Isolation of functional mature peritoneal macrophages from healthy humans

Macrophage variants in laboratory research: most are well done, but some are RAW

Macrophages play a pivotal role in the innate immune response. While their most characteristic function is phagocytosis, it is important not to solely characterize macrophages by this activity. Their crucial roles in body development, homeostasis, repair, and immune responses against pathogens necessitate a broader understanding. Macrophages exhibit remarkable plasticity, allowing them to modify their functional characteristics in response to the tissue microenvironment (tissue type, presence of pathogens or inflammation, and specific signals from neighboring cells) swiftly. While there is no single defined "macrophage" entity, there is a diverse array of macrophage types because macrophage ontogeny involves the differentiation of progenitor cells into tissue-resident macrophages, as well as the recruitment and differentiation of circulating monocytes in response to tissue-specific cues. In addition, macrophages continuously sense and respond to environmental cues and tissue conditions, adjusting their functional and metabolic states accordingly. Consequently, it is of paramount importance to comprehend the heterogeneous origins and functions of macrophages employed in in vitro studies, as each available in vitro macrophage model is associated with specific sets of strengths and limitations. This review centers its attention on a comprehensive comparison between immortalized mouse macrophage cell lines and primary mouse macrophages. It provides a detailed analysis of the strengths and weaknesses inherent in these in vitro models. Finally, it explores the subtle distinctions between diverse macrophage cell lines, offering insights into numerous factors beyond the model type that can profoundly influence macrophage function.

Human tissue-resident peritoneal macrophages reveal resistance towards oxidative cell stress induced by non-invasive physical plasma

In the context of multimodal treatments for abdominal cancer, including procedures such as cytoreductive surgery and intraperitoneal chemotherapy, recurrence rates remain high, and long-term survival benefits are uncertain due to post-operative complications. Notably, treatment-limiting side effects often arise from an uncontrolled activation of the immune system, particularly peritoneally localized macrophages, leading to massive cytokine secretion and phenotype changes. Exploring alternatives, an increasing number of studies investigated the potential of plasma-activated liquids (PAL) for adjuvant peritoneal cancer treatment, aiming to mitigate side effects, preserve healthy tissue, and reduce cytotoxicity towards non-cancer cells. To assess the non-toxicity of PAL, we isolated primary human macrophages from the peritoneum and subjected them to PAL exposure. Employing an extensive methodological spectrum, including flow cytometry, Raman microspectroscopy, and DigiWest protein analysis, we observed a pronounced resistance of macrophages towards PAL. This resistance was characterized by an upregulation of proliferation and anti-oxidative pathways, countering PAL-derived oxidative stress-induced cell death. The observed cellular effects of PAL treatment on human tissue-resident peritoneal macrophages unveil a potential avenue for PAL-derived immunomodulatory effects within the human peritoneal cavity. Our findings contribute to understanding the intricate interplay between PAL and macrophages, shedding light on the promising prospects for PAL in the adjuvant treatment of peritoneal cancer.

Optimization of peritoneal fluid and leukocyte collection in patients with endometriosis

OBJECTIVE

To propose a standardized protocol for peritoneal free fluid and leukocyte sample collection in women with endometriosis suitable for biomedical research on the basis of the surgical procedure, the clinical and technical conditions, and the quality of the samples obtained.

DESIGN

Video showing the step-by-step collection procedure and the suitability of samples obtained for biomedical research.

SUBJECTS

This study included 103 women with confirmed endometriosis by pathology analysis, who signed informed consent and were recruited from the Hospital "Virgen de la Arrixaca", Murcia, Spain. The study was approved by the Ethics Committee of University of Murcia (CEI 3156/2020).

MAIN OUTCOME MEASURES

We analyzed the presence of free fluid in the peritoneal cavity and its relationship with hormonal treatment intake. In addition, the presence of blood contamination, the number of viable leukocytes and macrophages in free peritoneal fluid and lavages as well as their relationship with the lavage volume used, the body mass index, and the age of patients were analyzed.

RESULTS

The presence of free peritoneal fluid, in which cells and molecules could be quantified, was scarce in the patients (21%), and it was not significantly related to hormonal treatment intake. The cell viability was higher than 98% in all collected samples; although 54% showed good quality and enough cellularity to be used in biomedical research, 40% were contaminated with blood and 6% had low cellularity. The number of leukocytes and macrophages recovered from the peritoneal lavages correlated positively with the lavage volume used and negatively with the body mass index and was independent of the age of the patients.

CONCLUSION

We describe a standardized step-by-step procedure for peritoneal fluid and leukocyte collection in women with endometriosis, suitable for biomedical research, taking into account that not all women present free fluid in the peritoneal cavity. We propose to increase the lavage volume recommended by the World Endometriosis Research Foundation from 10 mL to at least 40 mL of sterile saline solution and its mobilization for at least 30 seconds within the peritoneal cavity, especially in patients with higher body mass index, to improve the efficiency of the procedure.

Efficacy evaluation of chimeric antigen receptor-modified human peritoneal macrophages in the treatment of gastric cancer

BACKGROUND

Gastric cancer is one of the most common cancers. Peritoneal carcinomatosis (PC) appears to be the most common pattern of recurrence, and more than half of the GC patients eventually die from PC. Novel strategies for the management of patients with PC are urgently needed. Recently, rapid progress has been made in adoptive transfer therapy by using macrophages as the effector cells due to their capabilities of phagocytosis, antigen presentation, and high penetration. Here, we generated a novel macrophage-based therapy and investigated anti-tumoral effects on GC and potential toxicity.

METHODS

We developed a novel Chimeric Antigen Receptor-Macrophage (CAR-M) based on genetically modifying human peritoneal macrophages (PMs), expressing a HER2-FcεR1γ-CAR (HF-CAR). We tested HF-CAR macrophages in a variety of GC models in vitro and in vivo.

RESULTS

HF-CAR-PMs specifically targeted HER2-expressed GC, and harboured the FcεR1γ moieties to trigger engulfment. Intraperitoneal administration of HF-CAR-PMs significantly facilitated the HER2-positive tumour regression in PC mouse model and prolonged the overall survival rate. In addition, the combined use of oxaliplatin and HF-CAR-PMs exhibited significantly augment anti-tumour activity and survival benefit.

CONCLUSIONS

HF-CAR-PMs could represent an exciting therapeutic option for patients with HER2-positive GC cancer, which should be tested in carefully designed clinical trials.

Intraperitoneal metastasis of ovarian cancer: new insights on resident macrophages in the peritoneal cavity

Ovarian cancer metastasis occurs primarily in the peritoneal cavity. Orchestration of cancer cells with various cell types, particularly macrophages, in the peritoneal cavity creates a metastasis-favorable environment. In the past decade, macrophage heterogeneities in different organs as well as their diverse roles in tumor settings have been an emerging field. This review highlights the unique microenvironment of the peritoneal cavity, consisting of the peritoneal fluid, peritoneum, and omentum, as well as their own resident macrophage populations. Contributions of resident macrophages in ovarian cancer metastasis are summarized; potential therapeutic strategies by targeting such cells are discussed. A better understanding of the immunological microenvironment in the peritoneal cavity will provide a stepping-stone to new strategies for developing macrophage-based therapies and is a key step toward the unattainable eradication of intraperitoneal metastasis of ovarian cancer.

Deficiency of MST1 in endometriosis related peritoneal macrophages promoted the autophagy of ectopic endometrial stromal cells by IL-10

Changes in the function of peritoneal macrophages contribute to the homeostasis of the peritoneal immune microenvironment in endometriosis. The mechanism by which ectopic tissues escape phagocytic clearance by macrophages to achieve ectopic colonization and proliferation is unknown. The expression of CD163 in peritoneal macrophages in patients with endometriosis is increased, with the overexpression of MAPK, which can promote the M2-type polarization of macrophages and reduce their ability to phagocytose ectopic endometrial cells. As an upstream regulator of MAPK, MST1 expression is deficient in peritoneal macrophages of patients with endometriosis. This process is regulated by miR-887-5p, a noncoding RNA targeting MST1. Moreover, MST1-knockout macrophages secrete anti-inflammatory factor IL-10, which promotes autophagy of ectopic endometrial stromal cells. These results suggest that MST1 deficient macrophages may accelerate the autophagy of ectopic endometrium via IL-10 which was regulated by miR-887-5p.

Spontaneous Bacterial Peritonitis in Decompensated Liver Cirrhosis—A Literature Review

Background: Spontaneous bacterial peritonitis (SBP) is defined as a bacterial infection of the ascitic fluid without a surgically treatable intra-abdominal infection source. SBP is a common, severe complication in cirrhosis patients with ascites, and if left untreated, in-hospital mortality may exceed 90%. However, the incidence of SBP has been lowered to approx. 20% through early diagnosis and antibiotic therapy. Clinical awareness, prompt diagnosis, and immediate treatment are advised when caring for these patients to reduce mortality and morbidity. Aim: To discuss important issues comprising types of SBP, pathogenesis, bacteriology, including the emergence of multidrug-resistant (MDR) microorganisms, prompt diagnosis, risk factors, prognosis, treatment strategies, as well as recurrence prevention through antibiotic prophylaxis until liver transplantation and future trends in treating and preventing SBP in detail. Methods: This article is a literature review and appraisal of guidelines, randomized controlled trials, meta-analyses, and other review articles found on PubMed from between 1977 and 2022. Results: There are three types of SBP. Bacterial translocation from GI tract is the most common source of SBP. Therefore, two thirds of SBP cases were caused by Gram-negative bacilli, of which Escherichia coli is the most frequently isolated pathogen. However, a trend of Gram-positive cocci associated SBP has been demonstrated in recent years, possibly related to more invasive procedures and long-term quinolone prophylaxis. A diagnostic paracentesis should be performed in all patients with cirrhosis and ascites who require emergency room care or hospitalization, who demonstrate or report consistent signs/symptoms in order to confirm evidence of SBP. Distinguishing SBP from secondary bacterial peritonitis is essential because the conditions require different therapeutic strategies. The standard treatment for SBP is prompt broad-spectrum antibiotic administration and should be tailored according to community-acquired SBP, healthcare-associated or nosocomial SBP infections and local resistance profile. Albumin supplementation, especially in patients with renal impairment, is also beneficial. Selective intestinal decontamination is associated with a reduced risk of bacterial infection and mortality in high-risk group. Conclusions: The standard treatment for SBP is prompt broad-spectrum antibiotic administration and should be tailored according to community-acquired SBP, healthcare-associated or nosocomial SBP infections and local resistance profile. Since the one-year overall mortality rates for SBP range from 53.9 to 78%, liver transplantation should be seriously considered for SBP survivors who are good candidates for transplantation. Further development of non-antibiotic strategies based on pathogenic mechanisms are also urgently needed.

Plasticity of monocytes and macrophages in cirrhosis of the liver

Cirrhosis of the liver is a systemic condition with raising prevalence worldwide. Patients with cirrhosis are highly susceptible to develop bacterial infections leading to acute decompensation and acute-on-chronic liver failure both associated with a high morbidity and mortality and sparse therapeutic options other than transplantation. Mononuclear phagocytes play a central role in innate immune responses and represent a first line of defence against pathogens. Their function includes phagocytosis, killing of bacteria, antigen presentation, cytokine production as well as recruitment and activation of immune effector cells. Liver injury and development of cirrhosis induces activation of liver resident Kupffer cells and recruitment of monocytes to the liver. Damage- and pathogen-associated molecular patterns promote systemic inflammation which involves multiple compartments besides the liver, such as the circulation, gut, peritoneal cavity and others. The function of circulating monocytes and tissue macrophages is severely impaired and worsens along with cirrhosis progression. The underlying mechanisms are complex and incompletely understood. Recent 'omics' technologies help to transform our understanding of cellular diversity and function in health and disease. In this review we point out the current state of knowledge on phenotypical and functional changes of monocytes and macrophages during cirrhosis evolution in different compartments and their role in disease progression. We also discuss the value of potential prognostic markers for cirrhosis-associated immuneparesis, and future immunotherapeutic strategies that may reduce the need for transplantation and death.

Recent insights into the characteristics and role of peritoneal macrophages from ascites of cirrhotic patients

Macrophages are a diverse myeloid cell population involved in innate and adaptive immune responses, embryonic development, wound repair, and regulation of tissue homeostasis. These cells link the innate and adaptive immunities and are crucial in the development and sustainment of various inflammatory diseases. Macrophages are tissue-resident cells in steady-state conditions; however, they are also recruited from blood monocytes after local pathogen invasion or tissue injury. Peritoneal macrophages vary based on their cell complexity, phenotype, and functional capabilities. These cells regulate inflammation and control bacterial infections in the ascites of decompensated cirrhotic patients. Our recent work reported several phenotypic and functional characteristics of these cells under both healthy and pathological conditions. A direct association between cell size, CD14/CD16 expression, intracellular level of GATA-6, and expression of CD206 and HLA-DR activation/maturation markers, indicate that the large peritoneal macrophage CD14^highCD16^high subset constitutes the mature phenotype of human resident peritoneal macrophages during homeostasis. Moreover, elevated expression of CD14/CD16 is related to the phagocytic capacity. The novel large CD14^highCD16^high peritoneal subpopulation is increased in the ascites of cirrhotic patients and is highly sensitive to lipopolysaccharide (LPS)-induced activation, thereby exhibiting features of inflammatory priming. Thus, phosphorylation of ERK1/2, PKB/Akt, and c-Jun is remarkably increased in response to LPS in vitro, whereas that of p38 MAPK is reduced compared with the monocyte-derived macrophages from the blood of healthy controls. Furthermore, in vitro activated monocyte-derived macrophages from ascites of cirrhotic patients secreted significantly higher levels of IL-6, IL-10, and TNF-α and lower amounts of IL-1β and IL-12 than the corresponding cells from healthy donor’s blood. Based on these results, other authors have recently reported that the surface expression level of CD206 can be used to identify mature, resident, inflammatory peritoneal macrophages in patients with cirrhosis. Soluble CD206 is released from activated large peritoneal macrophages, and increased concentrations in patients with cirrhosis and spontaneous bacterial peritonitis (SBP) indicate reduced odds of survival for 90 d. Hence, the level of soluble CD206 in ascites might be used to identify patients with SBP at risk of death. In conclusion, peritoneal macrophages present in ascites of cirrhotic patients display multiple phenotypic modifications characterized by reduced ratio of cells expressing several membrane markers, together with an increase in the ratios of complex and intermediate subpopulations and a decrease in the classic-like subset. These modifications may lead to the identification of novel pharmaceutical targets for prevention and treatment of hepatic damage.

The Role of Peritoneal Macrophages in Endometriosis

Endometriosis is an estrogen-dependent gynecological disorder, defined as the growth of endometrial stromal cells and glands at extrauterine sites. Endometriotic lesions are more frequently located into the abdominal cavity, although they can also be implanted in distant places. Among its etiological factors, the presence of immune dysregulation occupies a prominent place, pointing out the beneficial and harmful outcomes of macrophages in the pathogenesis of this disease. Macrophages are tissue-resident cells that connect innate and adaptive immunity, playing a key role in maintaining local homeostasis in healthy conditions and being critical in the development and sustainment of many inflammatory diseases. Macrophages accumulate in the peritoneal cavity of women with endometriosis, but their ability to clear migrated endometrial fragments seems to be inefficient. Hence, the characteristics of the peritoneal immune system in endometriosis must be further studied to facilitate the search for new diagnostic and therapeutic tools. In this review, we summarize recent relevant advances obtained in both mouse, as the main animal model used to study endometriosis, and human, focusing on peritoneal macrophages obtained from endometriotic patients and healthy donors, under the perspective of its future clinical translation to the role that these cells play on this pathology.

Macrophages in Chronic Liver Failure: Diversity, Plasticity and Therapeutic Targeting

Chronic liver injury results in immune-driven progressive fibrosis, with risk of cirrhosis development and impact on morbidity and mortality. Persistent liver cell damage and death causes immune cell activation and inflammation. Patients with advanced cirrhosis additionally experience pathological bacterial translocation, exposure to microbial products and chronic engagement of the immune system. Bacterial infections have a high incidence in cirrhosis, with spontaneous bacterial peritonitis being the most common, while the subsequent systemic inflammation, organ failure and immune dysregulation increase the mortality risk. Tissue-resident and recruited macrophages play a central part in the development of inflammation and fibrosis progression. In the liver, adipose tissue, peritoneum and intestines, diverse macrophage populations exhibit great phenotypic and functional plasticity determined by their ontogeny, epigenetic programming and local microenvironment. These changes can, at different times, promote or ameliorate disease states and therefore represent potential targets for macrophage-directed therapies. In this review, we discuss the evidence for macrophage phenotypic and functional alterations in tissue compartments during the development and progression of chronic liver failure in different aetiologies and highlight the potential of macrophage modulation as a therapeutic strategy for liver disease.

Phenotypic Switch of Human Peritoneal Macrophages during Childhood

INTRODUCTION

 Human peritoneal macrophages are resident in the abdominal cavity where they support the specific microenvironmental regulation. We have previously observed a phenotypic switch of murine macrophages during infancy that was associated with a functional development. To investigate the age related changes in human peritoneal macrophages, we analyzed peritoneal macrophages of children undergoing laparoscopic procedures.

MATERIALS AND METHODS

 Immunologically healthy children who received minimally invasive surgery in our department were included in this study. In all cases, the written consent was obtained. At the beginning of laparoscopy, physiologic NaCl-solution was instilled and manually removed through the umbilical trocar to gain macrophages. Lavage cells were processed for flow cytometry analysis. CD14+ myeloid cells were monitored for specific lineage marker expression.

RESULTS

 A total of 21 donors (age: 7 days-18 years) were included and divided into three groups. In all age groups, 97% of myeloid cells expressed CD11b. 70% of these expressed CD14. Three subsets of CD14 cells were detected on the basis of CD14/CD16 expression (CD14 + CD16dim, CD14 + CD16inter, and CD14 + CD16high). In neonates, >80% belonged to the CD14 + CD16high subset, reducing to 30% in adolescents. In none of the cases, the M2 markers CD23 and CD25 were expressed.

CONCLUSION

 This is the first study showing that lineage marker expression of peritoneal macrophages in neonates differs from that in adults. The knowledge about neonatal tissue resident macrophages might help to understand their complex interaction and to use specific macrophage properties for therapeutic approaches.

Brassica Bioactives Could Ameliorate the Chronic Inflammatory Condition of Endometriosis

Endometriosis is a chronic, inflammatory, hormone-dependent disease characterized by histological lesions produced by the presence of endometrial tissue outside the uterine cavity. Despite the fact that an estimated 176 million women are affected worldwide by this gynecological disorder, risk factors that cause endometriosis have not been properly defined and current treatments are not efficient. Although the interaction between diet and human health has been the focus of many studies, little information about the correlation of foods and their bioactive derivates with endometriosis is available. In this framework, Brassica crops have emerged as potential candidates for ameliorating the chronic inflammatory condition of endometriosis, due to their abundant content of health-promoting compounds such as glucosinolates and their hydrolysis products, isothiocyanates. Several inflammation-related signaling pathways have been included among the known targets of isothiocyanates, but those involving aquaporin water channels have an important role in endometriosis. Therefore, the aim of this review is to highlight the promising effects of the phytochemicals present in Brassica spp. as major candidates for inclusion in a dietary approach aiming to improve the inflammatory condition of women affected with endometriosis. This review points out the potential roles of glucosinolates and isothiocyanates from Brassicas as anti-inflammatory compounds, which might contribute to a reduction in endometriosis symptoms. In view of these promising results, further investigation of the effect of glucosinolates on chronic inflammatory diseases, either as diet coadjuvants or as therapeutic molecules, should be performed. In addition, we highlight the involvement of aquaporins in the maintenance of immune homeostasis. In brief, glucosinolates and the modulation of cellular water by aquaporins could shed light on new approaches to improve the quality of life for women with endometriosis.