title: Extended culture of macrophages from different sources and maturation results in a common M2 phenotype.
abstract: Inflammatory responses to biomaterials heavily influence the environment surrounding implanted devices, often producing foreign-body reactions. The macrophage is a key immunomodulatory cell type consistently associated with implanted biomaterials and routinely used in short-term in vitro cell studies of biomaterials aiming to reproduce host responses. Inconsistencies within these studies, including differently sourced cells, different durations of culture, and assessment of different activation markers, lead to many conflicting results in vitro that confound consistency and conclusions. We hypothesize that different experimentally popular monocyte-macrophage cell types have intrinsic in vitro culture-specific differences that yield conflicting results. Recent studies demonstrate changes in cultured macrophage cytokine expression over time, leading to the hypothesis that changes in macrophage phenotype also occur in response to extended culture. Here, macrophage cells of different transformed and primary-derived origins were cultured for 21 days on model polymer biomaterials. Cell type-based differences in morphology and cytokine/chemokine expression as well as changes in cell surface biomarkers associated with differentiation stage, activation state, and adhesion were compared. Results reflect consistent macrophage development toward an M2 phenotype via up-regulation of the macrophage mannose receptor for all cell types following 21-day extended culture. Significantly, implanted biomaterials experiencing the foreign-body response and encapsulation in vivo often elicit a shift toward an analogous M2 macrophage phenotype. In vitro "default" of macrophage cultures, regardless of lineage, to this M2 state in the presence of biomaterials at long culture periods is not recognized, but has important implications to in vitro modeling of in vivo host response.
authors: Cell and Molecular Biology Program, Colorado State University, Fort Collins, Colorado, 80523.|Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah, 84112-5820.
authors: Lisa M
authors: LM
authors: Chamberlain
authors: Department of Bioengineering, University of Utah, Salt Lake City, Utah, 84112-5820.
authors: Dolly
authors: D
authors: Holt-Casper
authors: Cell and Molecular Biology Program, Colorado State University, Fort Collins, Colorado, 80523.|Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, 80523.
authors: Mercedes
authors: M
authors: Gonzalez-Juarrero
authors: Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah, 84112-5820.|Department of Bioengineering, University of Utah, Salt Lake City, Utah, 84112-5820.
authors: David W
authors: DW
authors: Grainger
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000009:adverse effects* / Q000737:chemistry; D002452:Cell Count; D018929:Cell Culture Techniques / Q000379:methods*; D002454:Cell Differentiation; D002460:Cell Line; D048430:Cell Shape; D016207:Cytokines / Q000378:metabolism; D005549:Foreign-Body Reaction / Q000276:immunology; D008262:Macrophage Activation; D008264:Macrophages / Q000145:classification / Q000166:cytology* / Q000276:immunology; D008422:Materials Testing; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D013499:Surface Properties; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D016207:Cytokines
keywords: biocompatibility; cell activation; cell culture; cytokine; foreign-body response; in vitro; inflammatory phenotype