Amnion: The Ideal Scaffold for Treating Full-Thickness Wounds of the Lower Extremity

Hyperdry Human Amniotic Membrane as a Protective Dressing for Open Wounds With Exposed Bowel in Mice

INTRODUCTION

An enteroatmospheric fistula forms when the exposed bowel is perforated with chronic enteric fistula formation. Currently, there is no established preventative method for this condition. Hyperdry (HD) amniotic membrane (AM) can promote early granulation tissue formation on the exposed viscera and is suitable for dressing intractable wounds as it possesses anti-inflammatory, antibacterial, and immunomodulatory properties. This study investigated whether HD-AM promotes early formation of blood vessel-containing granulation tissue for enteroatmospheric fistula treatment.

METHODS

An experimental animal model of an open wound with exposed bowel was developed. A 15 × 20 mm wound was prepared on the abdomen of Institute of Cancer Research mice, and the HD-AM was placed. The mice were assigned to one of the following groups: HD-AM group, in which the stromal layer of the HD-AM was placed in contact with the exposed bowel; HD-AM UD group, in which the epithelial layer of the HD-AM was placed in contact with the exposed bowel; and the HD-AM (-) or control group, in which the HD-AM was not used.

RESULTS

On postoperative days 7 and 14, granulation tissue thickness significantly increased in the HD-AM and HD-AM UD groups compared with that in the HD-AM (-) group. Macrophages accumulated in the HD-AM epithelium only in the HD-AM group. During HD-AM contact, a subset of invading macrophages switched from M1 to M2 phenotype.

CONCLUSIONS

HD-AM is a practical wound dressing with its scaffolding function, regulation of TGF β-1 and C-X-C motif chemokine 5 (CXCL-5), and ability to induce M1-to-M2 macrophage conversion.

Effectiveness and safety of human amnion/chorion membrane therapy for diabetic foot ulcers: An updated meta-analysis of randomized clinical trials

Human amnion/chorion membrane therapy has shown advantages in the management of diabetic foot ulcers and its effectiveness has been evaluated in the systematic reviews and meta-analyses. However, the number of patients included in the previous literatures was small and the safety profile of human amnion/chorion membrane therapy was not concerned. Therefore, we conducted an updated meta-analysis to better understand the effectiveness and safety of human amnion/chorion membrane therapy for diabetic foot ulcers. The PubMed, Embase, Cochrane Library, and ClinicalTrial.gov databases were searched for any randomized clinical trials comparing human amnion/chorion membrane therapy and standard therapy in the treatment of diabetic foot ulcers. Ulcer healing rate was considered as the primary outcome and the secondary outcomes mainly included mean time to ulcer healing and adverse events. Nine RCTs with 541 patients were included. Compared with merely standard therapy, human amnion/chorion membrane therapy plus standard therapy improved the ulcer healing rates at 6 weeks (RR = 3.50, 95% CI: 2.35-5.21), 12 weeks (RR = 2.09, 95% CI: 1.53-2.85) and 16 weeks (RR = 1.70, 95% CI: 1.25-2.30), and also shortened the healing time (MD = -4.58, 95% CI: -5.70 to -3.46). Meanwhile, no significant difference was observed in the number of patients with adverse events (RR = 0.56, 95% CI: 0.31-1.03) between two groups. This meta-analysis suggests that human amnion/chorion membrane therapy as an adjuvant treatment could promote the healing of diabetic foot ulcers and has a safety profile. More evidence from large high-quality randomized clinical trials with long follow-up duration are in urgent need to further confirm our findings.

LOXL2 from human amniotic mesenchymal stem cells accelerates wound epithelialization by promoting differentiation and migration of keratinocytes

In this study, we identified wound healing-related proteins secreted by human amniotic epithelial cells (hAECs) and human amniotic mesenchymal stem cells (hAMSCs). We observed increased migration and reduced proliferation and differentiation when keratinocytes were co-cultured in media conditioned by hAECs (hAECs-CM) and hAMSCs (hAMSCs-CM). Label-free mass spectrometry and bioinformatic analyses of the hAECs-CM and hAMSCs-CM proteome revealed several proteins associated with wound healing, angiogenesis, cellular differentiation, immune response and cell motility. The levels of the proteins related to wound healing, including CTHRC1, LOXL2 and LGALS1, were significantly higher in hAMSCs-CM than hAECs-CM. LOXL2 significantly enhanced in vitro keratinocyte migration and differentiation compared to CTHRC1 and LGALS1. Moreover, LOXL2 enhanced keratinocyte migration and differentiation by activating the JNK signaling pathway. We observed significant reduction in the in vitro migration and differentiation of keratinocytes when co-cultured with medium conditioned by LOXL2-silenced hAMSCs and when treated with 10 μM SP600125, a specific JNK inhibitor. Treatment with hAMSCs-CM and LOXL2 significantly accelerated wound healing in the murine skin wound model. These findings show that LOXL2 promotes wound healing by inducing keratinocyte migration and differentiation via a JNK signaling pathway.

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.

Autologous amniotic membrane: An accelerator of wound healing for prevention of surgical site infections following Cesarean delivery

Cesarean delivery (CD) has been known as the most common surgery in the United States. This procedure might associate with different complications, the most important of which is surgical site infection (SSI). Among the major SSI categories, incisional type is more common than the others. Regardless of its notable expense, the use of prophylactic wound healing technics (such as negative pressure therapy) has been advised for the patients with high SSI risk. Herein, use of patient's own human amniotic membrane in an autologous form (as a free of charge treatment) would be suggested for prevention of SSI in CD wounds. Human amniotic membrane (hAM) has been used for treatment of acute and chronic wounds and shown to be able to reduce the infection and the pain along with accelerating the healing process. Moreover, it has been shown in a systematic review and meta-analysis that hAM could significantly improve the treatment rate in comparison to the standard of care dressing (RR 2.057-3.665, P < 0.001) during a set time of six weeks. Wound duration on the other hand, has been shown to negatively associate with SSI. Furthermore, there is data supporting the critical role of tissue perfusion in the acceleration of wound healing along with decreasing the rate of wound infection. Angiogenesis, the formation of new blood vessels from their existing capillaries, is among the most crucial pathways involved in increasing tissue perfusion and wound healing. Interestingly, hAM is a rich source of pro-angiogenic and other tissue growth factors with the ability of inducing angiogenesis as well as strong antibacterial peptides. Taken together, authors suggest autologous application of hAM in the high (even low) risk patients undergoing CD in order to decrease wound related complications such as SSI and accelerate the healing time as a free wound healer. However, further randomized clinical trials are necessary.

Biological Amnion Prevents Flexor Tendon Adhesion in Zone II: A Controlled, Multicentre Clinical Trial

Introduction

Tendon adhesion to surrounding tissues is the most common complication reported after tendon repair. To date, effective solutions to prevent tendon injury are still lacking.

Materials and Methods

A total of 89 patients with flexor tendon injury in zone II were recruited. The patients were divided into a control group, a poly-DL-lactic acid (PDLLA) group, and an amnion group according to the different tendon treatments applied. The control group was not subjected to other treatments. PDLLA and bioamniotic membranes were, respectively, used to wrap broken ends in the PDLLA and amnion membrane groups. The patients were followed at 1, 2, 3, 6, and 12 months after surgery and the ranges of active flexion and extension lag in the proximal and distal interphalangeal joints were evaluated.

Results

The means of total active ranges of motion of the interphalangeal joints (excluding rupture cases) in the PDLLA and amnion groups did not significantly differ between each other but significantly differed from that of the control group. Statistical analysis showed a significant difference in the clinical grades of the outcomes among the control, PDLLA, and amnion groups. The incidence of complications in the control and PDLLA groups was found to be significantly higher than that in the amniotic membrane group; no significant difference was observed between the control and PDLLA groups.

Conclusion

In this study, freeze-dried amniotic membrane transplantation was applied to promote healing of the flexor tendon in zone II and prevent adhesion. This technique presents a new method to solve the issue of tendon adhesion after repair.

Clinical Trial Registration

The trial was registered by identifier ChiCTR1900021769.

Experimental study of tendon sheath repair via decellularized amnion to prevent tendon adhesion

The adhesion of tendon and surrounding tissue is the most common complication after repairing an injured tendon. The injured flexor tendons in zone II are frequently accompanied by tendon sheath defects, which lead to poor recovery. A variety of biological and non-biological materials have been recently used for repair or as substitute for tendon sheaths to prevent tendon adhesion. However, non-biological materials, such as polyethylene films, have been used to prevent tendon adhesions by mechanical isolation. The possibility of tendon necrosis and permanent foreign body remains due to the lack of permeability and the obstruction of nutrient infiltration. The natural macromolecule amniotic membrane derived from organisms is a semi-permeable membrane with the following characteristics: smooth; without vascular, nerve, and lymphatic; and rich in matrix, cytokines, enzymes, and other active ingredients. The unique structure of this membrane makes it an ideal biomaterial. In the experiment in Henry chicken, the model of tendon sheath defect and the flexor digitorum tendon in zone II was established and randomly divided into control group, medical membrane group, and decellularized amniotic membrane group. Samples were obtained at the 2nd, 4th, 8th, and 12th week after operation. General, histological, and biomechanical tests were performed to investigate the preventive effect of repaired tendon sheath by decallularized amniotic membrane. Experimental results showed the following: the amniotic membrane group and the medical membrane group had mild inflammatory reaction and tissue edema, and nearly no adhesion was observed in the surrounding tissue; the fibroblast-like cells were distributed in layers under the light microscope; the amniotic membrane group was denser than the medical membrane group cells, and numerous fibroblasts were disorganized in the control group. Biomechanical measurements showed that the sliding distance of tendon, the total flexion angle of the toes, and the tendon maximum tensile breaking strength at the early postoperative were significantly better than in the control group. Through this experiment, the amniotic membrane, as a natural biological substitute material in the construction of tendon sheath, can effectively inhibit exogenous healing and promote endogenous healing to prevent tendon adhesion.