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

Preclinical and clinical evidence for using perinatal tissue allografts in nerve sparing robot assisted radical prostatectomy to hasten recovery of functional outcomes: a literature review

INTRODUCTION

Localized prostate cancer (PCa) is one of the most common malignancies in the United States. Despite continued refinement of robot assisted radical prostatectomy (RARP) surgical methods, post-surgical erectile dysfunction and urinary incontinence remain significant challenges due to iatrogenic injury of local nervous tissue. Thus, the development of therapeutic strategies, including the use of biologic adjuncts to protect and/or enhance recovery and function of nerves following RARP is of growing interest. Perinatal tissue allografts have been investigated as one such biologic adjunct to nerve sparing RARP. However, knowledge regarding their clinical efficacy in hastening return of potency and continence as well as the potential underpinning biological mechanisms involved remains understudied. Thus, the objective of this literature review was to summarize published basic science and clinical studies supporting and evaluating the use of perinatal allografts for nerve repair and their clinical efficacy as adjuncts to RARP, respectively.

METHODS

The literature as of May 2024 was reviewed non-systematically using PubMed, EMBASE, Scopus, and Web of Science databases. The search terms utilized were "robotic prostatectomy", "prostate cancer", "nerve sparing", "perinatal tissue", "allograft", "potency", and "continence" alone or in combination. All articles were reviewed and judged for scientific merit by authors RP and JM, only peer-reviewed studies were considered.

RESULTS

Eight studies of perinatal tissue allograph use in RARP were deemed worthy of inclusion in this nonsystematic review.

CONCLUSIONS

Incontinence and impotence remain significant comorbidities despite continued advancement in surgical technique. However, basic science research has demonstrated potential neurotrophic, anti-fibrotic, and anti-inflammatory properties of perinatal tissue allografts, and clinical studies have shown that patients who receive an intra-operative prostatic perinatal membrane wrap have faster return to potency and continence.

Advancements in diabetic foot ulcer research: Focus on mesenchymal stem cells and their exosomes

Diabetes represents a widely acknowledged global public health concern. Diabetic foot ulcer (DFU) stands as one of the most severe complications of diabetes, its occurrence imposing a substantial economic burden on patients, profoundly impacting their quality of life. Despite the deepening comprehension regarding the pathophysiology and cellular as well as molecular responses of DFU, the current therapeutic arsenal falls short of efficacy, failing to offer a comprehensive remedy for deep-seated chronic wounds and microvascular occlusions. Conventional treatments merely afford symptomatic alleviation or retard the disease's advancement, devoid of the capacity to effectuate further restitution of compromised vasculature and nerves. An escalating body of research underscores the prominence of mesenchymal stem cells (MSCs) owing to their paracrine attributes and anti-inflammatory prowess, rendering them a focal point in the realm of chronic wound healing. Presently, MSCs have been validated as a highly promising cellular therapeutic approach for DFU, capable of effectuating cellular repair, epithelialization, granulation tissue formation, and neovascularization by means of targeted differentiation, angiogenesis promotion, immunomodulation, and paracrine activities, thereby fostering wound healing. The secretome of MSCs comprises cytokines, growth factors, chemokines, alongside exosomes harboring mRNA, proteins, and microRNAs, possessing immunomodulatory and regenerative properties. The present study provides a systematic exposition on the etiology of DFU and elucidates the intricate molecular mechanisms and diverse functionalities of MSCs in the context of DFU treatment, thereby furnishing pioneering perspectives aimed at harnessing the therapeutic potential of MSCs for DFU management and advancing wound healing processes.

Combined therapeutic use of umbilical cord blood serum and amniotic membrane in diabetic wounds

Diabetic wounds are hard-to-heal due to complex multifactorial dysregulation within the micro-environment, necessitating the development of novel regenerative approaches to stimulate healing. This study investigated whether the combined therapeutic application of two novel cellular tissue products, namely a decellularized collagen-rich amniotic membrane (AmR) and growth factor-rich umbilical cord blood serum (UCBS) could have a positive synergistic effect on long-term healing outcomes by stimulating both superficial wound closure and wound bed regeneration. Full thickness excisional wounds were induced on obese diabetic mice (B6.Cg-lepob/J, ob/ob, n = 23) and treated with either: 1) Standard wound care (control); 2) UCBS; 3) AmR or 4) UCBS + AmR. Macroscopic wound closure was assessed on days 0, 3, 7, 10 and 14 post wounding. To determine the potential impact on wound recurrence, endpoint analysis was performed to determine both the overall quality of healing histologically as well as the molecular state of the wounds on day 14 via proteomic analysis. The data demonstrated the presence of both healers and non-healers. Re-epithelization took place in the healers of all treatment groups, but underlying tissue regeneration was far more pronounced following application of the combined treatment (UCBS + AmR), suggesting improved quality of healing and potentially a reduced change of recurrence long term. In non-healers, wounds failed to heal due to excessive slough formation and a reduction in LTB4 expression, suggesting impaired antimicrobial activity. Care should thus be taken since the cellular tissue product therapy could pose an increased risk for infection in some patients.

Use of amniotic membrane in hard-to-heal wounds: a multicentre retrospective study

OBJECTIVE

Hard-to-heal (chronic) wounds negatively impact patients and are a source of significant strain on the healthcare system and economy. These wounds are often resistant to standard of care (SoC) wound healing approaches due to a diversity of underlying pathologies. Cellular, acellular, and matrix-like products, such as amniotic membranes (AM), are a potential solution to these challenges. A growing body of evidence suggests that AM may be useful for treatment-resistant wounds; however, limited information is available regarding the efficacy of dehydrated amniotic membrane (DHAM) on multi-aetiology, hard-to-heal wounds. Therefore, we analysed the efficacy of DHAM treatment in reducing the size of hard-to-heal diabetic and venous leg ulcers (VLUs) that had failed to improve after SoC-based treatments.

METHOD

In this multicentre retrospective study, we analysed wound size during clinic visits for patients being treated for either diabetic or VLUs. During each visit, the treatment consisted of debridement followed by application of DHAM. Each wound was measured after debridement and prior to DHAM application, and wound volumes over time or number of DHAM applications were compared.

RESULTS

A total of 18 wounds in 11 patients were analysed as part of this study. Wounds showed a significant reduction in volume after a single DHAM application, and a 50% reduction in wound size was observed after approximately two DHAM applications. These findings are consistent with reports investigating DHAM treatment of diabetic ulcers that were not necessarily resistant to treatment.

CONCLUSION

To our knowledge, this study is the first to directly compare the efficacy of standalone DHAM application to hard-to-heal diabetic and venous leg ulcers, and our findings indicate that DHAM is an effective intervention for resolving these types of wounds. This suggests that implementing this approach could lead to fewer clinic visits, cost savings and improved patient quality of life.

DECLARATION OF INTEREST

This research was supported in part by Merakris Therapeutics, US, and facilitated access to deidentified patient datasets, which may represent a perceived conflict of interest; however, the primary data analysis was performed by FSB who is unaffiliated with Merakris Therapeutics. TCB is a founder, employee of and shareholder in Merakris Therapeutics; WSF is a co-founder of, consultant for, and shareholder in Merakris Therapeutics, and was also supported by the National Institutes of Health National Center for Advancing Translational Sciences Clinical and Translational Science Awards Grant KL2 Scholars Program (KL2TR001441). The research was also supported through endowments to WSF from the University of Texas Medical Branch Mimmie and Hallie Smith Endowed Chair of Transplant Research and the John L Hern University Chair in Transplant Surgery.

Dehydrated human amnion/chorion membrane allograft with spongy layer to significantly improve the outcome of chronic non-healing wounds

We investigated the healing effect of a new dehydrated amnion/chorion membrane with a spongy layer over a 30-month period in 32 patients with 53 chronic non-healing wounds of different aetiologies. Wounds with <40% surface reduction after 4 weeks of best wound treatment underwent weekly allograft application by a certified wound specialist based on national guidelines and a standardised protocol until complete healing or definite treatment interruption. The main outcome measure was the percentage of wound surface reduction from baseline calculated using digital planimetry follow-up photographs. Overall, 38 (71.7%) wounds presented a favourable outcome (70%-100% area reduction), with 35 (66%) completely healing over a median time of 77 days (range 29-350 days). Favourable outcomes were observed in 75% of traumatic wounds, surgical wounds, venous leg ulcers and pressure injuries, as well as in 50% of ischaemic wounds. Wounds being present <12 months were significantly more likely to have a favourable outcome than more long-standing wounds (χ2  = 7.799; p = 0.005; OR = 3.378; 95% CI, 1.410-8.092). Thus, treatment with dehydrated amnion/chorion membrane with a spongy layer improves the outcome of non-healing wounds of different aetiologies and, therefore, has to be considered early in the management of refractory wounds.

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.

Placental-Derived Biomaterials and Their Application to Wound Healing: A Review

Chronic wounds are associated with considerable patient morbidity and present a significant economic burden to the healthcare system. Often, chronic wounds are in a state of persistent inflammation and unable to progress to the next phase of wound healing. Placental-derived biomaterials are recognized for their biocompatibility, biodegradability, angiogenic, anti-inflammatory, antimicrobial, antifibrotic, immunomodulatory, and immune privileged properties. As such, placental-derived biomaterials have been used in wound management for more than a century. Placental-derived scaffolds are composed of extracellular matrix (ECM) that can mimic the native tissue, creating a reparative environment to promote ECM remodeling, cell migration, proliferation, and differentiation. Reliable evidence exists throughout the literature to support the safety and effectiveness of placental-derived biomaterials in wound healing. However, differences in source (i.e., anatomical regions of the placenta), preservation techniques, decellularization status, design, and clinical application have not been fully evaluated. This review provides an overview of wound healing and placental-derived biomaterials, summarizes the clinical results of placental-derived scaffolds in wound healing, and suggests directions for future work.

A minimally manipulated preservation and virus inactivation method for amnion/chorion

Allogeneic amnion tissues have been widely used in tissue repair and regeneration, especially a remarkable trend of clinical uses in chronic wound repair. The virus inactivation procedures are necessary and required to be verified for the clinical use and approval of biological products. Cobalt-60 (Co-60) or electron-beam (e-beam) is the common procedure for virus and bacterial reduction, but the excessive dose of irradiation was reported to be harmful to biological products. Herein, we present a riboflavin (RB)-ultraviolet light (UV) method for virus inactivation of amnion and chorion tissues. We used the standard in vitro limiting dilution assay to test the viral reduction capacity of the RB-UV method on amnion or chorion tissues loaded with four types of model viruses. We found RB-UV was a very effective procedure for inactivating viruses of amnion and chorion tissues, which could be used as a complementary method to Co-60 irradiation. In addition, we also screened the washing solutions and drying methods for the retention of growth factors.

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.

Electrospun Polycaprolactone (PCL)-Amnion Nanofibrous Membrane Promotes Nerve Regeneration and Prevents Fibrosis in a Rat Sciatic Nerve Transection Model

Functional recovery after peripheral nerve injury repair is typically unsatisfactory. An anastomotically poor microenvironment and scarring at the repair site are important factors impeding nerve regeneration. In this study, an electrospun poly-e-caprolactone (PCL)-amnion nanofibrous membrane comprising an amnion membrane and nonwoven electrospun PCL was used to wrap the sciatic nerve repair site in the rat model of a sciatic nerve transection. The effect of the PCL-amnion nanofibrous membrane on improving nerve regeneration and preventing scarring at the repair site was evaluated by expression of the inflammatory cytokine, sciatic functional index (SFI), electrophysiology, and histological analyses. Four weeks after repair, the degree of nerve adhesion, collagen deposition, and intraneural macrophage invasion of the PCL-amnion nanofibrous membrane group were significantly decreased compared with those of the Control group. Moreover, the PCL-amnion nanofibrous membrane decreased the expression of pro-inflammatory cytokines such as interleukin(IL)-6, Tumor Necrosis Factor(TNF)-a and the number of pro-inflammatory M1 macrophages, and increased the expression of anti-inflammatory cytokine such as IL-10, IL-13 and anti-inflammatory M2 macrophages. At 16 weeks, the PCL-amnion nanofibrous membrane improved functional recovery, including promoting nerve Schwann cell proliferation, axon regeneration, and reducing the time of muscle denervation. In summary, the PCL-amnion nanofibrous membrane effectively improved nerve regeneration and prevent fibrosis after nerve repair, which has good clinical application prospect for tissue repair.