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

Anatomy and connectivity of the Göttingen minipig subgenual cortex (Brodmann area 25 homologue)

BACKGROUND

The subgenual gyrus is a promising target for deep brain stimulation (DBS) against depression. However, to optimize this treatment modality, we need translational animal models.

AIM

To describe the anatomy and connectivity of the Göttingen minipig subgenual area (sgC).

MATERIALS AND METHODS

The frontal pole of 5 minipigs was cryosectioned into 40 μm coronal and horizontal sections and stained with Nissl and NeuN-immunohistochemistry to visualize cytoarchitecture and cortical lamination. Eight animals were unilaterally stereotaxically injected in the sgC with anterograde (BDA) and retrograde (FluoroGold) tracers to reveal the sgC connectivity.

RESULTS

In homology with human nomenclature (Brodmann 1909), the minipig sgC can be subdivided into three distinct areas named area 25 (BA25), area 33 (BA33), and indusium griseum (IG). BA25 is a thin agranular cortex, approximately 1 mm thick. Characteristically, perpendicular to the pial surface, cell-poor cortical columns separate the otherwise cell-rich cortex of layer II, III and V. In layer V the cells are of similar size as seen in layer III, while layer VI contains more widely dispersed neurons. BA33 is less differentiated than BA25. Accordingly, the cortex is thinner and displays a complete lack of laminar differentiation due to diffusely arranged small, lightly stained neurons. It abuts the IG, which is a neuron-dense band of heavily stained small neurons separating BA33 directly from the corpus callosum and the posteriorly located septal nuclear area. Due to the limited area size and nearby location to the lateral ventricle and longitudinal cerebral fissure, only 3/8 animals received sgC injections with an antero- and retrograde tracer mixture. Retrograde tracing was seen primarily to the neighbouring ipsilateral ventral- and mPFC areas with some contralateral labelling as well. Prominent projections were furthermore observed from the ipsilateral insula, the medial aspect of the amygdala and the hippocampal formation, diencephalon and the brainstem ventral tegmental area. Anterograde tracing revealed prominent projections to the neighbouring medial prefrontal, mPFC and cingulate cortex, while moderate staining was noted in the hippocampus and adjoining piriform cortex.

CONCLUSION

The minipig sgC displays a cytoarchitectonic pattern and connectivity like the human and may be well suited for further translational studies on BA25-DBS against depression.

Structural and proteomic repercussions of growth hormone receptor deficiency on the pituitary gland: Lessons from a translational pig model

Growth hormone receptor deficiency (GHRD) results in low serum insulin-like growth factor 1 (IGF1) and high, but non-functional serum growth hormone (GH) levels in human Laron syndrome (LS) patients and animal models. This study investigated the quantitative histomorphological and molecular alterations associated with GHRD. Pituitary glands from 6 months old growth hormone receptor deficient (GHR-KO) and control pigs were analyzed using a quantitative histomorphological approach in paraffin (9 GHR-KO [5 males, 4 females] vs. 11 controls [5 males, 6 females]), ultrathin sections tissue sections (3 male GHR-KO vs. 3 male controls) and label-free proteomics (4 GHR-KO vs. 4 control pigs [2 per sex]). GHR-KO pigs displayed reduced body weights (60% reduction in comparison to controls; p < .0001) and decreased pituitary volumes (54% reduction in comparison to controls; p < .0001). The volume proportion of the adenohypophysis did not differ in GHR-KO and control pituitaries (65% vs. 71%; p = .0506) and GHR-KO adenohypophyses displayed a reduced absolute volume but an unaltered volume density of somatotrophs in comparison to controls (21% vs. 18%; p = .3164). In GHR-KO pigs, somatotroph cells displayed a significantly reduced volume density of granules (23.5%) as compared to controls (67.7%; p < .0001). Holistic proteome analysis of adenohypophysis samples identified 4660 proteins, of which 592 were differentially abundant between the GHR-KO and control groups. In GHR-KO samples, the abundance of somatotropin precursor was decreased, whereas increased abundances of proteins involved in protein production, transport and endoplasmic reticulum (ER) stress were revealed. Increased protein production and secretion as well as significantly reduced proportion of GH-storing granules in somatotroph cells of the adenohypophysis without an increase in volume density of somatotroph cells in the adenohypophysis could explain elevated serum GH levels in GHR-KO pigs.