Understanding the origin of myofibroblasts in kidney is of great interest because these cells are responsible for scar formation in fibrotic kidney disease. Recent studies suggest epithelial cells are an important source of myofibroblasts through a process described as the epithelial-to-mesenchymal transition; however , confirmatory studies in vivo are lacking. To quantitatively assess the contribution of renal epithelial cells to myofibroblasts , we used Cre/Lox techniques to genetically label and fate map renal epithelia in models of kidney fibrosis. Genetically labeled primary proximal epithelial cells cultured in vitro from these mice readily induce markers of myofibroblasts after transforming growth factor ␤ 1 treatment. However , using either red fluorescent protein or ␤-galactosidase as fate markers , we found no evidence that epithelial cells migrate outside of the tubular basement membrane and differentiate into interstitial myofibroblasts in vivo. Thus , although renal epithelial cells can acquire mesenchymal markers in vitro, they do not directly contribute to interstitial myofibroblast cells in vivo. Lineage analysis shows that during nephrogenesis , FoxD1-positive( ؉ ) mesenchymal cells give rise to adult CD73 ؉ , platelet derived growth factor receptor ␤ ؉ , smooth muscle actin-negative interstitial pericytes , and these FoxD1-derivative interstitial cells expand and differentiate into smooth muscle actin ؉ myofibroblasts during fibrosis, accounting for a large majority of myofibroblasts. These data indicate that therapeutic strategies directly targeting pericyte differentiation in vivo may productively impact fibrotic kidney disease. (Am J Pathol

Macrophages are required for tissue homeostasis through their role in regulation of the immune response and the resolution of injury. Here we show, using the kidney as a model, that the Wnt pathway ligand Wnt7b is produced by macrophages to stimulate repair and regeneration. When macrophages are inducibly ablated from the injured kidney, the canonical Wnt pathway response in kidney epithelial cells is reduced. Furthermore, when Wnt7b is somatically deleted in macrophages, repair of injury is greatly diminished. Finally, injection of the Wnt pathway regulator Dkk2 enhances the repair process and suggests a therapeutic option. Because Wnt7b is known to stimulate epithelial responses during kidney development, these findings suggest that macrophages are able to rapidly invade an injured tissue and reestablish a developmental program that is beneficial for repair and regeneration.

SummaryIterative liver injury results in progressive fibrosis disrupting hepatic architecture, regeneration potential, and liver function. Hepatic stellate cells (HSCs) are a major source of pathological matrix during fibrosis and are thought to be a functionally homogeneous population. Here, we use single-cell RNA sequencing to deconvolve the hepatic mesenchyme in healthy and fibrotic mouse liver, revealing spatial zonation of HSCs across the hepatic lobule. Furthermore, we show that HSCs partition into topographically diametric lobule regions, designated portal vein-associated HSCs (PaHSCs) and central vein-associated HSCs (CaHSCs). Importantly we uncover functional zonation, identifying CaHSCs as the dominant pathogenic collagen-producing cells in a mouse model of centrilobular fibrosis. Finally, we identify LPAR1 as a therapeutic target on collagen-producing CaHSCs, demonstrating that blockade of LPAR1 inhibits liver fibrosis in a rodent NASH model. Taken together, our work illustrates the power of single-cell transcriptomics to resolve the key collagen-producing cells driving liver fibrosis with high precision.

Intratumoral (IT) STING activation results in tumor regression in preclinical models, yet factors dictating the balance between innate and adaptive anti-tumor immunity are unclear. Here, clinical candidate STING agonist ADU-S100 (S100) is used in an IT dosing regimen optimized for adaptive immunity to uncover requirements for a T cell-driven response compatible with checkpoint inhibitors (CPIs). In contrast to highdose tumor ablative regimens that result in systemic S100 distribution, low-dose immunogenic regimens induce local activation of tumor-specific CD8 + effector T cells that are responsible for durable anti-tumor immunity and can be enhanced with CPIs. Both hematopoietic cell STING expression and signaling through IFNAR are required for tumor-specific T cell activation, and in the context of optimized T cell responses, TNFa is dispensable for tumor control. In a poorly immunogenic model, S100 combined with CPIs generates a survival benefit and durable protection. These results provide fundamental mechanistic insights into STING-induced anti-tumor immunity.

Background-Understanding the mechanisms of repair and regeneration of the kidney after injury is of great interest because there are currently no therapies that promote repair, and kidneys frequently do not repair adequately. We studied the capacity of human CD34 ϩ hematopoietic stem/progenitor cells (HSPCs) to promote kidney repair and regeneration using an established ischemia/reperfusion injury model in mice, with particular focus on the microvasculature. Methods and Results-Human HSPCs administered systemically 24 hours after kidney injury were selectively recruited to injured kidneys of immunodeficient mice (Jackson Labs, Bar Harbor, Me) and localized prominently in and around vasculature. This recruitment was associated with enhanced repair of the kidney microvasculature, tubule epithelial cells, enhanced functional recovery, and increased survival. HSPCs recruited to kidney expressed markers consistent with circulating endothelial progenitors and synthesized high levels of proangiogenic cytokines, which promoted proliferation of both endothelial and epithelial cells. Although purified HSPCs acquired endothelial progenitor markers once recruited to the kidney, engraftment of human endothelial cells in the mouse capillary walls was an extremely rare event, indicating that human stem cell mediated renal repair is by paracrine mechanisms rather than replacement of vasculature. Conclusions-These studies advance human HSPCs as a promising therapeutic strategy for promoting renal repair after injury. (Circulation. 2010;121:2211-2220.)

In the originally published version of this article, the 4T1 tumor cell line described in Figures 1, 2, and 5 and Supplemental Figures S1, S2, and S5 was mis-identified. This cell line has since been identified via short tandem repeat analysis as the murine CT26 tumor cell line, which is an undifferentiated colon carcinoma cell line. Furthermore, the line that was used had been engineered to express the human mesothelin protein. The authors believe that the substance and interpretation of the experiments put forth in the article remain the same. The online article, Figures 2 and S1, and the Supplemental Information have been updated to reflect the correction.

Kidney damage due to injury rarely resolves completely, and there are currently no therapies capable of promoting repair. In addition to understanding mechanisms by which tissues are damaged, illuminating mechanisms of repair and regeneration is also of great importance. Here we show that the melanoma-associated, transmembrane glycoprotein, Gpnmb, is up-regulated 15-fold following ischemic damage in kidney tissue and by more than 10-fold in macrophages and 3-fold in surviving epithelial cells. Gpnmb-expressing macrophages and epithelial cells were found to contain apoptotic bodies at 3 times the rate of nonexpressing cells. Either mutation of Gpnmb or ablation of inflammatory macrophages prevents normal repair of the kidney. Significantly, the kidneys from postischemic Gpnmb mutant mice exhibited a 5-fold increase in apoptotic cellular debris compared to wild-type mice. These mice also experienced an 85% increase in mortality following bilateral ischemic kidney. Finally, we demonstrate that Gpnmb is a phagocytic protein that is necessary for recruitment of the autophagy protein LC3 to the phagosome where these proteins are colocalized and for lysosomal fusion with the phagosome and hence bulk degradation of their content. Therefore, Gpnmb is a novel prorepair gene that is necessary for crosstalk between the macroautophagic degradation pathway and phagocytosis.

Abstract.We investigate the stability of Bravais lattices and their Cauchy-Born approximations under periodic perturbations. We formulate a general interaction law and derive its Cauchy-Born continuum limit. We then analyze the atomistic and Cauchy-Born stability regions, that is, the sets of all matrices that describe a stable Bravais lattice in the atomistic and Cauchy-Born models respectively. Motivated by recent results in one dimension on the stability of atomistic/continuum coupling methods, we analyze the relationship between atomistic and Cauchy-Born stability regions, and the convergence of atomistic stability regions as the cell size tends to infinity.Mathematics Subject Classification. 35Q74, 49K40, 65N25, 70J25, 70C20.