muscle ingrowth.

RESULTS

Two rats in the treated group died. No other severe complications were observed. Adhesion formation was more prominently visible in the HAM group ( P < .05). The initially increased inflammation in the HAM group reduced over time but remained significantly increased ( P < .05). The HAM degraded over time and a subtle transient glomerulitis could be observed.

CONCLUSION

HAMs were found to increase adhesion formation and were not suitable for bowel augmentation in the presented xenograft model.

The effects of Alkanna tinctoria Tausch on split-thickness skin graft donor site management: a randomized, blinded placebo-controlled trial

BACKGROUND

A prospective, randomized, placebo-controlled clinical trial was conducted to compare the healing effectiveness of Alkanna tinctoria (L.) Tausch (Boraginaceae) with standard dressing on wound healing at the donor site after removal of the skin graft.

METHODS

Enrolled patients were randomly allocated to receive topicalA. tinctoria extract ointment (20%) or standard dressing (dressing with base ointment) daily. Wound healing was assessed using the Bates-Jenson assessment tool at the 2^nd and 4^th weeks after intervention.

RESULTS

Decreases in wound score were significantly greater in the A. tinctoria group compared with the placebo group (P <0.05). The surface areas of graft donor sites in the A. tinctoria group were significantly reduced as compared with the control group at day 28 of the intervention (P < 0.05). The proportion of patients in the A. tinctoria group achieving complete wound healing within 2 to 4 weeks was 50% and 96.66%, respectively, significantly higher than in patients receiving standard care: 0% and 23.3%, respectively.

CONCLUSIONS

This clinical study showed that A. tinctoria dressing accelerates wound healing after graft harvesting.

TRIAL REGISTRATION

IRCT ID: IRCT201511165781N2 .

Stress relaxation and stress-strain characteristics of porcine amniotic membrane

BACKGROUND

Recently, amniotic membrane (AM) as scaffold is accumulating much more attention in tissue engineering. It is well-known that the mechanical properties of the scaffold inevitably affect the biological process of the incorporated cells.

OBJECTIVE

This study investigates the stress relaxation and stress-strain characteristics of AM, which have not been sufficiently elucidated before.

METHODS

Porcine AM samples were prepared at four different AM regions and at three different directions. Ramp-and-hold and stretch-to-rupture tests were conducted on a uniaxial tensile apparatus. A nonlinear viscoelastic model with two relaxation coefficients is proposed to fit the ramp-and-hold data. Rupture strain, rupture stress, and elastic modulus of the linear portion of the stress-strain curve are used to characterize the strength properties of the AM.

RESULTS

Sample direction has no significant effect on the mechanical properties of the AM. Samples at the ventral region has the maximum rupture strength and elastic modulus, respectively, 2.29±0.99MPa and 6.26±2.69MPa. The average of the relaxation coefficient for the fast and slow relaxation phases are 12.8±4.4s and 37.0±7.7s, respectively.

CONCLUSIONS

AM is a mechanically isotropic and heterogeneous material. The nonlinear viscoelastic model is suitable to model the AM viscoelasticity and potential for other biological tissues.

Bladder Reconstruction with Human Amniotic Membrane in a Xenograft Rat Model: A Preclinical Study

Background: Human amniotic membranes (HAMs) are assumed to have a number of unique characteristics including durability, hypoallergenic and anti-inflammatory properties. Materials and Methods: Multilayer HAMs from caesarian sections were applied to repair defined bladder defects in male Sprague-Dawley rats. The animals were sacrificed at 7, 21 and 42 days after implantation. Bladder volume capacity after grafting was measured. Histological analyses were performed to asses a number of parameters including HAM degradation, inflammatory reaction, graft rejection and smooth muscle ingrowth. Results: One rat died from sepsis in the treated group. No severe complications or signs of leakage were observed. Bladder capacity did not change over time. The initially increased inflammation in the HAM group diminished significantly over time (p<0.05). No signs of HAM degradation were observed and smooth muscle staining increased over time. Conclusions: HAMs appear to be durable and hypoallergenic grafts. The assumed suitability for the reconstruction of urinary tract justifies further research on detailed immunological process in larger grafts.

Aseptically Processed Placental Membrane Improves Healing of Diabetic Foot Ulcerations: Prospective, Randomized Clinical Trial

BACKGROUND

Allogeneic grafts derived from amnion/chorion are known to be efficacious in healing chronic diabetic foot ulcerations (DFUs). The goal of this study was to compare aseptically processed dehydrated human amnion and chorion allograft (dHACA) versus standard of care (SOC) in facilitating wound closure in nonhealing DFUs.

METHODS

Patients with DFUs treated with SOC (off-loading, appropriate debridement, and moist wound care) after a 2-week screening period were randomized to either SOC or wound-size-specific dHACA (AmnioBand, Musculoskeletal Transplant Foundation, Edison, N.J.) applied weekly for up to 12 weeks plus SOC. Primary endpoint was the percentage of wounds healed at 6 weeks between groups.

RESULTS

At 6 weeks, 70% (14/20) of the dHACA-treated DFUs healed compared with 15% (3/20) treated with SOC alone. Furthermore, at 12 weeks, 85% (17/20) of the DFUs in the dHACA group healed compared with 25% (5/20) in the SOC group, with a corresponding mean time to heal of 36 and 70 days, respectively. At 12 weeks, the mean number of grafts used per healed wound for the dHACA group was 3.8 (median 3.0), and mean cost of the tissue to heal a DFU was $1400. The mean wastage at 12 weeks was 40%. One adverse event and 1 serious adverse event occurred in the dHACA group; neither was graft related. Three adverse events and 1 serious adverse event occurred in the SOC group.

CONCLUSION

Aseptically processed dHACA heals diabetic foot wounds significantly faster than SOC at 6 and 12 weeks with minimal graft wastage.

Human Amniotic Membrane-Derived Products in Sports Medicine: Basic Science, Early Results, and Potential Clinical Applications

BACKGROUND

Amniotic membrane (AM)-derived products have been successfully used in ophthalmology, plastic surgery, and wound care, but little is known about their potential applications in orthopaedic sports medicine.

PURPOSE

To provide an updated review of the basic science and preclinical and clinical data supporting the use of AM-derived products and to review their current applications in sports medicine.

STUDY DESIGN

Systematic review.

METHODS

A systematic search of the literature was conducted using the Medline, EMBASE, and Cochrane databases. The search term amniotic membrane was used alone and in conjunction with stem cell, orthopaedic, tissue engineering, scaffold, and sports medicine.

RESULTS

The search identified 6870 articles, 80 of which, after screening of the titles and abstracts, were considered relevant to this study. Fifty-five articles described the anatomy, basic science, and nonorthopaedic applications of AM-derived products. Twenty-five articles described preclinical and clinical trials of AM-derived products for orthopaedic sports medicine. Because the level of evidence obtained from this search was not adequate for systematic review or meta-analysis, a current concepts review on the anatomy, physiology, and clinical uses of AM-derived products is presented.

CONCLUSION

Amniotic membranes have many promising applications in sports medicine. They are a source of pluripotent cells, highly organized collagen, antifibrotic and anti-inflammatory cytokines, immunomodulators, and matrix proteins. These properties may make it beneficial when applied as tissue engineering scaffolds, improving tissue organization in healing, and treatment of the arthritic joint. The current body of evidence in sports medicine is heavily biased toward in vitro and animal studies, with little to no human clinical data. Nonetheless, 14 companies or distributors offer commercial AM products. The preparation and formulation of these products alter their biological and mechanical properties, and a thorough understanding of these differences will help guide the use of AM-derived products in sports medicine research.

Amniotic membrane can be a valid source for wound healing

Amniotic membrane (AM) can promote proper epithelialization with suppression of excessive fibrosis by creating a supportive milieu for regeneration of chronic ulcer bed.

Influence of the Oil Phase and Topical Formulation on the Wound Healing Ability of a Birch Bark Dry Extract

Triterpenes from the outer bark of birch are known for various pharmacological effects including enhanced wound healing (WH). A birch bark dry extract (TE) obtained by accelerated solvent extraction showed the ability to form oleogels when it is suspended in oils. Consistency of the oleogels and the dissolved amount of triterpenes varies largely with the used oil. Here we wanted to know to what extent different oils and formulations (oleogel versus o/w emulsion) influence WH. Looking at the plain oils, medium-chain triglycerides (MCT) enhanced WH (ca. 1.4-fold), while e.g. castor oil (ca.0.3-fold) or light liquid paraffin (LLP; ca. 0.5-fold) significantly decreased WH. Concerning the respective oleogels, TE-MCT showed no improvement although the solubility of the TE was high. In contrast, the oleogel of sunflower oil which alone showed a slight tendency to impair WH, enhanced WH significantly (ca. 1.6-fold). These results can be explained by release experiments where the release rate of betulin, the main component of TE, from MCT oleogels was significantly lower than from sunflower oil oleogels. LLP impaired WH as plain oil and even though it released betulin comparable to sunflower oil it still results in an overall negative effect of the oleogel on WH. As a further formulation option also surfactant free o/w emulsions were prepared using MCT, sunflower oil and LLP as a nonpolar oil phase. Depending on the preparation method (suspension or oleogel method) the distribution of the TE varied markedly and affected also release kinetics. However, the released betulin was clearly below the values measured with the respective oleogels. Consequently, none of the emulsions showed a significantly positive effect on WH. In conclusion, our data show that the oil used as a vehicle influences wound healing not only by affecting the release of the extract, but also by having its own vehicle effect on wound healing. This is also of importance for other applications where drugs have to be applied in non-polar vehicles because these solvents likely influence the outcome of the experiment substantially.

Advancing biomaterials of human origin for tissue engineering

Biomaterials have played an increasingly prominent role in the success of biomedical devices and in the development of tissue engineering, which seeks to unlock the regenerative potential innate to human tissues/organs in a state of deterioration and to restore or reestablish normal bodily function. Advances in our understanding of regenerative biomaterials and their roles in new tissue formation can potentially open a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multi-component construction of native extracellular matrices (ECMs) for cell accommodation, the synthetic biomaterials produced today routinely incorporate biologically active components to define an artificial in vivo milieu with complex and dynamic interactions that foster and regulate stem cells, similar to the events occurring in a natural cellular microenvironment. The range and degree of biomaterial sophistication have also dramatically increased as more knowledge has accumulated through materials science, matrix biology and tissue engineering. However, achieving clinical translation and commercial success requires regenerative biomaterials to be not only efficacious and safe but also cost-effective and convenient for use and production. Utilizing biomaterials of human origin as building blocks for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural tissue with regard to its physical and chemical properties for the orchestration of wound healing and tissue regeneration. In addition to directly using tissue transfers and transplants for repair, new applications of human-derived biomaterials are now focusing on the use of naturally occurring biomacromolecules, decellularized ECM scaffolds and autologous preparations rich in growth factors/non-expanded stem cells to either target acceleration/magnification of the body's own repair capacity or use nature's paradigms to create new tissues for restoration. In particular, there is increasing interest in separating ECMs into simplified functional domains and/or biopolymeric assemblies so that these components/constituents can be discretely exploited and manipulated for the production of bioscaffolds and new biomimetic biomaterials. Here, following an overview of tissue auto-/allo-transplantation, we discuss the recent trends and advances as well as the challenges and future directions in the evolution and application of human-derived biomaterials for reconstructive surgery and tissue engineering. In particular, we focus on an exploration of the structural, mechanical, biochemical and biological information present in native human tissue for bioengineering applications and to provide inspiration for the design of future biomaterials.

Repair of a vesico-vaginal fistula with amniotic membrane - Step 1 of the IDEAL recommendations of surgical innovation

Introduction

Complex vesico-vaginal fistula (VVF) has a high recurrence rate and so the repair with graft tissues seems to be favorable. Amniotic membrane (AM) plays an increasing role as a scaffold for the repair of defect tissue due to its unique biological properties with regard to promoting wound healing.

Material and methods

An innovative surgical procedure for AM-assisted repair of a complex vesico-vaginal fistula as the Idea Stage following the IDEAL recommendations is presented. The development of amnion preparation and the involved surgical steps are described.

Results

We are able to report a successful repair of VVF by abdominal approach with an amniotic membrane graft. Good functional results, no adverse events and no graft rejection have been detected.

Conclusions

Favorable results confirm the technical simplicity, safety and efficacy of this procedure. Following the IDEAL recommendations, consecutive animal experiments and a cohort study are in progress.

MicroRNAs in skin tissue engineering

35.2 million annual cases in the U.S. require clinical intervention for major skin loss. To meet this demand, the field of skin tissue engineering has grown rapidly over the past 40 years. Traditionally, skin tissue engineering relies on the "cell-scaffold-signal" approach, whereby isolated cells are formulated into a three-dimensional substrate matrix, or scaffold, and exposed to the proper molecular, physical, and/or electrical signals to encourage growth and differentiation. However, clinically available bioengineered skin equivalents (BSEs) suffer from a number of drawbacks, including time required to generate autologous BSEs, poor allogeneic BSE survival, and physical limitations such as mass transfer issues. Additionally, different types of skin wounds require different BSE designs. MicroRNA has recently emerged as a new and exciting field of RNA interference that can overcome the barriers of BSE design. MicroRNA can regulate cellular behavior, change the bioactive milieu of the skin, and be delivered to skin tissue in a number of ways. While it is still in its infancy, the use of microRNAs in skin tissue engineering offers the opportunity to both enhance and expand a field for which there is still a vast unmet clinical need. Here we give a review of skin tissue engineering, focusing on the important cellular processes, bioactive mediators, and scaffolds. We further discuss potential microRNA targets for each individual component, and we conclude with possible future applications.