Mesoscopic 3D mapping and quantitative analysis of adult human dermal micro-vessels

The skin vascular plexus is essential to skin structure and function, with its morphological changes being linked to skin and systemic diseases. While current detection methods are largely limited to two-dimensional (2D) analysis, recent advances in tissue clearing and light-sheet imaging now enable three-dimensional (3D) visualization of microstructures, transforming this field. This study reports the first quantitative 3D histological analysis of adult human dermal microvascular system at a resolution of 1.0 µm. The results showed that the total length of blood vessels was 20.21 mm in 1 mm³ of dermal tissue. The inner diameters of the papillary dermal plexus (PDP), superficial reticular plexus (SRP), and deep reticular plexus (DRP) were 0.23-8.41 µm, 0.01-44.43 µm, and 0.01-74.00 µm, respectively. Therefore, we calculated the total length of an adult's dermal blood vessels to be 36.4-181.9 km, and their total inner surface area to be 0.39-1.97 m². We estimated the potential volume of dermal blood vessels, when fully opened and dilated, to be 412.0 ml. Interestingly, 48.99% of the dermal blood vessels were found to be closed. The vessels' branch numbers were assessed ranged from 25.53 to 56.20 in 1 mm³ of dermal tissue, and from 0 to 265 for each vessel. The trajectories and angulations along the X, Y and Z axes of dermal vessels were measured as well. Our study investigated the quantitative 3D histological characteristics of human adult skin dermal vessels, which are relevant to histology, physiology, and pathology, as well as to tissue engineering.