Retrograde AAV selectively targets D1-MSNs and saves Parkinsonian symptoms with chemogenetic modulation. Credit: SIAT
Researchers from the Shenzhen Institute of Advanced Technology (SIAT) within the Chinese Academy of Sciences (CAS), in addition to their partners, have actually designed a targeted gene therapy technique to alleviate the primary motor signs of Parkinsons disease in both rodents and nonhuman primates.
The research study was just recently published in the journal Cell.
Parkinsons illness, characterized by the loss of midbrain dopaminergic nerve cells, is one of the most common neurodegenerative diseases in the senior population, affecting more than 6 million individuals worldwide.
Levodopa (L-Dopa)- based treatment, which helps to bring back the dopamine systems function, is the mainstay treatment for Parkinsons disease. Nearly all patients given long-term L-Dopa treatment suffer from motor complications (e.g., motor fluctuations and dyskinesia). The relief of signs after a single drug administration lasts longer than 24 hours compared to a typical 6-hour therapeutic window for L-Dopa. Motor complications such as dyskinesia shown after L-Dopa treatment were absent after using the gene therapy over a prolonged period (i.e., over 8 months).
Dopamine receptor D1-expressing and D2-expressing medium spiny nerve cells (D1-MSN and D2-MSN, respectively) constitute 90% of nerve cells in the striatum. Both D1-MSN and D2-MSN receive dopaminergic innervation from the substantia nigra pars compacta (SNc), yet play opposing roles in motion control.
D1-MSNs that predict to the globus pallidus internal sector (GPi) and substantia nigra pars reticulata (SNr) make up the direct path and promote motion. In contrast, D2-MSNs that project to the globus pallidus external segment (GPe) form the indirect path and mediate movement inhibition.
In Parkinsons illness, dopamine exhaustion causes hypoactivity of the direct pathway and hyperactivity of the indirect path, resulting in numerous motor signs.
Limitations of New approaches and existing treatments
Levodopa (L-Dopa)- based treatment, which assists to bring back the dopamine systems function, is the mainstay treatment for Parkinsons illness. Unfortunately, practically all patients provided long-term L-Dopa treatment experience motor complications (e.g., motor fluctuations and dyskinesia). Hence, accurate, efficient, and steady treatments are considerably needed.
Considering that the SNr receives dense forecast from the D1-MSNs and no forecast from the D2-MSNs, the researchers proposed that D1-MSNs might be selectively identified by injecting highly effective retrograde adeno-associated infection (AAV) into the SNr and then be specifically controlled by presenting neuronal activity-regulating elements in the retrograde AAV.
To achieve the above goals, they developed a novel AAV capsid, AAV8R12, for efficient retrograde labeling of the D1-MSN in the striatum as well a new promoter G88P2/3/7 with strong D1-MSN activity. With a chemogenetic effector rM3Ds to match systemic administration of the activation drug, this gene treatment strategy was able to particularly activate D1-MSN and thus drive the D1-MSN-mediated direct path.
Results and Potential of the New Strategy
Normal motor symptoms such as trembling, bradykinesia, and rigidity were significantly improved in primate designs with Parkinsons disease after applying the circuit-specific method targeting D1-MSNs. For instance, bradykinesia was significantly reduced, trembling was totally eliminated, and motor abilities were restored.
Unlike L-Dopa treatment which non-specifically triggers the dopamine system in both the brain and peripheral organs, this brand-new method exactly controls the D1-MSN-mediated direct pathway.
In addition to its healing effectiveness, this circuit-manipulating gene treatment has a quicker beginning and longer duration compared to L-Dopa treatment. The reduction of symptoms after a single drug administration lasts longer than 24 hours compared to a normal 6-hour healing window for L-Dopa. Motor complications such as dyskinesia revealed after L-Dopa treatment were absent after applying the gene therapy over a prolonged period (i.e., over 8 months).
Showing possible for treating Parkinsons illness, this circuit-manipulating gene treatment paves the method for future development of targeted, circuit-based healing methods for other brain conditions.
Reference: “Circuit-specific gene treatment reverses core signs in a primate Parkinsons disease design” by Yefei Chen, Zexuan Hong, Jingyi Wang, Kunlin Liu, Jing Liu, Jianbang Lin, Shijing Feng, Tianhui Zhang, Liang Shan, Taian Liu, Pinyue Guo, Yunping Lin, Tian Li, Qian Chen, Xiaodan Jiang, Anan Li, Xiang Li, Yuantao Li, Jonathan J. Wilde, Jin Bao, Ji Dai and Zhonghua Lu, 2 November 2023, Cell.DOI: 10.1016/ j.cell.2023.10.004.
