Myeloid deficiency of heparan sulfate 6-O-endosulfatases impairs bone marrow hematopoiesis

The heparan sulfate (HS) 6-O-endosulfatases or the Sulfs (Sulf1 and Sulf2) are the only known enzymes that can modify HS sulfation status extracellularly and have been shown to regulate diverse biological processes. The role of the Sulfs in bone marrow (BM) hematopoiesis is not known. In this study, we generated a novel mouse line with myeloid-specific deletion of the Sulfs by crossing Sulf1/2 double floxed mice with the LysM-cre line. The LysM-Sulf knockout (KO) male mice exhibited age-dependent expansion of hematopoietic stem cells and the granulocyte-monocyte lineages in the BM, whereas common lymphoid progenitors and B lymphocyte populations were significantly reduced. Although megakaryocytic and erythroid progenitors were not reduced in the BM, the LysM-Sulf KO males suffered age-dependent reduction of red blood cells (RBCs) and platelets in the peripheral blood, suggesting that the production of RBCs and platelets was arrested at later stages. In addition, LysM-Sulf KO males displayed progressive splenomegaly with extramedullary hematopoiesis. Compared to males, LysM-Sulf KO females exhibited a much-reduced phenotype, and ovariectomy had little effect. Mechanistically, reduced TGF-β/Smad2 but enhanced p53/p21 signaling were observed in male but not female LysM-Sulf KO mice. Finally, HS disaccharide analysis via LC-MS/MS revealed increased HS 6-O-sulfation in the BM from both male and female LysM-Sulf KO mice, however, the distribution of 6-O-sulfated motifs were different between the sexes with compensatory increase in Sulf1 expression observed only in LysM-Sulf KO females. In conclusion, our study reveals that myeloid deficiency of the Sulfs leads to multilineage abnormalities in BM hematopoiesis in an age- and sex-dependent manner.