In the liver of obese animals, endoplasmic reticulum (ER) structure is altered, resulting in a higher number of contact sites between ER and mitochondria (Mitochondria Associated Membranes, MAMs). In this issue, Arruda et al. (p 1427) report that heightened MAM formation results in mitochondrial calcium overload, compromised mitochondrial oxidative capacity and oxidative stress. Image depicts a transmission electron micrograph of a hepatocyte within the liver of an obese (ob/ob) mouse, which displays ER wrapped around mitochondria with ultrastructural alterations. Original image captured by Ana Paula Arruda.

Pluripotent stem cells can be differentiated in vitro to form immature human intestinal organoids. In this issue, Michael Helmrath and his colleagues report that these organoids engraft in vivo to form mature and functional small intestine. The cover image, courtesy of Carey Watson (Cincinnati Children's Hospital Medical Center), depicts pluripotent stem cell–generated human small intestine engrafted under the mouse kidney capsule, with human intestinal DNA (pink), total DNA (blue), smooth muscle (green) and recipient's kidney (red).

Transient inhibition of JAK-STAT signaling drives proliferation of satellite cells and promotes repair of aged, injured and dystrophic muscle in mice (pp 1094, 1174 and 1182). The original immunofluorescence image shows mouse skeletal muscle regeneration. Original image by Anastasia Gromova. Artwork by Matt Hansen.

Alopecia areata is an autoimmune disease characterized by immune-mediated attack of the hair follicle and hair loss. In this issue, Xing et al. find that cytotoxic T cells are necessary and sufficient for the development of alopecia areata in mice. Inhibition of interferon and common gamma chain cytokines or administration of JAK inhibitors prevent the development of disease, whereas JAK inhibitors promote hair regrowth in patients and mice with established disease. The cover image depicts IL-15 (green), IL-15 receptor α (red) and nuclei (DAPI, blue) in a skin resident-hair bulb from a patient with alopecia areata. Image courtesy of the Christiano and Clynes laboratories, Columbia University.

This month Nature Medicine features a collection of articles focusing on regenerative medicine (pp 814–880). Cover image: "My Life as a Hill" by Pamela Goode

Neisseria meningitidis infection that enters the bloodstream can cause potentially fatal meningitis and septic shock. The host cell receptor that enables its adhesion to blood vessels and subsequent vascular colonization is not known. In this issue, Bernard et al. identify CD147 as an endothelial cell receptor that mediates meningococcal adhesion to and colonization of human blood vessels (p 725). The cover image depicts N. meningitidis (pink) colonizing human blood vessels (basal lamina collagen IV, green, and actin, blue) in human skin grafted onto a mouse. Image courtesy of Sandrine Bourdoulous, Institut Cochin.

Systemic exposure to the blood of young mice improves synaptic plasticity and cognitive function in aged mice. Villeda, Wyss-Coray and their colleagues demonstrate these effects using parabiosis as well as systemic injection of plasma from young mice (p 659). Additional work is needed to determine if similar findings apply in humans. Credit © Charicio/Alamy

A potential treatment for Huntington's disease involves reducing expression of the mutant gene. In this issue, X William Yang and his colleagues determine to which parts of the mouse brain the treatment should be directed for maximum benefit (p 536). The cover image (courtesy of the authors) demonstrates labeling of the cortex (green) and striatum (purple) and of neurons throughout the brain (red).

Kindler syndrome (KS) is a skin blister disease associated with an increased risk for skin cancer. In this issue, Reinhard Fässler and his colleagues have developed a new mouse model of KS, which allowed them to uncover new insight into the mechanisms of the disease (p 350). The cover image (courtesy of the authors) shows ectopic hair follicles with enlarged hair follicle bulges (red) and small hair germs (green) in the tail skin of a mouse lacking Kindlin-1 (nuclei in blue).

Large-scale visualization labs allow scientists to virtually walk through their data sets. A News Feature on page 228 explores how these immersive environments are advancing biomedicine. The cover shows a researcher looking at fiber tracts of the brain’s white matter that have been color-coded by their primary direction. Photo by Dyani Lewis.

In this issue (p 159), Benjamin Marsland and his colleagues show that the gut microbiota can influence allergic airway disease through the metabolism of dietary fiber. Cover image: Tim Gainey / Alamy.

Following transmission by mosquito bite, the Plasmodium parasite infects the liver, where it differentiates and proliferates but is clinically undetectable. In this issue, Maria Mota and her colleagues report that the parasite is nevertheless detected by cells in the liver, triggering an interferon response that restrains the parasite load (p 47). The cover image, courtesy of Peter Liehl, depicts mouse liver cells (red), the Plasmodium parasite (green) and DNA (blue).