#4 — At the Intersections — June 27, 2026

Medications exist to prevent HIV, yet infection rates among women are on the rise. Examining the multiple barriers to health across different scales is the focus of ComplexityPod. We begin this week's issue with a look at HIV prevention. This week, we're looking at health and biology across different scales—from large organizations down to the level of the genome. So starting at the highest level, with the systems themselves. There's a study looking at how healthcare organizations can provide more equitable care, specifically in emergency departments. A collaboration called EQUIP Emergency worked with staff, leaders, and community members in three ERs. They found that while there was a commitment to equity, it was often pushed aside by other priorities. What kind of priorities? Was it a lack of will? It seems to have been more about a lack of resources. They were focused on immediate crises: ensuring enough staffing, training new people, and responding to things like the drug poisoning emergency and violence in the departments. So the capacity to focus on equity was consumed by just keeping the department running. The analysis suggests the solution is to treat equity as a foundational part of the organization, not a separate goal. Exactly. To link it to those key organizational issues from the start, involving everyone, rather than treating it as an add-on. Moving from the organizational scale to a specific population, a review looked at HIV pre-exposure prophylaxis, or PrEP, among women. Right, and the context is that even though HIV rates are increasing for cisgender and transgender women globally, the uptake of PrEP isn't meeting their needs. This review synthesized literature on why that is. What are the main barriers it identified? Several themes emerged. Things like the challenges of starting and stopping the medication, how effective public health messaging is, and the influence of women's own networks. It also pointed to intimate partner violence as a factor. And it mentioned something called “seasons of risk.” What does that refer to? That's where a person's perceived risk drops temporarily, which can lead them to stop taking the medication. The review noted that peer support was really important for building trust and keeping women engaged with PrEP. So it's not a single issue. The conclusion is that improving uptake requires a women-centered approach that tackles the clinical, social, and structural barriers all at once. Now let's scale down again, to the brain. Research from Lena Palaniyappan looks at a potential link between the brain's waste clearance system and ALS. The brain has a waste clearance system? What does it do? It’s called the glymphatic system, and it’s believed to help clear out neurotoxic proteins. Researchers used multimodal MRI to measure its function in patients with ALS compared to healthy controls. And what did they see? In patients with ALS, the glymphatic system's function was significantly reduced. They also showed widespread increases in cortical fluid and reductions in white matter integrity. So a failure in this cleaning system was found alongside these other physical changes in the brain and was associated with functional, cognitive, and emotional outcomes. Correct. It’s in vivo evidence suggesting glymphatic dysfunction is happening alongside clinical impairment in ALS. And another study, also with Palaniyappan, looks at white matter in a different condition: behavioral variant frontotemporal dementia, or bvFTD. Which is known for profound changes in behavior and personality. So how is white matter involved there? This study used a method to look at the local geometry of white matter fibers. It found both increased geometric distortion in some areas and, interestingly, decreased distortion in other frontotemporal tracts. Hold on, *decreased* distortion was linked to *greater* clinical severity? That seems counterintuitive. It does. But the analysis showed that this particular change in white matter geometry seemed to mediate the effects of brain atrophy on the severity of the symptoms. It’s a new way of understanding the neural basis for the impairments. From the brain's structure, we can go down to the cellular level. A review with Kathleen Hill examined the formation of keloid and hypertrophic scars. These are scars from abnormal wound healing. The review looked at the role of a substance called hyaluronan, a polysaccharide involved in inflammation and skin health. And what's its role in these scars? Is there too much of it, or too little? Too little. The findings indicate that hyaluronan concentration was lower in cell-based models of these scars compared to normal skin. Its location within the tissue was also off, which seems connected to altered gene expression. If it's missing, does that suggest adding it back could be a treatment? That's the idea. The review notes that both injected and topical applications of hyaluronan have shown some short-term success in improving the appearance of keloid scars. It suggests the substance has potential, but more clinical validation is needed. So for the final step down in scale, we arrive at the genome itself. Another study with Kathleen Hill looks at what are called genomic signatures. These are basically nucleotide patterns that are specific to a species. The researchers wanted to see how consistent these signatures are across an entire genome, even in complex and repetitive regions. So like a genetic fingerprint. Did they find one? They did. Using a visualization technique on the human genome and three other eukaryotes, they showed each species has a stable signature across most chromosomes. The signature only departed from the norm in predictable ways, mostly in areas with a lot of tandem repeats. Is there a practical application for that finding? Yes. Based on this, they developed a computational pipeline that can automatically find a short, representative segment of a genome to act as a proxy for the whole thing. And that works? A small piece can stand in for the whole code? For certain tasks, yes. Using these proxies for something like taxonomic classification actually improved accuracy by seven percent compared to using a random segment. It's a practical method that builds on this new evidence about how these signatures are structured at the genome scale. That's all for this issue. We'll return next week with summaries of new research. From ComplexityPod, thanks for listening.