Mitochondrial membrane synthesis, remodelling and cellular trafficking.

Mitochondria are dynamic cellular organelles with complex roles in metabolism and signalling. Primary mitochondrial disorders are a group of approximately 400 monogenic disorders arising from pathogenic genetic variants impacting mitochondrial structure, ultrastructure and/or function. Amongst these disorders, defects of complex lipid biosynthesis, especially of the unique mitochondrial membrane lipid cardiolipin, and membrane biology are an emerging group characterised by clinical heterogeneity, but with recurrent features including cardiomyopathy, encephalopathy, neurodegeneration, neuropathy and 3-methylglutaconic aciduria. This review discusses lipid synthesis in the mitochondrial membrane, the mitochondrial contact site and cristae organising system (MICOS), mitochondrial dynamics and trafficking, and the disorders associated with defects of each of these processes. We highlight overlapping functions of proteins involved in lipid biosynthesis and protein import into the mitochondria, pointing to an overarching coordination and synchronisation of mitochondrial functions. This review also focuses on membrane interactions between mitochondria and other organelles, namely the endoplasmic reticulum, peroxisomes, lysosomes and lipid droplets. We signpost disorders of these membrane interactions that may explain the observation of secondary mitochondrial dysfunction in heterogeneous pathological processes. Disruption of these organellar interactions ultimately impairs cellular homeostasis and organismal health, highlighting the central role of mitochondria in human health and disease.

mRNA therapy corrects defective glutathione metabolism and restores ureagenesis in preclinical argininosuccinic aciduria.

The urea cycle enzyme argininosuccinate lyase (ASL) enables the clearance of neurotoxic ammonia and the biosynthesis of arginine. Patients with ASL deficiency present with argininosuccinic aciduria, an inherited metabolic disease with hyperammonemia and a systemic phenotype coinciding with neurocognitive impairment and chronic liver disease. Here, we describe the dysregulation of glutathione biosynthesis and upstream cysteine utilization in ASL-deficient patients and mice using targeted metabolomics and in vivo positron emission tomography (PET) imaging using (S)-4-(3-18F-fluoropropyl)-l-glutamate ([18F]FSPG). Up-regulation of cysteine metabolism contrasted with glutathione depletion and down-regulated antioxidant pathways. To assess hepatic glutathione dysregulation and liver disease, we present [18F]FSPG PET as a noninvasive diagnostic tool to monitor therapeutic response in argininosuccinic aciduria. Human hASL mRNA encapsulated in lipid nanoparticles improved glutathione metabolism and chronic liver disease. In addition, hASL mRNA therapy corrected and rescued the neonatal and adult Asl-deficient mouse phenotypes, respectively, enhancing ureagenesis. These findings provide mechanistic insights in liver glutathione metabolism and support clinical translation of mRNA therapy for argininosuccinic aciduria.

Atidarsagene autotemcel for metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is a rare autosomal recessive disorder of sphingolipid metabolism, due to a deficiency of the enzyme arylsulfatase A (ARSA). The main clinical signs of the disease are secondary to central and peripheral nervous system demyelination. MLD is subdivided into early- and late-onset subtypes based upon the onset of neurological disease. The early-onset subtype is associated with a more rapid progression of the disease that leads to death within the first decade of life. Until recently, no effective treatment was available for MLD. The blood-brain barrier (BBB) prevents systemically administered enzyme replacement therapy from reaching target cells in MLD. The evidence for the efficacy of hematopoietic stem cell transplantation is limited to the late-onset MLD subtype. Here, we review the preclinical and clinical studies that facilitated the approval of the ex vivo gene therapy atidarsagene autotemcel for early-onset MLD by the European Medicines Agency (EMA) in December 2020. This approach was studied in an animal model first and then in a clinical trial, eventually proving its efficacy in preventing disease manifestations in presymptomatic patients and stabilizing its progression in paucisymptomatic subjects. This new therapeutic consists of patients' CD34+ hematopoietic stem/progenitor cells (HSPCs) transduced with a lentiviral vector encoding functional ARSA cDNA. The gene-corrected cells get reinfused into the patients after a cycle of chemotherapy conditioning.

Hyperphosphatasia with mental retardation syndrome 3: Cerebrospinal fluid abnormalities and correction with pyridoxine and Folinic acid.

Glycosylphosphatidylinositol anchored proteins (GPI-APs) represent a class of molecules attached to the external leaflet of the plasma membrane by the GPI anchor where they play important roles in numerous cellular processes including neurogenesis, cell adhesion, immune response and signalling. Within the group of GPI anchor defects, six present with the clinical phenotype of Hyperphosphatasia with Mental Retardation Syndrome (HPMRS, Mabry Syndrome) characterized by moderate to severe intellectual disability, dysmorphic features, hypotonia, seizures and persistent hyperphosphatasia. We report the case of a 5-year-old female with global developmental delay associated with precocious puberty and persistently raised plasma alkaline phosphatase. Targeted next generation sequencing analysis of the HPMRS genes identified novel compound heterozygous variants in the PGAP2 gene (c.103del p.(Leu35Serfs*90)and c.134A > Gp.(His45Arg)) consistent with the diagnosis of HPMRS type 3. Cerebrospinal fluid (CSF) neurotransmitter analysis showed low levels of pyridoxal phosphate and 5-methyltetrahydrofolate and raised homovanillic acid. Supplementation with pyridoxine and folinic acid led to normalization of biochemical abnormalities. The patient continues to make developmental progress with significant improvement in speech and fine motor skills. Our reported case expands the clinical spectrum of HPMRS3 in which multisystem involvement is being increasingly recognized. Furthermore, it shows that miss-targeting GPI-APs and the effect on normal cellular function could provide a physiopathologic explanation for the CSF biochemical abnormalities with management implications for a group of disorders that currently has no treatment that can lead possibly to improved clinical outcomes.

Newborn Screening for Biotinidase Deficiency. The Experience of a Regional Center in Italy.

Introduction: Biotinidase deficiency (BD) is an autosomal recessive disease causing a defect in the biotin-releasing enzyme. Newborn screening (NBS) allows early diagnosis and treatment, ensuring excellent prognosis. The aim of this study was to describe our experience in the diagnosis, treatment, and follow-up showing key strategies and unsolved questions of the management of BD patients. Methods: We analyzed data of patients identified by the Regional Centre for Newborn Screening of Verona and followed by the Inherited Metabolic Disease Unit of Verona and Neonatal Intensive Care Unit of Bolzano, Italy, from 2014 to 2020. Results: Thirty-seven patients were diagnosed by NBS (five profound and 32 partial BD), with a total incidence of 1:5,996. All were started on biotin at diagnosis and presented no symptoms at follow-up. Analysis of parents and siblings led to identification of five asymptomatic patients with partial BD: one asymptomatic parent and four young siblings. Genetic analysis of the BTD gene identified 17 different genotypes and one mutation not previously known. Discussion: Our data confirm that NBS introduction had a dramatic impact on BD diagnosis, and the incidence has increased significantly compared to other areas. Partial defects are more common than profound and have a distinctive genotype. Partial BD treatment is still controversial even at what dose of biotin and for how long. At the end, BD treatment is very easy and inexpensive and prevents severe neurological damage. Sharing experiences is essential to achieving guidelines for treatment and follow-up and a better genotype-phenotype correlation.

Left spermatic vein retrograde sclerosis: comparison between sclerosant agent injection through a diagnostic catheter versus through an occluding balloon catheter.

PURPOSE: The aim of this study was to compare the technical success between left spermatic vein (LSV) scleroembolisation achieved with the injection of sclerosant through a diagnostic catheter and through an occluding balloon (OB), in the treatment of male varicocele. MATERIALS AND METHODS: From January 2012 to September 2013, we prospectively enrolled 100 patients with left varicocele and an indication for LSV scleroembolisation related to symptoms or spermiogram anomalies; patients were randomised to two groups (we wrote a list of 100 lines assigned casually with A or B and each patient was consecutively allocated to group A or B on the basis of this list). Patients in group A underwent injection of the sclerosing agent through an angiographic diagnostic catheter (free catheter technique) and patients in group B through an OB catheter (OB technique). In cases of incomplete occlusion of the LSV, the procedure was completed with coils. Total occlusion of the LSV at post-treatment phlebography during a Valsalva manoeuvre before any coil embolisation was considered a technical success. The rate of complications was also evaluated. The Fischer's test was used for statistical analysis. RESULTS: We evaluated a total of 90 patients because five patients for each group were not included in the statistical analysis owing to technical problems or complications. In group A we had a technical success of 75.6 versus 93.4 % in group B, and the difference was statistically significant (P = 0.003); in particular, we had to complete the embolisation with insertion of coils in 11 cases (24.4 %) in group A, and in three cases in group B (6.6 %). In group A, LSV rupture occurred in four cases (8 %) so the procedure was completed by sclerosant injection through the OB located distally to the lesion. These patients were not considered for evaluation. In another case, a high flow shunt towards the inferior vena cava was detected, so the patient underwent OB injection to stop the flow to the shunt, and was not included for statistical evaluation. In group B, vein rupture with contrast leakage was noted in six cases (12 %); nonetheless, all the procedures were completed because the OB was positioned distally to the vessel tear, obviating any retrograde leakage of sclerosant. In group B, in five cases (10 %), we were unable to advance the OB though the LSV ostium so the procedures were completed with the diagnostic catheter and not considered for statistical evaluation. CONCLUSION: On the basis of our data, the embolisation of the LSV obtained by injecting the sclerosant through an OB rather than through a diagnostic catheter seems to be more effective in achieving total vein embolisation, as well as allowing a controlled injection of sclerosant even in cases of vein rupture.

The use of microwaves ablation in the treatment of epiphyseal osteoid osteomas.

OBJECTIVE: This study was designed to demonstrate the feasibility and the reliability of microwave ablation (MWA) of epiphyseal osteoid osteomas (OO). MATERIALS AND METHODS: From February to November 2012, 7 patients (4 males and 3 females; age range 16-30 years) with epiphyseal OOs were treated with MWA. The treatment was performed with 16 G antennas with a power of 20 W for 2 min. The OOs were approached by using coaxial needles inserted with hammer or with automatic drill. All patients underwent spinal anaesthesia, with posttreatment 6-8 h observation before discharging. We treated epiphyseal OOs placed away from nervous and vascular nontarget structures, located in: femoral head (n = 2), femoral lesser trochanter (n = 2), femoral neck (n = 2), and proximal tibial epiphysis (n = 1). CT was used to visualize the nidus and to insert the needle for thermal ablation and for postprocedure control. Technical success was considered the positioning of the antenna in the nidus, while the efficacy of treatment was clinically evaluated as the complete remission of pain after the procedure by using the visual analogue score (VAS). Follow-up was performed by using VAS score 1 day, 1 week, and 1, 3, and 6 months after the procedure, whereas MRI examination was performed immediately after the procedure, at 1 month, and in any case of recurrence. Complications were also recorded. RESULTS: All patients experienced resolution of the symptomatology (VAS = 0) in ~1 week until the last follow-up, with residual VAS < 2 points occurring only from 1 to 7 days after the procedure. No intraprocedural complication was noted, whereas one patient had back pain for 2 months after the procedure, likely due to spinal analgesic injection. CONCLUSIONS: In our experience, MWA can be safely performed with excellent results without complications in selected cases of epiphyseal OOs; however, the clinical significance of this report is limited because there were only few patients included in this study. Thus, these data must be confirmed by further and larger studies.

Diffusion-weighted MRI in a liver protocol: its role in focal lesion detection.

AIM: To evaluate the role of diffusion-weighted imaging (DWI) in the detection of focal liver lesions (FLLs), using a conventional magnetic resonance imaging (MRI) protocol. METHODS: Fifty-two patients (22 males, average age 55.6 years, range: 25-82 years), studied using a 1.5 Tesla magnetic resonance scanner, were retrospectively analyzed; detection of FLLs was evaluated by considering the number of lesions observed with the following sequences: (1) respiratory-triggered diffusion-weighted single-shot echo-planar (DW SS-EP) sequences; (2) fat-suppressed fast spin-echo (fs-FSE) T2 weighted sequences; (3) steady-state free precession (SSFP) images; and (4) dynamic triphasic gadolinium-enhanced images, acquired with three-dimensional fast spoiled gradient-echo (3D FSPGR). Two radiologists independently reviewed the images: they were blinded to their respective reports. DW SS-EP sequences were compared to fs-FSE, SSFP and dynamic gadolinium-enhanced acquisitions using a t-test. Pairs were compared for the detection of: (1) all FLLs; (2) benign FLLs; (3) malignant FLLs; (4) metastases; and (5) hepatocellular carcinoma (HCC). RESULTS: Interobserver agreement was very good (weighted κ = 0.926, CI = 0.880-0.971); on the consensus reading, 277 FLLs were detected. In the comparison with fs-FSE, DW SS-EP sequences had a significantly higher score in the detection of all FLLs, benign FLLs, malignant FLLs and metastases; no statistical difference was observed in the detection of hepatocellular carcinoma (HCCs). In the comparison with SSFP sequences, DW SS-EP had significantly higher scores (P < 0.05) in the detection of all lesions, benign lesions, malignant lesions, metastases and HCC. All FLLs were better detected by dynamic 3D FSGR enhanced acquisition, with P = 0.0023 for reader 1 and P = 0.0086 for reader 2 in the comparison with DW SS-EP sequences; with reference to benign FLLs, DW SS-EP showed lower values than 3D FSPGR enhanced acquisition (P < 0.05). No statistical differences were observed in the detection of malignant lesions and metastases; considering HCCs, a very slight difference was reported by reader 1 (P = 0.049), whereas no difference was found by reader 2 (P = 0.06). CONCLUSION: In lesion detection, DWI had higher scores than T2 sequences; considering malignant FLLs, no statistical difference was observed between DWI and dynamic gadolinium images.

Venae comitantes as a potential vascular resource to create native arteriovenous fistulae.

PURPOSE: The arteriovenous fistula (AVF) represents the gold standard for hemodialysis (HD) vascular access. In some critical cases, use of the deep venous circle may represent an alternative approach and venae comitantes could be employed for this purpose. METHODS: Sixty patients with chronic renal failure in which the deep venous circle was used to create an AVF were identified; of the 48 who had a direct anastomosis between the brachial artery and vena comitans, 42 had a long-term follow-up (mean follow-up 59 weeks), while six were lost to follow-up. RESULTS: Immediate success (patency and palpable thrill) was achieved in 88% of cases (primary and early failure 12%). Primary accessibility rate was 62%, while 11 patients required a second surgical approach to make the vein accessible to needling. Secondary accessibility rate of 71% was due to surgical revisions. In the 80-week observation period, the complication rate was 10% with irreversible loss of the AVF in all these cases. Cumulative patency was 71% at the 80th week. Including all 42 patients, technical and functional success rate, defined as vein accessibility to needling and chance of an adequate HD treatment, was 62%. CONCLUSIONS: AVF employing venae comitantes may represent a suitable alternative in the absence of other vascular accesses for HD.

Atypical placement of hemodialysis catheters in patients with complete and irreversible obstruction of central venous vessels.

PURPOSE: This article describes the approach to atypical placement of central venous catheters (CVC) in dialysis patients with complete untreatable obstruction of central venous vessels. METHODS: Five patients with complete obstruction of central venous vessels underwent CT venography and digital venous angiography. After ultrasound-guided and radioscopic-assisted cannulation of the internal jugular vein, permanent CVCs were placed in atypical locations: in two patients a preliminary venous angioplasty was performed to facilitate the catheter positioning in a mediastinal enlarged collateral vein and in a persistent left superior vena cava; in three patients the CVC was placed in the azygos vein, enlarged because of the obstruction of the superior vena cava. RESULTS: In all cases, we achieved satisfactory morphological and functional immediate results. Hemodialysis (HD) was carried out long term in all patients except one who presented a non-functioning CVC after 4 months. In one case the catheter, still functioning well after 9 months, was removed due to kidney transplantation. The CVC in the left superior vena cava was replaced with a longer one after 12 months, and it is still functioning well 3 months after replacement. The patency of the other two catheters has to date been kept for 9 and 18 months. CONCLUSIONS: The placement of CVC for HD in atypical sites can be considered a viable option in extreme cases; adequate imaging support is paramount in order to facilitate the procedure and to avoid complications.