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.

Single-cell transcriptomic atlas of different endometriosis indicating that an interaction between endometriosis-associated mesothelial cells (EAMCs) and ectopic stromal cells may influence progesterone resistance

BACKGROUND

Endometriosis is a hormone-dependent disease, which can usually be divided into peritoneal endometriosis (PEM), deep-infiltrating endometriosis (DIE) and ovarian endometriosis (OEM). Although the three pathologic types are essentially the same disease, they differ in pathological manifestations, molecular features, pain symptoms and hormonal responsiveness. However, there is limited literature focusing on the differences among these types. In this study, we employed single-cell RNA sequencing (scRNA-seq) to profile the transcriptome of each type using surgical biopsy samples obtained from six patients. We aimed to explore and elucidate the variations among these different types of endometriosis.

RESULTS

We identified five major cell types and 44 subpopulations, including the presence of mesothelial cells in all pathological types, including OEM. Furthermore, we characterised the variations in cell types across different pathological types by employing enrichment analysis to assess functions and pathways. Notably, our findings reveal distinct levels of epithelial-mesenchymal transition (EMT) processes experienced by mesothelial cells within the microenvironment of endometriotic lesions. Through ligand-receptor analysis and referencing relevant literature, we propose that mesothelial cells exert an influence on progesterone resistance in stromal cells through intercellular communication mediated by the FN1-AKT pathway.

CONCLUSIONS

Our study comprehensively characterises the heterogeneity of the different pathologic types of endometriosis and offers valuable insights into the underlying mechanisms contributing to variations in progesterone resistance across the three subtypes.

KEY POINTS

Single-cell RNA (ScRNA) atlas across types of endometriosis is established. Mesothelial cells are founded in ovarian endometriosis. Endometriosis-associated mesothelial cells (EAMCs) experience various level of epithelial-mesenchymal transition (EMT) process in different subtypes. EAMCs may exert an influence on progesterone resistance in stromal cells through intercellular communication mediated by the FN1-AKT pathway.

CD45+/ Col I+ Fibrocytes: Major Source of Collagen in the Fibrotic Lung, but not in Passaged Fibroblast Cultures

The role of cells of the hematopoietic lineage in fibrosis is controversial. Here we evaluate the contribution of Col I+/CD45+ cells (fibrocytes) to lung fibrosis. Systemic bleomycin treatment was used to induce fibrosis in a bone marrow transplant and two transgenic mouse models. Lung cells from these mice were analyzed by flow cytometry, both immediately upon release from the tissue or following growth on tissue-culture plastic. Fibrotic and control human lung tissue were also used. Fibroblasts and fibrocytes derived from a transgenic mouse model were compared in terms of their morphology, growth, and adhesion to fibronectin. Single cell RNAseq was performed with the analysis focusing on CD45-/Col I+ "fibroblasts" and CD45+/Col I+ "fibrocytes" in control and fibrotic mouse lung tissue. Finally, we inhibited fibrosis in mice using a novel, water-soluble version of caveolin scaffolding domain (CSD) called WCSD. In both mouse and human lung tissue, we observed by flow cytometry a large increase in fibrocyte number and Col I expression associated with fibrosis. In contrast, fibroblast number was not significantly increased. A large increase (>50-fold) in fibrocyte number associated with fibrosis was also observed by single cell RNAseq. In this case, fibroblasts increased 5-fold. Single cell RNAseq also revealed that myofibroblast markers in fibrotic tissue are associated with a cluster containing a similar number of fibrocytes and fibroblasts, not with a resident fibroblast cluster. Some investigators claim that fibrocytes are not present among primary fibroblasts. However, we found that fibrocytes were the predominant cell type present in these cultures prior to passage. Fewer fibrocytes were present after one passage, and almost none after two passages. Our experiments suggest that fibrocytes are crowded out of cultures during passage because fibroblasts have a larger footprint than fibrocytes, even though fibrocytes bind more efficiently to fibronectin. Finally, we observed by flow cytometry that in mice treated with bleomycin and WCSD compared to bleomycin alone, there was a large decrease in the number of fibrocytes present but not in the number of fibroblasts. In summary, fibrocytes are a major collagen-producing cell type that is increased in number in association with fibrosis as well as a major source of myofibroblasts. The common observation that collagen-producing spindle-shaped cells associated with fibrosis are CD45- may be an artifact of passage in cell culture.

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.

Ligustrazine nanoparticles inhibits epithelial-mesenchymal transition and alleviates postoperative abdominal adhesion

Following abdominal surgery, the occurrence of postoperative abdominal adhesion (PAA) is highly prevalent and stands out as one of the most frequently encountered complications. The effect and molecular mechanisms of Ligustrazine nanoparticles (LN) underlying epithelial-mesenchymal transition (EMT) in PAA still remain elusive. Adhesions were induced in Male Sprague-Dawley rats by injuring the cecum (cecal abrasion model), followed by administration of LN and hyaluronate acid (HA). The mechanism was further verified by enzyme-linked immunosorbent assay, wound healing assay, si-RNA and Western blot. Animal experiments revealed that LN effectively ameliorated adhesions, notably decreased tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-8, and fibrosis, and reduced the expression of TGF-β1 and EMT related markers (Fibronectin and E-cadherin). Furthermore, in vitro experiments demonstrated that LN might inhibit the TGF-β1 FOXC2 pathway through suppressing the expression of Fibronectin, P120, and E-cadherin and ameliorating peritoneal adhesion. Collectively, our findings indicate that LN inhibits PAA formation by reducing inflammation, decreasing EMT and promoting peritoneal mesothelial cell repair. Therefore, LN might be considered a potential candidate for the treatment of PPA. However, further clinical studies are required to approve the effectiveness of LN.

Hepatocyte Growth Factor DNA Aptamer for Prevention of Postoperative Peritoneal Adhesion via Enhancement of Fibrinolysis and Inhibition of Mesothelial Mesenchymal Transition

Postoperative peritoneal adhesion (PPA) is a prevalent complication of abdominal surgery, posing a significant hindrance to postsurgical recovery. Although several strategies have been developed to alleviate and prevent adhesions, their efficacy remains unsatisfactory. For the first time, we studied the therapeutic effect and mechanism of our recently developed thermally stable oligonucleotide-based mimetics of hepatocyte growth factor (HGF DNA aptamer) to prevent PPA. The HGF DNA aptamer effectively inhibited canonical TGF-β1 signaling transduction, partially suppressing mesothelial mesenchymal transition. Additionally, the aptamer, respectively, upregulated and downregulated the expression of tissue plasminogen activator and plasminogen activator inhibitor 1, thereby enhancing fibrinolytic activity. As a pleiotropic factor, the HGF DNA aptamer also enhanced the migratory and proliferative capacities of mesothelial cells. Finally, the aptamer demonstrated a higher level of effectiveness in preventing PPAs than the commercially available antiperitoneal adhesion barrier, Seprafilm. Due to its therapeutic benefits, excellent stability, biosafety, cost-effectiveness, and versatility, the HGF DNA aptamer demonstrates promise for preventing PPA in future clinical settings.

Neutrophil Extracellular Traps: A Crucial Factor in Post-Surgical Abdominal Adhesion Formation

Post-surgical abdominal adhesions, although poorly understood, are highly prevalent. The molecular processes underlying their formation remain elusive. This review aims to assess the relationship between neutrophil extracellular traps (NETs) and the generation of postoperative peritoneal adhesions and to discuss methods for mitigating peritoneal adhesions. A keyword or medical subject heading (MeSH) search for all original articles and reviews was performed in PubMed and Google Scholar. It included studies assessing peritoneal adhesion reformation after abdominal surgery from 2003 to 2023. After assessing for eligibility, the selected articles were evaluated using the Critical Appraisal Skills Programme checklist for qualitative research. The search yielded 127 full-text articles for assessment of eligibility, of which 7 studies met our criteria and were subjected to a detailed quality review using the Critical Appraisal Skills Programme (CASP) checklist. The selected studies offer a comprehensive analysis of adhesion pathogenesis with a special focus on the role of neutrophil extracellular traps (NETs) in the development of peritoneal adhesions. Current interventional strategies are examined, including the use of mechanical barriers, advances in regenerative medicine, and targeted molecular therapies. In particular, this review emphasizes the potential of NET-targeted interventions as promising strategies to mitigate postoperative adhesion development. Evidence suggests that in addition to their role in innate defense against infections and autoimmune diseases, NETs also play a crucial role in the formation of peritoneal adhesions after surgery. Therefore, therapeutic strategies that target NETs are emerging as significant considerations for researchers. Continued research is vital to fully elucidate the relationship between NETs and post-surgical adhesion formation to develop effective treatments.

Effect of cellular senescence on the response of human peritoneal mesothelial cells to TGF-β

Transforming growth factor β (TGF-β) is implicated in both mesothelial-to-mesenchymal transition (MMT) and cellular senescence of human peritoneal mesothelial cells (HPMCs). We previously showed that senescent HPMCs could spontaneously acquire some phenotypic features of MMT, which in young HPMCs were induced by TGF-β. Here, we used electron microscopy, as well as global gene and protein profiling to assess in detail how exposure to TGF-β impacts on young and senescent HPMCs in vitro. We found that TGF-β induced structural changes consistent with MMT in young, but not in senescent HPMCs. Of all genes and proteins identified reliably in HPMCs across all treatments and states, 4,656 targets represented overlapping genes and proteins. Following exposure to TGF-β, 137 proteins and 46 transcripts were significantly changed in young cells, compared to 225 proteins and only 2 transcripts in senescent cells. Identified differences between young and senescent HPMCs were related predominantly to wound healing, integrin-mediated signalling, production of proteases and extracellular matrix components, and cytoskeleton structure. Thus, the response of senescent HPMCs to TGF-β differs or is less pronounced compared to young cells. As a result, the character and magnitude of the postulated contribution of HPMCs to TGF-β-induced peritoneal remodelling may change with cell senescence.

Research landscape of abdominal adhesions from 2004 to 2023: A bibliometric analysis

Adhesions are the most common complication of abdominal or pelvic surgery and remain a challenging problem. To better understand the development tendency of abdominal adhesions, we performed a comprehensive bibliometric analysis of the field of abdominal adhesions. In total, 2219 articles regarding abdominal adhesions were screened and analyzed from 3410 manuscripts indexed in the Web of Science-indexed manuscripts regarding abdominal adhesion from 2004 to 2023. A bibliometric analysis was performed, and CiteSpace [version 6.2. R3 (64-bit)] and VOSviewer (version 1.6.19) were used to visualize the results. The number of annual publications showed slight growth before 2019, and the USA contributed the most publications. The most prolific author in this domain was Diamond, while the publications from Ten Broek had the strongest influence. The most popular journal in this field was the Journal of Surgical Research, and the most frequently co-cited journal was Fertility and Sterility. After analyzing the keywords, "prevention", "surgery" and "peritoneal adhesion" were the 3 most co-cited keywords, while "adhesive small bowel obstruction" was the strongest keyword in the citation burst. Here, for the first time, we used bibliometric methods to study abdominal adhesions over the past ten years. By summarizing the characteristics of publications and predicting future research prospects, we established a framework for researchers and provided a basis for subsequent research.

Hemoadhican-Based Bioabsorbable Hydrogel for Preventing Postoperative Adhesions

Postoperative peritoneal adhesions are a prevalent clinical issue following abdominal and pelvic surgery, frequently resulting in heightened personal and societal health burdens. Traditional biomedical barriers offer limited benefits because of practical challenges for doctors and their incompatibility with laparoscopic surgery. Hydrogel materials, represented by hyaluronic acid gels, are receiving increasing attention. However, existing antiadhesive gels still have limited effectiveness or carry the risk of complications in clinical applications. Herein, we developed a novel hydrogel using polysaccharide hemoadhican (HD) as the base material and polyethylene glycol diglycidyl ether (PEGDE) as the cross-linking agent. The HD hydrogels exhibit appropriate mechanical properties, injectability, and excellent cytocompatibility. We demonstrate resistance to protein adsorption and L929 fibroblast cell adhesion to the HD hydrogel. The biodegradability and efficacy against peritoneal adhesion are further evaluated in C57BL/6 mice. Our results suggest a potential strategy for anti-postoperative tissue adhesion barrier biomaterials.

Advanced postoperative tissue antiadhesive membranes enabled with electrospun nanofibers

Tissue adhesion is one of the most common postoperative complications, which is frequently accompanied by inflammation, pain, and even dyskinesia, significantly reducing the quality of life of patients. Thus, to prevent the formation of tissue adhesions, various strategies have been explored. Among these methods, placing anti-adhesion membranes over the injured site to separate the wound from surrounding tissues is a simple and prominently favored method. Recently, electrospun nanofibers have been the most frequently investigated antiadhesive membranes due to their tunable porous structure and high porosities. They not only can act as an essential barrier and functional carrier system but also allow for high permeability and nutrient transport, showing great potential for preventing tissue adhesion. Herein, we provide a short review of the most recent applications of electrospun nanofibrous antiadhesive membranes in tendons, the abdominal cavity, dural sac, pericardium, and meninges. Firstly, each section highlights the most representative examples and they are sorted based on the latest progress of related research. Moreover, the design principles, preparation strategies, overall performances, and existing problems are highlighted and evaluated. Finally, the current challenges and several future ways to develop electrospun nanofibrous antiadhesive membranes are proposed. The systematic discussion and proposed directions can shed light on ideas and guide the reasonable design of electrospun nanofibrous membranes, contributing to the development of exceptional tissue anti-adhesive materials in the foreseeable future.

Luteolin blocks the ROS/PI3K/AKT pathway to inhibit mesothelial-mesenchymal transition and reduce abdominal adhesions

BACKGROUND

Postoperative abdominal adhesion (PAA) is a common postoperative complication. Clinically, various methods have been used to prevent the occurrence of PAA, such as drugs and physiotherapy; however, no satisfactory results have been obtained. Luteolin (LUT) is a natural flavonoid that reduces inflammation and acts as an antioxidant. This research aimed to examine the impact and mechanism of LUT in reducing PAA.

METHODS

C57/BL6 mice were used in vivo experiments. PAA model was established using a brush friction method. Visual scoring and hematoxylin and eosin staining were used to score the severity of adhesions. Network pharmacology was used to infer potential targets and core pathways of LUT. Hydrogen peroxide (H2O2) was used to induce oxidative stress in vitro, while the reactive oxygen species (ROS) assay kit was used to evaluate oxidative stress levels. Western blotting, cell immunofluorescence, and multiple immunofluorescence assays were used to detect α-SMA, vimentin, E-cadherin, collagen I, or AKT phosphorylation level. Scratch assay was used to detect cell migration.

RESULTS

LUT reduced the degree of PAA in mice. It attenuated H2O2-induced ROS production and reversed mesothelial-mesenchymal transition (MMT) in HMrSV5 cells. Network pharmacology analysis showed that LUT likely exerted anti-adhesion activity by regulating the PI3K-Akt signaling pathway. Phosphorylated Akt levels were significantly reduced in LUT-treated HMrSV5 cells. LUT also significantly reduced the expression of vimentin and collagen I in adherent tissues and upregulated E-cadherin expression.

CONCLUSION

LUT blocks the ROS/PI3K/AKT pathway, thereby inhibiting MMT and reducing PAA. To this end, LUT has potential in PAA therapy.

Can we predict peritoneal adhesions formation after cesarean delivery?

OBJECTIVE

To examine demographic and obstetrical factors that are associated with adhesion formation following cesarean delivery.

METHODS

We conducted a population-based study that included all women over 18 years og age who underwent two cesarean deliveries between the years 1988 and 2016 in a large tertiary medical center. We excluded women with adhesions already diagnosed during the first cesarean delivery, history of other abdominal or pelvic surgery, history of pelvic infection or pelvic inflammatory disease, history of endometriosis and history of uterine Müllerian anomalies. In addition, women with a classical or T-shaped uterine incision, non-singleton pregnancies, and fetal chromosomal or structural abnormalities were excluded.

RESULTS

During the study period, 32.6% (n = 2283) of women were diagnosed with peritoneal adhesions during the second cesarean delivery. Factors found to be significantly associated with peritoneal adhesions were maternal age 35 years or older at the first cesarean delivery, Bedouin Arab ethnicity, composite of intrapartum and postpartum infectious morbidity, and cesarean deliveries that were performed after the onset of labor. In contrast, having a previous vaginal birth was found to be protective.

CONCLUSIONS

Our results suggest that a woman's characteristics at her first cesarean delivery and her obstetrical history may be predictive of the likelihood of adhesion formation.

The impact of a previous cesarean section on the risk of perioperative and postoperative complications during vaginal hysterectomy

OBJECTIVE

To investigate whether a previous cesarean section increases the risk of perioperative and postoperative complications during vaginal hysterectomy.

METHODS

A retrospective cohort study of women who had undergone a vaginal hysterectomy for benign indications between 2014 and 2019 was conducted, comparing patients with or without a previous cesarean section. Perioperative and postoperative complications during vaginal hysterectomy were assessed according to the Clavien-Dindo classification system within 30 days of surgery. Duration of surgery, estimated blood loss, and postoperative hospitalization days were also recorded. A two-sided P value of less than 0.05 was considered significant.

RESULTS

A total of 185 women were included, 25 (13.5%) patients had undergone a previous cesarean section (study group) and 160 (86.5%) had no history of cesarean section (comparison group). We found no significant differences in demographic and clinical characteristics as well as postoperative complications and interventions, duration of surgery, estimated blood loss, and postoperative hospitalization days (P > 0.05). However, patients who underwent two or more cesarean sections had a significantly (P = 0.01) higher rate and grade of complications during vaginal hysterectomy, compared with women with only one previous cesarean section. All women who underwent two or more cesarean sections had mild complications during vaginal hysterectomy (40% grade I and 60% grade II, P = 0.01).

CONCLUSION

Vaginal hysterectomy is a safe procedure with few severe complications, regardless of a previous cesarean section. More than one previous cesarean section may increase the risk of minor complications during a vaginal hysterectomy. Patients who underwent a previous cesarean section could be reassured that they do not face an increased risk of complications during a vaginal hysterectomy.

Quercetin inhibits mesothelial-mesenchymal transition and alleviates postoperative peritoneal adhesions by blocking the TGF-β1/PI3K/AKT pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Carthami flos is a dried flower of the Asteraceae plant Carthamus tinctorius (L.). Danhong injection, composed of Carthami flos and Danshen can prevent the formation of postoperative peritoneal adhesions. Quercetin (QUE), an active compound of Carthami flos, has also been proved to prevent postoperative abdominal and uterine cavity adhesions. However, whether QUE is the key component in Carthami flos and the mechanism in preventing postoperative peritoneal adhesions has not been studied.

AIM OF THE STUDY

To predict whether QUE is the key molecule in Carthami flos and explore the effect and mechanism of QUE in preventing postoperative peritoneal adhesions.

MATERIALS AND METHODS

Drug composition and target analysis was used to predict the key component in Carthami flos. The method of cecum-sidewall abrasion was used to establish adhesion models, and the antiadhesion effect of QUE was evaluated with the adhesion scoring system. Network pharmacology was used to predict the targets and potential mechanism of QUE in preventing adhesion. The mechanism was further verified by immunofluorescence, Western blot, wound healing experiment, and molecular docking.

RESULTS

Quercetin was predicted to be the key to preventing postoperative peritoneal adhesions in Carthami flos. Animal experiments revealed that QUE effectively ameliorated adhesions and reduced the expression of mesothelial-mesenchymal transition (MMT) related markers and TGF-β1. Moreover, the TGF-β1/PI3K/AKT pathway was predicted via protein-protein interaction and Kyoto encyclopedia of Genes and Genomes enrichment analysis to play a crucial part in preventing adhesion by QUE. Furthermore, in vitro experiments and molecular docking demonstrated that QUE could block the TGF-β1/PI3K/AKT pathway through forming a stable combination with TβR-II, thereby inhibiting MMT and ameliorating peritoneal adhesion.

CONCLUSIONS

QUE can not only reduce postoperative TGF-β1 but also block the TGF-β1/PI3K/AKT pathway to inhibit MMT of mesothelial cells, and finally alleviate postoperative peritoneal adhesions. These findings may provide insights towards development of a safe and effective anti-adhesive drug for prevention of postoperative peritoneal adhesions.

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.

Techniques for navigating postsurgical adhesions: Insights into mechanisms and future directions

Postsurgical adhesions are a common complication of surgical procedures that can lead to postoperative pain, bowel obstruction, infertility, as well as complications with future procedures. Several agents have been developed to prevent adhesion formation, such as barriers, anti-inflammatory and fibrinolytic agents. The Food and Drug Administration (FDA) has approved the use of physical barrier agents, but they have been associated with conflicting clinical studies and controversy in the clinical utilization of anti-adhesion barriers. In this review, we summarize the human anatomy of the peritoneum, the pathophysiology of adhesion formation, the current prevention agents, as well as the current research progress on adhesion prevention. The early cellular events starting with injured mesothelial cells and incorporating macrophage response have recently been found to be associated with adhesion formation. This may provide the key component for developing future adhesion prevention methods. The current use of physical barriers to separate tissues, such as Seprafilm®, composed of hyaluronic acid and carboxymethylcellulose, can only reduce the risk of adhesion formation at the end stage. Other anti-inflammatory or fibrinolytic agents for preventing adhesions have only been studied within the context of current research models, which is limited by the lack of in-vitro model systems as well as in-depth study of in-vivo models to evaluate the efficiency of anti-adhesion agents. In addition, we explore emerging therapies, such as gene therapy and stem cell-based approaches, that may offer new strategies for preventing adhesion formation. In conclusion, anti-adhesion agents represent a promising approach for reducing the burden of adhesion-related complications in surgical patients. Further research is needed to optimize their use and develop new therapies for this challenging clinical problem.

Multifunctional Oxidized Dextran-Metformin as a Tissue-Adhesive Hydrogel to Prevent Postoperative Peritoneal Adhesions in Patients with Metabolic Syndrome

Patients with metabolic syndrome (MetS) undergoing surgery are at high risk of developing peritoneal adhesions and other severe postoperative complications. However, the single shielding function and absence of physiological activity render conventional methods less useful in preventing adhesions in patients with MetS. To address this challenge, a convenient method is introduced for developing a novel tissue-adhesive hydrogel called oxidized dextran-metformin (ODE-ME) via Schiff base linkages. This injectable ODE-ME hydrogel exhibits excellent tissue-adhesive properties and various physiological functions, particularly enhanced antibacterial effects. Furthermore, in vivo experiments demonstrate that the hydrogel can effectively alleviate hyperglycemia, reduce excessive inflammation, and improve fibrinolytic activity in MetS mice, thereby preventing adhesions and promoting incisional healing. The hydrogel concurrently isolates injured tissues and lowers the blood glucose levels immediately after surgery in mice. Therefore, the ODE-ME hydrogel functions as a multifunctional barrier material and has potential for preventing postoperative peritoneal adhesions in patients with MetS in clinical settings.

Advances in stem cell therapy for peritoneal fibrosis: from mechanisms to therapeutics

Peritoneal fibrosis (PF) is a pathophysiological condition caused by a variety of pathogenic factors. The most important features of PF are mesothelial-mesenchymal transition and accumulation of activated (myo-)fibroblasts, which hinder effective treatment; thus, it is critical to identify other practical approaches. Recently, stem cell (SC) therapy has been indicated to be a potential strategy for this disease. Increasing evidence suggests that many kinds of SCs alleviate PF mainly by differentiating into mesothelial cells; secreting cytokines and extracellular vesicles; or modulating immune cells, particularly macrophages. However, there are relatively few articles summarizing research in this direction. In this review, we summarize the risk factors for PF and discuss the therapeutic roles of SCs from different sources. In addition, we outline effective approaches and potential mechanisms of SC therapy for PF. We hope that our review of articles in this area will provide further inspiration for research on the use of SCs in PF treatment.

Targeting carcinoma-associated mesothelial cells with antibody-drug conjugates in ovarian carcinomatosis

Ovarian carcinomatosis is characterized by the accumulation of carcinoma-associated mesothelial cells (CAMs) in the peritoneal stroma and mainly originates through a mesothelial-to-mesenchymal transition (MMT) process. MMT has been proposed as a therapeutic target for peritoneal metastasis. Most ovarian cancer (OC) patients present at diagnosis with peritoneal seeding, which makes tumor progression control difficult by MMT modulation. An alternative approach is to use antibody-drug conjugates (ADCs) targeted directly to attack CAMs. This strategy could represent the cornerstone of precision-based medicine for peritoneal carcinomatosis. Here, we performed complete transcriptome analyses of ascitic fluid-isolated CAMs in advanced OC patients with primary-, high-, and low-grade, serous subtypes and following neoadjuvant chemotherapy. Our findings suggest that both cancer biological aggressiveness and chemotherapy-induced tumor mass reduction reflect the MMT-associated changes that take place in the tumor surrounding microenvironment. Accordingly, MMT-related genes, including fibroblast activation protein (FAP), mannose receptor C type 2 (MRC2), interleukin-11 receptor alpha (IL11RA), myristoylated alanine-rich C-kinase substrate (MARCKS), and sulfatase-1 (SULF1), were identified as specific actionable targets in CAMs of OC patients, which is a crucial step in the de novo design of ADCs. These cell surface target receptors were also validated in peritoneal CAMs of colorectal cancer peritoneal implants, indicating that ADC-based treatment could extend to other abdominal tumors that show peritoneal colonization. As proof of concept, a FAP-targeted ADC reduced tumor growth in an OC xenograft mouse model with peritoneal metastasis-associated fibroblasts. In summary, we propose MMT as a potential source of ADC-based therapeutic targets for peritoneal carcinomatosis. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Intraperitoneal transfer of microRNA-29b-containing small extracellular vesicles can suppress peritoneal metastases of gastric cancer

Small extracellular vesicles (sEV) contain various microRNAs (miRNAs) and play crucial roles in the tumor metastatic process. Although miR-29b levels in peritoneal exosomes were markedly reduced in patients with peritoneal metastases (PM), their role has not been fully clarified. In this study, we asked whether the replacement of miR-29b can affect the development of PM in a murine model. UE6E7T-12, human bone marrow-derived mesenchymal stem cells (BMSCs), were transfected with miR-29b-integrating recombinant lentiviral vector and sEV were isolated from culture supernatants using ultracentrifugation. The sEV contained markedly increased amounts of miR-29b compared with negative controls. Treatment with transforming growth factor-β1 decreased the expression of E-cadherin and calretinin with increased expression of vimentin and fibronectin on human omental tissue-derived mesothelial cells (HPMCs). However, the effects were totally abrogated by adding miR-29b-rich sEV. The sEV inhibited proliferation and migration of HPMCs by 15% (p < 0.005, n = 6) and 70% (p < 0.005, n = 6), respectively, and inhibited adhesion of NUGC-4 and MKN45 to HPMCs by 90% (p < 0.0001, n = 5) and 77% (p < 0.0001, n = 5), respectively. MicroRNA-29b-rich murine sEV were similarly obtained using mouse BMSCs and examined for in vivo effects with a syngeneic murine model using YTN16P, a highly metastatic clone of gastric cancer cell. Intraperitoneal (IP) transfer of the sEV every 3 days markedly reduced the number of PM from YTN16P in the mesentery (p < 0.05, n = 6) and the omentum (p < 0.05, n = 6). Bone marrow mesenchymal stem cell-derived sEV are a useful carrier for IP administration of miR-29b, which can suppress the development of PM of gastric cancer.

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.

Lipid emulsions prevent postoperative abdominal adhesions

INTRODUCTION

Adhesions are the most common cause of long-term morbidity after abdominal surgery and most often cause various forms of intestinal passage disorders ranging from partial obstruction to complete, life-threatening intestinal obstruction. The aim of the present study was to evaluate the protective effect of intraperitoneally administered lipid emulsions on the formation of adhesions in larger animal model, as the lubricating effect of phospholipids and the mechanical barrier of the lipid component are combined with the anti-inflammatory effect of fish oil.

METHODS

Thirty-one female domestic pigs were randomly divided into three groups. At the end of the surgical procedure, a lipid emulsion or saline solution was applied intraperitoneally. After 14 days, an independent macroscopic, histological and immunohistochemical evaluation of the adhesions were performed.

RESULTS

Intraperitoneal administration of lipid emulsions significantly reduced the incidence of intra-abdominal adhesions. Microscopic examination demonstrated a significant reduction in the number of inflammatory elements and the amount of collagen in the adhesions, especially after administration of the fish oil-based emulsion. A simultaneous decrease in neovascularization was observed in the adhesions. Evaluation of the intestinal anastomosis did not reveal significant differences in healing between the groups.

CONCLUSION

Intraperitoneal administration of lipid emulsions can reduce the development of postoperative intra-abdominal adhesions by the combined action of phospholipids as important lubricants and lipids as a mechanical barrier. Their effect is caused by a reduction in proinflammatory and profibrotic mediators. At the same time, intraperitoneal administration of lipid emulsions does not impair healing of the anastomosis in larger animal model.

Connexin43 in Post-Surgical Peritoneal Adhesion Formation

OBJECTIVE

Post-surgical peritoneal adhesions are a serious problem for the quality of life and fertility. Yet there are no effective ways of preventing their occurrence. The gap junction protein Cx43 is known to be involved in fibrosis in several different organs and disease conditions often associated with inflammation. Here we examined the Cx43 dynamic expression in an ischemic button model of surgical adhesions.

METHODS

Using the mouse ischemic button model, Cx43 antisense was delivered in Pluronic gel to attenuate Cx43 expression. The severity of button formation and immunofluorescence analysis of Cx43 and TGF-β1 were performed. The concentration of tissue plasminogen activator via ELISA was also performed.

RESULTS

As early as 6 h after button formation, the Cx43 levels were elevated in and around the button and some weak adhesions were formed. By 24 h Cx43 levels had increased further and adhesions were more defined. At 7 days the adhesions were much more robust, opaque, and vascularized, requiring blunt or sharp dissection to break them. Cx43 antisense attenuated its upregulation and, reduced the number and severity of adhesions that formed.

CONCLUSION

Targeting Cx43 after surgical procedures may be a potential therapeutic strategy for preventing adhesion formation or at least reducing their severity.

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.

Monocyte-derived peritoneal macrophages protect C57BL/6 mice against surgery-induced adhesions

Peritoneal adhesions commonly occur after abdominal or pelvic surgery. These scars join internal organs to each other or to the cavity wall and can present with abdominal or pelvic pain, and bowel obstruction or female infertility. The mechanisms underlying adhesion formation remain unclear and thus, effective treatments are not forthcoming. Peritoneal macrophages accumulate after surgery and previous studies have attributed either pro- or anti-scarring properties to these cells. We propose that there are complex and nuanced responses after surgery with respect to both resident and also monocyte-derived peritoneal macrophage subpopulations. Moreover, we contend that differences in responses of specific macrophage subpopulations in part explain the risk of developing peritoneal scars. We characterized alterations in peritoneal macrophage subpopulations after surgery-induced injury using two strains of mice, BALB/c and C57BL/6, with known differences in macrophage response post-infection. At 14 days post-surgery, BALB/c mice displayed more adhesions compared with C57BL/6 mice. This increase in scarring correlated with a lower influx of monocyte-derived macrophages at day 3 post-surgery. Moreover, BALB/c mice showed distinct macrophage repopulation dynamics after surgery. To confirm a role for monocyte-derived macrophages, we used Ccr2-deficient mice as well as antibody-mediated depletion of CCR2 expressing cells during initial stages of adhesion formation. Both Ccr2-deficient and CCR2-depleted mice showed a significant increase in adhesion formation associated with the loss of peritoneal monocyte influx. These findings revealed an important protective role for monocyte-derived cells in reducing adhesion formation after surgery.

Bottlebrush inspired injectable hydrogel for rapid prevention of postoperative and recurrent adhesion

Postsurgical adhesion is a common clinic disease induced by surgical trauma, accompanying serious subsequent complications. Current non-surgical approaches of drugs treatment and biomaterial barrier administration only show limited prevention effects and couldn't effectively promote peritoneum repair. Herein, inspired by bottlebrush, a novel self-fused, antifouling, and injectable hydrogel is fabricated by the free-radical polymerization in aqueous solution between the methacrylate hyaluronic acid (HA-GMA) and N-(2-hydroxypropyl) methacrylamide (HPMA) monomer without any chemical crosslinkers, termed as H-HPMA hydrogel. The H-HPMA hydrogel can be tuned to perform excellent self-fused properties and suitable abdominal metabolism time. Intriguingly, the introduction of the ultra-hydrophilic HPMA chains to the H-HPMA hydrogel affords an unprecedented antifouling capability. The HPMA chains establish a dense hydrated layer that rapidly prevents the postsurgical adhesions and recurrent adhesions after adhesiolysis in vivo. The H-HPMA hydrogel can repair the peritoneal wound of the rat model within 5 days. Furthermore, an underlying mechanism study reveals that the H-HPMA hydrogel significantly regulated the mesothelial-to-mesenchymal transition (MMT) process dominated by the TGF-β-Smad2/3 signal pathway. Thus, we developed a simple, effective, and available approach to rapidly promote peritoneum regeneration and prevent peritoneal adhesion and adhesion recurrence after adhesiolysis, offering novel design ideas for developing biomaterials to prevent peritoneal adhesion.

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.

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.

Crosstalk of tumor stromal cells orchestrates invasion and spreading of gastric cancer

Tumors contain various stromal cells that support cancer progression. Some types of cancer, such as scirrhous gastric cancer, are characterized by large areas of fibrosis accompanied by cancer-associated fibroblasts (CAFs). Asporin (ASPN) is a small leucine-rich proteoglycan highly expressed in CAFs of various tumors. ASPN accelerates CAF migration and invasion, resulting in CAF-led cancer cell invasion. In addition, ASPN further upregulated the expression of genes specific to a characteristic subgroup of fibroblasts in tumors. These cells were preferentially located at the tumor periphery and could be generated by a unique mechanism involving the CAF-mediated education of normal fibroblasts (CEFs). In this review, we at first describe recent findings regarding the function of ASPN in the tumor microenvironment, as well as the mechanism involved in the generation of CEFs. CAFs are derived from heterogeneous origins besides resident normal fibroblasts. Among them, CAFs derived from mesothelial cells (mesothelial cell-derived CAF [MC-CAFs]) play pivotal roles in peritoneal carcinomatosis. We observed that MC-CAFs on the surfaces of organs also participate in tumor formation by infiltrating into the parenchyma, promoting local invasion by gastric cancers. This review also highlights the potential functions of macrophages in the formation of MC-CAFs in gastric cancers, by transfer the contents of cancer cell-derived extracellular vesicles.

The Inhibitory Effects of Naringin in a Rat Model of Postoperative Intraperitoneal Adhesion Formation

Background

Many attempts have been made to inhibit the formation of postoperative intraperitoneal adhesions, but the results have been discouraging. Therefore, the identification of effective preventative measures or treatments is of great importance. In this study, the substantial potential of naringin (NG) to reduce peritoneal adhesions was validated in a rat model.

Materials and Methods

A rat peritoneal adhesion model was established by abrasion of the cecum and its opposite intraperitoneal region under aseptic surgical conditions. After the operation, three groups of NG-treated rats were given 2 mL of NG by gavage at different concentrations (40, 60, or 80 mg/kg/d). The sham, control, and hyaluronan (HA) groups were given equal volumes of normal saline daily. On the 8th day, all rats were sacrificed 30 min after the administration of an activated carbon solution (10 mL/kg) by oral gavage. Intraperitoneal adhesion formation was adequately evaluated by necropsy, hematoxylin and eosin (HE) staining, Sirius red staining, immunofluorescence staining, enzyme-linked immunosorbent assays, and reactive oxygen species (ROS) probes. The gastrointestinal dynamics of the rats were assessed on the basis of a small intestinal charcoal powder propulsion test and the detection of motilin and gastrin levels in serum.

Results

Intraperitoneal adhesions were markedly reduced in the group of rats receiving high-dose NG. Compared with the control group, the high-dose NG group showed clear reductions in inflammatory reactions, oxidative stress, collagen deposition, and fibroblast formation in the adhesion tissue and enhanced gastrointestinal dynamics (P < 0.05).

Conclusion

NG alleviated the severity of intraperitoneal adhesions in a rat model by reducing inflammation, oxidative stress, collagen deposition, and fibroblast formation, highlighting the potential of NG as a drug candidate to prevent postoperative peritoneal adhesion formation.

A combination of hybrid polydopamine-human keratinocyte growth factor nanoparticles and sodium hyaluronate for the efficient prevention of postoperative abdominal adhesion formation

Postoperative abdominal adhesion (PAA) is one of the more universal complications of abdominal surgery with a frequent incidence. Currently available keratinocyte growth factor (KGF)-based glues for the prevention of adhesions remain a great bottleneck since their long-term biological activity in vivo is insufficient. In this study, we fabricated hybrid polydopamine (PDA)-KGF nanoparticles (PDA-KGF NPs) by using an in situ self-assembly and polymerization method. The physicochemical properties of the PDA-KGF nanoparticles were systematically characterized. The effect of preventing PAA in rats was evaluated by using hybrid PDA-KGF NPs combined with hyaluronate (Ha). The expression levels of inflammatory factors and the degree of inflammatory cell infiltration in the injured peritoneum were evaluated by enzyme-linked immunosorbent assays and hematoxylin-eosin staining, respectively. The levels of phospho-Src expression were revealed by Western blotting. The degree of fibrosis and the density of deposited collagen fibers were measured with real-time reverse-transcription polymerase chain reaction and picrosirius red staining. The results indicated that the PDA-KGF NPs combined with Ha greatly prevented the incidence of abdominal adhesion s and promoted the repair of mesothelial cells in injured peritoneum. More importantly, the PDA-KGF NPs combined with Ha obviously reduced collagen deposition and fibrosis and inhibited the inflammatory response. Our results suggest that PDA-KGF NPs combined with Ha are promising barrier-like biomaterials for the effective prevention of postoperative tissue adhesion. STATEMENT OF SIGNIFICANCE: Postoperative abdominal adhesion (PAA) as an inevitable postoperative complication affected the quality of life of patients. Currently available methods for preventing adhesions mainly employ degradable biomaterials. Previous research demonstrated that a hybrid keratinocyte growth factor (KGF)-sodium hyaluronate (Ha) gel could prevent the formation of PAAs. However, its clinical outcomes are not satisfactory since their bioactivity in vivo is too short. In this article, we fabricated hybrid polydopamine (PDA)-KGF nanoparticles (PDA-KGF NPs), which extend KGF bioactivity, effectively prevent PAA. Moreover, PDA-KGF NPs could remarkably reduce both collagen deposition and fibrosis, inhibit the inflammatory response, and promote mesothelial regeneration. Overall, the PDA-KGF NPs combined with Ha exhibit efficient antiadhesion properties, may provide a promising clinical protocol for the prevention of PAA.

MiR-29b may suppresses peritoneal metastases through inhibition of the mesothelial-mesenchymal transition (MMT) of human peritoneal mesothelial cells

Peritoneal dissemination is a major metastatic pathway for gastrointestinal and ovarian malignancies. The miR-29b family is downregulated in peritoneal fluids in patients with peritoneal metastases (PM). We examined the effect of miR-29b on mesothelial cells (MC) which play critical a role in the development of PM through mesothelial-mesenchymal transition (MMT). Human peritoneal mesothelial cells (HPMCs) were isolated from surgically resected omental tissue and MMT induced by stimulation with 10 ng/ml TGF-β1. MiR-29b mimics and negative control miR were transfected by lipofection using RNAiMAX and the effects on the MMT evaluated in vitro. HPMC produced substantial amounts of miR-29b which was markedly inhibited by TGF-β1. TGF-β1 stimulation of HPMC induced morphological changes with decreased expression of E-cadherin and calretinin, and increased expression of vimentin and fibronectin. TGF-β1 also enhanced proliferation and migration of HPMC as well as adhesion of tumor cells in a fibronectin dependent manner. However, all events were strongly abrogated by simultaneous transfection of miR-29b. MiR-29b inhibits TGF-β1 induced MMT and replacement of miR-29b in the peritoneal cavity might be effective to prevent development of PM partly through the effects on MC.

Intraperitoneal microbial contamination drives post-surgical peritoneal adhesions by mesothelial EGFR-signaling

Abdominal surgeries are lifesaving procedures but can be complicated by the formation of peritoneal adhesions, intra-abdominal scars that cause intestinal obstruction, pain, infertility, and significant health costs. Despite this burden, the mechanisms underlying adhesion formation remain unclear and no cure exists. Here, we show that contamination of gut microbes increases post-surgical adhesion formation. Using genetic lineage tracing we show that adhesion myofibroblasts arise from the mesothelium. This transformation is driven by epidermal growth factor receptor (EGFR) signaling. The EGFR ligands amphiregulin and heparin-binding epidermal growth factor, are sufficient to induce these changes. Correspondingly, EGFR inhibition leads to a significant reduction of adhesion formation in mice. Adhesions isolated from human patients are enriched in EGFR positive cells of mesothelial origin and human mesothelium shows an increase of mesothelial EGFR expression during bacterial peritonitis. In conclusion, bacterial contamination drives adhesion formation through mesothelial EGFR signaling. This mechanism may represent a therapeutic target for the prevention of adhesions after intra-abdominal surgery.

Development of a refined ex vivo model of peritoneal adhesion formation, and a role for connexin 43 in their development

Despite many advances across the surgical sciences, post-surgical peritoneal adhesions still pose a considerable risk in modern-day procedures and are highly undesirable. We have developed a novel mouse peritoneal strip ex vivo adhesion model which may serve to bridge the gap between single cell culture systems and in vivo animal drug testing for the assessment of potential anti-adhesion agents, and study of causality of the process. We investigated the optimal conditions for adhesion formation with mouse peritoneal tissue strips by modifying an existing ex vivo rat model of peritoneal adhesions. We assessed the impact of the following conditions on the formation of adhesions: contact pressure, abrasions, and the presence of clotted blood. Macroscopic adhesions were detected in all mouse peritoneal strips exposed to specific conditions, namely abrasions and clotted blood, where peritoneal surfaces were kept in contact with pressure using cotton gauze in a tissue cassette. Adhesions were confirmed microscopically. Interestingly, connexin 43, a gap junction protein, was found to be upregulated at sites of adhesions. Key features of this model were the use of padding the abraded tissue with gauze and the use of a standardised volume of clotted blood. Using this model, peritoneal strips cultured with clotted blood between abraded surfaces were found to reproducibly develop adhesion bands at 72 h. Our goal is to develop a model that can be used in genetically modified mice in order to dissect out the role of particular genes in adhesion formation and to test drugs to prevent adhesion formation.

TMIGD1 Inhibited Abdominal Adhesion Formation by Alleviating Oxidative Stress in the Mitochondria of Peritoneal Mesothelial Cells

Background

Postoperative abdominal adhesion remains one of the frequent complications after abdominal surgery and lacks effective intervention. Peritoneal mesothelial cell injury and healing play crucial roles in the process of adhesion formation, and identifying this mechanism might provide new insight into possible new therapeutic strategies for this disease. Transmembrane and immunoglobulin domain-containing 1 (TMIGD1) has been proven to protect renal epithelial cells from injury induced by oxidative stress and has also been identified as a novel adhesion molecule. Here, we investigated the role of TMIGD1 and its possible mechanism in adhesion formation.

Materials and Methods

Immunohistochemistry (IHC), qPCR, and immunofluorescence (IHF) were used to detect the expression of TMIGD1. The grade and tenacity score of adhesion were used to evaluate the adhesion formation conditions. A TMIGD1-overexpressing HMrSV5 cell line was established. MTT assay, Western blotting, Annexin V apoptosis analysis, and CK19 staining were used to measure mesothelial cell viability, apoptosis, and completeness. ROS and MDA detection were used to measure mesothelial cell oxidative stress levels. JC-1 staining, IHF, and transmission electron microscopy were performed to assess mitochondrial function. Scratch-wound and adhesion assays were used to evaluate the adhesion ability of mesothelial cells.

Results

First, we showed that TMIGD1 was decreased in mouse abdominal adhesion tissue and peritoneal mesothelial cells. Second, TMIGD1 overexpression inhibited adhesion formation. Third, TMIGD1 overexpression protected mesothelial cells from hydrogen peroxide- (H₂O₂-) induced oxidative stress injury. Fourth, TMIGD1 overexpression alleviated oxidative stress by protecting the mitochondrial function of mesothelial cells. In addition, TMIGD1 overexpression enhanced mesothelial cell adhesion.

Conclusion

Our findings suggest that TMIGD1 protects mesothelial cells from oxidative stress injury by protecting their mitochondrial function, which is decreased in regular abdominal adhesion tissue. In addition, TMIGD1 enhances peritoneal mesothelial cell adhesion to promote healing.

Post-Operative Adhesions: A Comprehensive Review of Mechanisms

Post-surgical adhesions are common in almost all surgical areas and are associated with significant rates of morbidity, mortality, and increased healthcare costs, especially when a patient requires repeat operative interventions. Many groups have studied the mechanisms driving post-surgical adhesion formation. Despite continued advancements, we are yet to identify a prevailing mechanism. It is highly likely that post-operative adhesions have a multifactorial etiology. This complex pathophysiology, coupled with our incomplete understanding of the underlying pathways, has resulted in therapeutic options that have failed to demonstrate safety and efficacy on a consistent basis. The translation of findings from basic and preclinical research into robust clinical trials has also remained elusive. Herein, we present and contextualize the latest findings surrounding mechanisms that have been implicated in post-surgical adhesion formation.

Prevention of Post-Operative Adhesions: A Comprehensive Review of Present and Emerging Strategies

Post-operative adhesions affect patients undergoing all types of surgeries. They are associated with serious complications, including higher risk of morbidity and mortality. Given increased hospitalization, longer operative times, and longer length of hospital stay, post-surgical adhesions also pose a great financial burden. Although our knowledge of some of the underlying mechanisms driving adhesion formation has significantly improved over the past two decades, literature has yet to fully explain the pathogenesis and etiology of post-surgical adhesions. As a result, finding an ideal preventative strategy and leveraging appropriate tissue engineering strategies has proven to be difficult. Different products have been developed and enjoyed various levels of success along the translational tissue engineering research spectrum, but their clinical translation has been limited. Herein, we comprehensively review the agents and products that have been developed to mitigate post-operative adhesion formation. We also assess emerging strategies that aid in facilitating precision and personalized medicine to improve outcomes for patients and our healthcare system.

Sterile Injury Repair and Adhesion Formation at Serosal Surfaces

Most multicellular organisms have a major body cavity containing vital organs. This cavity is lined by a mucosa-like serosal surface and filled with serous fluid which suspends many immune cells. Injuries affecting the major body cavity are potentially life-threatening. Here we summarize evidence that unique damage detection and repair mechanisms have evolved to ensure immediate and swift repair of injuries at serosal surfaces. Furthermore, thousands of patients undergo surgery within the abdominal and thoracic cavities each day. While these surgeries are potentially lifesaving, some patients will suffer complications due to inappropriate scar formation when wound healing at serosal surfaces defects. These scars called adhesions cause profound challenges for health care systems and patients. Therefore, reviewing the mechanisms of wound repair at serosal surfaces is of clinical importance. Serosal surfaces will be introduced with a short embryological and microanatomical perspective followed by a discussion of the mechanisms of damage recognition and initiation of sterile inflammation at serosal surfaces. Distinct immune cells populations are free floating within the coelomic (peritoneal) cavity and contribute towards damage recognition and initiation of wound repair. We will highlight the emerging role of resident cavity GATA6+ macrophages in repairing serosal injuries and compare serosal (mesothelial) injuries with injuries to the blood vessel walls. This allows to draw some parallels such as the critical role of the mesothelium in regulating fibrin deposition and how peritoneal macrophages can aggregate in a platelet-like fashion in response to sterile injury. Then, we discuss how serosal wound healing can go wrong, causing adhesions. The current pathogenetic understanding of and potential future therapeutic avenues against adhesions are discussed.

Post-Surgical Peritoneal Scarring and Key Molecular Mechanisms

Post-surgical adhesions are internal scar tissue and a major health and economic burden. Adhesions affect and involve the peritoneal lining of the abdominal cavity, which consists of a continuous mesothelial covering of the cavity wall and majority of internal organs. Our understanding of the full pathophysiology of adhesion formation is limited by the fact that the mechanisms regulating normal serosal repair and regeneration of the mesothelial layer are still being elucidated. Emerging evidence suggests that mesothelial cells do not simply form a passive barrier but perform a wide range of important regulatory functions including maintaining a healthy peritoneal homeostasis as well as orchestrating events leading to normal repair or pathological outcomes following injury. Here, we summarise recent advances in our understanding of serosal repair and adhesion formation with an emphasis on molecular mechanisms and novel gene expression signatures associated with these processes. We discuss changes in mesothelial biomolecular marker expression during peritoneal development, which may help, in part, to explain findings in adults from lineage tracing studies using experimental adhesion models. Lastly, we highlight examples of where local tissue specialisation may determine a particular response of peritoneal cells to injury.

Mechanisms of Peritoneal Fibrosis: Focus on Immune Cells-Peritoneal Stroma Interactions

Peritoneal fibrosis is characterized by abnormal production of extracellular matrix proteins leading to progressive thickening of the submesothelial compact zone of the peritoneal membrane. This process may be caused by a number of insults including pathological conditions linked to clinical practice, such as peritoneal dialysis, abdominal surgery, hemoperitoneum, and infectious peritonitis. All these events may cause acute/chronic inflammation and injury to the peritoneal membrane, which undergoes progressive fibrosis, angiogenesis, and vasculopathy. Among the cellular processes implicated in these peritoneal alterations is the generation of myofibroblasts from mesothelial cells and other cellular sources that are central in the induction of fibrosis and in the subsequent functional deterioration of the peritoneal membrane. Myofibroblast generation and activity is actually integrated in a complex network of extracellular signals generated by the various cellular types, including leukocytes, stably residing or recirculating along the peritoneal membrane. Here, the main extracellular factors and the cellular players are described with emphasis on the cross-talk between immune system and cells of the peritoneal stroma. The understanding of cellular and molecular mechanisms underlying fibrosis of the peritoneal membrane has both a basic and a translational relevance, since it may be useful for setup of therapies aimed at counteracting the deterioration as well as restoring the homeostasis of the peritoneal membrane.

LncRNA SPOCD1-AS from ovarian cancer extracellular vesicles remodels mesothelial cells to promote peritoneal metastasis via interacting with G3BP1

Background

Metastasis is the key cause of death in ovarian cancer patients. To figure out the biological nature of cancer metastasis is essential for developing effective targeted therapy. Here we investigate how long non-coding RNA (lncRNA) SPOCD1-AS from ovarian cancer extracellular vesicles (EVs) remodel mesothelial cells through a mesothelial-to-mesenchymal transition (MMT) manner and facilitate peritoneal metastasis.

Methods

EVs purified from ovarian cancer cells and ascites of patients were applied to mesothelial cells. The MMT process of mesothelial cells was assessed by morphology observation, western blot analysis, migration assay and adhesion assay. Altered lncRNAs of EV-treated mesothelial cells were screened by RNA sequencing and identified by qRT-PCR. SPOCD1-AS was overexpressed or silenced by overexpression lentivirus or shRNA, respectively. RNA pull-down and RNA immunoprecipitation assays were conducted to reveal the mechanism by which SPOCD1-AS remodeled mesothelial cells. Interfering peptides were synthesized and applied. Ovarian cancer orthotopic implantation mouse model was established in vivo.

Results

We found that ovarian cancer-secreted EVs could be taken into recipient mesothelial cells, induce the MMT phenotype and enhance cancer cell adhesion to mesothelial cells. Furthermore, SPOCD1-AS embedded in ovarian cancer-secreted EVs was transmitted to mesothelial cells to induce the MMT process and facilitate peritoneal colonization in vitro and in vivo. SPOCD1-AS induced the MMT process of mesothelial cells via interacting with G3BP1 protein. Additionally, G3BP1 interfering peptide based on the F380/F382 residues was able to block SPOCD1-AS/G3BP1 interaction, inhibit the MMT phenotype of mesothelial cells, and diminish peritoneal metastasis in vivo.

Conclusions

Our findings elucidate the mechanism associated with EVs and their cargos in ovarian cancer peritoneal metastasis and may provide a potential approach for metastatic ovarian cancer therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01899-6.

Advancement of Biomaterial-Based Postoperative Adhesion Barriers

Postoperative peritoneal adhesion (PPA) is a prevalent incidence that generally happens during the healing process of traumatized tissues. It causes multiple severe complications such as intestinal obstruction, chronic abdominal pain, and female infertility. To prevent PPA, several antiadhesion materials and drug delivery systems composed of biomaterials are used clinically, and clinical antiadhesive is one of the important applications nowadays. In addition to several commercially available materials, like film, spray, injectable hydrogel, powder, or solution type have been energetically studied based on natural and synthetic biomaterials such as alginate, hyaluronan, cellulose, starch, chondroitin sulfate, polyethylene glycol, polylactic acid, etc. Moreover, many kinds of animal adhesion models, such as cecum abrasion models and unitary horn models, are developed to evaluate new materials' efficacy. A new animal adhesion model based on hepatectomy and conventional animal adhesion models is recently developed and a new adhesion barrier by this new model is also developed. In summary, many kinds of materials and animal models are studied; thus, it is quite important to overview this field's current progress. Here, PPA is reviewed in terms of the species of biomaterials and animal models and several problems to be solved to develop better antiadhesion materials in the future are discussed.

A review of physiological and cellular mechanisms underlying fibrotic postoperative adhesion

Postoperative adhesions (PA) are fibrotic tissues that are the most common driver of long-term morbidity after abdominal and pelvic surgery. The optimal drug or material to prevent adhesion formation has not yet been discovered. Comprehensive understanding of cellular and molecular mechanisms of adhesion process stimulates the design of future anti-adhesive strategies. Recently, disruption of peritoneal mesothelial cells were suggested as the 'motor' of PA formation, followed by a cascade of events (coagulation, inflammation, fibrinolysis) and influx of various immune cells, ultimately leading to a fibrous exudate. We showed that a variety of immune cells were recruited into adhesive peritoneal tissues in patients with small bowel obstruction caused by PA. The interactions among various types of immune cells contribute to PA development following peritoneal trauma. Our review focuses on the specific role of different immune cells in cellular and humoral mechanisms underpinning adhesion development.

Potential of a facile sandwiched electrospun scaffold loaded with ibuprofen as an anti-adhesion barrier

The combination of nanofibre-based barriers and anti-adhesion drugs is potentially useful for adhesion prevention after ventral surgeries. However, drug molecules exposed to the surface of barriers easily result in an initial burst that is sharp, thus limiting the anti-adhesion efficiency. In this study, we developed a sandwiched electrospun scaffold loaded with ibuprofen (Sandwich) serving as a physical barrier, as well as an effectual carrier delivering it into the injured site for enhancing anti-adhesion capability. This Sandwich scaffold exhibited significantly a reduced initial burst of drug release in the first hour and a prolonged delivery for ibuprofen over 14 days, expected to provide the long-term anti-adhesion capability. In vitro study on fibroblasts showed that incorporation of ibuprofen effectively inhibited their adhesion and proliferation, and developed Sandwich maintained the least adhesion of L-929 after 5 days of culture (<20%). For RAW 264.7 macrophages, worse cell adhesion and poorer TNF-α production of Sandwich indicated its superior anti-inflammatory effect. In summary, the sandwiched ibuprofen-loaded scaffold showed promising potential for preventing adhesion formation.

Mesothelial Cells Participate in Endometriosis Fibrogenesis Through Platelet-Induced Mesothelial-Mesenchymal Transition

CONTEXT

While fibrosis in endometriosis has recently loomed prominently, the sources of myofibroblasts, the principal effector cell in fibrotic diseases, remain largely obscure. Mesothelial cells (MCs) can be converted into myofibroblasts through mesothelial-mesenchymal transition (MMT) in many fibrotic diseases and adhesion.

OBJECTIVE

To evaluate whether MCs contribute to the progression and fibrogenesis in endometriosis through MMT.

SETTING, DESIGN, PATIENTS, INTERVENTION, AND MAIN OUTCOME MEASURES

Dual immunofluorescence staining and immunohistochemistry using antibodies against calretinin, Wilms' tumor-1 (WT-1), and α-smooth muscle actin (α-SMA) were performed on lesion samples from 30 patients each with ovarian endometrioma (OE) and deep endometriosis (DE), and 30 normal endometrial (NE) tissue samples. Human pleural and peritoneal MCs were co-cultured with activated platelets or control medium with and without neutralization of transforming growth factor β1 (TGF-β1) and/or platelet-derived growth factor receptor (PDGFR) and their morphology, proliferation, and expression levels of genes and proteins known to be involved in MMT were evaluated, along with their migratory and invasive propensity, contractility, and collagen production.

RESULTS

The number of calretinin/WT-1 and α-SMA dual-positive fibroblasts in OE/DE lesions was significantly higher than NE samples. The extent of lesional fibrosis correlated positively with the lesional α-SMA staining levels. Human MCs co-cultured with activated platelets acquire a morphology suggestive of MMT, concomitant with increased proliferation, loss of calretinin expression, and marked increase in expression of mesenchymal markers. These changes coincided with functional differentiation as reflected by increased migratory and invasive capacity, contractility, and collagen production. Neutralization of TGF-β1 and PDGFR signaling abolished platelet-induced MMT in MCs.

CONCLUSIONS

MCs contribute to lesional progression and fibrosis through platelet-induced MMT.

Neutrophil and monocyte kinetics play critical roles in mouse peritoneal adhesion formation

Peritoneal adhesions are pathological fibroses that ensnare organs after abdominal surgery. This dense connective tissue can cause small bowel obstruction, female infertility, and chronic abdominal pain. The pathogenesis of adhesions is a fibrotic response to tissue damage coordinated between mesothelial cells, fibroblasts, and immune cells. We have previously demonstrated that peritoneal adhesions are a consequence of mechanical injury to the mesothelial layer sustained during surgery. Neutrophils are among the first leukocytes involved in the early response to tissue damage. Here, we show that when subjected to mechanical stress, activated mesothelial cells directly recruit neutrophils and monocytes through upregulation of chemokines such as CXCL1 and monocyte chemoattractant protein 1 (MCP-1). We find that neutrophils within the adhesion sites undergo cell death and form neutrophil extracellular traps (NETosis) that contribute to pathogenesis. Conversely, tissue-resident macrophages were profoundly depleted throughout the disease time course. We show that this is distinct from traditional inflammatory kinetics such as after sham surgery or chemically induced peritonitis, and suggest that adhesions result from a primary difference in inflammatory kinetics. We find that transient depletion of circulating neutrophils significantly decreases adhesion burden, and further recruitment of monocytes with thioglycolate or MCP-1 also improves outcomes. Our findings suggest that the combination of neutrophil depletion and monocyte recruitment is sufficient to prevent adhesion formation, thus providing insight for potential clinical interventions.

Increased miR-7641 Levels in Peritoneal Hyalinizing Vasculopathy in Long-Term Peritoneal Dialysis Patients

Peritoneal hyalinizing vasculopathy (PHV) represents the cornerstone of long-term peritoneal dialysis (PD), and especially characterizes patients associated with encapsulating peritoneal sclerosis. However, the mechanisms of PHV development remain unknown. A cross sectional study was performed in 100 non-selected peritoneal biopsies of PD patients. Clinical data were collected and lesions were evaluated by immunohistochemistry. In selected biopsies a microRNA (miRNA)-sequencing analysis was performed. Only fifteen patients (15%) showed PHV at different degrees. PHV prevalence was significantly lower among patients using PD fluids containing low glucose degradation products (GDP) (5.9% vs. 24.5%), angiotensin converting enzyme inhibitors (ACEIs) (7.5% vs. 23.4%), statins (6.5% vs. 22.6%) or presenting residual renal function, suggesting the existence of several PHV protective factors. Peritoneal biopsies from PHV samples showed loss of endothelial markers and induction of mesenchymal proteins, associated with collagen IV accumulation and wide reduplication of the basement membrane. Moreover, co-expression of endothelial and mesenchymal markers, as well as TGF-β1/Smad3 signaling activation were found in PHV biopsies. These findings suggest that an endothelial-to-mesenchymal transition (EndMT) process was taking place. Additionally, significantly higher levels of miR-7641 were observed in severe PHV compared to non-PHV peritoneal biopsies. Peritoneal damage by GDPs induce miRNA deregulation and an EndMT process in submesothelial vessels, which could contribute to collagen IV accumulation and PHV.