Elucidating the fundamental fibrotic processes driving abdominal adhesion formation

Biomimetic nanostructural materials based on placental amniotic membrane-derived nanofibers for self-healing and anti-adhesion during cesarean section

Cesarean section (CS) is highly prevalent surgery among females. However, current absorbable anti-adhesion membranes used clinically can partially prevent postoperative adhesions but show limited efficacy in tissue regeneration, leaving post-cesarean women at risk for severe complications including cesarean scar pregnancy, placenta previa, and uterine rupture. Herein, we designed a fully amniotic membrane (AM)-derived biomimetic nanostructural materials (AM-BNMs) as an anti-adhesion barrier, and validated its therapeutic efficacy in a rat CS model. The biomaterial consisted of AM-extracellular matrix (ECM) nanofibers, enriched with hemostatic proteins (collagen, S100A8, S100A9, etc.), carrying AM mesenchymal stem cells (MSCs)-secretome that exhibited significantly elevated levels of pro-regenerative factors (miR-302a-3p, angiogenin, VEGF, etc.) compared to endogenous secretion. The reconstituted AM-BNMs demonstrated synergistic effects at CS wounds, effectively preventing adhesion formation while promoting hemostasis and tissue regeneration. In summary, this readily accessible human-derived biomaterial shows promising potential in preventing adhesion-related complications and enhancing uterine wound healing, thereby promoting female reproductive health.

A dynamically phase-adaptive regulating hydrogel promotes ultrafast anti-fibrotic wound healing

Achieving rapid and scar-free wound repair is a key goal in the field of regenerative medicine. Herein, a dynamically Schiff base-crosslinked hydrogel (F/R gel) with phase-adaptive regulating functions is constructed to integratedly promote rapid re-epithelization with suppressed scars on chronic infected wounds. Specifically, the gel effectively eliminates multidrug-resistant bacterial biofilm at infection stage via antimicrobial activity of ε-polylysine firstly dissociated from hydrogel matrix in infectious microenvironment, and interrupts the severe oxidative stress-inflammation cycle at wound site by the released ceria nanozyme, thus stimulating a pro-regenerative environment to ensure tissue repair. Subsequently, fibroblast growth factor/c-Jun siRNA co-loaded microcapsules gradually disintegrate to release drugs, facilitating neoangiogenesis and cell proliferation but simultaneously blocking c-Jun overexpression for fibrotic scar suppression. Notably, the F/R gel facilitates normal-like skin regeneration with no perceptible scars formed on infected male mouse wound and female rabbit ear wound models. Our work offers a promising regenerative strategy emphasizing immunomodulatory and fibroblast subtype modulation for scarless wound repair.

Tissue-Adhesive, Antibacterial, and Antioxidant Hydrogel Sealant for Sealing Colorectal Anastomotic Leakage and Preventing Postoperative Adhesion

Surgical treatment of colorectal diseases typically involves excising the diseased portion of the bowel and anastomosing the remaining sections to reestablish continuity. Surgical suturing has limitations in preventing anastomotic leakage and postoperative adhesion. To address these challenges, a tissue-adhesive, antibacterial, and antioxidant hydrogel is designed to cover and seal colorectal anastomotic wounds. The hydrogel is formed in situ by simply mixing oxidized hyaluronic acid, adipic acid dihydrazide-modified hyaluronic acid, ε-poly-l-lysine, and tannic acid. The hydrogel exhibits a rapid gelation rate and self-healing ability. Compared with commercial fibrin glue, the hydrogel has superior tissue-adhesive strength and wound sealing performance. The hydrogel displays potent reactive oxygen species scavenging ability and antibacterial activity against both Gram-positive and Gram-negative bacteria. The hydrogel also exhibits good biodegradation and biocompatibility. In a cecum-abdominal wall adhesion model in rats, the hydrogel attaches firmly to the injured tissues and serves as a physical barrier to prevent adhesion formation. In anastomotic leakage models after colon resection in rats and rabbits, the hydrogel effectively seals the anastomotic leakage, prevents postoperative adhesion, and promotes anastomotic healing. Thus, this multifunctional hydrogel has strong clinical potential for preventing anastomotic leakage and adhesion formation after colorectal surgery.

An anti-inflammatory and anti-fibrotic Janus hydrogel for preventing postoperative peritoneal adhesion

Postoperative peritoneal adhesion (PPA) is pathological tissue hyperplasia between surgical wounds and nearby organs. Currently, traditional double-sided bioadhesives are limited in preventing PPA due to the indiscriminate adhesive properties and the poor interaction with wet tissues. Herein, we developed a Janus hydrogel, named PAA-Cos, by using the polycationic carbohydrate polymer of chitooligosaccharide (Cos) and the polyanionic polymer of polyacrylic acid (PAA). The adhesive layer of Janus hydrogels could adhere to wet tissue tightly due to surfaces composed of carboxyls, and the positively charged biomaterial (Cos) neutralized carboxyls on one side of PAA hydrogel to form Janus hydrogels. Moreover, PAA-Cos can further load with ligustrazine hydrochloride (Ligu), a pharmaceutical compound with anti-inflammatory and anti-fibrotic effects, finally obtaining PAA-Cos@Ligu. After the application of PAA-Cos@Ligu on the surgical trauma, the bottom surface can adhere to wet tissues robustly to restore the wound, while the top surface acts as a physical barrier with antiadhesive effects to avoid PPA. PAA-Cos@Ligu also exhibited anti-inflammatory effects by promoting M2 macrophage polarization, inhibiting the myofibroblast-like differentiation of peritoneal mesothelial cells, and blocking the TGF-β/Smad2/3 signaling pathway to hinder collagen deposition. Our findings suggest that PAA-Cos@Ligu has great potential as an anti-adhesion candidate with biocompatibility and ease of preparation.

Nanotechnology-Based Therapies for Preventing Post-Surgical Adhesions

Adhesions are the body's natural response to various inflammatory causes, with surgery being the most common cause. However, the formation of postoperative adhesions can lead to significant complications, including intestinal obstruction and chronic pain. To prevent such postoperative complications associated with adhesions, developing effective strategies for adhesion prevention has been a major focus of research. Currently, several therapeutic models have been developed to achieve this objective. These include pharmaceuticals, inert polymers, functional biomaterials, and nanotherapeutics. Among the various strategies developed, nanotherapeutics, though still in its early stages, has shown promise as a potential approach. Other therapeutic models are associated with adverse side effects and complications related to their application. On the other hand, nanotherapeutic models are able to overcome the limitations of the other strategies and provide their own set of unique advantages. Hence, nanotherapeutics represents a promising area for further research. Further efforts should be made to refine existing nanotherapeutics for clinical application while also addressing associated safety and ethical concerns related to their use in medical practice. Therefore, this article aims to review the various nanotherapeutic approaches developed for the prevention of postoperative adhesions, explore their regulatory pathways, and discuss associated safety and ethical concerns.

StatGel: An Innovative hydrogel carrying STAT3-targeted small molecule inhibitor for the treatment of abdominal adhesions

Adhesions in the abdominal cavity are among the most common complications post abdominal surgery, resulting from excessive fibrous tissue proliferation and collagen synthesis due to various factors. To date, physical barrier materials have been approved for preventing adhesions, though their effectiveness remains unsatisfactory. One of the important causes of abdominal adhesions is the excessive proliferation of fibrotic cells, and our previous research indicated that STAT3 is a promising therapeutic target for anti-fibrosis. This study designed and synthesized a STAT3 targeted small molecule inhibitor compound 16 K and evaluated its anti-fibrotic effects using the CCK-8 assay on fibroblasts. Compound 16 K was then combined with GelMA (methacryloyl gelatin) hydrogel through UV curing to prepare StatGel, a 16 K-loaded hydrogel with both anti-fibrotic activity and physical barrier properties. Material property assessments showed that StatGel does not alter the inherent properties of GelMA while maintaining the capability of sustained release of compound 16 K. StatGel significantly inhibited the proliferation of L929 cells and TGF-β1-induced fibrotic differentiation, and down-regulated p-STAT3 protein without affecting the STAT3 protein. Furthermore, StatGel was demonstrated to prevent the formation of abdominal adhesions in a mouse model induced by CLP as assessed by histological examination and adhesion index. Overall, StatGel offers a potential approach for effectively preventing the formation of abdominal adhesions.

Postoperative adhesions are abrogated by a sustained-release anti-JUN therapeutic in preclinical models

Postoperative abdominal adhesions are the leading cause of bowel obstruction and a cause of chronic pain and infertility. Adhesion formation occurs after 50 to 90% of abdominal operations and has no proven preventative or treatment strategy. Abdominal adhesions derive primarily from the visceral peritoneum and are composed of polyclonally proliferating tissue-resident fibroblasts. We have previously shown that signaling of the transcription factor JUN regulates adhesiogenesis and that a small-molecule JUN inhibitor (T-5224) decreases adhesion formation. Here, we encapsulated T-5224 in a shear-thinning hydrogel with antiadhesion properties for intraperitoneal postoperative delivery and sustained release of a JUN inhibitor for adhesion prevention. The material properties of the T-5224-hydrogel support its use for open or minimally invasive surgical application. We found this therapeutic system to be safe, well tolerated, and efficacious in murine and porcine preclinical models. T-5224-hydrogel minimized adhesion quantity and also diminished adhesion fibrosis at an ultrastructural level. Moving toward clinical translation, we developed a large mammal adhesion model in pigs with bowel resection. Single-cell transcriptomic analysis showed that JUN and associated pathway signaling were diminished in adhesion-derived fibroblasts treated with T-5224-hydrogel. The JUN-inhibiting T-5224-hydrogel provided robust prevention of adhesion without deleterious effects on bowel anastomosis or abdominal wall healing. Adhesion biology is similar across surgical sites, and, therefore, this formulation has potential for applicability across the body. The development of therapeutics to prevent adhesions is of paramount importance with potential for high-impact translation to patient care to address a common, unmet clinical need.

Janus decellularized membrane with anisotropic cell guidance and anti-adhesion silk-based coatings for spinal dural repair

The repair of soft tissues with anisotropic structures, such as spinal dura mater, requires the use of biomaterials to guide tissue directional growth while minimizing epidural fibrotic adhesion. Herein, we construct the Janus small intestinal submucosa (SIS) via silk-based hydrogel coatings, which provides extracellular matrix-mimicking features and anti-adhesion performance for spinal dural defect repair. We demonstrate that the silk fibroin and methacrylated silk fibroin (SilMA) composite microgroove hydrogel coating at the inner surface via water vapor annealing treatment exhibits excellent structure stability, stable attachment to SIS substrate, and shows orientated cell morphology and extracellular matrix produced by fibroblasts, good histocompatibility and promotes the polarization of macrophages towards the anti-inflammatory phenotype. The methacrylated hyaluronic acid and SilMA composite coating outer surface serves as favorable physical barrier shows effective resistance to protein adsorption, cell and tissue adhesion, and can mitigate fibrosis reactions. Spinal dura mater defect experiments on male rats demonstrate that the Janus SIS simultaneously promotes dural regeneration and inhibits epidural fibrosis.

Mesothelial cell responses to acute appendicitis or small bowel obstruction reactive ascites: Insights into immunoregulation of abdominal adhesion

Previous abdominal surgery (PAS) increases risk of small bowel obstruction (SBO) due to adhesions, and appendectomy (appy) is an independent risk factor for abdominal adhesion-related complications. Peritoneal inflammation, e.g., acute appendicitis (AA), causes formation of reactive ascitic fluid (rA) that activates peritoneum surface mesothelial cells (MCs) to form adhesions. Pathologic adhesions may arise if restoration of MC-regulated fibrinolysis and secretion of glycocalyx (GCX) are disrupted. Proteins affecting these processes may originate from peritoneal rA. This is a prospective observational IRB-approved study at three Level 1 trauma centers where rA is collected prior to surgical intervention for non-perforated AA or adhesiolysis for SBO. Samples from 48 appy and 15 SBO patients were used to treat human MCs and subjected to quantification of 85 inflammatory mediators. Results were compared between patients with surgically naïve abdomens (naïve) and patients with >1 PAS. Select rA caused MCs to form clusters of fibroblastic cells, extracellular matrix fibers (FIB), and secretion of GCX. PAS and naïve patient rA fluids were clustered into "fiber-GCX" (FIB-GCX) groups: highFIB-highGCX, highFIB-lowGCX, noFIB-highGCX, noFIB-lowGCX, and noFIB-noGCX. Between groups, 26 analytes were differentially abundant including innate immune response, wound healing, and mucosal defense proteins. Factors that contributed to the differences between groups were rA-induced highFIB and history of PAS. Overall, PAS patient rA showed a muted immune response compared to rA from naïve patients. Our data suggest that abdominal surgery may negatively impact future immune responses in the abdomen. Further, quantifying immunomodulators in peritoneal rA may lead to the development a personalized approach to post-surgical adhesion treatment and prevention.

Human placental stem cell-based therapies for prevention of abdominal adhesions: A prospective randomized preclinical trial

BACKGROUND

Abdominal adhesions are networks of fibrotic tissues that form between organs postoperatively. Current prophylactic strategies do not reproducibly prevent adhesive small bowel obstruction across the entire abdomen. Human placental-derived stem cells produce an anti-inflammatory secretome that has been applied to multiple fibrosing diseases. The purpose of this project is to test human placental stem cell (hPSC)-based therapies for prevention of abdominal adhesions in a clinically relevant rat model.

METHODS

Fifty-four (n = 54, n = 6/group) male Sprague-Dawley rats (250-350 g) underwent model creation and treatment randomization under anesthesia. Experimental groups included human placental-derived stem cells (hPSC, 5 × 106 cells/10 mL Plasmalyte A), human placental-derived stem cells in a hyaluronic acid (HA-Mal-hPSC) hydrogel, the human placental-derived stem cell secretome from conditioned media in 10 mL Plasmalyte A, human placental-derived stem cells' conditioned media in a hyaluronic acid (HA-Mal-CM) hydrogel, Plasmalyte A (media alone, 10 mL), hyaluronic acid hydrogel alone (HA-Mal), Seprafilm (Baxter, Deerfield, IL), and the control groups, model with no treatment (MNT) and sham animals. Treatments were administered intraperitoneally, and the study period was 14 days postoperation. Adhesions were scored at necropsy and analyzed as the difference between means of an index statistic (Animal Index Score) versus MNT. Underlying molecular mechanisms were explored by functional genomic analysis and histology of peritoneal tissues.

RESULTS

Hyaluronic acid hydrogel alone, HA-Mal-CM hydrogel, and Seprafilm significantly reduced the overall appearance of abdominal adhesions by mean Animal Index Score at 14 days versus MNT. Human placental stem cell, HA-Mal-hPSC hydrogel, HA-Mal-CM hydrogel, HA-Mal hydrogel alone, and Seprafilm significantly reduced the collagen content of injured peritoneal tissues. Human placental stem cell and HA-Mal-hPSC hydrogel suppressed expression of the most profibrotic genes. Conditioned media, HA-Mal hydrogel alone, and media alone significantly altered the expression of proteins associated with peritoneal fibrotic pathways.

CONCLUSION

Human placental stem cell-based therapies reduce abdominal adhesions in a prospective randomized preclinical trial. This effect is supported by suppression of profibrotic genomic and proteomic pathways.

The multiple roles of macrophages in peritoneal adhesion

Peritoneal adhesion (PA) refers to the abnormal adhesion of the peritoneum either with the peritoneum itself or with tissues and organs that is caused by abdominopelvic surgery, abdominal infection or peritoneal inflammation. PA is associated with various clinical complications, such as abdominal pain and distension, intestinal obstruction, gastrointestinal disorders and female infertility, and adversely affects the quality of life of patients. Macrophages are essential for PA formation and can undergo polarization into classically activated macrophages (M1) and alternatively activated macrophages (M2), which are influenced by the peritoneal microenvironment. By releasing proinflammatory cytokines and reactive oxygen species, M1 macrophages promote peritoneal inflammatory reactions and the resultant formation of adhesion. In contrast, M2 macrophages secrete anti-inflammatory cytokines and growth factors to inhibit PA formation and to promote repair and healing of peritoneal tissues, and thereby play a significant anti-inflammatory role. This review comprehensively explores the function and mechanism of macrophages and their subtypes in PA formation to gain insight into the prevention and treatment of PA based on the modulation of macrophages.

Engineered Lubricative Lecithin-Based Electrospun Nanofibers for the Prevention of Postoperative Abdominal Adhesion

Background: Postoperative abdominal adhesion is a prevalent complication following abdominal surgery, with the incidence of adhesion reaching up to 90%, which may precipitate a range of adverse outcomes. Although fibrous membranes loaded with various anti-inflammatory or other drugs have been proposed for anti-adhesion, most of them suffer from drug-induced adverse effects. Methods: In this study, a lecithin-based electrospun polylactic acid (PLA) nanofibrous membrane (L/P-NM) was developed for the prevention of postoperative abdominal adhesion, utilizing the hydration lubrication theory. The loaded zwitterionic lecithin allows the nanofiber surface to strongly bind water molecules to create a hydration lubrication interface. Results: As the TGA results show, the content of bound water in the nanofibers increased significantly with the increase in the lecithin content. Tribological test results show that L/P-NM reached a minimum coefficient of friction (COF) of about 0.112. Additionally, the developed nanofibrous membranes possess favorable tensile property and biocompatibility. Rat postoperative abdominal adhesion model evaluation results demonstrated that L/P-NM possesses significant anti-adhesive performance, with an adhesion score of only 1. Conclusions: Therefore, this study offers a promising strategy for efficiently preventing abdominal adhesion.

Construction of a Curcumin‐Loaded PLLA/PCL Micro‐Nano Conjugated Fibrous Membrane to Synergistically Prevent Postoperative Adhesion From Multiple Perspectives

Postoperative adhesion (POA) has emerged as a prevalent clinical challenge in soft tissue repair, emphasizing the critical need for preventive measures. However, the complex POA development process makes POA prevention from a single aspect insufficient. Hence, a curcumin‐loaded poly‐L‐lactic acid‐poly (caprolactone) micro‐nano conjugated fibrous membrane (PAPC MCFM (cur)) is engineered to synergistically prevent POA from multiple perspectives, in which poly (caprolactone) (PCL) nanofibers (118 ± 12 nm) with low orientation traverse the oriented poly‐L‐lactic acid (PLLA) microfibers (2.0 ± 0.3 µm). The PAPC MCFM not only significantly improves the mechanical properties of the anisotropic fibrous membrane (AIFM) that the modulus of elasticity and the tensile strength in the direction vertical to microfiber orientation increase by 4.5 and 13.0 times, respectively, but also can further enhance the “contact guidance effect” of AIFM, i.e., hindering fibroblast adhesion, proliferation, and differentiation to myofibroblast through inhibiting integrin β1 activation, vinculin expression and focal adhesion (FA) formation, and the nuclear localization activation of yes‐associated protein (YAP). Except for these effects, PAPC MCFM loading with 2.5 mg mL−1 curcumin can further prevent POA by delivering anti‐inflammatory, antioxidant, and antibacterial properties, and by suppressing fibrosis through decreased transforming growth factor‐β1(TGF‐β1) expression, showing effective POA prevention in rat abdominal cavity and rabbit dura mater models.

A biodegradable shape memory polyurethane film as a postoperative anti-adhesion barrier for minimally invasive surgery

Postoperative adhesions commonly form in various tissues, resulting in serious implications and an increased risk of secondary surgery. The application of anti-adhesion films as physical barriers has proven effective in reducing adhesion incidence and severity. However, existing anti-adhesion films require manual deployment during minimally invasive surgery, posing inconvenience and possibility of further injury. To address these limitations, we have developed an intelligent anti-adhesion film based on shape memory polyurethane. In this work, a linear shape memory polyurethane (ISO2-PU), incorporating hexamethylene isocyanate and isosorbitol as hard segments and poly(D, L-lactic acid) macrodiol as soft segments, was fabricated into an anti-adhesion film. The favorable shape memory effect of the ISO2-PU film ensures its convenient delivery and automatic unfolding, as revealed by a simulation experiment for endoscopic surgical implantation. Furthermore, the glass transition temperature (Tg) close to body temperature endows the ISO2-PU film with good mechanical compliance, thus ensuring a reliable fit with the wounded tissue to avoid undesired folding. Finally, in vivo experiments using a rat cecal abdominal wall injury model demonstrated that the combination of reliable fit, appropriate degradation rate, and good cytocompatibility promises the ISO2-PU film with high anti-adhesion efficacy. This work validates the concept of shape memory anti-adhesion barrier and expands future directions for advanced anti-adhesion biomaterials. STATEMENT OF SIGNIFICANCE: Postoperative adhesions are a common complication that occurs widely after various surgeries. This work developed an intelligent anti-adhesion film based on a linear shape memory polyurethane (ISO2-PU). This film is featured with remarkable shape memory effect and mechanical compliance at body temperature, appropriate degradability, and good cytocompatibility. These merits ensure convenient delivery and smart unfolding of ISO2-PU film during minimally invasive surgery and favorable postoperative anti-adhesion efficacy. The results validate the concept of shape memory anti-adhesion barrier and paves a way for designing next-generation anti-adhesion biomaterials.

The Toll-like receptor 4 antagonist TAK-242 in combination with sodium hyaluronate alleviates postoperative abdominal adhesion in a mouse model

Postoperative abdominal adhesion is one of the most common complications after abdominal surgery. The Toll-like receptor 4 (TLR4) signaling pathway is one of the most common inflammation-related pathways, and it has been demonstrated that TLR4 is highly expressed in adhesive tissues; however, the function of TLR4 in adhesion formation has not yet been studied. In the present study, the expression of TLR4 was first detected by immunohistochemical (IHC) and double-immunofluorescence staining in 40 mice, which were randomly divided into four groups, and sacrificed at 1, 3, 5 and 7 days after surgery. Subsequently, another 40 mice were randomly divided into five groups; with the exception of the sham group, the other groups were modeled and treated with saline that contained DMSO, sodium hyaluronate (HA), TAK-242 or TAK-242 + HA (applied to damaged peritoneal wounds). A total of 7 days after surgery, the mice were sacrificed and specimens were collected. Inflammation was detected by hematoxylin and eosin staining, and ELISA of transforming growth factor- β1 (TGF-β1) and interleukin-6 (IL-6); collagen deposition was examined by Masson staining and IHC staining of α-SMA; and reactive oxygen species (ROS) were detected by ROS staining and malondialdehyde (MDA) assay. The results revealed that TLR4 was highly expressed in the adhesive tissues at 3, 5 and 7 days after surgery. In addition, TAK-242 + HA treatment could reduce abdominal adhesion formation, exhibiting lower Nair's score and inflammation scores, lower TGF-β1 and IL-6 levels, and lower collagen thickness and α-SMA levels compared with those in the control group. In addition, the TAK-242 + HA group had lower levels of ROS and MDA compared with those in the control group. The present study revealed that TLR4 was highly expressed in the process of adhesion formation and its inhibitor, TAK-242, combined with HA, could reduce adhesion formation by reducing inflammation and ROS, and alleviating collagen deposition.

A self-fused peptide-loaded hydrogel with injectability and tissue-adhesiveness for preventing postoperative peritoneal adhesions

Peritoneal adhesions commonly occur following abdominal or pelvic surgery and can cause serious complications. Currently, physical barriers are the primary approach used in clinical practice to prevent adhesion, although their effectiveness is frequently inadequate. In this study, we developed an injectable peptide-loaded hydrogel with multiple functions, including self-fusion, tissue-adhesiveness, anti-inflammation, anti-cell adhesion and anti-angiogenesis. To assess the effectiveness of these hydrogels, which are stabilized by dynamic imine bonds and acetal connections, in preventing postoperative abdominal adhesions, we utilized both a rat abdominal adhesion model and a rat model simulating repeated-injury adhesions. In comparison to the commercially available HA hydrogel, as-prepared hydrogels exhibited significant reductions in inflammation, fibrosis, and angiogenesis, leading to an obvious decrease in peritoneal adhesions. Moreover, this peptide-loaded hydrogel demonstrated an ideal degradation time, maintaining an in vivo viability for about 10 days. We believe this peptide-loaded hydrogel presents a promising solution for the challenging clinical issue of postoperative abdominal adhesions.

A Scoping Review of Animal Models for Development of Abdominal Adhesion Prevention Strategies

INTRODUCTION

Abdominal adhesions represent a chronic postsurgical disease without reliable prophylaxis. Animal modeling has been a cornerstone of novel therapeutic development but has not produced reliable clinical therapies for prevention of adhesive small bowel obstruction. The purpose of this scoping review is to analyze animal models for abdominal adhesion generation by key considerations of external validity (i.e., fidelity, homology, and discrimination).

METHODS

A literature review was performed in accordance with the Preferred Reporting Items for Systematic Reviews Extension for Scoping Reviews guidelines. Peer-reviewed publications were included that described the development or quality assessment of experimental animal models for abdominal adhesions with inclusion of a scoring system. Studies that focused on treatment evaluation, implantation of surgical devices, models of nonsurgical etiologies for abdominal adhesions, non-in vivo modeling, and investigations involving human subjects were excluded.

RESULTS

Four hundred and fifteen (n = 415) articles were identified by prespecified search criteria. Of these, 13 studies were included for review.

CONCLUSIONS

Translation of investigational therapeutics for abdominal adhesion prevention is dependent upon high-quality experimental animal models that reproduce the clinical adhesions seen in the operating room as a disease of the entire abdomen.

A retrospective analysis of perioperative complications of lateral approach lumbar interbody fusion in patients with prior abdominal surgery or a history of colonic inflammatory disease

BACKGROUND CONTEXT

Lateral approaches for lumbar interbody fusion (LIF) allow for access to the lumbar spine and disc space by passing through a retroperitoneal corridor either pre- or trans-psoas. A contraindication for this approach is the presence of retroperitoneal scarring that may occur from prior surgical intervention in the retroperitoneal space or from inflammatory conditions with fibrotic changes and pose challenges for the mobilization and visualization needed in this approach. However, there is a paucity of evidence on the prevalence of surgical complications following lateral fusion surgery in patients with a history of abdominal surgery.

PURPOSE

The primary aim of this study is to describe the association between surgical complications following lateral interbody fusion surgery and prior abdominal surgical.

STUDY DESIGN

Retrospective study.

PATIENT SAMPLE

Patients over the age of 18 who underwent lateral lumbar interbody fusion at a large, tertiary care center between 2011 and 2019 were included in the study.

OUTCOME MEASURES

The primary outcome included medical, surgical, and thigh-related complications either in the intraoperative or 90-day postoperative periods. Additional outcome metrics included readmission rates, length of stay, and operative duration.

METHODS

The electronic health records of 250 patients were reviewed for demographic information, surgical data, complications, and readmission following surgery. The association of patient and surgical factors to complication rate was analyzed using multivariable logistic regression. Statistical analysis was performed using R statistical software (R, Vienna, Austria).

RESULTS

Of 250 lateral interbody fusion patients, 62.8% had a prior abdominal surgery and 13.8% had a history of colonic disease. The most common perioperative complication was transient thigh or groin pain/sensory changes (n=62, 24.8%). A multivariable logistic regression considering prior abdominal surgery, age, BMI, history of colonic disease, multilevel surgery, and the approach relative to psoas found no significant association between surgical complication rates and colonic disease (OR 0.40, 95% CI 0.02-2.22) or a history of prior abdominal surgeries (OR 0.56, 95% CI 0.20-1.55). Further, the invasiveness of prior abdominal surgeries showed no association with overall spine complication rate, lateral-specific complications, or readmission rates (p>.05).

CONCLUSION

Though retroperitoneal scarring is an important consideration for lateral approaches to the lumbar spine, this study found no association between lateral lumbar approach complication rates and prior abdominal surgery. Further study is needed to determine the impact of inflammatory colonic disease on lateral approach spine surgery.

A Single-Component Janus Zwitterionic Hydrogel Patch with a Bionic Microstructure for Postoperative Adhesion Prevention

The development of anti-adhesion hydrogels for preventing postoperative adhesions is an ongoing challenge, particularly in achieving a balance between exceptional antifouling properties and effective in situ tissue retention. In this study, we propose a unique approach with the design of a single-component Janus zwitterionic hydrogel patch featuring a bionic microstructure. The Janus patches were prepared through free radical polymerization of sulfobetaine methacrylate with N, N'-methylenebis(2-propenamide) as the cross-linker. The incorporation of hexagonal facets separated by interconnecting grooves on one side imparts durable and reliable in situ retention capabilities to the Janus hydrogel patch when it is applied to traumatized tissues. The opposing flat surface exhibits outstanding resistance to bacteria, proteins, and cell adhesion, due to the superhydrophilicity and excellent antifouling characteristics of zwitterionic polymers. This dual functionality empowers the Janus hydrogel patch to mitigate adhesions between traumatized and surrounding tissues. The hexagonal and groove bionic microstructures facilitate rapid drainage, promoting swift contact with the tissue for increased adhesion strength, while independent hexagonal microfacets enhance the peeling energy. In an in vivo setting, Janus zwitterionic hydrogel patches with surface microstructures form mutually embedded structures with the cecum surface, minimizing the likelihood of slippage and detachment. Remarkably, in vivo experiments involving abdominal wall cecum injuries illustrate the Janus zwitterionic hydrogel patch's superior anti-adhesion effectiveness compared to commercial controls. Thus, the Janus hydrogel patch, distinguished by its bionic microstructure surface, presents substantial potential in the biomedical field for averting postoperative adhesions.

A novel electrospun polylactic acid silkworm fibroin mesh for abdominal wall hernia repair

Objective

Abdominal wall hernias are common abdominal diseases, and effective hernia repair is challenging. In clinical practice, synthetic meshes are widely applied for repairing abdominal wall hernias. However, postoperative complications, such as inflammation and adhesion, are prevalent. Although biological meshes can solve this problem to a certain extent, they face the problems of heterogeneity, rapid degradation rate, ordinary mechanical properties, and high-cost. Here, a novel electrospinning mesh composed of polylactic acid and silk fibroin (PLA-SF) for repairing abdominal wall hernias was manufactured with good physical properties, biocompatibility and low production cost.

Materials and methods

FTIR and EDS were used to demonstrate that the PLA-SF mesh was successfully synthesized. The physicochemical properties of PLA-SF were detected by swelling experiments and in vitro degradation experiments. The water contact angle reflected the hydrophilicity, and the stress‒strain curve reflected the mechanical properties. A rat abdominal wall hernia model was established to observe degradation, adhesion, and inflammation in vivo. In vitro cell mesh culture experiments were used to detect cytocompatibility and search for affected biochemical pathways.

Results

The PLA-SF mesh was successfully synthesized and did not swell or degrade over time in vitro. It had a high hydrophilicity and strength. The PLA-SF mesh significantly reduced abdominal inflammation and inhibited adhesion formation in rat models. The in vitro degradation rate of the PLA-SF mesh was slower than that of tissue remodeling. Coculture experiments suggested that the PLA-SF mesh reduced the expression of inflammatory factors secreted by fibroblasts and promoted fibroblast proliferation through the TGF-β1/Smad pathway.

Conclusion

The PLA-SF mesh had excellent physicochemical properties and biocompatibility, promoted hernia repair of the rat abdominal wall, and reduced postoperative inflammation and adhesion. It is a promising mesh and has potential for clinical application.

A Zwitterionic Hydrogel with Anti-Oxidative and Anti-Inflammatory Properties for the Prevention of Peritoneal Adhesion by Inhibiting Mesothelial-Mesenchymal Transition

Postoperative peritoneal adhesion is a serious clinical complication. Various hydrogel barriers have been developed to prevent peritoneal adhesion. However, it remains a challenge to design a hydrogel with desirable physicochemical properties and bioactivities. In this study, a zwitterionic polysaccharide-based multifunctional hydrogel is developed using epigallocatechin-3-gallate (EGCG) to prevent postoperative abdominal adhesion. This hydrogel is simple to use and has desirable properties, such as excellent injectability, self-healing, and non-swelling properties. The hydrogel also has ultralow fouling capabilities, such as superior bactericidal performance, cell and protein adhesion, and low immunogenicity resistance. Moreover, the hydrogel exhibits good antioxidant activity, which is attributed to the integration of EGCG. Furthermore, the detailed mechanism from in vivo and in vitro experimental studies illustrates that hydrogel compositions can synergistically prevent adhesion formation through multiple pathways, including anti-inflammatory and antioxidant capabilities and inhibition effects on the mesothelial-mesenchymal transition (MMT) process induced by transforming growth factor (TGF-β). In summary, this zwitterionic multifunctional hydrogel has great potential to prevent postoperative adhesion formation in the clinical setting.

A Strong Adhesive Biological Hydrogel for Colon Leakage Repair and Abdominal Adhesion Prevention

Colon leakage is one of the most severe complications in abdominal trauma or surgery cases. It can lead to severe abdominal infection and abdominal adhesions, resulting in prolonged hospital stays and increased mortality. In this study, a photosensitive hydrogel is proposed, which can swiftly form a strong adhesion coating on the damaged colon after UV irradiation, to realize quick cure and suture-free repair of colon leakage. The newly developed biological gel consists of hyaluronic acid methacryloyl (HAMA) and hyaluronic acid o-nitroso benzaldehyde (HANB) in the optimal ratio of 3: 1, which exerts both the rapid photocuring properties of HAMA and the strong tissue adhesion properties of HANB. HAMA/HANB shows excellent adhesion stability on wet surfaces, presenting controllable mechanical properties, ductility, adhesion stability, and chemical stability; it also evades foreign body response, which relieves the degree of abdominal adhesion. The underlying mechanism for HAMA/HANB promoting wound healing in colon leakage involves the reconstruction of the colon barrier, as well as the regulation of the immune reaction and neovascularization. In all, HAMA/HANB is a promising alternative suture-free approach for repairing colon leakage; it has a reliable healing effect and is expected to be extended to clinical application for other organ injuries.

Multifunctional hydrogels: advanced therapeutic tools for osteochondral regeneration

Various joint pathologies such as osteochondritis dissecans, osteonecrosis, rheumatic disease, and trauma, may result in severe damage of articular cartilage and other joint structures, ranging from focal defects to osteoarthritis (OA). The osteochondral unit is one of the critical actors in this pathophysiological process. New approaches and applications in tissue engineering and regenerative medicine continue to drive the development of OA treatment. Hydrogel scaffolds, a component of tissue engineering, play an indispensable role in osteochondral regeneration. In this review, tissue engineering strategies regarding osteochondral regeneration were highlighted and summarized. The application of hydrogels for osteochondral regeneration within the last five years was evaluated with an emphasis on functionalized physical and chemical properties of hydrogel scaffolds, functionalized delivery hydrogel scaffolds as well as functionalized intelligent response hydrogel scaffolds. Lastly, to serve as guidance for future efforts in the creation of bioinspired hydrogel scaffolds, a succinct summary and new views for specific mechanisms, applications, and existing limitations of the newly designed functionalized hydrogel scaffolds were offered.

Prevention strategies of postoperative adhesion in soft tissues by applying biomaterials: Based on the mechanisms of occurrence and development of adhesions

Postoperative adhesion (POA) widely occurs in soft tissues and usually leads to chronic pain, dysfunction of adjacent organs and some acute complications, seriously reducing patients' quality of life and even being life-threatening. Except for adhesiolysis, there are few effective methods to release existing adhesion. However, it requires a second operation and inpatient care and usually triggers recurrent adhesion in a great incidence. Hence, preventing POA formation has been regarded as the most effective clinical strategy. Biomaterials have attracted great attention in preventing POA because they can act as both barriers and drug carriers. Nevertheless, even though much reported research has been demonstrated their efficacy on POA inhibition to a certain extent, thoroughly preventing POA formation is still challenging. Meanwhile, most biomaterials for POA prevention were designed based on limited experiences, not a solid theoretical basis, showing blindness. Hence, we aimed to provide guidance for designing anti-adhesion materials applied in different soft tissues based on the mechanisms of POA occurrence and development. We first classified the postoperative adhesions into four categories according to the different components of diverse adhesion tissues, and named them as "membranous adhesion", "vascular adhesion", "adhesive adhesion" and "scarred adhesion", respectively. Then, the process of the occurrence and development of POA were analyzed, and the main influencing factors in different stages were clarified. Further, we proposed seven strategies for POA prevention by using biomaterials according to these influencing factors. Meanwhile, the relevant practices were summarized according to the corresponding strategies and the future perspectives were analyzed.

Multifunctional Microgel-Based Cream Hydrogels for Postoperative Abdominal Adhesion Prevention

Postoperative abdominal adhesions are a common problem after surgery and can produce serious complications. Current antiadhesive strategies focus mostly on physical barriers and are unsatisfactory and inefficient. In this study, we designed and synthesized advanced injectable cream-like hydrogels with multiple functionalities, including rapid gelation, self-healing, antioxidation, anti-inflammation, and anti-cell adhesion. The multifunctional hydrogels were facilely formed by the conjugation reaction of epigallocatechin-3-gallate (EGCG) and hyaluronic acid (HA)-based microgels and poly(vinyl alcohol) (PVA) based on the dynamic boronic ester bond. The physicochemical properties of the hydrogels including antioxidative and anti-inflammatory activities were systematically characterized. A mouse cecum-abdominal wall adhesion model was implemented to investigate the efficacy of our microgel-based hydrogels in preventing postoperative abdominal adhesions. The hydrogels, with a high molecular weight HA, significantly decreased the inflammation, oxidative stress, and fibrosis and reduced the abdominal adhesion formation, compared to the commercial Seprafilm group or Injury-only group. Label-free quantitative proteomics analysis demonstrated that S100A8 and S100A9 expressions were associated with adhesion formation; the microgel-containing hydrogels inhibited these expressions. The microgel-containing hydrogels with multifunctionality decreased the formation of postoperative intra-abdominal adhesions in a murine model, demonstrating promise for clinical applications.

Endoscopic ultrasound-guided gallbladder endoscopic mucosal resection: a pilot porcine study

INTRODUCTION

Endoscopic ultrasound (EUS)-guided natural orifice transluminal gallbladder polypectomy provides a minimally invasive alternative to cholecystectomy. The study aimed to investigate the feasibility and safety of protocol for gallbladder endoscopic mucosal resection (gEMR) under EUS guidance using a porcine model.

MATERIAL AND METHODS

Fifteen Bama mini pigs were randomly divided into the control (CG, n = 3) and experimental (EG, n = 12) groups. EUS-guided fine needle aspiration was performed in the CG and used to establish a gallbladder pathway for polyp resection under EUS guidance in the EG. Procedural safety was evaluated using routine blood and biochemical tests, microbial bile cultures, histopathological tests, and enzyme-linked immunosorbent assays for inflammatory adhesion factors.

RESULTS

EUS-guided metal stents were successfully deployed in all 12 pigs. Two cases of stent displacement occurred postoperatively, and one pig died of infectious peritonitis on the first day after stent implantation. In 11 surviving experimental animals, mature gallbladder paths were formed at 7-14 days after gastro-cholecystostomy, through which gEMR of gallbladder polyps was successfully performed. There were no significant changes in levels of inflammatory and adhesion factors during the postoperative process.

CONCLUSIONS

EUS-gEMR may be a safe and effective minimally invasive treatment approach for gallbladder polyps.

Melanocortin therapies to resolve fibroblast-mediated diseases

Stromal cells have emerged as central drivers in multiple and diverse diseases, and consequently, as potential new cellular targets for the development of novel therapeutic strategies. In this review we revise the main roles of fibroblasts, not only as structural cells but also as players and regulators of immune responses. Important aspects like fibroblast heterogeneity, functional specialization and cellular plasticity are also discussed as well as the implications that these aspects may have in disease and in the design of novel therapeutics. An extensive revision of the actions of fibroblasts on different conditions uncovers the existence of numerous diseases in which this cell type plays a pathogenic role, either due to an exacerbation of their 'structural' side, or a dysregulation of their 'immune side'. In both cases, opportunities for the development of innovative therapeutic approaches exist. In this regard, here we revise the existing evidence pointing at the melanocortin pathway as a potential new strategy for the treatment and management of diseases mediated by aberrantly activated fibroblasts, including scleroderma or rheumatoid arthritis. This evidence derives from studies involving models of in vitro primary fibroblasts, in vivo models of disease as well as ongoing human clinical trials. Melanocortin drugs, which are pro-resolving mediators, have shown ability to reduce collagen deposition, activation of myofibroblasts, reduction of pro-inflammatory mediators and reduced scar formation. Here we also discuss existing challenges, both in approaching fibroblasts as therapeutic targets, and in the development of novel melanocortin drug candidates, that may help advance the field and deliver new medicines for the management of diseases with high medical needs.

An Injectable Hydrogel Scaffold Loaded with Dual-Drug/Sustained-Release PLGA Microspheres for the Regulation of Macrophage Polarization in the Treatment of Intervertebral Disc Degeneration

Due to the unique physical characteristics of intervertebral disc degeneration (IVDD) and the pathological microenvironment that it creates, including inflammation and oxidative stress, effective self-repair is impossible. During the process of intervertebral disc degeneration, there is an increase in the infiltration of M1 macrophages and the secretion of proinflammatory cytokines. Here, we designed a novel injectable composite hydrogel scaffold: an oligo [poly (ethylene glycol) fumarate]/sodium methacrylate (OPF/SMA) hydrogel scaffold loaded with dual-drug/sustained-release PLGA microspheres containing IL-4 (IL-4-PLGA) and kartogenin (KGN-PLGA). This scaffold exhibited good mechanical properties and low immunogenicity while also promoting the sustained release of drugs. By virtue of the PLGA microspheres loaded with IL-4 (IL-4-PLGA), the composite hydrogel scaffold induced macrophages to transition from the M1 phenotype into the M2 phenotype during the early induced phase and simultaneously exhibited a continuous anti-inflammatory effect through the PLGA microspheres loaded with kartogenin (KGN-PLGA). Furthermore, we investigated the mechanisms underlying the immunomodulatory and anti-inflammatory effects of the composite hydrogel scaffold. We found that the scaffold promoted cell proliferation and improved cell viability in vitro. While ensuring mechanical strength, this composite hydrogel scaffold regulated the local inflammatory microenvironment and continuously repaired tissue in the nucleus pulposus via the sequential release of drugs in vivo. When degenerative intervertebral discs in a rat model were injected with the scaffold, there was an increase in the proportion of M2 macrophages in the inflammatory environment and higher expression levels of type II collagen and aggrecan; this was accompanied by reduced levels of MMP13 expression, thus exhibiting long-term anti-inflammatory effects. Our research provides a new strategy for promoting intervertebral disc tissue regeneration and a range of other inflammatory diseases.

Mechanisms of Peritoneal Mesothelial Cells in Peritoneal Adhesion

A peritoneal adhesion (PA) is a fibrotic tissue connecting the abdominal or visceral organs to the peritoneum. The formation of PAs can induce a variety of clinical diseases. However, there is currently no effective strategy for the prevention and treatment of PAs. Damage to peritoneal mesothelial cells (PMCs) is believed to cause PAs by promoting inflammation, fibrin deposition, and fibrosis formation. In the early stages of PA formation, PMCs undergo mesothelial-mesenchymal transition and have the ability to produce an extracellular matrix. The PMCs may transdifferentiate into myofibroblasts and accelerate the formation of PAs. Therefore, the aim of this review was to understand the mechanism of action of PMCs in PAs, and to offer a theoretical foundation for the treatment and prevention of PAs.

Injectable adhesive self-healing biocompatible hydrogel for haemostasis, wound healing, and postoperative tissue adhesion prevention in nephron-sparing surgery

Nephron-sparing surgery is a well-established treatment in patients with T1a renal cell carcinoma; however, the complex suturing process prolongs warm ischaemia time, affects the preservation of normal renal parenchymal function, and causes avoidable postoperative tissue adhesion complications, including chronic abdominal pain, intestinal obstruction, and female infertility. Hence, the design of multifunctional biomaterials with haemostasis, postoperative wound management, and postoperative tissue adhesion prevention properties for nephron-sparing surgeries is urgently needed. In this study, a series of injectable adhesive multifunctional biocompatible hydrogels were designed based on the free-radical polymerisation of monomers acryloyl-6-aminocaproic acid (AA) and N-acryloyl 2-glycine (NAG), and the ionic coordination between Ca²⁺ and the abundant carboxyl groups in AA and NAG. AA/NAG/Ca (AA, NAG, and Ca refer to acryloyl-6-aminocaproic acid, N-acryloyl 2-glycine and calcium chloride, respectively) hydrogel exhibited good mechanical properties, swelling and adhesion properties, flexibility, in vitro blood-clotting ability, and cytocompatibility. In vivo experiments on liver injury models and rat/rabbit nephron-sparing surgery models elucidated that the AA/NAG/Ca hydrogel had haemostasis performance and wound healing properties that led to short bleeding time, reduced bleeding volume, and well-organised nephron structures. An abdomen-caecum adhesion model indicated that the AA/NAG/Ca hydrogel showed excellent anti-adhesion properties. In summary, this multifunctional hydrogel exhibited potential for improving haemostasis and wound management in nephron-sparing surgeries, showing potential for clinical application. STATEMENT OF SIGNIFICANCE: Extended warm ischemia time during nephron sparing surgery negatively affected postoperative renal function due to the need for hemostasis at the wound with abundant blood supply, and postoperative wound healing and additional adhesions caused by the surgical procedure deserve attention. Based on the efficient and stable adhesion properties of hydrogels and the ability to promote wound healing. Herein, a series of adhesive self-healing biocompatible hydrogels were prepared based on free-radical polymerization of acryloyl-6-aminocaproic acid (AA) and N-acryloyl 2-glycine (NAG) and the ionic coordination between Ca²⁺ with the abundant carboxyl groups in AA and NAG. AA/NAG/Ca hydrogel showed hemostasis property in nephron sparing surgery model, promote kidney wound healing, and could perform anti-postoperative adhesion efficacy in an abdomen-caecum adhesion model.

Schwann cell precursors represent a neural crest-like state with biased multipotency

Schwann cell precursors (SCPs) are nerve-associated progenitors that can generate myelinating and non-myelinating Schwann cells but also are multipotent like the neural crest cells from which they originate. SCPs are omnipresent along outgrowing peripheral nerves throughout the body of vertebrate embryos. By using single-cell transcriptomics to generate a gene expression atlas of the entire neural crest lineage, we show that early SCPs and late migratory crest cells have similar transcriptional profiles characterised by a multipotent "hub" state containing cells biased towards traditional neural crest fates. SCPs keep diverging from the neural crest after being primed towards terminal Schwann cells and other fates, with different subtypes residing in distinct anatomical locations. Functional experiments using CRISPR-Cas9 loss-of-function further show that knockout of the common "hub" gene Sox8 causes defects in neural crest-derived cells along peripheral nerves by facilitating differentiation of SCPs towards sympathoadrenal fates. Finally, specific tumour populations found in melanoma, neurofibroma and neuroblastoma map to different stages of SCP/Schwann cell development. Overall, SCPs resemble migrating neural crest cells that maintain multipotency and become transcriptionally primed towards distinct lineages.

AICAR attenuates postoperative abdominal adhesion formation by inhibiting oxidative stress and promoting mesothelial cell repair

Background

Postoperative abdominal adhesion is one of most common complications after abdominal operations. 5-aminoimidazole-4-carboxyamide ribonucleoside (AICAR) is an adenosine 5’-monophosphate activated protein kinase (AMPK) pathway agonist that inhibits inflammation, reduces cell fibrosis and cellular reactive oxygen species (ROS) injury, promotes autophagy and mitochondrial function. This study aimed to explore the mechanism of AICAR in inhibiting adhesion formation.

Materials and methods

Forty rats were randomly divided into five groups. All of the rats except the sham group received cecal abrasion to establish an adhesion model. The rats in the sodium hyaluronate group were treated with 2 mL sodium hyaluronate before closing the peritoneal cavity. The AICAR 1 and 2 groups were treated with 100 mg/kg and 200 mg/kg AICAR, respectively. Seven days after the operation, all of the rats were euthanized, and the adhesion condition was evaluated by Nair’s system. Inflammation was assessed by Eosin-hematoxylin (HE) staining and transforming growth factor-β (TGF-β1) detection. Oxidative stress effect was determined by ROS, nitric oxide (NO) level, superoxide dismutase (SOD), catalase, glutathione peroxidase (Gpx) and malondialdehyde (MDA) levels in adhesion tissue. Then, Sirius red picric acid staining was used to detect the fiber thickness. Immunohistochemical staining of cytokeratin-19 (CK-19), alpha-smooth muscle actin (α-SMA) and nuclear factor erythroid 2-related factor 2 (Nrf2) was also performed. Finally, HMrSV5 cells were treated with TGF-β1 and AICAR, the mRNA expression of E-cadherin, α-SMA and vimentin was assessed by q-PCR and cellular immunofluorescent staining.

Results

The rats in the AICAR-treated group had fewer adhesion formation incidences and a reduced Nair’s score. The inflammation was determined by HE staining and TGF-β1 concentration. The ROS, SOD, Catalase, Gpx, MDA levels and fiber thickness were decreased by AICAR treatments compared to the control. However, the NO production, Nrf2 levels and peritoneal mesothelial cell integrity were promoted after AICAR treatments. In vitro work, AICAR treatments reduced E-cadherin, α-SMA and vimentin mRNA level compared to that in the TGF-β1 group.

Conclusion

AICAR can inhibit postoperative adhesion formation by reducing inflammation, decreasing oxidative stress response and promoting peritoneal mesothelial cell repair.

In-situ growth of robust superlubricated nano-skin on electrospun nanofibers for post-operative adhesion prevention

It is a great challenge to achieve robustly bonded, fully covered, and nanoscaled coating on the surface of electrospun nanofibers. Herein, we develop a controllable, facile, and versatile strategy to in-situ grow superlubricated nano-skin (SLNS) on the single electrospun nanofiber. Specifically, zwitterionic polymer chains are generated from the nanofiber subsurface in an inside-out way, which consequently form a robust network interpenetrating with the polymeric chains of the nanofiber matrix. The nanofibers with SLNS are superlubricated with the coefficient of friction (COF) lower than 0.025, which is about 16-fold of reduction than the original nanofibers. The time-COF plot is very stable after 12, 000 cycles of friction test, and no abrasion is observed. Additionally, the developed nanofibrous membranes possess favorable tensile property and biocompatibility. Furthermore, the nanofibrous membranes with SLNS achieve prevention of post-operative adhesion, which is confirmed in both rat tendon adhesion model and abdominal adhesion model. Compared with clinically-used antiadhesive membranes such as Interceed and DK-film, our nanofibrous membranes are not only more effective but also have the advantage of lower production cost. Therefore, this study demonstrates a potential of the superlubricated nanofibrous membranes in-situ grown based on a SLNS strategy for achieving prevention of post-operative adhesion in clinics.

Regenerative Medicine Therapies for Prevention of Abdominal Adhesions: A Scoping Review

INTRODUCTION

Globally, abdominal adhesions constitute a significant burden of morbidity and mortality. They represent the commonest complication of abdominal operations with a lifelong risk of multiple pathologies, including adhesive small bowel obstruction, female infertility, and chronic pain. Adhesions represent a problem of the entire abdomen, forming at the time of injury and progressing through multiple complex pathways. Clinically available preventative strategies are limited to barrier technologies. Significant knowledge gaps persist in the characterization and mitigation of the involved molecular pathways underlying adhesion formation. Thus, the objectives of this scoping review are to describe the known molecular pathophysiology implicated in abdominal adhesion formation and summarize novel preclinical regenerative medicine preventative strategies for potential future clinical investigation.

METHODS

A literature review was performed in accordance with the Preferred Reporting Items for Systematic Reviews Extension for Scoping Reviews. Included peer-reviewed publications were published within the last 5 y and contained in vivo preclinical experimental studies of postoperative adhesions with the assessment of underlying mechanisms of adhesion formation and successful therapy for adhesion prevention. Studies not involving regenerative medicine strategies were excluded. Data were qualitatively synthesized.

RESULTS

A total of 1762 articles were identified. Of these, 1001 records were excluded by the described screening criteria. Sixty-eight full-text articles were evaluated for eligibility, and 11 studies were included for review.

CONCLUSIONS

Novel and reliable preventative strategies are urgently needed. Recent experimental data propose novel regenerative medicine targets for adhesion prevention.

Identification, discrimination and heterogeneity of fibroblasts

Fibroblasts, the principal cell type of connective tissue, secrete extracellular matrix components during tissue development, homeostasis, repair and disease. Despite this crucial role, the identification and distinction of fibroblasts from other cell types are challenging and laden with caveats. Rapid progress in single-cell transcriptomics now yields detailed molecular portraits of fibroblasts and other cell types in our bodies, which complement and enrich classical histological and immunological descriptions, improve cell class definitions and guide further studies on the functional heterogeneity of cell subtypes and states, origins and fates in physiological and pathological processes. In this review, we summarize and discuss recent advances in the understanding of fibroblast identification and heterogeneity and how they discriminate from other cell types.

In this review, the authors look at how recent progress in single-cell transcriptomics complement and enrich the classical, largely morphological, portraits of fibroblasts. The detailed molecular information now available provides new insights into fibroblast identity, heterogeneity and function.

Photo-Crosslinked Hyaluronic Acid/Carboxymethyl Cellulose Composite Hydrogel as a Dural Substitute to Prevent Post-Surgical Adhesion

A dural substitute is frequently used to repair dura mater during neurosurgical procedures. Although autologous or commercially available dural substitutes matched most of the requirements; difficulties during dural repair, including insufficient space for suturing, insufficient mechanical strength, easy tear and cerebrospinal fluid leakage, represent major challenges. To meet this need, a photo-crosslinked hydrogel was developed as a dural substitute/anti-adhesion barrier in this study, which can show sol-to-gel phase transition in situ upon short-time exposure to visible light. For this purpose, hyaluronic acid (HA) and carboxymethyl cellulose (CMC), materials used in abdominal surgery for anti-adhesion purposes, were reacted separately with glycidyl methacrylate to form hyaluronic acid methacrylate (HAMA) and carboxymethyl cellulose methacrylate (CMCMA). The HA/CMC (HC) hydrogels with different HA compositions could be prepared by photo-crosslinking HAMA and CMCMA with a 400 nm light source using lithium phenyl-2,4,6-trimethylbenzoylphosphinate as a photo-initiator. From studies of physico-chemical and biological properties of HC composite hydrogels, they are bio-compatible, bio-degradable and mechanically robust, to be suitable as a dural substitute. By drastically reducing attachment and penetration of adhesion-forming fibroblasts in vitro, the HC hydrogel can also act as an anti-adhesion barrier to prevent adhesion formation after dural repair. From in vivo study in rabbits, the HC hydrogel can repair dural defects as well as protect the dura from post-operative adhesion, endorsing the possible application of this hydrogel as a novel dural substitute.

Disrupting mechanotransduction decreases fibrosis and contracture in split-thickness skin grafting

Burns and other traumatic injuries represent a substantial biomedical burden. The current standard of care for deep injuries is autologous split-thickness skin grafting (STSG), which frequently results in contractures, abnormal pigmentation, and loss of biomechanical function. Currently, there are no effective therapies that can prevent fibrosis and contracture after STSG. Here, we have developed a clinically relevant porcine model of STSG and comprehensively characterized porcine cell populations involved in healing with single-cell resolution. We identified an up-regulation of proinflammatory and mechanotransduction signaling pathways in standard STSGs. Blocking mechanotransduction with a small-molecule focal adhesion kinase (FAK) inhibitor promoted healing, reduced contracture, mitigated scar formation, restored collagen architecture, and ultimately improved graft biomechanical properties. Acute mechanotransduction blockade up-regulated myeloid CXCL10-mediated anti-inflammation with decreased CXCL14-mediated myeloid and fibroblast recruitment. At later time points, mechanical signaling shifted fibroblasts toward profibrotic differentiation fates, and disruption of mechanotransduction modulated mesenchymal fibroblast differentiation states to block those responses, instead driving fibroblasts toward proregenerative, adipogenic states similar to unwounded skin. We then confirmed these two diverging fibroblast transcriptional trajectories in human skin, human scar, and a three-dimensional organotypic model of human skin. Together, pharmacological blockade of mechanotransduction markedly improved large animal healing after STSG by promoting both early, anti-inflammatory and late, regenerative transcriptional programs, resulting in healed tissue similar to unwounded skin. FAK inhibition could therefore supplement the current standard of care for traumatic and burn injuries.

Peritoneum-Inspired Janus Porous Hydrogel with Anti-Deformation, Anti-Adhesion, and Pro-Healing Characteristics for Abdominal Wall Defect Treatment

Implantable meshes used in tension-free repair operations facilitate treatment of internal soft-tissue defects. However, clinical meshes fail to achieve anti-deformation, anti-adhesion, and pro-healing properties simultaneously, leading to undesirable surgery outcomes. Herein, inspired by the peritoneum, a novel biocompatible Janus porous poly(vinyl alcohol) hydrogel (JPVA hydrogel) is developed to achieve efficient repair of internal soft-tissue defects by a facile yet efficient strategy based on top-down solvent exchange. The densely porous and smooth bottom-surface of JPVA hydrogel minimizes adhesion of fibroblasts and does not trigger any visceral adhesion, and its loose extracellular-matrix-like porous and rough top-surface can significantly improve fibroblast adhesion and tissue growth, leading to superior abdominal wall defect treatment to commercially available PP and PCO meshes. With unique anti-swelling property (maximum swelling ratio: 6.4%), JPVA hydrogel has long-lasting anti-deformation performance and maintains high mechanical strength after immersion in phosphate-buffered saline (PBS) for 14 days, enabling tolerance to the maximum abdominal pressure in an internal wet environment. By integrating visceral anti-adhesion and defect pro-healing with anti-deformation, the JPVA hydrogel patch shows great prospects for efficient internal soft-tissue defect repair.

Harnessing a Feasible and Versatile ex vivo Calvarial Suture 2-D Culture System to Study Suture Biology

As a basic science, craniofacial research embraces multiple facets spanning from molecular regulation of craniofacial development, cell biology/signaling and ultimately translational craniofacial biology. Calvarial sutures coordinate development of the skull, and the premature fusion of one or more, leads to craniosynostosis. Animal models provide significant contributions toward craniofacial biology and clinical/surgical treatments of patients with craniofacial disorders. Studies employing mouse models are costly and time consuming for housing/breeding. Herein, we present the establishment of a calvarial suture explant 2-D culture method that has been proven to be a reliable system showing fidelity with the in vivo harvesting procedure to isolate high yields of skeletal stem/progenitor cells from small number of mice. Moreover, this method allows the opportunity to phenocopying models of craniosynostosis and in vitro tamoxifen-induction of ActincreERT2;R26Rainbow suture explants to trace clonal expansion. This versatile method tackles needs of large number of mice to perform calvarial suture research.

PNP Hydrogel Prevents Formation of Symblephara in Mice After Ocular Alkali Injury

PURPOSE

To create an alkali injury symblephara mouse model to study conjunctival fibrosis pathophysiology and test polymer nanoparticle (PNP) hydrogel as a preventative therapeutic.

METHODS

Mice were injured using NaOH-soaked filter paper to determine the optimal NaOH concentration to induce the formation of symblephara. Injured mice were observed for 7 days to detect the formation of symblephara. Forniceal shortening observed on hematoxylin and eosin (H&E)-stained tissue sections was used as a symblephara marker. Alpha-smooth muscle actin (α-SMA) expression, Masson's trichrome assay, and periodic acid-Schiff (PAS) staining were used to determine myofibroblast expression, collagen deposition, and goblet cell integrity. PNP hydrogel, with multivalent, noncovalent interactions between modified biopolymers and nanoparticles, was applied immediately after alkali injury to determine its ability to prevent the formation of symblephara.

RESULTS

Forniceal shortening was observed in H&E images with 1N NaOH for 2 minutes after 7 days without globe destruction. PNP hydrogel prevented forniceal shortening after alkali injury as observed by H&E histology. α-SMA expression and collagen deposition in eye tissue sections were increased in the fornix after injury with 1N NaOH compared with uninjured controls. PNP hydrogel treatment immediately after injury reduced α-SMA expression and collagen deposition in the forniceal region. Mucin-secreting goblet cells stained with PAS were significantly lower in alkali-injured and PNP hydrogel-treated conjunctivas than in uninjured control conjunctivas.

CONCLUSIONS

We observed that 1N NaOH for 2 minutes induced maximal forniceal shortening and symblephara in mice. PNP hydrogel prevented forniceal shortening and conjunctival fibrosis after injury. This first murine model for symblephara will be useful to study fibrosis pathophysiology after conjunctival injury and to determine therapeutic targets for cicatrizing diseases.

TRANSLATIONAL RELEVANCE

This mouse model of symblephara can be useful for studying conjunctival scarring disease pathophysiology and preventative therapeutics. We tested PNP hydrogel, which prevented the formation of symblephara after injury.

A functional PVA aerogel-based membrane obtaining sutureability through modified electrospinning technology and achieving promising anti-adhesion effect after cardiac surgery

Pericardial barrier destruction, inflammatory cell infiltration, and fibrous tissue hyperplasia, trigger adhesions after cardiac surgery. There are few anti-adhesion materials that are both functional and sutureable for pericardial reconstruction. Besides, a few studies have reported on the mechanism of preventing pericardial adhesion. Herein, a functional barrier membrane with sutureability was developed via a modified electrospinning method. It was composed of poly(l-lactide-co-caprolactone) (PLCL) nanofibers, poly(vinyl alcohol) (PVA) aerogel, and melatonin, named PPMT. The PPMT had a special microstructure manifested as a staggered arrangement of nanofibers on the surface and a layered macroporous aerogel structure in a cross-section. Besides providing the porosity and hydrophilicity obtained from PVA, the structure also had suitable mechanical properties for stitching due to the addition of PLCL nanofibers. Furthermore, it inhibited the proliferation of fibroblasts by suppressing the activation of Fas and P53, and achieved anti-inflammatory effects by affecting the activity of inflammatory cells and reducing the release of pro-inflammatory factors, such as interleukin 8 (IL-8) and tumor necrosis factor α (TNF-α). Finally, in vivo transplantation showed that it up-regulated the expression of matrix metalloproteinase-1 (MMP1) and tissue inhibitor of metalloproteinase-1 (TIMP1), and down-regulated the expression of Vinculin and transforming growth factor β (TGF-β) in the myocardium, thereby reducing the formation of adhesions. Collectively, these results demonstrate a great potential of PPMT membrane for practical application to anti-adhesion.

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A functional PVA aerogel-based membrane (PPMT) obtained sutureability through modified electrospinning technology.

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The primary mechanism to anti-adhesion of PPMT membrane was explored.

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Promising anti-adhesion effect of PPMT membrane was accomplished in pericardium reconstruction in rabbit.

JUN promotes hypertrophic skin scarring via CD36 in preclinical in vitro and in vivo models

[Figure: see text].

Disrupting biological sensors of force promotes tissue regeneration in large organisms

Tissue repair and healing remain among the most complicated processes that occur during postnatal life. Humans and other large organisms heal by forming fibrotic scar tissue with diminished function, while smaller organisms respond with scarless tissue regeneration and functional restoration. Well-established scaling principles reveal that organism size exponentially correlates with peak tissue forces during movement, and evolutionary responses have compensated by strengthening organ-level mechanical properties. How these adaptations may affect tissue injury has not been previously examined in large animals and humans. Here, we show that blocking mechanotransduction signaling through the focal adhesion kinase pathway in large animals significantly accelerates wound healing and enhances regeneration of skin with secondary structures such as hair follicles. In human cells, we demonstrate that mechanical forces shift fibroblasts toward pro-fibrotic phenotypes driven by ERK-YAP activation, leading to myofibroblast differentiation and excessive collagen production. Disruption of mechanical signaling specifically abrogates these responses and instead promotes regenerative fibroblast clusters characterized by AKT-EGR1.

Humans and other large mammals heal wounds by forming fibrotic scar tissue with diminished function. Here, the authors show that disrupting mechanotransduction through the focal adhesion kinase pathway in large animals accelerates healing, prevents fibrosis, and enhances skin regeneration.

Aged skeletal stem cells generate an inflammatory degenerative niche

Loss of skeletal integrity during ageing and disease is associated with an imbalance in the opposing actions of osteoblasts and osteoclasts1. Here we show that intrinsic ageing of skeletal stem cells (SSCs)2 in mice alters signalling in the bone marrow niche and skews the differentiation of bone and blood lineages, leading to fragile bones that regenerate poorly. Functionally, aged SSCs have a decreased bone- and cartilage-forming potential but produce more stromal lineages that express high levels of pro-inflammatory and pro-resorptive cytokines. Single-cell RNA-sequencing studies link the functional loss to a diminished transcriptomic diversity of SSCs in aged mice, which thereby contributes to the transformation of the bone marrow niche. Exposure to a youthful circulation through heterochronic parabiosis or systemic reconstitution with young haematopoietic stem cells did not reverse the diminished osteochondrogenic activity of aged SSCs, or improve bone mass or skeletal healing parameters in aged mice. Conversely, the aged SSC lineage promoted osteoclastic activity and myeloid skewing by haematopoietic stem and progenitor cells, suggesting that the ageing of SSCs is a driver of haematopoietic ageing. Deficient bone regeneration in aged mice could only be returned to youthful levels by applying a combinatorial treatment of BMP2 and a CSF1 antagonist locally to fractures, which reactivated aged SSCs and simultaneously ablated the inflammatory, pro-osteoclastic milieu. Our findings provide mechanistic insights into the complex, multifactorial mechanisms that underlie skeletal ageing and offer prospects for rejuvenating the aged skeletal system.