Cultivation of Hepatic Stellate Cells in 3D ECM to Simulate Physiological and Fibrotic Conditions

Abstract

BackgroundHepatic stellate cells, the major providers of hepatic retinoids and extracellular matrix (ECM), reside in the space of Disse filled with loose basement like ECM, and flanked by hepatocytes and sinusoidal endothelial cells. Upon hepatic injury, stellate cells are activated to express multiple matrix metalloproteinases (MMPs) and to mobilize retinoids for wound healing. In chronic injury, the quiescent stellate cells undergo trans‐differentiation into myofibroblast like cells, marked by loss of retinoids, expression interstitial ECM as well as smooth muscle actin (alpha‐SMA), and gain of contractibility. Although knowledge has been evolved substantially, two fundamental questions remain largely unknown as to how, in normal liver, HSCs maintain quiescence, and how, by injury, HSCs are activated within the ECM milieu.ResultsTo recapitulate the sub‐sinusoid microenvironment we embedded rat primary stellate cells in three‐dimensional ECM (3D ECM). Cultured on plastic, the stellate cells activated spontaneously, showing loss of vitamin A droplets and expression of alpha‐SMA. However, in 3D Matrigel, stellate cells retained retinoid droplets, in association with elevated level of lecithin retinoid acyltransferase (LRAT), a key enzyme for retinol esterification. In 3D ECM, stellate cells were arrested at G0/G1 phase, while on plastic the cells underwent cell cycling and stopped at G2/M phase. We then reconstituted the microenvironment of sinusoids by introducing Kupffer cells, the major hepatic inflammatory cells, into 3D ECM with HSCs. Activated Kupffer cells triggered subsequent activation of stellate cells, evidenced by expression of multiple MMPs, buildup of stress fibers, and loss of retinoids. The Kupffer cell‐mediated activation of stellate cells was blocked by interleukin‐1 receptor antagonist, demonstrating interleukin‐1 as a major injury signal from Kupffer cells conducting stellate cell activation and trans‐differentiation. Furthermore, within 3D ECM, but not on the plastic, interleukin‐1 signal was greatly amplified by stellate cells in an autocrine manner, which may exacerbate liver injury by expressing MMPs in the space of Disse. The myofibroblastic cells derived from the 3D ECM culture were contractile in response to endothelin.ConclusionThe 3D ECM culture provides a model to simulate key physiological functions of stellate cells in normal liver, and also to recapitulate patho‐physiological responses in liver injury. The method may also be used in cell‐based drug screening to identify components targeting liver failure and fibrosis.Support or Funding InformationNational Institutes of Health (NIH) Grants R01s, DK069418‐05 and AR051558, and the Natural Science Foundation of ChinaThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.