Abstract Impulsive-compulsive disorders (ICDs), including pathological gambling, hypersexuality, and compulsive buying, are frequently precipitated by dopamine D2/3 receptor agonists such as pramipexole (PPX), yet the molecular mechanisms that confer individual vulnerability remain poorly understood. Impulsive choice, a core dimension of ICDs, is modulated by dopaminergic signaling within corticostriatal circuits, but the microRNAs (miRs) that potentially translate this signaling into persistent behavioral change have not been identified. Here, we combined a delay discounting task (DDT) with high-throughput miR sequencing in the dorsal striatum and nucleus accumbens (NAcc) of rats stratified by baseline impulsivity and subchronic PPX treatment. PPX increased impulsive choice selectively in low- and mid-impulsive rats, whereas high-impulsive rats remained unaffected, consistent with a ceiling effect. Among the differentially expressed miRs, miR-10a-5p emerged as the strongest candidate: it was constitutively elevated in high-impulsive rats and upregulated by PPX in low- and mid-impulsive animals in both regions, thereby paralleling the trait-dependent behavioral effect of the drug. In vivo viral-mediated overexpression of miR-10a-5p confirmed its predicted downregulation of the PI3K–AKT–mTOR and BDNF pathways in the striatum, and, critically, overexpression restricted to the NAcc, but not the dorsal striatum, was sufficient to increase impulsive choice, recapitulating the pro-impulsive effect of PPX. These findings identify miR-10a-5p as a critical molecular regulator of impulsivity through its activity in the NAcc, providing a mechanistic link between dopaminergic perturbation, trait vulnerability, and ICDs, and opening new avenues for the development of miR-directed therapeutic strategies for these disorders.

Background & AimA breadth of preclinical studies (Doi et al, 2020; Piao et al, 2021; Hiller et al, 2022, Kirkeby et al, 2023) is now backing the rationale of pluripotent-stem cell (PSC)-derived cell replacement therapies to restore motor function in Parkinsonian patients. The target for replacement is the major dysfunctional cell population in the disease: ventral mesencephalic A9 dopaminergic neurons, which are particularly vulnerable to the in vitro manipulations required for intracerebral administration (Marchionini et al., 2003). Optimizing for survival and functionality post-transplantation is thus a significant pharmaceutical hurdle for manufacturing and delivering dopaminergic neuron-containing cell therapies. With the aim to ensure accurate dosing and enhance functional reproducibility, we report here a change in graft format, i.e. moving away from cell suspensions to 3D neural microtissues that are resistant to the stress of transplantation.Methods, Results & ConclusionUsing TreeFrog Therapeutics’ proprietary cell encapsulation C-stem technology and standard bioreactors, we demonstrate a scalable process to generate off-the-shelf cryopreserved iPSC-derived 3D neural microtissues containing a mixture of ventral mesencephalic dopaminergic neurons and dopaminergic progenitors. We use orthogonal methods including flow cytometry, immunofluorescence labelling, RTqPCR and bulkRNAseq for characterization. Upon administration, the neural microtissues innervate the lesioned striatum of hemiparkinsonian rodents with TH+ dopaminergic projections and lead to motor recovery by 16 weeks (MFD and high dose) and 20 weeks (low dose) respectively. This demonstrates proof-of-concept efficacy of the dopaminergic neuron-containing neural microtissue product and supports the intention to pursue preclinical studies to assess its safety and efficacy as a cell therapy for Parkinson's disease.

Impulse control disorders (ICDs), a wide spectrum of maladaptive behaviors which includes pathological gambling, hypersexuality and compulsive buying, have been recently suggested to be triggered or aggravated by treatments with dopamine D2/3 receptor agonists, such as pramipexole (PPX). Despite evidence showing that impulsivity is associated with functional alterations in corticostriatal networks, the neural basis of the exacerbation of impulsivity by PPX has not been elucidated. Here we used a hotspot analysis to assess the functional recruitment of several corticostriatal structures by PPX in male rats identified as highly (HI), moderately impulsive (MI) or with low levels of impulsivity (LI) in the 5-choice serial reaction time task (5-CSRTT). PPX dramatically reduced impulsivity in HI rats. Assessment of the expression pattern of the two immediate early genes C-fos and Zif268 by in situ hybridization subsequently revealed that PPX resulted in a decrease in Zif268 mRNA levels in different striatal regions of both LI and HI rats accompanied by a high impulsivity specific reduction of Zif268 mRNA levels in prelimbic and cingulate cortices. PPX also decreased C-fos mRNA levels in all striatal regions of LI rats, but only in the dorsolateral striatum and nucleus accumbens core (NAc Core) of HI rats. Structural equation modeling further suggested that the anti-impulsive effect of PPX was mainly attributable to the specific downregulation of Zif268 mRNA in the NAc Core. Altogether, our results show that PPX restores impulse control in highly impulsive rats by modulation of limbic frontostriatal circuits.

The neurobiological mechanisms underlying compulsive alcohol use, a cardinal feature of alcohol use disorder, remain elusive. The key modulator of motivational processes, dopamine (DA), is suspected to play an important role in this pathology, but its exact role remains to be determined. Here, we found that rats expressing compulsive-like alcohol use, operationalized as punishment-resistant self-administration, showed a decrease in DA levels restricted to the dorsolateral territories of the striatum, the main output structure of the nigrostriatal DA pathway. We then causally demonstrated that chemogenetic-induced selective hypodopaminergia of this pathway resulted in compulsive-like alcohol self-administration in otherwise resilient rats, accompanied by the emergence of alcohol withdrawal-like motivational impairments (i.e., impaired motivation for a natural reinforcer). Finally, the use of the monoamine stabilizer OSU6162, previously reported to correct hypodopaminergic states, transiently decreased compulsive-like alcohol self-administration in vulnerable rats. These results suggest a potential critical role of tonic nigrostriatal hypodopaminergic states in alcohol addiction and provide new insights into our understanding of the neurobiological mechanisms underlying compulsive alcohol use.

BackgroundCare management of Parkinson's disease (PD) patients currently remains symptomatic, mainly because diagnosis relying on the expression of the cardinal motor symptoms is made too late. Earlier detection of PD therefore represents a key step for developing therapies able to delay or slow down its progression.MethodsWe investigated metabolic markers in 3 different animal models of PD, mimicking different phases of the disease assessed by behavioral and histological evaluation, and in 3 cohorts of de novo PD patients and matched controls (n = 129). Serum and brain tissue samples were analyzed by nuclear magnetic resonance spectroscopy and data submitted to advanced multivariate statistics.ResultsOur translational strategy reveals common metabolic dysregulations in serum of the different animal models and PD patients. Some of them were mirrored in the tissue samples, possibly reflecting pathophysiological mechanisms associated with PD development. Interestingly, some metabolic dysregulations appeared before motor symptom emergence and could represent early biomarkers of PD. Finally, we built a composite biomarker with a combination of 6 metabolites. This biomarker discriminated animals mimicking PD from controls, even from the first, nonmotor signs and, very interestingly, also discriminated PD patients from healthy subjects.ConclusionFrom our translational study, which included 3 animal models and 3 de novo PD patient cohorts, we propose a promising biomarker exhibiting a high accuracy for de novo PD diagnosis that may possibly predict early PD development, before motor symptoms appear.FundingFrench National Research Agency (ANR), DOPALCOMP, Institut National de la Santé et de la Recherche Médicale, Université Grenoble Alpes, Association France Parkinson.

Background Care management of Parkinson’s disease (PD) patients currently remains symptomatic, especially because diagnosis relying on the expression of the cardinal motor symptoms is made too late. Detecting PD earlier therefore represents a key step for developing therapies able to delay or slow down its progression. Methods We investigated metabolic markers in three different animal models of PD, mimicking different phases of the disease assessed by behavioral and histological evaluation, and in 2 cohorts of de novo PD patients (n = 95). Serum and brain tissue samples were analyzed by nuclear magnetic resonance spectroscopy and data submitted to advanced multivariate statistics. Results Our translational strategy reveals common metabolic dysregulations in serum of the different animal models and PD patients. Some of them were mirrored in the tissue samples, possibly reflecting pathophysiological mechanisms associated with PD development. Interestingly, some metabolic dysregulations appeared before motor symptom emergence, and could represent early biomarkers of PD. Finally, we built a composite biomarker with a combination of 6 metabolites. This biomarker discriminated animals mimicking PD from controls, even from the first, non-motor signs and very interestingly, also discriminated PD patients from healthy subjects. Conclusion From our translational study which included three animal models and two PD patient cohorts, we propose a promising composite biomarker exhibiting a high level of predictivity for PD diagnosis in its early phase, before motor symptoms appearance. Fundings ANR, DOPALCOMP, Institut National de la Santé et de la Recherche Médicale, Grenoble Alpes University.

BackgroundCare management of Parkinson's disease (PD) patients currently remains symptomatic, mainly because diagnosis relying on the expression of the cardinal motor symptoms is made too late. Earlier detection of PD therefore represents a key step for developing therapies able to delay or slow down its progression.MethodsWe investigated metabolic markers in 3 different animal models of PD, mimicking different phases of the disease assessed by behavioral and histological evaluation, and in 3 cohorts of de novo PD patients and matched controls (n = 129). Serum and brain tissue samples were analyzed by nuclear magnetic resonance spectroscopy and data submitted to advanced multivariate statistics.ResultsOur translational strategy reveals common metabolic dysregulations in serum of the different animal models and PD patients. Some of them were mirrored in the tissue samples, possibly reflecting pathophysiological mechanisms associated with PD development. Interestingly, some metabolic dysregulations appeared before motor symptom emergence and could represent early biomarkers of PD. Finally, we built a composite biomarker with a combination of 6 metabolites. This biomarker discriminated animals mimicking PD from controls, even from the first, nonmotor signs and, very interestingly, also discriminated PD patients from healthy subjects.ConclusionFrom our translational study, which included 3 animal models and 3 de novo PD patient cohorts, we propose a promising biomarker exhibiting a high accuracy for de novo PD diagnosis that may possibly predict early PD development, before motor symptoms appear.FundingFrench National Research Agency (ANR), DOPALCOMP, Institut National de la Santé et de la Recherche Médicale, Université Grenoble Alpes, Association France Parkinson.

microRNAs are small non-coding RNAs gaining interest for their potential roles as reliable biomarkers for the diagnosis and therapeutics of numerous pathologies, ranging from cancer to neurodegenerative or psychiatric disorders. Indeed, microRNAs are present in various accessible biofluids, including peripheral blood, and specific dysregulation of their expression may be associated with these different pathological conditions. microRNAs can be isolated from plasma or serum for sequencing with commercial kits. However, these two biofluids might exhibit some differences in their microRNA contents, due notably to the coagulation process occurring during serum collection. It remains unclear from previous studies and commercial recommendations which blood fraction is preferable. Because of the small amount of circulating microRNAs in a given blood volume, this question appears crucial for qualitative and quantitative optimization of microRNA profiling, especially in animal models used for investigating the pathophysiological relevancy of this approach. We therefore evaluated the efficiency of RNA isolation and microRNA levels from plasma and sera isolated from rats and humans, with a widely used extraction kit (QIAGEN miRNeasy), and assessed microRNA quality and quantity with high-throughput sequencing. Fewer reads with length corresponding to non-miRNAs sequences were observed in plasma than in serum, both from rats and humans. Moreover, rat plasma produced twice as many aligned reads compared to sera, as well as more aligned reads corresponding to microRNAs (84.6% against 38.7%), differences that were not find in human samples. Our results, therefore, clearly indicate that plasma should be preferred for miRNA investigations, particularly for translational studies.