Researchers found that vascular endothelial cells appeared as early as six days into the organoid differentiation process and persisted for several months. As the skin organoids matured, the developing blood vessel networks became progressively surrounded by mural cells, resembling stabilising structures seen in native human skin. 

When exposed to inflammatory triggers, the organoids activated their blood vessels and surrounding tissue, expressing proteins involved in immune-cell homing and releasing additional inflammatory mediators. The researchers also demonstrated that the organoid blood vessels could regrow after sharp-object injury. 

The authors note that the vascular structures showed a molecular signature resembling small arteries, but not veins or lymphatic vessels, indicating that the model remains imperfect. 

The findings suggest that skin organoids could provide a useful platform for studying the role of cutaneous blood vessels in inflammation, repair, regeneration and ageing, while supporting the development of more human-relevant alternatives to animal models.