Stem Cell Models to Reveal Why Parkinson’s Disease Hits Women Differently

Parkinson’s disease has long been studied as if it were a single illness, yet a growing body of evidence shows that it does not affect men and women in the same way. Men carry an approximately 1.5 to 2 times greater risk of developing the disease compared to women, according to a 2015 analysis of baseline data from the NIH Exploratory Trials in Parkinson’s Disease Long-term Study-1 published in PLOS ONE. Women, meanwhile, report a lived experience of the disease that differs from men’s, including differences in the time it takes to receive a diagnosis and in the burden of non-motor symptoms relative to motor symptoms. Despite these well-recognized disparities, women remain under-represented in clinical and experimental studies of Parkinson’s, and much of the biological underpinning of sex differences in the disease remains to be elucidated, as a 2025 review published in Biology of Sex Differences made clear. A new collaboration announced in Tucson aims to begin closing that gap at the level of individual cells.

Critical Path Institute, or C-Path, a Tucson-based nonprofit founded in 2005 as a public-private partnership in response to the FDA’s Critical Path Initiative, has announced a research collaboration with the University of Arizona to investigate the cellular mechanisms that drive Parkinson’s disease in women. The two-year project will be led by Lalitha Madhavan, M.D., Ph.D., Professor of Neurology at the University of Arizona. At its core, the study will compare brain cells grown from women and men living with Parkinson’s disease, searching for biological differences that may help explain why the disease presents and progresses differently between the sexes. The work represents a deliberate turn toward human-relevant laboratory models in a field where animal systems and clinical data alone have struggled to answer mechanistic questions.

The collaboration is embedded within C-Path’s Global Evidence in Medicine for Parkinson’s Disease initiative, known as GEM-PD, which was launched in March 2025 to address how Parkinson’s uniquely affects women. The initiative focuses on sex-specific biological factors that may influence disease progression, symptoms, and treatment. The new University of Arizona partnership constitutes the real-world evidence workstream within GEM-PD and advances C-Path’s broader vision of addressing unmet needs in research and drug development. For an organization that has built its reputation on convening international consortia that currently include more than 1,600 scientists and representatives from government and regulatory agencies, academia, patient organizations, disease foundations, and pharmaceutical and biotech companies, the project marks a continuation of a strategy that treats data generation and regulatory science as inseparable.

The experimental design centers on induced pluripotent stem cells, or iPSCs, a technology that allows mature cells to be reprogrammed back into a stem-like state and then directed to become almost any cell type in the body. Researchers at the University of Arizona will differentiate cortical neurons from well-characterized female and male sporadic Parkinson’s iPSC lines obtained through the Parkinson’s Precision Medicine Initiative, or PPMI, a landmark longitudinal observational study sponsored by The Michael J. Fox Foundation for Parkinson’s Research. Following review by the study’s Biospecimen Review Committee, PPMI cell lines are made available to qualified investigators to enable biomarker research, therapeutic development, drug screening, and disease modeling. In other words, the neurons that will populate the Tucson laboratory carry the genetic backgrounds of real patients, offering a window into disease biology that generic cell lines cannot provide.

Once the neurons are generated, the comparison will proceed across multiple layers of cellular function. The Parkinson’s-derived neurons will be measured against age- and sex-matched controls across cellular, functional, and proteomic endpoints, using established cellular assays, quantitative proteomics, and electrophysiological analyses. Cellular assays can reveal differences in survival, stress responses, and protein handling; quantitative proteomics provides an unbiased inventory of the proteins expressed in each cell population, flagging molecular pathways that behave differently in female versus male disease contexts; and electrophysiological analyses probe how the neurons fire and communicate, the functions most directly tied to the degeneration of dopaminergic circuits in Parkinson’s disease. Triangulating across these endpoints is intended to distinguish robust, reproducible sex-specific signatures from noise.

A defining feature of the project is its reliance on New Approach Methodologies, or NAMs, a category of human-cell-based and non-animal research models designed to address the limitations of traditional preclinical systems. NAMs have gained momentum across the drug development pipeline as regulators and sponsors seek models that better predict human biology while reducing dependence on animal testing. In addition to the project with Dr. Madhavan, C-Path has prioritized NAMs applications in drug development through its New Approach Methodologies Developer Coalition. The Parkinson’s collaboration effectively puts that policy commitment into practice, applying a human-derived disease model to a question, sex-specific mechanisms in Parkinson’s, that has been difficult to interrogate in conventional systems.

The partnership itself has deep roots. C-Path and the University of Arizona have a long history of collaboration, and both institutions framed the new project as an acceleration of an existing relationship. Kristen Swingle, M.S., C-Path’s President and Chief Operating Officer, said that C-Path and the University of Arizona have a long history together and that this new phase of the partnership further accelerates the organization’s commitment to understanding how Parkinson’s affects women. She noted that the specialized neurons that Dr. Madhavan’s lab will grow in Tucson are essential to answering questions that clinical information alone cannot, and expressed pride in deepening investments in human-relevant research models that share a commitment to scientific rigor, adding that C-Path is grateful to the University of Arizona for bringing its stem cell expertise to important projects like this one.

Dr. Madhavan, whose laboratory specializes in stem cell-based disease modeling, emphasized the continuity of the collaboration from the university’s side. She said the University of Arizona is proud to continue to work with C-Path after years of success together and that both share a strong commitment to understanding this disease in the people it affects. With C-Path’s newest commitment, she said, the team is pleased to apply its stem cell program to create human-derived models that make vital scientific questions, such as the mechanisms of Parkinson’s in women, possible to answer. That framing captures the central promise of iPSC technology in neurodegenerative disease research: the ability to pose mechanistic questions about living human neurons from patients who cannot be biopsied in any meaningful way.

The project is structured as a multi-year partnership extending from April 2026 through June 2028 across four defined milestones. The researchers expect to share their results at scientific conferences such as the International Society for Stem Cell Research and the AD/PD meeting, culminating in a primary research paper. That timeline suggests a deliberate staging, in which cell line characterization, neuronal differentiation, and multi-endpoint comparisons are sequenced so that findings can be validated and disseminated progressively rather than held until the end of the funding period. For a field in which sex-specific findings have often been reported piecemeal, a milestone-driven design with public dissemination points could help ensure that results reach both the clinical community and trial designers in a timely way.

The ultimate ambition extends beyond the laboratory bench. Diane Stephenson, Ph.D., Vice President of Neurology at C-Path and Executive Director of the Critical Path for Parkinson’s Consortium, described addressing sex-specific biology as an essential and long-overdue step in Parkinson’s research. She said this foundational work delivers the mechanistic evidence required to elevate how clinical trials are designed and to ensure that new therapies are evaluated with greater precision. If the Tucson collaboration succeeds in identifying reproducible sex-specific cellular signatures of Parkinson’s disease, those signatures could inform stratification strategies in future trials, sharpen the interpretation of real-world evidence, and ultimately support the development of therapies that account for the biology of the roughly half of the patient population whose disease mechanisms have historically received less experimental attention. For women living with Parkinson’s, whose reports of differing symptom burdens and diagnostic experiences have often outpaced the underlying science, the project represents a concrete investment in evidence.

Subject of Research: Translational stem cell research into sex-specific cellular mechanisms of Parkinson's disease in women

Article Title: C-Path partners with University of Arizona on translational research of Parkinson’s disease in women

Article References: C-Path partners with University of Arizona on translational research of Parkinson’s disease in women. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Parkinson's disease, women's health, stem cells, induced pluripotent stem cells, new approach methodologies, translational research, Critical Path Institute, University of Arizona, proteomics, electrophysiology, drug development, real-world evidence