Most patients with ovarian cancer (OvCA) present peritoneal disseminated disease at the time of diagnosis. During peritoneal metastasis, cancer cells detach from the primary tumor and disseminate through the intraperitoneal fluid. The peritoneal mesothelial cell (PMC) monolayer that lines the abdominal cavity is the first barrier encountered by OvCA cells. Subsequent progression of tumors through the peritoneum leads to the accumulation into the peritoneal stroma of a sizeable population of carcinoma-associated fibroblasts (CAFs), which is mainly originated from a mesothelial-to-mesenchymal transition (MMT) process. A common characteristic of OvCA patients is the intraperitoneal accumulation of ascitic fluid, which is composed of cytokines, chemokines, growth factors, miRNAs, and proteins contained in exosomes, as well as tumor and mesothelial suspended cells, among other components that vary in proportion between patients. Exosomes are small extracellular vesicles that have been shown to mediate peritoneal metastasis by educating a pre-metastatic niche, promoting the accumulation of CAFs via MMT, and inducing tumor growth and chemoresistance. This review summarizes and discusses the pivotal role of exosomes and MMT as mediators of OvCA peritoneal colonization and as emerging diagnostic and therapeutic targets.

During peritoneal metastasis, cancer cells spread from abdominal solid tumors, disseminate through the peritoneal fluid and attach to and invade through mesothelial cells (MCs) that line the peritoneum. Intestinal adenocarcinomas originating in the mucosa infiltrate the submucosa, muscle layer, and serosa in order to finally colonize the peritoneal cavity. However, the mechanism by which metastatic cells leave the primary tumor and reach the peritoneal cavity has not been previously described. Hence, we investigate whether MCs lining visceral peritoneum, through a mesothelial-to-mesenchymal transition (MMT), are a source of carcinoma-associated fibroblasts (CAFs), which could contribute to cancer progression toward the peritoneal cavity. CAFs detected in biopsies from patients with superficially invasive colorectal cancer differed from locally advanced tumors. An aberrant accumulation of myofibroblasts expressing mesothelial markers was found in the stroma of deeply infiltrative tumors located in the neighborhood of a frequently activated mesothelium. We suggest that MMT is a key event in the early stages of peritoneal dissemination.

Approximately 25% of colorectal cancer (CRC) patients develop peritoneal metastasis, a condition associated with a bleak prognosis. The CRC peritoneal dissemination cascade involves the shedding of cancer cells from the primary tumor, their transport through the peritoneal cavity, their adhesion to the peritoneal mesothelial cells (PMCs) that line all peritoneal organs, and invasion of cancer cells through this mesothelial cell barrier and underlying stroma to establish new metastatic foci. Exosomes produced by cancer cells have been shown to influence many processes related to cancer progression and metastasis. In epithelial ovarian cancer these extracellular vesicles (EVs) have been shown to favor different steps of the peritoneal dissemination cascade by changing the functional phenotype of cancer cells and PMCs. Little is currently known, however, about the roles played by exosomes in the pathogenesis and peritoneal metastasis cascade of CRC and especially about the molecules that mediate their interaction and uptake by target PMCs and tumor cells. We isolated exosomes by size−exclusion chromatography from CRC cells and performed cell-adhesion assays to immobilized exosomes in the presence of blocking antibodies against surface proteins and measured the uptake of fluorescently-labelled exosomes. We report here that the interaction between integrin α5β1 on CRC cells (and PMCs) and its ligand ADAM17 on exosomes mediated the binding and uptake of CRC-derived exosomes. Furthermore, this process was negatively regulated by the expression of tetraspanin CD9 on exosomes.

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.

Tissue trauma initiates inflammation that can lead to fibrotic complications such as postoperative peritoneal adhesions, which contribute to chronic pain, infertility, and bowel obstruction. Despite their prevalence and impact, effective interventions to prevent adhesion formation remain limited. In this study, we evaluated a sprayable extracellular matrix (ECM) hydrogel as a barrier to protect healing tissues and reduce adhesion formation after abdominal surgery. In both mouse and rabbit models of colorectal and gynecologic procedures, ECM hydrogel application resulted in a substantial reduction in adhesion severity. Mechanistic studies demonstrated that the hydrogel promotes preservation or restoration of the mesothelial lining while modulating early local inflammation. Treated tissues exhibited reduced expression of inflammatory cytokines, including IL-1β, and maintained an intact mesothelial surface with fewer activated myofibroblasts compared with synthetic hydrogel and controls. Immunohistochemical analysis, transcriptomic profiling of mesothelial cells, and in vitro mechanical stretch experiments revealed that the ECM hydrogel mitigates mesothelial-to-mesenchymal transition. These findings suggest that the hydrogel not only provides a physical barrier but also serves as a biological modulator, shielding tissue from mechanical and inflammatory cues that drive adhesion formation. Overall, this study identifies a dual-function, biologically active ECM hydrogel capable of protecting healing tissues and reducing adhesion development in preclinical surgical models. These results support the potential of ECM hydrogel as a clinically translatable, biocompatible strategy for improving postsurgical healing outcomes and reducing adhesion-related complications.

Surgical Techniques For Catheter Placement And 5/6 Nephrectomy In Murine Models Of Peritoneal Dialysis. JoVE publishes peer-reviewed scientific video protocols to accelerate biological, medical, chemical and physical research. Watch our scientific video articles. JoVE is the world-leading producer and provider of science videos with the mission to improve scientific research, scientific journals, and education. Millions of scientists, educators and students at thousands of universities, colleges, hospitals and biopharmaceutical companies worldwide use JoVE for their research, teaching and learning.