Peripheral Monocytes from Crohn's Disease Patients Retain Functional Responsiveness to GM-CSF during Active Disease

Paul Peter Winkel¹Wendy Bergmann-Ewert²Johannes Reiner³Astrid Huth³Dana Kleimeier⁴Rosaely Casalegno Garduño⁵Ida Maria Wrobel⁶Grazyna Domanska⁷Jan Däbritz^8*Elisa Wirthgen^9*

• ¹Rostock Medical School, Universitat Rostock, Rostock, Germany
• ²Core Facility for Cell Sorting and Cell Analysis, Universitatsmedizin Rostock, Rostock, Germany
• ³Division of Gastroenterology, Department of Medicine II, Universitatsmedizin Rostock, Rostock, Germany
• ⁴Department of Anesthesia, Critical Care, Emergency and Pain Medicine, Universitatsmedizin Greifswald, Greifswald, Germany
• ⁵Institute of Experimental Gene Therapy & Cancer Research, Universitatsmedizin Rostock, Rostock, Germany
• ⁶Department of Transfusion Medicine, Universitatsmedizin Rostock, Rostock, Germany
• ⁷Department of Immunology, Universitatsmedizin Greifswald, Greifswald, Germany
• ⁸German Centre for Child and Adolescent Health (DZKJ), Site Greifswald/Rostock, Universitatsmedizin Greifswald, Greifswald, Germany
• ⁹Zittau/Görlitz University of Applied Sciences, Zittau, Germany

Crohn's disease (CD) is a relapsing inflammatory disease for which there is currently no cure. Despite the availability of anti-inflammatory treatments, 30-60% of patients eventually develop resistance, necessitating the development of new therapeutic approaches. Data from colitis models in mice suggest that granulocyte-macrophage colony-stimulating factor (GM-CSF)-activated monocytes (GMaMs) could be a promising cellular therapeutic for CD. However, it remains unclear whether inflammatory mediators, medication, or intrinsic defects impair the functionality of peripheral monocytes in patients with active CD (aCD), potentially affecting their therapeutic efficacy. This study evaluates monocytes from aCD patients and healthy donors (HDs) in terms of in vitro migratory capacity, adherence, metabolic activity, surface markers, and inflammatory response. The GMaM phenotype was characterized by increased metabolic activity, enhanced production of inflammatory cytokines, stronger adhesion, and remodeling of cell surface receptors involved in T-cell activation, compared to naïve monocytes. These findings were comparable between aCD patients and HDs. With a few exceptions, the response of GMaMs to lipopolysaccharides (LPS) was also comparable between aCD patients and HDs and included a significant production of pro-inflammatory and chemotactic cytokines such as interleukin (IL)-8 and monocyte chemotactic protein 1. Both are crucial recruiters of monocytes and neutrophils to sites of inflammation. Monocytes of aCD patients showed an increased IL-10 response to GM-CSF. At the same time, the LPS-induced release of tumor necrosis factor-alpha and interferon-gamma by GMaMs was reduced in aCD patients. However, there is no indication that these features represent a limitation for the intended use as a cellular therapeutic.