Cyclophosphamide disrupts hepatic sinusoidal endothelium and improves transplanted cell engraftment in rat liver

Abstract

To determine whether disruption of the hepatic sinusoidal endothelium will facilitate engraftment of transplanted cells, we treated Fischer 344 (F344) rats lacking dipeptidyl peptidase IV (DPPIV) activity with cyclophosphamide (CP). Electron microscopy showed endothelial injury within 6 hours following CP, and, after 24 and 48 hours, the endothelium was disrupted in most hepatic sinusoids. CP did not affect Kupffer cell function. Similarly, CP had no obvious effects on hepatocytes. Intrasplenic transplantation of F344 rat hepatocytes followed by their localization with DPPIV histochemistry showed 3-to 5-fold increases in the number of transplanted cells in CP-treated animals. Transplanted cells integrated in the liver parenchyma more rapidly in CPtreated animals, and hybrid bile canaliculi developed even 1 day after cell transplantation, which was not observed in control animals. To demonstrate whether improved cell engraftment translated into superior liver repopulation, recipient animals were conditioned with retrorsine and two-thirds partial hepatectomy (PH), which induces transplanted cell proliferation. CP treatment of these animals before cell transplantation significantly increased the number and size of transplanted cell foci. In conclusion, disruption of the hepatic sinusoidal endothelium was associated with accelerated entry and integration of transplanted cells in the liver parenchyma. These results provide insights into hepatocyte engraftment in the liver and will help in optimizing liver-directed cell therapy. ( T ransplanted hepatocytes integrate in the liver, survive throughout the life of animals, and express genes normally. 1-3 However, several days are required for transplanted cells to integrate in the liver parenchyma. 4 Moreover, transplanted cells do not proliferate significantly in the normal adult liver, 3 although, when proliferation and/or survival of native and transplanted cells are dissociated, transplanted hepatocytes can repopulate the liver extensively. [5][6][7][8][9][10] The possibility of therapeutic liver repopulation has been tested in several animal models with liver failure, genetic diseases, and metabolic deficiency states. [11][12][13][14] The swiftness with which transplanted cells engraft could be critical for liver repopulation. After injection into the portal system, transplanted cells lodge in hepatic sinusoids because of differences in the dimensions of these cells and sinusoids. 15 This is associated with changes in native hepatocytes, such as gamma-glutamyl transpeptidase activation and disruption of gap junctions. 16 The sinusoidal endothelium is disrupted 16 to 20 hours after transplantation, which provides transplanted cells access to the space of Disse. 4 Transplanted cells then translocate into the liver plate, with reconstitution of gap junctions and bile canaliculi over 3 to 7 days. However, delays in cell engraftment affect transplanted cell proliferation. In rats subjected to two-thirds partial hepatectomy (PH), which induces hepatic DNA synthesis within ...

Hepatocyte transplantation activates hepatic stellate cells with beneficial modulation of cell engraftment in the rat

“…15 Cell transplantation is associated with perturbations of additional liver cell compartments, such as those associated with ischemia-reperfu- sion injury, that is, Kupffer cell activation, and endothelial disruption, which increases the potential for cell-cell interactions. [1][2][3][4][5] Activation of HSC is associated early with increased desmin expression and cell cycle entry, which is in agreement with intense and widespread desmin expression in HSC within 3 days after cell transplantation. However, these changes were transient, because the number of desminpositive HSC declined within 7 days after cell transplantation.…”

“…[1][2][3][4][5] Using DPPIVϪ rats, we demonstrate here that hepatocyte transplantation partially activated HSC, including expression of growth factors and ECM-modifying matrix metalloproteinases (MMPs), which are largely produced in HSC. 7,8 Moreover, depletion of HSC interfered with cell engraftment.…”

Morphology of the bone marrow, spleen and liver during hematopoietic cell mobilization with cyclophosphamide in mice.

“…Although cyclophosphamide is regarded to be a hepatotoxic agent, the hepatocytes' morphology observed in light microscopy was not altered. However, Malhi et al [37] showed in electron microscopy experiments the endothelial injury just within 6 hours after CY treatment and the endothelium disorganization in most sinusoids was observed after 24 and 48 hours. In their studies, CY had no obvious effects on hepatocytes and Kupffers' cells [37].…”

“…However, Malhi et al [37] showed in electron microscopy experiments the endothelial injury just within 6 hours after CY treatment and the endothelium disorganization in most sinusoids was observed after 24 and 48 hours. In their studies, CY had no obvious effects on hepatocytes and Kupffers' cells [37]. In our experiment, we observed the increase in number of Kupffers' cells in zone III (central venous drainage) and zone II (intermediate region) on day 6. after CY administration.…”

Liver gene therapy: advances and hurdles

“…Hepatocyte engraftment could also be significantly increased: (i) by increasing the number of donor cells depositing in hepatic sinusoids using vasodilators; (ii) by disrupting the sinusoidal endothelial endothelium using drugs such as cyclosphamide; and (iii) by depleting macrophage/Kuppfer cells prior to hepatocyte transplantation using gadolinium chloride. 78,86,87 Other strategies were aimed at amplifying the hepatic mass of transplanted hepatocytes after they had integrated into the liver parenchyma. Partial hepatectomy and hepatocyte growth factor infusion were ineffective in increasing the transplanted hepatocyte mass, because both transplanted and host hepatocytes had been removed and/or responded equally to the regenerative stimuli.…”