The Human Tissue-Biomaterial Interface: A Role for PPARγ-Dependent Glucocorticoid Receptor Activation in Regulating the CD163(+) M2 Macrophage Phenotype

Samuel J Bullers, Simon C Baker, Eileen Ingham, Jennifer Southgate

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In vivo studies of implanted acellular biological scaffolds in experimental animals have shown constructive remodeling mediated by anti-inflammatory macrophages. Little is known about the human macrophage response to such biomaterials, or the nature of the signaling mechanisms that govern the macrophage phenotype in this environment. The cellular events at the interface of a tissue and implanted decellularized biomaterial were examined by establishing a novel ex vivo tissue culture model in which surgically excised human urinary tract tissue was combined with porcine acellular bladder matrix (PABM). Evaluation of the tissue-biomaterial interface showed a time-dependent infiltration of the biomaterial by CD68(+) CD80(-) macrophages. The migration of CD68(+) cells from the tissue to the interface was accompanied by maturation to a CD163(hi) phenotype, suggesting that factor(s) associated with the biomaterial or the wound edge was/were responsible for the active recruitment and polarization of local macrophages. Glucocorticoid receptor (GR) and peroxisome proliferator activated receptor gamma (PPARγ) signaling was investigated as candidate pathways for integrating inflammatory responses; both showed intense nuclear labeling in interface macrophages. GR and PPARγ activation polarized peripheral blood-derived macrophages from a default M1 (CD80(+)) toward an M2 (CD163(+)) phenotype, but PPARγ signaling predominated, as its antagonism blocked any GR-mediated effect. Seeding on PABM was effective at polarizing peripheral blood-derived macrophages from a default CD80(+) phenotype on glass to a CD80(-) phenotype, with intense nuclear localization of PPARγ. These results endorse in vivo observations that the infiltration of decellularized biological scaffolds, exemplified here by PABM, is pioneered by macrophages. Thus, it appears that natural factors present in PABM are involved in the active recruitment and polarization of macrophages to a CD163(+) phenotype, with activation of PPARγ identified as the candidate pathway. The harnessing of these natural matrix-associated factors may be useful in enhancing the integration of synthetic and other natural biomaterials by polarizing macrophage activation toward an M2 regulatory phenotype.

Original languageEnglish
Pages (from-to)2390-2401
Number of pages12
JournalTissue engineering. Part A
Issue number17-18
Early online date16 May 2014
Publication statusPublished - 11 Sept 2014

Bibliographical note

© 2014 Mary Ann Liebert, Inc. This work is licensed under a Creative Commons Attribution 3.0 United States License. You are free to copy, distribute, transmit and adapt this work, but you must attribute this work as ‘‘Tissue Engineering, Part A. Copyright 2014 Mary Ann Liebert, Inc., used under a Creative Commons Attribution License:’’

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