Engineering of fully humanized and vascularized 3D bone marrow niches sustaining undifferentiated human cord blood hematopoietic stem and progenitor cells

Abstract

Hematopoietic stem and progenitor cells (HSPCs) are frequently located around the bone marrow (BM) vasculature. These so-called perivascular niches regulate HSC function both in health and disease, but they have been poorly studied in humans due to the scarcity of models integrating complete human vascular structures. Herein, we propose the stromal vascular fraction (SVF) derived from human adipose tissue as a cell source to vascularize 3D osteoblastic BM niches engineered in perfusion bioreactors. We show that SVF cells form self-assembled capillary structures, composed by endothelial and perivascular cells, that add to the osteogenic matrix secreted by BM mesenchymal stromal cells in these engineered niches. In comparison to avascular osteoblastic niches, vascularized BM niches better maintain immunophenotypically-defined cord blood (CB) HSCs without affecting cell proliferation. In contrast, HSPCs cultured in vascularized BM niches showed increased CFU-granulocyte-erythrocyte-monocyte-megakaryocyte (CFU-GEMM) numbers. The vascularization also contributed to better preserve osteogenic gene expression in the niche, demonstrating that niche vascularization has an influence on both hematopoietic and stromal compartments. In summary, we have engineered a fully humanized and vascularized 3D BM tissue to model native human endosteal perivascular niches and revealed functional implications of this vascularization in sustaining undifferentiated CB HSPCs. This system provides a unique modular platform to explore hemato-vascular interactions in human healthy/pathological hematopoiesis.

Bioengineered Living Bone Grafts—A Concise Review on Bioreactors and Production Techniques In Vitro

“…The developed in vitro pre-vascularization procedure allowed for obtaining a vascularized bone scaffold that was characterized by improved cellular density and better microvascular networks compared with the culture in static conditions. Moreover, it has been proved that the stromal vascular fraction (SVF) of adipose tissue may be used as a source of vasculogenic cells for the production of vascularized bone tissue grafts [101,102]. The SVF is a heterogeneous cell population that contains MSCs, preadipocytes, mature endothelial cells, and endothelial progenitor cells that promote the formation of microvascular networks [37,101].…”

“…Moreover, it has been proved that the stromal vascular fraction (SVF) of adipose tissue may be used as a source of vasculogenic cells for the production of vascularized bone tissue grafts [101,102]. The SVF is a heterogeneous cell population that contains MSCs, preadipocytes, mature endothelial cells, and endothelial progenitor cells that promote the formation of microvascular networks [37,101]. Furthermore, to support the vascularization of the bone grafts, some investigators chose an approach to deliver pro-angiogenic factors (e.g., VEGF, PDGF, FGF, and BMP) that enhanced both new vessel and bone formation [75].…”

Osteoblast Lineage Support of Hematopoiesis in Health and Disease

“…Finally, tissue engineered threedimensional (3D) bone marrow niches hold promise as an approach to more rigorously probe cellular and molecular interactions within the bone marrow microenvironment. (184)(185)(186) Alterations in niche-resident osteoblasts have the potential to disrupt hematopoiesis and promote the development of hematopoietic malignancies. Similarly, reports of bone loss and altered bone homeostasis driven by hematopoietic malignancies demonstrate a reciprocal relationship between the hematopoietic and mesenchymal lineages.…”

“…Finally, tissue engineered three‐dimensional (3D) bone marrow niches hold promise as an approach to more rigorously probe cellular and molecular interactions within the bone marrow microenvironment. ( 184‐186 )…”

Biomimetic human bone marrow tissues: models to study hematopoiesis and platforms for drug testing

“…This vascularized O-N, recapitulating features of native endosteal perivascular microenvironments, sustains the maintenance of primitive HSCs better than avascular osteoblastic niches. 9 On the other hand, SVF cells were also used to generate a non-osteogenic stromal-vascular niche (SV-N), which mimics features from perivascular niches in central BM. 8 …”