Anatomy and histology of the Göttingen minipig adenohypophysis with special emphasis on the polypeptide hormones: GH, PRL, and ACTH.

The pituitary is involved in the regulation of endocrine homeostasis. Therefore, animal models of pituitary disease based on a thorough knowledge of pituitary anatomy are of great importance. Accordingly, we aimed to perform a qualitative and quantitative description of polypeptide hormone secreting cellular components of the Göttingen minipig adenohypophysis using immunohistochemistry and stereology. Estimates of the total number of cells immune-stained for adrenocorticotrophic hormone (ACTH), prolactin (PRL), and growth hormone (GH) were obtained with the optical fractionator technique using Stereo Investigator software. Moreover, 3D reconstructions of cell distribution were made. We estimated that the normal minipig adenohypophysis contains, on average, 5.6 million GH, 3.5 million PRL, and 2.4 million ACTH producing cells. The ACTH producing cells were widely distributed, while the PRL and GH producing cells were located in clusters in the central and lateral regions of the adenohypophysis. The morphology of the hormone producing cells also differs. We visualized a clear difference in the numerical density of hormone producing cells throughout the adenohypophysis. The relative proportions of the cells analyzed in our experiment are comparable to those observed in humans, primates, and rodents; however, the distribution of cells differs among species. The distribution of GH cells in the minipig is similar to that in humans, while the PRL and ACTH cell distributions differ. The volume of the pituitary is slightly smaller than that of humans. These data provide a framework for future large animal experimentation on pituitary function in health and disease.

Towards a Göttingen minipig model of adult onset growth hormone deficiency: evaluation of stereotactic electrocoagulation method.

BACKGROUND: Adult onset growth hormone (GH) deficiency (AGDH) is a potentially underdiagnosed condition, caused by damage to the pituitary gland. AGHD is treated with growth hormone replacement therapy. A large variety of clinical symptoms and changes in the metabolic homeostasis can be observed and quantified. New large animal models are needed for future drug development. NEW METHOD: In this study, we evaluate methods for a new large non-primate animal model of GH deficiency in post pubertal Göttingen Minipigs (minipig). Lesions in the pituitary gland were made by stereotaxic monopolar thermo-coagulation guided by magnetic resonance imaging (MRI), and pituitary function was evaluated using insulin tolerance test (ITT) with measurements of growth hormone secretion induced by hypoglycemia. RESULTS: Lesions were successfully applied to the pituitary gland without any damage to surrounding tissue including the hypothalamus, which was confirmed by post-operative MRI and post mortem histology. Plasma levels of GH during ITT showed no decrease in secreted levels one week after surgery compared to levels obtained before surgery. COMPARISON WITH EXISTING METHODS: Compared to other GH insufficiency models, eloquent brain tissue is spared. Furthermore, alternatively to rodent models, a large animal model would allow the use of human intended equipment to evaluate disease. Using the minipig avoids social, economical and ethical issues, compared with primates. CONCLUSION: The lesions did not remove all GH production, but proof of concept is demonstrated. In addition, the ITT is presented as a safe and efficient method to diagnose GH deficiency in minipigs.

A fiducial skull marker for precise MRI-based stereotaxic surgery in large animal models.

BACKGROUND: Stereotaxic neurosurgery in large animals is used widely in different sophisticated models, where precision is becoming more crucial as desired anatomical target regions are becoming smaller. Individually calculated coordinates are necessary in large animal models with cortical and subcortical anatomical differences. NEW METHOD: We present a convenient method to make an MRI-visible skull fiducial for 3D MRI-based stereotaxic procedures in larger experimental animals. Plastic screws were filled with either copper-sulfate solution or MRI-visible paste from a commercially available cranial head marker. The screw fiducials were inserted in the animal skulls and T1 weighted MRI was performed allowing identification of the inserted skull marker. RESULTS: Both types of fiducial markers were clearly visible on the MRÍs. This allows high precision in the stereotaxic space. COMPARISON WITH EXISTING METHOD: The use of skull bone based fiducial markers gives high precision for both targeting and evaluation of stereotaxic systems. There are no metal artifacts and the fiducial is easily removed after surgery. CONCLUSION: The fiducial marker can be used as a very precise reference point, either for direct targeting or in evaluation of other stereotaxic systems.

Exposure of the Pig CNS for Histological Analysis: A Manual for Decapitation, Skull Opening, and Brain Removal.

Pigs have become increasingly popular in large-animal translational neuroscience research as an economically and ethically feasible substitute to non-human primates. The large brain size of the pig allows the use of conventional clinical brain imagers and the direct use and testing of neurosurgical procedures and equipment from the human clinic. Further macroscopic and histological analysis, however, requires postmortem exposure of the pig central nervous system (CNS) and subsequent brain removal. This is not an easy task, as the pig CNS is encapsulated by a thick, bony skull and spinal column. The goal of this paper and instructional video is to describe how to expose and remove the postmortem pig brain and the pituitary gland in an intact state, suitable for subsequent macroscopic and histological analysis.