Donor Heterogeneity in the Human Macrophage Response to a Biomaterial Under Hyperglycemia In Vitro

Macrophages have a commanding role in scaffold-driven in situ tissue regeneration. Depending on their polarization state, macrophages mediate the formation and remodeling of new tissue by secreting growth factors and cytokines. Therefore, successful outcomes of material-driven in situ tissue vascular tissue engineering depend largely on the immuno-regenerative potential of the recipient. A large cohort of patients requiring vascular replacements suffers from systemic multifactorial diseases, such as diabetes, which gives rise to a hyperglycemic and aggressive oxidative inflammatory environment that is hypothesized to hamper a well-balanced regenerative process. Here, we aimed at fundamentally exploring the effects of hyperglycemia, as one of the hallmarks of diabetes, on the macrophage response to three-dimensional (3D) electrospun synthetic biomaterials for in situ tissue engineering, in terms of inflammatory profile and tissue regenerative capacity. To simulate the early phases of the in situ regenerative cascade, we used a bottom-up in vitro approach. Primary human macrophages ( n = 8 donors) were seeded in two-dimensional (2D) culture wells and polarized to pro-inflammatory M1 and anti-inflammatory M2 phenotype in normoglycemic (5.5 mM glucose), hyperglycemic (25 mM), and osmotic control (OC) conditions (5.5 mM glucose, 19.5 mM mannitol). Unpolarized macrophages and (myo)fibroblasts were seeded in mono- or co-culture in a 3D electrospun resorbable polycaprolactone bisurea scaffold and exposed to normoglycemic, hyperglycemic, and OC conditions. The results showed that macrophage polarization by biochemical stimuli was effective under all glycemic conditions and that the polarization states dictated expression of the receptors SCL2A1 (glucose transporter 1) and CD36 (fatty acid transporter). In 3D, the macrophage response to hyperglycemic conditions was strongly donor-dependent in terms of phenotype, cytokine secretion profile, and metabolic receptor expression. When co-cultured with (myo)fibroblasts, hyperglycemic conditions led to an increased expression of fibrogenic markers ( ACTA2, COL1, COL3, IL-1β). Together, these findings show that the hyperglycemic and hyperosmotic conditions may, indeed, influence the process of macrophage-driven in situ tissue engineering, and that the extent of this is likely to be patient-specific.