Neuro-Chikungunya: Acute Transverse Myelopathy Associated with Chikungunya Virus Infection

Chikungunya is an arboviral infection caused by Chikungunya virus, an RNA virus from Togaviridae family.1 The disease manifests as fever, rash and characteristically, with arthralgia.1 Chikungunya is strongly believed to have neurotropism but has not been well studied like other neurotropic arboviruses.2 Encephalitis appears to represent the most common clinical manifestation6 and occurs either simultaneously or within few days of onset of systemic symptoms, during the period of viremia. A delay of more than two weeks has been reported with other complications like myelitis, Guillian Barre syndrome and optic neuritis. This case describes the clinical, serological, neuroimaging and CSF findings of Chikungunya induced acute transverse myelitis in a 13 years old male patient who responded to steroid treatment. It is a relatively unknown and very rare complication of Chikungunya virus infection during outbreak of Chikungunya infection in September 2016.

Analysis of Hepatocyte Distribution and Survival in Vascular Beds with Cells Marked by 99mTC or Endogenous Dipeptidyl Peptidase IV Activity

Knowledge of the kinetics of cell distribution in vascular beds will help optimize engraftment of transplanted hepatocytes. To noninvasively localize transplanted cells in vivo, we developed conditions for labeling rat hepatocytes with 99mTc–pertechnetate. The incorporated 99mTc was bound to intracellular proteins and did not impair cell viability. When 99mTc hepatocytes were intrasplenically injected into normal rats, cells entered liver sinusoids with time–activity curves demonstrating instantaneous cell translocations. 99mTc activity in removed organs was in liver or spleen, and lungs showed little activity. However, when cells were intrasplenically transplanted into rats with portasystemic collaterals, 99mTc appeared in both liver sinusoids and pulmonary alveolar capillaries. To further localize cells, we transplanted DPPIV+ F344 rat hepatocytes into syngeneic DPPIV – recipients. Histochemical staining for DPPIV activity demonstrated engraftment of intrasplenically transplanted cells in liver parenchyma. In contrast, when 99mTc hepatocytes were injected into a peripheral vein, cells were entrapped in pulmonary capillaries but were subsequently broken down with redistribution of 99mTc activity elsewhere. Intact DPPIV+ hepatocytes were identified in lungs, whereas only cell fragments were present in liver, spleen, or kidneys. These findings indicate that although the pulmonary vascular bed offers advantages of easy accessibility and a relatively large capacity, significant early cell destruction is an important limitation.

Human SeruM Albumin Microspheres Approximate Initial Organ-Specific Biodistributions of Transplanted Hepatocytes and Are Effective Cell Surrogates for Safety Studies

Liver repopulation with transplanted hepatocytes will generate novel cell-based therapies, although translocation of transplanted cells into lungs through portasystemic shunts has the potential for embolic complications. To facilitate safety analysis of hepatocyte transplantation, we wished to obtain effective cell surrogates and analyzed biodistributions of similarly sized 99mTc-labeled human serum albumin microspheres and rat hepatocytes. Image analysis with dual 99mTc and 111In labels indicated that cells and microspheres were similarly distributed in the liver when injected into normal rats via the spleen. Also, their distributions were similar when injected via a femoral vein or the superior mesenteric vein with cells and microspheres localizing in lungs or liver, respectively. Upon intraportal injection in rats with portal hypertension, microspheres localized in both liver and lungs, consistent with portasystemic shunting. These data demonstrate that human serum albumin microspheres are effective cell surrogates for approximating the safety of hepatocyte transplantation and should be clinically useful.

Human immunodeficiency virus-associated nephropathy

Human immunodeficiency virus-associated nephropathy (HIVAN) is a clinicopathological entity characterised by proteinuria, rapidly developing azotemia and histologically by collapsig variant of focal and segmental glomerulosclerosis with acute tubular necrosis and mild interstitial inflammation. Untreated, it may result in end stage renal disease (ESRD) in as little as four months. The incidence of HIVAN continues to increase and is the single most common cause of chronic renal disease in HIV-1 seropositive patients. It affects predominantly black individuals. Exact pathogenesis is still not clear but a great deal of progress has been made in the recent past by studies on transgenic mouse model, renal cell cultures and from study of human biopsy material. Current considerations revolve around the role of HIV or protein in renal epithelium and the effects of cytokines, including transforming growth factor-beta and basic fibroblast growth factor on renal structures. Different modalities of treatment with corticosteroids, zidovudine or angiotensin converting enzyme inhibitors have been tried with modest success.

Gallbladder vasculitis associated with type-1 cryoglobulinemia

A patient with type I cryoglobulinemia and monoclonal gammopathy of uncertain significance was found to have acute gallbladder vasculitis. The most prominent manifestation was upper abdominal pain in the setting of normal liver tests. An abdominal ultrasound demonstrated a thickened gallbladder wall, along with gallstones. HIDA scanning showed a nonfunctioning gallbladder with an edematous and thickened wall. There was characteristic leukocytoclastic vasculitis affecting the gallbladder. The patient recovered uneventfully subsequent to cholecystectomy. Gallbladder vasculitis should be considered in patients with unexplained upper abdominal pain and systemic vasculitis.

Cell transplantation causes loss of gap junctions and activates GGT expression permanently in host liver

Cell transplantation into hepatic sinusoids, which is necessary for liver repopulation, could cause hepatic ischemia. To examine the effects of cell transplantation on host hepatocytes, we transplanted Fisher 344 rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient rats. Within 24 h of cell transplantation, areas of ischemic necrosis, along with transient disruption of gap junctions, appeared in the liver. Moreover, host hepatocytes expressed gamma-glutamyl transpeptidase (GGT) extensively, which was observed even 2 years after cell transplantation. GGT expression was not associated with alpha-fetoprotein activation, which is present in progenitor cells. Increased GGT expression was apparent after transplantation of nonparenchymal cells and latex beads but not after injection of saline, fragmented hepatocytes, hepatocyte growth factor, or turpentine. Some host hepatocytes exhibited apoptosis, as well as DNA synthesis, between 24 and 48 h after cell transplantation. Changes in gap junctions, GGT expression, DNA synthesis, and apoptosis after cell transplantation were prevented by vasodilators. The findings indicated the onset of ischemic liver injury after cell transplantation. These hepatic perturbations must be considered when transplanted cells are utilized as reporters for biological studies.

Transplanted reporter cells help in defining onset of hepatocyte proliferation during the life of F344 rats

Transplanted hepatocytes integrate in the liver parenchyma and exhibit gene expression patterns that are similar to adjacent host hepatocytes. To determine the fate of genetically marked hepatocytes in the context of hepatocellular proliferation throughout the rodent life span, we transplanted Fischer 344 (F344) rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient rats. The proliferative activity in transplanted hepatocytes was studied in animals ranging in age from a few days to 2 yr. Transplanted hepatocytes proliferated during liver development between 1 and 6 wk of age, each dividing an estimated two to five times. DNA synthesis in occasional cells was demonstrated by localizing bromodeoxyuridine incorporation. There was no evidence for transplanted cell proliferation between 6 wk and 1 yr of age. Subsequently, transplanted cells proliferated again, with increased sizes of transplanted cell clusters at 18 and 24 mo of age. The proliferative activity of transplanted cells was greater in rats entering senescence compared with during postnatal liver development. In old rats, some liver lobules were composed entirely of transplanted cells. We conclude that hepatocyte proliferation in the livers of very young and old F344 rats is regulated in a temporally determined, biphasic manner. The findings will be relevant to mechanisms concerning liver development, senescence, and oncogenesis, as well as to cell and gene therapy.

KATP channels regulate mitogenically induced proliferation in primary rat hepatocytes and human liver cell lines. Implications for liver growth control and potential therapeutic targeting

To determine whether K(ATP) channels control liver growth, we used primary rat hepatocytes and several human cancer cell lines for assays. K(ATP) channel openers (minoxidil, cromakalim, and pinacidil) increased cellular DNA synthesis, whereas K(ATP) channel blockers (quinidine and glibenclamide) attenuated DNA synthesis. The channel inhibitor glibenclamide decreased the clonogenicity of HepG2 cells without inducing cytotoxicity or apoptosis. To demonstrate the specificity of drugs for K(+) channels, whole-cell patch-clamp recordings were made. Hepatocytes revealed K(+) currents with K(ATP) channel properties. These K(+) currents were augmented by minoxidil and pinacidil and attenuated by glibenclamide as well as tetraethylammonium, in agreement with established responses of K(ATP) channels. Reverse transcription of total cellular RNA followed by polymerase chain reaction showed expression of K(ATP) channel-specific subunits in rat hepatocytes and human liver cell lines. Calcium fluxes were unperturbed in glibenclamide-treated HepG2 cells and primary rat hepatocytes following induction with ATP and hepatocyte growth factor, respectively, suggesting that the effect of K(ATP) channel activity upon hepatocyte proliferation was not simply due to indirect modulation of intracellular calcium. The regulation of mitogen-related hepatocyte proliferation by K(ATP) channels advances our insights into liver growth control. The findings have implications in mechanisms concerning liver development, regeneration, and oncogenesis.

Transplanted hepatocytes engraft, survive, and proliferate in the liver of rats with carbon tetrachloride-induced cirrhosis

Repopulation of the cirrhotic liver with disease-resistant hepatocytes could offer novel therapies, as well as systems for biological studies. Establishing whether transplanted hepatocytes can engraft, survive, and proliferate in the cirrhotic liver is a critical demonstration. Dipeptidyl peptidase IV-deficient F344 rats were used to localize transplanted hepatocytes isolated from the liver of syngeneic normal F344 rats. Cirrhosis was induced by administration of carbon tetrachloride with phenobarbitone and these drugs were withdrawn prior to cell transplantation. Cirrhotic rats showed characteristic hepatic histology, as well as significant portosystemic shunting. When hepatocytes were transplanted via the spleen, cells were distributed immediately in periportal areas, fibrous septa, and regenerative nodules of the cirrhotic liver. Although some transplanted cells translocated into pulmonary capillaries, this was not deleterious. At 1 week, transplanted cells were fully integrated in the liver parenchyma, along with expression of glucose-6-phosphatase and glycogen as reporters of hepatic function. Transplanted cells proliferated in the liver of cirrhotic animals and survived indefinitely. At 1 year, transplanted hepatocytes formed large clusters containing several-fold more cells than normal control animals, which was in agreement with increased cell turnover in the cirrhotic rat liver. The findings indicate that the cirrhotic liver can be repopulated with functionally intact hepatocytes that are capable of proliferating. Liver repopulation using disease-resistant hepatocytes will be applicable in chronic conditions, such as viral hepatitis or Wilson's disease.

Transplanted hepatocytes engraft, survive, and proliferate in the liver of rats with carbon tetrachloride-induced cirrhosis

Repopulation of the cirrhotic liver with disease-resistant hepatocytes could offer novel therapies, as well as systems for biological studies. Establishing whether transplanted hepatocytes can engraft, survive, and proliferate in the cirrhotic liver is a critical demonstration. Dipeptidyl peptidase IV-deficient F344 rats were used to localize transplanted hepatocytes isolated from the liver of syngeneic normal F344 rats. Cirrhosis was induced by administration of carbon tetrachloride with phenobarbitone and these drugs were withdrawn prior to cell transplantation. Cirrhotic rats showed characteristic hepatic histology, as well as significant portosystemic shunting. When hepatocytes were transplanted via the spleen, cells were distributed immediately in periportal areas, fibrous septa, and regenerative nodules of the cirrhotic liver. Although some transplanted cells translocated into pulmonary capillaries, this was not deleterious. At 1 week, transplanted cells were fully integrated in the liver parenchyma, along with expression of glucose-6-phosphatase and glycogen as reporters of hepatic function. Transplanted cells proliferated in the liver of cirrhotic animals and survived indefinitely. At 1 year, transplanted hepatocytes formed large clusters containing several-fold more cells than normal control animals, which was in agreement with increased cell turnover in the cirrhotic rat liver. The findings indicate that the cirrhotic liver can be repopulated with functionally intact hepatocytes that are capable of proliferating. Liver repopulation using disease-resistant hepatocytes will be applicable in chronic conditions, such as viral hepatitis or Wilson's disease.

Integration and proliferation of transplanted cells in hepatic parenchyma following D-galactosamine-induced acute injury in F344 rats

To determine whether liver repopulation with cell transplantation could be of therapeutic value in acute hepatic failure, it is necessary to establish the fate of transplanted hepatocytes. This study used dipeptidyl peptidase IV-deficient F344 rats as recipients to analyse the engraftment and proliferation of transplanted hepatocytes. Syngeneic hepatocytes were transplanted intrasplenically 24-30 h after induction of liver injury by D-galactosamine (GalN). Portosystemic shunting was analysed with 99m-Tc-labelled albumin microspheres. GalN-treated rats showed characteristic hepatic necrosis, inflammation, gamma-glutamyl transpeptidase activation, and regenerative activity, without increased portosystemic shunting (>99% 99m-Tc activity was in the liver in normal and GalN-treated rats). Transplanted cells entered hepatic sinusoids promptly and were observed in liver plates at 48 h. The number of transplanted cells increased in GalN-treated rats by approximately seven-fold (range two- to 12-fold), along with evidence for DNA synthesis between 3 and 14 days after cell transplantation and greater prevalence of larger transplanted cell clusters. These findings indicate that the liver can be safely repopulated in animals with acute liver failure, although the time required for regenesis of plasma membrane structures and proliferation in transplanted hepatocytes will need to be considered in developing therapeutic strategies.

Radionuclide analysis of drug-induced blood-pool changes in liver and other organs

Although it is possible to repopulate the animal liver with transplanted hepatocytes, the success of such transplants depends, in part, on the number of transplanted cells that enter the hepatic sinusoids. Pharmacologic alteration of hepatic vascular tone, and hence blood volume, can increase the number of cells that are successfully transplanted. Although analysis of changes in vascular beds is helpful for developing strategies for cell transplantation, convenient methods to analyze such changes are lacking. The objective of this study was to determine whether 99mTc-labeled red blood cells could be used to reveal pharmacologically induced blood pool changes in various organs.

METHODS

F344 rats were injected with syngeneic labeled red blood cells and subjected to blood pool analysis with gamma camera imaging. Animals were treated with phenylephrine, phentolamine, labetalol, and nitroglycerine. To correlate hepatic blood pool changes with structural alterations at the vascular level, microspheres were injected into the portal circulation of these animals.

RESULTS

Phenylephrine significantly increased cardiac and pulmonary blood pools, findings in agreement with its alpha-adrenergic effects. Phentolamine increased the hepatic, splenic, and pulmonary blood pools, whereas labetalol increased only the pulmonary blood pool. Nitroglycerine increased both hepatic and splenic blood pools. Prior administration of phentolamine, labetalol, and nitroglycerine prevented the phenylephrine-induced changes. When microspheres were injected into the portal circulation after nitroglycerine administration, they penetrated more distal locations in the liver lobule.

CONCLUSION

These data indicate that it is possible, using radionuclide methods, to noninvasively show pharmacologically induced hemodynamic changes. This finding is potentially useful for studying hepatic physiology and may also have applications for cell therapy.

Integration and proliferation of transplanted cells in hepatic parenchyma following D-galactosamine-induced acute injury in F344 rats

To determine whether liver repopulation with cell transplantation could be of therapeutic value in acute hepatic failure, it is necessary to establish the fate of transplanted hepatocytes. This study used dipeptidyl peptidase IV-deficient F344 rats as recipients to analyse the engraftment and proliferation of transplanted hepatocytes. Syngeneic hepatocytes were transplanted intrasplenically 24-30 h after induction of liver injury by D-galactosamine (GalN). Portosystemic shunting was analysed with 99m-Tc-labelled albumin microspheres. GalN-treated rats showed characteristic hepatic necrosis, inflammation, gamma-glutamyl transpeptidase activation, and regenerative activity, without increased portosystemic shunting (>99% 99m-Tc activity was in the liver in normal and GalN-treated rats). Transplanted cells entered hepatic sinusoids promptly and were observed in liver plates at 48 h. The number of transplanted cells increased in GalN-treated rats by approximately seven-fold (range two- to 12-fold), along with evidence for DNA synthesis between 3 and 14 days after cell transplantation and greater prevalence of larger transplanted cell clusters. These findings indicate that the liver can be safely repopulated in animals with acute liver failure, although the time required for regenesis of plasma membrane structures and proliferation in transplanted hepatocytes will need to be considered in developing therapeutic strategies.

Partial hepatectomy-induced polyploidy attenuates hepatocyte replication and activates cell aging events

In understanding mechanisms of liver repopulation with transplanted hepatocytes, we studied the consequences of hepatic polyploidization in the two-thirds partial hepatectomy model of liver regeneration. Liver repopulation studies using genetically marked rodent hepatocytes showed that the number of previously transplanted hepatocytes did not increase in the liver with subsequential partial hepatectomy. In contrast, recipients undergoing partial hepatectomy before cells were transplanted showed proliferation in transplanted hepatocytes, with kinetics of DNA synthesis differing in transplanted and host hepatocytes. Also, partial hepatectomy caused multiple changes in the rat liver, including accumulation of polyploid hepatocytes along with prolonged depletion of diploid hepatocytes, as well as increased senescence-associated beta-galactosidase and p21 expression. Remnant hepatocytes in the partially hepatectomized liver showed increased autofluorescence and cytoplasmic complexity on flow cytometry, which are associated with lipofuscin accumulation during cell aging, and underwent apoptosis more frequently. Moreover, hepatocytes from the partially hepatectomized liver showed attenuated proliferative capacity in cell culture. These findings were compatible with decreased proliferative potential of hepatocytes experiencing partial hepatectomy compared with hepatocytes from the unperturbed liver. Attenuation of proliferative capacity and other changes in hepatocytes experiencing partial hepatectomy offer novel perspectives concerning liver regeneration in the context of cell ploidy.

Transplanted hepatocytes proliferate differently after CCl4 treatment and hepatocyte growth factor infusion

To understand regulation of transplanted hepatocyte proliferation in the normal liver, we used genetically marked rat or mouse cells. Hosts were subjected to liver injury by carbon tetrachloride (CCl4), to liver regeneration by a two-thirds partial hepatectomy, and to hepatocellular DNA synthesis by infusion of hepatocyte growth factor for comparative analysis. Transplanted hepatocytes were documented to integrate in periportal areas of the liver. In response to CCl4 treatments after cell transplantation, the transplanted hepatocyte mass increased incrementally, with the kinetics and magnitude of DNA synthesis being similar to those of host hepatocytes. In contrast, when cells were transplanted 24 h after CCl4 administration, transplanted hepatocytes appeared to be injured and most cells were rapidly cleared. When hepatocyte growth factor was infused into the portal circulation either subsequent to or before cell transplantation and engraftment, transplanted cell mass did not increase, although DNA synthesis rates increased in cultured primary hepatocytes as well as in intact mouse and rat livers. These data suggested that procedures causing selective ablation of host hepatocytes will be most effective in inducing transplanted cell proliferation in the normal liver. The number of transplanted hepatocytes was not increased in the liver by hepatocyte growth factor administration. Repopulation of the liver with genetically marked hepatocytes can provide effective reporters for studying liver growth control in the intact animal.

Entry and integration of transplanted hepatocytes in rat liver plates occur by disruption of hepatic sinusoidal endothelium

To establish the process by which transplanted cells integrate into the liver parenchyma, we used dipeptidyl peptidase IV-deficient F344 rats as hosts. On intrasplenic injection, transplanted hepatocytes immediately entered liver sinusoids, along with attenuation of portal vein radicles on angiography. However, a large fraction of transplanted cells (>70%) was rapidly cleared from portal spaces by phagocyte/macrophage responses. On the other hand, transplanted hepatocytes entering the hepatic sinusoids showed superior survival. These cells translocated from sinusoids into liver plates between 16 and 20 hours after transplantation, during which electron microscopy showed disruption of the sinusoidal endothelium. Interestingly, production of vascular endothelial growth factor was observed in hepatocytes before endothelial disruptions. Portal hypertension and angiographic changes resulting from cell transplantation resolved promptly. Integration of transplanted hepatocytes in the liver parenchyma required cell membrane regenesis, with hybrid gap junctions and bile canaliculi forming over 3 to 7 days after cell transplantation. We propose that strategies to deposit cells into distal hepatic sinusoids, to disrupt sinusoidal endothelium for facilitating cell entry into liver plates, and to accelerate cell integrations into liver parenchyma will advance applications of hepatocyte transplantation.

Rapid clearance of transplanted hepatocytes from pulmonary capillaries in rats indicates a wide safety margin of liver repopulation and the potential of using surrogate albumin particles for safety analysis

BACKGROUND/AIMS

Applications of liver repopulation by hepatocyte transplantation require analysis of cell biodistributions, particularly when portasystemic shunting coexists. The aims of this study were to determine the fate of hepatocytes transplanted into the pulmonary vascular bed and to examine whether cell biodistributions could be approximated by convenient surrogates.

METHODS

Rat hepatocytes and macroaggregated serum albumin particles of similar sizes were injected into the portal and pulmonary vascular beds of rats, followed by biodistribution, survival and function analyses.

RESULTS

Although functionally intact, virtually all hepatocytes were cleared from the pulmonary capillaries within 24 h. Serum albumin levels increased minimally in Nagase analbuminemic rats with or without portacaval shunting to enhance delivery of portal factors to transplanted cells in lungs. Despite intravenous injection of hepatocytes approaching >1x10(9) cells in humans, the hemodynamic changes were limited to transient increases in right atrial pressures. The hepatocyte distributions in specific vascular beds were largely reproduced by macroaggregated human serum albumin particles.

CONCLUSIONS

Incidental intrapulmonary cell translocations during liver repopulation will have a wide safety margin. Use of macroaggregated serum albumin particles as surrogates for initial short-term biodistribution and safety analysis will advance hepatocyte transplantation, as the cost of GLP-certified laboratories and consumption of scarce donor livers will be avoided.

Differentiation-specific regulation of transgene expression in a diploid epithelial cell line derived from the normal F344 rat liver

To establish the differentiation potential of progenitor cells, non-parenchymal epithelial cells from the F344 rat liver (FNRL cells) were studied. These cells reacted with the OV-6 antibody marker of oval cells, but were negative for hepatocyte markers (albumin, transferrin, glycogen, glucose-6-phosphatase, H4 antigen), biliary markers (gamma glutamyl transpeptidase, cytokeratin-19), and alpha-fetoprotein, although exposure to sodium butyrate induced nascent albumin and alpha-fetoprotein mRNA transcription. When stably transduced, FNRL cells expressed a retroviral promotor-driven lacZ reporter in vitro, similar to transgene expression in hepatocyte-derived HepG2 cells. However, lacZ expression in FNRL cells was rapidly extinguished in intact animals, whereas the reporter remained active in HepG2 cells. Transplanted FNRL cells showed copious glucose-6-phosphatase expression; however, the cell differentiation programme remained incomplete, despite two-thirds partial hepatectomy, D-galactosamine treatment or bile duct ligation. Interestingly, lacZ expression resumed in cultures of FNRL cells explanted from recipients. Moreover, lacZ expression was down-regulated by gamma-interferon in FNRL cells, without affecting lacZ activity in HepG2 cells. The data indicate that although subpopulations of oval cells may not fully differentiate into mature hepatocytes, these cells might serve critical functions, such as glucose utilization, and help survival after liver injury. Also, introduced genes may be regulated in progenitor cells at multiple levels, including by interactions between regulatory sequences, differentiation-specific cellular factors, and extracellular signals; in vivo studies are thus especially important for analysing gene regulation in progenitor cells.

Position-specific gene expression in the liver lobule is directed by the microenvironment and not by the previous cell differentiation state

Mechanisms directing position-specific liver gene regulation are incompletely understood. To establish whether this aspect of hepatic gene expression is an inveterate phenomenon, we used transplanted hepatocytes as reporters in dipeptidyl peptidase IV-deficient F344 rats. After integration in liver parenchyma, the position of transplanted cells was shifted from periportal to perivenous areas by targeted hepatic ablations with carbon tetrachloride. In controls, transplanted cells showed greater glucose-6-phosphatase and lesser glycogen content in periportal areas. This pattern was reversed when transplanted cells shifted from periportal to perivenous areas. Transplanted hepatocytes in perivenous areas exhibited inducible cytochrome P450 activity, which was deficient in periportal hepatocytes. Moreover, cytochrome P450 activity was rapidly extinguished in activated hepatocytes when these cells were transplanted into the nonpermissive liver of suckling rat pups. In cells isolated from the normal F344 rat liver, cytochrome P450 inducibility was originally greater in perivenous hepatocytes; however, periportal cells rapidly acquired this facility in culture conditions. These findings indicate that the liver microenvironment exerts supremacy over prior differentiation state of cells in directing position-specific gene expression. Therefore, persistence of specialized hepatocellular function will require interactions with regulatory signals and substrate availability, which bears upon further analysis of liver gene regulation, including in progenitor and/or stem cells.

Fractionation of rat hepatocyte subpopulations with varying metabolic potential, proliferative capacity, and retroviral gene transfer efficiency

The liver contains hepatocytes with varying ploidy and gene expression. To isolate cells on the basis of ploidy for analyzing mechanisms concerning cell proliferation and differentiation, we used Percoll gradients to separate F344 rat hepatocyte subpopulations. Specific fractions were enriched in polyploid (H2 fraction) or diploid (H3 and H4 fractions) hepatocytes containing glycogen and glucose-6-phosphatase. H4 cells were relatively smaller with greater nuclear/cytoplasmic ratios, less complex cytoplasm, and higher serum albumin or ceruloplasmin biosynthetic rates. H2 fraction cells were larger with lesser nuclear/cytoplasmic ratio, more complex cytoplasm, and more cytochrome P450 activity. Phenotypic marking showed that H4 cells originated in zone one and H2 cells in zones two or three of the liver lobule. H4 cells showed much greater mitogenic responsiveness to human hepatocyte growth factor. Retroviral gene transfer, which requires both viral receptors and cellular DNA synthesis, was significantly more efficient in H4 cells. The findings indicated that small diploid and large polyploid hepatocytes show unique biological differences. The ability to isolate hepatocytes of varying maturity is relevant for mechanisms concerning liver growth control and hepatic gene expression.

Human serum albumin microspheres approximate initial organ-specific biodistributions of transplanted hepatocytes and are effective cell surrogates for safety studies

Liver repopulation with transplanted hepatocytes will generate novel cell-based therapies, although translocation of transplanted cells into lungs through portasystemic shunts has the potential for embolic complications. To facilitate safety analysis of hepatocyte transplantation, we wished to obtain effective cell surrogates and analyzed biodistributions of similarly sized 99mTc-labeled human serum albumin microspheres and rat hepatocytes. Image analysis with dual 99mTc and 111In labels indicated that cells and microspheres were similarly distributed in the liver when injected into normal rats via the spleen. Also, their distributions were similar when injected via a femoral vein or the superior mesenteric vein with cells and microspheres localizing in lungs or liver, respectively. Upon intraportal injection in rats with portal hypertension, microspheres localized in both liver and lungs, consistent with portasystemic shunting. These data demonstrate that human serum albumin microspheres are effective cell surrogates for approximating the safety of hepatocyte transplantation and should be clinically useful.

Analysis of hepatocyte distribution and survival in vascular beds with cells marked by 99mTC or endogenous dipeptidyl peptidase IV activity

Knowledge of the kinetics of cell distribution in vascular beds will help optimize engraftment of transplanted hepatocytes. To noninvasively localize transplanted cells in vivo, we developed conditions for labeling rat hepatocytes with 99mTc-pertechnetate. The incorporated o9mTc was bound to intracellular proteins and did not impair cell viability. When 99mTc hepatocytes were intrasplenically injected into normal rats, cells entered liver sinusoids with time-activity curves demonstrating instantaneous cell translocations. 99mTc activity in removed organs was in liver or spleen, and lungs showed little activity. However, when cells were intrasplenically transplanted into rats with portasystemic collaterals, 99mTc appeared in both liver sinusoids and pulmonary alveolar capillaries. To further localize cells, we transplanted DPPIV+ F344 rat hepatocytes into syngeneic DPPIV-recipients. Histochemical staining for DPPIV activity demonstrated engraftment of intrasplenically transplanted cells in liver parenchyma. In contrast, when 99mTc hepatocytes were injected into a peripheral vein, cells were entrapped in pulmonary capillaries but were subsequently broken down with redistribution of 99mTc activity elsewhere. Intact DPPIV+ hepatocytes were identified in lungs, whereas only cell fragments were present in liver, spleen, or kidneys. These findings indicate that although the pulmonary vascular bed offers advantages of easy accessibility and a relatively large capacity, significant early cell destruction is an important limitation.

Efficacy and safety of repeated hepatocyte transplantation for significant liver repopulation in rodents

BACKGROUND & AIMS

Significant liver repopulation by hepatocyte transplantation will advance clinical applications. The aim of this study was to test the hypothesis that translocation of transplanted cells into liver plates will allow repeated cell transplantation for increasing the transplanted hepatocyte mass.

METHODS

Hepatocytes were transplanted via spleen from either F344 rats into syngeneic recipients deficient in dipeptidyl peptidase IV or from transgenic hepatitis B surface antigen-producing G26 mice with hepatitis B virus into nontransgenic congeneic recipients. Portosystemic shunting was shown by radiological methods.

RESULTS

Repeated hepatocyte transplantation led to progressively increased liver repopulation. Transplantation of 1.75 x 10(8) hepatocytes in three divided doses repopulated more than an estimated 5% of the host rat liver, with 3.8 x 10(6) +/- 0.1 x 10(6) transplanted cells/cm3 liver. This was a tenfold or threefold mean increase in transplanted cell number compared with recipients of 2.0 x 10(7) or 7.5 x 10(7) cells transplanted in single sessions, respectively (P < 0.001). Repeated hepatocyte transplantation interfered with neither cell integrations in liver parenchyma nor secretory function of transplanted cells. Portal hypertension, portasystemic collaterals, or intrahepatic shunting were not observed in cell recipients.

CONCLUSIONS

Repeated transplantation of hepatocytes in large numbers is safe and effective and should advance strategies for liver repopulation.

Studies of liver repopulation using the dipeptidyl peptidase IV-deficient rat and other rodent recipients: cell size and structure relationships regulate capacity for increased transplanted hepatocyte mass in the liver lobule

The feasibility of liver repopulation with hepatocytes has been shown, although clinical applications demand significant hepatic replacement. To show whether portal vascular bed in large animals could accomodate a greater cell number, we analyzed liver repopulation in syngeneic Fischer 344 rats deficient in dipeptidyl peptidase IV. This system allowed localization of transplanted normal hepatocytes in liver or various ectopic sites, as well as dual studies for analysis of gene expression. Interestingly, the product of a dipeptidyl peptidase IV substrate inactivated bile canalicular adenosine triphosphatase (ATPase) activity in normal but not in dipeptidyl peptidase IV-deficient rats, which allowed localization of dipeptidyl peptidase IV-deficient hepatocytes in normal rat liver for additional reversed transplantation systems. Further studies with genetically marked cells showed that because of the size difference between hepatocytes and portal vein radicles, intrasplenically transplanted cells were distributed in periportal areas (zone 1) in mice, whereas in larger animals (rats or rabbits) cells were also distributed downstream to midlobular (zone 2) or perivenous (zone 3) areas. Transplantation of an escalating number of hepatocytes showed that adult rats tolerated intrasplenic injection of a large cell number in single sessions (up to 1 X 10(8), approximately 10% to 15% of the host hepatocyte mass). Morphometric analysis of recipient livers showed survival of a significantly greater cell number with incorporation in host liver plates. At 4 weeks, transplantation of 2 x 10(7) hepatocytes into adult rats led to a survival of 1.4 +/- 1.0 x 10(6) transplanted cells/cm3 liver, whereas after transplantation of 5 x 10(7) cells or 7.5 x 10(7) cells, the number of surviving transplanted cells in the liver significantly increased to 4.1 +/- 1.4 x 10(6) transplanted cells/cm3 liver (mean, 2.9-fold; P<.003) and 5.5 +/- 1.3 x 10(6) transplanted cells/cm3 liver (mean, 3.9-fold; P<.003), respectively. When cells were injected in greater numbers, transplanted hepatocytes retained normal function and produced more serum albumin or hepatitis B surface antigen in deficient hosts. These data indicate the feasibility in larger animals of significant liver repopulation with hepatocyte transplantation. Use of dipeptidyl peptidase IV-deficient rats should help further analysis of mechanisms in liver repopulation.

Integration of transplanted hepatocytes into host liver plates demonstrated with dipeptidyl peptidase IV-deficient rats

To analyze mechanisms of liver repopulation, we transplanted normal hepatocytes into syngeneic rats deficient in dipeptidyl peptidase IV activity. When isolated hepatocytes were injected into splenic pulp, cells promptly migrated into hepatic sinusoids. To examine whether transplanted hepatocytes entered liver plates and integrated with host hepatocytes, we analyzed sharing of hepatocyte-specific gap junctions and bile canaliculi. Colocalization studies showed gap junctions uniting adjacent transplanted and host hepatocytes in liver plates. Visualization of bile canalicular domains in transplanted and host hepatocytes with dipeptidyl peptidase IV and ATPase activities, respectively, demonstrated hybrid bile canaliculi, which excreted a fluorescent conjugated bile acid analogue. These results indicate that transplanted hepatocytes swiftly overcome mechanical barriers in hepatic sinusoids to enter liver plates and join host cells. Integration into liver parenchyma should physiologically regulate the function or disposition of transplanted hepatocytes and benefit applications such as gene therapy.

Celiac sprue and macroamylasemia: potential clinical and pathophysiological implications. Case study

In a patient with celiac sprue, abdominal complaints were ascribed to acute pancreatitis in the setting of hyperamylasemia and choledocholithiasis. The problem turned out to be macroamylasemia associated with elevated serum immunoglobulin A. The patient remained stable for 4 years with no specific intervention except gluten restriction. An association between celiac sprue or other malabsorptive states and macroamylasemia requires more study.

Transcatheter hepatocyte transplantation: preclinical studies of anatomic consequences in the portal vascular bed

RATIONALE AND OBJECTIVES

Intrasplenic transplantation deposits hepatocytes in host hepatic sinusoids with amelioration of chronic liver failure and genetic deficiency states. Because portal resistance can be altered by intrasinusoidal transplanted cells, we examined whether hepatocyte recipients would develop deleterious portal hypertension or portosystemic collaterals.

METHODS

Syngeneic hepatocytes in suspension were transplanted into recipient rats by transcatheter injection into the splenic parenchyma. Subjects included recipients of 2 x 10(7) hepatocytes representing approximately 3% of the host hepatic mass, recipients of 7.5 x 10(7) hepatocytes representing approximately 12.5% of the host hepatic mass, normal control rats, and positive control rats with portal hypertension induced by partial portal vein constriction. Portal pressures were recorded with a sensitive transducer, portosystemic collaterals were demonstrated with direct splenoportography, and survival of transplanted cells was determined with an endogenous dipeptidyl peptidase IV reporter gene.

RESULTS

In normal rats, the portal pressure was 6.25 +/- 1.9 mm Hg with no portosystemic collaterals. By contrast, portal pressures were significantly increased in portal vein-constricted rats, 20.7 +/- 3.9 mm Hg (P < 0.001), with extensive portosystemic collaterals. In hepatocyte recipients, portal hypertension observed during transcatheter cell injection but proved transient. When animals were examined up to 16 weeks after hepatocyte transplantation, portal pressures were in the normal range (after 2 x 10(7) cells, 7.5 x 2.6 mm Hg; after 7.5 x 10(7) cells, 9.5 +/- 4.2 mm Hg, P = not significant). No portosystemic collaterals developed in hepatocyte recipients at various times up to 8 months after transplantation. Transplanted hepatocytes expressing the reporter gene were present in recipients with assimilation in host hepatic cords.

CONCLUSION

Despite injection of a massive number of cells, transcatheter hepatocyte transplantation was devoid of any significant portal vascular alterations or toxicity in recipients. These findings are consistent with assimilation of transplanted hepatocytes into host hepatic cords and will facilitate therapeutic applications in metabolic diseases or acute liver failure.

Chloramphenicol resistant enteric fever

In recent times there have been several reports of chloramphenicol resistant enteric fever necessitating the use of other antimicrobial agents. Clinical profile of 15 chloramphenicol resistant patients of enteric fever was studied. Three such patients (20%) responded to chloramphenicol despite in vitro resistance to the drug. Hence chloramphenicol still remains the drug of first choice in enteric fever as a majority (68.4%--26 out of 38) of our bacteriologically proven enteric fever patients were cured by the drug. The remaining 12 cases responded satisfactorily to ciprofloxacin (46.7%), gentamicin (20%), and ofloxacin (13.3%). There was an increased incidence of complications among the 15 drug resistant cases as compared to 23 cases of chloramphenicol sensitive enteric fever observed during the same period.

Mitral stenosis and aortic regurgitation in rheumatoid arthritis

A patient of rheumatoid arthritis having mitral stenosis and aortic regurgitation is reported. Our findings are based on clinical and echocardiographic study.

Alcohol and Indian porphyrics

The role of alcohol as the precipitating factor in the induction of acute attacks of acute intermittent porphyria was studied in an Indian population. Thirty-four teetotal patients with acute intermittent porphyria, in remission, were given 60 ml of 30% ethanol. Except for two patients, all had negative Watson-Schwartz tests prior to the alcohol. Within 24 hours, the Watson-Schwartz test became positive in 16 of these 32 patients (50%). In 8 out of the 34 patients (23.5%) a clinical attack was precipitated, including both patients who had a positive Watson-Schwartz test prior to the alcohol. It was concluded that alcohol does precipitate an acute attack in a significant percentage of patients of Indian origin with acute intermittent porphyria. Patients already excreting porphobilinogen are at a greater risk of developing an acute attack on alcohol ingestion. This study is the first from India and probably first of its kind to be reported from any country.

Comparative evaluation of the antihypertensive effect of timolol and propranolol in patients with essential hypertension

Fifty patients with essential hypertension were studied for the antihypertensive effect of timolol and propranolol. In 16 out of 25 patients on timolol therapy (64%) blood pressure could be brought well under control (defined as diastolic blood pressure less than 90 mmHg) while with propranolol 13 out of 25 patients (52%) responded. Side-effects were negligible with timolol as compared to propranolol therapy. This study revealed that timolol is an effective and safe drug in essential hypertension, and is tolerated better than propranolol by the patients.