Bioprosthetic Repair Of Complex Duodenal And Abdominal Defects Using Smart Biomaterials

Regenerative surgery is a broad interdisciplinary field that may be functionally defined as the application of regenerative material and techniques such as live cells,genes,smart material,or their combination with surgical methods to affect clinical therapy for disease or restore normal human function.This approach has the potential to transform the surgical treatment for diseases including trauma,cancer,and congenital malformations.The loss of a duodenm and abdominal wall is devastating.Attempts to repair large abdominal and duodenal defects have met with serious problems.We aimed to prepare smart biomaterials,using the principle of regenerative medicine,and to assess the application of this technology in patients with complex duodenal defects and open abdomen.PART I Gastrointestinal regeneration using collagen scaffolds loaded with human collagen-binding bFGF in a porcine modelObjective:Complex duodenal defects and their complications are benign lesions but with malignant outcomes.Although primary repair of duodenal wall defect involving less than 50%of the intestinal circumference is often possible,extensive damage requires wide local drainage after damage control of hemorrhage with temporary closure and resuscitation before delayed enteric reconstruction.Thus,it is very important to promote in situ duodenal regeneration.In the present study,two collagen membrane patches(CBD-bFGF/collagen and PBS/collagen)were developed to bridge the gaps in the duodenum to evaluate the efficacy in the repair of a complex(>50%circumiference)injury and if it could induce intestinal regeneration at the graft site.Methods:Thirty-six China experimental hybrid pigs of either sex,weighing 20-25 kg were randomly divided into two groups,including CBD-bFGF/collagen group and PBS/collagen group.A 3.5-cm long by roughly 2-cm wide section of duodenum was sharply excised from the second portion of the duodenum,approximately 4 cm distal to the pylorus.After 30 minutes of peritoneal soilage,a bioprosthetic repair using collagen membranes was performed.Animals were recovered and resumed a normal diet on day 3.Blood test,imaging examination and operative re-exploration was performed at 1-,4-,and 12-week intervals.All specimens was evaluated by histological analysis.Results:All animals in experimental groups survived after the operation and appeared healthy at the time of observation,with progressive weight gain and normal bowel function.The hepatic enzymes and bilirubin values at different time points post-surgery were within the normal range.No animal had evidence of duodenal stenosis,proximal dilation,or abscess formation.Histological analysis demonstrated collagen/CBD-bFGF promoted more vascularization and smooth muscle cell ingrowth and induced satisfying intestinal histological structures.Conclusions:Bioprosthetic repair of enteric wall defects,even in proximity to upper intestinal secretions,allows successful recovery of bowel function and injury repair without extensive anatomic reconstruction and appears to be an effective strategy for gastrointestinal regeneration.PART Ⅱ Rapidly curable hydrogels as tissue adhesives for protection of microvascular blood flow and wound healing after open abdomen Study one:Rapidly In Situ Forming Platelet-Rich Plasma Gel EnhancesAngiogenic Responses and Augments Early Wound Healing after Open Abdomen Objective:The purposes of our present study were to evaluate the potential of platelet-rich plasma gel to enhance granulation tissue formation after open abdomen and to examine whether the effect was attributable to stimulating rapid neovascularization.Methods:Twenty-four rats underwent colon ascendens stent peritonitis surgery to induce sepsis,followed by intraperitoneal injection of nitrogen to create intra-abdominal hypertension.Four hours later,laparotomies were performed.The rats were randomized into three groups(n=8 for each group):control,platelet-poor plasma(PPP),and platelet-rich plasma(PRP)groups.One week after the treatment,granulation tissue formation and angiogenesis were evaluated by histological and laser Doppler analysis.Results:The resultant platelet count in platelet-rich plasma was higher than that of PPP.The concentrations of platelet-derived growth factor BB,transforming growth factor β－1,and vascular endothelial growth factor in PRP were significantly higher when compared with that of PPP.Myofibroblast count,granulation tissue thickness,vessel numbers,and blood perfusion were increased in PRP group,followed by PPP group,with control being the least.Conclusion:Rapidly in situ forming platelet-rich plasma gel promoted remarkable neovascularization and early wound healing after open abdomen and may lead to novel and effective treatments for open abdominal wounds.Study two:Protection of Colonic Anastomosis with Platelet-rich Plasma Gel in the Open AbdomenObjective:Although evidence for colonic anastomosis in the damage control abdomen continues to accumulate,anastomotic leak is common and associated with greater morbidity.The purpose of our study was to evaluate the effect of platelet-rich plasma(PRP)gel on the healing of colon anastomosis and anastomotic strength in the open abdomen.Methods:PRP was prepared by enriching whole blood platelet concentration from healthy rat.In the rodent model,standard colonic anastomoses followed by closure of abdomen(Control;n=10)and anastomoses followed by open abdomen(OA;n=10)were compared to PRP-sealed anastomoses in open abdomen(OA+PRP;n=10).One week after surgery,body weight,anastomotic bursting pressure,hydroxyproline concentration,and histology of anastomotic tissue were evaluated.Results:All rats survived surgery and had no signs of anastomotic leakage.Compared with the control and PRP group,OA group exhibited a significant decrease in body weight,anastomotic bursting pressure,hydroxyproline concentration,and collagen deposition.No significant difference was detected in these variables between the PRP group and the control group.Conclusion:PRP gel application prevented delayed anastomotic wound healing after open abdomen,which suggested that anastomotic sealing with PRP gel might improve outcome of colonic injuries in the setting of open abdomen.Study three:Granulation tissue formation and microvascular blood flow changes in the small intestinal wall during conventional temporary abdominal closure and temporary abdominal closure using a protective hydrogel over the intestines in laparostomyObjectives:The purposes of our present study were to evaluate the potential of chitosan-PEG(CPT)hydrogel to enhance granulation tissue formation after open abdomen and to evaluate blood flow changes in the intestines during conventional temporary abdominal closure and temporary abdominal closure using a protective hydrogel over the intestines in laparostomy.Methods:A poly(ethylene glycol)modified with tyramine was grafted onto a chitosan backbone to enhance the solubility of the chitosan and to crosslink into three-dimensional networks.The gelation time and the ultrastructure were examined.The hemostatic and bioadhesive property for wound closure were evaluated using twelve healthy male Sprague-Dawley rats of hemorrhaging liver model and twenty-four rats of skin incision model,respectively.Another twelve rats underwent laparotomies,and then were randomized into two groups:control and CPT hydrogel groups.The microvascular blood flow was measured in the intestinal wall before and 24 hours after the treatment,using laser Doppler analysis.One week after the treatment,granulation tissue formation and angiogenesis were evaluated by histological analysis.Results:CPT hydrogels were rapidly formed in situ using horseradish peroxidase and hydrogen peroxide.The hydrogels showed fast gelation,excellent hemostatic property,and strong adhesiveness of skin incisions,suggesting it can be used as tissue adhesive devices for wound.The blood flow of intestine was significantly decreased after the open abdomen with conventional temporary abdominal closure,compared with no decrease after temporary abdominal closure using a protective hydrogel over the intestines in laparostomy.One week after apllication,myofibroblast counts,granulation tissue thickness and vessel numbers were increased in CPT hydrogel group,when compared with control group.Conclusion:Rapidly in situ forming CPT hydrogels,as a ideal adhesives,protect the intestines from ischemia and promote early wound healing after open abdomen and may lead to novel and effective treatments for open abdominal wounds.PART Ⅲ Wound healing of electrospun fibrous membranes containing bFGF loaded nanoparticles after temporary closure of open abdomenObjective:The purposes of our present study were to evaluate the potential of electrospun fibrous membranes containing bFGF loaded nanoparticles to enhance granulation tissue formation after open abdomen.Methods:In this study,pre-formulated dextran glassy nanoparticles(DGNs)loaded with basic fibroblast growth factor(bFGF)were electrospun into a poly(ε-caprolactone)(PCL)polymer fiber to secure the bioactivity of bFGF in a sustained manner and then bioactivity retention was certificated by promoting open abdominal wound healing.Thirty-two rats underwent colon ascendens stent peritonitis surgery to induce sepsis,followed by intraperitoneal injection of nitrogen to create intra-abdominal hypertension.Four hours later,laparotomies were performed.The rats were randomized into four groups(n=8 for each group):control,PCL,bFGF/PCL,and bFGF/DGNs-PCL groups.One week after the treatment,granulation tissue formation and angiogenesis were evaluated by histological analysis.Results:The bFGF can be effectively encapsulated into the dextran glassy nanoparticles and harvested.The bFGF/DGNs-PCL membrane in which bFGF was protected by DGNs has no burst release and a control release kinetic of nearly 30 days.Myofibroblast count,granulation tissue thickness,and vessel numbers were increased in bFGF/DGNs-PCL group,followed by bFGF/PCL group,with control and PCL being the least.Conclusion:Electrospun PCL fibrous membranes containing bFGF loaded nanoparticles could be used for temporary closure of open abdomen and promoted early wound healing after open abdomen,which may lead to novel and effective treatments for open abdominal wounds.