Microbiological safety and clinical efficacy of radiation sterilized amniotic membranes for treatment of second-degree burns

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

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

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.

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.

Amnion bilayer for dressing and graft replacement for delayed grafting of full-thickness burns; A study in a rat model

Burn is a common case in developing countries, with over half of fire-related deaths reported in Southeast Asia and full-thickness burns as a high mortality risk. Human amnion has been used as a wound dressing for centuries. In this study, a decellularised amnion overlaid with fibrin, “amnion bilayer (AB),” was used as a dressing immediately after burn and as a graft to replace the scar in Sprague-Dawley rats subjected to full-thickness burn model. The aim was to observe whether amnion bilayer can reduce damages in third-grade burn when skin replacement is deemed impossible. The burn was induced using an electrical solder, heated for 5 mins, and contacted on the rat’s bare skin for 20 s. AB was applied as a (i) dressing immediately after induction and graft after eschar removal. Two groups (n = 6) were compared: AB and Sofra-Tulle ^®, the National Hospital of Indonesia (NHI) protocol. Sections were stained with hematoxylin and eosin and Masson trichrome stains. Immunohistochemistry labelling was used to indicate scars (α-smooth muscle actin [α-SMA] and collagen-1) and angiogenesis (von Willebrand factor). Also, the macrophages inflammatory protein-3α (MIP-3α) indicates an early inflammatory process. The post dressing of the AB group demonstrated hair follicle remains and adipose tissue development. The NHI group appeared with a denatured matrix. Complete healing was seen in the AB group after 28 days with skin appendages similar to normal, while the NHI group showed no appendages in the centre of the actively inflamed area. The α-SMA was found in both groups. Collagen-1 was highly expressed in the NHI group, which led to a scar. Angiogenesis was found more in the AB group. The AB group had shown the capacity to accelerate complete healing and recover skin appendages better than the current protocol.

Therapeutic effects of equine amniotic membrane suspension on corneal re-epithelialization and haze in a modified lagomorph ex vivo wound healing model

OBJECTIVE

To investigate the therapeutic effects of topical equine amniotic membrane (eAM) suspension following corneal wounding in a controlled experimental setting.

PROCEDURES

Equine amniotic membrane was collected, gamma irradiated, homogenized for topical suspension preparation, and cryopreserved. Corneoscleral rims harvested from fresh rabbit globes were wounded via keratectomy and were maintained in an air-liquid interface ex vivo corneal culture model. Treatment groups included topical gamma irradiated eAM suspension (n = 20) and a control group (n = 20). Re-epithelialization of the wound was assessed with daily photographic evaluation of area of fluorescein uptake (mm² ). Corneal wound haze after a 21-day period was assessed by photographic analysis of haze area (mm² ) and pixel intensity (0-255). Histologic processing of corneal tissue was performed, and protein identification of eAM suspension using Liquid chromatography-mass spectrometry (LC-MS).

RESULTS

The average day of complete corneal re-epithelialization in controls (5.5 ± 1.1) and topically treated (5.5 ± 0.6) corneas, and rates of reduction in area of fluorescein uptake over time did not significantly differ (p = .44). The corneal wound haze was significantly reduced in mean area by approximately 52% and intensity by 57% in corneas treated with topical eAM suspension (p < .05), compared to controls 21 days following wounding. Protein analysis identified numerous proteins, specifically decorin, dermatopontin, and lumican, which have previously been documented in eAM.

CONCLUSIONS

Area and intensity of corneal wound haze were significantly reduced in corneas treated with gamma irradiated eAM suspension, which may be due to previously identified therapeutic proteins which promote corneal clarity.

Tissue Engineering in Skin Substitute

Thermal injuries may cause significant damage to large areas of the skin. Extensive and deep burn wounds require specialized therapy. The optimal method in the strategy of treating extensive, full thickness burns (III°) is the use of autologous split thickness skin grafts STSG (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalized patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017). The main limitation of that method is the inadequate amount of healthy, undamaged skin (donor sites), which could be harvested and used as a graft. Moreover, donor sites are an additional wounds that require analgesic therapy, leave scars during the healing process and they are highly susceptible to infection (1-6). It must be emphasized that in terms of the treatment of severe, deep and extensive burns, and there should be no doubt that the search for a biocompatible skin substitute that would be able to replace autologous STSG is an absolute priority. The above-mentioned necessitates the search for new treatment methods of severe burn wounds. Such methods could consider the preparation and application of bioengineered, natural skin substitutes. At present, as the clinical standard considered by the physicians may be use of available biological skin substitutes, e.g., human allogeneic skin, in vitro cultured skin cells, acellular dermal matrix ADM and revitalized ADMs, etc. (Busuioc et al. Rom J Morphol Embryol 4:1061-1067, 2012; Kitala D, Kawecki M, Klama-Baryła A, Łabuś W, Kraut M, Glik J, Ryszkiel I, Kawecki MP, Nowak M. Allogeneic vs. Autologous Skin Grafts in the Therapy of Patients with Burn Injuries: A Restrospective, Open-label Clinical Study with Pair Matching. Adv Clin Exp Med. 2016 Sep-Oct;25(5):923-929.; Glik J, Kawecki M, Kitala D, Klama-Baryła A, Łabuś W, Grabowski M, Durdzińska A, Nowak M, Misiuga M, Kasperczyk A. A new option for definitive burn wound closure - pair matching type of retrospective case-control study of hand burns in the hospitalised patients group in the Dr Stanislaw Sakiel Center for Burn Treatment between 2009 and 2015. Int Wound J. 2017 Feb 21. https://doi.org/10.1111/iwj.12720 . [Epub ahead of print]; Prim et al. May 24Wound Repair Regen., 2017; Grossova et al. Mar 31Ann Burns Fire Disasters 30:5-8, 2017; Łabuś et al. FebJ Biomed Mater Res B Appl Biomater 106:726-733, 2018).

Influence of electron beam irradiation on extracellular matrix of the human allogeneic skin grafts

The nonviable allogeneic human skin grafts might be considered as the most suitable skin substitutes in the treatment of extensive and deep burns. However, in accordance to biological security such grafts require the final sterilization prior to clinical application. The aim of the study was to verify the influence of electron beam irradiation of three selected doses: 18, 25, and 35 kGy on the extracellular matrix of human skin. Prior to sterilization, the microbiological tests were conducted and revealed contamination in all examined cases. Individual groups were subjected to single electron beam radiation sterilization at proposed doses and then subjected to microbiological tests again. The results of microbiological testing performed for all irradiation doses used were negative. Only in the control group was a growth of microorganisms observed. The FTIR spectrometry tests were conducted followed by the histological evaluation and mechanical tests. In addition, cost analysis of radiation sterilization of individual doses was performed. The results of spectroscopic analysis, mechanical tests, and histological staining showed no significant changes in composition and characteristics of tested tissues after their irradiation, in comparison to control samples. The cost analysis has shown that irradiation with 18 kGy is the most cost-effective and 35 kGy is the least favorable. However, according to biological risk reduction, the recommended sterilization dose is 35 kGy, despite the higher price compared to the other doses tested.

A review on the potential of photocatalysis in combatting SARS-CoV-2 in wastewater

Photocatalytic technology offers powerful virus disinfection in wastewater via oxidative capability with minimum harmful by-products generation. This review paper aims to provide state-of-the-art photocatalytic technology in battling transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater. Prior to that, the advantages and limitations of the existing conventional and advanced oxidation processes for virus disinfection in water systems were thoroughly examined. A wide spectrum of virus degradation by various photocatalysts was then considered to understand the potential mechanism for deactivating this deadly virus. The challenges and future perspectives were comprehensively discussed at the end of this review describing the limitations of current photocatalytic technology and suggesting a realistic outlook on advanced photocatalytic technology as a potential solution in dealing with similar upcoming pandemics. The major finding of this review including discovery of a vision on the possible photocatalytic approaches that have been proven to be outstanding against other viruses and subsequently combatting SARS-CoV-2 in wastewater. This review intends to deliver insightful information and discussion on the potential of photocatalysis in battling COVID-19 transmission through wastewater.

The potential of radiation sterilized and banked tissue allografts for management of nuclear casualties

Processed and radiation sterilized allograft tissues that can be banked for use on demand are a precious therapeutic resource for the repair or reconstruction of damaged or injured tissues. Skin dressings or skin substitutes like allograft skin, amniotic membrane and bioengineered skin can be used for the treatment of thermal burns and radiation induced skin injuries. Bone grafts can be employed for repairing fracture defects, filling in destroyed regions of bone, and treatment of spinal and joint injuries. A nuclear scenario would result in a large number of casualties due to the heat, blast and radiation effects of the weapon. Perspective of radiation sterilized biological tissues provided by the tissue banks for management of casualties in a nuclear disaster scenario is presented.

Evaluation of Radiosterilized Glyercerolated Amniotic Membranes as a Substrate for Cultured Human Epithelial Cells

Human amniotic membrane (HAM) is a biomaterial with biological properties beneficial to tissue repair, serving as a substrate for cell cultivation. Irradiation is used for tissue sterilization, but can damage the HAM structure. The objective of this paper was to construct a skin substitute, composed of human keratinocytes cultured on glycerolated HAMs, and to evaluate the influence radiation on subsequent cell culture growth. Four batches of HAMs were glycerolated, and half of them were radio-sterilzed with 25 kGy. Non-irradiated glycerolated HAM (ni-HAM) and irradiated glycerolated HAM (i-HAM) samples were then de-epithelized and analyzed using optical microscopy (Picrossirius staining), immunofluorescence and electron microscopy. Subsequently, keratinocytes were cultured on ni- and i-HAMs, and either immersed or positioned at the air-liquid interface. The basement membranes of the ni-HAM group remained intact following de-epithelialization, whereas the i-HAM group displayed no evidence or remnant presence of these membranes. Concerning the keratinocyte cultures, the ni-HAM substrate promoted the growth of multi-layered and differentiated epithelia. Keratinocytes cultured on i-HAM formed epithelium composed of three layers of stratification and discrete cell differentiation. The glycerolated HAM was compatible with cultured epithelia, demonstrating its potential as a skin substitute. Irradiation at 25 kGy caused structural damage to the amnion.

Preparation of placental tissue transplants and their application in skin wound healing and chosen skin bullous diseases - Stevens-Johnson syndrome and toxic epidermal necrolysis treatment

Unique properties of amniotic membrane make it a promising source for tissue engineering and a clinically useful alternative for patients suffering from chronic wounds including, for example, ulcers, burns, ocular surface damages and wounds occurring in the course of bullous diseases like stevens-johnson syndrome and toxic epidermal necrolysis. Its use has many advantages over standard wound care, as it contains pluripotent cells, nutrients, anti-fibrotic and anti-inflammatory cytokines, growth factors and extracellular matrix (ECM) proteins. Placental tissues can be prepared as a medical component, an advanced therapy medicinal product or a tissue graft. In addition to basic preparation procedures such as washing, rinsing, cutting, drying and sterilisation, there are many optional steps such as perforation, crosslinking and decellularisation. Finally, transplants should be properly stored-in cryopreserved or dehydrated form. In recent years, many studies including basic science and clinical trials have proven the potential to expand the use of amniotic membrane and amnion-derived cells to the fields of orthopaedics, dentistry, surgery, urology, vascular tissue engineering and even oncology. In this review, we discuss the role of placental tissues in skin wound healing and in the treatment of various diseases, with particular emphasis on bullous diseases. We also describe some patented procedures for placental tissue grafts preparation.

How preparation and preservation procedures affect the properties of amniotic membrane? How safe are the procedures?

Human amniotic membrane (AM) has been widely used for tissue engineering and regenerative medicine applications. AM has many favorable characteristics such as high biocompatibility, antibacterial activity, anti-scarring property, immunomodulatory effects, anti-cancer behavior and contains several growth factors that make it an excellent natural candidate for wound healing. To date, various methods have been developed to prepare, preserve, cross-link and sterilize the AM. These methods remarkably affect the morphological, physico-chemical and biological properties of AM. Optimization of an effective and safe method for preparation and preservation of AM for a specific application is critical. In this review, the isolation, different methods of preparation, preservation, cross-linking and sterilization as well as their effects on properties of AM are well discussed. For each section, at least one effective and safe protocol is described in detail.

A single-center, retrospective review of robot-assisted laparoscopic prostatectomy with and without cryopreserved umbilical cord allograft in improving continence recovery

The objective of this study was to evaluate the safety and effectiveness of cryopreserved umbilical cord (UC) allograft as a nerve wrap around the neurovascular bundle (NVB) in accelerating return to continence after radical prostatectomy. A single-center, retrospective study was performed on 200 patients who underwent bilateral, nerve-sparing robot-assisted radical prostatectomy (RARP) with and without placement of UC around the NVBs (n = 100/group). Patients were excluded if they had previous simple or transurethral prostatectomy or history of pelvic radiation. Post-operative continence, defined as 0 or 1 safety pad, was analyzed between groups at 1, 3, 6, and 12 months. Complications, biochemical recurrence and adverse events were assessed to determine safety. Patients who underwent RARP with UC were significantly more likely to be continent at 1 month (65% vs. 44%, p = 0.018), 3 months (83% vs. 70%, p = 0.03), and 12 months (97% vs. 87%, p = 0.009). Sample stratification revealed that UC is beneficial for obese patients and those > 60 years, both of which are high risk for post-RARP incontinence. Biochemical failure was noted in 2 (UC) and 4 (control) patients. No adverse events or complications related to UC were observed. The results suggest that UC allograft is safe and accelerates continence recovery in post-RARP patients. Prospective, randomized trials are warranted.

Biochemical characterization of pure dehydrated binate amniotic membrane: role of cytokines in the spotlight

AIM

Placental allografts used for tissue regeneration differ in membrane compositions and processing techniques. A uniquely folded dehydrated binate amniotic membrane (DBAM) was biochemically characterized to evaluate its potential role in wound healing.

METHODS

Histology, Luminex-based immunoassay and standard in vitro cell biology techniques were employed.

RESULTS

Histological staining confirmed that the DBAM was chorion free with epithelial cell layer of the respective amnion membranes facing outward. DBAM had quantifiable levels of relevant cytokines that induced proliferation and migration while bolstering secretory activity of the cells. DBAM retained biological efficacy at a broad range of temperatures.

CONCLUSION

Cytokines in DBAM stimulate bone marrow stromal and stem cells that may lead to tissue regeneration and wound healing in a clinical setup.

Healing Effects of Dried and Acellular Human Amniotic Membrane and Mepitelas for Coverage of Skin Graft Donor Areas; A Randomized Clinical Trial

Objective

To compare the healing effects of dried and acellular human amniotic membrane and Mepitel for coverage of split-thickness graft donor site (STGDS).

Methods

Twenty patients who underwent STGDS regeneration surgery in identical anatomic regions were enrolled in this randomized controlled clinical trial conducted in Hazrate Fatemeh hospital (Iran). Patients were randomly assigned in 3 groups of wound dressing; group A by Mepitel, group B AmiCare (Dried amniotic membrane) and group C OcuReg-A (Acellular amniotic membrane). Re-epithelization rate (healing time), pain sensation, scar formation and infection rate were assessed till complete healing was achieved.

Results

Our results showed no significant difference between Amicare, OcuReg-A and Mepitel in the features analyzed by us including: Re-epithelization rate (healing time) P value; 0.573, Pain sensation P value: day 4 th: 0.131, day8 th: 0.93 and day 12 th: 0.365, Scar formation P value>0.05and Infection rate.

Conclusion

Our findings confirmed the safety and efficacy of AmiCare (dried amniotic membrane) and OcuReg-A (Acellular amniotic membrane) in treatment of split-thickness donor site in comparison with Mepitel as a standard wound dressing. Trial registration number: IRCT201511118177N12.

Advances of radiation sterilisation in tissue banking

Under the auspices of the IAEA tissue banking programme on "Radiation Sterilisation of Tissue Graft" conducted from 1985 to 2004, many scientists and surgeons were involved in various regional research and development (R&D) projects mainly in dealing with radiation dose selection, radiation effects on human tissues and quality system in radiation sterilisation. New findings on radiation effects, tissue processing and preservation were shared during the regional and interregional meetings and workshops. Many tissue banks started to use radiation (25 kGy) to sterilize tissue grafts for tissue safety and efficacy and still continue to use it. The IAEA Code of Practice for Radiation Sterilization of Tissues Allografts developed in 2007 offered simpler methods to conduct radiation dose setting and dose validation experiments for tissue grafts. Advances in dose selection and dose mapping are continued under the quality management system when banks need to be certified to continue their operation. The combination of good tissue processing and preservation as well as good radiation practice will ensure the tissue products are properly sterilised thus safe and of high quality. Experience in meeting challenges in using radiation sterilisation and achievements reported by the tissue bankers are shared here.

Comparison of impact of two decontamination solutions on the viability of the cells in human amnion

Human amniotic membrane (HAM) is used as an allograft in regenerative medicine or as a source of pluripotent cells for stem cell research. Various decontamination protocols and solutions are used to sterilize HAM before its application, but little is known about the toxicity of disinfectants on HAM cells. In this study, we tested two decontamination solutions, commercial (BASE·128) and laboratory decontamination solution (LDS), with an analogous content of antimycotic/antibiotics for their cytotoxic effect on HAM epithelial (EC) and mesenchymal stromal cells (MSC). HAM was processed in a standard way, placed on nitrocellulose scaffold, and decontaminated, following three protocols: (1) 6 h, 37 °C; (2) 24 h, room temperature; (3) 24 h, 4 °C. The viability of EC was assessed via trypan blue staining. The apoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). The mean % (±SD) of dead EC (%DEC) from six fresh placentas was 12.9 ± 18.1. Decontamination increased %DEC compared to culture medium. Decontamination with BASE·128 for 6 h, 37 °C led to the highest EC viability (81.7%). Treatment with LDS at 24 h, 4 °C resulted in the lowest EC viability (55.9%) in the set. MSC were more affected by apoptosis than EC. Although the BASE·128 expresses lower toxicity compared to LDS, we present LDS as an alternative decontamination solution with a satisfactory preservation of cell viability. The basic formula of LDS will be optimised by enrichment with nutrient components, such as glucose or vitamins, to improve cell viability.

Using Amniotic Membrane as a Novel Method to Reduce Post-burn Hypertrophic Scar Formation: A Prospective Follow-up Study

Background:

Several studies have shown that the application of amniotic membrane as a biological dressing in the management of burns is accompanied by rapid re-epithelialisation. In this follow-up study, we aimed to evaluate the possible role of amniotic membrane as an adjunct to split thickness skin grafting on reducing itching and severity of hypertrophic scar formation.

Materials and Methods:

From October 2013 to January 2015, in a prospective follow-up study, 54 patients (108 limbs) with second and third degree burns, covering 4%–15% of total body surface area (TBSA), were included in the study. All patients needed split-thickness skin grafts for burn-wound coverage. Selected patients had symmetric burns on two (upper or lower) extremities. Then, in every patient, the extremities were randomly divided into two groups: In one limb, the skin graft was traditionally fixed with skin staples (control group) and in the other limb, the skin graft was covered with an amniotic membrane (amnion group). Therefore, in every patient, the graft was covered with an amniotic membrane in one extremity and fixed with skin staples in the other extremity. Finally, after 6 months, the degree of itching and hypertrophic scar formation was compared between the two groups.

Results:

The study group was composed of 108 limbs in 54 patients (27 males and 27 females) with a mean age of 23.54 ± 4.9 years and burn 9.03 ± 2.69% TBSA. The patients were divided into two groups: 54 limbs in amnion group and 54 limbs in control group. In 59.25% of the cases, patient had less itching in the extremity covered with amniotic membrane. Furthermore, in 64.81% of the cases, patients had less hypertrophic scar formation in the extremity covered with amniotic membrane. These differences were statistically significant (P < 0.001).

Conclusions:

Amniotic membrane used as an adjunct in split thickness skin grafting is a novel modality which significantly reduces scar formation and itching that can be greatly distressing to burn patients. However, still more prospective well designed studies are needed to prove it.

Infections in the tissue material and their impact on the loss of transplants in the Laboratory of in vitro Cell and Tissue Culture with Tissue Bank in the years 2011-2015

Radiation sterilization eliminates microbiological infections but causes the degradation of the cell factor. The negative result of microbiological examination for tissue transplants is one of the conditions for approval for distribution in patients. The study attempts to verify impact of the presence of microbes onto material for transplant loss. In the 2011-2015 period, we analyzed 293 donors of skin and amnion. Microbiological sampling was performed. The total of 21 strains of bacteria, molds and fungi was identified in collected tissue. The widest spectrum of strains was found in skin (17), followed by amnia (8). The total number of positive findings was 147 and was again highest in skin (129), while the number of positive findings in amnia was 18 only. The general percentage of fungal infections was very low. The presence of fungal strains was only observed in allogeneic skin (2%). Large number of microorganisms isolated from the skin before sterilization was observed, so it seems impossible to use allogeneic intravital skin. However, the intravital application of allogeneic amnion obtained from cesarean section remains to be considered.

Radiation sterilization of tissue allografts: A review

Tissue substitutes are required in a number of clinical conditions for treatment of injured and diseased tissues. Tissues like bone, skin, amniotic membrane and soft tissues obtained from human donor can be used for repair or reconstruction of the injured part of the body. Allograft tissues from human donor provide an excellent alternative to autografts. However, major concern with the use of allografts is the risk of infectious disease transmission. Therefore, tissue allografts should be sterilized to make them safe for clinical use. Gamma radiation has several advantages and is the most suitable method for sterilization of biological tissues. This review summarizes the use of gamma irradiation technology as an effective method for sterilization of biological tissues and ensuring safety of tissue allografts.

Decellularized human amniotic membrane: how viable is it as a delivery system for human adipose tissue-derived stromal cells?

OBJECTIVES

Human amniotic membrane (HAM) has been widely used in soft tissue engineering both in its fresh form and decellularized; its efficiency to aid treatment of burn injuries is well known. On the other hand, it has been reported clinically by several studies that human adipose-derived stem cells (hADSC) are a promising cell source for cell therapy for burns. Recently, we have reported a new technique for decellularization of HAM. In this study, potential of prepared decellularized HAM (dHAM) as a viable support for proliferation and delivery of hADSC was investigated.

MATERIALS AND METHODS

Amniotic membranes were collected, decellularized and preserved according to the protocol described in our previously published study. hADSC were obtained from the patients undergoing elective liposuction surgery and cells were then seeded on the decellularized membrane for various times. Efficiency of the decellularized membrane as a delivery system for hADSC was investigated by MTT, LDH specific activity, DAPI staining and SEM.

RESULTS

The results showed that dHAM provided a supporting microenvironment for cell growth without producing any cytotoxic effects. In addition, the cells were spread out and actively attached to the dHAM scaffold.

CONCLUSION

These results strongly suggest that dHAMs have considerable potential as 3D cell-carrier scaffolds for delivery of hADSC, in tissue engineering and regenerative medicine applications.

A Novel Approach to Penile Augmentation Urethroplasty Using Buccal Mucosa and Amniotic Membrane: A Pilot Study in a Rabbit Model

OBJECTIVE

To evaluate and compare the success of amniotic membrane (AM) and buccal mucosa (BM) grafts and simultaneous use of both in penile augmentation urethroplasty in rabbits.

MATERIALS AND METHODS

A total of 12 New Zealand rabbits were divided into 3 groups by grafting style: Group 1 (AM), Group 2 (BM), and Group 3 (simultaneous use of BM and AM). In all animals, a standardized urethral defect was created. BM and AM were obtained from the rabbits. Solely AM grafts were affixed to the defects in Group 1, solely BM grafts were affixed to the urethral defects in Group 2, and simultaneous AM + BM grafts were affixed in Group 3. At 4 and 8 weeks, the penises were subject to histological assessment of subepithelial fibrosis, epithelial transformation, and inflammatory reaction.

RESULTS

Stenosis was detected in none of the groups. A dehiscence was developed in one rabbit in Group 1 and a fistula was developed in one rabbit in Group 2. After 4 weeks, minimal subepithelial fibrosis and inflammatory reaction were observed in Group 2, while subepithelial fibrosis was not in Groups 3. After 8 weeks, subepithelial connective tissue proliferation was moderate in Group 2, at both 4th and 8th weeks in Group 2. After 8 weeks, the best epithelial transformations were observed in Group 3.

CONCLUSION

In an animal model, the simultaneous use of AM and BM grafts following acute urethral injury may be feasible for penile augmentation urethroplasty. Further study is needed.

Combination of the buccal mucosa and amniotic membrane: a novel approach for graft augmentation urethroplasty

Today, complicated and long-segment stricture is usually treated by augmentation urethroplasty with buccal mucosa (BM) as the grafted tissue. Augmentation urethroplasty is applied in different parts of the urethra with varying success. Success rate is quite low in one-step penile ventral urethra rehabilitations due to weak subcutaneous tissue in the penile urethra tissue. The amniotic membrane (AM) is a biologically compatible tissue with growth factors, antimicrobial qualities, and immunoregulatory activity that minimizes tissue rejection and scarring. Due to these characteristics, it has been used in various surgical areas, particularly in ophthalmology, with success for more than 50 years. According to our hypothesis, when AM is combined with BM, the success rates in penile ventral augmentation urethroplasty would be increased by decreasing postoperative complications. New evidence could be added to the literature by using AM and BM in combination on an animal model. The positive results of this combined method would give a new point of view to reconstructive urethral surgery practice.

Comparison of cryopreserved amniotic membrane and umbilical cord tissue with dehydrated amniotic membrane/chorion tissue

OBJECTIVE

To evaluate how the different processing methods cryopreservation and dehydration affect the structural integrity and biological composition of key signalling molecules within amniotic membrane and umbilical cord tissues.

METHOD

We directly compared cryopreserved amniotic membrane (AM) and umbilical cord (UC) tissues with dehydrated amniotic membrane/chorion (dHACM) tissue using biochemical and functional assays including histological and histochemical staining, BCA, agarose gel electrophoresis, western blot, ELISA, and proliferation and cell death assays.

RESULTS

Cryopreservation retains the native architecture of the AM/UC extracellular matrix and maintains the quantity and activity of key biological signals present in fresh AM/UC, including high molecular weight hyaluronic acid, heavy chain-HA complex, and pentraxin 3. In contrast, dehydrated tissues were structurally compromised and almost completely lacked these crucial components.

CONCLUSION

The results presented here indicate that cryopreservation better preserves the structural and biological signaling molecules of foetal tissues.

The clinical applications of human amnion in plastic surgery

Since the early 1900s, human amnion has been applied to a wide variety of clinical scenarios including burns, chronic ulcers, dural defects, intra-abdominal adhesions, peritoneal reconstruction, genital reconstruction, hip arthroplasty, tendon repair, nerve repair, microvascular reconstruction, corneal repair, intra-oral reconstruction and reconstruction of the nasal lining and tympanic membrane. Amnion epithelial and mesenchymal cells have been shown to contain a variety of regulatory mediators that result in the promotion of cellular proliferation, differentiation and epithelialisation and the inhibition of fibrosis, immune rejection, inflammation and bacterial invasion. The full repertoire of biological factors that these cells synthesise, store and release and the mechanisms by which these factors exert their beneficial effects are only now being fully appreciated. Although many commercially available biological and synthetic alternatives to amnion exist, ethical, religious, and financial constraints may limit the widespread utilisation of these products. Amnion is widely available, economical and is easy to manipulate, process and store. Although many clinical applications are of historical interest only, amnion offers an alternative source of multi-potent or pluripotent stem cells and therefore may yet have a great deal to offer the plastic surgery and regenerative medicine community. It is the purpose of this article to review the clinical applications of human amnion relevant to plastic surgery.

Effects of gamma irradiation on bacterial microflora associated with human amniotic membrane

Human amniotic membrane is considered a promising allograft material for the treatment of ocular surface reconstruction, burns, and other skin defects. In order to avoid the transmission of any diseases, grafts should be perfectly sterile. Twenty-five amniotic sacs were collected to determine the microbiological quality of human amniotic membrane, to analyze the radiation sensitivity pattern of the microorganism, and to detect the radiation decimal reduction dose (D₁₀) values. All the samples were found to be contaminated, and the bioburden was ranged from 3.4 × 10² to 1.2 × 10⁵ cfu/g. Initially, a total fifty bacterial isolates were characterized according to their cultural, morphological, and biochemical characteristics and then tested for the radiation sensitivity in an incremental series of radiation doses from 1 to 10 KGy. The results depict gradual decline in bioburden with incline of radiation doses. Staphylococcus spp. were the most frequently isolated bacterial contaminant in tissue samples (44%). The D₁₀ values of the bacterial isolates were ranged from 0.6 to 1.27 KGy. Streptococcus spp. were found to be the highest radioresistant strain with the radiation sterilization dose (RSD) of 11.4 KGy for a bioburden level of 1000. To compare the differences, D₁₀ values were also calculated by graphical evaluations of the data with two of the representative isolates of each bacterial species which showed no significant variations. Findings of this study indicate that lower radiation dose is quite satisfactory for the sterilization of amniotic membrane grafts. Therefore, these findings would be helpful to predict the efficacy of radiation doses for the processing of amniotic membrane for various purposes.

Preservation methods of allografts and their (lack of) influence on clinical results in partial thickness burns

Allografts, cadaver skin and amnion membrane are considered the golden standard in the management of partial thickness burns. However, debate on whether the tissue needs to be viable is on-going, since many believe that viable grafts result in better healing. The objective of this literature survey was to analyse the evidence on the method of preservation of allografts (cadaver skin or amnion membrane, glycerol, cryopreservation, lyophilisation) having a clinical impact on the healing of partial thickness burns. The survey focussed on preservation techniques and clinical outcomes (reepithelialisation) in partial thickness burns, as well as on differences in viability, immunogenicity and antimicrobial properties of the preservation methods. Most studies on allograft treatment of partial thickness burns are observational, with only one study of a (historical) comparative nature. A true meta-analysis was not performed and the results of this survey are observational in nature as well: they indicate that there is no evidence that viability of the graft influences healing outcomes. Thus, instead of viability, other aspects, such as intrinsic antimicrobial safety of the preservation method and cost should be the primary criteria for the choice of preservation method to be used for allografts.

Dried gamma-irradiated amniotic membrane as dressing in burn wound care

RATIONALE

Dried amniotic membrane contains collagen matrix and key bioactive molecules like fibronectin, laminin, glycosaminoglycans and elastin. Fresh and cryopreserved human amniotic membrane has been widely explored as a biological dressing. However, fresh and cryopreserved amniotic membranes are not readily available or require special storage conditions. This investigation was aimed to study the functional and clinical efficacy of air-dried radiation sterilized amniotic membranes as dressing in burn wound care.

METHODS

Amniotic membranes collected from placentae of screened donors were processed and sterilized by gamma radiation at 25 kGy. The fluid handling capacity, shelf life and clinical efficacy of air-dried gamma-irradiated amniotic membranes was evaluated.

RESULTS

Fluid handling capacity of the air-dried irradiated amniotic membrane dressing was 3.79-4.2 g/10 cm(2) in 24 h. Infrared (IR) spectral scanning showed no degradation or change in the dried gamma-irradiated amniotic tissue after 2 and 5 years of storage. No effect of storage on the impermeability of the processed amniotic membranes to bacteria was observed. The dried gamma-irradiated amniotic membranes even after 5 years of storage provided an effective barrier to microbial penetration. The dried amniotic membranes were applied to 22 cases of scald, flame and electrical burns. Of the 22 patients studied, 19 patients had excellent results in the form of complete epithelialization of wound with an average healing time of 15-25 days.

CONCLUSION

IR studies and microbial permeability test indicate no qualitative changes in the material property of dried gamma-irradiated amniotic membranes after 2 and 5 years of storage. Air-dried amniotic membrane with the advantage of storage at room temperature as well as functional efficiency is an ideal dressing for burn wound care.

Amniotic membrane grafting in patients with epidermolysis bullosa with chronic wounds

BACKGROUND

Severe forms of epidermolysis bullosa (EB) are characterized by chronic, nonhealing wounds.

OBJECTIVE

We sought to evaluate the usefulness of amniotic membranes in patients with EB.

METHODS

A retrospective chart review of patients with EB who were treated with amniotic membranes (two patients, 8 applications) was conducted. The primary outcome measure was number of days to complete healing, and the secondary outcome measures were a qualitative wound score, a visual analog scale score, and potential adverse effects.

RESULTS

The number of days to detect a significant clinical response, defined as greater than 50% improvement, was 40.3 +/- 21.2 days. The median qualitative wound score was 2 (range 0-5). The mean visual analog scale score at last follow-up was 31.4 +/- 26.8. No adverse events were noted.

LIMITATIONS

Retrospective design, healing assessed by comparing photographs, and partial grafting of some wounds were limitations.

CONCLUSION

This proof-of-concept study revealed the potential usefulness of amniotic membrane grafting in promoting healing of chronic wounds in patients with EB.

Dried irradiated human amniotic membrane as a biological dressing for facial burns--a 7-year case series

BACKGROUND

Facial burns are common and have a significant impact on patient function and psychosocial well being. Human amnion has been used for many years as a temporary biological wound dressing in the management of partial thickness burns. The observed advantages of human amnion treatment include pain relief, ease of use, prevention of infection and acceleration of wound healing.

OBJECTIVE

This study evaluated our 7 years of working with dried irradiated human amnion in the treatment of facial burns.

METHOD

A review of patients, treated with dried human amnion for facial burns between 2001 and 2008. Demographic details collected included age, gender, total facial surface area burned, type of burn and cause of injury. The effectiveness of the treatment was determined by wound infection rate, frequency of dressing reapplication, healing time and resulting scarring.

RESULTS

Thirty-three patients with superficial partial thickness burn were identified (25 males, 8 females). The average age of the patients was 16.5 years (range: 8 months to 64 years). The causes included scalding (n=15), contact burning (n=13) and flash burning (n=5). The mean percent total facial surface area burned was 2.7% (range: 0.5-8.5%). None of the patients developed facial wound infections. Eighty-five percent (n=28) of the patients needed a single application of the dried amnion. The average healing time was 5.4 days (range: 2-14 days). Thirteen patients (39%) had burns confined to the facial area, of which three were discharged and treated as outpatients. Long-term follow up showed two hypopigmented scars, one hyperpigmented scar and one hypertrophic scar.

CONCLUSION

Superficial partial thickness facial burns can be effectively treated with dried irradiated human amnion membrane.

The role of allogenic amniotic membrane in burn treatment

Amniotic membrane (AM) has been used in burns for nearly 100 years. The purpose of this article is to give a comprehensive review of the English literature published in the last two decades (1987--2007) to present the current state of this therapy form. Three medical databases (PubMed, Medline, The Cochrane Library) and specific burn journals were electronically screened for relevant articles using carefully selected retrieval strategies and keywords (AM, amnion grafts, burns, wound dressing, amnion banking). Bibliographies of relevant articles were analyzed for additional pertinent publications. After exclusion of articles which referred to the use of AM in reconstructive and ophthalmologic surgery, the inquiry yielded 31 relevant articles in English language dealing with AM and burns. There was no publication fulfilling the criteria of evidence level I, 6 articles had evidence level II, 10 had evidence level III, 6 had evidence level IV, and 9 were merely narrative (level V). The review testifies to--in view of good tissue practice--heightened use of processed AM in burns, especially in the last decade. Randomized clinical trials favored the use of amnion in burns in the first place for promotion of wound healing and in the second place for its comfortable and less dressing changes. Antimicrobial effects, pain relief, reduction of fluid, and scar formation were demonstrated additionally.