The route of administration of implanted cells may affect the outcome of cell therapy by directing cell migration to the damaged site. However, the question of the relationship between the route of administration, the efficacy of colonisation of a given organ, and the efficacy of cell therapy has not been resolved. The aim of the study was to localise transplanted intravenously and intraperitoneally human amniotic epithelial cells (hAECs) in the tissues of mice, both healthy and injured, in an animal experimental model of acute liver failure (ALF). Mice intoxicated with D-Galactosamine (D-GalN) at a dose of 150 mg/100 g body weight received D-GalN alone or with a single dose of hAECs administered by different routes. Subsequently, at 6, 24, and 72 h after D-GaIN administration and at 3, 21, and 69 h after hAEC administration, lungs, spleen, liver, and blood were collected from recipient mice. The degree of liver damage and regeneration was assessed based on biochemical blood parameters, histopathological evaluation (H&E staining), and immunodetection of proliferating (Ki67+) and apoptotic (Casp+) cells. The biodistribution of the administered cells was based on immunohistochemistry and the identification of human DNA. It has been shown that after intravenous administration, in both healthy and intoxicated mice, most of the transplanted hAECs were found in the lungs, while after intraperitoneal administration, they were found in the liver. We concluded that a large number of hAECs implanted in the lungs following intravenous administration can exert a therapeutic effect on the damaged liver, while the regenerative effect of intraperitoneally injected hAECs on the liver was very limited due to the relatively lower efficiency of cell engraftment.

In humans, chronic liver disease (CLD) is a serious clinical condition with many life-threatening complications. Currently, there is no therapy to stop or slow down the progression of liver fibrosis. Experimental mouse models of CLD, induced by repeated intraperitoneal injections of carbon tetrachloride (CCL4) and D-galactosamine (D-GalN), can be used to evaluate therapies that cannot be performed in humans. A major drawback of these animal models is the different dynamics of liver fibrosis progression depending on the animal strain, administered hepatotoxin, its dose, duration of intoxication, and frequency of injections. The aim of this study was to describe and compare the dynamics of progression of pathological changes in the BALB/c mouse and Sprague Dawley rat models of CLD induced by CCl4 and D-GalN. We defined the onset and duration of these changes and suggested the optimal time for therapeutic intervention in the analyzed CLD models.
CLD was induced by repeated intraperitoneal injection of CCl4 in mice (12.5 μL/100 g bw every 5 days) and rats (25-100 μL/100 g bw twice a week) and D-GalN in mice (75 mg/100 g bw twice a week) and rats (25 mg/100 g bw twice a week). Blood and liver samples were collected at weeks 2, 4, 6, 8, 10, and 12 of intoxication. Liver injury and its progression were assessed by using complete blood count and liver function blood tests as well as by analyzing histopathological changes, including fibrosis, proliferation activity, apoptosis, stellate cell activation, and gene expression.
In mice and rats treated with CCl4, early fibrosis was observed in most pericentral areas from week 2 to 4 of intoxication. Established fibrosis developed in both rats and mice at week 6 of intoxication. Incomplete cirrhosis, defined as the presence of occasional cirrhotic nodules, was observed in rats at week 12 of intoxication. The dynamics of liver fibrosis in CCl4-treated animals were greater than in the D-GalN groups. In D-GalN-intoxicated rats and mice, the first signs of liver fibrosis were observed at weeks 4 and 10 of intoxication, respectively. The rats developed early fibrosis after 8 weeks of D-GalN intoxication. The progression of collagen deposition was accompanied by histological changes and alteration of certain genes and blood liver parameters.
The dynamics of liver fibrosis in CCl4 treated rodents is greater than in the D-GalN treated ones. In the CCl4 models, two appropriate times for therapeutic intervention are indicated, which to varying degrees reflect the real clinical situation and may potentially differ in the obtained results: early intervention before week 4 of intoxication (early fibrosis) and late intervention after week 8 of intoxication (when signs of established fibrosis are present). Rodent models of D-GalN-induced fibrosis are not recommended due to the long incubation period and weak toxic effect.