The Impact of Intraventricular Hemorrhage and Periventricular Leukomalacia on Mortality and Neurodevelopmental Outcome in Very Preterm and Very Low Birthweight Infants: A Prospective Population-based Cohort Study.

OBJECTIVE: To survey the incidence of intraventricular hemorrhage (IVH) and periventricular leukomalacia (PVL) by gestational age and to report the impact on mortality and neurodevelopmental outcome in very preterm/very low birthweight infants. STUDY DESIGN: This was a population-based cohort study of 1927 very preterm/very low birthweight infants born in 2014-2016 and admitted to Flemish neonatal intensive care units. Infants underwent standard follow-up assessment until 2 years corrected age with the Bayley Scales of Infant and Toddler Development and neurological assessments. RESULTS: No brain lesion was present in 31% of infants born at <26 weeks of gestation and 75.8% in infants born at 29-32 weeks of gestation. The prevalence of low-grade IVH/PVL (grades I and II) was 16.8% and 12.7%, respectively. Low-grade IVH/PVL was not related significantly to an increased likelihood of mortality, motor delay, or cognitive delay, except for PVL grade II, which was associated with a 4-fold increase in developing cerebral palsy (OR, 4.1; 95% CI, 1.2-14.6). High-grade lesions (III-IV) were present in 22.0% of the infants born at <26 weeks of gestational and 3.1% at 29-32 weeks of gestation, and the odds of death were ≥14.0 (IVH: OR, 14.0; 95% CI, 9.0-21.9; PVL: OR, 14.1; 95% CI, 6.6-29.9). PVL grades III-IV showed an increased odds of 17.2 for motor delay and 12.3 for cerebral palsy, but were not found to be associated significantly with cognitive delay (OR, 2.9; 95% CI, 0.5-17.5; P = .24). CONCLUSIONS: Both the prevalence and severity of IVH/PVL decreased significantly with advancing gestational age. More than 75% of all infants with low grades of IVH/PVL showed normal motor and cognitive outcome at 2 years corrected age. High-grade PVL/IVH has become less common and is associated with adverse outcomes.

Metachromatic leukodystrophy: To screen or not to screen?

Metachromatic leukodystrophy (MLD) is a neurodegenerative lysosomal storage disorder caused by biallelic pathogenic variants in the gene encoding arylsulfatase A. Disease onset is variable (with late infantile, early and late juvenile, and adult forms) and treatment options depend on age and disease symptoms at onset. In the past, allo-hematopoietic stem cell transplantation (allo-HSCT) has been the best treatment option, following strict selection criteria. The outcome however is variable and morbidity remains high. This paved the way to the development of new treatment options, some of them aiming to be curative. In the light of this changing therapeutic field, newborn screening is becoming a valuable option. This narrative review aims to describe the outcome of allo-HSCT in the different MLD disease forms, and, in addition, reviews new treatment options. Finally, the shift of the field towards newborn screening for MLD is discussed.

MPS I: Early diagnosis, bone disease and treatment, where are we now?

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disorder characterized by α-L-iduronidase deficiency. Patients present with a broad spectrum of disease severity ranging from the most severe phenotype (Hurler) with devastating neurocognitive decline, bone disease and early death to intermediate (Hurler-Scheie) and more attenuated (Scheie) phenotypes, with a normal life expectancy. The most severely affected patients are preferably treated with hematopoietic stem cell transplantation, which halts the neurocognitive decline. Patients with more attenuated phenotypes are treated with enzyme replacement therapy. There are several challenges to be met in the treatment of MPS I patients. First, to optimize outcome, early recognition of the disease and clinical phenotype is needed to guide decisions on therapeutic strategies. Second, there is thus far no effective treatment available for MPS I bone disease. The pathophysiological mechanisms behind bone disease are largely unknown, limiting the development of effective therapeutic strategies. This article is a state of the art that comprehensively discusses three of the most urgent open issues in MPS I: early diagnosis of MPS I patients, pathophysiology of MPS I bone disease, and emerging therapeutic strategies for MPS I bone disease.

Primary skeletal muscle myoblasts from chronic heart failure patients exhibit loss of anti-inflammatory and proliferative activity.

BACKGROUND: Peripheral skeletal muscle wasting is a common finding with adverse effects in chronic heart failure (HF). Whereas its clinical relevance is beyond doubt, the underlying pathophysiological mechanisms are not yet fully elucidated. We aimed to introduce and characterize the primary culture of skeletal muscle cells from individual HF patients as a supportive model to study this muscle loss. METHODS AND RESULTS: Primary myoblast and myotubes cultures were successfully propagated from the m. vastus lateralis of 6 HF patients with reduced ejection fraction (HFrEF; LVEF <45 %) and 6 age and gender-matched healthy donors. HFrEF cultures were not different from healthy donors in terms of morphology, such as myoblast size, shape and actin microfilament. Differentiation and fusion indexes were identical between groups. Myoblast proliferation in logarithmic growth phase, however, was attenuated in the HFrEF group (p = 0.032). In addition, HFrEF myoblasts are characterized by a reduced TNFR2 expression and IL-6 secretion (p = 0.017 and p = 0.016; respectively). CONCLUSION: Biopsy derived primary skeletal muscle myoblasts of HFrEF patients produce similar morphological and myogenic differentiation responses as myoblasts of healthy donors, though demonstrate loss of anti-inflammatory and proliferative activity.

A mutation in the human CBP4 ortholog UQCC3 impairs complex III assembly, activity and cytochrome b stability.

Complex III (cytochrome bc1) is a protein complex of the mitochondrial inner membrane that transfers electrons from ubiquinol to cytochrome c. Its assembly requires the coordinated expression of mitochondrial-encoded cytochrome b and nuclear-encoded subunits and assembly factors. Complex III deficiency is a severe multisystem disorder caused by mutations in subunit genes or assembly factors. Sequence-profile-based orthology predicts C11orf83, hereafter named UQCC3, to be the ortholog of the fungal complex III assembly factor CBP4. We describe a homozygous c.59T>A missense mutation in UQCC3 from a consanguineous patient diagnosed with isolated complex III deficiency, displaying lactic acidosis, hypoglycemia, hypotonia and delayed development without dysmorphic features. Patient fibroblasts have reduced complex III activity and lower levels of the holocomplex and its subunits than controls. They have no detectable UQCC3 protein and have lower levels of cytochrome b protein. Furthermore, in patient cells, cytochrome b is absent from a high-molecular-weight complex III. UQCC3 is reduced in cells depleted for the complex III assembly factors UQCC1 and UQCC2. Conversely, absence of UQCC3 in patient cells does not affect UQCC1 and UQCC2. This suggests that UQCC3 functions in the complex III assembly pathway downstream of UQCC1 and UQCC2 and is consistent with what is known about the function of Cbp4 and of the fungal orthologs of UQCC1 and UQCC2, Cbp3 and Cbp6. We conclude that UQCC3 functions in complex III assembly and that the c.59T>A mutation has a causal role in complex III deficiency.

Mitochondrial ATP synthase: architecture, function and pathology.

Human mitochondrial (mt) ATP synthase, or complex V consists of two functional domains: F(1), situated in the mitochondrial matrix, and F(o), located in the inner mitochondrial membrane. Complex V uses the energy created by the proton electrochemical gradient to phosphorylate ADP to ATP. This review covers the architecture, function and assembly of complex V. The role of complex V di-and oligomerization and its relation with mitochondrial morphology is discussed. Finally, pathology related to complex V deficiency and current therapeutic strategies are highlighted. Despite the huge progress in this research field over the past decades, questions remain to be answered regarding the structure of subunits, the function of the rotary nanomotor at a molecular level, and the human complex V assembly process. The elucidation of more nuclear genetic defects will guide physio(patho)logical studies, paving the way for future therapeutic interventions.

Restoration of complex V deficiency caused by a novel deletion in the human TMEM70 gene normalizes mitochondrial morphology.

We report a fragmented mitochondrial network and swollen and irregularly shaped mitochondria with partial to complete loss of the cristae in fibroblasts of a patient with a novel TMEM70 gene deletion, which could be completely restored by complementation of the TMEM70 genetic defect. Comparative genomics analysis predicted the topology of TMEM70 in the inner mitochondrial membrane, which could be confirmed by immunogold labeling experiments, and showed that the TMEM70 gene is not restricted to higher multi-cellular eukaryotes. This study demonstrates that the role of complex V in mitochondrial cristae morphology applies to human mitochondrial disease pathology.

High-throughput assay to measure oxygen consumption in digitonin-permeabilized cells of patients with mitochondrial disorders.

BACKGROUND: Muscle biopsy analysis is regarded as the gold standard in diagnostic workups of patients with suspected mitochondrial disorders. Analysis of cultured fibroblasts can provide important additional diagnostic information. The measurement of individual OXPHOS complexes does not always provide sufficient information about the functional state of the complete mitochondrial energy-generating system. Thus, we optimized a high-throughput fluorescence-based methodology for oxygen consumption analysis in patient-derived cells. METHODS: We analyzed mitochondrial respiration in digitonin-permeabilized cells in the presence of a substrate mix containing pyruvate and malate, using a phosphorescent probe, 96-well plates, and a fluorescence plate reader. RESULTS: In control fibroblasts, we observed clear stimulation by ADP of the pyruvate + malate-driven respiration. Known inhibitors of the OXPHOS system and the Krebs cycle significantly reduced respiration. In patient fibroblasts with different OXPHOS deficiencies, ADP-stimulated respiratory activity was decreased in comparison to control cells. In several patients with reduced ATP production rate in muscle tissue but with normal OXPHOS enzyme activities, the fibroblasts displayed reduced respiratory activity. Finally, we observed a clear difference between control and complex I-deficient transmitochondrial cybrid cells. CONCLUSIONS: These results confirm the validity of the assay as a high-throughput screening method for mitochondrial function in digitonin-permeabilized cells. The assay allows primary and secondary mitochondrial abnormalities in muscle to be differentiated, which is of great importance with respect to counseling, and also will facilitate the search for new genetic defects that lead to mitochondrial disease.

Biochemical and genetic analysis of 3-methylglutaconic aciduria type IV: a diagnostic strategy.

The heterogeneous group of 3-methylglutaconic aciduria type IV consists of patients with various organ involvement and mostly progressive neurological impairment in combination with 3-methylglutaconic aciduria and biochemical features of dysfunctional oxidative phosphorylation. Here we describe the clinical and biochemical phenotype in 18 children and define 4 clinical subgroups (encephalomyopathic, hepatocerebral, cardiomyopathic, myopathic). In the encephalomyopathic group with neurodegenerative symptoms and respiratory chain complex I deficiency, two of the children, presenting with mild Methylmalonic aciduria, Leigh-like encephalomyopathy, dystonia and deafness, harboured SUCLA2 mutations. In children with a hepatocerebral phenotype most patients presented with complex I deficiency and mtDNA-depletion, three of which carried POLG1-mutations. In the cardiomyopathic subgroup most patients had complex V deficiency and an overlapping phenotype with that previously described in isolated complex V deficiency, in three patients a TMEM70 mutation was confirmed. In one male with a pure myopathic form and severe combined respiratory chain disorder, based on the pathogenomic histology of central core disease, RYR1 mutations were detected. In our patient group the presence of the biochemical marker 3-methylglutaconic acid was indicative for nuclear coded respiratory chain disorders. By delineating patient-groups we elucidated the genetic defect in 10 out of 18 children. Depending on the clinical and biochemical phenotype we suggest POLG1, SUCLA2, TMEM70 and RYR1 sequence analysis and mtDNA-depletion studies in children with 3-methylglutaconic aciduria type IV.