GNAS Epigenetic Defects and Pseudohypoparathyroidism: Time for a New Classification?

Pseudohypoparathyroidism-Ia and -Ib (PHP-Ia and -Ib) are caused by mutations in GNAS exons 1-13 and methylation defects in the imprinted GNAS cluster, respectively. PHP-Ia patients show Albright hereditary osteodystrophy (AHO), together with resistance to the action of different hormones that activate the Gs-coupled pathway. In PHP-Ib patients AHO is classically absent and hormone resistance is limited to PTH and TSH. This disorder is caused by GNAS methylation alterations with loss of imprinting at the exon A/B differentially methylated region (DMR) being the most consistent and recurrent defect. The familial form of the disease (AD-PHP-Ib) is typically associated with an isolated loss of imprinting at the exon A/B DMR due to microdeletions disrupting the upstream STX16 gene. In addition, deletions removing the entire NESP55 DMR, located within GNAS, associated with loss of all the maternal GNAS imprints have been identified in some AD-PHP-Ib kindreds. Conversely, most sporadic PHP-Ib cases have GNAS imprinting abnormalities that involve multiple DMRs, but the genetic lesion underlying these defects is unknown. Recently, methylation defects have been detected in a subset of patients with PHP-Ia and variable degrees of AHO, indicating a molecular overlap between the 2 forms. Imprinting defects do not seem to be associated with the severity of AHO neither with specific AHO signs. In conclusion, the latest findings on the molecular basis underlying these defects suggest the existence of a clinical and genetic/epigenetic overlap between PHP-Ia and PHP-Ib, and highlight the necessity of a new clinical classification of these disorders based on molecular findings.     

Optimising Controlled Human Malaria Infection Studies Using Cryopreserved P. falciparum Parasites Administered by Needle and Syringe

Background

Controlled human malaria infection (CHMI) studies have become a routine tool to evaluate efficacy of candidate anti-malarial drugs and vaccines. To date, CHMI trials have mostly been conducted using the bite of infected mosquitoes, restricting the number of trial sites that can perform CHMI studies. Aseptic, cryopreserved P. falciparum sporozoites (PfSPZ Challenge) provide a potentially more accurate, reproducible and practical alternative, allowing a known number of sporozoites to be administered simply by injection.

Methodology

We sought to assess the infectivity of PfSPZ Challenge administered in different dosing regimens to malaria-naive healthy adults (n = 18). Six participants received 2,500 sporozoites intradermally (ID), six received 2,500 sporozoites intramuscularly (IM) and six received 25,000 sporozoites IM.

Findings

Five out of six participants receiving 2,500 sporozoites ID, 3/6 participants receiving 2,500 sporozoites IM and 6/6 participants receiving 25,000 sporozoites IM were successfully infected. The median time to diagnosis was 13.2, 17.8 and 12.7 days for 2,500 sporozoites ID, 2,500 sporozoites IM and 25,000 sporozoites IM respectively (Kaplan Meier method; p = 0.024 log rank test).

Conclusions

2,500 sporozoites ID and 25,000 sporozoites IM have similar infectivities. Given the dose response in infectivity seen with IM administration, further work should evaluate increasing doses of PfSPZ Challenge IM to identify a dosing regimen that reliably infects 100% of participants.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01465048","term_id":"NCT01465048"}}NCT01465048     

Development of an injectable composite for bone regeneration

With the development of minimally invasive surgical techniques, there is a growing interest in the research and development of injectable biomaterials especially for orthopedic applications. In a view to enhance the overall surgery benefits for the patient, the BIOSINJECT project aims at preparing a new generation of mineral-organic composites for bone regeneration exhibiting bioactivity, therapeutic activity and easiness of use to broaden the application domains of the actual bone mineral cements and propose an alternative strategy with regard to their poor resorbability, injectability difficulties and risk of infection. First, a physical-chemical study demonstrated the feasibility of self-setting injectable composites associating calcium carbonate-calcium phosphate cement and polysaccharides (tailor-made or commercial polymer) in the presence or not of an antibacterial agent within the composite formulation. Then, bone cell response and antimicrobial activity of the composite have been evaluated in vitro. Finally, in order to evaluate resorption rate and bone tissue response an animal study has been performed and the histological analysis is still in progress. These multidisciplinary and complementary studies led to promising results in a view of the industrial development of such composite for dental and orthopaedic applications.     

Mine, yours, ours? Sharing data on human genetic variation

The achievement of a robust, effective and responsible form of data sharing is currently regarded as a priority for biological and bio-medical research. Empirical evaluations of data sharing may be regarded as an indispensable first step in the identification of critical aspects and the development of strategies aimed at increasing availability of research data for the scientific community as a whole. Research concerning human genetic variation represents a potential forerunner in the establishment of widespread sharing of primary datasets. However, no specific analysis has been conducted to date in order to ascertain whether the sharing of primary datasets is common-practice in this research field. To this aim, we analyzed a total of 543 mitochondrial and Y chromosomal datasets reported in 508 papers indexed in the Pubmed database from 2008 to 2011. A substantial portion of datasets (21.9%) was found to have been withheld, while neither strong editorial policies nor high impact factor proved to be effective in increasing the sharing rate beyond the current figure of 80.5%. Disaggregating datasets for research fields, we could observe a substantially lower sharing in medical than evolutionary and forensic genetics, more evident for whole mtDNA sequences (15.0% vs 99.6%). The low rate of positive responses to e-mail requests sent to corresponding authors of withheld datasets (28.6%) suggests that sharing should be regarded as a prerequisite for final paper acceptance, while making authors deposit their results in open online databases which provide data quality control seems to provide the best-practice standard. Finally, we estimated that 29.8% to 32.9% of total resources are used to generate withheld datasets, implying that an important portion of research funding does not produce shared knowledge. By making the scientific community and the public aware of this important aspect, we may help popularize a more effective culture of data sharing.     

B-cell depletion therapy in patients with diffuse systemic sclerosis associates with a significant decrease in PDGFR expression and activation in spindle-like cells in the skin

Introduction

Recently, several studies assessing the clinical efficacy of rituximab (RTX) in systemic sclerosis (SSc) have reported encouraging results. We aimed at exploring whether RTX exerts its beneficial effects on fibrosis through attenuation of platelet-derived growth factor receptor (PDGFR) pathway activation.

Methods

We immunohistochemically assessed skin biopsies obtained from eight patients with SSc prior to and 6 months following RTX treatment, three control SSc patients (at the same time points) and three healthy subjects. We assessed the expression of platelet-derived growth factor, PDGFR and phosphorylated (activated) PDGFR.

Results

We found a strong correlation of PDGFRα and PDGFRβ expression on spindle-like cells and collagen deposition in SSc biopsies (r = 0.97 and r = 0.96 for PDGFRα and PDGFRβ, respectively; P < 0.0001 for both), indicating a strong link between PDGFR expression and fibrosis. Expression of PDGFRα and PDGFRβ in the papillary dermis significantly decreased following RTX administration (mean ± standard error of the mean at baseline vs. 6 months, respectively: PDGFRα, 42.05 ± 5.03 vs. 26.85 ± 3.00, P = 0.004; and PDGFRβ, 37.14 ± 4.94 vs. 24.01 ± 3.27, P = 0.012). Similarly, expression of phosphorylated PDGFRα and PDGFRβ in the papillary dermis significantly decreased following RTX administration (P = 0.006 and P = 0.013 for phospho-PDGFRα and phospho-PDGFRβ, respectively). No changes in platelet-derived growth factor tissue expression or serum levels were found following RTX treatment.

Conclusion

RTX may favorably affect skin fibrosis through attenuation of PDGFR expression and activation, a finding that supports a disease-modifying role of RTX in SSc. Large-scale, multicenter studies are needed to further explore the efficacy of RTX in SSc.     

Type 2 diabetes alters mesenchymal stem cell secretome composition and angiogenic properties

This study aimed at characterizing the impact of type 2 diabetes mellitus (T2DM) on the bone marrow mesenchymal stem cell (BMMSC) secretome and angiogenic properties. BMMSCs from Zucker diabetic fatty rats (ZDF) (a T2DM model) and Zucker LEAN littermates (control) were cultured. The supernatant conditioned media (CM) from BMMSCs of diabetic and control rats were collected and analysed. Compared to results obtained using CM from LEAN‐BMMSCs, the bioactive content of ZDF‐BMMSC CM (i) differently affects endothelial cell (HUVEC) functions in vitro by inducing increased (3.5‐fold; P < 0.01) formation of tubule‐like structures and migration of these cells (3‐fold; P < 0.001), as well as promotes improved vascular formation in vivo, and (ii) contains different levels of angiogenic factors (e.g. IGF1) and mediators, such as OSTP, CATD, FMOD LTBP1 and LTBP2, which are involved in angiogenesis and/or extracellular matrix composition. Addition of neutralizing antibodies against IGF‐1, LTBP1 or LTBP2 in the CM of BMMSCs from diabetic rats decreased its stimulatory effect on HUVEC migration by approximately 60%, 40% or 40%, respectively. These results demonstrate that BMMSCs from T2DM rats have a unique secretome with distinct angiogenic properties and provide new insights into the role of BMMSCs in aberrant angiogenesis in the diabetic milieu.