Pharmacological elevation of sphingosine-1-phosphate by S1P lyase inhibition accelerates bone regeneration after post-traumatic osteomyelitis

Posttraumatic osteomyelitis and the ensuing bone defects are a debilitating complication after open fractures with little therapeutic options. We have recently identified potent osteoanabolic effects of sphingosine-1-phosphate (S1P) signalling and have now tested whether it may beneficially affect bone regeneration after infection. We employed pharmacological S1P lyase inhibition by 4-deoxypyrodoxin (DOP) to raise S1P levels in vivo in an unicortical long bone defect model of posttraumatic osteomyelitis in mice. In a translational approach, human bone specimens of clinical osteomyelitis patients were treated in organ culture in vitro with DOP. Bone regeneration was assessed by μCT, histomorphometry, immunohistology and gene expression analysis. The role of S1P receptors was addressed using S1PR3 deficient mice. Here, we present data that DOP treatment markedly enhanced osteogenesis in posttraumatic osteomyelitis. This was accompanied by greatly improved osteoblastogenesis and enhanced angiogenesis in the callus accompanied by osteoclast-mediated bone remodelling. We also identified the target of increased S1P to be the S1PR3 as S1PR3-/- mice showed no improvement of bone regeneration by DOP. In the human bone explants, bone mass significantly increased along with enhanced osteoblastogenesis and angiogenesis. Our data suggest that enhancement of S1P/S1PR3 signalling may be a promising therapeutic target for bone regeneration in posttraumatic osteomyelitis.

Molecular and Functional Relevance of NaV1.8-Induced Atrial Arrhythmogenic Triggers in a Human SCN10A Knock-Out Stem Cell Model

In heart failure and atrial fibrillation, a persistent Na⁺ current (I_NaL) exerts detrimental effects on cellular electrophysiology and can induce arrhythmias. We have recently shown that Na_V1.8 contributes to arrhythmogenesis by inducing a I_NaL. Genome-wide association studies indicate that mutations in the SCN10A gene (Na_V1.8) are associated with increased risk for arrhythmias, Brugada syndrome, and sudden cardiac death. However, the mediation of these Na_V1.8-related effects, whether through cardiac ganglia or cardiomyocytes, is still a subject of controversial discussion. We used CRISPR/Cas9 technology to generate homozygous atrial SCN10A-KO-iPSC-CMs. Ruptured-patch whole-cell patch-clamp was used to measure the I_NaL and action potential duration. Ca²⁺ measurements (Fluo 4-AM) were performed to analyze proarrhythmogenic diastolic SR Ca²⁺ leak. The I_NaL was significantly reduced in atrial SCN10A KO CMs as well as after specific pharmacological inhibition of Na_V1.8. No effects on atrial APD₉₀ were detected in any groups. Both SCN10A KO and specific blockers of Na_V1.8 led to decreased Ca²⁺ spark frequency and a significant reduction of arrhythmogenic Ca²⁺ waves. Our experiments demonstrate that Na_V1.8 contributes to I_NaL formation in human atrial CMs and that Na_V1.8 inhibition modulates proarrhythmogenic triggers in human atrial CMs and therefore Na_V1.8 could be a new target for antiarrhythmic strategies.

Study protocol for a pilot trial analysing the usability, validity and safety of an interventional health app programme for the structured prehabilitation of patients before major surgical interventions: the PROTEGO MAXIMA trial

INTRODUCTION

Major surgery is associated with a high risk for postoperative complications, leading to an increase in mortality and morbidity, particularly in frail patients with a reduced cardiopulmonary reserve. Prehabilitation, including aerobic exercise training, aims to improve patients' physical fitness before major surgery and reduce postoperative complications, length of hospital stay and costs. The purpose of the study is to assess the usability, validity and safety of an app-based endurance exercise software in accordance with the Medical Device Regulation using wrist-worn wearables to measure heart rate (HR) and distance.

METHODS AND ANALYSIS

The PROTEGO MAXIMA trial is a prospective, interventional study with patients undergoing major elective surgery, comprising three tasks. Tasks I and II aim to assess the usability of the app, using evaluation questionnaires and usability scenarios. In Task IIIa, patients will undergo a structured risk assessment by the Patronus App, which will be correlated with the occurrence of postoperative complications after 90 days (non-interventional). In Task IIIb, healthy students and patients will perform a supervised 6 min walking test and a 37 min interval training on a treadmill based on HR reserve, wearing standard ECG limb leads and two smartwatches, which will be driven by the test software. The aim of this task is to assess the accuracy of HR measurement by the wearables and the safety, using specific alarm settings of the devices and lab testing of the participants (interventional).

ETHICS AND DISSEMINATION

Ethical approval was granted by the Institutional Review Board of the University Hospital of Frankfurt and by the Federal Institute for Pharmaceuticals and Medical Products (BfArM, reference number 94.1.04-5660-13655) on 7 February 2022. The results from this study will be submitted to peer-reviewed journals and reported at suitable national and international meetings.

TRIAL REGISTRATION NUMBERS

European Database on Medical Devices (CIV-21-07-037311) and German Clinical Trial Registry (DRKS00026985).