Mitosis and apoptosis in the pituitary gland: tumour formation or hyperplasia?

Fluorophores Use in Pituitary Surgery: A Pharmacokinetics and Pharmacodynamics Appraisal

(1) Background: Despite many surgical and technological advances, pituitary adenoma surgery is still burdened by non-negligible rates of incomplete tumor resection, mainly due to difficulties in differentiating pathology from normal pituitary tissue. Some fluorescent agents have been recently investigated as intraoperative contrast agents in pituitary surgery. The aim of this study is to evaluate the actual knowledge about the usefulness of such fluorophores with a particular focus on both the pharmacokinetics and pharmacodynamics issues of the pituitary gland. (2) Methods: We reviewed the current literature about fluorophores use in pituitary surgery and reported the first fully endoscopic experience with fluorescein. (3) Results: The studies investigating 5-ALA use reported contrasting results. ICG showed encouraging results, although with some specificity issues in identifying pathological tissue. Low-dose fluorescein showed promising results in differentiating pathology from normal pituitary tissue. Apart from the dose and timing of administration, both the fluorophores' volume of distribution and the histological variability of the interstitial space and vascular density played a crucial role in optimizing intraoperative contrast enhancement. (4) Conclusions: Both pharmacokinetics and pharmacodynamics issues determine the potential usefulness of fluorophores in pituitary surgery. ICG and fluorescein showed the most promising results, although further studies are needed.

Inhibition of estrogen-induced pituitary tumor growth and angiogenesis in Fischer 344 rats by the matrix metalloproteinase inhibitor batimastat

The development of estrogen-induced pituitary prolactinoma in Fischer 344 (F344) rats is associated with enhanced neovascularization. Based on the significance of matrix metalloproteinases (MMPs) for tumor growth and angiogenesis, we have studied the effect of batimastat (BB-94), a synthetic MMPs inhibitor (MMPI) on the progression of prolactin-secreting pituitary adenoma in rats. Pituitary tumors were induced in male F344 rats by s.c. implantation of Silastic tubes containing diethylstilbestrol (DES). The effects of chronic treatment with BB-94 (30 mg/kg b.w.) on pituitary weight, cell proliferation, apoptosis and vascular density were evaluated. We have stated that chronic treatment with batimastat caused a significant reduction in the pituitary weight. Batimastat has been found to decrease cell proliferation evaluated by a number of PCNA-positive stained cell nuclei. A marked increase in the apoptotic index within the pituitary was observed in the study group. Moreover, the density of microvessels identified by CD31 was reduced in the group treated with BB-94. The results of our study provide evidence for an inhibitory effect of batimastat, a synthetic MMPI, on the growth and angiogenesis in an experimental model of human prolactinoma. The ability of BB-94 to suppress established pituitary tumor growth suggests a possible application of MMPIs in the treatment of pituitary adenomas.

Differential effects of the early and late intrauterine environment on corticotrophic cell development

The developing embryo and fetus respond to a range of intrauterine stressors, but the effect of chronic intrauterine stress on the programmed development of pituitary corticotrophs has not been investigated. We have used a pregnant sheep model in which the embryonic environment at conception has been surgically perturbed by uterine carunclectomy. This procedure results in the development of fetuses that either are placentally restricted and chronically hypoxemic or that demonstrate compensatory placental growth and maintain normoxemia throughout late gestation. We found that uterine carunclectomy resulted in the emergence of a population of non-corticotrophin-releasing hormone (non-CRH) target cells that secreted high amounts of adrenocorticotrophic hormone (ACTH) in the fetal pituitary. This change in corticotroph development was independent of late-gestation hypoxemia. However, chronic hypoxemia during late gestation (in either carunclectomized or non-carunclectomized uterine environments) resulted in a reduction in the proportion of ACTH stored in CRH-target. Thus, the early and late intrauterine environments differentially program the development of specific corticotrophic cell types in the fetal pituitary. These patterns of altered corticotroph development are important given the central roles of the hypothalamo-pituitary-adrenal axis in the fetal adaptive response to intrauterine stress and in the early programming of adult disease.