A CRISPR Nasal Spray Shows Early Promise Against Brain Inflammation After Traumatic Injury
A gene-editing treatment delivered through the nose has reduced acute brain inflammation and improved early motor performance in mice after traumatic brain injury, according to a study published in Biomedical Microdevices. The experimental therapy uses lipid nanoparticles—tiny fat-based carriers already familiar from several nucleic-acid medicines—to transport CRISPR-Cas12a components into injured brain tissue. The particles were engineered to target Iba-1-positive myeloid cells, a group that includes resident microglia and infiltrating monocyte-derived macrophages. These immune cells can help clear debris and support repair, but after injury they may also produce inflammatory molecules that intensify secondary damage. In the new work, researchers focused on MAPK9, also known as JNK2, a stress-activated enzyme involved in inflammatory signaling. Rather than eliminating microglia or suppressing the immune response throughout the body, the strategy aims to reprogram the behavior of inflammatory cells inside the damaged brain. In a controlled cortical impact model, a standard laboratory simulation of traumatic brain injury, a single intranasal dose reduced inflammatory markers within 24 hours, decreased evidence of cell death, and was associated with better performance on a rotating-rod test. The findings are preliminary and come from small groups of male mice, but they point toward a non-invasive way to deliver gene-editing machinery to a difficult therapeutic target.
Traumatic brain injury begins with a mechanical insult, but much of the lasting damage can arise later. The initial impact can rupture blood vessels, disturb the blood–brain barrier, damage axons and neurons, and trigger excitotoxicity, oxidative stress, and cellular injury. The resulting chemical environment activates microglia, the central nervous system’s resident immune cells, while the damaged barrier permits circulating immune cells to enter the brain. This inflammatory response is not inherently harmful: activated microglia can remove dead cells and release signals that support tissue repair. The problem is that activation may persist or become excessively pro-inflammatory, leading to the release of cytokines, chemokines, and reactive nitrogen and oxygen species that injure nearby neurons and amplify immune recruitment. The researchers describe this process using markers associated with pro-inflammatory and reparative states, including iNOS and CD80 on one side and CD206 and Arg1 on the other. They also emphasize that the familiar “M1” and “M2” labels are an oversimplification. Modern single-cell studies show that microglia and macrophages occupy a continuum of overlapping, changing states. The therapeutic goal, therefore, is not to force every cell into a rigid category, but to shift the injured tissue toward a less damaging and more repair-supportive inflammatory environment.
MAPK9 is a member of the mitogen-activated protein kinase family, a network of serine/threonine enzymes that converts cellular stress into changes in gene expression and behavior. MAPK9, or JNK2, can be activated by injury-associated signals and influence transcription factors, cytokine production, apoptosis, and other processes relevant to brain trauma. To test whether it was a useful intervention point, the team first screened several candidate genes in mouse bone-marrow-derived macrophages stimulated with lipopolysaccharide and interferon-gamma, laboratory signals that induce a strongly inflammatory state. Among the targets examined, Mapk9 suppression produced one of the clearest changes in cell phenotype. Treated macrophages displayed more CD206-positive cells and fewer CD80-positive cells than inflammatory control cultures. Gene-expression tests showed reductions in Ccl2, Ccl3, Ccl4, Ccl5, Cxcl1, and Il1b, molecules that help recruit or activate additional immune cells. The researchers then repeated the test in primary mouse microglia. In those cultures, CRISPR treatment reduced Mapk9 messenger RNA and lowered Nos2, Cd80, Ccl2, and Nlrp3 expression, while increasing Mrc1, which encodes CD206, and Arg1. Western blotting confirmed that the corresponding iNOS protein was also reduced. These experiments suggested that MAPK9 is not merely a marker of inflammation but a potential molecular lever for changing the response of injured myeloid cells.
The delivery system was designed to solve one of the central problems in brain gene therapy: getting a large, fragile molecular payload into the right cells without exposing the entire body. The nanoparticles contained phospholipids, cholesterol, an ionizable lipid used to package nucleic acids, polyethylene glycol-linked lipid, and a fluorescent lipid that allowed the researchers to track them. Inside the particles were Cas12a protein and a guide RNA designed to recognize the mouse Mapk9 gene. Cas12a is an RNA-guided nuclease related to the more widely known Cas9. Once inside a cell, the guide directs the nuclease to a matching DNA sequence, where it can cut the genome and disrupt the targeted gene. The nanoparticles were then decorated with an antibody against Iba-1, a protein expressed by microglia and macrophages. This surface modification was intended to increase the likelihood that the particles would interact with these myeloid cells. Physical characterization found particles about 160 nanometers in diameter, with antibody attachment changing their surface charge but not substantially altering their size. The treatment was given through the nose, 30 minutes after injury, at a dose containing 20 milligrams per kilogram of the total lipid and CRISPR formulation. Intranasal administration can provide access to the brain through olfactory and trigeminal pathways and associated tissue spaces, potentially reducing the systemic exposure associated with injection into the bloodstream.
The mouse experiments used adult male C57BL/6J mice subjected to a controlled cortical impact over the left motor and somatosensory cortex. The injury was produced with a three-millimeter impact tip moving at 3.25 meters per second to a depth of 1.5 millimeters. The investigators compared intranasal delivery with retro-orbital injection and examined the distribution of fluorescent nanoparticles in the injured hemisphere. After nasal dosing, roughly 90 percent of nanoparticle-positive cells were associated with Iba-1-positive cells, compared with about 55 percent after retro-orbital administration. Within the injured cortex, approximately 35 percent of fluorescent particle-positive cells were associated with Iba-1-positive myeloid cells, whereas about 13 percent were associated with NeuN-positive neurons. The result indicates preferential targeting, not exclusive targeting: some particles still reached cells that did not express Iba-1. RNA imaging showed that Mapk9 transcripts increased in the peri-lesional cortex after injury and that the signal was associated with Iba-1-positive cells. In treated mice, Mapk9 messenger RNA was visibly reduced, including within the Iba-1-positive compartment. A separate analysis of publicly available single-cell RNA-sequencing data supported the biological rationale. At 24 hours after injury, the fraction of Mapk9-positive microglia rose from 4.39 percent in uninjured samples to 8.01 percent after cortical impact, while Mapk9-positive bone-marrow-derived monocytes and macrophages increased from 4.90 to 6.93 percent. The proportion of Mapk9-positive neurons changed little, strengthening the case for concentrating treatment on myeloid cells.
The molecular changes were accompanied by alterations in the appearance and abundance of immune cells around the lesion. In untreated injured mice, Iba-1-positive cells became more numerous and hypertrophic, with enlarged cell bodies and shorter, less-branched processes. This morphology is commonly associated with activation. Compared with vehicle-treated injured animals, mice receiving the CRISPR nanoparticles had fewer Iba-1-positive cells, fewer hypertrophic cells, and smaller cell bodies. The composition of the myeloid response also shifted. The proportion of iNOS-positive Iba-1 cells fell, while the proportion expressing CD206 rose. RNA in situ hybridization detected lower levels of tumor necrosis factor and interleukin-1 beta messenger RNA in the injured cortex after treatment. These cytokines are potent inflammatory signals capable of affecting neurons, blood vessels, glial cells, and infiltrating leukocytes. The therapy was also associated with fewer TUNEL-positive cells, a measure of DNA fragmentation commonly used to estimate cell death. On the rotarod, injured mice normally fell sooner than they had before trauma, but treated animals remained on the rotating apparatus longer than vehicle-treated injured mice at one day after injury. However, the intervention did not significantly reduce the gross lesion volume at this early time point. That distinction matters: a treatment can influence inflammatory signaling and short-term function before it produces a measurable reduction in the amount of tissue lost.
The researchers also looked for signs that the nanoparticles caused harm outside the brain. Traumatic brain injury itself raised serum amyloid A, an acute-phase inflammatory protein, and treatment reduced this increase. Serum aspartate aminotransferase was elevated after injury but did not differ significantly between treated and untreated injured animals, while liver AST activity remained unchanged across groups. Microscopic examination of the liver, kidney, spleen, heart, and lungs found no obvious treatment-associated abnormalities. The mice showed no reported differences in body weight or overt behavior during the short observation period. These results provide an initial safety signal, but they do not establish that the approach is safe for long-term use. CRISPR nucleases can create unintended edits, and the study primarily measured suppression of Mapk9 messenger RNA rather than directly sequencing the genome to quantify editing efficiency or detect off-target changes. The antibody against Iba-1 also cannot distinguish resident microglia from infiltrating macrophages. That distinction could be important because the two populations arise from different sources and may have different effects on recovery. The work used only male mice, relatively small experimental cohorts, and a single acute time point, leaving open questions about sex differences, dose, treatment timing, repeated administration, and effects on cognition.
The study’s most striking feature is the combination of a programmable gene-editing payload, cell-enriching nanoparticle design, and a route of administration that does not require surgery or direct injection into the brain. Yet the results remain a proof of concept rather than evidence of a ready-to-use treatment for people with head injuries. The researchers will need to determine how long MAPK9 suppression lasts, whether it improves neurological recovery over weeks or months, and whether early motor benefits translate into preserved cognition and reduced neurodegeneration. Future experiments should directly measure genomic edits in purified nanoparticle-positive cells, map uptake across neurons, astrocytes, neutrophils, and peripheral organs, and test the system in both sexes and larger animal cohorts. Human-relevant models, including induced-pluripotent-stem-cell-derived microglia, could reveal whether the same pathway operates in human immune cells. The distinction between preferential and exclusive targeting will also be crucial for clinical development: Iba-1 is shared by multiple myeloid populations, and broad suppression of inflammatory signaling could theoretically interfere with useful immune functions. Even with those caveats, the findings offer a vivid example of how nanomedicine and CRISPR technology are converging. Instead of attempting to silence the entire post-traumatic immune response, the approach seeks to deliver a molecular instruction to the cells most responsible for sustaining inflammation, potentially turning the nose into an unexpected gateway for treating the injured brain.
Subject of Research: Intranasal delivery of Iba-1-targeted CRISPR-Cas12a lipid nanoparticles to suppress MAPK9-driven neuroinflammation after traumatic brain injury
Subject of Research: Technology and Engineering
Article Title: Intranasal CRISPR lipid nanoparticles targeting MAPK9 attenuate neuroinflammation after traumatic brain injury
Article References: Kara, G., Holcomb, M., Hijazi, A. A., Ali, Y., López-Espinosa, J., Cruz-Pineda, L., Park, P., Flinn, H., Taylor, N., Galbraith, T., McMahon, L., Rostomily, R., Leonard, F., & Villapol, S. (2026). Intranasal CRISPR lipid nanoparticles targeting MAPK9 attenuate neuroinflammation after traumatic brain injury. Biomedical Microdevices, 28(3), Article 58. https://doi.org/10.1007/s10544-026-00843-9
Image Credits: AI Generated
DOI: 10.1007/s10544-026-00843-9
Keywords: traumatic brain injury, CRISPR-Cas12a, lipid nanoparticles, MAPK9, intranasal delivery, neuroinflammation, microglia, macrophages
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SCIENMAG. (August 28, 2026). Nasal CRISPR Lipid Nanoparticles Targeting MAPK9 Reduce Brain Inflammation After Traumatic Injury. https://scienmag.com/nasal-crispr-lipid-nanoparticles-targeting-mapk9-reduce-brain-inflammation-after-traumatic-injury/
SCIENMAG. “Nasal CRISPR Lipid Nanoparticles Targeting MAPK9 Reduce Brain Inflammation After Traumatic Injury.” Scienmag, 28 August 2026, https://scienmag.com/nasal-crispr-lipid-nanoparticles-targeting-mapk9-reduce-brain-inflammation-after-traumatic-injury/. Accessed 28 August 2026.
SCIENMAG. “Nasal CRISPR Lipid Nanoparticles Targeting MAPK9 Reduce Brain Inflammation After Traumatic Injury.” Scienmag. August 28, 2026. https://scienmag.com/nasal-crispr-lipid-nanoparticles-targeting-mapk9-reduce-brain-inflammation-after-traumatic-injury/
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