Three‐dimensional reconstruction of internal fascicles and microvascular structures of human peripheral nerves

Abstract

Biofabricated nanostructured and microstructured scaffolds have exhibited great potential for nerve tissue regeneration and functional restoration, and prevascularization and biotransportation within 3D fascicle structures are critical. Unfortunately, an ideal internal fascicle and microvascular model of human peripheral nerves is lacking. In this study, we used microcomputed tomography (microCT) to acquire high‐resolution images of the human sciatic nerve. We propose a novel deep‐learning network technique, called ResNetH3D‐Unet, to segment fascicles and microvascular structures. We reconstructed 3D intraneural fascicles and microvascular topography to quantify the fascicle volume ratio (FVR), microvascular volume ratio (MVR), microvascular to fascicle volume ratio (MFVR), fascicle surface area to volume ratio (FSAVR), and microvascular surface area to volume ratio (MSAVR) of human samples. The frequency distributions of the fascicle diameter, microvascular diameter, and fascicle‐to‐microvasculature distance were analyzed. The obtained microCT analysis and reconstruction provided high‐resolution microstructures of human peripheral nerves. Our proposed ResNetH3D‐Unet method for fascicle and microvasculature segmentation yielded a mean intersection over union (IOU) of 92.1% (approximately 5% higher than the U‐net IOU). The 3D reconstructed model showed that the internal microvasculature runs longitudinally within the internal epineurium and connects to the external vasculature at some points. Analysis of the 3D data indicated a 48.2 ± 3% FVR, 23.7 ± 1.8% MVR, 4.9 ± 0.5% MFVR, 7.26 ± 2.58 mm‐1 FSAVR, and 1.52 ± 0.52 mm‐1 MSAVR. A fascicle diameter of 0.98 mm, microvascular diameter of 0.125 mm, and microvasculature‐to‐fascicle distance of 0.196 mm were most frequent. This study provides fundamental data and structural references for designing bionic scaffolding constructs with 3D microvascular and fascicle distributions.

Skin precursor‐derived Schwann cells accelerate in vivo prevascularization of tissue‐engineered nerves to promote peripheral nerve regeneration

“…Pro‐vascularization strategy emerges as a feasible and effective approach to promote peripheral nerve regeneration (Masgutov et al, 2021; Wang et al, 2018). Furthermore, mimicking autologous nerves, the prevascularization pattern has attracted great attentions in the tissue‐engineered nerve construction (Thibodeau et al, 2022; Yan et al, 2019). So far, in vitro prevascularization through co‐culture of cells and biomaterials has been well‐informed (Kuss et al, 2018; Shafiee et al, 2021; Xu et al, 2022).…”

An experimental and numerical study of the microstructural and biomechanical properties of human peripheral nerve endoneurium for the design of tissue scaffolds

“…Micro-CT was used to acquire high-resolution images from the preprocessed samples using the iodine and freeze-dry (IFD) method described previously ( Yan et al, 2017a ; Yan et al, 2019 ). Preprocessing steps are briefly summarized here for completeness ( Robinson, 2022 ).…”

“…In a previous study, we proposed to implement an iodine and freeze-drying enhanced microscopic computed tomography (micro-CT) imaging technique that would enable us to obtain the high-resolution microstructure of the human peripheral nerve, which allowed us to construct a baseline model for numerical characterization in silico here ( Yan et al, 2017a ; Yan et al, 2019 ; Almeida and Bartolo, 2021 ). The present study aims to investigate the key microstructural characteristics and permeability of the human peripheral nerve eECM, in which the effects of porosity, tortuosity, surface area-to-volume ratio (SAVR) and pore size on the stiffness and permeability are explored using experimental and numerical approaches.…”