A Critical Evaluation of Liver Pathology in Humans with Danon Disease and Experimental Correlates in a Rat Model of LAMP-2 Deficiency.

Danon disease is a genetic deficiency in lysosome-associated membrane protein 2 (LAMP-2), a highly glycosylated constituent of the lysosomal membrane and characterized by a cardiomyopathy, skeletal muscle myopathy, and cognitive impairment. Patients, however, often manifest hepatic abnormalities, but liver function has not been well evaluated and the syndrome is relatively uncommon. Hence, we have taken advantage of a rat that has been deleted of LAMP-2 to study the relative role of LAMP-2 on liver function. Interestingly, rats deficient in LAMP-2 develop a striking increase in serum alkaline phosphatase (ALP) and a decrease in bile flow compared with wild-type littermates. Importantly and by ultrastructural analysis, deficient rats manifest dilated canaliculi that lack microvilli with evidence of bile-containing bodies. Moreover, following bile duct ligation, LAMP-2-deficient rats develop rapid and severe evidence of advanced cholestasis, with an increase in serum bilirubin, as early as 6 h later. In wild-type control rats, multidrug resistance-associated protein 2 (Mrp2) normally concentrates at the bile canalicular membranes to secrete conjugated bilirubin into bile. However, in LAMP-2y/- rats, Mrp2 was detected in hepatocytes compared with other canalicular proteins including P-glycoproteins, dipeptidyl peptidase IV (CD26), and aminopeptidase (CD13). Our data further suggest that LAMP-2 interacts with the membrane cytoskeletal proteins radixin and F-actin in determining the localization of integral membrane proteins.

Induction of hepatocyte-like cells from human umbilical cord-derived mesenchymal stem cells by defined microRNAs.

Generating functional hepatocyte-like cells (HLCs) from mesenchymal stem cells (MSCs) is of great urgency for bio-artificial liver support system (BALSS). Previously, we obtained HLCs from human umbilical cord-derived MSCs by overexpressing seven microRNAs (HLC-7) and characterized their liver functions in vitro and in vivo. Here, we aimed to screen out the optimal miRNA candidates for hepatic differentiation. We sequentially removed individual miRNAs from the pool and examined the effect of transfection with remainder using RT-PCR, periodic acid-Schiff (PAS) staining and low-density lipoprotein (LDL) uptake assays and by assessing their function in liver injury models. Surprisingly, miR-30a and miR-1290 were dispensable for hepatic differentiation. The remaining five miRNAs (miR-122, miR-148a, miR-424, miR-542-5p and miR-1246) are essential for this process, because omitting any one from the five-miRNA combination prevented hepatic trans-differentiation. We found that HLCs trans-differentiated from five microRNAs (HLC-5) expressed high level of hepatic markers and functioned similar to hepatocytes. Intravenous transplantation of HLC-5 into nude mice with CCl4 -induced fulminant liver failure and acute liver injury not only improved serum parameters and their liver histology, but also improved survival rate of mice in severe hepatic failure. These data indicated that HLC-5 functioned similar to HLC-7 in vitro and in vivo, which have been shown to resemble hepatocytes. Instead of using seven-miRNA combination, a simplified five-miRNA combination can be used to obtain functional HLCs in only 7 days. Our study demonstrated an optimized and efficient method for generating functional MSC-derived HLCs that may serve as an attractive cell alternative for BALSS.