Developing strategies to regulate the immune response poses significant challenges with respect to the clinical translation of tissue-engineered scaffolds. Prominent advancements have been made relating to macrophage-based therapies and biomaterials. Macrophages exhibit the potential to influence healing trajectory, and predominance of particular subtypes during early onset of healing influences repair outcomes. This study evaluated short- and long-term healing response and postoperative mechanical properties of genipin-cross-linked, electrochemically aligned collagen biotextiles with comparative administration of M0, M1, and M2 subtypes. Irrespective of macrophage subtype seeded, all the groups demonstrated existence of M2 macrophages at both time points as typified by arginase and Ym-1 expressions, and distinct absence of M1 macrophages, as indicated by lack of inducible nitric oxide synthase (iNOS) and interleukin-1β expression in all the groups for both time points. M2 macrophage-seeded collagen biotextiles revealed promising host tissue responses, such as reduced fibrous capsule thickness and minimal granulation tissue formation. Furthermore, the M2-seeded group displayed more abundant interstitial collagen deposition following degradation of the collagen threads. M2 macrophage supplementation improved structural and mechanical properties at the tissue and cellular level as indicated by increased modulus and stiffness. This study demonstrates improved biomechanical and histological outcomes following incorporation of M2 macrophages into genipin-cross-linked collagen biotextiles for tissue repair and offers future strategies focused on connective tissue regeneration. Impact statement Macrophages exhibit significant plasticity with complex phenotypes ranging from proinflammatory (M1) to proregenerative (M2). They release cytokines and chemokines governing immunological stability, inflammation resolution, and tissue healing and regeneration. However, utilization of macrophages as therapeutic tools for tissue engineering remains limited. In this study, genipin-cross-linked collagen biotextiles were employed to deliver M0, M1, and M2 macrophages and evaluate tissue responses and postsurgical mechanical properties in vivo. M2-seeded collagen biotextiles showed reduced fibrous capsule and favorable healing response. These outcomes shed new light on designing tissue-engineered constructs that offer a novel cell-based therapeutic approach for applications requiring structural augmentation.
Keywords: M1/M2; collagen; genipin; macrophages; tissue regeneration.