# Biomimetic Fibrinogen Nanofiber Scaffolds for Vascular Hematopoietic Stem Cell Niche Engineering

## TL;DR

Researchers created a lab model of bone marrow niches using fibrinogen nanofibers to study blood stem cells and their environment.

## Contribution

A novel fibrinogen nanofiber scaffold mimics the vascular niche basement membrane for HSC niche engineering.

## Key findings

- Fibrinogen scaffolds are cytocompatible and support cell adhesion and migration.
- The model emulates HSC niche dynamics including residency, exit, and homing.
- The scaffold can serve as a platform for drug testing and tissue engineering.

## Abstract

Hematopoietic stem cells (HSCs) can reconstitute the human blood system. In vivo, HSCs are localized in and regulated by distinct bone marrow (BM) microenvironments, or niches, like the vascular HSC niches near fenestrated sinusoidal blood vessels. These delicate structures, comprising a single‐layered endothelium and a discontinuous basement membrane, pose challenges in soft tissue engineering. In this study, the basement membrane in vascular niches is mimicked using nanofibrous fibrinogen scaffolds. A novel clamping system enables handling the scaffold as a membrane and seeding both sides−one with microvascular endothelial cells (HMEC‐1) and the other with mesenchymal stem and stroma cells (iMSC#3). Subsequently, HSCs and their progenitors (HSPCs) are introduced from both sides to emulate their niche dynamics (residency, exit, and homing). The study reveals that the fibrinogen scaffolds are highly cytocompatible and show good cell‐adhesive properties. In addition, HSPCs are able to migrate through the scaffolds, validating them as fenestrated basement membrane mimetics. This in vitro model offers insights into HSPC behavior in the vascular niche and can serve as a drug testing platform in future studies. Moreover, beyond HSCs, the presented scaffold‐based mimetic of the basement membrane offers new opportunities for mimicking and studying vasculature in tissue engineering approaches.

This study presents an advanced in vitro model of the vascular hematopoietic stem cell niche using self‐assembled fibrinogen nanofibers, mimicking the basement membrane in bone marrow (BM) sinusoids. The model supports the coculture of microvascular endothelial cells, stromal cells, and hematopoietic stem and progenitor cells, providing insights into niche dynamics and offering potential for drug testing and tissue engineering applications.