Dysfunctional endothelium contributes to more diseases than any other tissue in the body. Small interfering RNAs (siRNAs) can help in the study and treatment of endothelial cells in vivo by durably silencing multiple genes simultaneously, but efficient siRNA delivery has so far remained challenging. Here, we show that polymeric nanoparticles made of low-molecular-weight polyamines and lipids can deliver siRNA to endothelial cells with high efficiency, thereby facilitating the simultaneous silencing of multiple endothelial genes in vivo. Unlike lipid or lipid-like nanoparticles, this formulation does not significantly reduce gene expression in hepatocytes or immune cells even at the dosage necessary for endothelial gene silencing. These nanoparticles mediate the most durable non-liver silencing reported so far and facilitate the delivery of siRNAs that modify endothelial function in mouse models of vascular permeability, emphysema, primary tumour growth and metastasis.

Rationale:: Macrophages reside in the healthy myocardium, participate in ischemic heart disease, and modulate myocardial infarction (MI) healing. Their origin and roles in post-MI remodeling of nonischemic remote myocardium, however, remain unclear. Objective:: This study investigated the number, origin, phenotype, and function of remote cardiac macrophages residing in the nonischemic myocardium in mice with chronic heart failure after coronary ligation. Methods and Results:: Eight weeks post MI, fate mapping and flow cytometry revealed that a 2.9-fold increase in remote macrophages results from both increased local macrophage proliferation and monocyte recruitment. Heart failure produced by extensive MI, through activation of the sympathetic nervous system, expanded medullary and extramedullary hematopoiesis. Circulating Ly6C ^high monocytes rose from 64±5 to 108±9 per microliter of blood ( P <0.05). Cardiac monocyte recruitment declined in Ccr2 ^−/− mice, reducing macrophage numbers in the failing myocardium. Mechanical strain of primary murine and human macrophage cultures promoted cell cycle entry, suggesting that the increased wall tension in post-MI heart failure stimulates local macrophage proliferation. Strained cells activated the mitogen-activated protein kinase pathway, whereas specific inhibitors of this pathway reduced macrophage proliferation in strained cell cultures and in the failing myocardium ( P <0.05). Steady-state cardiac macrophages, monocyte-derived macrophages, and locally sourced macrophages isolated from failing myocardium expressed different genes in a pattern distinct from the M1/M2 macrophage polarization paradigm. In vivo silencing of endothelial cell adhesion molecules curbed post-MI monocyte recruitment to the remote myocardium and preserved ejection fraction (27.4±2.4 versus 19.1±2%; P <0.05). Conclusions:: Myocardial failure is influenced by an altered myeloid cell repertoire.

Significance: To respond better to evolving pathogens, sudden outbreaks, and individual patient needs, a flexible, safe, and efficient vaccine platform amenable to rapid production near the point of care is required. To this end, we created a fully synthetic, single-dose, adjuvant-free nanoparticle vaccine platform wherein modified dendrimer molecules nanoencapsulate antigen-expressing replicon mRNAs. Vaccines can be multiplexed and formed with multiple antigen-expressing replicons. After a single immunization, the rapid-production, contaminant-free vaccines elicit vital CD8 ⁺ T-cell and antibody responses that fully protect against lethal exposures to several deadly pathogens, including Ebola virus, H1N1 influenza, and Toxoplasma gondii . We believe this technology may allow for rapid-response vaccines with broad efficacy that reduce the number and frequency of vaccinations, and healthcare worker burden.

Scaffolds have been broadly applied within tissue engineering and regenerative medicine to regenerate, replace, or augment diseased or damaged tissue. For a scaffold to perform optimally, several design considerations must be addressed, with an eye toward the eventual form, function, and tissue site. The chemical and mechanical properties of the scaffold must be tuned to optimize the interaction with cells and surrounding tissues. For complex tissue engineering, mass transport limitations, vascularization, and host tissue integration are important considerations. As the tissue architecture to be replaced becomes more complex and hierarchical, scaffold design must also match this complexity to recapitulate a functioning tissue. We outline these design constraints and highlight creative and emerging strategies to overcome limitations and modulate scaffold properties for optimal regeneration. We also highlight some of the most advanced strategies that have seen clinical application and discuss the hurdles that must be overcome for clinical use and commercialization of tissue engineering technologies. Finally, we provide a perspective on the future of scaffolds as a functional contributor to advancing tissue engineering and regenerative medicine.

MicroRNAs (miRNAs) and siRNAs have enormous potential as cancer therapeutics, but their effective delivery to most solid tumors has been difficult. Here, we show that a new lung-targeting nanoparticle is capable of delivering miRNA mimics and siRNAs to lung adenocarcinoma cells in vitro and to tumors in a genetically engineered mouse model of lung cancer based on activation of oncogenic Kirsten rat sarcoma viral oncogene homolog (Kras) and loss of p53 function. Therapeutic delivery of miR-34a, a p53-regulated tumor suppressor miRNA, restored miR-34a levels in lung tumors, specifically down-regulated miR-34a target genes, and slowed tumor growth. The delivery of siRNAs targeting Kras reduced Kras gene expression and MAPK signaling, increased apoptosis, and inhibited tumor growth. The combination of miR-34a and siRNA targeting Kras improved therapeutic responses over those observed with either small RNA alone, leading to tumor regression. Furthermore, nanoparticle-mediated small RNA delivery plus conventional, cisplatin-based chemotherapy prolonged survival in this model compared with chemotherapy alone. These findings demonstrate that RNA combination therapy is possible in an autochthonous model of lung cancer and provide preclinical support for the use of small RNA therapies in patients who have cancer. Significance Small RNAs can potently and precisely regulate gene expression; as a result, they have tremendous clinical potential. However, effective delivery of small RNAs to solid tumors has remained challenging. Here we report that a lipid/polymer nanoparticle can deliver small RNAs to treat autochthonous tumors in the so-called “KP” mouse model of lung cancer. Nanoparticles formulated with mimics of the p53-regulated miRNA miR-34a downregulated target genes and delayed tumor progression, while nanoparticles formulated with siRNA targeting Kirsten rat sarcoma viral oncogene homolog (siKras) slowed tumor growth and increased apoptosis. Notably, concurrent delivery of miR-34a and siKras increased anti-tumor effects, and led to tumor regression. These results demonstrate that small RNA therapies can impact solid lung tumor growth, and that targeted RNA combination therapies may be used to improve therapeutic response.

Myocardial infarction (MI) leads to a systemic surge of vascular inflammation in mice and humans, resulting in secondary ischemic complications and high mortality. We show that, in ApoE^−/− mice with coronary ligation, increased sympathetic tone up-regulates not only hematopoietic leukocyte production but also plaque endothelial expression of adhesion molecules. To counteract the resulting arterial leukocyte recruitment, we developed nanoparticle-based RNA interference (RNAi) that effectively silences five key adhesion molecules. Simultaneously encapsulating small interfering RNA (siRNA)–targeting intercellular cell adhesion molecules 1 and 2 (Icam1 and Icam2), vascular cell adhesion molecule 1 (Vcam1), and E- and P-selectins (Sele and Selp) into polymeric endothelial-avid nanoparticles reduced post-MI neutrophil and monocyte recruitment into atherosclerotic lesions and decreased matrix-degrading plaque protease activity. Five-gene combination RNAi also curtailed leukocyte recruitment to ischemic myocardium. Therefore, targeted multigene silencing may prevent complications after acute MI.