3D organoid modeling of extramedullary hematopoiesis.

Background: Under certain clinical and experimental conditions hematopoiesis occurs in other site than bone marrow (BM), such as the liver. Here, we develop a 3D organoid that mimics several components of the hematopoietic niche present during liver extramedullary hematopoiesis.

Aim: To evaluate the capacity of a 3D hematopoietic organoid (3D-HO) to function as a hematopoietic like-niche allowing for blood cell production outside of the BM.

Methods: The 3D-HO is constituted by liver sinusoidal endothelial cells (LSEC) as the stromal component, BM isolated from 5-FU treated mice (FU-BMCs), collagen microspheres and plasma clot as scaffolds. The ability of the 3D-HO to support the survival and functionality of FU-BMCs was investigated by using confocal microscopy, histology analysis, flow cytometry, and clonogenic assays.

Results: After 15 and 30 days, post-ectopic implantation, histological studies of the 3D-HO showed the presence of cells with myeloid and lymphoid lineage morphology. Flow cytometry analysis of these cells showed the presence of cells expressing hematopoietic stem progenitor cells (HSPC) (Sca-1/c-Kit), myeloid (Gr-1) and lymphoid (B220 and CD19) markers. Clonogenic assays showed that cells from the 3D-HO formed hematopoietic colonies. Expression of the gene by cells from the 3D-HO, implanted for 30 days in female mice, indicated that male donor cells persist in this model of extramedullary hematopoiesis.

Conclusions: The 3D-HO constitutes an extramedullary hematopoietic-like niche which supports the survival and functionality of FU-BMCs. It may constitute an efficient model for investigating, and , those factors that control hematopoiesis outside BM.