Single-cell RNA sequencing reveals the mesangial identity and species diversity of glomerular cell transcriptomes.

Molecular characterization of the individual cell types in human kidney as well as model organisms are critical in defining organ function and understanding translational aspects of biomedical research. Previous studies have uncovered gene expression profiles of several kidney glomerular cell types, however, important cells, including mesangial (MCs) and glomerular parietal epithelial cells (PECs), are missing or incompletely described, and a systematic comparison between mouse and human kidney is lacking. To this end, we use Smart-seq2 to profile 4332 individual glomerulus-associated cells isolated from human living donor renal biopsies and mouse kidney. The analysis reveals genetic programs for all four glomerular cell types (podocytes, glomerular endothelial cells, MCs and PECs) as well as rare glomerulus-associated macula densa cells. Importantly, we detect heterogeneity in glomerulus-associated Pdgfrb-expressing cells, including bona fide intraglomerular MCs with the functionally active phagocytic molecular machinery, as well as a unique mural cell type located in the central stalk region of the glomerulus tuft. Furthermore, we observe remarkable species differences in the individual gene expression profiles of defined glomerular cell types that highlight translational challenges in the field and provide a guide to design translational studies.

Systems pharmacology-based integration of human and mouse data for drug repurposing to treat thoracic aneurysms.

Marfan syndrome (MFS) is associated with mutations in fibrillin-1 that predispose afflicted individuals to progressive thoracic aortic aneurysm (TAA) leading to dissection and rupture of the vessel wall. Here we combined computational and experimental approaches to identify and test FDA-approved drugs that may slow or even halt aneurysm progression. Computational analyses of transcriptomic data derived from the aortas of MFS patients and MFS mice (Fbn1mgR/mgR mice) predicted that subcellular pathways associated with reduced muscle contractility are key TAA determinants that could be targeted with the GABAB receptor agonist baclofen. Systemic administration of baclofen to Fbn1mgR/mgR mice validated our computational prediction by mitigating arterial disease progression at the cellular and physiological levels. Interestingly, baclofen improved muscle contraction-related subcellular pathways by upregulating a different set of genes than those downregulated in the aorta of vehicle-treated Fbn1mgR/mgR mice. Distinct transcriptomic profiles were also associated with drug-treated MFS and wild-type mice. Thus, systems pharmacology approaches that compare patient- and mouse-derived transcriptomic data for subcellular pathway-based drug repurposing represent an effective strategy to identify potential new treatments of human diseases.

Control of cell-cell forces and collective cell dynamics by the intercellular adhesome.

Dynamics of epithelial tissues determine key processes in development, tissue healing and cancer invasion. These processes are critically influenced by cell-cell adhesion forces. However, the identity of the proteins that resist and transmit forces at cell-cell junctions remains unclear, and how these proteins control tissue dynamics is largely unknown. Here we provide a systematic study of the interplay between cell-cell adhesion proteins, intercellular forces and epithelial tissue dynamics. We show that collective cellular responses to selective perturbations of the intercellular adhesome conform to three mechanical phenotypes. These phenotypes are controlled by different molecular modules and characterized by distinct relationships between cellular kinematics and intercellular forces. We show that these forces and their rates can be predicted by the concentrations of cadherins and catenins. Unexpectedly, we identified different mechanical roles for P-cadherin and E-cadherin; whereas P-cadherin predicts levels of intercellular force, E-cadherin predicts the rate at which intercellular force builds up.

Improved rat steatotic and nonsteatotic liver preservation by the addition of epidermal growth factor and insulin-like growth factor-I to University of Wisconsin solution.

This study examined the effects of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) supplementation to University of Wisconsin solution (UW) in steatotic and nonsteatotic livers during cold storage. Hepatic injury and function were evaluated in livers preserved for 24 hours at 4 degrees C in UW and in UW with EGF and IGF-I (separately or in combination) and then perfused ex vivo for 2 hours at 37 degrees C. AKT was inhibited pharmacologically. In addition, hepatic injury and survival were evaluated in recipients who underwent transplantation with steatotic and nonsteatotic livers preserved for 6 hours in UW and UW with EGF and IGF-I (separately or in combination). The results, based on isolated perfused liver, indicated that the addition of EGF and IGF-I (separately or in combination) to UW reduced hepatic injury and improved function in both liver types. A combination of EGF and IGF-I resulted in hepatic injury and function parameters in both liver types similar to those obtained by EGF and IGF-I separately. EGF increased IGF-I, and both additives up-regulated AKT in both liver types. This was associated with glycogen synthase kinase-3beta (GSK3(beta)) inhibition in nonsteatotic livers and PPAR gamma overexpression in steatotic livers. When AKT was inhibited, the effects of EGF and IGF-I on GSK3(beta), PPAR gamma, hepatic injury and function disappeared. The benefits of EGF and IGF-I as additives in UW solution were also clearly seen in the liver transplantation model, because the presence of EGF and IGF-I (separately or in combination) in UW solution reduced hepatic injury and improved survival in recipients who underwent transplantation with steatotic and nonsteatotic liver grafts. In conclusion, EGF and IGF-I may constitute new additives to UW solution in steatotic and nonsteatotic liver preservation, whereas a combination of both seems unnecessary.

Insulin-like growth factor and epidermal growth factor treatment: new approaches to protecting steatotic livers against ischemia-reperfusion injury.

Hepatic steatosis is a major risk factor in ischemia-reperfusion (I/R). IGF-binding proteins (IGFBPs) modulate IGF-I action by transporting circulating IGF-I to its sites of action. Epidermal growth factor (EGF) stimulates IGF-I synthesis in vitro. We examined the effect of IGF-I and EGF treatment, separately or in combination, on the vulnerability of steatotic livers to I/R. Our results indicated that I/R impaired IGF-I synthesis only in steatotic livers. Only when a high dose of IGF-I (400 microg/kg) was given to obese animals did they show high circulating IGF-I:IGFBP levels, increased hepatic IGF-I levels, and protection against damage. In lean animals, a dose of 100 microg/kg IGF-I protected nonsteatotic livers. Our results indicated that the combined administration of IGF-I and EGF resulted in hepatic injury parameters in both liver types similar to that obtained by IGF-I and EGF separately. IGF-I increased egf expression in both liver types. The beneficial role of EGF on hepatic I/R injury may be attributable to p38 inhibition in nonsteatotic livers and to PPAR gamma overexpression in steatotic livers. In conclusion, IGF-I and EGF may constitute new pharmacological strategies to reduce the inherent susceptibility of steatotic livers to I/R injury.

Inhibition of angiotensin II action protects rat steatotic livers against ischemia-reperfusion injury.

OBJECTIVE: We examined whether pharmacologic strategies blocking angiotensin II actions protect steatotic livers against ischemia-reperfusion (I/R) injury. The effects of ischemic preconditioning (PC) on angiotensin II were also evaluated. DESIGN: Randomized and controlled animal study. SETTING: Experimental laboratory. SUBJECTS: Zucker rats. INTERVENTIONS: The following experimental groups were studied: I/R, ischemia-reperfusion + angiotensin-converting enzyme inhibitor (I/R+ACE inhibitor), ischemia-reperfusion + angiotensin II type I receptor antagonist (I/R+AT1R antagonist), ischemia-reperfusion + angiotensin II type II receptor antagonist (I/R+AT2R antagonist), and PC (5 mins of ischemia + 10 mins of reperfusion before I/R). In some of these groups, the action of bradykinin (BK) and/or peroxisome-proliferator-activated receptor-gamma (PPARgamma) was altered pharmacologically. MEASUREMENTS AND MAIN RESULTS: I/R+ACE inhibitor, I/R+AT1R antagonist, and I/R+AT2R antagonist reduced hepatic injury in steatotic livers compared with the I/R group. PC reduced angiotensin II generation and hepatic injury in steatotic livers in comparison to I/R group. Our results revealed that I/R+ACE inhibitor, I/R+AT1R antagonist, I/R+AT2R antagonist, and PC increased BK compared with the I/R group. In addition, the effects of PC on BK and hepatic injury were abolished when angiotensin II was administered. Furthermore, administration of BK receptor antagonists to the I/R+ACE inhibitor, I/R+AT1R antagonist, I/R+AT2R antagonist, and PC groups resulted in hepatic injury similar to the I/R group, indicating that the benefits of ACE inhibitor, AT1R antagonist, AT2R antagonist, and PC were abolished when the action of BK was inhibited. Experiments aimed at investigating why BK was protective in steatotic livers indicated that BK acts as a positive regulator of PPARgamma. If PPARgamma action was inhibited, BK did not protect steatotic livers against hepatic injury. CONCLUSIONS: Pharmacologic blockers of angiotensin II action (ACE inhibitors, AT1R antagonists, and AT2R antagonists) and PC, which reduced angiotensin II generation, increased BK generation in steatotic livers after I/R. This in turn increased PPARgamma and protected this type of liver against I/R injury.