Adrenocortical-specific transgene expression directed by steroid hydroxylase gene promoters

Adrenal gland infection by serotype 5 adenovirus requires coagulation factors

Recombinant, replication-deficient serotype 5 adenovirus infects the liver upon in vivo, systemic injection in rodents. This infection requires the binding of factor X to the capsid of this adenovirus. Another organ, the adrenal gland is also infected upon systemic administration of Ad, however, whether this infection is dependent on the cocksackie adenovirus receptor (CAR) or depends on the binding of factor X to the viral capsid remained to be determined. In the present work, we have used a pharmacological agent (warfarin) as well as recombinant adenoviruses lacking the binding site of Factor X to elucidate this mechanism in mice. We demonstrate that, as observed in the liver, adenovirus infection of the adrenal glands in vivo requires Factor X. Considering that the level of transduction of the adrenal glands is well-below that of the liver and that capsid-modified adenoviruses are unlikely to selectively infect the adrenal glands, we have used single-photon emission computed tomography (SPECT) imaging of gene expression to determine whether local virus administration (direct injection in the kidney) could increase gene transfer to the adrenal glands. We demonstrate that direct injection of the virus in the kidney increases gene transfer in the adrenal gland but liver transduction remains important. These observations strongly suggest that serotype 5 adenovirus uses a similar mechanism to infect liver and adrenal gland and that selective transgene expression in the latter is more likely to be achieved through transcriptional targeting.

Transgenic GATA-4 expression induces adrenocortical tumorigenesis in C57Bl/6 mice

A link between elevated luteinizing hormone (LH) levels, GATA-4 and LH receptor (LHCGR) expression and gonadotropin-dependent adrenocortical tumorigenesis in humans and mice has been shown. To assess the mechanistic tumorigenic interrelationships between these factors, we transgenically expressed Gata4 under the 21-hydroxylase promoter (Cyp21a1, 21-OH) in C57Bl/6N mice. There was a gradual age-dependent increase of GATA-4 expression only in 21-OH-GATA-4 (TG) female adrenals, in association with slowly progressing neoplasia of non-steroidogenic spindle-shaped A cells in the subcapsular cortex. Gonadectomy (GDX), apparently through direct action of elevated serum LH, markedly enhanced the adrenocortical neoplasia, which now also appeared in GDX TG males. The neoplastic areas of the post-GDX TG adrenals contained, besides A cells, larger lipid-laden, steroidogenically active and LHCGR-positive B cells. Prolonged (>10 months) exposure to elevated post-GDX LH levels resulted in formation of adrenocortical adenomas in the TG mice. Intact and GDX TG mouse adrenals displayed elevated FOG-2 and decreased GATA-6 expression. Additionally, increased expression/activation of components of the Inhbb-Acvr2a-Acvr1c-Smad2/3 signaling system was observed in 12-month-old GDX TG adrenals. Our findings show that two distinct GATA-4-dependent populations of neoplastic adrenocortical cells form: non-steroidogenic LH-independent A cells and steroidogenic LH-dependent B cells.

Cellular characterization of the tropism of recombinant adenovirus for the adrenal glands

BACKGROUND

Recombinant adenoviruses are widely used in gene therapy clinical trials. A particular tropism for the adrenal glands has been reported but the precise cellular base for this tropism has not been determined.

MATERIALS AND METHODS

Recombinant adenoviruses were injected intravenously into Balb/c nu/nu or C57BL/6 mice. Seventy-two hours later, the animals were sacrificed and the adrenal glands and livers collected. The glands were sectioned and analyzed using immunohistochemical methods to detect adenoviral epitopes and transgene expression. Total RNA were extracted from the liver and adrenal glands of some animals and subjected to real-time RT-PCR.

RESULTS

The only cell type infected in the adrenal glands of Balb/c nu/nu or C57BL/6 mice is the adrenocortical cells in the zona fasciculata. Quantitatively, the relative level of gene expression in the adrenal gland is comparable but lower than that measured in the liver.

CONCLUSIONS

Systemic injection of recombinant adenovirus could be used as a procedure to restore adrenal steroidogenesis in clinical gene therapy protocols. In addition, our study suggest that adrenal dysfunction should be considered when criteria are established to assess the safety of gene therapy formulations administered systemically.

Cord-like mosaic patches in the adrenal cortex are fractal: implications for growth and development

Organogenesis proceeds rapidly and faithfully during fetal development. The process includes generation of parenchyma, followed by organization into functional tissues. The method by which the growth of organ parenchyma is regulated is not known, but insight into this regulation has been obtained by studying mosaic tissues of experimental chimeras and transgenic mosaics. The patterns revealed by this procedure offer an indication of how the parenchyma was generated. In the liver, the pattern appears as islands of one cell type in a sea of the other cell type, while in the adrenal cortex the pattern is one of alternating cords of one cell type adjacent to the other cell type. We have established previously that mosaic patches in the liver are fractal. The fractal dimensions of patches in the liver are consistent with an iterative, recursive growth model with simple stereotypical division rules. Here we report that the patches in mosaic adrenal cortex of the mouse and rat are also fractal and that the fractal dimension of the surface of the patches is lower than that in the liver. Fetal development and fractal dimensions of adrenal cortical mosaic patches are consistent with an algorithmic cell division model in which parenchymal growth is constrained to edges of growth centers forcing cord structures to form. Fractal analysis of the geometry of mosaic patches in tissues of experimental chimeras is helpful in constructing hypotheses of organ growth.

Transgenic animal models for the functional analysis of vasoactive peptides

The interplay of vasoactive peptide systems is an essential determinant of blood pressure regulation in mammals. While the endothelin and the renin-angiotensin systems raise blood pressure by inducing vasoconstriction and sodium retention, the kallikrein-kinin and the natriuretic-peptide systems reduce arterial pressure by eliciting vasodilatation and natriuresis. Transgenic technology has proven to be very useful for the functional analysis of vasoactive peptide systems. As an outstanding example, transgenic rats overexpressing the mouse Ren-2 renin gene in several tissues become extremely hypertensive. Several other transgenic rat and mouse strains with genetic modifications of components of the renin-angiotensin system have been developed in the past decade. Moreover, in recent years gene-targeting technology was employed to produce mouse strains lacking these proteins. The established animal models as well as the main insights gained by their analysis are summarized in this review.