Mecanismos moleculares de la latencia viral. Papel del factor de transcripción HIVEP3

La infección por el virus del SIDA continua siendo una de las mayores amenzas a escala mundial. Los últimos informes muestran que al menos 33 millones de personas vivían infectados por SIDA al final de 2008, y que casi 3 millones de nuevos infectados aparecen cada año. Gracias al esfuerzo de la comunidad científica desde el inicio de la enfermedad, se han logrado identificar los distintos pasos del ciclo de replicación viral, y se han desarrollado medicinas que inhiben enzimas virales claves en cada uno de estos pasos. Estos medicamentos constituyen la base del tratamiento actual para los enfermos de SIDA, conocida como TARGA (Terapia AntiRetroviral de Gran Actividad). Esta terapia consigue una disminución de las copias virales en el plasma de los infectados hasta niveles indetectables después de unos meses de tratamiento. Sin embargo, esta terapia no tiene efecto sobre el virus en su forma latente, el cual se encuentra en células y tejidos específicos formando lo que se conoce como reservorio viral. Existen pruebas que vinculan estos reservorios como los responsables de la rápida multiplicación del virus en pacientes que cesan en el tratamiento antiretroviral, incluso después de muchos años bajo el mismo. Es por esto, que actualmente es necesario mantener el tratamiento con TARGA de por vida en estos pacientes

Towards targeting overactive BMP signaling in Fibrodysplasia Ossificans Progressiva

Fibrodysplasia Ossificans Progressiva (FOP) is a rare monogenetic disorder in which patients develop heterotopic ossification (HO). A heterozygous mutation in BMP type I receptor ALK2 results in hyper-sensitized BMP signaling. The aim of this study is to identify small molecules which can selectively inhibit this overactive BMP pathway. Thirteen FDA-approved small molecules were tested on their effect on BMP6-induced target gene expression, alkaline phosphatase activity and mineralization in KS483 cells. We identified cryptotanshinone as a small molecule able to inhibit BMP signaling. In conclusion, cryptotanshinone could be a novel small molecule inhibitor of the overactive BMP signaling pathway in FOP

Promiscuous signaling of ligands via mutant ALK2 in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare hereditary disorder characterized by successive heterotopic bone formation, for which at present there is no therapy. Mutations in the bone morphogenetic protein (BMP) type I receptor Activin receptor-like kinase 2 (ACVR1/ALK2) are the main trigger for FOP and inflammation is thought to be the secondary hit. The single nucleotide mutation at position 617 in the cDNA ALK2 sequence, which is found in 98% of FOP patients, results in a R206H change in the intracellular juxtamembrane region of ALK2. Previous studies had revealed that this mutation perturbs the interaction with the negative regulator FKBP12, thereby sensitising cells expressing this mutant receptor to BMPs, which are potent inducers of cartilage and bone formation. Recently, however, a twist in the underlying mechanism of FOP was revealed. Mutant ALK2 was found to respond to Activin-A, whereas wild type ALK2 function is inhibited by Activin-A. The latter cytokine is induced locally upon tissue damage and inflammation. Moreover, therapeutic targeting of Activin-A was found to inhibit heterotopic ossification in a mutant ALK2 knock-in mouse model that is highly reminiscent to human FOP. This review will focus on these latest surprising findings and discuss the implication for treatment of FOP patients

Human iPSCs as model systems for BMP-related rare diseases

This article belongs to the Special Issue iPS Cells (iPSCs) for Modelling and Treatment of Human Diseases 2022.Disturbances in bone morphogenetic protein (BMP) signalling contribute to onset and development of a number of rare genetic diseases, including Fibrodysplasia ossificans progressiva (FOP), Pulmonary arterial hypertension (PAH), and Hereditary haemorrhagic telangiectasia (HHT). After decades of animal research to build a solid foundation in understanding the underlying molecular mechanisms, the progressive implementation of iPSC-based patient-derived models will improve drug development by addressing drug efficacy, specificity, and toxicity in a complex humanized environment. We will review the current state of literature on iPSC-derived model systems in this field, with special emphasis on the access to patient source material and the complications that may come with it. Given the essential role of BMPs during embryonic development and stem cell differentiation, gain- or loss-of-function mutations in the BMP signalling pathway may compromise iPSC generation, maintenance, and differentiation procedures. This review highlights the need for careful optimization of the protocols used. Finally, we will discuss recent developments towards complex in vitro culture models aiming to resemble specific tissue microenvironments with multi-faceted cellular inputs, such as cell mechanics and ECM together with organoids, organ-on-chip, and microfluidic technologies.C.H. was funded by “The Open Access Publication Fund of the Westphalian University of Applied Sciences” as well as the 5th Research Challenge on Sustainability (Internal program for science promotion of a sustainable future by the Westphalian University of Applied Sciences). G.S.-D. is sponsored by Fundació La Marató de TV3 (#202038), the Spanish Ministry of Science, through the Ramón y Cajal grants RYC2021-030866-I and PID2022-141212OA-I00, and the BHF-DZHK-DHF, 2022/23 award PROMETHEUS. Both authors would like to thank the Scientific Research Network by the Research Foundation–Flanders (WOG W0014200N) and An Zwijsen.Peer reviewe

Promiscuous signaling of ligands via mutant ALK2 in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare hereditary disorder characterized by successive heterotopic bone formation, for which at present there is no therapy. Mutations in the bone morphogenetic protein (BMP) type I receptor Activin receptor-like kinase 2 (ACVR1/ALK2) are the main trigger for FOP and inflammation is thought to be the secondary hit. The single nucleotide mutation at position 617 in the cDNA ALK2 sequence, which is found in 98% of FOP patients, results in a R206H change in the intracellular juxtamembrane region of ALK2. Previous studies had revealed that this mutation perturbs the interaction with the negative regulator FKBP12, thereby sensitising cells expressing this mutant receptor to BMPs, which are potent inducers of cartilage and bone formation. Recently, however, a twist in the underlying mechanism of FOP was revealed. Mutant ALK2 was found to respond to Activin-A, whereas wild type ALK2 function is inhibited by Activin-A. The latter cytokine is induced locally upon tissue damage and inflammation. Moreover, therapeutic targeting of Activin-A was found to inhibit heterotopic ossification in a mutant ALK2 knock-in mouse model that is highly reminiscent to human FOP. This review will focus on these latest surprising findings and discuss the implication for treatment of FOP patients

Sex-biased TGFβ signalling in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare cardiovascular disorder leading to pulmonary hypertension and, often fatal, right heart failure. Sex differences in PAH are evident, which primarily presents with a female predominance and increased male severity. Disturbed signalling of the transforming growth factor-β (TGFβ) family and gene mutations in the bone morphogenetic protein receptor 2 (BMPR2) are risk factors for PAH development, but how sex-specific cues affect the TGFβ family signalling in PAH remains poorly understood. In this review, we aim to explore the sex bias in PAH by examining sex differences in the TGFβ signalling family through mechanistical and translational evidence. Sex hormones including oestrogens, progestogens, and androgens, can determine the expression of receptors (including BMPR2), ligands, and soluble antagonists within the TGFβ family in a tissue-specific manner. Furthermore, sex-related genetic processes, i.e. Y-chromosome expression and X-chromosome inactivation, can influence the TGFβ signalling family at multiple levels. Given the clinical and mechanistical similarities, we expect that the conclusions arising from this review may apply also to hereditary haemorrhagic telangiectasia (HHT), a rare vascular disorder affecting the TGFβ signalling family pathway. In summary, we anticipate that investigating the TGFβ signalling family in a sex-specific manner will contribute to further understand the underlying processes leading to PAH and likely HHT.Our research is supported by the Dutch Cardiovascular Alliance (Hartstichting, Nederlandse Federatie van Universitair Medische Centra (NFU), Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Koninklijke Nederlandse Akademie van Wetenschappen), PHAEDRA-IMPACT (CVON-2018-29) and DOLPHIN-GENESIS (CVON-2017-10). GSD is also sponsored by Fundació La Marato de TV3 (grant #202038), the Spanish Ministerio de Ciencia e Innovación (“Ramon y Cajal” grant RYC2021-030866-I and PID2022-141212OA-I00). GSD and FdM are supported by the BHF-DZHK-DHF, 2022/23 award PROMETHEUS.Peer reviewe

TGF-Beta Induces Activin A Production in Dermal Fibroblasts Derived from Patients with Fibrodysplasia Ossificans Progressiva

Fibrodysplasia ossificans progressiva (FOP) is a catastrophic, ultra-rare disease of heterotopic ossification caused by genetic defects in the ACVR1 gene. The mutant ACVR1 receptor, when triggered by an inflammatory process, leads to heterotopic ossification of the muscles and ligaments. Activin A has been discovered as the main osteogenic ligand of the FOP ACVR1 receptor. However, the source of Activin A itself and the trigger of its production in FOP individuals have remained elusive. We used primary dermal fibroblasts from five FOP patients to investigate Activin A production and how this is influenced by inflammatory cytokines in FOP. FOP fibroblasts showed elevated Activin A production compared to healthy controls, both in standard culture and osteogenic transdifferentiation conditions. We discovered TGFβ1 to be an FOP-specific stimulant of Activin A, shown by the upregulation of the INHBA gene and protein expression. Activin A and TGFβ1 were both induced by BMP4 in FOP and control fibroblasts. Treatment with TNFα and IL6 produced negligible levels of Activin A and TGFβ1 in both cell groups. We present for the first time TGFβ1 as a triggering factor of Activin A production in FOP. As TGFβ1 can promote the induction of the main driver of FOP, TGFβ1 could also be considered a possible therapeutic target in FOP treatment

TGF-Beta Induces Activin A Production in Dermal Fibroblasts Derived from Patients with Fibrodysplasia Ossificans Progressiva

Fibrodysplasia ossificans progressiva (FOP) is a catastrophic, ultra-rare disease of heterotopic ossification caused by genetic defects in the ACVR1 gene. The mutant ACVR1 receptor, when triggered by an inflammatory process, leads to heterotopic ossification of the muscles and ligaments. Activin A has been discovered as the main osteogenic ligand of the FOP ACVR1 receptor. However, the source of Activin A itself and the trigger of its production in FOP individuals have remained elusive. We used primary dermal fibroblasts from five FOP patients to investigate Activin A production and how this is influenced by inflammatory cytokines in FOP. FOP fibroblasts showed elevated Activin A production compared to healthy controls, both in standard culture and osteogenic transdifferentiation conditions. We discovered TGFβ1 to be an FOP-specific stimulant of Activin A, shown by the upregulation of the INHBA gene and protein expression. Activin A and TGFβ1 were both induced by BMP4 in FOP and control fibroblasts. Treatment with TNFα and IL6 produced negligible levels of Activin A and TGFβ1 in both cell groups. We present for the first time TGFβ1 as a triggering factor of Activin A production in FOP. As TGFβ1 can promote the induction of the main driver of FOP, TGFβ1 could also be considered a possible therapeutic target in FOP treatment