R31 - Microporous Annealed Particle Delivery of Synaptogenic Factor TSP-1 Does not Inhibit Vascular Repair

Friday, October 10, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Aiden Pasinsky

Undergraduate Researcher
Duke University, Utah, United States

Co-Author(s)

Aiden Pasinsky

Undergraduate Researcher
Duke University, Utah, United States
NP

Nhi V. Phan

Graduate Student
Duke University, United States
YY

Yan Yang

Undergraduate Researcher
Duke University
Ellicott City, Maryland, United States
Zoe Meadows

Undergraduate Research Assistant
Duke University, United States
AE

Anna Edgcomb

Undergraduate Research Assistant
Duke University, United States
TL

Ting Ting Li

Undergraduate Researcher
Duke University, United States
Augustus J. Adams

Undergraduate Lab Assistant
Segura Lab, Duke University
CARY, North Carolina, United States

Primary Investigator(s)

TS

Tatiana Segura

Professor of Biomedical Engineering
Duke University, United States

Introduction: : Ischemic stroke, an abrupt arterial occlusion halting blood flow to brain tissue, comprises most stroke cases and leaves survivors with profound functional deficits. Stroke triggers a brief window of endogenous plasticity that rarely suffices for lasting repair. Re-establishing blood flow, axonal architecture, and synaptic connectivity in the infarct cavity is therefore central to functional recovery. We hypothesize that pairing an injectable microporous annealed particle (MAP) scaffold [1] with factor‑specific nanoparticles can synchronously drive angiogenesis and synaptogenesis. Vascular endothelial growth factor (VEGF) is loaded into ∼100 nm heparin nanoparticles (NPs) and clustered within the scaffold (CLUVENA) to spur vessel ingrowth [2]. Thrombospondin‑1 (TSP‑1) (an astrocyte‑secreted synaptogenic glycoprotein that is anti‑angiogenic in free form) is conjugated to separate NPs to induce synapse formation. We test how these cues in combination remodel the photothrombotic stroke cavity in mice.

Materials and

Methods: : C57BL/6 mice received an unilateral cortical photothrombotic stroke. On post‑stroke day 5, 6 µL of one treatment was stereotactically injected into the lesion: (i) blank MAP, (ii) CLUVENA (VEGF NPs + MAP), (iii) TSP‑1 NPs + VEGF NPs + MAP, (iv) soluble TSP‑1 + soluble VEGF + MAP, or (v) no‑material control. At day 15 brains were perfused, sectioned, and stained for DAPI, tomato lectin (TL, perfused vessels), NF200 (neurons), and vGlut1 (presynaptic marker). Confocal images of infarct and peri‑infarct zones (N = 3-5 animals/group) were analyzed for cell repopulation (% DAPI area), vascular density and branch length (TL +), axonal invasion (% NF200 area), and synaptic puncta (under analysis). Statistics: one‑way ANOVA with Sidak post‑hoc, α = 0.05.

Results, Conclusions, and Discussions:: Nanoparticle‑conjugated TSP‑1 (TSP‑NP) preserved angiogenesis: vessel density and maximum branch length were statistically indistinguishable from the MAP‑only scaffold and from the pro‑angiogenic CLUVENA group (p > 0.05), confirming that the combination therapy does not hinder vessel ingrowth. Similarly, soluble TSP‑1 markedly increased vascular ingrowth, boosting infarct‑core vessel density versus MAP (p < 0.05). TSP‑1 NP supported similar cell infiltration (% DAPI area) compared with MAP whereas soluble TSP-1 was significantly lower. In the peri‑infarct cortex, both TSP formulations again matched MAP for vascular density.
Neuronal and synaptic remodeling after TSP‑1 delivery. NF200 staining and quantitative analyses reveal axonal presence in the infarct core and peri‑infarct cortex. CLUVENA + MAP scaffolds enabled modest axonal repopulation of the core. A prior MAP study demonstrated decreased atrophy and enhanced NF200 axonal infiltration3. Both soluble TSP‑1 and nanoparticle‑bound TSP‑1 (TSP‑NP) showed significantly poorer axonal entry, well below CLUVENA levels, indicating that early TSP‑1 exposure suppresses elongation.
In peri‑infarct tissue, MAP showed the most axonal presence; TSP‑NP fell below MAP and was statistically indistinguishable from soluble TSP‑1, showing a potential trade‑off between synaptogenic signaling and neuron outgrowth at the border zone. Ongoing puncta mapping demonstrates that TSP‑NP, despite limited axon invasion, increases synaptic marker density, suggesting sustained nanoparticle delivery biases neurons toward synapse rebuilding rather than further extension.

Delivering regenerative cues on size‑tuned nanoparticles within a MAP scaffold decouples competing repair programs. VEGF‑NPs restore a perfusable vascular bed, while TSP‑1 NPs bias neurons toward synaptogenesis without blocking angiogenesis. However, TSP-1 appears to inhibit axonal elongation. These findings suggest a delayed delivery strategy: (1) early CLUVENA to rebuild vasculature, (2) delayed TSP‑1 NP release to solidify new circuits when axons have reached their targets. Future work will integrate a degradable coating for staggered TSP‑1 release and assess long‑term functional recovery. Our platform offers a modular route to coordinate the vascular‑neuronal dialogue essential for rebuilding the stroke‑damaged brain.

Acknowledgements and/or References (Optional): : Nih LR, Sideris E, Carmichael ST, Segura T. Injection of microporous annealing particle (MAP) hydrogels in the stroke cavity reduces gliosis and inflammation and promotes NPC migration to the lesion. Advanced Materials 2017;29:1606471. doi:10.1002/adma.201606471

Erning, K., Wilson, K. L., Smith, C. S., Nguyen, L., Joseph, N. I., Irengo, R., Cao, L. Y., Cumaran, M., Shi, Y., Lyu, S., Riley, L., Dunn, T. W., Carmichael, S. T., & Segura, T. (2025). Clustered VEGF nanoparticles in microporous annealed particle (MAP) hydrogel accelerates functional recovery and brain tissue repair after stroke. bioRxiv. https://doi.org/10.1101/2025.01.30.635733

Sideris E, Yu A, Chen J, Carmichael ST, Segura T. Hyaluronic acid particle hydrogels decrease cerebral atrophy and promote pro‑reparative astrocyte/axonal infiltration in the core after ischemic stroke. bioRxiv 2019. doi:10.1101/76829