Modelling Erythroblastic Islands: Using a Hybrid Model to Assess the Function of Central Macrophage

TL;DR

This paper presents a hybrid computational model combining intracellular regulation, cell interactions, and growth factor diffusion to study the role of macrophages in erythropoiesis, highlighting their impact on island stability.

Contribution

It introduces a novel hybrid model integrating multiple biological scales to analyze the function of macrophages in erythropoiesis, emphasizing spatial and stochastic effects.

Findings

Macrophages enhance erythroblastic island stability.

Pro-survival cytokines from macrophages improve responsiveness.

Model suggests macrophages are crucial for normal erythropoiesis.

Abstract

The production and regulation of red blood cells, erythropoiesis, occurs in the bone marrow where erythroid cells proliferate and differentiate within particular structures, called erythroblastic islands. A typical structure of these islands consists in a macrophage (white cell) surrounded by immature erythroid cells (progenitors), with more mature cells on the periphery of the island, ready to leave the bone marrow and enter the bloodstream. A hybrid model, coupling a continuous model (ordinary differential equations) describing intracellular regulation through competition of two key proteins, to a discrete spatial model describing cell-cell interactions, with growth factor diffusion in the medium described by a continuous model (partial differential equations), is proposed to investigate the role of the central macrophage in normal erythropoiesis. Intracellular competition of the two proteins leads the erythroid cell to either proliferation, differentiation, or death by apoptosis. This approach allows considering spatial aspects of erythropoiesis, involved for instance in the occurrence of cellular interactions or the access to external factors, as well as dynamics of intracellular and extracellular scales of this complex cellular process, accounting for stochasticity in cell cycle durations and orientation of the mitotic spindle. The analysis of the model shows a strong effect of the central macrophage on the stability of an erythroblastic island, when assuming the macrophage releases pro-survival cytokines. Even though it is not clear whether or not erythroblastic island stability must be required, investigation of the model concludes that stability improves responsiveness of the model, hence stressing out the potential relevance of the central macrophage in normal erythropoiesis.