Effects of amniotic membrane on the healing of normal and high-risk colonic anastomoses in rats

Evaluation of colonic anastomosis healing using hybrid nanosheets containing molybdenum disulfide (MOS2) scaffold of human placental amniotic membrane and polycaprolactone (PCL) in rat animal model

Anastomosis is a standard technique following different conditions such as obstruction, tumor, and trauma. Obstruction, adhesion, or anastomosis leakage can be some of its complications. To improve healing and prevent postoperative complications, we design a hybrid scaffold containing acellular human amniotic membranes and polycaprolactone-molybdenum disulfide nanosheets for colon anastomosis. The animal model of colocolonic anastomosis was performed on two groups of rats: control and scaffold. The hybrid scaffold was warped around the anastomosis site in the scaffold group. Samples from the anastomosis site were resected on the third and seventh postoperative days for histopathological and molecular assessments. Histopathologic score and burst pressure had shown significant improvement in the scaffold group. No mortality and anastomosis leakage was reported in the scaffold group. In addition, inflammatory markers were significantly decreased, while anti-inflammatory cytokines were increased in the scaffold group. The result indicates that our hybrid scaffold is a proper choice for colorectal anastomosis repair by declining postoperative complications and accelerating healing.

Biological properties and surgical applications of the human amniotic membrane

The amniotic membrane (AM) is the inner part of the placenta. It has been used therapeutically for the last century. The biological proprieties of AM include immunomodulatory, anti-scarring, anti-microbial, pro or anti-angiogenic (surface dependent), and tissue growth promotion. Because of these, AM is a functional tissue for the treatment of different pathologies. The AM is today part of the treatment for various conditions such as wounds, ulcers, burns, adhesions, and skin injury, among others, with surgical resolution. This review focuses on the current surgical areas, including gynecology, plastic surgery, gastrointestinal, traumatology, neurosurgery, and ophthalmology, among others, that use AM as a therapeutic option to increase the success rate of surgical procedures. Currently there are articles describing the mechanisms of action of AM, some therapeutic implications and the use in surgeries of specific surgical areas, this prevents knowing the therapeutic response of AM when used in surgeries of different organs or tissues. Therefore, we described the use of AM in various surgical specialties along with the mechanisms of action, helping to improve the understanding of the therapeutic targets and achieving an adequate perspective of the surgical utility of AM with a particular emphasis on regenerative medicine.

In vivo performance of a bilayer wrap to prevent abdominal adhesions

There is a high prevalence of intra-abdominal adhesions following bowel resection, which can result in chronic pain, bowel obstruction, and morbidity. Although commercial adhesion barriers have been widely utilized for colonic resections, these barriers do not prevent anastomotic leakage resulting from reduced healing of the anastomosis, which can result in long-term health problems. To address this limitation, we have developed an adhesive bilayer wrap with selective bioactivity to simultaneously prevent intra-abdominal adhesion formation and promote anastomotic healing. Reactive electrospinning was used to generate a crosslinked gelatin mesh to serve as a cell-instructive substrate to improve anastomotic healing. A coating of poly(ethylene glycol) (PEG) foam was applied to the bioactive mesh to generate an antifouling layer and prevent intra-abdominal adhesions. After in vitro confirmation of selective bioactivity, the composite wrap was compared after 2 weeks to a commercial product (Interceed^Ⓡ) in an in vivo rat colonic abrasion model for prevention of intra-abdominal adhesions. The composite bilayer wrap was able to prevent intra-abdominal adhesions when clinical placement was maintained. The composite bilayer wrap was further modified to include tissue adhesive properties for improved efficacy. Preliminary studies indicated that the adhesive composite bilayer wrap maintained a maximum shear strength comparable to Interceed^Ⓡ and greater than fibrin glue. Overall, this work resulted in an initial proof-of-concept device that was shown to effectively prevent intra-abdominal adhesion formation in vivo. The composite bilayer wrap studied here could lead to an improved technology for improved healing of intestinal anastomoses.

Effect of Human Amniotic Membrane on Prevention of Colorectal Anastomosis Leakage in Cases with Neoadjuvant Radiotherapy: An Experimental Animal Study

BACKGROUND

Radiotherapy is one of the most important factors which results in negative effects on wound healing and increases anastomosis leakage. Diverting loop ileostomy has been usually performed after colorectal anastomosis in cases of colorectal cancer with a history of neoadjuvant radiotherapy to decrease the chance of leakage. Considering the side effects of diverting loop ileostomy, the objective of the present study is to investigate the effect of human amniotic membrane (HAM) on colorectal anastomosis leakage after neo-adjuvant radiotherapy.

METHODS

In this experimental animal study, 20 crossbreed rabbits were randomly divided into two groups (case group: 13 rabbits, control group: 7 rabbits) after receiving an equal dose of external beam radiation. Four weeks after irradiation, resection of 4 cm of colorectal segment and end-to-end single layer anastomosis were conducted. In the case group, a 2×2 cm wrap of HAM applied around the site of anastomosis. Eight weeks later, all the survived rabbits were sacrificed. A segment of anastomotic sites was resected in all expired and survived rabbits and sent for pathological evaluation. Mann-Whitney U Test (SPSS for Windows, Ver. 16, Chicago, IL) was applied to analyze healing scores between the two groups.

RESULTS

Due to anastomosis dehiscence, 5 rabbits expired in the control group, but all the 13 rabbits (case group) survived after 8 weeks and showed no leakage. In addition, pathological evaluation revealed significant epithelialization and neovascularization in the case group. Statistically, healing score was higher in the case group rather than the control group (P<0.001).

CONCLUSION

To prevent post irradiation colorectal anastomosis leakage, the use of HAM might play a significant role and a feasible technical approach.

Fibrinogen-thrombin collagen patch reinforcement of high-risk colonic anastomoses in rats

AIM

To evaluate the effectiveness of human fibrinogen-thrombin collagen patch (TachoSil®) in the reinforcement of high-risk colon anastomoses.

METHODS

A quasi-experimental study was conducted in Wistar rats (n = 56) that all underwent high-risk anastomoses (anastomosis with only two sutures) after colectomies. The rats were divided into two randomized groups: Control group (24 rats) and treatment group (24 rats). In the treatment group, high-risk anastomosis was reinforced with TachoSil® (a piece of TachoSil® was applied over this high-risk anastomosis, covering the gap). Leak incidence, overall survival, intra-abdominal adhesions, and histologic healing of anastomoses were analyzed. Survivors were divided into two subgroups and euthanized at 15 and 30 d after intervention in order to analyze the adhesions and histologic changes.

RESULTS

Overall survival was 71.4% and 57.14% in the TachoSil® group and control group, respectively (P = 0.29); four rats died from other causes and six rats in the treatment group and 10 in the control group experienced colonic leakage (P > 0.05). The intra-abdominal adhesion score was similar in both groups, with no differences between subgroups. We found non-significant differences in the healing process according to the histologic score used in both groups (P = 0.066).

CONCLUSION

In our study, the use of TachoSil® was associated with a non-statistically significant reduction in the rate of leakage in high-risk anastomoses. TachoSil® has been shown to be a safe product because it does not affect the histologic healing process or increase intra-abdominal adhesions.

A light-activated amnion wrap strengthens colonic anastomosis and reduces peri-anastomotic adhesions

BACKGROUND AND OBJECTIVE

Colonic anastomotic failure is a dreaded complication, and multiple surgical techniques have failed to eliminate it. Photochemical tissue bonding (PTB) is a method of sealing tissue surfaces by light-activated crosslinking. We evaluated if a human amniotic membrane (HAM), sealed over the anastomotic line by PTB, increases the anastomotic strength.

STUDY DESIGN

Sprague-Dawley rats underwent midline laparotomy followed by surgical transection of the left colon. Animals were randomized to colonic anastomosis by one of the following methods (20 per group): single-layer continuous circumferential suture repair (SR); SR with a HAM wrap attached by suture (SR+ HAM-S); SR with HAM bonded photochemically over the anastomotic site using 532 nm light (SR+ HAM-PTB); approximation of the bowel ends with only three sutures and sealing with HAM-PTB (3+ HAM-PTB). A control group underwent laparotomy alone with no colon resection (NR). Sub-groups (n = 10) were sacrificed at days 3 and 7 post-operatively and adhesions were evaluated. A 6 cm section of colon was then removed and strength of anastomosis evaluated by burst pressure (BP) measurement.

RESULTS

A fourfold increase in BP was observed in the SR+ HAM-PTB group compared to suture repair alone (94 ± 3 vs. 25 ± 8 mm Hg, P < 0.0001) at day 3. At day 7 the burst pressures were 165 ± 40 and 145 ± 31 mm Hg (P = 1), respectively. A significant decrease in peri-anastomotic adhesions was observed in the SR+ HAM-PTB group compared to the SR group at both time points (P < 0.001).

CONCLUSION

Sealing sutured colonic anastomotic lines with HAM-PTB increases the early strength of the repair and reduces peri-anastomotic adhesions. Lasers Surg. Med. 48:530-537, 2016. © 2016 Wiley Periodicals, Inc.

Evaluation of repair in duodenal perforation with human amniotic membrane: An animal model (dog)

Background:

There is a growing tendency toward application of human amniotic membrane (HAM) as a biologic substitute in various tissue injuries where a significant tissue loss is a matter of concern. In gastrointestinal injuries especially duodenal ones, some potential limitations in current surgical techniques contribute to not fully acceptable healing outcomes. Thus, this study was carried out to assess repair with HAM patch for duodenal defect in comparison with simple duodenoraphy in an animal model (dog).

Materials and Methods:

A total of 15 male German shepherd dogs weighing 23-27 kg were randomly divided into two groups. Group A with 10 dogs, which were a candidate for duodenal repair by amniotic membrane patch and Group B consisted of 5 dogs perform simple duodenorraphy. A precise control was made to match all conditions except surgical technique. Macroscopic and microscopic features of the healed duodenal lumen in both groups were recorded.

Results:

Gross evaluation revealed no difference in luminal diameter in both groups. Statistical analysis of duodenal diameter between both groups after operation also showed no significant difference (P_v = 0.789). Histological assessment indicated less inflammation with better wound healing in Group A.

Conclusion:

It seems that repairing duodenal wall defect with HAM would result in better histological outcomes compared with what is seen in simple duodenoraphy in animal models. However, there is no significant difference regarding surgical findings.

External coating of colonic anastomoses: a systematic review

PURPOSE

Colon anastomotic leakage remains both a frequent and serious complication in gastrointestinal surgery. External coating of colonic anastomoses has been proposed as a means to lower the rate of this complication. The aim of this review was to evaluate existing studies on external coating of colonic anastomoses.

METHODS

CINAHL, EMBASE, and PubMed were searched up to September 2011 to identify studies evaluating external coating of colonic anastomoses.

RESULTS

Forty studies have evaluated 20 different coating materials, of which only fibrin sealant, omental pedicle graft, and hyaluronic acid/carboxymethylcellulose have been used in humans. Fibrin sealant has shown positive, however not significant, results. Omental pedicle graft can be used safely, yet without beneficial effects, whereas hyaluronic acid/carboxymethylcellulose should be avoided due to increased complications. The remaining coating materials have solely been evaluated in experimental animals with many contradictory and few positive results.

CONCLUSIONS

External coating of colonic anastomoses has yet failed to show convincing results. Randomized clinical trials and high-quality experimental studies are warranted to determine the role of fibrin sealant, omental pedicle graft, and other coating materials for prevention of colon anastomotic leakage.

Choosing the best animal species to mimic clinical colon anastomotic leakage in humans: a qualitative systematic review

BACKGROUND/AIMS

Animal models are valuable for studying pathogenic factors and preventive measures for colon anastomotic leakage. The suitability of the species as models varies greatly; however, no consensus exists on which species to use. The aim of this review was to evaluate different experimental animals for the study of clinical colon anastomotic leakage.

METHODS

PubMed and REX database were searched up to October 2010 to identify studies evaluating clinical colon anastomotic leakage in animal models and textbooks on experimental animals, respectively.

RESULTS

Functional models of clinical colon anastomotic leakage have been developed in the mouse, pig, rat, dog and rabbit. However, extreme interventions are needed in order to produce clinical leakage in the rat.

CONCLUSION

Despite the wide use of the rat in this field of research, it seems that its resistance to intra-abdominal infection makes clinical leakage difficult to produce thus rendering the rat unsuited as a model. On the basis of the available literature, we recommend using mice as models mimicking clinical colon anastomotic leakage. Pigs may be an alternative; however, the existing models in this animal are less validated and clinically relevant.

Collagen fleeces do not improve colonic anastomotic strength but increase bowel obstructions in an experimental rat model

PURPOSE

To investigate whether a collagen fleece kept in place by fibrin glue might seal off a colorectal anastomosis, provide reinforcement, and subsequently improve anastomotic healing.

METHODS

Wistar rats underwent a 1-cm left-sided colonic resection followed by a 4-suture end-to-end anastomosis. They were then randomly assigned to one of three treatment groups: no additional intervention (control, n = 20), the anastomosis covered with fibrin glue (fibrin glue, n = 20), the anastomosis covered with a collagen fleece, kept in place with fibrin glue (collagen fleece, n = 21). At either 3 or 7 days follow-up, anastomotic bursting pressure was measured and tissue was obtained for histology and collagen content assessment after which animals were sacrificed.

RESULTS

Three rats in the control (15%), three in the fibrin glue (15%), and one in the collagen group (4.8%) died due to anastomotic complications (P = 0.497). Anastomotic bursting pressures were not significantly different between groups at 3 and 7 days follow-up (P = 0.659 and P = 0.427, respectively). However, bowel obstructions occurred significantly more often in the collagen group compared to the control group (14/21 vs. 3/20, P = 0.003). Collagen contents were not different between groups, but histology showed a more severe inflammation in the collagen group compared to the other groups at both 3 and 7 days follow-up.

CONCLUSIONS

A collagen fleece kept in place by fibrin glue does not improve healing of colonic anastomoses in rats. Moreover, this technique induces significantly more bowel obstructions in rats, warranting further study before being translated to a clinical setting.

Covering the colon anastomoses with amniotic membrane prevents the negative effects of early intraperitoneal 5-FU administration on anastomotic healing

PURPOSE

This study investigated whether covering the colonic anastomoses with amniotic membrane (AM) protects the anastomotic healing from the adverse effects of immediate 5-fluorouracil (5-FU) administration.

METHODS

One hundred twenty wistar albino rats were randomized to one of four groups (I-IV, 30 rats in each) and underwent a standardized left colon resection and anastomoses. The anastomoses of the rats in groups II (AM) and IV (5-FU + AM) were covered with AM. Saline solution (2 ml/day; groups I (control) and II) or 5-FU (20 mg/kg/day; groups III (5-FU) and IV) was administered to the rats intraperitoneally once daily from the day of operation until sacrificed. Half of each group was sacrificed on the postoperative day 4 (IA, IIA, IIIA, and IVA) and other half on the postoperative day 8 (IB, IIB, IIIB, and IVB), and their anastomoses were evaluated when sacrificed.

RESULTS

The dehiscence rate of anastomotic dehiscence and adhesion formation were significantly higher in groups IIIA and IIIB compared with groups IVA and IVB, respectively. Bursting pressure was significantly higher in the 5-FU + AM groups than in the 5-FU groups. The inflammatory cell infiltration was significantly lower in groups IIIA and IVA compared with group IA, in groups IIIB and IVB compared with group IB, and in group IVA compared with group IIIA. Neoangiogenesis, fibroblast activity, collagen deposition, and hydroxyproline levels were significantly higher in the 5FU + AM groups compared with control and 5-FU groups. Malondialdehyde levels were significantly higher in the 5-FU groups than in the 5-FU + AM groups.

CONCLUSION

Covering colon anastomoses with AM protects them, preventing leakage and reversing the negative effects of 5-FU administration.