Fractionation of an ECM hydrogel into structural and soluble components reveals distinctive roles in regulating macrophage behavior

Abstract

Extracellular matrix (ECM) derived from mammalian tissues has been utilized to repair damaged or missing tissue and improve healing outcomes. More recently, processing of ECM into hydrogels has expanded the use of these materials to include platforms for 3-dimensional cell culture as well as injectable therapeutics that can be delivered by minimally invasive techniques and fill irregularly shaped cavities. At the cellular level, ECM hydrogels initiate a multifaceted host response that includes recruitment of endogenous stem/progenitor cells, regional angiogenesis, and modulation of the innate immune response. Unfortunately, little is known about the components of the hydrogel that drive these responses. We hypothesized that different components of ECM hydrogels could play distinctive roles in stem cell and macrophage behavior. Utilizing a well-characterized ECM hydrogel derived from urinary bladder matrix (UBM), we separated the soluble and structural components of UBM hydrogel and characterized their biological activity. Perivascular stem cells migrated toward and reduced their proliferation in response to both structural and soluble components of UBM hydrogel. Both components also altered macrophage behavior but with different fingerprints. Soluble components increased phagocytosis with an IL-1RA(high), TNFα(low), IL-1β(low), uPA(low) secretion profile. Structural components decreased phagocytosis with a PGE2(high), PGF2α(high), TNFα(low), IL-1β(low), uPA(low), MMP2(low), MMP9(low), secretion profile. The biologic activity of the soluble components was mediated by Notch and PI3K/Akt signaling, while the biologic activity of the structural components was mediated by integrins and MEK/ERK signaling. Collectively, these findings demonstrate that soluble and structural components of ECM hydrogels contribute to the host response but through different mechanisms.

Restoring Mucosal Barrier Function and Modifying Macrophage Phenotype with an Extracellular Matrix Hydrogel: Potential Therapy for Ulcerative Colitis

“…Although the signaling molecules that influence macrophage and lymphocyte phenotype transition are not fully understood, there is suggestive evidence that at least some of these regulators reside within the ECM [9,10,25]. Results of the present study suggest that ECMH modulates the innate immune response not by directly promoting an M2-like macrophage phenotype but rather by reducing the number of TNF expressing M1-like proinflammatory macrophages, thus shifting the microenvironmental milieu from inflammation to repair.…”

“…The choice of 8 mg/mL ECMH concentration was based on a hydrogel concentration that supported robust gel formation within 10 minutes of placement within the colon, would adhere to the ulcerated colonic wall for greater than 12 hours, and did not exhibit time-dependent viscosity as was observed in the 12 mg/mL ECMH (Supplemental Figure 2). To examine the effects of ECMH on cell in-vitro, the ECMH concentration had to be reduced to prevent gelation within the cell culture and 500 μg/mL was used based on previous studies [10,14]. 14 C-labeled ECMH was prepared as stated above with the intestines of pigs that were injected with 14 C-tagged proline, as previously described [15].…”

“…Intact and solubilized/hydrogel forms of ECM have been shown to facilitate a rapid and dramatic transition away from an M1-like, pro-inflammatory macrophage phenotype toward an M2-like, pro-healing/regulatory macrophage phenotype [9,10]. Simultaneously, naturally occurring cryptic peptide motifs released or exposed during in-vivo degradation of the ECM material, combined with the secreted products of ECM-exposed alternatively activated macrophages, promote stem/progenitor cell chemotaxis, proliferation, and differentiation [11,12].…”

Injectable Extracellular Matrix Hydrogels as Scaffolds for Spinal Cord Injury Repair

“…15,27 Recent studies describe the M2 polarizing effects of ECM derived from several tissues. 28,29 In the present study, the expression of genes related to both M1 and M2 macrophages decreased at 2 weeks, which reflects that both inflammatory as well as antiinflammatory responses were inhibited after ECM hydrogel treatment. Nevertheless, according to positive staining for CD206, ECM hydrogel treatment led to spatial differences of macrophage distribution within the lesion, where M2 macrophages were mostly accumulated within the hydrogel, and M1 macrophages were in the surrounding tissue.…”

Solubilized extracellular matrix from brain and urinary bladder elicits distinct functional and phenotypic responses in macrophages

“…These soluble forms of ECM afford many advantages including minimally invasive delivery to the site of injury and the ability to fill an irregularly shaped cavity [13e15]. Most importantly, solubilized ECM retains many of the bioactive properties of intact ECM including the ability to modulate macrophage phenotype [16,17].…”