RESUMO
Pituitary cells that express the transcription factor SOX2 are stem cells because they can self-renew and differentiate into multiple pituitary hormone-producing cell types as organoids. Wounding and physiological challenges can activate pituitary stem cells, but cell numbers are not fully restored, and the ability to mobilize stem cells decreases with increasing age. The basis of these limitations is still unknown. The regulation of stem cell quiescence and activation involves many different signalling pathways, including those mediated by WNT, Hippo and several cytokines; more research is needed to understand the interactions between these pathways. Pituitary organoids can be formed from human or mouse embryonic stem cells, or from human induced pluripotent stem cells. Human pituitary organoid transplantation is sufficient to induce corticosterone release in hypophysectomized mice, raising the possibility of therapeutic applications. Today, pituitary organoids have the potential to assess the role of individual genes and genetic variants on hormone production ex vivo, providing an important tool for the advancement of exciting frontiers in pituitary stem cell biology and pituitary organogenesis. In this article, we provide an overview of notable discoveries in pituitary stem cell function and highlight important areas for future research.
Assuntos
Células-Tronco Pluripotentes Induzidas , Humanos , Animais , Camundongos , Células-Tronco Pluripotentes Induzidas/metabolismo , Hipófise/metabolismo , Fatores de Transcrição/metabolismo , Transdução de Sinais , Diferenciação CelularRESUMO
Serum prolactin increases from birth to adulthood in rats, being higher in females from birth. The maturation of hypothalamic/gonadal prolactin-releasing and -inhibiting factors does not explain some sex differences observed. During the first weeks of life, prolactin secretion increases, even when lactotrophs are isolated in vitro, in the absence of those controls, suggesting the participation of intra-pituitary factors in this control. The present work aimed to study the involvement of pituitary activins in the regulation of prolactin secretion during post-natal development. Sex differences were also highlighted. Female and male Sprague-Dawley rats at 11, 23 and 45postnatal days were used. Pituitary expression of activin subunits and activin receptors was maximum in p11 female pituitaries, being even higher than that observed in males. Those expressions decrease with age in females, and then the gender differences disappear at p23. Inhbb expression strongly increases at p45 in males, being the predominant subunit in this sex in adulthood. Activin inhibition of prolactin is mediated by the inhibition of Pit-1 expression. This action involves not only the canonical pSMAD pathway but also the phosphorylation of p38MAPK. At p11, almost all lactotrophs express p-p38MAPK in females, and its expression decreases with age with a concomitant increase in Pit-1. Our findings suggest that the inhibitory regulation of pituitary activins on prolactin secretion is sex specific; this regulation is more relevant in females during the first week of life and decreases with age; this intra-pituitary regulation is involved in the sex differences observed in serum prolactin levels during postnatal development.
Assuntos
Lactotrofos , Prolactina , Feminino , Ratos , Masculino , Animais , Prolactina/metabolismo , Ativinas/metabolismo , Ratos Sprague-Dawley , Hipófise/metabolismo , Lactotrofos/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Sex differences in the control of prolactin secretion are well documented. Sex-related differences in intrapituitary factors regulating lactotroph function have recently attracted attention. Sex differences in prolactinoma development are well documented in clinic, prolactinomas being more frequent in women but more aggressive in men, for poorly understood reasons. Kallikrein, the enzyme releasing kinins has been found in the pituitary, but there is no information on pituitary kinin receptors and their function. In the present work, we characterized pituitary bradykinin receptors (BRs) at the messenger RNA and protein levels in 2 mouse models of prolactinoma, Drd2 receptor gene inactivation and hCGß gene overexpression, in both males and females, wild type or genomically altered. BR B2 (B2R) accounted for 97% or more of total pituitary BRs in both models, regardless of genotype, and was present in lactotrophs, somatotrophs, and gonadotrophs. Male pituitaries displayed higher level of B2R than females, regardless of genotype. Pituitary B2R gene expression was downregulated by estrogen in both males and females but only in females by dopamine. Activation of B1R or B2R by selective pharmacological agonists induced prolactin release in male pituitaries but inhibited prolactin secretion in female pituitaries. Increased B2R content was observed in pituitaries of mutated animals developing prolactinomas, compared to their respective wild-type controls. The present study documents a novel sex-related difference in the control of prolactin secretion and suggests that kinins are involved, through B2R activation, in lactotroph function and prolactinoma development.
Assuntos
Neoplasias Hipofisárias , Prolactinoma , Animais , Feminino , Humanos , Cininas , Masculino , Camundongos , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/metabolismo , Prolactina/metabolismo , Prolactinoma/genética , Prolactinoma/metabolismo , Receptor B2 da Bradicinina/agonistas , Receptor B2 da Bradicinina/genética , Receptor B2 da Bradicinina/metabolismo , Receptores da BradicininaRESUMO
Among pituitary adenomas, prolactinomas are the most frequently diagnosed (about 50%). Dopamine agonists are generally effective in the treatment of prolactinomas. However, a subset of about 25% of patients does not respond to these agents. The management of drug-resistant prolactinomas remains a challenge for endocrinologists and new inhibitory treatments are needed. Pituitary activins inhibit lactotroph function. Its expression and action were found reduced in animal models of lactotroph hyperplasia (female mice overexpressing the B subunit of the human chorionic gonadotrophin and female mice knockout for dopamine receptor type 2). In these models, an oophorectomy avoids prolactinoma development. Hormonal replacement with oestradiol and/or progesterone is not enough to reach the tumor size observed in transgenic females. We postulated that the loss of gonadal inhibins after an oophorectomy contributes to prevent hyperplasia development. Here, we demonstrated that an oophorectomy at 2 months age recovers the following in adulthood: (i) pituitary activin expression, (ii) activin receptor expression specifically in lactotroph population, (iii) activin biological activity in lactotrophs with a concomitant reduction of Pit-1 expression. To summarize, when an oophorectomy is performed, inhibins are lost and the inhibitory action of pituitary activins on lactotroph population is recovered, helping to prevent lactotroph hyperplasia development. These results emphasize the importance of the inhibitory action of activins on lactotroph function, positioning activins as a good therapeutic target for the treatment of resistant prolactinomas.
Assuntos
Lactotrofos , Neoplasias Hipofisárias , Prolactinoma , Ativinas/metabolismo , Adulto , Animais , Feminino , Humanos , Hiperplasia , Inibinas/metabolismo , Inibinas/uso terapêutico , Lactotrofos/metabolismo , Lactotrofos/patologia , Camundongos , Ovariectomia , Neoplasias Hipofisárias/metabolismo , Prolactina/metabolismo , Prolactinoma/metabolismo , Prolactinoma/prevenção & controleRESUMO
PURPOSE: Congenital hypopituitarism (CH) can present in isolation or with other birth defects. Mutations in multiple genes can cause CH, and the use of a genetic screening panel could establish the prevalence of mutations in known and candidate genes for this disorder. It could also increase the proportion of patients that receive a genetic diagnosis. METHODS: We conducted target panel genetic screening using single-molecule molecular inversion probes sequencing to assess the frequency of mutations in known hypopituitarism genes and new candidates in Argentina. We captured genomic deoxyribonucleic acid from 170 pediatric patients with CH, either alone or with other abnormalities. We performed promoter activation assays to test the functional effects of patient variants in LHX3 and LHX4. RESULTS: We found variants classified as pathogenic, likely pathogenic, or with uncertain significance in 15.3% of cases. These variants were identified in known CH causative genes (LHX3, LHX4, GLI2, OTX2, HESX1), in less frequently reported genes (FOXA2, BMP4, FGFR1, PROKR2, PNPLA6) and in new candidate genes (BMP2, HMGA2, HNF1A, NKX2-1). CONCLUSION: In this work, we report the prevalence of mutations in known CH genes in Argentina and provide evidence for new candidate genes. We show that CH is a genetically heterogeneous disease with high phenotypic variation and incomplete penetrance, and our results support the need for further gene discovery for CH. Identifying population-specific pathogenic variants will improve the capacity of genetic data to predict eventual clinical outcomes.
Assuntos
Doenças do Sistema Endócrino/genética , Testes Genéticos/estatística & dados numéricos , Hipopituitarismo/genética , Mutação/genética , Adolescente , Adulto , Argentina , Criança , Pré-Escolar , Feminino , Heterogeneidade Genética , Humanos , Lactente , Proteínas com Homeodomínio LIM/genética , Masculino , Fenótipo , Polimorfismo de Nucleotídeo Único , Fatores de Transcrição/genética , Adulto JovemRESUMO
Serum prolactin levels gradually increase from birth to puberty in both male and female rats, with higher levels observed in female since the first days of life. The increase in lactotroph secretion was attributed to the maturation of prolactin-inhibiting and prolactin-releasing factors; however, those mechanisms could not fully explain the gender differences observed. Prolactin secretion from isolated lactotrophs, in the absence of hypothalamic control, also increases during the first weeks of life, suggesting the involvement of intra-pituitary factors. We postulate that pituitary transforming growth factor beta 1 (TGFß1) is involved in the regulation of prolactin secretion as well as in the gender differences observed at early postnatal age. Several components of the local TGFß1 system were evaluated during postnatal development (11, 23, and 45 days) in female and male Sprague-Dawley rats. In vivo assays were performed to study local TGFß1 activation and its impact on prolactin secretion. At day 11, female pituitaries present high levels of active TGFß1, concomitant with the highest expression of TGFß1 target genes and the phospho-Smad3 immunostaining in lactotrophs. The steady increase in prolactin secretion inversely correlates with active TGFß1 levels only in females. Dopamine and estradiol induce TGFß1 activation at day 11, in both genders, but its activation induces the inhibition of prolactin secretion only in females. Our findings demonstrate that: (1) TGFß1 activation is regulated by dopamine and estradiol; (2) the inhibitory regulation of local TGFß1 on prolactin secretion is gender specific; and (3) this mechanism is responsible, at least partially, for the gender differences observed being relevant during postnatal development.
Assuntos
Fator de Crescimento Transformador beta1/metabolismo , Animais , Dopamina/farmacologia , Estradiol/farmacologia , Feminino , Lactotrofos/efeitos dos fármacos , Lactotrofos/metabolismo , Masculino , Prolactina/metabolismo , Ratos , Ratos Sprague-Dawley , Caracteres Sexuais , Proteína Smad3/metabolismoRESUMO
The anterior pituitary gland is comprised of specialized cell-types that produce and secrete polypeptide hormones in response to hypothalamic input and feedback from target organs. These specialized cells arise during embryonic development, from stem cells that express SOX2 and the pituitary transcription factor PROP1, which is necessary to establish the stem cell pool and promote an epithelial to mesenchymal-like transition, releasing progenitors from the niche. Human and mouse embryonic stem cells can differentiate into all major hormone-producing cell types of the anterior lobe in a highly plastic and dynamic manner. More recently human induced pluripotent stem cells (iPSCs) emerged as a viable alternative due to their plasticity and high proliferative capacity. This mini-review gives an overview of the major advances that have been achieved to develop protocols to generate pituitary hormone-producing cell types from stem cells and how these mechanisms are regulated. We also discuss their application in pituitary diseases, such as pituitary hormone deficiencies.
Assuntos
Diferenciação Celular/fisiologia , Células-Tronco Pluripotentes Induzidas/fisiologia , Células-Tronco Pluripotentes Induzidas/transplante , Hipófise/fisiologia , Hipófise/transplante , Medicina Regenerativa/métodos , Animais , Humanos , Células-Tronco Pluripotentes Induzidas/citologia , Doenças da Hipófise/patologia , Doenças da Hipófise/terapia , Hipófise/citologia , Medicina Regenerativa/tendênciasRESUMO
Membrane progesterone receptors are known to mediate rapid nongenomic progesterone effects in different cell types. Recent evidence revealed that mPRα is highly expressed in the rat pituitary, being primarily localized in lactotrophs, acting as an intermediary of P4-inhibitory actions on prolactin secretion. The role of mPRs in prolactinoma development remains unclear. We hypothesize that mPR agonists represent a novel tool for hyperprolactinemia treatment. To this end, pituitary expression of mPRs was studied in three animal models of prolactinoma. Expression of mPRs and nuclear receptor was significantly decreased in tumoral pituitaries compared to normal ones. However, the relative proportion of mPRα and mPRß was highly increased in prolactinomas. Interestingly, the selective mPR agonist (Org OD 02-0) significantly inhibited PRL release in both normal and tumoral pituitary explants, displaying a more pronounced effect in tumoral tissues. As P4 also regulates PRL secretion indirectly, by acting on dopaminergic neurons, we studied mPR involvement in this effect. We found that the hypothalamus has a high expression of mPRs. Interestingly, both P4 and OrgOD 02-0 increased dopamine release in hypothalamus explants. Moreover, in an in vivo treatment, that allows both, pituitary and hypothalamus actions, the mPR agonist strongly reduced the hyperprolactinemia in transgenic females carrying prolactinoma. Finally, we also found and interesting gender difference: males express higher levels of pituitary mPRα/ß, a sex that does not develop prolactinoma in these mice models. Taken together, these findings suggest mPRs activation could represent a novel tool for hyperprolactinemic patients, especially those that present resistance to dopaminergic drugs.
Assuntos
Neoplasias Hipofisárias/prevenção & controle , Progesterona/farmacologia , Prolactina/metabolismo , Prolactinoma/prevenção & controle , Receptores de Dopamina D2/fisiologia , Receptores de Progesterona/agonistas , Animais , Gonadotropina Coriônica Humana Subunidade beta/genética , Gonadotropina Coriônica Humana Subunidade beta/metabolismo , Feminino , Humanos , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Neoplasias Hipofisárias/etiologia , Neoplasias Hipofisárias/patologia , Prolactinoma/etiologia , Prolactinoma/patologia , Ratos , Transdução de SinaisRESUMO
Ovarian steroids control a variety of physiological functions. They exert actions through classical nuclear steroid receptors, but rapid non-genomic actions through specific membrane steroid receptors have been also described. In this study, we demonstrate that the G-protein-coupled estrogen receptor (GPER) is expressed in the rat pituitary gland and, at a high level, in the lactotroph population. Our results revealed that ~40% of the anterior pituitary cells are GPER positive and ~35% of the lactotrophs are GPER positive. By immunocytochemical and immuno-electron-microscopy studies, we demonstrated that GPER is localized in the plasmatic membrane but is also associated to the endoplasmic reticulum in rat lactotrophs. Moreover, we found that local Gper expression is regulated negatively by 17ß-estradiol (E2) and progesterone (P4) and fluctuates during the estrus cycle, being minimal in proestrus. Interestingly, lack of ovarian steroids after an ovariectomy (OVX) significantly increased pituitary GPER expression specifically in the three morphologically different subtypes of lactotrophs. We found a rapid estradiol stimulatory effect on PRL secretion mediated by GPER, both in vitro and ex vivo, using a GPER agonist G1, and this effect was prevented by the GPER antagonist G36, demonstrating a novel role for this receptor. Then, the increased pituitary GPER expression after OVX could lead to alterations in the pituitary function as all three lactotroph subtypes are target of GPER ligand and could be involved in the PRL secretion mediated by GPER. Therefore, it should be taken into consideration in the response of the gland to an eventual hormone replacement therapy.
Assuntos
Estradiol/farmacologia , Lactotrofos/metabolismo , Adeno-Hipófise/metabolismo , Progesterona/farmacologia , Receptores Acoplados a Proteínas G/metabolismo , Animais , Linhagem Celular Tumoral , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Estrogênios/farmacologia , Feminino , Expressão Gênica/efeitos dos fármacos , Lactotrofos/efeitos dos fármacos , Lactotrofos/ultraestrutura , Ovariectomia , Adeno-Hipófise/citologia , Proestro , Ratos Sprague-Dawley , Receptores Acoplados a Proteínas G/genéticaRESUMO
Female transgenic mice that overexpress the human chorionic gonadotrophin ß subunit (hCGß+) develop prolactinomas, whereas hCGß+ males do not. The high levels of circulating hCG induce massive luteinization in the ovary of hCGß+ females, and progesterone becomes the primary steroid hormone produced, but estradiol remains at physiological level. The involvement of high levels of progesterone in lactotroph proliferation is not clearly understood; hence, the pathogenesis of prolactinomas in hCGß+ females remains unclear. TGFß1 is an inhibitor of lactotroph function, and the reduced TGFß1 activity found in prolactinomas has been proposed to be involved in tumor development. The aim of the present work was to study the role of TGFß1 in the gender-specific development of prolactinomas in hCGß+ mice. We compared the expression of different components of the pituitary TGFß1 system in males and females in this model. We found reduced TGFß1 levels, reduced expression of TGFß1 target genes, TGFß1 receptors, Ltbp1, Smad4 and Smad7 in hCGß+ female pituitaries. However, no differences were found between the transgenic and wild-type male pituitaries. We postulate that decreased pituitary TGFß1 activity in hCGß+ females is involved in the development of prolactinomas. In fact, we demonstrated that an in vivo treatment carried out for increasing pituitary TGFß1 activity, was successful in reducing the prolactinoma development, and the hyperprolactinemia in hCGß+ females. Moreover, the stronger TGFß1 system found in males could protect them from excessive lactotroph proliferation. Sex differences in the regulation of the pituitary TGFß1 system could explain gender differences in the incidence of prolactinoma.