Juan Parga

• University of Santiago de Compostela

Parkinson’s disease is a neurodegenerative condition characterized by motor impairments caused by the selective loss of dopaminergic neurons in the substantia nigra. Levodopa is an effective and well-tolerated dopamine replacement agent. However, levodopa provides only symptomatic improvements, without affecting the underlying pathology, and is ass...

2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson’s disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transc...

A major limiting factor for cell therapy in Parkinson's disease is the poor survival and reinnervation capacity of grafted dopaminergic neurons, independently of the cell source. Mesenchymal stromal cells (MSCs) have high capability to regulate the local environment through the release of trophic, antiapoptotic and immunomodulatory factors. In this...

Adult neurogenesis is a dynamic and highly regulated process and different studies suggest that dopamine modulates ventricular-subventricular zone (V-SVZ) neurogenesis. However, the specific role of dopamine and the mechanisms/factors underlying its effects on physiological and pathological conditions such as Parkinson's disease (PD) are not fully...

The renin–angiotensin system (RAS), and particularly its angiotensin type-2 receptors (AT2), have been classically involved in processes of cell proliferation and maturation during development. However, the potential role of RAS in adult neurogenesis in the ventricular-subventricular zone (V-SVZ) and its aging-related alterations have not been inve...

Nuclear factor-E2-related factor 2 (NRF2) is a transcription factor that activates the antioxidant cellular defense in response to oxidative stress, leading to neuroprotective effects in Parkinson's disease (PD) models. We have previously shown that Angiotensin II (AngII) induces an increase in reactive oxygen species (ROS) via AngII receptor type...

This article describes the effect of the oxidative stress inducers Angiotensin II and 6-hydroxydopamine (6-OHDA) on different cell lines. The levels of expression Angiotensin type 1 and type 2 receptors in different dopaminergic cell lines are shown. The data indicate that treatment with Angiotensin II and 6-OHDA increases the production of reactiv...

In addition to the classical hormonal (tissue-to-tissue) renin-angiotensin system (RAS), there are a paracrine (cell-to-cell) and an intracrine (intracellular/nuclear) RAS. A local paracrine brain RAS has been associated with several brain disorders, including Parkinson’s disease (PD). Classically, angiotensin II (Ang II) is the main RAS effector p...

Mesenchymal stromal cells (MSCs) have been shown to have useful properties for cell therapy and have been proposed for treatment of neurodegenerative diseases, including Parkinson's disease. However, the mechanisms involved in recovering dopaminergic neurons are not clear. The present study aims to evaluate the pathways and molecules involved in th...

Significance: Cell-replacement therapy is one promising therapy for Parkinson's disease (PD). However, many questions must be addressed before widespread application. Rho kinase (ROCK) inhibitors have been used in a variety of applications associated with stem cell research and may be an excellent strategy for improving survival of grafted neurons...

Neuroactive! An enantioselective, catalytic synthesis strategy provides rapid access to natural-product-inspired classes of neuritogenic compounds. The goal is to find interesting chemical probes to shed light on neurodevelopmental processes and foster a better understanding of the complex biology and physiology of neuronal development and related...

Phenotypic drug discovery requires billions of cells for high-throughput screening (HTS) campaigns. Because up to several million different small molecules will be tested in a single HTS campaign, even small variability within the cell populations for screening could easily invalidate an entire campaign. Neurodegenerative assays are particularly ch...

Natural products endowed with neuromodulatory activity and their underlying structural scaffolds may inspire the synthesis of novel neurotrophic compound classes. The spirocyclic secoyohimbane alkaloid rhynchophylline is the major component of the extracts of Uncaria species used in Chinese traditional medicine for treatment of disorders of the cen...

smNPCs differentiate into oligodendrocytes after spontaneous differentiation. (A) After at least three weeks of spontaneous differentiation by withdrawal of CHIR and PMA, single O4 positive cells are interspersed in the neural clusters, as identified by TUBBIII positive neurons. (B) Following reseeding as single cells and recovery of one more week,...

Derivation of neural epithelial cells. (A) Immunostaining of EBs with the indicted markers on day 6 of differentiation after being plated for 8 hours. (B) GTG-banded metaphase spreads for 3 independent neural epithelial cell lines derived from either human ESCs or iPSCs as indicated, analyzed at passage 25 to 27 and showing apparently normal diploi...

Differentiation of neural epithelial cells into neural crest progenitors. (A) qRT-PCR of neural epithelial cells after treatment with CHIR or BMP4 for 6 days for the neural crest markers PAX7 and SOX9 and TFAP2A. (B) Immunostaining for TFAP2A after differentiation of neural epithelial cells with CHIR for 2 days followed by BMP4 for two days, indica...

smNPC-derived neurons acquire excitable properties of neuronal cells. (A–E) Amplitude and kinetic parameters (n = 7 cells) and an exemplary recording of minis (F) performed at holding potential −70 mV after two to three weeks of maturation. (TIF)

Human iPSC-derived smNPCs. 2 independent smNPC lines were derived from iPSCs. The results of all experiments with hiPSC-derived smNPCs were directly comparable to those with hESC-derived smNPCs. (A) Immunostaining results for the indicated neural progenitor markers. Immunostaining of PNS neurons (B), mDANs (C), and MNs (D) differentiated from the i...

Clonal differentiation into CNS and PNS lineages. (A) Phase-contrast images of 3 independent single cell–derived neural epithelial cell colonies that were picked and expanded. (B) Immunostaining of the resulting clonal neural epithelial cell lines for the indicated neural progenitor markers. (C) Immunostaining for mDANs (TH/FOXA2), MNs (ISLET1/TUBI...

LRRK2 G2019S increases sensitivity of dopaminergic neurons derived from smNPCs to stress compared with controls. smNPCs were derived from two patient-specific LRRK2 mutant iPSCs, alongside with two age- and sex-matched controls. smNPCs were differentiated into mDANs, replated as single cells and incubated with N2 medium only, or supplemented with 5...

Primers used for qRT-PCR used in this study. (DOCX)

Gene expression by neural epithelial cells. (A) Expression levels for the indicated genes derived from microarray analysis of 2 neural epithelial cell lines and their parental human pluripotent cell lines. Neural epithelial cells consistently expressed neural progenitor and rosette markers, but not markers of pluripotency or mesendodermal different...

Neural epithelial cells are capable of forming neural rosettes. (A) Phase-contrast image of smNPCs before and after treatment with FGF2 for 2 days. (B) Immunostaining of neural epithelial cells before and after treatment with FGF2 for NESTIN, N-CADHERIN, and ZO-1. Arrowheads indicate N-CADHERIN and ZO-1 expression in the center of neural rosette-li...

In vivo differentiation potential and long-term survival of transplanted smNPCs. (A) Already after two weaks of maturation in vivo, smNPCs form mature, postmitoctic neurons, as shown by NeuN and human – specific NCAM staining. (B–E) Eight weeks post transplantation, smNPCs have formed and survived as neurons and astrocytes, as shown by staining for...

Neural epithelial cells express markers of a moderately dorsal, hindbrain character. Microarray data of the indicated neural epithelial cell lines for markers of dorsoventral (A) and rostrocaudal (B) patterning. A schematic representation of the expression patterns of these markers in vivo in the developing neural tube is shown to the right. The bl...

smNPC-derived mDANs are specifically susceptible to oxidative stress. (A) Overview image of a stressed dopaminergic neuron culture after differentiation from smNPCs stressed with 6 OH-Dopa for two days before fixation. Cultures were stained with the indicated markers. Note that most of the cells positive for cleaved CASPASE3 (CASP3) as an indicator...

Stem cells, through their ability to both self-renew and differentiate, can produce a virtually limitless supply of specialized cells that behave comparably to primary cells. We took advantage of this property to develop an assay for small-molecule-based neuroprotection using stem-cell-derived motor neurons and astrocytes, together with activated m...

Recent studies have shown that renin-angiotensin system overactivation is involved in the aging process in several tissues as well as in longevity and aging-related degenerative diseases by increasing oxidative damage and inflammation. We have recently shown that angiotensin II enhances dopaminergic degeneration by increasing levels of reactive oxy...

Reactive oxygen species signaling has been suggested to regulate stem cell development. In the present study, we treated neurospheres of rat mesencephalic precursors with inhibitors of the NADPH oxidase complex and mitochondrial ATP-sensitive potassium (mitoKATP) channel blockers during the proliferation and/or the differentiation periods to study...

The neurotoxin 6-hydroxydopamine is commonly used in models of Parkinson's disease, and a potential factor in the pathogenesis of the disease. However, the mechanisms responsible for 6-hydroxydopamine-induced dopaminergic degeneration have not been totally clarified. Reactive oxygen species (ROS) derived from 6-OHDA uptake and intraneuronal autooxi...

Angiotensin II (AII) plays a major role in the progression of inflammation and NADPH-derived oxidative stress (OS) in several tissues. The brain possesses a local angiotensin system, and OS and inflammation are key factors in the progression of Parkinson's disease. In rat mesencephalic cultures, AII increased 6-OHDA-induced dopaminergic (DA) cell d...

Production of dopaminergic neurons from stem/precursor cells for transplantation in Parkinson's disease has become a major focus of research. However, the inductive signals mediating this process have not been clarified. Reported data on the effects of Sonic hedgehog on differentiation of dopaminergic and serotonergic neurons from cultures of neura...

Cell death induced by 6-hydroxydopamine (6-OHDA) is thought to be caused by reactive oxygen species (ROS) derived from 6-OHDA autooxidation and by a possible direct effect of 6-OHDA on the mitochondrial respiratory chain. However, the process has not been totally clarified. In rat primary mesencephalic cultures, we observed a significant increase i...

Neurotransmitters have been shown to control CNS neurogenesis, and GABA-mediated signaling is thought to be involved in the regulation of nearly all key developmental stages. Generation of dopaminergic (DA) neurons from stem/precursor cells for cell therapy in Parkinson's disease has become a major focus of research. However, the possible effects o...

Inductive signals mediating the differentiation of neural precursors into serotonergic (5-HT) or dopaminergic neurons have not been clarified. We have recently shown that in cell aggregates obtained from rat mesencephalic precursors, reduction of serotonin levels induces a marked increase in generation of dopaminergic neurons. In the present study...

The search for alternative sources of dopaminergic cells, other than primary fetal tissue for transplantation in Parkinson's disease has become a major focus of research. Different methodological approaches have led to generation in vitro of cells expressing DA-cell markers, although these cells are frequently unable to survive for a long time in v...

The level of heme oxygenase-1 (HO-1) in the normal striatum is below the limit of immunodetection. However, HO-1 is overexpressed in both neural and non-neural cells in response to a wide range of lesions. We induced different types of lesions affecting the striatal cells or the main striatal afferent systems in rats to investigate if overexpressio...

In addition to the well-known actions of the humoral renin-angiotensin system, all components of this system are present in many tissues, including the brain, and may play a major role in brain development and differentiation. We investigated the possible effects of angiotensin II on the generation of dopaminergic phenotype neurons from proliferati...