Enhanced intestinal anastomotic healing with gelatin hydrogel incorporating basic fibroblast growth factor

Endothelial progenitor cells for fabrication of engineered vascular units and angiogenesis induction

The promotion of vascularization and angiogenesis in the grafts is a crucial phenomenon in the healing process and tissue engineering. It has been shown that stem cells, especially endothelial progenitor cells (EPCs), can stimulate blood vessel formation inside the engineered hydrogels after being transplanted into the target sites. The incorporation of EPCs into the hydrogel can last the retention time, long-term survival, on-target delivery effects, migration and differentiation into mature endothelial cells. Despite these advantages, further modifications are mandatory to increase the dynamic growth and angiogenesis potential of EPCs in in vitro and in vivo conditions. Chemical modifications of distinct composites with distinct physical properties can yield better regenerative potential and angiogenesis during several pathologies. Here, we aimed to collect recent findings related to the application of EPCs in engineered vascular grafts and/or hydrogels for improving vascularization in the grafts. Data from the present article can help us in the application of EPCs as valid cell sources in the tissue engineering of several ischemic tissues.

Double-layer adhesives for preventing anastomotic leakage and reducing post-surgical adhesion

Preventing anastomotic leakage (AL) and postoperative adhesions after gastrointestinal surgery is crucial for ensuring a favorable surgical prognosis. However, AL prevention using tissue adhesives can unintentionally lead to undesirable adhesion formation, while anti-adhesive agents may interfere with wound healing and contribute to AL. In this study, we have developed a double-layer patch, consisting of an adhesive layer on one side, utilizing gallic acid-conjugated chitosan (CHI-G), and an anti-adhesive layer on the opposite side, employing crosslinked hyaluronic acid (cHA). These CHI-G/cHA double-layer adhesives significantly prevented AL by forming physical barriers of CHI-G and reduced post-surgical adhesion at the anastomosis sites by the anti-adhesive layers of cHA. The bursting pressure (161.1 ± 21.6 mmHg) of double-layer adhesives-applied rat intestine at postoperative day 21 was far higher than those of the control (129.4 ± 5.7 mmHg) and the commercial anti-adhesives-applied group (120.8 ± 5.2 mmHg). In addition, adhesion score of double-layer adhesives-applied rat intestine was 3.6 ± 0.3 at postoperative day 21, which was similar to that of the commercial anti-adhesives-applied group (3.6 ± 0.3) and lower than that of the control group (4.9 ± 0.5). These findings indicate that the double-layer patch (CHI-G/cHA) has the potential to effectively prevent both postoperative adhesions and anastomotic leakage, offering a promising solution for gastrointestinal surgery.

Advances in Hydrogel Adhesives for Gastrointestinal Wound Closure and Repair

Millions of individuals undergo gastrointestinal (GI) tract surgeries each year with common postoperative complications including bleeding, perforation, anastomotic leakage, and infection. Today, techniques such as suturing and stapling seal internal wounds, and electrocoagulation stops bleeding. These methods induce secondary damage to the tissue and can be technically difficult to perform depending on the wound site location. To overcome these challenges and to further advance wound closure, hydrogel adhesives are being investigated to specifically target GI tract wounds because of their atraumatic nature, fluid-tight sealing capability, favorable wound healing properties, and facile application. However, challenges remain that limit their use, such as weak underwater adhesive strength, slow gelation, and/or acidic degradation. In this review, we summarize recent advances in hydrogel adhesives to treat various GI tract wounds, with a focus on novel material designs and compositions to combat the environment-specific challenges of GI injury. We conclude with a discussion of potential opportunities from both research and clinical perspectives.

Perioperative intrapelvic hyaluronate application as prophylaxis against complications following rectal anastomotic dehiscence: An experimental study

PURPOSE

The aim of this experimental study was to test the method of prevention of postoperative complications, especially infectious, in partial dehiscence following stapler anastomosis in rectal surgeries.

METHODS

The method includes the application of a hyaluronic acid-based gel in combination with triclosan, which has antibacterial properties. The gel was applied to the space around the rectum with an artificial, precisely defined dehiscence so that the dehiscence was separated from the rest of pelvis and the peritoneal cavity to avoid the spread of infection. The study included 30 female pigs. The rectosigmoid colon was mobilized and transected completely. Anastomosis was constructed with circular staplers. A perforator was then used to create precisely defined artificial dehiscence. Subsequently the lesser pelvis was filled with hyaluronic gel such that the site of artificial dehiscence was covered completely.

RESULTS

All animals survived for 14 days until the second-look revision with no signs of failure in the anastomosis healing, local inflammation, and sepsis or postoperative complications, such as chills, refusal of liquid or feed, abdominal distension, and bowel obstruction.

CONCLUSION

Hyaluronic acid applied as a precursor solution around the rectal anastomosis fills the lesser pelvis perfectly. It prevents the leakage of intestinal contents in the lesser pelvis. Triclosan as an antibacterial substance prevents the spread of inflammation in the pelvis or even in the abdominal cavity.

Reinforcement of Colonic Anastomosis with Improved Ultrafine Nanofibrous Patch: Experiment on Pig

Anastomotic leakage is a dreadful complication in colorectal surgery. It has a negative impact on postoperative mortality, long term life quality and oncological results. Nanofibrous polycaprolactone materials have shown pro-healing properties in various applications before. Our team developed several versions of these for healing support of colorectal anastomoses with promising results in previous years. In this study, we developed highly porous biocompatible polycaprolactone nanofibrous patches. We constructed a defective anastomosis on the large intestine of 16 pigs, covered the anastomoses with the patch in 8 animals (Experimental group) and left the rest uncovered (Control group). After 21 days of observation we evaluated postoperative changes, signs of leakage and other complications. The samples were assessed histologically according to standardized protocols. The material was easy to work with. All animals survived with no major complication. There were no differences in intestinal wall integrity between the groups and there were no signs of anastomotic leakage in any animal. The levels of collagen were significantly higher in the Experimental group, which we consider to be an indirect sign of higher mechanical strength. The material shall be further perfected in the future and possibly combined with active molecules to specifically influence the healing process.

Engineering Tough, Injectable, Naturally Derived, Bioadhesive Composite Hydrogels

Engineering mechanically robust bioadhesive hydrogels that can withstand large strains may open new opportunities for the sutureless sealing of highly stretchable tissues. While typical chemical modifications of hydrogels, such as increasing the functional group density of crosslinkable moieties and blending them with other polymers or nanomaterials have resulted in improved mechanical stiffness, the modified hydrogels have often exhibited increased brittleness resulting in deteriorated sealing capabilities under large strains. Furthermore, highly elastic hydrogels, such as tropoelastin derivatives are highly expensive. Here, gelatin methacryloyl (GelMA) is hybridized with methacrylate-modified alginate (AlgMA) to enable ion-induced reversible crosslinking that can dissipate energy under strain. The hybrid hydrogels provide a photocrosslinkable, injectable, and bioadhesive platform with an excellent toughness that can be tailored using divalent cations, such as calcium. This class of hybrid biopolymers with more than 600% improved toughness compared to GelMA may set the stage for durable, mechanically resilient, and cost-effective tissue sealants. This strategy to increase the toughness of hydrogels may be extended to other crosslinkable polymers with similarly reactive moieties.

Development of hyaluronan-based membranes for the healing of intestinal surgical wounds: a preliminary study

Implantable membranes based on alginate and hyaluronic acid (HA) were manufactured to obtain a rapidly resorbing pliable mesh for the in situ administration of HA to intestinal tissue. Morphological analyses of this interpenetrated matrix pointed out a homogeneous polymeric texture while degradation studies demonstrated that the material is able to dissolve in physiological solutions within few days. Biological studies in vitro showed that the membrane is biocompatible towards human dermal fibroblasts and that liquid extracts from the HA-containing membrane can stimulate wound healing. A preliminary in vivo biocompatibility study on rats showed that the membranes in direct contact with the intestine did not elicit any acute adverse reaction or immune response, while only a mild inflammatory reaction was noticed at the mesenteric or serosal region. Overall, these results appear to support the application of these polysaccharide-based materials for intestinal wound healing.

A Comparison of Conventional Collagen Sponge and Collagen-Gelatin Sponge in Wound Healing

The objective of this study was to compare the effectiveness of the collagen-gelatin sponge (CGS) with that of the collagen sponge (CS) in dermis-like tissue regeneration. CGS, which achieves the sustained release of basic fibroblast growth factor (bFGF), is a promising material in wound healing. In the present study, we evaluated and compared CGSs and conventional CSs. We prepared 8 mm full-thickness skin defects on the backs of rats. Either CGSs or CSs were impregnated with normal saline solution (NSS) or 7 μg/cm(2) of bFGF solution and implanted into the defects. At 1 and 2 weeks after implantation, tissue specimens were obtained from the rats of each group (n = 3, total n = 24). The wound area, neoepithelial length, dermis-like tissue area, and the number and area of capillaries were evaluated at 1 and 2 weeks after implantation. There were no significant differences in the CGS without bFGF and CS groups. Significant improvements were observed in the neoepithelial length, the dermis-like tissue area, and the number of newly formed capillaries in the group of rats that received CGSs impregnated with bFGF. The effects on epithelialization, granulation, and vascularization of wound healing demonstrated that, as a scaffold, CGSs are equal or superior to conventional CSs.

Colorectal anastomotic healing: why the biological processes that lead to anastomotic leakage should be revealed prior to conducting intervention studies

BACKGROUND

Anastomotic leakage (AL) remains the most dreaded complication after colorectal surgery and causes high morbidity and mortality. The pathophysiology of AL remains unclear, despite numerous studies that have been conducted on animals and humans, probably due to the undetermined healing process of colorectal anastomoses. Increasing basic knowledge on this healing process may shed more light on causal factors of AL, and additionally reduce the quantity and accelerate the quality of experimental studies. In this debate article, our aim was to provide different perspectives on what is known about the colorectal healing process in relation to wound healing and AL.

DISCUSSION

Since knowledge on anastomotic healing is lacking, it remains difficult to conclude which factors are essential in preventing AL. This is essential information in the framework of humane animal research, where the focus should lie on Replacement, Reduction and Refinement (3Rs). While many researchers compare anastomotic healing with wound healing in the skin, there are substantial recognized differences, e.g. other collagen subtypes and different components involved. Based on our findings in literature as well as discussions with experts, we advocate stop considering anastomotic healing in the gastrointestinal tract and cutaneous healing as a similar process. Furthermore, intervention studies should at least address the anastomotic healing process in terms of histology and certain surrogate markers. Finally, the anastomotic healing process ought to be further elucidated - with modern techniques to achieve 3Rs in animal research--to provide starting points for potential interventions that can prevent AL.

Proapoptotic effect of control-released basic fibroblast growth factor on skin wound healing in a diabetic mouse model

The ability of basic fibroblast growth factor (bFGF) to improve wound healing is attenuated by its short half-life in free form. This study aimed to enhance skin wound healing in a diabetes mouse model while concomitantly decreasing scar formation using control-released bFGF together with acidic gelatin hydrogel microspheres (AGHMs). Bilateral full-thickness wounds (10 mm in diameter) were made on the backs of db/db mice. Forty-five mice were divided into three groups, and the base of the wound under the panniculus carnosus and the wound periphery were injected with phosphate-buffered saline (300 μL) containing (1) control-released bFGF (50 μg), (2) control-released bFGF (20 μg), or (3) AGHMs alone. The size of the wound area was recorded on each postoperative day (POD). Mice were sacrificed on postoperative day 4, 7, 10, 14, and 28, and skin wound specimens were obtained to assess the endothelium/angiogenesis index via cluster of differentiation 31 immunohistochemistry, the proliferation index via Ki-67 immunohistochemistry, and the myofibroblast and fibroblast apoptosis indices by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and alpha-smooth muscle actin or vimentin staining, respectively. Epithelialization rates and indices of proliferation and myofibroblast/fibroblast apoptosis were higher in the bFGF groups than in the AGHM group, mainly within 2 weeks of injury. No dose-effect relationship was found for control-released bFGF, although the actions of 50 μg bFGF seemed to last longer than those of 20 μg bFGF. Therefore, control-released bFGF may accelerate diabetic skin wound healing and induce myofibroblast/fibroblast apoptosis, thereby reducing scar formation.