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Many key functions performed by the liver depend on the interaction between parenchymal cells and the microenvironment comprised of neighboring cells and extracellular matrix. The biological macromolecules in the matrix, which are dynamically changing, participate in various physiological processes through interactions with cell surface receptors, antigens, and ion channels. We found the rat liver biomatrix scaffold (LBS) prepared from adult rats is more effective in enhancing the function of hepatic spheroids than those derived from newborn or senile rats. Combined with matrisome and bioinformatics analyses, we further found that the glycoproteins, fibronectin and fibrinogen may have special potential for improving hepatocyte function. Human primary hepatocyte organoids and HepaRG spheroids showed more mature hepatocyte phenotype after adding fibronectin and fibrinogen to the culture system. During the cultivation of hepatic spheroids, fibrinogen resulted in an increase in cell-cell junction by promoting cell aggregation and helping fibronectin to assemble on cell surface, which resulted in activation of Wnt/β-catenin pathway. Fibronectin-integrin αVβ1-Wnt/β-catenin may be the axis of signal transduction in parenchymal cell microenvironment. Importantly, fibrinogen enhances the signal transduction. These results suggest that the addition of fibronectin and fibrinogen to the 3D culture system is a new strategy for inducing parenchymal cell functional maturation.

The prevalence of nonalcoholic fatty liver disease (NAFLD), a common cause of chronic liver disease, continues to increase in parallel with that of obesity. Currently, there are no preclinical models to study its complex pathogenesis nor to assess candidate therapies. We have established a tissue-engineered (TE) liver by seeding cells into liver-derived matrix scaffolds and then perfusing the scaffolds with a medium that dynamically provides requisite nutrients, vitamins, minerals, and hormones. Liver-specific biomatrix scaffolds, comprised of almost all of the liver's known extracellular matrix (ECM) components and matrix-bound soluble signals (e.g., growth factors/cytokines), were recellularized with human hepatic cell line HepG2 and perfused with a complete medium enabling the cells to form functioning liver tissue. By perfusing the system with medium with a high fat content, the cells established a TE fatty (TEF) liver model paralleling that of livers in NAFLD patients. The high fat medium containing 500 μM of free fatty acids (FFAs) (oleic acid:palmitic acid = 2:1) caused the TEF livers to accumulate 2-times more fat than those in the control medium over an 8 day culture period and significantly influenced the capacity of fatty acid synthesis and metabolism. PDK4, CYP2E1, and CYP7A1 genes associated with NAFLD and other liver diseases were all up-regulated, and the metabolic activity of CYP3A4 was significantly impaired. Excess FFAs also induced alterations in transporters and key enzymes in the lipid biosynthesis pathway. The TEF liver was used to test if an antisteatotic drug, Metformin, used in patients with NAFLD, would be able to provide effects paralleling those observed in some patients. Metformin treatment of the TEF liver model caused reduced cellular triglycerides, activated AMPK molecule, inhibited mTORC1 signaling pathway, which thus affected the synthesis and metabolism of FFAs. Overall, the TEF liver offers a stable and reproducible model to study the NAFLD development process and antisteatotic drug effects.

Sweat glands perform a vital thermoregulatory function in mammals. Like other skin components, they originate from epidermal progenitors. However, they have low regenerative potential in response to injury. We have established a sweat gland culture and expansion method using 3D organoids cultures. The epithelial cells derived from sweat glands in dermis of adult mouse paw pads were embedded into Matrigel and formed sweat gland organoids (SGOs). These organoids maintained remarkable stem cell features and demonstrated differentiation capacity to give rise to either sweat gland cells (SGCs) or epidermal cells. Moreover, the bipotent SGO-derived cells could be induced into stratified epidermis structures at the air−liquid interface culture in a medium tailored for skin epidermal cells in vitro. The SGCs embedded in Matrigel tailored for sweat glands formed epithelial organoids, which expressed sweat-gland-specific markers, such as cytokeratin (CK) 18 and CK19, aquaporin (AQP) 5 and αATP. More importantly, they had potential of regeneration of epidermis and sweat gland when they were transplanted into the mouse back wound and claw pad with sweat gland injury, respectively. In summary, we established and optimized culture conditions for effective generation of mouse SGOs. These cells are candidates to restore impaired sweat gland tissue as well as to improve cutaneous skin regeneration.