Dermatopontin in Bone Marrow Extracellular Matrix Regulates Adherence but Is Dispensable for Murine Hematopoietic Cell Maintenance

The hematopoietic marrow microenvironment is composed of multiple cell types embedded in an extracellular matrix (ECM). We have explored marrow ECM using mass spectrometry and found dermatopontin (DPT), a small non-collagenous ECM protein, to be present. We found that DPT cooperates with other ECM proteins to promote hematopoietic cell adherence in vitro on plastic as well as OP9 stromal cells. We generated constitutional DPT^−/− mice that were viable and had no peripheral lympho-hematopoietic abnormalities. The composition of the marrow of wild-type and DPT^−/− mice was equivalent in terms of cellularity, CFU-C, LSK (Lineage⁻, SCA-1⁺, KIT⁺), and LSK-SLAM (LSK, CD48⁻, CD150⁺) frequencies. These data suggest that DPT fosters adherence but is not required for steady-state hematopoiesis in vivo. There are likely overlapping cellular adhesion mechanisms that can compensate to maintain the hematopoietic niche in the absence of DPT.