Monocyte Recruitment for Vascular Tissue Regeneration

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Vascular Biology

Background:

• Tissue engineered vascular grafts (TEVs) often lack sufficient cells for effective regeneration.
• Recruiting endogenous cells, such as monocytes, is a promising strategy for vascular tissue regeneration.
• Acellular TEVs require methods to promote cell infiltration and differentiation.

Purpose of the Study:

• To develop a strategy for recruiting monocytes (MCs) from blood to regenerate vascular tissue in unseeded, cell-free tissue engineered vascular grafts (TEVs).
• To investigate the ability of a specific fusion protein (H2R5) to capture and differentiate monocytes on vascular graft surfaces.
• To evaluate the in vivo performance of H2R5-functionalized acellular TEVs in promoting vascular regeneration.

Main Methods:

• Immobilization of the H2R5 fusion protein on the surface of vascular grafts.
• Assessment of MC capture under static and flow conditions, analyzing shear stress dependence.
• In vivo implantation of H2R5-functionalized acellular-tissue engineered vessels (A-TEVs) into mouse aortas.
• Histological and immunohistochemical analysis to evaluate cell infiltration, differentiation, and tissue formation.
• Lineage tracing using a CX3CR1-confetti mouse model to track MC/macrophage (Mϕ) contribution.

Main Results:

• The H2R5 fusion protein successfully captured blood-derived MCs in a shear stress-dependent manner.
• Bound MCs differentiated into Mϕ expressing both M1 and M2 phenotype-specific genes.
• Implanted H2R5-functionalized A-TEVs remained patent and formed a continuous endothelium expressing endothelial cell (EC) and MC-specific proteins.
• Underneath the endothelium, multiple cell layers formed, coexpressing smooth muscle cell (SMC) and MC markers.
• Lineage tracing confirmed MC/Mϕ populated the graft lumen, supporting their role in endothelialization and vascular wall formation.

Conclusions:

• Circulating monocytes represent a viable cell source for the regeneration of acellular vascular grafts.
• The H2R5 fusion protein serves as an effective chemoattractant and differentiation cue for monocytes.
• This strategy demonstrates potential for promoting endothelialization and vascular wall formation in engineered vascular grafts through endogenous cell recruitment.