Cryopreserved human amniotic membrane for soft tissue repair in rats

Application of amniotic membranes in reconstructive surgery of internal organs-A systematic review and meta-analysis

Amniotic membrane (AM) has great potential as a scaffold for tissue regeneration in reconstructive surgery. To date, no systematic review of the literature has been performed for the applications of AM in wound closure of internal organs. Therefore, in this systematic review and meta-analysis, we summarize the literature on the safety and efficacy of AM for the closure of internal organs. A systematic search was performed in MEDLINE-PubMed database and OVID Embase to retrieve human and controlled animal studies on wound closure of internal organs. The Cochrane Risk of Bias tool for randomized clinical trials and the SYRCLE risk of bias tool for animal studies were used. Meta-analyses (MAs) were conducted for controlled animal studies to assess efficacy of closure, mortality and complications in subjects who underwent surgical wound closure in internal organs with the application of AM. Sixty references containing 26 human experiments and 36 animal experiments were included. The MAs of the controlled animal studies showed comparable results with regard to closure, mortality and complications, and suggested improved mechanical strength and lower inflammation scores after AM application when compared to standard surgical closure techniques. This systematic review and MAs demonstrate that the application of AM to promote wound healing of internal organs appears to be safe, efficacious, and feasible.

An Evaluation of Wound Healing Efficacy of a Film Dressing Made from Polymer-integrated Amnion Membrane

A film dressing is an easy and common wound management, which is flexible to cover many types of superficial injuries. In a recent study, we developed a scaffold from poly (1,8-octanediolco-citrate) incorporated decellularized amnion membrane (DAM-POC). The DAM-POC scaffold was biocompatible and could enhance soft and hard tissue regeneration when applied to repair the cleft palate in rat. The efficacy of the DAM-POC scaffold in oral repair had led us to hypothesize that it could be employed extensively in the medical field as a wound dressing. This study aimed to investigate the feasibility and efficacy of the DAM-POC scaffold as a film dressing in accelerating wound healing when applied in multiple tissue injuries. Our results demonstrated that both the DAM and DAM-POC scaffolds were biocompatible and anti-adhesive without causing severe foreign body reactions when covering wounds in abdominal wall, back muscle, tibia bone, and liver. In addition, the DAM-POC scaffold was superior to the DAM scaffold in reducing inflammation, preventing fibrosis, and regenerating tissues. In conclusion, the DAM-POC scaffold might potentially be adopted as a film dressing in a wide range of therapeutic applications and healing situations to protect the damaged tissues from the external environment and prevent infections.

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.

Human neonatal stem cell-derived skin substitute improves healing of severe burn wounds in a rat model

Conventional approaches can repair minor skin injuries; however, severe burn injuries require innovative approaches for efficient and better wound repair. Recent studies indicate that stem cell-based regenerative therapies can restore severe damaged skin both structurally and functionally. The current study aims to evaluate the wound healing potential of skin substitute derived from human neonatal stem cells (hNSCs) using a severe burn injury rat model. Amniotic epithelial cells (AECs) and mesenchymal stem cells (MSCs) were isolated from placenta (a source of neonatal stem cells) by explant culture method. After characterization, AECs and umbilical cord-MSCs were differentiated into keratinocyte and fibroblasts, respectively. Morphological changes, and expression of corresponding keratinocyte and fibroblast specific markers were used to verify differentiation into respective lineage. A skin substitute was developed by mixing hNSCs-derived skin cells (hNSCs-SCs) in plasma for transplantation in a rat model of severe burn injury. Results indicated that placenta-derived AECs and MSCs were efficiently differentiated into skin cells, that is, keratinocytes and fibroblasts, respectively, as indicated by morphological changes, immunostaining, and polymerase chain reaction analysis. Further, transplantation of hNSCs-SCs seeded in plasma significantly improved basic skin architecture, re-epithelization rate, and wound healing concurrent with reduced apoptosis. In conclusion, neonatal stem cell-derived skin substitute efficiently improved severe burn wounds in a rat model of burn injury. Unique properties of placenta-derived stem cells make them superlative candidates for the development of "off-the-shelf" artificial skin substitutes for future use.

Human amniotic membrane for guided bone regeneration of calvarial defects in mice

Due to its biological properties, human amniotic membrane (hAM) is widely studied in the field of tissue engineering and regenerative medicine. hAM is already very attractive for wound healing and it may be helpful as a support for bone regeneration. However, few studies assessed its potential for guided bone regeneration (GBR). The purpose of the present study was to assess the potential of the hAM as a membrane for GBR. In vitro, cell viability in fresh and cryopreserved hAM was assessed. In vivo, we evaluated the impact of fresh versus cryopreserved hAM, using both the epithelial or the mesenchymal layer facing the defect, on bone regeneration in a critical calvarial bone defect in mice. Then, the efficacy of cryopreserved hAM associated with a bone substitute was compared to a collagen membrane currently used for GBR. In vitro, no statistical difference was observed between the conditions concerning cell viability. Without graft material, cryopreserved hAM induced more bone formation when the mesenchymal layer covered the defect compared to the defect left empty. When associated with a bone substitute, such improved bone repair was not observed. These preliminary results suggest that cryopreserved hAM has a limited potential for GBR.

What is the benefit of using amniotic membrane in oral surgery? A comprehensive review of clinical studies

OBJECTIVES

Since its first use for the reconstruction of tissue defects in the oral cavity in 1985, human amniotic membrane (hAM) has been widely studied in the field of oral surgery. Despite the growing number of publications in this field, there is no systematic review or meta-analysis concerning its clinical applications, outcome assessments, and relevance in oral surgery. The aim of this review is to provide a thorough understanding of the potential use of hAM for soft and hard tissue reconstruction in the oral cavity.

MATERIALS AND METHODS

A systematic electronic and a manual literature search of the MEDLINE-PubMed database and Scopus database was completed. Patient, Intervention, Comparison and Outcomes (PICO) technique was used to select the relevant articles to meet the objective. Studies using hAM for oral reconstruction, and conducted on human subjects, were included in this survey.

RESULTS

A total of 17 articles were analyzed. Five areas of interest were identified as potential clinical application: periodontal surgery, cleft palate and tumor reconstruction, prosthodontics and peri-implant surgery. Overall, periodontal surgery was the only discipline to assess the efficacy of hAM with randomized clinical trials. The wide variability of preservation methods of hAM and the lack of objective measurements were observed in this study.

CONCLUSION

hAM is already used in the field of oral surgery. Despite this, there is weak clinical evidence demonstrating convincingly the benefit of hAM in this area compared to standard surgery.

CLINICAL RELEVANCE

Several studies now suggest the interest of hAM for periodontal tissue repair. Due to its biological and mechanical properties, hAM seems to be a promising treatment for wound healing in various areas of oral reconstruction. However, further randomized clinical trials are needed to confirm these preliminary results.

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.

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.

Influence of Factors of Cryopreservation and Hypothermic Storage on Survival and Functional Parameters of Multipotent Stromal Cells of Placental Origin

Human placenta is a highly perspective source of multipotent stromal cells (MSCs) both for the purposes of patient specific auto-banking and allogeneic application in regenerative medicine. Implementation of new GMP standards into clinical practice enforces the search for relevant methods of cryopreservation and short-term hypothermic storage of placental MSCs. In this paper we analyze the effect of different temperature regimes and individual components of cryoprotective media on viability, metabolic and culture properties of placental MSCs. We demonstrate (I) the possibility of short-term hypothermic storage of these cells; (II) determine DMSO and propanediol as the most appropriate cryoprotective agents; (III) show the possibility of application of volume expanders (plasma substituting solutions based on dextran or polyvinylpyrrolidone); (IV) reveal the priority of ionic composition over the serum content in cryopreservation media; (V) determine a cooling rate of 1°C/min down to -40°C followed by immersion into liquid nitrogen as the optimal cryopreservation regime for this type of cells. This study demonstrates perspectives for creation of new defined cryopreservation methods towards GMP standards.

The role of adult tissue-derived stem cells in chronic leg ulcers: a systematic review focused on tissue regeneration medicine

Wound healing is an articulated process that can be impaired in different steps in chronic wounds. Chronic leg ulcers are a special type of non-healing wounds that represent an important cause of morbidity and public cost in western countries. Because of their common recurrence after conventional managements and increasing prevalence due to an ageing population, newer approaches are needed. Over the last decade, the research has been focused on innovative treatment strategies, including stem-cell-based therapies. After the initial interest in embryonic pluripotent cells, several different types of adult stem cells have been studied because of ethical issues. Specific types of adult stem cells have shown a high potentiality in tissue healing, in both in vitro and in vivo studies. Aim of this review is to clearly report the newest insights on tissue regeneration medicine, with particular regard for chronic leg ulcers.

Safety of placental, umbilical cord and fetal membrane explants after cryopreservation

There have been studied morphological safety and functional state of the explants of human placenta, umbilical cord and fetal membranes by vital staining techniques using the MTT and resazurin reduction tests, level of glucose in incubation medium, activity of lactate dehydrogenase and alkaline phosphatase before and after cryopreservation. It has been found that proposed program of cryopreservation allows keeping a high level of viability of the explants of placenta, umbilical cord and fetal membranes, the most informative methods of assessing the safety of these biological objects before and after cryopreservation are method of vital staining, determination of glucose content in incubation medium, MTT-test and resazurin reduction test.

The use of temporalis muscle graft, fresh and cryopreserved amniotic membrane in preventing temporomandibular joint ankylosis after discectomy in rabbits

PURPOSE

The aim of the study was to evaluate the efficacy of temporalis muscle-fascia graft, fresh and cryopreserved human amniotic membrane as an interpositional material in preventing temporomandibular joint ankylosis in a rabbit model.

MATERIALS AND METHODS

In this experimental study, 21 New Zealand white rabbits were used. The condyle and the joint disc were removed to induce ankylosis in left TMJs. Reconstruction was immediately performed with temporalis muscle-fascia graft (tMFG) in group I (n = 7), fresh human amniotic membrane (fHAM) in group II (n = 7) and cryopreserved human amniotic membrane (cHAM) in group III (n = 7). All rabbits were sacrificed at 3 months after the operation. The comparison was made among three groups by means of vertical mouth opening and weight measurements, radiologic and histologic findings obtained before and after surgery.

RESULTS

In all rabbits, there was no statistically significant difference in the jaw movements and weight among groups at commencement and 3 months after surgery. The condylar surfaces were more irregular in HAM groups. There were mild osteophyte formations, sclerosis, fibrosis and calcification around the condyle in all groups however the joint gap was more preserved in group I. All interpositional materials were also seen to be partially present in the joint gap at 3 months. Ankylosis was not seen in the joint gap in any group.

CONCLUSION

With the results of this study it was concluded that interpositional arthroplasty with HAM and tMFG have an almost similar effect in preventing TMJ ankylosis after discectomy in the rabbit model.

Effect of Hypericum perforatum on intraperitoneal adhesion formation in rats

INTRODUCTION

The aim of this study was to evaluate the efficacy of Hypericum perforatum for prevention of adhesion formation in rats.

MATERIAL AND METHODS

Twenty-four female wistar rats underwent left uterine horn adhesion model. Rats were randomised into 4 groups. Group 1 (Control): Closure of abdominal incision without any agent administration. Group 2: Closure of incision after administration of intraperitoneal (i.p.) Ringer's lactate solution. Group 3: Closure of incision after administration of i.p. olive oil (diluent of H. perforatum). Group 4: Hypericum perforatum extract (Ecodab(®)) was administered i.p. before the closure of incision. Fourteen days later, relaparatomy was performed and surgical adhesion scores, inflammation and fibrosis scores were noted. Groups were compared according to these scores.

RESULTS

There was statistical significant difference between ringer's lactate group and olive oil group according to surgical adhesion score (p = 0.009). However, groups were not different according to inflammation and fibrosis scores (p > 0.05).

CONCLUSIONS

Despite antiinflammatory, antioxidants and antimicrobial properties of H. perforatum, our results revealed no positive effect of H. perforatum on the prevention of intraperitoneal adhesion formation.

Prevention of intraabdominal adhesions by local and systemic administration of immunosuppressive drugs

Background:

Intraperitoneal adhesion formation is a serious postsurgical issue. Adhesions develop after damage to the peritoneum by surgery, irradiation, infection or trauma.

Objectives:

Using a rat model, we compared the effectiveness of systemic and intraperitoneally administered common immunosuppressive drugs for prevention of postoperative intraperitoneal adhesions.

Materials and Methods:

Peritoneal adhesions were induced in 98 female Wistar-Albino rats by cecal abrasion and peritoneal excision. Rats were randomly separated into seven groups, each containing fourteen rats, and the standard experimental model was applied to all of rats. 14 days later, rats were euthanized, intraperitoneal adhesions were scored and tissues were examined histologically using hematoxylin/eosin and Masson’s trichrome staining.

Results:

Throughout the investigation, no animal died during or after surgery. In all of experimental groups, decrease in fibrosis was statistically significant. Decrease in fibrosis was most prominently in intraperitoneal tacrolimus group (P = 0.000), and decrease was least in intraperitoneal cyclosporine group (P = 0.022). Vascular proliferation was significantly decreased in all experimental groups (P < 0.05) except for systemic tacrolimus group (P = 0.139). Most prominent reduction in vascular proliferation was in intraperitoneal tacrolimus group (P = 0.000).

Conclusions:

Administration of immunosuppressive drugs is effective for prevention of intraperitoneal adhesions.

Repair of oronasal fistulae by interposition of multilayered amniotic membrane allograft

BACKGROUND

Oronasal fistulas are a frequent complication after cleft palate surgery. Numerous repair methods have been described, but wound-healing problems occur often. The authors investigated, for the first time, the suitability of multilayered amniotic membrane allograft for fistula repair in a laboratory experiment (part A), a swine model (part B), and an initial patient series (part C).

METHODS

In part A, one-, two-, and four-layer porcine and human amniotic membranes (n = 20 each) were fixed in a digital towing device and the force needed for rupture was determined. In part B, iatrogenic oronasal fistulas in 18 piglets were repaired with amniotic membrane allograft, autofetal amniotic membrane, or small intestinal submucosa (n = 6 each). Healing was evaluated by probing and visual inflammation control (no/moderate/strong) on postoperative days 3, 7, 10, and 76. Histological analysis was performed to visualize tissue architecture. In part C, four patients (two women and two men, ages 21 to 51 years) were treated with multilayered amniotic membrane allograft.

RESULTS

In part A, forces needed for amniotic membrane rupture increased with additional layers (p < 0.001). Human amniotic membrane was stronger than porcine membrane (p < 0.001). In part B, fistula closure succeeded in all animals treated with amniotic membrane with less inflammation than in the small intestinal submucosa group. One fistula remained persistent in the small intestinal submucosa group. In part C, all fistulas healed completely without inflammation.

CONCLUSIONS

Amniotic membrane is an easily available biomaterial and can be used successfully for oronasal fistula repair. The multilayer technique and protective plates should be utilized to prevent membrane ruptures.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Side dependent effects of the human amnion on angiogenesis

INTRODUCTION

Amnion (AM), the innermost layer of human placenta, has a variety of functions such as capability to reduce scarring and inflammation, as well as anti-microbial and immunoregulatory properties. However, there are challenging reports about angiogenic and anti-angiogenic effects of the AM. The aim of this study was to evaluate whether the angiogenesis is dependent on epithelial or mesenchymal sides of this membrane.

METHODS

Dorsal skinfold chamber model was performed on male rats. A layer of dorsal skin of rats was removed and the AM was implanted in either epithelial side up or mesenchymal side up position. Intra-vital microscopy was done one week after tissue transplantation. In vitro evaluation of angiogenesis was also performed using rat aortic ring assay on the AM.

RESULTS

The number of vessel sprouts and their lengths were increased more significantly in epithelial side up group comparing to the control group. Inhibitory effect of epithelial side of the AM on angiogenesis was clearly seen in mesenchymal side up group. Both number and length of sprouts in mesenchymal up group were decreased in comparison to epithelial side up group. In aortic ring assay, angiogenesis was detected on the AM after removal of the amniotic epithelial cells.

DISCUSSION & CONCLUSION

This study showed that the AM has both angiogenic and anti-angiogenic properties, which is surface dependent. Therefore, the AM can have a vast application in both ischemic organs through inducing angiogenesis and pathological situations such as cancer in which angiogenesis must be inhibited.

Concise review: role of mesenchymal stem cells in wound repair

Wound healing requires a coordinated interplay among cells, growth factors, and extracellular matrix proteins. Central to this process is the endogenous mesenchymal stem cell (MSC), which coordinates the repair response by recruiting other host cells and secreting growth factors and matrix proteins. MSCs are self-renewing multipotent stem cells that can differentiate into various lineages of mesenchymal origin such as bone, cartilage, tendon, and fat. In addition to multilineage differentiation capacity, MSCs regulate immune response and inflammation and possess powerful tissue protective and reparative mechanisms, making these cells attractive for treatment of different diseases. The beneficial effect of exogenous MSCs on wound healing was observed in a variety of animal models and in reported clinical cases. Specifically, they have been successfully used to treat chronic wounds and stimulate stalled healing processes. Recent studies revealed that human placental membranes are a rich source of MSCs for tissue regeneration and repair. This review provides a concise summary of current knowledge of biological properties of MSCs and describes the use of MSCs for wound healing. In particular, the scope of this review focuses on the role MSCs have in each phase of the wound-healing process. In addition, characterization of MSCs containing skin substitutes is described, demonstrating the presence of key growth factors and cytokines uniquely suited to aid in wound repair.

Repair of oronasal fistulas with human amniotic membrane in minipigs

We evaluated the use of multilayer human amniotic membrane (HAM) as a grafting material for the repair of mid-palate oronasal fistulas in seven Berlin minipigs. After two weeks, three animals had the fistulas repaired with multilayered HAM grafts, three had them repaired with a collagen-based dermal substitute (INTEGRA((R)), Integra Life Sciences, Plainsboro, NJ, USA), and one fistula was left untreated to serve as a control. Grafts were interposed between the oral and nasal mucosa, traversing the fistulas. After healing for 40 days, the pigs were killed for clinical, histological, and immunohistochemical examination. Two of the three fistulas closed with HAM were successful, the diameter of the third was reduced in size, and there was no change in the diameter of the fistula in the control. This study shows successful closure of oronasal fistulas in minipigs using interposed grafts of cryopreserved HAM, and offers promise as a simple and effective technique for tension-free closure of such fistulas.

Reduction of postsurgical adhesions in a rat model: a comparative study

BACKGROUND

Adhesion formation after peritoneal surgery is a major cause of postoperative bowel obstruction, infertility, and chronic pelvic pain. In this study, we compared the possible individual effects of phosphatidylcholine (PC), Seprafilm II, and tissue plasminogen activator (t-PA) and the combined effects of phosphatidylcholine and t-PA on postoperative adhesion formation in a rat surgical model.

MATERIALS AND METHODS

A total of 50 Wistar male rats underwent median laparotomy and standardized abrasion of the visceral and parietal peritoneum. phosphatidylcholine, Seprafilm II, and t-PA alone and phosphatidylcholine and t-PA in combination were applied intraperitoneally at the end of the surgical procedure. Seven days after surgery, a relaparotomy was performed for adhesion grading and histopathological examination.

RESULTS

A comparison of adhesion stages demonstrated a significant difference between the control group and the study groups (p<0.001). The adhesion grade of the combined treatment group was statistically different from that of the other groups (p<0.05). In the t-PA group and the combined group, six and two rats, respectively, developed hematomas locally on the cecum.

CONCLUSIONS

PC, t-PA, and Seprafilm II used individually reduced the adhesion grade. The t-PA and phosphatidylcholine combination was most effective in reducing adhesion formation. On the other hand, usage of t-PA alone or in combination may increase risk of bleeding. More detailed studies are needed, and future studies on the efficacy of a material for decreasing adhesion formation should include a comparison of several control materials in the same model.