Infused wild-type macrophages reside and self-renew in the liver to rescue the hemolysis and anemia of Hmox1-deficient mice

Abstract

Heme oxygenase 1 (HMOX1), the inducible enzyme that catabolizes the degradation of heme into biliverdin, iron, and carbon monoxide, plays an essential role in the clearance of senescent and damaged red blood cells, systemic iron homeostasis, erythropoiesis, vascular hemostasis, and oxidative and inflammatory stress responses. In humans, HMOX1 deficiency causes a rare and lethal disease, characterized by severe anemia, intravascular hemolysis, as well as vascular and tissue damage. Hmox1 knockout (KO) mice recapitulated the phenotypes of HMOX1-deficiency patients and could be rescued by bone marrow (BM) transplantation that engrafted donor’s hematopoietic stem cells into the recipient animals after myeloablation. To find better therapy and elucidate the contribution of macrophages to the pathogenesis of HMOX1-deficiency disease, we infused wild-type (WT) macrophages into Hmox1 KO mice. Results showed that WT macrophages engrafted and proliferated in the livers of Hmox1 KO mice, which corrected the microcytic anemia, rescued the intravascular hemolysis, restored iron homeostasis, eliminated kidney iron overload and tissue damage, and provided long-term protection. These results showed that a single macrophage infusion delivered a long-term curative effect in Hmox1 KO mice, obviating the need for BM transplantation, and suggested that the HMOX1 disease stems mainly from the loss of viable reticuloendothelial macrophages. Our work provides new insights into the etiology of HMOX1 deficiency and demonstrates the potential of infusion of WT macrophages to prevent disease in patients with HMOX1 deficiency and potentially other macrophage-related diseases.

Characterization of hepatic macrophages and evaluation of inflammatory response in heme oxygenase-1 deficient mice exposed to scAAV9 vectors

“…Increased level of MCP-1 in the livers of HO-1 KO mice resulted in constant recruitment and significantly higher than in WT mice numbers of F4/80 low CD11b high MDMs. It was recently shown that WT bone marrow derived macrophages engraft in the livers of HO-1 KO mice, differentiate into KCs, and self-renew, protecting the recipient for several weeks and potentially for a lifetime [29,55]. In the present study, in WT mice we noted the expansion of KCs 3 days after delivery of the 1 st dose of scAAV9-GFP (their number after the 2 nd vector dose was comparable with untreated mice).…”

Macrophage metabolic adaptation to heme detoxification involves CO-dependent activation of the pentose phosphate pathway

“…During episodes of hemolysis, macrophages in the spleen and liver are responsible for detoxifying heme from the extracellular environment. 29,45 To examine the metabolic state of these organ systems in a model of chronic hemolysis, we used Townes SCD transgenic mice, which express human b-globin instead of the endogenous mouse protein. [46][47][48] When compared with mice that expressed normal human hemoglobin (b A mice), mice that expressed sickle hemoglobin (b S mice) had significantly higher levels of free heme in their serum (Figure 7A).…”

M-CSF supports medullary erythropoiesis and erythroid iron demand following burn injury through its activity on homeostatic iron recycling

“…Insufficient macrophage iron recycling function commonly leads to accumulation of iron in tissues. Non-heme iron increases in Nramp1−/− mice which do not efficiently www.nature.com/scientificreports/ recycle iron from damaged red blood cells 44 , in myeloid specific Fpn1−/− mice due to impaired mobilization from macrophages 45 , in Hmox1−/− mice due to heme toxicity that leads to broad depletion of iron recycling macrophages 21,46 , and Spic−/− mice due to loss of red pulp macrophages 23 . Further, we found the exacerbation of iron restricted erythropoiesis caused by post burn M-CSF neutralization was associated with augmented secretion of G-CSF and IL-6.…”