Adenovirus-mediated human pancreatic lipase gene transfer to rat bile: gene therapy of fat malabsorption

Delivery of non-viral naked DNA vectors to liver in small weaned pigs by hydrodynamic retrograde intrabiliary injection

Hepatic gene therapy by delivering non-integrating therapeutic vectors in newborns remains challenging due to the risk of dilution and loss of efficacy in the growing liver. Previously we reported on hepatocyte transfection in piglets by intraportal injection of naked DNA vectors. Here, we established delivery of naked DNA vectors to target periportal hepatocytes in weaned pigs by hydrodynamic retrograde intrabiliary injection (HRII). The surgical procedure involved laparotomy and transient isolation of the liver. For vector delivery, a catheter was placed within the common bile duct by enterotomy. Under optimal conditions, no histological abnormalities were observed in liver tissue upon pressurized injections. The transfection of hepatocytes in all tested liver samples was observed with vectors expressing luciferase from a liver-specific promoter. However, vector copy number and luciferase expression were low compared to hydrodynamic intraportal injection. A 10-fold higher number of vector genomes and luciferase expression was observed in pigs using a non-integrating naked DNA vector with the potential for replication. In summary, the HRII application was less efficient (i.e., lower luciferase activity and vector copy numbers) than the intraportal delivery method but was significantly less distressful for the piglets and has the potential for injection (or re-injection) of vector DNA by endoscopic retrograde cholangiopancreatography.

Regenerative medicine and cell-based approaches to restore pancreatic function

The pancreas is a complex organ with exocrine and endocrine components. Many pathologies impair exocrine function, including chronic pancreatitis, cystic fibrosis and pancreatic ductal adenocarcinoma. Conversely, when the endocrine pancreas fails to secrete sufficient insulin, patients develop diabetes mellitus. Pathology in either the endocrine or exocrine pancreas results in devastating economic and personal consequences. The current standard therapy for treating patients with type 1 diabetes mellitus is daily exogenous insulin injections, but cell sources of insulin provide superior glycaemic regulation and research is now focused on the goal of regenerating or replacing β cells. Stem-cell-based models might be useful to study exocrine pancreatic disorders, and mesenchymal stem cells or secreted factors might delay disease progression. Although the standards that bioengineered cells must meet before being considered as a viable therapy are not yet established, any potential therapy must be acceptably safe and functionally superior to current therapies. Here, we describe progress and challenges in cell-based methods to restore pancreatic function, with a focus on optimizing the site for cell delivery and decreasing requirements for immunosuppression through encapsulation. We also discuss the tools and strategies being used to generate exocrine pancreas and insulin-producing β-cell surrogates in situ and highlight obstacles to clinical application.

Enzyme replacement therapy for pancreatic insufficiency: present and future

Pancreatic enzyme replacement therapy is currently the mainstay of treatment for nutrient malabsorption secondary to pancreatic insufficiency. This treatment is safe and has few side effects. Data demonstrate efficacy in reducing steatorrhea and fat malabsorption. Effective therapy has been limited by the ability to replicate the physiologic process of enzyme delivery to the appropriate site, in general the duodenum, at the appropriate time. The challenges include enzyme destruction in the stomach, lack of adequate mixing with the chyme in the duodenum, and failing to deliver and activate at the appropriate time. Treatment is begun when clinically significant malabsorption occurs resulting in steatorrhea and weight loss. Treatment failure is addressed in a sequential fashion. Current research is aimed at studying new enzymes and delivery systems to improve the efficiency of action in the duodenum along with developing better means to monitor therapy.

Pancreatic enzyme replacement therapy in chronic pancreatitis

Exocrine pancreatic insufficiency (EPI) is a serious condition which occurs in several diseases including chronic pancreatitis (CP), cystic fibrosis, pancreatic cancer, and as a result of pancreatic surgery. The lack or absence of pancreatic enzymes leads to an inadequate absorption of fat, proteins, and carbohydrates, causing steatorrhoea and creathorrhea which results in abdominal discomfort, weight loss, and nutritional deficiencies. To avoid malnutrition related morbidity and mortality, it is pivotal to commence pancreatic enzyme replacement therapy (PERT) as soon as EPI is diagnosed. Factors as early acidic inactivation of ingested enzymes, under dosage, and patient incompliance may prevent normalisation of nutrient absorption, in particular of fat digestion. This review focuses on the current status of how to diagnose and treat EPI.

Delayed release pancrelipase for treatment of pancreatic exocrine insufficiency associated with chronic pancreatitis

Pancreatic enzyme supplements (PES) are used in chronic pancreatitis (CP) for correction of pancreatic exocrine insufficiency (PEI) as well as pain and malnutrition. The use of porcine pancreatic enzymes for the correction of exocrine insufficiency is governed by the pathophysiology of the disease as well as pharmacologic properties of PES. Variability in bioequivalence of PES has been noted on in vitro and in vivo testing and has been attributed to the differences in enteric coating and the degree of micro-encapsulation. As a step towards standardizing pancreatic enzyme preparations, the Food and Drug Administration now requires the manufacturers of PES to obtain approval of marketed formulations by April 2010. In patients with treatment failure, apart from evaluating drug and dietary interactions and compliance, physicians should keep in mind that patients may benefit from switching to a different formulation. The choice of PES (enteric coated versus non-enteric coated) and the need for acid suppression should be individualized. There is no current standard test for evaluating adequacy of therapy in CP patients and studies have shown that optimization of therapy based on symptoms may be inadequate. Goals of therapy based on overall patient presentation and specific laboratory tests rather than mere correction of steatorrhea are needed.

Chitosan-DNA nanoparticles delivered by intrabiliary infusion enhance liver-targeted gene delivery

The goal of this study was to examine the efficacy of liver-targeted gene delivery by chitosan-DNA nanoparticles through retrograde intrabiliary infusion (RII). The transfection efficiency of chitosan-DNA nanoparticles, as compared with PEI-DNA nanoparticles or naked DNA, was evaluated in Wistar rats by infusion into the common bile duct, portal vein, or tail vein. Chitosan-DNA nanoparticles administrated through the portal vein or tail vein did not produce detectable luciferase expression. In contrast, rats that received chitosan-DNA nanoparticles showed more than 500 times higher luciferase expression in the liver 3 days after RII; and transgene expression levels decreased gradually over 14 days. Luciferase expression in the kidney, lung, spleen, and heart was negligible compared with that in the liver. RII of chitosan-DNA nanoparticles did not yield significant toxicity and damage to the liver and biliary tree as evidenced by liver function analysis and histopathological examination. Luciferase expression by RII of PEI-DNA nanoparticles was 17-fold lower than that of chitosan-DNA nanoparticles on day 3, but it increased slightly over time. These results suggest that RII is a promising routine to achieve liver-targeted gene delivery by non-viral nanoparticles; and both gene carrier characteristics and mode of administration significantly influence gene delivery efficiency.

Interleukin-4 gene transfer into rat pancreas by recombinant adenovirus

OBJECTIVE

Adenovirus-mediated gene transfer technology may provide a novel approach in the treatment of pancreatic diseases. In the rat model of chronic pancreatitis induced by dibutyltin dichloride (DBTC), Th1 lymphocytes are known to be involved in the mediation of inflammation. We therefore investigated whether local expression of the Th2 cytokine interleukin (IL)-4 might modulate the inflammatory response. To address this question, we have established a protocol of efficient gene transfer into rat pancreas.

MATERIAL AND METHODS

Recombinant adenovirus constructs carrying the Escherichia coli beta-galactosidase gene (Adbeta-gal) or the rat IL-4 gene (AdrIL-4) were injected into the left gastric artery of healthy LEW.1W rats. Expression of beta-Gal and IL-4 in pancreatic cells was analyzed by X-Gal staining and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. After optimization of the transduction protocol, effects of the IL-4 gene transfer on pancreatic inflammation and fibrosis were studied in DBTC-treated rats.

RESULTS

Seven days after Adbeta-gal injection, beta-gal-positive cells were detectable in the rat pancreas. RT-PCR analysis using RNA from pancreata of AdrIL-4-treated rats indicated that IL-4 was expressed for at least 14 days after adenovirus application. Expression of the IL-4 transgene was accompanied by a transient increase of the IL-10 mRNA level in the pancreas. In DBTC-treated rats, adenovirus-mediated transfer of the IL-4 gene modified the pattern of infiltrating inflammatory cells in the pancreas. Importantly, a decrease of CD4+ helper cells was observed.

CONCLUSIONS

Our data suggest that the injection of recombinant adenoviruses into the left gastric artery is a promising approach to achieving expression of therapeutic transgenes in the pancreas.

Pancreatic Enzyme Supplementation Therapy

Effective treatment of malabsorption due to severe pancreatic exocrine insufficiency requires delivery of sufficient enzymatic activity into the duodenal lumen simultaneously with meal nutrients. To achieve this, modern therapeutic concepts recommend administration of 25,000 to 40,000 units of lipase per meal using pH-sensitive pancreatin microspheres. In case of treatment failure, dosage should be increased two to three times. If this still is not successful, compliance may be checked by measurement of fecal chymotrypsin, although this is not a standardized procedure. In the compliant patient, diagnosis of pancreatic exocrine insufficiency needs to be reviewed, particularly cases of celiac disease, (concomitant) bacterial overgrowth, and blind loop syndrome, as well as giardiasis, which need to be excluded or otherwise be treated specifically. Finally, additional acid suppression with application of unprotected pancreatin and/or reduced fat intake may help to control malabsorption. Still, in most patients, lipid digestion cannot be completely normalized by current standard therapy. On the one hand, this leads to loss of energy that may only partly be compensated for by increased nutrient intake. On the other hand, increased nutrient exposition of distal intestinal sites may release excessive amounts of mostly inhibitory distal intestinal neurohumoral mediators, and thereby disturb gastrointestinal secretory and motor functions. Consequently, future developments are needed for optimizing treatment.

Lipase supplementation therapy: standards, alternatives, and perspectives

Treatment of steatorrhea by lipase supplementation therapy has become more successful in the last decade due to better understanding of the physiology and pathophysiology of the digestive process. Porcine lipase has been the therapeutic standard for several decades and will continue to be the treatment of choice in pancreatic exocrine insufficiency. Modern therapeutic concepts recommend administration of 25,000-40,000 units of porcine lipase per meal using pH-sensitive pancreatin microspheres. In case of treatment failure, the dose should be increased, compliance should be checked, and other reasons for malabsorption should be excluded. Still, in most patients, lipid digestion cannot be completely normalized by current standard therapy, and future developments are needed for optimizing treatment. In this article, pathophysiologic characteristics of pancreatic exocrine insufficiency, prerequisites for use of alternative lipase sources as well as currently available lipases of nonporcine origin, and new developments are discussed. Current literature suggests that bovine lipase products present a theoretical alternative but play no major role in the western world. Fungal lipase has inferior properties compared with conventional products. Bacterial lipase products show promising potential and offer future therapeutic alternatives. Moreover, human pancreatic lipase gene transfer and application of bioengineered human gastric lipase appear on the horizon.

Enhanced delivery of drugs to the liver by adenovirus-mediated heterologous expression of the human oligopeptide transporter PEPT1

To explore the feasibility of drug delivery to the liver by the use of adenovirus-mediated human oligopeptide transporter (hPEPT1) gene transfer, we examined the accumulation of L-[(3)H]carnosine in the hepatoma cell line (HepG2 and WIFB9) and mouse liver. We constructed a recombinant adenovirus encoding hPEPT1-enhanced yellow fluorescent protein (EYFP) fusion gene (AdhPEPT1-EYFP). In vitro uptake of L-[(3)H]carnosine was determined in HepG2 and WIFB9 cells transduced with AdhPEPT1-EYFP. In vivo, the accumulation of L-[(3)H]carnosine in mouse liver was evaluated after transduction of AdhPEPT1-EYFP. At pH 6.0, the uptake of L-[(3)H]carnosine by HepG2 and WIFB9 cells transduced with AdhPEPT1-EYFP was increased 15- and 2-fold, respectively, compared with the cells without transduction. At pH 7.4, uptake of L-[(3)H]carnosine in AdhPEPT1-EYFP transduced HepG2 cells was 3 times greater than that of nontransduced cells. In the presence of carnosine or glycylsarcosine as an inhibitor at 20 mM, the uptake of L-[(3)H]carnosine was reduced to a level comparable to that of nontransduced cells. At 30 min after intravenous administration of L-[(3)H]carnosine to mice transduced with AdhPEPT1-EYFP at 1 x 10(10) plaque-forming units/mouse, the tissue-to-plasma concentration ratio (K(p)) of L-[(3)H]carnosine in the liver was significantly increased to 7 times that of nontransduced mice. In contrast, the K(p) value of [(14)C]inulin, a marker for extracellular fluid space, remained unchanged after adenoviral transduction suggesting minimal pathological damage of tissues. hPEPT1-EYFP was localized at both the basolateral and apical membranes in HepG2 cells, WIFB9 cells, and mouse liver. In conclusion, our results suggest that delivery of oligopeptide to the liver by adenovirus-mediated heterologous expression of hPEPT1 in vivo is feasible.

In vivo gene delivery via portal vein and bile duct to individual lobes of the rat liver using a polylysine-based nonviral DNA vector in combination with chloroquine

The objective of this study was to evaluate a bifunctional synthetic peptide as a DNA vector for regional gene delivery to the rat liver by the portal vein and bile duct routes. The 31-amino-acid peptide (polylysine-molossin) comprises an amino-terminal chain of 16 lysines for electrostatic binding of DNA, and the 15 amino acid integrin-binding domain of the venom of the American pit viper, Crotalus molossus molossus. Initial in vitro evaluation demonstrated that polylysine-molossin/DNA complexes were much smaller (approximately 50-100nm versus 500-1300nm), more positively charged, and more stable in isotonic dextrose in comparisons with salt-containing solutions. However, polylysine-molossin/DNA complexes in any solution other than complete culture medium were ineffective for gene delivery in vitro. Vector localization studies demonstrated that both the portal vein and bile duct routes provided excellent access of polylysine-molossin/DNA complexes to the liver. However, complexes delivered by the portal vein were rapidly lost (<15 min) following re-establishment of the portal circulation, whereas complexes delivered by the bile duct persisted much longer. Polylysine-molossin/DNA complexes in various isotonic solutions were delivered to the right lateral lobes either by perfusion through a branch of the portal vein or by infusion into appropriate branches of the bile duct. Two or three hours before gene delivery, rats were given a single injection of chloroquine. We report that the polylysine-molossin vector is much more effective (>10-fold) when delivered by the bile duct route with all isotonic solutions evaluated, and that polylysine-molossin/DNA complexes in isotonic dextrose are much more effective (>10-fold) than complexes in salt-containing solutions.