Human Tendon-on-a-Chip for modeling vascular inflammatory fibrosis II
Vascular inflammation and myofibroblast activation by TGF-ß1 are key, yet-to-be-fully-understood pathological processes in fibrosis. Here we report the development of a novel human Tendon-on-a-Chip (hToC) to elucidate the role of TGF-ß1 in peritendinous adhesions, a debilitating fibrosis condition affecting flexor tendon, which currently lacks biological therapies. The hToC allows the crosstalk between a vascular compartment harboring endothelial cells and monocytes with a tissue hydrogel compartment containing tendon fibroblasts and macrophages. We find that the hToC replicates in vivo inflammatory and fibrotic phenotypes in preclinical and clinical samples, including myofibroblast differentiation and tissue contraction, excessive ECM deposition, and inflammatory cytokines secretion. We further show the fibrotic phenotypes are driven by the interactions between the vascular and tissue compartments, mediating the transmigration of monocytes. We demonstrate significant overlap in fibrotic transcriptional signatures in the hToC with human tenolysis samples, including the mTOR pathway, a regulatory nexus of fibrosis across various organs. Treatment with Rapamycin suppressed the fibrotic phenotype on the hToC, which validates the hToC as a preclinical alternative for investigating fibrosis and testing therapeutics. Overall design: We developed an in vitro human tendon-on-a-chip (hToC) platform quad culture model composed of human primary tenocytes (TCs) and tissue macrophages (tM?) in a collagen hydrogel model of injured tendon, combined with human umbilical endothelial cells (ECs) and circulating Monocytes (cM?) to model the new vasculature in an injured tendon.  Since TGF-ß1 was a consistent signature of inflammation and fibrosis in the injured tendons, we treated the disease devices with TGF-ß1 and compared them with non-treated hToC devices (controls). We performed bulk RNA-sequencing of the two-compartment hToC to evaluate the effects of TGF-ß1.