This issue features a collection of Physician-Scientist Development articles that highlight the work, challenges, and goals faced along the physician-scientist career path. It is introduced by an Editorial from Oliver Eickelberg, Christopher S. Williams, and Kyu Y. Rhee. The cover image is a collage of drawings that were produced by children who were prompted to illustrate what comes to mind when they think of a physician-scientist. Illustrations were provided by Demetri Kitsios, Liam Snyder, Elizabeth Neal, and Jocelyn L. (clockwise from the top right).
Fibroblasts are central to pathogenesis of systemic sclerosis (SSc). However, studies of conventional explant fibroblast cultures incompletely reflect disease biology and treatment response. We isolated a second non-migratory “resident” population of fibroblasts from skin biopsies after outgrowth of explant “migratory” cells. These non-motile resident fibroblasts were compared with migratory cells from the same biopsy, using functional studies, bulk and scRNAseq, and localised in situ by multichannel immunofluorescence. Migratory and resident fibroblast populations in SSc showed distinct pro-fibrotic characteristics and gene expression for pathogenic pathways differing by stage and autoantibody subgroup. TGFβ signalling was highly active in migratory fibroblasts in early stage dcSSc. Conversely, resident fibroblasts had less upregulated TGFβ signalling, especially in late dcSSc. Increased chemokine expression was a hallmark of resident fibroblasts at all stages. In vitro studies confirmed differential response to TGFβ1 and CCL2 between migratory and resident cells. We suggest that migratory fibroblasts are especially important in early skin disease whereas non-migratory fibroblasts may have a regulatory role and contribute more to fibrosis in later stage disease. Thus, we have identified a pathogenic fibroblast population in SSc, not isolated by conventional explant culture, that could play an important role in fibrosis and be targeted therapeutically.
Kristina E.N. Clark, Shiwen Xu, Moustafa Attar, Voon H. Ong, Christopher D. Buckley, Christopher P. Denton
Degenerative retinal disorders leading to irreversible photoreceptor death are a common cause of blindness. Optogenetic gene therapy aims to restore vision in affected individuals by introducing light sensitive opsins into the surviving neurons of the inner retina. While up until now the main focus of optogenetic therapy has been on terminally blind individuals, treating at stages where residual native vision is present could have several advantages. Yet, it is still unknown how residual native and optogenetic vision would interact if present at the same time. Using transgenic mice expressing the optogenetic tool ReaChR in ON-bipolar cells, we herein examine this interaction through electroretinography (ERG) and visually evoked potentials (VEP). We find that optogenetic responses show a peculiar ERG signature and are enhanced in retinas without photoreceptor loss. Conversely, native responses are dampened in the presence of ReaChR. Moreover, in VEP recordings we find that optogenetic responses reach the cortex asynchronous to the native response. These findings should be taken into consideration when planning future clinical trials and may direct future preclinical research to optimize optogenetic approaches for visual restoration. The identified ERG signatures moreover may serve to track treatment efficiency in clinical trials.
Eleonora Carpentiero, Steven Hughes, Jessica Rodgers, Nermina Xhaferri, Sumit Biswas, Michael J. Gilhooley, Mark W. Hankins, Moritz Lindner
Bronchiolitis obliterans syndrome (BOS) is a progressive, fatal obstructive lung that occurs following lung transplant, where it is termed chronic lung allograft dysfunction BOS (CLAD-BOS), or as the primary manifestation of pulmonary chronic graft versus host disease (cGVHD-BOS) following allogeneic hematopoietic stem cell transplant. Disease pathogenesis is poorly understood, however chronic alloreactivity is common to both conditions, suggesting a shared pathophysiology. We performed single-cell RNA-Seq (scRNA-Seq) on explanted human lungs from 4 CLAD-BOS patients, 3 cGVHD-BOS patients, and 3 deceased controls to identify cell types, genes, and pathways enriched in BOS to better understand disease mechanisms. In both forms of BOS, we found an expanded population of CD8+ tissue resident memory T-cells (TRM), which was distinct to BOS compared to other chronic lung diseases. In addition, BOS samples expressed genes and pathways associated with macrophage chemotaxis and proliferation, including in non-immune cell populations. We also identify dysfunctional stromal cells in BOS, characterized by pro and anti-fibrotic gene programs. These data suggest substantial cellular and molecular overlap between CLAD- and cGVHD-BOS and therefore, common pathways for possible therapeutic intervention.
Patrick W. Mellors, Ana N. Nottingham, Bruno Casino Remondo, Maksim Shestov, Joseph D. Planer, Andrew R. Peterson, Yun Ying, Su Zhou, Jason D. Christie, Joshua M. Diamond, Edward Cantu, Maria C. Basil, Saar Gill
We defined injury-induced transcriptome states in 4502 kidney transplant biopsies taken 1 day to 45 years post-transplant using genome-wide microarrays. Injury was measured by injury-induced gene sets and classifiers previously developed in transplants. In principal component analysis, PC1 correlated with both acute and chronic kidney injury and related inflammation, and PC2 with time post-transplant. PC3 was a novel dimension that correlated with epithelial remodeling pathways. Both PC1 and PC3 correlated with reduced survival, PC1 effects strongly increasing with time whereas PC3 effects being time-independent. In this model, we studied the expression of genes annotated in native kidneys in epithelial cells with failed repair: 12 “New” gene sets previously defined in single nucleus RNA sequencing of native kidneys with AKI (Genome Med.14(1):103). The “New4” gene sets reflecting epithelial-mesenchymal transition (EMT) correlated with injury PC1, lower eGFR, higher donor age, and future failure as strongly as any gene sets previously derived in transplants, independent of nephron segment of origin and graft rejection. These results suggest that there are two distinct dimensions in kidney transplant response to injury: PC1, AKI-induced changes, failed repair, and inflammation; and PC3, a response involving epithelial remodeling without inflammation. Increasing kidney age amplifies PC1 and particularly PC3.
Philip F. Halloran, Jessica Chang, Martina Mackova, Katelynn Madill-Thomsen, Enver Akalin, Tarek Alhamad, Sanjiv Anand, Miha Arnol, Rajendra Baliga, Mirosław Banasik, Christopher Blosser, Georg Böhmig, Daniel Brennan, Jonathan Bromberg, Klemens Budde, Andrzej Chamienia, Kevin Chow, Michał Ciszek, Declan de Freitas, Dominika Dęborska-Materkowska, Alicja Debska-Ślizień, Arjang Djamali, Leszek Domański, Magdalena Durlik, Gunilla Einecke, Farsad Eskandary, Richard Fatica, Iman Francis, Justyna Fryc, John Gill, Jagbir Gill, Maciej Glyda, Sita Gourishankar, Marta Gryczman, Gaurav Gupta, Petra Hruba, Peter Hughes, Arskarapurk Jittirat, Zeljka Jurekovic, Layla Kamal, Mahmoud Kamel, Sam Kant, Nika Kojc, Joanna Konopa, James Lan, Roslyn Mannon, Arthur Matas, Joanna Mazurkiewicz, Marius Miglinas, Thomas Mueller, Marek Myślak, Seth Narins, Beata Naumnik, Anita Patel, Agnieszka Perkowska-Ptasińska, Michael Picton, Grzegorz Piecha, Emilio Poggio, Silvie Rajnochová Bloudíčková, Thomas Schachtner, Soroush Shojai, Majid Sikosana, Janka Slatinská, Katarzyna Smykal-Jankowiak, Željka Veceric Haler, Ondrej Viklicky, Ksenija Vucur, Matthew R. Weir, Andrzej Wiecek, Zbigniew Włodarczyk, Harold Yang, Ziad Zaky, Patrick T. Gauthier, Christian Hinze
Invasive aspergillosis is characterized by lung hemorrhage and release of extracellular heme, which promotes fungal growth. Heme can also mediate tissue injury directly, and both fungal growth and lung injury may induce hemorrhage. To assimilate these interdependent processes, we hypothesized that, during aspergillosis, heme mediates direct lung injury independent of fungal growth, leading to worse infection outcomes, and the scavenger protein, hemopexin, mitigates these effects. Mice with neutropenic aspergillosis were found to have a time-dependent increase in lung extracellular heme and a corresponding hemopexin induction. Hemopexin deficiency resulted in markedly increased lung injury, fungal growth, and lung hemorrhage. Using a computational model of the interactions of Aspergillus, heme, and the host, we predicted a critical role for heme-mediated generation of neutrophil-extracellular traps in this infection. We tested this prediction using a fungal strain unable to grow at body temperature, and found that extracellular heme and fungal exposure synergize to induce lung injury by promoting NET release, and disruption of NETs was sufficient to attenuate lung injury and fungal burden. These data implicate heme-mediated NETosis in both lung injury and fungal growth during aspergillosis, resulting in a detrimental positive feedback cycle that can be interrupted by scavenging heme or disrupting NETs.
Ganlin Qu, Henrique A.L. Ribeiro, Angelica L. Solomon, Luis Sordo Vieira, Yana Goddard, Nickolas G. Diodati, Arantxa V. Lazarte, Matthew Wheeler, Reinhard Laubenbacher, Borna Mehrad
In this episode, Davide Croci, Sandra van Wilpe, and Niven Mehra explain that their manuscript predicts clinical benefit to immunotherapy by analyzing combined biomarkers from circulating tumor DNA and immune cell gene expression data in blood...