Biology subjects

Chen, K.

Publications and source records attributed to Chen, K..

At least 19 recordsLinked to original sources

bioRxiv2026

In-vivo MRI of noradrenergic and dopaminergic nuclei predicts future cognition and Alzheimers disease progression

Noradrenergic and dopaminergic nuclei modulate cognition, and post-mortem data indicate they are affected early in the neurodegenerative cascade of Alzheimers disease. We derived in-vivo locus coeruleus (LC) and substantia nigra-ventral tegmental area (SN-VTA) MRI integrity measures from 739 ADNI participants, examined MRI-histology correspondence in individuals with both in-vivo imaging and post-mortem data, and tested whether these measures reflect early MRI-indexed degeneration predicting later cognitive decline. LC and SN-VTA contrast predicted cognitive and behavioral function 10 years later, despite only weak associations with current function. LC- and SN-VTA-associated brain-wide atrophy patterns aligned with PET-derived norepinephrine-transporter and dopamine-receptor maps, respectively. A one-standard-deviation decrease in baseline LC contrast was associated with 84% higher five-year odds of MCI-to-AD progression, and predictive effects of the catecholaminergic nuclei were mediated by their corresponding atrophy patterns. The SN-VTA pattern was associated with less amyloid PET-related memory decline. Together, these findings establish LC and SN-VTA MRI contrast as markers of early neurodegeneration that forecast cognitive decline years before clinical onset.

neuroscience↗

bioRxiv2026

A spatial and single-cell transcriptomic atlas of the embryonic synovial joint and its explant model

Synovial joint formation requires the coordinated differentiation of multiple cell types while balancing opposing migratory cues that recruit joint progenitors and exclude other populations. More specifically, a subset of limb bud mesenchyme is recruited into the interzone while neighboring chondrocytes and endothelial cells are excluded. Existing single-cell references sample this process sparsely, without position, or without the surrounding mesenchyme. Here, we present an atlas of the mouse hindlimb from E11.5 to E15.5 that pairs 228,703 single-cell transcriptomes with 47 spatial transcriptomic sections, annotates 56 cell types by their location, and extends the same profiling to limb explant culture. Explants preserve the lineages and axial patterning of the limb for three days, with delayed chondrocyte hypertrophy. Using the atlas, we found that Sema3c is co-expressed with Sox9 and Gdf5 during condensation and is required for chondrogenesis and joint formation in culture; that interzone cells carry a chondrogenic signature early and a tenogenic signature late; and that a core interzone signature includes eleven previously unreported markers, one of which, Igfbp5, is required for knee formation in explants.

developmental biology↗

bioRxiv2026

OFC-SV: Interpreting structural variants in African and Asian cohorts with non-syndromic orofacial clefts

OFC-SV is a web-based data portal designed to help interpret structural variants (SVs) in non-syndromic orofacial clefts genomic data published by The Gabriella Miller Kids First Pediatric Research Program. The portal offers a user-friendly way to explore 41 novel SV genes (of these 13 sharing regulatory perturbations already reported in the literature as SNV genes) potentially responsible for non-syndromic OFC (nsOFC) from a cohort of children of African and Asian ancestry. A salient feature of the portal is its unique ability to capture epigenomic disruptions and complex oligogenic interactions in visualized regulatory pathways, thus advancing the frontier of disease etiology through convenient translation of computational signals into biological interpretations.

bioinformatics↗

bioRxiv2026

Thille, a chromosome-level type B avocado genome, and the structural and allelic variation at candidate flowering-type loci

Avocado (Persea americana Mill.) is heterodichogamous: each flower opens first as female and then as male, and cultivars fall into two complementary flowering types, A and B, determined by the transcription factor SDMYB, whose dominant allele confers type A. Avocado genomes have so far come from type A cultivars. Here we report a chromosome-level genome of Thille, a type B cultivar used in breeding. From 72.2 Gb of PacBio HiFi reads (81x coverage) and Omni-C data, the assembly places 859.8 Mb, 96% of the expected 896 Mb genome, in 12 chromosomes with an NG50 of 84.5 Mb, a consensus quality of QV 69.95, and 97.3% complete BUSCO genes; repeats occupy 64.0% of the assembly, and 35,386 protein-coding genes were predicted. We compared Thille with the type A cultivars Hass and Puebla, a predominantly Guatemalan hybrid, and with a West Indian (WI) accession, a Lowland botanical group variety of unreported flowering type. The assemblies differ by large rearrangements, including an 18.8 Mb inversion on chromosome 12 specific to Hass. Using phased reads and haplotype assemblies, we reconstructed the alleles of candidate flowering genes from a type A versus type B Fst scan. Both WI haplotypes carry the recessive SDMYB allele found in Thille; based on this study and the previous study of SDMYB, we predict the WI accession to be type B. Six genes, including SDMYB, carry an allele shared by all three type A cultivars and absent from Thille and WI. The genome and HiFi reads are available under BioProject PRJNA1142556.

genomics↗

bioRxiv2026

LigRNA: High-accuracy prediction of RNA-ligand binding sites via dynamic chemical complementarity and language model encoding

RNA-binding small molecules represent a validated therapeutic modality, yet pinpointing their exact RNA binding sites remains critical for mechanistic understanding and drug optimization. Experimental methods, while precise, are costly and low-throughput, necessitating robust computational alternatives. Approaches based on static feature concatenation may overlook input-dependent relationships between RNA residues and ligand functional groups. Here we present LigRNA, a graph neural network framework that predicts RNA-ligand binding sites through joint cross-modal encoding of both molecules. LigRNA integrates structure-guided language model embeddings with physicochemical features-solvent-accessible surface area and secondary structure types, to construct comprehensive RNA representations. Ligands are encoded as attributed molecular graphs via graph attention networks, preserving atom-level chemical topology rather than compressing molecules into fixed fingerprints. A cross-attention mechanism then enables dynamic, ligand-dependent modulation of RNA nucleotide attention, capturing context-specific interaction patterns. Benchmarked on TE9 and TE18 datasets, LigRNA achieves F1 scores of 0.73 and 0.58, improving on GATRsite by 7.4% and 18.4%, respectively. Ablation studies identify the RNA residual encoder as the most consistent contributor across the two benchmarks. The source code is freely available at https://github.com/WillowWang0216/LigRNA.

bioinformatics↗

bioRxiv2026

Bayesian phylogenetics with incomplete lineage tracing data

Single-cell lineage tracing is rapidly emerging as a powerful method to track the dynamics of cell populations through time. Specifically, CRISPR-Cas9-based dynamic lineage tracing methods generate high-resolution data with the potential to investigate increasingly complex biological processes. However, single-cell readouts are inherently lossy, resulting in significant sparsity in lineage barcode alignments. Here, we present a mechanistic model of barcode loss implemented in the Bayesian framework BEAST 2, enabling phylogenetic inference from sparse datasets without the need for data filtering. Through simulations, we find that incorporating a mechanistic model of loss improves accuracy across all estimates in phylogenetic analyses by enabling previously unusable data to contribute to the inference. We further demonstrate the model's utility across two datasets: one from a monoclonal cell culture and another from murine gastruloids. Consistent with our simulation findings, applying our model to these datasets recovers higher growth rates than workflows relying on standard data filtering, confirming that such filtering can lead to an underestimation of population expansion. Crucially, we demonstrate that our framework enables inference even from datasets whose sparsity previously prevented analysis, providing a robust foundation for extracting biological insights from lineage tracing experiments.

bioinformatics↗

bioRxiv2026

A Novel Role for FSTL-1 in Hematopoietic Stem Cell Homeostasis and Post-injury Regeneration

Background: The ability to repopulate all lineages of blood cells from a single hematopoietic stem cell (HSC) requires a constant balancing between maintenance of quiescence/self-renewal and the need for differentiation and adoption of specific lineage phenotypes. A classical interpretation suggests that during homeostasis, long- and then short-term HSCs differentiate into multipotent progenitors (MPPs), which then lack self-renewal capacity but can still differentiate into all downstream lineages. While much is known about the intrinsic and extrinsic regulators that promote HSC homeostasis, less is known about factors which influence HSC behavior following significant bone marrow (BM) injury, such as sublethal irradiation (SLI). Methods: Conditional knock-out of follistatin-like 1 (FSTL-1) was achieved by breeding mice with floxed Fstl1 sites to mice expressing CreERT2 under control of the ROSA locus, followed by systemic tamoxifen administration. ELISA and RT-PCR quantitated protein and RNA level loss of FSTL-1, respectively. HSC populations were assessed by flow cytometry under multiple conditions. Sublethal irradiation induced BM injury and blocking polyclonal FSTL-1 antibodies were used to recapitulate results seen with genetic ablation. Finally, single cell RNA sequencing defined both cell-specific expression of Fstl1 within the BM compartment, but also identified transcripts and pathways upregulated in the absence of FSTL-1. Results: These studies delineate a novel role for FSTL-1 in regulating HSC biology. In addition to selective expression of Fstl1 within HSCs, genetic deletion of Fstl1 increases Lineage negative;Sca-1+c-Kit+ (LSK) cell number and alters HSC homeostasis. These findings are further amplified in the BM in the context of recovery from sublethal irradiation. Importantly, the post-irradiation increase in BM cellularity seen with Fstl1 deletion is replicated by treatment with anti-FSTL-1 polyclonal antibodies. Finally, single cell RNA sequencing reveals distinct Fstl1 expression in specific LSK subpopulations, including HSCs and proliferating cells, and identifies a novel relationship between decreased FSTL-1 levels and enrichment of canonical metabolic pathways including oxidative phosphorylation, fatty acid metabolism, and glycolysis. Conclusions: Taken together, these results highlight a novel role for FSTL-1 in promoting HSC homeostasis. They also unlock an innovative way to promote HSPC recovery following BM injury, knowledge predicted to be of significant therapeutic value.

developmental biology↗

bioRxiv2026

The cleaved C-terminal domain of GmERS1-1 modulates cell cycle via GmACR1

Ethylene signaling orchestrates plant development and stress adaptation, yet how post-translational modifications of its receptors coordinate growth regulation remains unresolved. Here, we uncover a proteolytic processing mechanism of the soybean ethylene receptor GmERS1-1 that directly gates cell cycle progression. The GmERS1-1 mutants exhibit elevated yield under field conditions, whereas overexpression suppresses growth and hypersensitizes plants to ethylene. Ethylene triggers nuclear translocation of C-terminal domain (GmERS1-1-CEND), which is indispensable for receptor function. Mechanistically, GmERS1-1-CEND scaffolds a trimeric complex with GmACR1 and GmCDK7, enforcing G2/M phase arrest, thereby decoupling cell division from canonical ethylene transcriptional responses. Strikingly, ethylene-induced cell cycle blockade during apple fruit maturation mirrors this pathway, suggesting deep conservation across angiosperms. Our work defines a receptor processing-dependent signaling axis that directly interlinks phytohormone perception with cell cycle control, proposing tunable targets (e.g., GmERS1-1 cleavage efficiency) for engineering crop architecture and productivity.

plant biology↗

bioRxiv2026

A Single-cell Spatiotemporal Atlas Encoding Age-dependent Evolution of the Ischemic Penumbra

Aging is the predominant risk factor for stroke and a major driver of poor neurological recovery. Although the ischemic penumbra represents a key therapeutic target, its age-dependent molecular landscape remains poorly understood. Here, we generated a spatiotemporal transcriptomic atlas of the post-stroke penumbra in young (3-4 months) and aged (19-20 months) mice at acute (day 3) and chronic (day 14) stages following transient focal cerebral ischemia. Integrating spatial transcriptomics with dissociated single-cell RNA sequencing revealed a persistent transcriptomic penumbra (TP) that remains detectable for at least 14 days after stroke in both age groups, far beyond the window suggested by conventional imaging modalities. Aging profoundly altered TP organization, resulting in dysregulated energy metabolism, impaired neurovascular repair, diminished pro-reparative cell-cell communication, and extensive remodeling of transcriptional regulatory networks. Using this atlas, we further identified regulatory hub genes whose predicted perturbation could simultaneously counteract multiple age-associated pathological pathways. These data define the molecular architecture of the aging post-stroke penumbra and provide a publicly accessible framework for mechanistic discovery and therapeutic target prioritization aimed at improving recovery after stroke.

neuroscience↗

bioRxiv2026

Single-Cell Indel Detection Enhances Genetic Ancestry and Cellular Lineage Analysis

Small insertions and deletions (Indels) provide critical information for cancer genomics and clonal evolution, yet their detection from single-cell sequencing (SCS) such as scRNA-seq and scATAC-seq remains challenging due to sparse coverage, alignment artifacts, and RNA editing. Here, we present Monopogen-Indel, a bioinformatics framework for accurate germline and somatic Indel detection through haplotype-aware variant calling, dynamic template matching in repetitive regions, and cell-population- based allele segregation analysis. We validated germline Indel detection in human retina snRNA-seq with matched bulk whole genome sequencing (WGS). Monopogen-Indel detected 41,000-45,000 germline Indels per sample, with >70% precision and >90% genotyping accuracy. Using 65 heart left ventricle snATAC-seq samples, indel-based global ancestry inference segregated genetic ancestry comparably to SNVs, establishing indels as an independent marker of genetic diversity in SCS. In scRNA-seq from 43,717 cells across four anatomic sites of a patient with high grade serous ovarian cancer (HGSOC), Monopogen- Indel identified ~50,000 germline Indels per sample at 86% WGS-validated precision and an average of 1,040 de novo Indels per sample. Approximately 50% of de novo Indels reflected biological sources, including variants WGS variants, RNA editing, and cell-type-specific patterns. Somatic SNVs were correctly restricted to CD45- cells, indicating high specificity in delineating somatic from germline variants. In summary, Monopogen-indel is the first framework dedicated to indel detection from SCS and expands the utility of existing single-cell data for population genetics and cancer evolution. The module is integrated into Monopogen repository https://github.com/KChen-lab/Monopogen.

genomics↗

bioRxiv2026

Brain Controllability and Control Energy in Gray-White Matter Fusion Network

Objective: Brain network controllability provides a framework for understanding how structural organization shapes brain dynamics, yet current models mainly rely on white-matter connectivity and may overlook the contribution of gray-matter architecture. Approach: We constructed a fusion network combining diffusion tensor imaging-derived white-matter connectivity with gray-matter morphological similarity and investigated its controllability, biological associations, heritability, phenotype prediction, and control energy. Main results: Controllability derived from the fusion network preserved key topological properties of the white-matter network and was associated with neurotransmitter systems and cerebral metabolism. Compared with the white-matter connectivity-based network, fusion-based controllability showed a systematic shift toward higher heritability, improved prediction of several individual characteristics and cognitive functions, and lower modeled control energy for activating resting-state networks. Significance: These findings suggest that incorporating gray-matter morphological information into a DTI-supported network provides a complementary structural representation for studying brain network controllability and state transitions. The lower control energy represents a model-derived transition cost and should not be interpreted as a direct measure of physiological energy expenditure.

neuroscience↗

bioRxiv2026

A Medicinal Chemistry-Centered Evaluation of AlphaFold 3 and Boltz-2 Across Diverse Binding Modalities

AlphaFold 3 (AF3) and Boltz-2 are state-of-the-art AI-based tools for biomolecular structure prediction, but whether their predictions provide useful guidance for lead optimization, SAR interpretation, and virtual screening remains insufficiently characterized. We benchmarked their performance using newly determined soluble epoxide hydrolase co-crystal structures and matched activity data together with a curated post-training-cutoff dataset spanning kinases, allosteric modulators, covalent systems, PROTACs, molecular glues, fragments, membrane proteins, RNA binders, and activity-cliff pairs. Both models recovered canonical orthosteric enzyme and kinase complexes, including key DFG/C conformational states, whereas allosteric, membrane-protein, and induced-proximity complexes remained challenging. Pharmacophore RMSD was often lower than overall ligand RMSD, indicating preservation of key recognition features despite imperfect whole-ligand alignment. AF3 minPAE correlated with pose accuracy, and very low minPAE values (<0.85 A) were strongly enriched for accurate poses. Model confidence scores were not associated with experimental activity, whereas Boltz-2 predicted affinity captured relative activity trends and distinguished the activity-cliff pair, although its performance varied across ligand series.

biochemistry↗

bioRxiv2026

SOX9-mediated G1 elongation confers reserve stem cell-associated injury resistance in human intestinal stem cells

Background & Aims Dynamic cell cycle control is critical for intestinal crypt maintenance and injury responses, yet genetic regulators driving these changes remain poorly defined. As reserve intestinal stem cells (rISCs) are often considered to be slowly-cycling and can resist replication-dependent injury, factors that restrain proliferation may confer cytoprotection. Here, we define SOX9 as a regulator of intestinal stem cell (ISC) cycling and injury resistance. Methods Primary human ISCs were engineered to tune SOX9 levels, visualize cell cycle state, and manipulate cell cycle regulators. Using this system, we tested how SOX9 dosage impacts stemness, differentiation, proliferative recovery after SOX9 washout, and survival after 5-FU-mediated injury. Transcriptional analyses identified candidate links between SOX9 levels and cell cycle control, which were functionally tested using inducible INK4A (CDKN2A) and Cyclin D2 (CCND2) ISC lines. Results SOX9 induction lengthens the cell cycle in a dose-dependent manner largely by elongating G1 phase through the INK4A-Rb pathway. The effects of high SOX9 levels repressing proliferation and stem cell activity are reversible. SOX9 induction protects against 5-FU toxicity. This protection is mimicked by INK4A overexpression or pharmacological G1 phase arrest and repressed by CCND2 induction. Conclusions These findings identify SOX9-mediated G1 elongation as a reversible cytoprotective program that confers key functional properties associated with rISCs: proliferative restraint, retained stem cell potential, and resistance to replication-dependent injury. This positions G1 length as a potential determinant of which crypt cells survive injury to act as reserve stem cells.

cell biology↗

bioRxiv2026

ApoE4 Promotes Thrombosis via Endothelial Cell ApoER2 and PP2A Activation

Background: APOE4, the variant of apolipoprotein E carried by 25% of individuals, is a common genetic risk factor for cardiovascular disease (CVD). Although ApoE classically participates in lipid transport, APOE4-associated risk goes beyond impact on circulating lipids. Life-threatening CVD events including myocardial infarction and stroke are driven by atherogenesis and thrombosis. In mice ApoE4 increases atherosclerosis severity, but whether other major drivers of CVD events are influenced by ApoE4 is unknown. Methods: GWAS data for venous thromboembolism (VTE) were analyzed. In humanized APOE3 (hE3) and APOE4 (hE4) mice, thrombosis was assessed by intravital microscopy (IVM) in the mesenteric microcirculation and by inferior vena cava (IVC) partial ligation. Actions of ApoE3 versus ApoE4 on endothelial cells (EC) and their underpinnings were studied in cultured human and mouse aortic EC, interrogating interactomes with immunoprecipitation-mass spectrometry and quantifying the secretion of Von Willebrand Factor (vWF), a critical initiator of thrombosis. Single cell transcriptomics datasets were queried do localize endothelial cell gene expression. Results: GWAS showed that APOE4 is associated with increased VTE risk, and whereas plasma lipids were similar, both microvascular and venous thrombosis were markedly increased in hE4 compared to hE3 mice. In cultured EC, whereas ApoE3 attenuated vWF secretion, it was enhanced by ApoE4, and both processes were mediated by ApoE receptor 2 (ApoER2). ApoE4, but not ApoE3, suppressed VEGF eNOS activation and NO production by causing the recruitment of the protein phosphatase 2A (PP2A) catalytic subunit to ApoER2 and the activation of PP2A. PP2A deletion prevented ApoE4-induced eNOS antagonism and vWF secretion by preserving Akt activation, and the NO donor spermine NONOate negated apoE4 stimulation of vWF secretion. PP2A activity was increased in hE4 aortas and IVC, and EC ApoER2 deletion or pharmacologic PP2A inhibition fully prevented exaggerated thrombosis in hE4 mice. In human great saphenous vein ApoER2 is primarily expressed in valvular endothelium. Conclusions: APOE4 is a risk allele for thrombosis, and ApoE4 is prothrombotic in microvasculature and veins in mice. Mechanistically, the ApoE4-EC ApoER2 tandem enhances vWF secretion by recruiting and activating PP2A and antagonizing eNOS, resulting in exaggerated thrombosis. In human veins ApoER2 is expressed in valvular endothelium, which is the most common site of initiation of venous thrombosis. Targeting these processes may afford protection from both primary thrombotic disorders like VTE and acute CVD events such as myocardial infarction and stroke in 25% of the population.

pathology↗

bioRxiv2026

Reprogramming VHL with molecular glues enables selective degradation of caspase-2

Molecular glue degraders (MGDs) reprogram E3 ligases to eliminate neosubstrates, yet their application has largely been confined to CRBN. Here, we identify caspase-2 as a new neosubstrate for von Hippel-Lindau (VHL), expanding the scope of VHL-based MGDs. Guided by a focused VHL ligand library design, we employed TurboID-based proximity labeling to discover stereoisomeric compounds (dCASP2-1 and dCASP2-2) that selectively recruit caspase-2 to VHL and promote its ubiquitin-proteasome system-dependent degradation. Further structure-activity relationship (SAR) studies yielded dCASP2-3 and dCASP2-4, which enhanced degradation potency (by 622-fold relative to dCASP2-1) and abolished enantioselectivity. Mechanistic mapping localized the degrader-induced interface to a two-helix region of the caspase-2 CARD domain, with residues H33, P34, and D100 essential for VHL engagement. Degron-guided computational modeling of the VHL/MGD/caspase-2 ternary complex provided structural insight into neosubstrate recognition. Together, we report the development of VHL molecular glues that selectively and potently degrade caspase-2, offering chemical probes to interrogate its functions in apoptosis and stress responses, while broadening the substrate landscape of VHL-based MGDs.

biochemistry↗

bioRxiv2026

Functional and evolutionary insights into the emerging tet(X4)-carrying non-O1/O139 Vibrio cholerae from retail pork

The tigecycline resistance gene tet(X4) is prevalent in Enterobacteriaceae, particularly in Escherichia coli. To our knowledge, no study has reported the dissemination dynamics of tet(X4) in Vibrio spp. Herein, we isolated and characterized a first tet(X4)-positive non-O1/O139 Vibrio cholerae isolate from retail pork. Genomic sequencing identified a novel tet(X4) variant in the V. cholerae chromosome, harboring a G568A nucleotide substitution that resulted in an Ala190Thr (A190T) amino acid substitution in Tet(X4). While this Tet(X4)-A190T variant conferred lower phenotypic resistance to tetracyclines (including tigecycline) than the wild-type Tet(X4), its overall catalytic efficiency against these antibiotics was paradoxically enhanced despite a reduced substrate affinity. Genomic comparisons revealed that two copies of ISCR2 flanked the variant gene, and the structure was ISCR2-hp-hp-abh-tet(X4)G568A -ISCR2, which is highly homologous to the reported E. coli plasmids carrying tet(X4). In addition, it confirmed the presence of an ISCR2-mediated circular intermediate, proving this modules capacity for horizontal transfer of the tet(X4)G568A variant. Furthermore, the ISCR2-tet(X4) genetic structure carrying the G568A substitution was integrated within a chimeric SXT/R391-like integrative and conjugative element (ICE), which is also serving as a vehicle for genetic dissemination. As per our knowledge, this is the first report on the emergence of SXT/R391-like ICE carrying tet(X4) in Vibrio strains. Our finding demonstrates that the clinically relevant tigecycline resistance gene tet(X4), previously confined mainly to Enterobacterales from humans and livestock, is now actively spreading into environmental Vibrio populations. This cross-species transfer highlights a previously underappreciated ecological and public health concern in aquatic ecosystems.

microbiology↗

bioRxiv2026

Coronary Artery Disease Transcriptomics Reveals Two Drivers of the Endothelial Cell SR-BI Expression and LDL Transport that Underlie Atherosclerosis

Atherosclerosis is initiated by circulating low-density lipoprotein (LDL) cholesterol transfer into the artery wall, which is mediated by scavenger receptor class B, type I (SR-BI) in endothelial cells(1). Employing single-cell RNA sequencing in human coronary artery disease (CAD) samples, here we show that endothelial SR-BI expression is increased in atheroma, and in endothelial cells with a transcript signature indicative of responding to disturbed blood flow. In vivo in mice hypercholesterolemia and disturbed blood flow independently upregulate endothelial SR-BI; the flow-related upregulation initiates endothelial cell LDL uptake and atherogenesis. Guided by transcription factor networks, it is revealed that HIF-1 binding to human Scarb1 Intron 1 governs endothelial SR-BI transcription, and in mice HIF-1 drives hypercholesterolemia-related SR-BI upregulation and artery LDL uptake. Thus, the two major instigators of atherosclerotic lesion formation, hypercholesterolemia and disturbed blood flow, both upregulate endothelial SR-BI to drive the LDL transport that underlies the disorder. Targeting the processes regulating endothelial SR-BI potentially represents a new therapeutic strategy against CAD.

cell biology↗

bioRxiv2026

Bioorthogonal Tethering of FGF18 to Annealed Microgel Scaffolds Enhances Cartilage Repair

Articular cartilage damage often progresses to osteoarthritis (OA), a degenerative joint disease characterized by chronic pain, limited mobility, and reduced quality of life. Tissue engineering approaches using poly (ethylene glycol) (PEG)-based hydrogels offer tunable mechanical properties and bioactive functionalization, yet the influence of surface charge on cartilage regeneration remains underexplored. Moreover, recombinant fibroblast growth factor 18 (FGF18) has successfully improved cartilage tissue thickness in clinical trials, but required high dosages and recurring injections may limit compliance. Here, we developed a granular microgel-based platform with bioorthogonally tethered FGF18 to evaluate the interplay of microgel surface charge and growth factor presentation on chondrogenesis. Azide groups were incorporated onto the microgel surfaces to enable site specific FGF18 conjugation across microgel scaffolds with distinct surface charges. When seeded with mesenchymal stromal cells, microgel scaffolds functionalized with FGF18 outperformed their unmodified counterparts, evidenced by higher GAG content, collagen content, and compressive modulus. In a murine microfracture model, anionic and zwitterionic microgel scaffolds tethered with FGF18 increased cartilage regeneration compared to nonionic microgels. We detected increased collagen II content within defects treated with tethered FGF18 microgel scaffolds. This work demonstrates the role of surface charge and growth factor presentation in directing cell behavior and tissue repair, advancing the design of biomaterials for cartilage regeneration. HIGHLIGHTSO_LICovalent tethering of FGF18 to microgel surface enables localized bioactivity C_LIO_LIFGF18 tethered microgel scaffolds enhance extracellular matrix deposition and chondrogenic differentiation of murine mesenchymal stromal cells in vitro C_LIO_LILocalized FGF18 presentation improves cartilage tissue formation and mechanical properties in vivo, with anionic and zwitterionic microgel scaffolds outperforming nonionic scaffolds C_LIO_LIFGF18 presentation is a more potent stimulus than microgel surface charge for cartilage regeneration C_LI

bioengineering↗