Biology subjects

Griffin, D. R.

Publications and source records attributed to Griffin, D. R..

6 recordsLinked to original sources

bioRxiv2026

Fibronectin Tethering as a Shear-thinning Bio-Annealing Strategy for Granular Hydrogels

Granular hydrogel scaffolds (GHS) are injectable, integrative biomaterials built from hydrogel microparticles that permit rapid cell infiltration independent of scaffold degradation. Microporous annealed particle (MAP) scaffolds, a sub-class of GHS, use inter-microparticle crosslinks to anneal adjacent particles, providing greater mechanical stability than purely jammed assemblies. A growing range of inter-particle crosslinking strategies, including covalent photo-initiated radical polymerization and reversible guest-host chemistries, some intended to mimic extracellular matrix (ECM) viscoelasticity, focus on mechanical stabilization, while surface bioactivity is typically added separately via orthogonally tethered cell-adhesion ligands such as RGD, a peptide derived from fibronectin (FN), a key mediator of cell-ECM and ECM-ECM interactions. Here, we present an alternative that unifies these functions: coating MAP microparticle building blocks with covalently bound fibronectin to create fibronectin-modified MAP (FN-MAP). FN-MAP exhibits shear-thinning annealing with complete recovery of scaffold mechanics after physical mixing. Human lung fibroblasts respond favorably, adopting spread morphologies with high viability. Translationally, FN-MAP shows proof-of-principle promise for 3D bioprinting (greater stability and higher print resolution) and wound healing (increased epidermal closure in a diabetic mouse model). FN-MAP thus delivers both increased scaffold strength and bioactivity without exogenous soluble linkers or mixed particle populations.

bioengineering↗

bioRxiv2025

Development of a Clinically Relevant Rabbit Model of Acute Laryngeal Injury

ObjectivesAcute Laryngeal Injury (ALgI) is created as a result of endotracheal tube pressure ulcer formation leading to fibrosis and inflammation. This condition often leads to airway obstruction and voice and swallowing dysfunction. This study demonstrates a reliable animal model of ALgI to reproduce the acute wound process seen clinically, to explore the pathophysiology of this disease process, and serve as a reproducible injury suitable for the evaluation of therapeutic interventions. MethodsAn ALgI model was developed in New Zealand White rabbits using precise mucosal stripping of the posterior larynx, followed by intubation with an oversized 4.0 endotracheal tube for one hour to mimic intubation-associated trauma and pressure ischemia. Laryngoscopy and laryngeal harvest were performed two weeks post-injury for histologic and immunofluorescent evaluation. ResultsInjured rabbits demonstrated an eight-fold increase in posterior glottic thickness (1.57mm vs. 0.19mm in controls; p=0.0004) and eleven-fold increase in collagen content (1.93mm2 vs. 0.17mm2; p=0.005). Collagen subtype analysis revealed a shift toward active collagen within the injured larynx compared to the uninjured, with increased type III collagen (69.0%% vs. 26.1%; p<0.0001) and reduced type I collagen (27.2% vs. 73.9%; p<0.0001) in the posterior glottis, consistent with the proliferative phase of wound healing. Collagen fiber alignment analysis demonstrated increased coherency in injured tissues (0.36 vs. 0.21; p=0.023), indicating early organized collagen formation consistent with scar formation within the posterior glottis. ConclusionsThe model offers a robust platform for studying the acute pathogenesis of laryngeal injury and for testing the treatment options in the management of ALgI. Level of EvidenceLevel III

bioengineering↗

bioRxiv2024

Novel wheat germ agglutinin-based mass cytometry cell barcoding reagent for heterogeneous, live or fixed sample

Sample multiplexing in flow cytometry is a powerful technique which allows for reduction of error, inclusion of control samples for batch effect correction, and reduction in both time and consumable usage. Current industry standard for barcoding in mass cytometry is an intracellular reagent, which requires fixation and permeabilization of sample prior to barcoding. We developed a barcode using the ubiquitous and well-tolerated membrane labeling lectin, wheat germ agglutinin. This barcode effectively labels all tested cell types, both live and fixed. We determine that barcode yields, or the ratio of debarcoded cells to total input cells, is stable in live pooled sample for at least an hour. This barcode does not show differential performance across major PBMC lineages. Thus, this universal wheat germ agglutinin-based barcode represents an advance in gentle, non-reactive cell surface barcoding for live cells.

cell biology↗

bioRxiv2022

A unique Thy-1-negative immuno-fibroblast population emerges as a key determinant of fibrotic outcomes to biomaterials

Microporous annealed particle (MAP) hydrogels are an exciting new development in biomaterial design. They regulate innate and acquired immunity which has been linked to their ability to evade normal host-material fibrosis. Yet, resident stromal fibroblasts, not immune cells, are the arbiters of the extracellular matrix assembly that characterizes fibrosis. In other idiopathic fibrotic disorders, a fibroblast subpopulation defined by its loss of cell surface Thy-1 expression is strongly correlated with degree of fibrosis. We have previously shown that Thy-1 is a critical v{beta}3 integrin regulator that enables normal fibroblast mechanosensing and here, leveraging non-fibrosing MAP gels, we demonstrate that Thy-1-/- mice mount a robust response to MAP gels that remarkably resembles a classical foreign body response. We further find that within the naive, Thy-1+ fibroblast population exists a distinct and cryptic SMA+ Thy-1- population that emerges in response to IL-1{beta} and TNF. Employing single-cell RNA sequencing, we find that IL-1{beta}/TNF-induced Thy-1- fibroblasts actually consist of two distinct subpopulations, both of which are strongly pro-inflammatory. These findings illustrate the emergence of a unique pro-inflammatory, pro-fibrotic fibroblast subpopulation that is central to material-associated fibrosis likely through amplifying local inflammatory signaling. Significance StatementDespite decades of research, implanted biomaterials are still significantly hampered by the foreign body response and fibrotic encapsulation. Advancements in material design and immunomodulation have made positive impacts, yet, a fuller mechanistic understanding of aberrant ECM remodeling in the biomaterial microenvironment could improve approaches in biomaterial-host interactions. Here, we leverage anti-fibrotic MAP hydrogels and demonstrate that their ability to evade fibrosis is linked to fibroblast Thy-1 (CD90) surface expression. Thy-1-/- mice exhibit elevated NF{kappa}B signaling and elevated fibrosis in response to MAP gel implantation. Interestingly, pro-inflammatory cytokines elicit a Thy-1-/SMA+ myofibroblast subpopulation. Single-cell RNA-Seq more fully identifies an immunofibroblast subpopulation defined by Thy-1 loss and a pro-inflammatory/fibrotic cytokine, chemokine, and cytokine receptor expression profile, suggesting a self-perpetuating pro-fibrotic subpopulation.

bioengineering↗

bioRxiv2020

Selective and Improved Photoannealing of Microporous Annealed Particle (MAP) Scaffolds

Microporous Annealed Particle (MAP) scaffolds consist of a slurry of hydrogel microspheres that undergo annealing to form a solid scaffold. MAP scaffolds have contained functional groups with dual abilities to participate in Michael-type addition (gelation) and radical polymerization (photoannealing). Functional groups with efficient Michael-type additions react with thiols and amines under physiological conditions, limiting usage for therapeutic delivery. We present a heterofunctional maleimide/methacrylamide 4-arm PEG macromer (MethMal) engineered for selective photopolymerization compatible with multiple polymer backbones. Rheology using two classes of photoinitiators demonstrates advantageous photopolymerization capabilities. Functional assays show benefits for therapeutic delivery and 3D printing without impacting cell viability.

bioengineering↗

bioRxiv2020

Activating an adaptive immune response from a hydrogel scaffold imparts regenerative wound healing.

Biomaterial scaffolds represent a promising approach for material-based tissue regeneration. We previously developed microporous annealed particle (MAP) hydrogels - a flowable, microparticle-based hydrogel in which neighboring hydrogel particles are linked in situ to form a porous scaffold that accelerates wound healing. To promote more extensive tissue ingrowth before scaffold degradation, we aimed to slow scaffold degradation by switching the chirality of the crosslinking peptides from L-peptides to D-peptides. Unexpectedly, despite showing the predicted slower enzymatic degradation in vitro, D-peptide crosslinked MAP hydrogel (D-MAP) hastened material degradation in vivo and imparted significant tissue regeneration to healed cutaneous wounds, including increased tensile strength and hair neogenesis. By themselves, D-chiral peptides were poor activators of macrophage innate immune signaling in vivo, but MAP particles elicit IL-33 type 2 myeloid cell recruitment which is amplified in vivo in the presence of D-peptides. Remarkably, D-MAP elicited significant antigen-specific immunity against the D-chiral peptides, and an intact adaptive immune system was required for the hydrogel-induced skin regeneration. These findings demonstrate that the generation of an adaptive immune response from a biomaterial is sufficient to induce cutaneous regenerative healing despite faster scaffold degradation.

bioengineering↗