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.

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.