Peptide amphiphile (PA) is a peptide-based biomaterial that can self-assemble into a nanostructured gel-like scaffold, mimicking the chemical and biological complexity of natural extracellular matrix. To evaluate the capacity of the PA scaffold to improve islet function and survival in vitro, rat islets were cultured in three different groups--(1) bare group: isolated rat islets cultured in a 12-well nontissue culture-treated plate; (2) insert group: isolated rat islets cultured in modified insert chambers; (3) nanomatrix group: isolated rat islets encapsulated within the PA nanomatrix gel and cultured in modified insert chambers. Over 14 days, both the bare and insert groups showed a marked decrease in insulin secretion, whereas the nanomatrix group maintained glucose-stimulated insulin secretion. Moreover, entire islets in the nanomatrix gel stained positive for dithizone up to 14 days, indicating better maintained glucose-stimulated insulin production. Fluorescein diacetate/propidium iodide staining results also verified necrosis in the bare and insert groups after 7 days, whereas the PA nanomatrix gel maintained islet viability after 14 days. Thus, these results demonstrate the potential of PAs as an intermediary scaffold for increasing the efficacy of pancreatic islet transplantation.

Understanding the role of the pancreatic extracellular matrix (ECM) in supporting islet survival and function drives the pursuit to create biomaterials that imitate and restore the pancreatic ECM microenvironment. To create an ECM mimic holding bioinductive cues for β-cells, self-assembled peptide amphiphiles (PAs) inscribed with four selected ECM-derived cell adhesive ligands are synthesized. After 7 days, compared to control groups cultured on biologically inert substrates, MIN6 β-cells cultured on PAs functionalized with YIGSR and RGDS cell adhesive ligands exhibit elevated insulin secretion in responses to glucose and also form β-cell clusters. These findings suggest that the self-assembled PA nanomatrix may be utilized to improve pancreatic islet transplantation for treating type 1 diabetes.

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Chronic inflammation contributes significantly to disease progression in heart failure (HF), and is characterized by expansion of activated macrophages, dendritic cells, and T cells in the failing heart. Neutrophils play a well-known role as the initial drivers of inflammatory response to myocardial infarction (MI), thereby providing the platform for the subsequent recruitment of macrophages and T cells. However, whether and how neutrophils contribute to inflammation and adverse LV remodeling in chronic HF are unknown. We tested the hypothesis that activated neutrophils are required for tissue remodeling and disease progression in HF. Male C57Bl/6 mice were studied 4 and 8 weeks after left coronary artery ligation during established ischemic HF (sham-operated controls). As assessed by flow cytometry, CD11b + Ly6G + neutrophils were expanded in the peripheral blood (4 w post-MI), and in the bone marrow, spleen, and heart at 8 w post-MI. Immunostaining revealed that in the failing heart, neutrophils were primarily localized to the MI border zone, but also augmented in remote zone myocardium. CXCL1 and CXCL5 chemokine expression was increased in the failing heart, consistent with chemotactic signals for myocardial neutrophil recruitment. Isolated naïve neutrophils also exhibited increased chemotaxis in response to plasma from HF mice (versus plasma from naïve mice), as assessed by time-lapse video microscopy. Moreover, blood neutrophils isolated from HF mice exhibited significantly increased neutrophil extracellular trap (NET) production as compared to control neutrophils, whereas plasma NETs (histone-DNA complexes) were increased in HF mice. Finally, the in vivo role of neutrophils in chronic HF (8 w post-MI) was determined via depletion studies using genetic (Ly6G-diptheria toxin receptor mice) and antibody (1A8) based approaches. In both models, 2 and 4 w of neutrophil depletion, respectively, significantly improved LV systolic function and reduced end systolic volume. 1A8 treated HF mice also exhibited reduced remote zone fibrosis. We conclude: neutrophil expansion and activation are important components of the chronic inflammatory response in HF, and play an obligatory role in the progression of LV remodeling in ischemic cardiomyopathy.

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