CX3CL1 and CX3CR1 Expressing Tendon Cells - A novel Immune Cell Population in the Tendon Core

Lehner, C.; Spitzer, G.; Gehwolf, R.; Wagner, A.; Weissenbacher, N.; Deininger, C.; Emmanuel, K.; Wichlas, F.; Tempfer, H.; Traweger, A.

doi:10.1101/693317

bioRxiv · 10.1101/693317

CX3CL1 and CX3CR1 Expressing Tendon Cells - A novel Immune Cell Population in the Tendon Core

Lehner, C.·Spitzer, G.·Gehwolf, R.·Wagner, A.·Weissenbacher, N.·Deininger, C.·Emmanuel, K.·Wichlas, F.·Tempfer, H.·Traweger, A.

View original source ↗Export metadata ↓

Abstract

Tendon disorders frequently occur and recent evidence has clearly implicated the presence of immune cells and inflammatory events during early tendinopathy. However, the origin and properties of these cells remain poorly defined. Therefore, the aim of this study was to determine the presence of myleoid cells in healthy rodent and human tendon tissue and to characterize them. Using various transgenic reporter mouse models, we demonstrate the presence of tendon cells in the dense matrix of the tendon core expressing the fractalkine (Fkn) receptor CX3CR1 and its cognate ligand CX3CL1/Fkn. Pro-inflammatory stimulation of 3D tendon-like constructs in vitro resulted in a significant increase in the expression of IL-1{beta}, IL-6, Mmp3, Mmp9, Cx3cl1, and epiregulin which has been reported to contribute to inflammation, wound healing, and tissue repair. Furthermore, we demonstrate that inhibition of the fractalkine receptor blocked tendon cell migration in vitro and show the presence of CX3CR1/CX3CL1/EREG expressing cells in healthy human tendons. Taken together, we demonstrate the presence of CX3CL1+/CX3CR1+ \"tenophages\" within the healthy tendon proper potentially fulfilling surveillance functions in tendons.\n\nSummary StatementHere, we demonstrate the presence of a macrophage-like, CX3CL1/CX3CR1-expressing cell population within the healthy tendon proper potentially fulfilling a surveillance function.

Source connections

Published article ↗

Explore related subjects

cell biology Preprint

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Lehner, C., Spitzer, G., Gehwolf, R., Wagner, A., Weissenbacher, N., Deininger, C., Emmanuel, K., Wichlas, F., Tempfer, H., Traweger, A.. 2019-07-04. CX3CL1 and CX3CR1 Expressing Tendon Cells - A novel Immune Cell Population in the Tendon Core. https://doi.org/10.1101/693317

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

High-content screening identifies FDA-approved activators of mitophagy

Mitochondrial diseases are highly heterogeneous disorders caused by defects in oxidative phosphorylation, for which only limited therapeutic options are available. The elimination of dysfunctional mitochondria via mitophagy activation is an attractive strategy to treat several mitochondrial diseases, irrespective of the underlying genetic defect. To identify pharmacological activators of this pathway, we performed a high-content screening of 1,971 FDA-approved compounds using cellular reporters of TFEB nuclear translocation and mitophagy. This screening identified 294 compounds that promoted TFEB translocation, nine of which increased the number of mitolysosomes without compromising cell viability or damaging mitochondria. Among the selected compounds, Meptazinol and Ponatinib emerged as the top-ranked mitophagy inducers in fibroblasts from patients with complex I and IV deficiency, respectively, and were prioritised for further characterisation. However, they did not rescue the bioenergetic defect, suggesting that the stimulation of mitophagy per se is not sufficient to ameliorate the OXPHOS defect in mitochondrial diseases. Overall, our findings establish a scalable platform for the identification of pharmacological activators of TFEB and identify candidate compounds for therapeutic modulation of mitophagy.

cell biology↗

bioRxiv2026

A LOV-domain photoreceptor mediates phototaxis in brown algae

Phototaxis enables motile cells to navigate light environments and plays a critical role in survival and reproduction across diverse eukaryotic lineages. This ability has evolved independently through distinct photoreceptor systems. Yet, the molecular mechanisms underlying phototaxis remain poorly understood in many major eukaryotic lineages, including stramenopiles. Here, combining functional genetics, cell biology and evolutionary analyses, we identify Helmchrome (HELM), a LOV-domain protein required for phototaxis in the brown alga Ectocarpus. HELM localizes to the posterior flagellum and is responsible for the characteristic flavin-associated fluorescence of brown algal gametes. Loss of HELM abolishes phototactic accumulation and directional orientation without affecting basal motility or fertilization, demonstrating its specific requirement for light-directed movement. Phylogenetic analyses reveal that HELM-like proteins are distributed across diverse stramenopile lineages and that their domain architecture evolved through repeated duplication of an ancestral RGS-LOV module. Our findings identify HELM as a key component of the light-sensing machinery in brown algae, provide a molecular explanation for the long-standing observation of flagellar flavin fluorescence, and reveal a distinct phototaxis system that expands the known diversity of eukaryotic light-sensing mechanisms.

cell biology↗

bioRxiv2026

A distinct chondrogenic progenitor population from human umbilical cord derived mesenchymal stromal cells for osteoarthritis therapy

Stem cell-based cartilage regeneration remains constrained by functional heterogeneity and phenotypic drift in conventional cell sources, compromising durable structural repair. Human umbilical cord-derived mesenchymal stromal cells (UC-MSCs) represent an accessible, off-the-shelf cell source; however, their broad clinical utility is hampered by cellular heterogeneity, leaving the key chondrogenic subpopulation responsible for cartilage repair unresolved. By integrating single-cell transcriptomics with functional assays, we identified and prospectively isolated a distinct, highly expandable subpopulation of skeletal stem cell-like progenitors (U-CPCs) from the human umbilical cord, establishing an extra-skeletal cell source uniquely primed for joint restoration. Single-cell transcriptomics reveal their inherent regulatory landscape, uncovering a distinct transcriptional state uniquely primed for chondrogenesis. In comparison with conventional stem cells and other tissue-derived SSC-like populations (from umbilical cord, bone marrow, adipose tissue, and dental pulp), U-CPCs exhibit a markedly enhanced chondrogenic capacity. In both a mouse cartilage injury model and a rat osteoarthritis model, the administration of U-CPCs effectively mitigates joint degeneration and drives the restoration of a structurally sound, hyaline-like matrix. Mechanistically, U-CPCs secrete extracellular vesicles enriched with microRNA Let-7a-5p, which specifically modulates DUSP7/MAPK/ERK signaling in recipient chondrocytes, thereby restoring extracellular matrix homeostasis and promoting cartilage repair. By characterizing these specialized extra-skeletal progenitors and elucidating both their intrinsic chondrogenic priming and paracrine regulation of host tissue, this study establishes U-CPCs as a robust, lineage-restricted cellular source for osteoarthritis therapy.

cell biology↗