Showing papers by "Edward F. Srour published in 2021"

Mitigating oxygen stress enhances aged mouse hematopoietic stem cell numbers and function

Abstract: Bone marrow (BM) hematopoietic stem cells (HSCs) become dysfunctional during aging (i.e., they are increased in number but have an overall reduction in long-term repopulation potential and increased myeloid differentiation) compared with young HSCs, suggesting limited use of old donor BM cells for hematopoietic cell transplantation (HCT). BM cells reside in an in vivo hypoxic environment yet are evaluated after collection and processing in ambient air. We detected an increase in the number of both young and aged mouse BM HSCs collected and processed in 3% O2 compared with the number of young BM HSCs collected and processed in ambient air (~21% O2). Aged BM collected and processed under hypoxic conditions demonstrated enhanced engraftment capability during competitive transplantation analysis and contained more functional HSCs as determined by limiting dilution analysis. Importantly, the myeloid-to-lymphoid differentiation ratio of aged BM collected in 3% O2 was similar to that detected in young BM collected in ambient air or hypoxic conditions, consistent with the increased number of common lymphoid progenitors following collection under hypoxia. Enhanced functional activity and differentiation of old BM collected and processed in hypoxia correlated with reduced "stress" associated with ambient air BM collection and suggests that aged BM may be better and more efficiently used for HCT if collected and processed under hypoxia so that it is never exposed to ambient air O2.

Neonatal Osteomacs and Bone Marrow Macrophages Differ in Phenotypic Marker Expression and Function.

Abstract: Osteomacs (OM) are specialized bone-resident macrophages that are a component of the hematopoietic niche and support bone formation. Also located in the niche are a second subset of macrophages, namely bone marrow-derived macrophages (BM Mφ). We previously reported that a subpopulation of OM co-express both CD166 and CSF1R, the receptor for macrophage colony-stimulating factor (MCSF), and that OM form more bone-resorbing osteoclasts than BM Mφ. Reported here are single-cell quantitative RT-PCR (qRT-PCR), mass cytometry (CyTOF), and marker-specific functional studies that further identify differences between OM and BM Mφ from neonatal C57Bl/6 mice. Although OM express higher levels of CSF1R and MCSF, they do not respond to MCSF-induced proliferation, in contrast to BM Mφ. Moreover, receptor activator of NF-κB ligand (RANKL), without the addition of MCSF, was sufficient to induce osteoclast formation in OM but not BM Mφ cultures. OM express higher levels of CD166 than BM Mφ, and we found that osteoclast formation by CD166-/- OM was reduced compared with wild-type (WT) OM, whereas CD166-/- BM Mφ showed enhanced osteoclast formation. CD110/c-Mpl, the receptor for thrombopoietin (TPO), was also higher in OM, but TPO did not alter OM-derived osteoclast formation, whereas TPO stimulated BM Mφ osteoclast formation. CyTOF analyses demonstrated OM uniquely co-express CD86 and CD206, markers of M1 and M2 polarized macrophages, respectively. OM performed equivalent phagocytosis in response to LPS or IL-4/IL-10, which induce polarization to M1 and M2 subtypes, respectively, whereas BM Mφ were less competent at phagocytosis when polarized to the M2 subtype. Moreover, in contrast to BM Mφ, LPS treatment of OM led to the upregulation of CD80, an M1 marker, as well as IL-10 and IL-6, known anti-inflammatory cytokines. Overall, these data reveal that OM and BM Mφ are distinct subgroups of macrophages, whose phenotypic and functional differences in proliferation, phagocytosis, and osteoclast formation may contribute physiological specificity during health and disease. © 2021 American Society for Bone and Mineral Research (ASBMR).

Cellular components of the hematopoietic niche and their regulation of hematopoietic stem cell function.

Abstract: Purpose of review Development and functions of hematopoietic stem cells (HSC) are regulated by multiple cellular components of the hematopoietic niche. Here we review the recent advances in studying the role of three such components -- osteoblasts, osteomacs, and megakaryocytes and how they interact with each other in the hematopoietic niche to regulate HSC. Recent findings Recent advances in transgenic mice models, scRNA-seq, transcriptome profile, proteomics, and live animal imaging have revealed the location of HSC within the bone and signaling molecules required for the maintenance of the niche. Interaction between megakaryocytes, osteoblasts and osteomacs enhances hematopoietic stem and progenitor cells (HSPC) function. Studies also revealed the niche as a dynamic entity that undergoes cellular and molecular changes in response to stress. Aging, which results in reduced HSC function, is associated with a decrease in endosteal niches and osteomacs as well as reduced HSC--megakaryocyte interactions. Summary Novel approaches to study the cellular components of the niche and their interactions to regulate HSC development and functions provided key insights about molecules involved in the maintenance of the hematopoietic system. Furthermore, these studies began to build a more comprehensive model of cellular interactions and dynamics in the hematopoietic niche.

The kidney protects against sepsis by enhancing the systemic release of Uromodulin to stimulate macrophage function

Abstract: Sepsis is associated with significant mortality that persists despite advances in the care of critically ill patients. Concomitant development of acute kidney injury (AKI) markedly increases the mortality of sepsis through unclear mechanisms. While electrolyte disturbances and toxic metabolite buildup likely play a crucial role, loss of a protective molecule(s) from the injured kidney could also contribute to the dire outcomes observed in sepsis with AKI. Uromodulin (Tamm-Horsfall protein, THP) is a kidney-derived protein bidirectionally released in the urine and circulation. We previously showed that AKI causes acute systemic THP deficiency. Here, we show that circulating THP increases in experimental murine sepsis without severe AKI through basolateral shifting of its release within the kidney medulla. Concordantly, in asmall cohort of patient with sepsis and preserved kidney function, circulating THP positively correlates with the degree of critical illness, and accumulates in the lungs of a cohort of patients with ARDS. In a knockout mouse model with sepsis, we show that THP deficiency significantly increases mortality. Using single cell RNA-sequencing, we observe that THP expands a macrophage subset enriched with transcripts required for protein translation, migration and phagocytosis. Indeed, treatment of bone marrow-derived macrophages with THP enhances phagocytosis and the loss of THP in vivo causes an increases bacterial burden within organs during sepsis. Finally, treatment of septic THP-/- mice with exogenous THP improves survival. Together, these findings suggest that THP protects from sepsis by enhancing macrophage function and its loss could explain the detrimental outcomes of sepsis with AKI. Our findings also suggest a potential therapeutic role of THP in sepsis.