Biology subjects

Spiller, K.

Publications and source records attributed to Spiller, K..

4 recordsLinked to original sources

bioRxiv2026

Reciprocal macrophage-MSC crosstalk drives immunomodulatory and regenerative phenotypes in a mineralized collagen scaffold

Critical sized craniomaxillofacial bone defects do not heal naturally and often exhibit chronic inflammatory responses that restrict regeneration. It is increasingly apparent that biomaterials must facilitate dynamic crosstalk between immune cells, such as macrophages, and osteoprogenitors to resolve inflammation and accelerate regeneration. Here, we evaluate interactions between macrophages in a neutral (M0) or pro-inflammatory (M1) state with mesenchymal stem cells (MSCs) in a basal or licensed state within a mineralized collagen scaffold. We reveal that MSC-macrophage crosstalk influences significant changes in osteoprogenitor cell differentiation and immune cell polarization. Notably, crosstalk between MSCs and macrophages drives an early-stage inflammatory response, which enhances the immunomodulatory activity of MSCs via secretion of IL-6, an effect that is heightened for already licensed MSCs. The presence of macrophages in the co-cultures upregulated osteogenic (ALPL, BMP2, COL1A2, and RUNX2) and angiogenic genes (ANGPT1) in basal MSC groups. Further, MSC-macrophage interactions subsequently drive increased M2-like macrophage polarization as early as 7 days of culture, as indicated by surface marker expression. These findings show that biomaterial scaffolds can be leveraged as mediators of MSC-mediated immunomodulation with an emphasis on achieving early-stage pro-inflammatory phenotypes that drive subsequent macrophage polarization and markers of increased regenerative potency.

bioengineering↗

bioRxiv2026

Mineralized collagen scaffold pore architecture and glycosaminoglycan content biases anti-inflammatory macrophage phenotype

Macrophages play a central role in early immune response after injury that can shape the success or failure of craniomaxillofacial (CMF) bone repair. While mineralized collagen glycosaminoglycan (GAG) scaffolds have been developed to support osteogenesis, here we define how scaffold pore size, pore alignment, and glycosaminoglycan (GAG) composition influence human monocyte-derived macrophage polarization. We establish flow cytometry, secretome, and gene expression benchmarks to assess primary macrophage polarization toward M1 versus M2 phenotypes in response to cytokine cocktails in 2D culture and 3D scaffolds. We then define the kinetics macrophage polarization in response to scaffold pore architecture and composition in the absence of exogenous cytokines. All scaffold variants support an early pro-inflammatory response followed by a shift toward M2-like phenotypes over seven days reflected by increased CD206 expression, secretion of pro-healing factors such as CCL18, and upregulation of M2a- and M2c-associated genes. Anisotropic scaffolds with smaller pores more robustly drove angiogenic and extracellular matrix related gene expression as well as earlier emergence of M2-like phenotypes. Scaffold GAG chemistry provided an additional tuning mechanism, with chondroitin-6-sulfate variants promoting the greatest late-stage M2 surface marker expression, heparin variants accelerating early M2 and pro-angiogenic phenotypes, and chondroitin-4-sulfate variants dampening both M1 and M2 phenotypes at early timepoints. These findings demonstrate that mineralized collagen scaffolds intrinsically guide macrophage polarization toward pro-regenerative states but that scaffold structure and composition can be used to shape the kinetics and intensity of these responses. These insights provide a critical foundation for immuno-instructive biomaterial designs that enhance CMF bone repair.

bioengineering↗

bioRxiv2024

Effects of injury size on local and systemic immune cell dynamics in volumetric muscle loss

We took a systems approach to the analysis of macrophage phenotype in regenerative and fibrotic volumetric muscle loss outcomes in mice together with analysis of systemic inflammation and of other leukocytes in the muscle, spleen, and bone marrow. Macrophage dysfunction in the fibrotic group occurred as early as day 1, persisted to at least day 28, and was associated with increased numbers of leukocytes in the muscle and bone marrow, increased pro-inflammatory marker expression in splenic macrophages, and changes in the levels of pro-inflammatory cytokines in the blood. The most prominent differences were in muscle neutrophils, which were much more abundant in fibrotic outcomes compared to regenerative outcomes at day 1 after injury. However, neutrophil depletion had little to no effect on macrophage phenotype or on muscle repair outcomes. Together, these results suggest that the entire system of immune cell interactions must be considered to improve muscle repair outcomes.

bioengineering↗

bioRxiv2024

Marginated neutrophils in the lungs effectively compete for nanoparticles targeted to the endothelium, serving as a part of the reticuloendothelial system

Nanomedicine has long pursued the goal of targeted delivery to specific organs and cell types but has not achieved this goal with the vast majority of targets. One rare example of success in this pursuit has been the 25+ years of studies targeting the lung endothelium using nanoparticles conjugated to antibodies against endothelial surface molecules. However, here we show that such "endothelial-targeted" nanocarriers also effectively target the lungs numerous marginated neutrophils, which reside in the pulmonary capillaries and patrol for pathogens. We show that marginated neutrophils uptake of many of these "endothelial-targeted" nanocarriers is on par with endothelial uptake. This generalizes across diverse nanomaterials and targeting moieties and was even found with physicochemical lung tropism (i.e., without targeting moieties). Further, we observed this in ex vivo human lungs and in vivo healthy mice, with an increase in marginated neutrophil uptake of nanoparticles caused by local or distant inflammation. These findings have implications for nanomedicine development for lung diseases. These data also suggest that marginated neutrophils, especially in the lungs, should be considered a major part of the reticuloendothelial system (RES), with a special role in clearing nanoparticles that adhere to the lumenal surfaces of blood vessels. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=172 SRC="FIGDIR/small/597904v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@17e0518org.highwire.dtl.DTLVardef@809eb6org.highwire.dtl.DTLVardef@33d9a7org.highwire.dtl.DTLVardef@169863_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗