Functional and microstructural regulation of three-dimensional tissues by using extracellular matrix

Compared with monolayer cultures, three-dimensional cultures such as multicellular spheroids provide the high cellular functions and the in vivo-like microstructures. Extracellular matrix (ECM) is one of the most important regulators of in vivo tissues' functions and microstructures. A typical three-dimensional culture for assembling spheroid and ECM is to embed spheroid in ECM gel. However, the effect of ECM on the inner of spheroid was not observed because spheroid is embedded in ECM after fabricating spheroid. In the last symposium on MHS, we reported a new method for fabricating ECM containing spheroid which the ECM layer exists between cells in spheroid. In this study, we aimed to reveal whether ECM is able to regulate functions and microstructures of hepatic ECM containing spheroid. To fabricate ECM containing spheroid, we utilized the 3% methylcellulose (MC) medium [1]. We injected 1 μl of diluted ECM solution (Matrigel or collagen) suspending 2000 of Hep G2 cells into the MC medium. To examine contribution of ECM to spheroids, the albumin secretion was measured. The albumin secretion activity of Matrigel containing spheroids was higher than that of normal spheroids. By contrast, when we used type I collagen, the activity was lower than that of normal spheroids. However, type I collagen enhanced cellular proliferation of Hep G2 cells. In addition, we found that Matrigel containing spheroids was effective to form bile canaliculi in spheroids. These results indicated that ECM was able to regulate functions and microstructures of hepatic multicellular spheroids.