Functional Consequences of Adenovirus-Mediated Murine Pancreatic Gene Transfer

Abstract

Pancreatic adenoviral gene transfer can be achieved with high efficiency; however, questions concerning tissue injury from this commonly used vector have not been addressed. In these experiments, the effects of adenoviral gene transfer on pancreatic exocrine function were evaluated. Direct pancreatic injection with an adenoviral vector containing the Escherichia coli β-galactosidase (β-Gal; lacZ) transgene (H5.010CBlacZ) resulted in a high level of transgene expression (64 ± 6% of pancreatic cells expressed β-Gal) at 3 days following infection. However, amylase levels in four of five different subcellular pancreatic fractions were significantly decreased at this time point. Direct pancreatic injection with either saline or psoralen/UV-inactivated adenovirus did not have this effect, whereas both transduction with an adenoviral vector containing a different transgene and transduction with a homologous transgene resulted in decreased pancreatic amylase. The decrease in subcellular amylase levels persisted at 7 days post-transduction, and then returned to baseline at 21 days post-transduction. There was associated histologic damage (increased edema, inflammation, cell destruction, and vacuolization) at 3 and 7 days post-transduction, which resolved by 21 days. In summary, adenoviral transduction of the pancreas results in increased viral transgene expression and a uniform decrease in host amylase production throughout the pancreas. The normalization of amylase levels and histology suggest that organ recovery occurs. Gene transfer technology as a novel strategy for pancreatic diseases such as diabetes, pancreatitis, and cystic fibrosis is feasible but will benefit from continued approaches to limit toxicity. The functional effect of adenoviral administration on host organ function is an important factor to consider in the use of adenoviral vectors for gene transfer. This study evaluated the effect of pancreatic adenoviral transduction on pancreatic exocrine function. Subcellular fractionated amylase levels were determined following administration of the adenoviral vector. In addition, pancreatic histology was evaluated. We demonstrated that there was significant transgene expression and a uniform decrease in subcellular amylase content. This effect is undesirable, because organ function should not be compromised during therapeutic manipulations. However, the decrease in amylase content, as well as the pancreatic histologic damage, was transient, implying rapid organ recovery.