Biomedical subjects

Julia C Fitzgerald

Publications and source records attributed to Julia C Fitzgerald.

3 recordsLinked to original sources

PubMed2026

Prolonged In Vitro Expansion Shapes the Neuro-Supportive Potential of Jaw Periosteum Secretomes: Implications for Secretome Product Quality.

Nerve injuries are frequent complications of complex oral and maxillofacial surgical procedures, particularly following extensive tumor resections. Secretome-based, cell-free therapies derived from mesenchymal stromal cells have emerged as promising regenerative approaches; however, robust manufacturing requires the identification of critical quality attributes (CQAs) that ensure product potency and consistency. The influence of replicative senescence during in vitro expansion on the quality of jaw periosteum-derived mesenchymal stromal cell (JPC) secretomes has not yet been established. This study investigated whether the expansion state of JPCs affects the composition and neuro-supportive potency of their secretomes. Secretomes from four independent JPC donors were collected separately at early and late passages, pooled within each passage-specific preparation, and applied to human induced pluripotent stem cell-derived neurons. Neuronal survival, neurite outgrowth, and neuronal marker expression were assessed as functional readouts. Secretome composition was characterized by quantitative proteomics and enzyme-linked immunosorbent assay (ELISA) of selected senescence-associated secretory phenotype (SASP) factors. Secretomes derived from early-passage JPCs significantly enhanced neuronal survival and neurite outgrowth, whereas late-passage secretomes displayed reduced neuro-supportive activity. Proteomic profiling identified a pronounced shift toward inflammatory and stress-associated signaling, whereas performed ELISAs confirmed senescence-associated remodeling of the secretome, including increased abundance of SASP-associated factors in late-passage preparations. These findings demonstrate that prolonged in vitro expansion profoundly influences both the composition and biological potency of JPC-derived secretomes. Collectively, this study identifies the passage-associated senescence-like phenotype of JPCs as a key determinant of secretome quality and supports its consideration as a critical quality attribute for the manufacturing and standardization of JPC-derived secretome products. Monitoring and controlling the expansion state of JPCs may therefore be essential to ensure the consistency, potency, and clinical translation of secretome-based regenerative therapies.

Humans↗

PubMed2025

Interactions of Oligodendrocyte Precursor Cells and Dopaminergic Neurons in the Mouse Substantia Nigra.

Parkinson's disease (PD) is a prevalent neurodegenerative disease caused by the death of dopaminergic neurons within the substantia nigra pars compacta (SNpc) region of the midbrain. Recent genomic and single cell sequencing data identified oligodendrocytes and oligodendrocyte precursor cells (OPCs) to confer genetic risk in PD, but their biological role is unknown. Although SNpc dopaminergic neurons are scarcely or thinly myelinated, there is a gap in the knowledge concerning the physiological interactions between dopaminergic neurons and oligodendroglia. We sought to investigate the distribution of OPCs with regard to the myelination state in the mouse substantia nigra (SN) by high-resolution imaging to provide a morphological assessment of OPC-dopaminergic neuron interactions and quantification of cell numbers across different age groups. OPCs are evenly distributed in the midbrain throughout the lifespan and they physically interact with both the soma and axons of dopaminergic neurons. The presence of OPCs and their interaction with dopaminergic neurons does not correlate with the distribution of myelin. Myelination is sparse in the SNpc, including dopaminergic fibers originating from the SNpc and projecting through the substantia nigra pars reticulata (SNpr). We report that OPCs and dopaminergic neurons exist in a 1:1 ratio in the SNpc, with OPCs accounting for 15%-16% of all cells in the region across all age groups. This description of OPC-dopaminergic neuron interaction in the midbrain provides a first look at their longitudinal distribution in mice, suggesting additional functions of OPCs beyond their differentiation into myelinating oligodendrocytes.

Animals↗

PubMed2024

Proteome Dynamics in iPSC-Derived Human Dopaminergic Neurons.

Dopaminergic neurons participate in fundamental physiological processes and are the cell type primarily affected in Parkinson's disease. Their analysis is challenging due to the intricate nature of their function, involvement in diverse neurological processes, and heterogeneity and localization in deep brain regions. Consequently, most of the research on the protein dynamics of dopaminergic neurons has been performed in animal cells ex vivo. Here we use iPSC-derived human mid-brain-specific dopaminergic neurons to study general features of their proteome biology and provide datasets for protein turnover and dynamics, including a human axonal translatome. We cover the proteome to a depth of 9409 proteins and use dynamic SILAC to measure the half-life of more than 4300 proteins. We report uniform turnover rates of conserved cytosolic protein complexes such as the proteasome and map the variable rates of turnover of the respiratory chain complexes in these cells. We use differential dynamic SILAC labeling in combination with microfluidic devices to analyze local protein synthesis and transport between axons and soma. We report 105 potentially novel axonal markers and detect translocation of 269 proteins between axons and the soma in the time frame of our analysis (120 h). Importantly, we provide evidence for local synthesis of 154 proteins in the axon and their retrograde transport to the soma, among them several proteins involved in RNA editing such as ADAR1 and the RNA helicase DHX30, involved in the assembly of mitochondrial ribosomes. Our study provides a workflow and resource for the future applications of quantitative proteomics in iPSC-derived human neurons.

Humans↗