IGF-1 in Friedreich's Ataxia - proof-of-concept trial

Therapeutic Biomarkers in Friedreich's Ataxia: a Systematic Review and Meta-analysis

Although a large array of biomarkers have been investigated in Friedreich's ataxia (FRDA) trials, the optimal biomarker for assessing disease progression or therapeutic benefit has yet to be identified. We searched PubMed, MEDLINE, and EMBASE databases up to June 2023 for any original study (with ≥ 5 participants and ≥ 2 months' follow-up) reporting the effect of therapeutic interventions on any clinical, cardiac, biochemical, patient-reported outcome measures, imaging, or neurophysiologic biomarker. We also explored the biomarkers' ability to detect subtle disease progression in untreated patients. The pooled standardized mean difference (SMD) was calculated using a random-effects model. The study's protocol was registered in PROSPERO (CRD42022319196). In total, 43 studies with 1409 FRDA patients were included in the qualitative synthesis. A statistically significant improvement was observed in Friedreich Ataxia Rating Scale scores [combining Friedreich Ataxia Rating Scale (FARS) and modified FARS (mFARS): SMD =  - 0.32 (- 0.62 to - 0.02)] following drugs that augment mitochondrial function in a sensitivity analysis. Left ventricular mass index (LVMI) was improved significantly [SMD =  - 0.34 (- 0.5 to - 0.18)] after 28.5 months of treatment with drugs that augment mitochondrial function. However, LVMI remained stable [SMD = 0.05 (- 0.3 to 0.41)] in untreated patients after 6-month follow-up. None of the remaining biomarkers changed significantly following any treatment intervention nor during the natural disease progression. Nevertheless, clinical implications of these results should be interpreted with caution because of low to very low quality of evidence. Further randomized controlled trials of at least 24 months' duration using a biomarker toolbox rather than a single biomarker are warranted.

The neurobiology of insulin-like growth factor I: From neuroprotection to modulation of brain states

After decades of research in the neurobiology of IGF-I, its role as a prototypical neurotrophic factor is undisputed. However, many of its actions in the adult brain indicate that this growth factor is not only involved in brain development or in the response to injury. Following a three-layer assessment of its role in the central nervous system, we consider that at the cellular level, IGF-I is indeed a bona fide neurotrophic factor, modulating along ontogeny the generation and function of all the major types of brain cells, contributing to sculpt brain architecture and adaptive responses to damage. At the circuit level, IGF-I modulates neuronal excitability and synaptic plasticity at multiple sites, whereas at the system level, IGF-I intervenes in energy allocation, proteostasis, circadian cycles, mood, and cognition. Local and peripheral sources of brain IGF-I input contribute to a spatially restricted, compartmentalized, and timed modulation of brain activity. To better define these variety of actions, we consider IGF-I a modulator of brain states. This definition aims to reconcile all aspects of IGF-I neurobiology, and may provide a new conceptual framework in the design of future research on the actions of this multitasking neuromodulator in the brain.

Frataxin Deficit Leads to Reduced Dynamics of Growth Cones in Dorsal Root Ganglia Neurons of Friedreich’s Ataxia YG8sR Model: A Multilinear Algebra Approach

Computational techniques for analyzing biological images offer a great potential to enhance our knowledge of the biological processes underlying disorders of the nervous system. Friedreich’s Ataxia (FRDA) is a rare progressive neurodegenerative inherited disorder caused by the low expression of frataxin, which is a small mitochondrial protein. In FRDA cells, the lack of frataxin promotes primarily mitochondrial dysfunction, an alteration of calcium (Ca²⁺) homeostasis and the destabilization of the actin cytoskeleton in the neurites and growth cones of sensory neurons. In this paper, a computational multilinear algebra approach was used to analyze the dynamics of the growth cone and its function in control and FRDA neurons. Computational approach, which includes principal component analysis and a multilinear algebra method, is used to quantify the dynamics of the growth cone (GC) morphology of sensory neurons from the dorsal root ganglia (DRG) of the YG8sR humanized murine model for FRDA. It was confirmed that the dynamics and patterns of turning were aberrant in the FRDA growth cones. In addition, our data suggest that other cellular processes dependent on functional GCs such as axonal regeneration might also be affected. Semiautomated computational approaches are presented to quantify differences in GC behaviors in neurodegenerative disease. In summary, the deficiency of frataxin has an adverse effect on the formation and, most importantly, the growth cones’ function in adult DRG neurons. As a result, frataxin deficient DRG neurons might lose the intrinsic capability to grow and regenerate axons properly due to the dysfunctional GCs they build.

Research Progress on Neuroprotection of Insulin-like Growth Factor-1 towards Glutamate-Induced Neurotoxicity

Insulin-like growth factor-1 (IGF-1) and its binding proteins and receptors are widely expressed in the central nervous system (CNS), proposing IGF-1-induced neurotrophic actions in normal growth, development, and maintenance. However, while there is convincing evidence that the IGF-1 system has specific endocrine roles in the CNS, the concept is emerging that IGF-I might be also important in disorders such as ischemic stroke, brain trauma, Alzheimer’s disease, epilepsy, etc., by inducing neuroprotective effects towards glutamate-mediated excitotoxic signaling pathways. Research in rodent models has demonstrated rescue of pathophysiological and behavioral abnormalities when IGF-1 was administered by different routes, and several clinical studies have shown safety and promise of efficacy in neurological disorders of the CNS. Focusing on the relationship between IGF-1-induced neuroprotection and glutamate-induced excitatory neurotoxicity, this review addresses the research progress in the field, intending to provide a rationale for using IGF-I clinically to confer neuroprotective therapy towards neurological diseases with glutamate excitotoxicity as a common pathological pathway.

Mesenchymal Stem Cell-Derived Factors Restore Function to Human Frataxin-Deficient Cells

Friedreich's ataxia is an inherited neurological disorder characterised by mitochondrial dysfunction and increased susceptibility to oxidative stress. At present, no therapy has been shown to reduce disease progression. Strategies being trialled to treat Friedreich's ataxia include drugs that improve mitochondrial function and reduce oxidative injury. In addition, stem cells have been investigated as a potential therapeutic approach. We have used siRNA-induced knockdown of frataxin in SH-SY5Y cells as an in vitro cellular model for Friedreich's ataxia. Knockdown of frataxin protein expression to levels detected in patients with the disorder was achieved, leading to decreased cellular viability, increased susceptibility to hydrogen peroxide-induced oxidative stress, dysregulation of key anti-oxidant molecules and deficiencies in both cell proliferation and differentiation. Bone marrow stem cells are being investigated extensively as potential treatments for a wide range of neurological disorders, including Friedreich's ataxia. The potential neuroprotective effects of bone marrow-derived mesenchymal stem cells were therefore studied using our frataxin-deficient cell model. Soluble factors secreted by mesenchymal stem cells protected against cellular changes induced by frataxin deficiency, leading to restoration in frataxin levels and anti-oxidant defences, improved survival against oxidative stress and stimulated both cell proliferation and differentiation down the Schwann cell lineage. The demonstration that mesenchymal stem cell-derived factors can restore cellular homeostasis and function to frataxin-deficient cells further suggests that they may have potential therapeutic benefits for patients with Friedreich's ataxia.

A role for astrocytes in cerebellar deficits in frataxin deficiency: Protection by insulin-like growth factor I

Inherited neurodegenerative diseases such as Friedreich's ataxia (FRDA), produced by deficiency of the mitochondrial chaperone frataxin (Fxn), shows specific neurological deficits involving different subset of neurons even though deficiency of Fxn is ubiquitous. Because astrocytes are involved in neurodegeneration, we analyzed whether they are also affected by frataxin deficiency and contribute to the disease. We also tested whether insulin-like growth factor I (IGF-I), that has proven effective in increasing frataxin levels both in neurons and in astrocytes, also exerts in vivo protective actions. Using the GFAP promoter expressed by multipotential stem cells during development and mostly by astrocytes in the adult, we ablated Fxn in a time-dependent manner in mice (FGKO mice) and found severe ataxia and early death when Fxn was eliminated during development, but not when deleted in the adult. Analysis of underlying mechanisms revealed that Fxn deficiency elicited growth and survival impairments in developing cerebellar astrocytes, whereas forebrain astrocytes grew normally. A similar time-dependent effect of frataxin deficiency in astrocytes was observed in a fly model. In addition, treatment of FGKO mice with IGF-I improved their motor performance, reduced cerebellar atrophy, and increased survival. These observations indicate that a greater vulnerability of developing cerebellar astrocytes to Fxn deficiency may contribute to cerebellar deficits in this inherited disease. Our data also confirm a therapeutic benefit of IGF-I in early FRDA deficiency.

Emerging therapies in Friedreich's ataxia

Friedreich's ataxia (FRDA) is an inherited, progressive neurodegenerative disease that typically affects teenagers and young adults. Therapeutic strategies and disease insight have expanded rapidly over recent years, leading to hope for the FRDA population. There is currently no US FDA-approved treatment for FRDA, but advances in research of its pathogenesis have led to clinical trials of potential treatments. This article reviews emerging therapies and discusses future perspectives, including the need for more precise measures for detecting changes in neurologic symptoms as well as a disease-modifying agent.

Long-term treatment with thiamine as possible medical therapy for Friedreich ataxia

Thiamine (vitamin B1) is a cofactor of fundamental enzymes of cell energetic metabolism; its deficiency causes disorders affecting both the peripheral and central nervous system. Previous studies reported low thiamine levels in cerebrospinal fluid and pyruvate dehydrogenase dysfunction in Friedreich ataxia (FRDA). We investigated the effect of long-term treatment with thiamine in FRDA, evaluating changes in neurological symptoms, echocardiographic parameters, and plasma FXN mRNA levels. Thirty-four consecutive FRDA patients have been continuously treated with intramuscular thiamine 100 mg twice a week and have been assessed with the Scale for the Assessment and Rating of Ataxia (SARA) at baseline, after 1 month, and then every 3 months during treatment. Thiamine administration ranged from 80 to 930 days and was effective in improving total SARA scores from 26.6 ± 7.7 to 21.5 ± 6.2 (p < 0.02). Moreover, deep tendon reflexes reappeared in 57 % of patients with areflexia at baseline, and swallowing improved in 63 % of dysphagic patients. Clinical improvement was stable in all patients, who did not show worsening even after 2 years of treatment. In a subgroup of 13 patients who performed echocardiogram before and during treatment, interventricular septum thickness reduced significantly (p < 0.02). Frataxin mRNA blood levels were modestly increased in one-half of treated patients. We suppose that a focal thiamine deficiency may contribute to a selective neuronal damage in the areas involved in FRDA. Further studies are mandatory to evaluate thiamine role on FXN regulation, to exclude placebo effect, to verify our clinical results, and to confirm restorative and neuroprotective action of thiamine in FRDA.

Gene Transfer of Brain-derived Neurotrophic Factor (BDNF) Prevents Neurodegeneration Triggered by FXN Deficiency

Friedreich's ataxia is a predominantly neurodegenerative disease caused by recessive mutations that produce a deficiency of frataxin (FXN). Here, we have used a herpesviral amplicon vector carrying a gene encoding for brain-derived neurotrophic factor (BDNF) to drive its overexpression in neuronal cells and test for its effect on FXN-deficient neurons both in culture and in the mouse cerebellum in vivo. Gene transfer of BDNF to primary cultures of mouse neurons prevents the apoptosis which is triggered by the knockdown of FXN gene expression. This neuroprotective effect of BDNF is also observed in vivo in a viral vector-based knockdown mouse cerebellar model. The injection of a lentiviral vector carrying a minigene encoding for a FXN-specific short hairpin ribonucleic acid (shRNA) into the mouse cerebellar cortex triggers a FXN deficit which is accompanied by significant apoptosis of granule neurons as well as loss of calbindin in Purkinje cells. These pathological changes are accompanied by a loss of motor coordination of mice as assayed by the rota-rod test. Coinjection of a herpesviral vector encoding for BDNF efficiently prevents both the development of cerebellar neuropathology and the ataxic phenotype. These data demonstrate the potential therapeutic usefulness of neurotrophins like BDNF to protect FXN-deficient neurons from degeneration.

IFN-γ for Friedreich ataxia: present evidence

IFN-γ-1b is currently US FDA approved as an orphan drug for the treatment of chronic granulomatous disease and severe malignant osteopetrosis. It is administered via subcutaneous injection and is a potential therapy for Friedreich ataxia (FRDA), a rare degenerative neurological condition. Ongoing Phase II and III trials in both adults and children with FRDA were preceded by a small Phase I, open-label trial in children that showed that IFN-γ-1b was reasonably well-tolerated and improved overall neurological function as measured by the Friedreich Ataxia Rating Scale after 12 weeks of treatment, though the primary outcome measure of frataxin level showed no improvement. Although there is an established dose of IFN-γ-1b prescribed for the current indications, the efficacy and tolerability of these dose levels in the FRDA population remains the subject of ongoing investigation.