Sustained gene delivery from inflammation-responsive anti-inflammatory hydrogels promotes extracellular matrix metabolism balance in degenerative nucleus pulposus

Up-to-date evidence about levels and trends in disease and injury incidence, prevalence, and years lived with disability (YLDs) is an essential input into global, regional, and national health policies. In the Global Burden of Disease Study 2013 (GBD 2013), we estimated these quantities for acute and chronic diseases and injuries for 188 countries between 1990 and 2013.

Hydrogel delivery systems can leverage therapeutically beneficial outcomes of drug delivery and have found clinical use. Hydrogels can provide spatial and temporal control over the release of various therapeutic agents, including small-molecule drugs, macromolecular drugs and cells. Owing to their tunable physical properties, controllable degradability and capability to protect labile drugs from degradation, hydrogels serve as a platform in which various physiochemical interactions with the encapsulated drugs control their release. In this Review, we cover multiscale mechanisms underlying the design of hydrogel drug delivery systems, focusing on physical and chemical properties of the hydrogel network and the hydrogel-drug interactions across the network, mesh, and molecular (or atomistic) scales. We discuss how different mechanisms interact and can be integrated to exert fine control in time and space over the drug presentation. We also collect experimental release data from the literature, review clinical translation to date of these systems, and present quantitative comparisons between different systems to provide guidelines for the rational design of hydrogel delivery systems.

Since their serendipitous discovery in nematodes, microRNAs (miRNAs) have emerged as key regulators of biological processes in animals. These small RNAs form complex regulatory networks in cell development, differentiation and homeostasis. Deregulation of miRNA function is associated with an increasing number of human diseases, particularly cancer. Recent discoveries have expanded our understanding of how miRNAs are regulated. Here we review the mechanisms that modulate miRNA activity, their stability and their localization through alternative processing, sequence editing, post-translational modifications of Argonaute proteins, viral factors, transport from the cytoplasm and regulation of miRNA–target interactions. We conclude by discussing intriguing open questions to be answered by future research.