Role of the mesenchymal stromal cells in bone marrow failure of Fanconi Anemia patients

Introduction: Fanconi anemia (FA) is an inherited disorder characterized bybone marrow failure, congenital malformations, and predisposition to malignancies.Alterations in hematopoietic stem cells (HSC) have been reported, but little is knownregarding the bone marrow (BM) stroma. Thus, the characterization of MesenchymalStromal Cells (MSC) would help to elucidate their involvement in the BM failure.Methods: We characterized MSCs of 28 FA patients (FA-MSC) before and aftertreatment (hematopoietic stem cell transplantation, HSCT; or gene therapy, GT).Phenotypic and functional properties were analyzed and compared with MSCsexpanded from 26 healthy donors (HD-MSCs). FA-MSCs were geneticallycharacterized through, mitomycin C-test and chimerism analysis. Furthermore, RNA-seq profiling was used to identify dysregulated metabolic pathways. Results: Overall,FA-MSC had the same phenotypic and functional characteristics as HD-MSC. Of note,MSC-GT had a lower clonogenic efficiency and MSC- HSCT had a lower ability toinhibit mitogen-induced T-cell proliferation. These findings were not confirmed in thewhole FA patients cohort. Transcriptomic profiling identified dysregulation in HSCself-maintenance pathways in FA-MSC (HOX), confirmed by real-time quantitativepolymerase chain reaction (RT-qPCR). Discussion: Our study provides acomprehensive characterization of FA-MSCs, including for the first time MSC-GT andconstituting the largest series published to date. Interestingly, transcript profilingrevealed dysregulation of metabolic pathways related to HSC self-maintenance. Takentogether, our results or findings provide new insights into the pathophysiology of thedisease, although whether these niche defects are involved in the hematopoietic defectsseen of FA deserves further investigation.