# Lymphatic incorporated biomimetic scaffold enhances Osteoangio-lymphogenic coupling via HIF-1α mediated mitochondrial reprogramming for osteoporotic bone repair

## TL;DR

A 3D-printed scaffold promotes bone repair by coordinating bone, blood vessel, and lymphatic growth through a novel cell interaction system.

## Contribution

First scaffold integrating lymphatic regulation and organoid-like systems for bone repair via HIF-1α mediated metabolic reprogramming.

## Key findings

- The scaffold recruits BMSCs, HUVECs, and LECs to form self-assembled cell islands for tissue regeneration.
- It enhances bone formation, vascular remodeling, and lymphatic maturation in an osteoporotic model.
- HIF-1α signaling is crucial for mitochondrial reprogramming that supports angiogenesis and osteogenesis.

## Abstract

Recent studies have challenged the notion that bone tissue lacks lymphatic vessels, highlighting their essential role in bone regeneration. Effective bone repair relies on the interplay of osteogenesis, angiogenesis, and lymphangiogenesis. Here, we present a three dimensional-printed biomimetic Gelatin methacryloyl/icariin@Mesoporous silica nanoparticle/Hydroxyapatite (GelMA/ICA@MSN/HAp) scaffold designed to recruit bone marrow mesenchymal stem cells (BMSCs), human umbilical vein endothelial cells (HUVECs), and lymphatic endothelial cells (LECs), enabling these cells to self-assemble into “cell islands” that coordinate tissue regeneration. The scaffold exhibits excellent biocompatibility, biodegradability, and sustained cytokine release. In vitro, it promotes the migration, proliferation, and lineage-specific differentiation of BMSCs, HUVECs, and LECs. In an osteoporotic bone defect model, the scaffold significantly enhances new bone formation, supports vascular remodeling by recruiting HUVECs, and induces lymphatic maturation via LECs, accompanied by upregulation of bone morphogenetic protein 2, vascular endothelial growth factor, and prospero homeobox protein 1. Transcriptomic analysis identifies activation of the hypoxia-inducible factor 1 alpha (HIF-1α) signaling pathway as crucial to these effects. Mechanistically, LECs-derived conditioned medium stimulates HUVECs angiogenesis and BMSCs osteogenesis by inducing HIF-1α mediated mitochondrial metabolic reprogramming. This is the first study to integrate lymphatic modulation into scaffold design for bone repair, achieving osteo-angio-lymphogenic coupling and establishing a novel organoid model for bone regeneration.

(A) Schematic diagram of the preparation process for the GelMA/ICA@MSN/HAp scaffold. (B) Schematic diagram of the in vivo action mechanism of the GelMA/ICA@MSN/HAp scaffold. (C) HIF-1α mediated mitochondrial metabolic reprogramming promotes bone repair.Image 1

•A 3D-printed GelMA/ICA@MSN/HAp scaffold recruits BMSCs, HUVECs, and LECs to form self-organized multicellular “cell islands” for bone repair.•The scaffold integrates osteo–angio–lymphogenic coupling in one platform, driving robust and spatially organized bone regeneration.•LECs-derived medium enhances angiogenesis and osteogenesis via HIF-1α–mediated mitochondrial metabolic reprogramming in HUVECs and BMSCs.•This work presents the first scaffold-based strategy integrating lymphatic regulation and an organoid-like system for bone repair.

A 3D-printed GelMA/ICA@MSN/HAp scaffold recruits BMSCs, HUVECs, and LECs to form self-organized multicellular “cell islands” for bone repair.

The scaffold integrates osteo–angio–lymphogenic coupling in one platform, driving robust and spatially organized bone regeneration.

LECs-derived medium enhances angiogenesis and osteogenesis via HIF-1α–mediated mitochondrial metabolic reprogramming in HUVECs and BMSCs.

This work presents the first scaffold-based strategy integrating lymphatic regulation and an organoid-like system for bone repair.