Biology subjects

Santa-Maria, I.

Publications and source records attributed to Santa-Maria, I..

6 recordsLinked to original sources

bioRxiv2026

Human SHED-derived extracellular cues activate a specialized neuroprotective and regenerative program in developing retinal ganglion cells

Axonal degeneration and insufficient neuronal survival remain major barriers to central nervous system repair. Stem cells from human exfoliated deciduous teeth (SHED) represent an accessible, developmentally immature, neural crest-derived mesenchymal stem cell population with potential relevance for neuroregenerative medicine. Here, we show that SHED display enhanced proliferative stability, preserved mesenchymal identity, and more sustained expansion capacity than adult dental pulp stem cells, supporting their suitability for scalable regenerative applications. Using embryonic chick retinal explants at neurogenic and post-neurogenic stages, we demonstrate that SHED robustly promote retinal ganglion cell axonogenesis, axonal regeneration, and neuronal survival. At embryonic day 5, SHED enhanced axonal outgrowth in both newly generated EdU/TUJ1 neurons and pre-existing EdU-/TUJ1 retinal ganglion cells. At embryonic day 13, when retinal neurons are post-mitotic and intrinsically less regenerative, SHED still significantly increased regenerative axonal extension and reduced developmental cell death. To investigate the molecular mechanisms underlying the neuroprotective and axogenic effects of SHED, proteomic profiling of SHED-retina co-culture secretomes was performed, revealing a highly enriched extracellular environment containing matrix-associated and neurodevelopmental proteins, including thrombospondin-1 (THBS1), galectin1 and 3, and multiple proteins associated with IGF2 pathway. Proteomic analysis of the SHED secretome, together with prior evidence implicating thrombospondin signaling in neuronal development and synaptogenesis, identified THBS1 as a strong candidate mediator of SHED-induced effects in chick retinal co-culture systems. Neutralization of THBS1, particularly in combination with gabapentin-mediated blockade of 2{delta}-1-dependent thrombospondin signaling, markedly reduced SHED-induced axonal growth and induced neuritic swellings consistent with impaired axonal integrity. In contrast, inhibition of THBS1 signaling did not significantly abolish the neuroprotective effect of SHED on neuronal survival, suggesting that distinct paracrine mechanisms independently regulate axonal regeneration and cell survival. Together, these findings demonstrate that SHED-derived combined secreted factors promote neuronal survival and axonal regeneration through partially divergent extracellular matrix-associated developmental pathways, positioning SHED and their secretome as promising candidates for cell-based and cell-free neuroregenerative strategies.

cell biology↗

bioRxiv2022

Neurogenic induction by Ngfr reduces reactive astrocytic Lcn2/Slc22a17 signalling, amyloid deposition and Tau phosphorylation

Neurogenesis relates to the brain resilience and is reduced in Alzheimers disease (AD). Restoring healthy levels of neurogenesis could have beneficial effects for coping with neurodegeneration. However, molecular mechanisms that could enhance neurogenesis from astroglial progenitors in AD pathology are largely unknown. We used lentiviruses to express Ngfr in the hippocampus of the APP/PS1dE9 mouse model of AD, histologically analyzed the changes in proliferation of neural stem cells and neurogenesis; performed single-cell transcriptomics, spatial proteomics, and functional knockdown studies. We found that expression of Ngfr, a neurogenic determinant in pathology-induced neuroregeneration in zebrafish, stimulated proliferative and neurogenic outcome in the APP/PS1dE9 AD mouse model. Ngfr suppressed reactive astrocyte marker Lipocalin-2 (Lcn2) in astroglia. Blockage of Lcn2 receptor, Slc22a17, recapitulated the neurogenic effects of NGFR, and long-term Ngfr expression reduced amyloid plaques and Tau phosphorylation. Furthermore, immunostaining on postmortem human hippocampi with AD or primary age-related Tauopathy and 3D human astroglial cultures showed that elevated LCN2 levels correlate with gliosis. By comparing transcriptional changes in mouse hippocampus, zebrafish brain, and human AD brains in terms of cell intrinsic differential gene expression analyses as well as weighted gene co-expression network analysis, we observed common potential downstream effectors of NGFR signaling, C4B and PFKP, that are relevant to AD. Our study links the regulatory role of an autocrine molecular mechanism in astroglia to the neurogenic ability and modulatory effects on amyloid and tau phosphorylation, opening new research avenues and suggesting that neurogenesis-oriented therapeutic approaches could be a potential clinical intervention for AD.

neuroscience↗

bioRxiv2021

Alzheimer's disease-associated P460L mutation in ephrin receptor type A1 (EphA1) leads to dysregulated Rho-GTPase signaling

Recently, late onset AD (LOAD) genome-wide association studies identified EphA1, a member of receptor tyrosine kinase family (RTK) as a disease associated loci. In the follow-up study where 3 independent LOAD cohorts were performed, a P460L coding mutation in EphA1 loci showed a significant association with LOAD. However, the role of EphA1 and P460L mutant EphA1 in AD is not fully understood. We have characterized this mutation biophysically and biochemically. Our structural in silico model and in vitro biochemical analysis demonstrate that EphA1-P460L mutation makes the receptor constitutively active suggesting a gain-of-toxic function leading to chronic EphA1 signaling in the brain. Moreover, we report that the EphA1 P460L variant triggers Rho-GTPase signaling dysregulation that could potentially contribute to spine morphology abnormalities and synaptic dysfunction observed in AD pathology.

molecular biology↗

bioRxiv2021

NSun2 deficiency promotes tau hyperphosphorylation and neurodegeneration through epitranscriptomic regulation of miR-125b

Overproduction or suppression of certain microRNAs (miRNAs) in Alzheimers disease (AD) brains promote alterations in tau proteostasis and neurodegeneration. However, the mechanisms governing how specific miRNAs are dysregulated in AD brains are still under investigation. Epitranscriptomic regulation adds a layer of post-transcriptional control to brain function during development and adulthood. NOP2/Sun RNA methyltransferase 2 (NSun2) is one of the few known brain-enriched methyltransferases able to modify mammalian non-coding RNAs and loss of function autosomal-recessive mutations in NSUN2 have been associated with neurological abnormalities in humans. Here, we provide evidence that NSun2 is expressed in adult human neurons in the hippocampal formation and prefrontal cortex. When we evaluated NSun2 protein expression in post-mortem brain tissue from AD patients we find is dysregulated which was also found in mice and human cellular AD models. To probe these observed alterations were unique to AD we further evaluated brain tissue from other tauopathies, observing NSun2 protein levels were similar between cases and controls. In a well-established Drosophila melanogaster model of tau-induced toxicity we investigated the pathological role of NSun2 observing that reduction of NSun2 protein levels exacerbated tau toxicity, while overexpression of NSun2 partially abrogated the toxic effects. We further show using human induced pluripotent stem cell (iPSC) derived neuronal cultures that NSun2 deficiency results in tau hyperphosphorylation and we found in primary hippocampal neuronal cultures NSun2 levels decrease in response to amyloid-beta oligomers (A{beta}O). Furthermore, in mice, we observed that NSun2 deficiency promotes aberrant levels of m6A methylated miR-125b and tau hyperphosphorylation. Altogether, our study supports that neuronal NSun2 deficiency in AD promotes neurodegeneration by altering tau phosphorylation and tau toxicity through an epitranscriptomic regulatory mechanism and highlights a novel avenue for therapeutic targeting.

neuroscience↗

bioRxiv2020

The Caribbean-Hispanic Alzheimer's Brain Transcriptome Reveals Ancestry-Specific Disease Mechanisms

Ethnicity impacts Alzheimers disease risk, especially among Caribbean-Hispanics. We report the first RNA-sequencing analysis of brain tissue from 45 Alzheimers disease and control Caribbean-Hispanics. Data were compared with two independent samples of non-Hispanic Caucasians (total n=729). By identifying and characterizing those genes with ancestry- and region-specific expression patterns in Alzheimers disease, we reveal molecular insights that may help explain epidemiological disparities in this understudied aging population.

genomics↗

bioRxiv2019

MiR-219 deficiency in Alzheimer’s disease contributes to neurodegeneration and memory dysfunction through post-transcriptional regulation of tau-kinase network

Intracellular accumulation of hyperphosphorylated misfolded tau proteins is one of the main neuropathological hallmarks in Alzheimers disease (AD) and related tauopathies. Hence, knowledge and understanding of disease mechanisms altering tau proteostasis and inducing cytotoxicity is critical. MicroRNAs (miRNAs) are capable of binding to and silencing many target transcripts, providing an additional level of regulation that complements canonical transcriptional pathways. Therefore, observed abnormalities in their expression patterns in neurodegeneration suggest alterations of microRNA-target networks as drivers of cellular dysfunction in the disease. Strikingly, here we have found in autopsy brain tissue that miRNA miR-219 expression levels are decreased in a brain region early affected in AD patients, the entorhinal cortex. Our bioinformatics analysis indicates miR-219 is predicted to target Calcium/calmodulin-dependent protein kinase 2 gamma subunit (CAMK2{gamma}), Tau tubulin kinase 1 (TTBK1) and Glycogen synthase kinase 3 beta (GSK3{beta}), which are all implicated in the generation of abnormal hyperphosphorylated tau. We reveal human proteomic data supporting dysregulation in the levels of predicted miR-219 targets in the entorhinal cortex. In mammalian cellular models, we found that downregulation of miR-219 de-repress synthesis of three tau kinases, CAMK2{gamma}, TTBK1 and GSK3{beta} on the post-transcriptional level resulting in tau phosphorylation and cell toxicity. Finally, we show that deficiency of miR-219 in vivo promotes age dependent neurodegeneration in the adult brain, with enhanced alterations in tau proteostasis, presynaptic terminals and memory impairment. Taken together, our data implicate miRNA dysregulation central to AD etiopathogenesis and suggest potential targets for the treatment of AD and related tauopathies.

neuroscience↗