Acute Myeloid Leukemia (AML) is the most common acute leukemia in adults. While the clinical presentation is quite uniform, it is a highly heterogeneous disease at the genetic level. Using intravital two-photon microscopy in AML xenograft models, we have previously showed that AML patient-derived samples induced a common pathologic bone marrow (BM) vascular phenotype. To understand the translational potential of our findings we have optimized dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) for the assessment of BM vascular dysfunction. We quantified non-model based parameters from DCE-MRI scans: Contrast Enhancement (CE); Wash-in Rate (WiR); and Wash-out Rate (WoR). CE reflects tissue vascular density and is a measurement of the proportion of fully functional vessels per pixel area, WIR reflects blood flow and tissue perfusion, and WoR reflects vascular permeability and tissue clearance capacity. We first measured DCE parameters in control mice. We observed no gender-related differences in BM DCE parameters, while we found significant age-related changes. As mice age, BM vascular density decreases together with increased vascular permeability and reduced tissue clearance capacity. When compared to age- matched controls, mice injected with AML cell lines showed decreased vascular density, decreased blood inflow, increased vascular permeability and reduced tissue clearance capacity. There was a progressive decline in BM vascular function as the disease burden increased, particularly in WiR and WoR parameters, with even low levels of leukemia significantly altering BM vascular function. When analyzing mice injected with AML patient samples, changes in BM vascular function were more dependent on the AML sample than on the engraftment. Low disease burden did not significantly change DCE vascular parameters. At high disease burden, patient-derived xenografts show different degrees of vascular disruption, spanning from global altered DCE parameters to milder phenotypes. Upon AraC treatment, altered vascular parameters remained unchanged in most of the cases, suggesting inability to fully rescue BM vascular function. In conclusion, we showed that DCE-MRI is able to detect consistent changes associated with BM vasculature induced by aging and leukemia. Despite the heterogeneous nature of the disease, our method captures different degrees of vascular alterations, with WIR having the highest diagnostic potential. Our results further suggest that the detection of a pathologic vascular phenotype in the BM of AML patients could be of use in the clinical scenario.
No relevant conflicts of interest to declare.
Author notes
Asterisk with author names denotes non-ASH members.
