The calcium sensing receptor (CaSR) is a class C G-protein-coupled receptor that is crucial for the feedback regulation of extracellular free ionised calcium homeostasis. While extracellular calcium (Ca(2+)o) is considered the primary physiological ligand, the CaSR is activated physiologically by a plethora of molecules including polyamines and l-amino acids. Activation of the CaSR by different ligands has the ability to stabilise unique conformations of the receptor, which may lead to preferential coupling of different G proteins; a phenomenon termed 'ligand-biased signalling'. While mutations of the CaSR are currently not linked with any malignancies, altered CaSR expression and function are associated with cancer progression. Interestingly, the CaSR appears to act both as a tumour suppressor and an oncogene, depending on the pathophysiology involved. Reduced expression of the CaSR occurs in both parathyroid and colon cancers, leading to loss of the growth suppressing effect of high Ca(2+)o. On the other hand, activation of the CaSR might facilitate metastasis to bone in breast and prostate cancer. A deeper understanding of the mechanisms driving CaSR signalling in different tissues, aided by a systems biology approach, will be instrumental in developing novel drugs that target the CaSR or its ligands in cancer. This article is part of a Special Issue entitled: 12th European Symposium on Calcium.

Calcium released in the bone microenvironment during remodeling is a major factor in regulating bone cells. Osteoblast and osteoclast proliferation, differentiation, and apoptosis are influenced by local extracellular calcium concentration. Thus, the calcium-sensing properties of skeletal cells can be exploited in order to modulate bone turnover and can explain the bone anabolic effects of agents developed and employed to revert osteoporosis.

Engineering brain organoids from human induced pluripotent stem cells (hiPSCs) is a powerful tool for modeling brain development and neurological disorders. Rett syndrome (RTT), a rare neurodevelopmental disorder, can greatly benefit from this technology, since it affects multiple neuronal subtypes in forebrain sub-regions. We have established dorsal and ventral forebrain organoids from control and RTT patient-specific hiPSCs recapitulating 3D organization and functional network complexity. Our data revealed a premature development of the deep-cortical layer, associated to the formation of TBR1 and CTIP2 neurons, and a lower expression of neural progenitor/proliferative cells in female RTT dorsal organoids. Moreover, calcium imaging and electrophysiology analysis demonstrated functional defects of RTT neurons. Additionally, assembly of RTT dorsal and ventral organoids revealed impairments of interneuron’s migration. Overall, our models provide a better understanding of RTT during early stages of neural development, demonstrating a great potential for personalized diagnosis and drug screening.

BackgroundThe prevalence of hypogonadism in HIV-infected patients is still a matter of debate as there is no standardized consensual diagnostic method. In addition, the etiology and endocrine/metabolic implications of hypogonadism in this population remain controversial. This study aims to determine the prevalence of testosterone deficiency in a single-site hospital and to evaluate its association with potential risk factors, lipodystrophy, metabolic syndrome, and cardiovascular risk.MethodsThis study analyzed 245 HIV-infected men on combined antiretroviral therapy. Patients with low total testosterone (TT) levels (<2.8 ng/mL) and/or low calculated free testosterone (FT) levels (<6.5 ng/dL) were considered testosterone deficient. According to their LH and FSH levels, patients were classified as having hypogonadotropic or hypergonadotropic dysfunction. Other clinical, anthropometric, and analytic parameters were also collected and analyzed.ResultsThe prevalence of testosterone deficiency in our population was 29.4 %. Among them, 56.9 % had hypogonadotropic dysfunction and 43.1 % presented with hypergonadotropic dysfunction. Patients with testosterone deficiency were older (p < 0.001), had higher HbA1c levels (p = 0.016) and higher systolic blood pressure (p = 0.007). Patients with lower testosterone levels had higher prevalence of isolated central fat accumulation (p = 0.015) and had higher median cardiovascular risk at 10 years as measured by the Framingham Risk Score (p = 0.004) and 10-Year ASCVD risk (p = 0.002).ConclusionsThe prevalence of testosterone deficiency in this HIV population is high, with hypogonadotropic dysfunction being responsible for the majority of cases. Testosterone deficiency might predispose to, or be involved, in the pathogenesis of HIV-associated lipodystrophy. Patients with low testosterone levels have higher cardiovascular risk, highlighting the importance of early diagnosis of this condition.