Chronic viral infections persistently alter marrow stroma and impair hematopoietic stem cell fitness

Chronic viral infections are associated with hematopoietic suppression, bone marrow (BM) failure, and hematopoietic stem cell (HSC) exhaustion. However, how persistent viral challenge and inflammatory responses target BM tissues and perturb hematopoietic competence remains poorly understood. Here, we combine functional analyses with advanced 3D microscopy to demonstrate that chronic infection with lymphocytic choriomeningitis virus leads to (1) long-lasting decimation of the BM stromal network of mesenchymal CXCL12-abundant reticular cells, (2) proinflammatory transcriptional remodeling of remaining components of this key niche subset, and (3) durable functional defects and decreased competitive fitness in HSCs. Mechanistically, BM immunopathology is elicited by virus-specific, activated CD8 T cells, which accumulate in the BM via interferon-dependent mechanisms. Combined antibody-mediated inhibition of type I and II IFN pathways completely preempts degeneration of CARc and protects HSCs from chronic dysfunction. Hence, viral infections and ensuing immune reactions durably impact BM homeostasis by persistently decreasing the competitive fitness of HSCs and disrupting essential stromal-derived, hematopoietic-supporting cues

3D Microscopy of Murine Bone Marrow Hematopoietic Tissues

The soft marrow tissues, which are found disseminated throughout bone cavities, are prime sites for hematopoietic cell production, development, and control of immune responses, and regulation of skeletal metabolism. These essential functions are executed through the concerted and finely tuned interaction of a large variety of cell types of hematopoietic and nonhematopoietic origin, through yet largely unknown sophisticated molecular mechanisms. A fundamental insight of the biological underpinnings of organ function can be gained from the microscopic study of the bone marrow (BM), its complex structural organization and the existence of cell-specific spatial associations. Albeit the application of advanced imaging techniques to the analysis of BM has historically proved challenging, recent technological developments now enable the interrogation of organ-wide regions of marrow tissues in three dimensions at high resolution. Here, we provide a detailed experimental protocol for the generation of thick slices of BM from murine femoral cavities, the immunostaining of cellular and structural components within these samples, and their optical clearing, which enhances the depth at which optical sectioning can be performed with standard confocal microscopes. Collectively, the experimental pipeline here described allows for the rendering of single-cell resolution, multidimensional reconstructions of vast volumes of the complex BM microenvironment

Chronic viral infections persistently alter marrow stroma and impair hematopoietic stem cell fitness

Chronic viral infections are associated with hematopoietic suppression, bone marrow (BM) failure, and hematopoietic stem cell (HSC) exhaustion. However, how persistent viral challenge and inflammatory responses target BM tissues and perturb hematopoietic competence remains poorly understood. Here, we combine functional analyses with advanced 3D microscopy to demonstrate that chronic infection with lymphocytic choriomeningitis virus leads to (1) long-lasting decimation of the BM stromal network of mesenchymal CXCL12-abundant reticular cells, (2) proinflammatory transcriptional remodeling of remaining components of this key niche subset, and (3) durable functional defects and decreased competitive fitness in HSCs. Mechanistically, BM immunopathology is elicited by virus-specific, activated CD8 T cells, which accumulate in the BM via interferon-dependent mechanisms. Combined antibody-mediated inhibition of type I and II IFN pathways completely preempts degeneration of CARc and protects HSCs from chronic dysfunction. Hence, viral infections and ensuing immune reactions durably impact BM homeostasis by persistently decreasing the competitive fitness of HSCs and disrupting essential stromalderived, hematopoietic-supporting cues.ISSN:0022-1007ISSN:1540-0069ISSN:1540-953