Stancu, I.-C. | bioRxiv Science

bioRxiv2022

Hypotrochoidal scaffolds for cartilage regeneration

The main function of articular cartilage is to provide a low friction surface and protect the underlying subchondral bone. The extracellular matrix composition of articular cartilage mainly consists of glycosaminoglycans and collagen type II. Specifically the collagen type II organization has a characteristic organization in three distinct zones; (1) the superficial zone which has collagen fibers oriented parallel to the surface, (2) the intermediate zone where there is no predominant orientation, and (3) the deep zone which shows a high orientation with fibers perpendicular to the underlying bone. Collagen type II fibers in these 3 zones take an arch-like organization that can be mimicked with segments of a hypotrochoidal curve. In this study, a script was developed that allowed the fabrication of scaffolds with a hypotrochoidal design. This design was investigated and compared to a regular 0-90 woodpile design. The results showed that the hypotrochoidal design was successfully fabricated. Micro-CT analyses divided the areas of the scaffold in their distinct zones. In addition, the mechanical analyses revealed that the hypotrochoidal design had a lower component Youngs modulus while the toughness and strain at yield were higher compared to the woodpile design. Fatigue tests showed that the hypotrochoidal design lost more energy per cycle due to the damping effect of the unique microarchitecture. Finite element analyses revealed that the hypotrochoidal design had an improved stress distribution compared to the 0-90 woodpile design due to the lower component stiffness. In addition, data from cell culture under dynamic stimulation demonstrated that the collagen type II deposition was improved in the hypotrochoidal design. Finally, Alcian blue staining revealed that the areas where the stress was higher during the stimulation produced more glycosaminoglycans. Our results highlight a new and simple scaffold design based on hypotrochoidal curves that could be used for cartilage tissue engineering.

bioengineering↗

bioRxiv2021

Glial contribution to cyclodextrin-mediated reversal of cholesterol accumulation in murine NPC1-deficient neurons in vivo

Niemann-Pick type C (NPC) disease is a rare and fatal lysosomal storage disorder presenting severe neurovisceral symptoms. Disease-causing mutations in genes encoding either NPC1 or NPC2 protein provoke accumulation of cholesterol and other lipids in specific structures of the endosomal-lysosomal system and degeneration of specific cells, notably neurons in the central nervous system (CNS). 2-hydroxypropyl-beta-cyclodextrin (CD) emerged as potential therapeutic approach based on animal studies and clinical data, but the mechanism of action on neurons has remained unclear. To address this topic in vivo, we took advantage of the retina as highly accessible part of the (CNS) and intravitreal injections as mode of drug administration. We find that CD enters the endosomal-lysosomal system of neurons and enables the release of lipid-laden lamellar inclusions, which are then removed from the extracellular space by specific types of glial cells. Thus, CD triggers a concerted action of neurons and glial cells to restore lipid homeostasis in the central nervous system.

neuroscience↗