Applications of the Human Bone Marrow Organoid System to Study Hematopoiesis and Anemia Stress

Abstract

Hematopoietic stem and progenitor cells (HSPCs) are precisely organized within specialized bone marrow niches containing hematopoietic and nonhematopoietic cell types. Physiologically accurate human models of this niche environment that include functional HSPCs have been lacking until recently. Using induced pluripotent stem cells (iPSCs) grown in mixed-matrix hydrogels, vascularized three-dimensional human bone marrow organoids (hBMOs) can now be generated that contain mesenchymal, endothelial, and hematopoietic cells, all vital components of the bone marrow niche. While hBMOs have been shown to support engraftment of normal and malignant cells, there are numerous opportunities to use hBMOs for developing a wider experimental toolkit to test gene functions and stress responses. Here, we establish two new applications for the hBMO platform. First, we demonstrate successful engraftment of gene-edited CD34⁺ cells from healthy donors, enabling direct investigation of gene-specific effects on human hematopoiesis in a defined microenvironment. Gene-edited engrafted HSPCs are maintained in hBMOs for 7 days and undergo multilineage differentiation. Second, we adapted a method to induce stress erythropoiesis—a response to acute anemia in mice and humans—in hBMOs, resulting in robust expansion of immunophenotypically defined hematopoietic progenitors and erythroid populations. These two advances expand the laboratory uses for hBMOs and establish this system as a versatile platform for studying human hematopoiesis and erythropoiesis, stress responses, and gene functions within a physiologically relevant bone marrow microenvironment.

Impact Statement

This project establishes and validates new protocols using human bone marrow organoids (hBMOs) with gene editing technologies, creating a versatile platform to study human hematopoiesis in a physiologically relevant microenvironment. By enabling engraftment of CRISPR/Cas9 gene-edited primary human CD34⁺ cells and modeling stress erythropoiesis, these strategies address key limitations of animal models and less complex in vitro systems. By modifying the culture conditions, we also extend the hBMO toolkit to study erythropoietic stress, provide a promising new platform for direct interrogation of gene function in the contexts of niche–hematopoietic interactions, and for investigation of paracrine signaling/transcriptional control of regenerative responses in human cells. hBMOs are a discovery tool for human mechanisms underlying anemia, bone marrow failure, and hematological malignancies and provide a translationally relevant system for testing therapeutic strategies.