Signalling pathways in stem-like cells of the hypothalamic-pituitary-adrenal (HPA) axis during stress and metabolic changes
PhD student: Ilona Berger
Supervisor at TUD: Charlotte Steenblock, Stefan Bornstein
Supervisor at KCL: Cynthia Andoniadou
Start date: 01.02.2018 Date of defense: 19.11.2021 Joint PhD
We encounter stress very often in our daily life. This can have both positive and negative effects on our well-being. While acute stress can have a motivating or performance-enhancing effect, chronic stress usually becomes a burden and has been linked with mental illnesses such as depression, but also systemic diseases like diabetes. The body reacts to stress by activating the hypothalamic-pituitary-adrenal axis, or so-called endocrine stress system, which controls the targeted release of stress hormones. These hormones enable the increased energy requirement in stress and regulate their own activity via negative feedback. The stress response is therefore an essential network and requires precise regulation. It has been shown that chronic stress or early childhood stress can permanently change this system, which can result in a higher probability of disease development. The underlying causes for this have not yet been fully clarified.
One theory suggests that stem cells residing in endocrine organs such as the hypothalamus, pituitary gland, and adrenal gland, may be involved in chronic changes through their plasticity in response to external stimuli but the influence of stress on these cells is largely unknown. The stem cells of these organs have different origins and characteristics, hence cannot be directly compared with one another. However, there is evidence that these populations are regulated by a pathway that has previously been associated with stress and stress disorders, the YAP/TAZ signalling cascade. The aim of this study was therefore to clarify whether this signalling pathway in the pituitary gland and adrenal cortex is influenced by stress and whether this leads to a regulation of the stem cells in the respective organs.
Regulation of stem cell populations during stress was characterised by using an in vivo restraint stress paradigm. Further, molecular methods, including RT-qPCR, RNAscope mRNA in situ hybridisation, western blot and immunofluorescence were performed. Spheroid and clonogenic colony cultures of adrenal and pituitary stem-/progenitor cells, respectively, were performed to further classify their regulation.
The YAP/TAZ pathway was first analysed in detail in the adrenal cortex. The data revealed that the components of the cascade were expressed in the entire adrenal cortex, whereas the transcription factor YAP was mainly active in the outermost cell layers, where the stem cells are also located. YAP and classic target genes like Ctgf were also found in cells defined as progenitor cells or stem cells. A stress experiment showed that particularly Ctgf expression was increased in the stem cell niche. Progenitor cells in the adrenal cortex are normally mainly regulated by the WNT signalling pathway, which is inhibited by stress. Since this was shown in previous studies as an important step in the formation of new cells from the progenitor cells, adrenal glands of glucocorticoid-treated mice, which show adrenal cortical atrophy, were also analysed. These showed an activity of the two pathways that was contrary to stress. These results were confirmed in an in vitro cell differentiation model.
The same stress protocol as above was used to analyse the regulation of the YAP/TAZ signalling pathway in the anterior pituitary. The stem cell population in the pituitary gland is generally defined by the marker SOX2 and is, among others, regulated by the YAP/TAZ signalling pathway. Repeated stress led to greatly increased gene expression of classic YAP/TAZ target genes Ctgf and Cyr61. Both were expressed in the SOX2+ cells of the anterior pituitary, which suggested a potential influence of stress on SOX2+ cells. The data implied that these cells did not exhibit increased proliferation or differentiation in response to stress. Rather, in vitro studies revealed that SOX2+ cells secreted CTGF to potentially influence neighbouring cells via paracrine signalling. Further investigations demonstrated that glucocorticoids stimulated expression of Ctgf and the secretion of the signal peptide in the SOX2+ cell population. These results suggest that the negative feedback from the adrenal gland during stress could also influence stem cells in the pituitary gland, which in turn could play a role in the regulation of hormone-producing cells via paracrine signalling.
In summary, the present work demonstrates that stress can have an influence on signalling pathways in the endocrine stress axis, which can influence precursor cell populations in different organs. This could have various consequences for the respective organ and progenitor cells could influence the stress response in general. These results exemplify that a more extensive understanding of the regulation of stem cells in stress may be required to understand the underlying causes of disease development favoured by chronic or early life stress.
Publications:
Oxytocin alters the morphology of hypothalamic neurons via the transcription factor myocyte enhancer factor 2A (MEF‑2A). M. Meyer, I. Berger, J. Winter, B. Jurek. Mol Cell Endocrinol. 2018;477:156-162.
Isolation and characterization of adrenocortical progenitors involved in the adaptation to stress. C. Steenblock, M.F. Rubin de Celis, L.F. Delgadillo Silva, V. Pawolski, A. Brennand, M. Werdermann, I. Berger, A. Santambrogio, M. Peitzsch, C.L. Andoniadou, A.V. Schally, S.R. Bornstein. Proc Natl Acad Sci U S A. 2018;115:12997-13002.
The adrenal gland in stress - Adaptation on a cellular level. I. Berger*, M. Werdermann*, S.R. Bornstein, C. Steenblock. J Steroid Biochem Mol Biol. 2019;190:198-206.
Adrenal cortex–medulla interactions in adaptation to stress and disease. S.R. Bornstein, I. Berger, L. Scriba, A. Santambrogio, C. Steenblock. Curr Opin Endocr Metab Res. 2019;8:9-14.
Stress-inducible-stem cells: a new view on endocrine, metabolic and mental disease? S.R. Bornstein, C. Steenblock, G.P. Chrousos, A.V. Schally, F. Beuschlein, G. Kline, N.P. Krone, J. Licinio, M.L. Wong, E. Ullmann, G. Ruiz-Babot, B.O. Boehm, A. Behrens, A. Brennand, A. Santambrogio, I. Berger, M. Werdermann, R. Sancho, A. Linkermann, J.W. Lenders, G. Eisenhofer, C.L. Andoniadou. Mol Psychiatry. 2019;24:2-9.
Are Nestin-positive cells responsive to stress? S.R. Bornstein, I. Berger, C. Steenblock. Stress. 2020;1-5.
Adrenal medulla development and medullary-cortical interactions. N. Bechmann, I. Berger, S.R. Bornstein, C. Steenblock. Mol Cell Endocrinol. 2021;528:111258.
Viral infiltration of pancreatic islets in patients with COVID-19. C. Steenblock, S. Richter, I. Berger, M. Barovic, J. Schmid, U. Schubert, N. Jarzebska, A. von Mässenhausen, A. Linkermann, A. Schürmann, J. Pablik, T. Dienemann, K. Evert, R.N. Rodionov, N. Semenova, V. Zinslering, R. Gainetdinov, G. Baretton, D. Lindemann, M. Solimena, B. Ludwig, S.R. Bornstein. Nat Commun. 2021.
Insulin and obesity transform hypothalamic-pituitary-adrenal axis stemness and function in a hyperactive state. M. Werdermann, I. Berger, L.D. Scriba, A. Santambrogio, P. Schlinkert, H. Brendel, H. Morawietz, A. Schedl, M. Peitzsch, A.J.F. King, C.L. Andoniadou, S.R. Bornstein, C. Steenblock. Mol Metab. 2021;43:101112.
Chronic oxytocin-driven alternative splicing of CRFR2α induces anxiety. J. Winter, M. Meyer, I. Berger, S. Peters, M. Royer, M. Bianchi, S. Stang, D. Langgartner, S.O. Reber, K. Kuffner, A.K. Schmidtner, F. Hartmann, A. Bludau, O.J. Bosch, D.A. Slattery, E.H. Van den Burg, B. Jurek, I.D. Neumann. Mol Psychiatry. 2021.