Biology subjects

Horsley, V.

Publications and source records attributed to Horsley, V..

10 recordsLinked to original sources

bioRxiv2026

Loss of Sun2 ablates nuclear mechanosensing-driven extracellular matrix production and mitigates lung fibrosis

Fibrosis and pathological stiffening of tissue are driven by mechanical and biochemical signaling pathways. Here, we find that Sun2, an integral inner nuclear membrane component of Linker of Nucleoskeleton and Cytoskeleton (LINC) complexes, is up-regulated in the lung of patients suffering from fibrotic conditions and in fibroblasts during an injury-induced mouse model of lung fibrosis. Sun2 protein levels also increase in primary lung fibroblasts in a substrate stiffness-dependent manner. Sun2-/- primary lung fibroblasts respond to TGF{beta}, become contractile, and express a key marker of extracellular matrix-producing fibroblasts, Cthrc1. Consistent with this, Sun2 is dispensable for myofibroblast formation and repairing the alveolar barrier after bleomycin injury. Remarkably, however, fibrosis does not develop in bleomycin-treated Sun2-/- mouse lungs. This is explained by the requirement for Sun2 to up-regulate genes encoding extracellular matrix proteins. We therefore suggest that Sun2-containing LINC complexes contribute to a mechanical coincidence detection mechanism that acts in concert with canonical TGF{beta} signaling necessary for pathologic extracellular matrix protein production, representing a nuclear mechanosensing node for intervention in fibrotic diseases of the lung.

cell biology↗

bioRxiv2026

SUN2 mediates epigenetic remodeling to drive mechanotransduction during skin fibrosis

Fibrosis involves sustained changes in fibroblast gene expression, leading to excessive extracellular matrix (ECM) deposition and progressive tissue stiffening. Although matrix stiffness is a potent regulator of cell fate and transcription, it is not clear how nuclear mechanosensing contributes to fibrosis. Here, we define a central role for SUN2, a component of linker of nucleoskeleton and cytoskeleton (LINC) complexes, as a mediator of stiffness-dependent nuclear and chromatin responses during skin fibrosis. SUN2 transcripts are upregulated in dermal fibroblasts of patients with systemic sclerosis and Sun2 protein is elevated in fibrotic mouse skin. Nuclear size, A-type lamins and Sun2 are elevated in dermal fibroblasts plated on stiff substrates. Loss of Sun2 protects against bleomycin-induced skin fibrosis in vivo and abolishes stiffness-induced changes in nuclear size and fibrotic gene expression in vitro. Mechanistically, we identify three Sun2-dependent mechanosensitive chromatin states and show that mechanical induction of the histone methyltransferase Ezh2 requires Sun2. These findings define SUN2 as a nuclear mechanosensor that couples matrix stiffness to chromatin regulation and transcriptional programs that drive fibrosis, identifying it as a potential therapeutic target pathway in fibrotic disease.

cell biology↗

bioRxiv2024

Multiomics reveals age-dependent metabolic reprogramming of macrophages by wound bed niche secreted signals

The cellular metabolism of macrophages depends on tissue niches and can control macrophage inflammatory or resolving phenotypes. Yet, the identity of signals within tissue niches that control macrophage metabolism is not well understood. Here, using single-cell RNA sequencing of macrophages in early mouse wounds, we find that, rather than gene expression of canonical inflammatory or resolving polarization markers, metabolic gene expression defines distinct populations of early wound macrophages. Single-cell secretomics and transcriptomics identify inflammatory and resolving cytokines expressed by early wound macrophages, and we show that these signals drive metabolic inputs and mitochondrial metabolism in an age-dependent manner. We show that aging alters the metabolome of early wound macrophages and rewires their metabolism from mitochondria to glycolysis. We further show that macrophage-derived Chi3l3 and IGF-1 can induce metabolic inputs and mitochondrial mass/metabolism in aged and bone marrow-derived macrophages. Together, these findings reveal that macrophage-derived signals drive the mitochondrial metabolism of macrophages within early wounds in an age-dependent manner and have implications for inflammatory diseases, chronic injuries, and age-related inflammatory diseases. In BriefThis study reveals that macrophage subsets in early inflammatory stages of skin wound healing are defined by their metabolic profiles rather than polarization phenotype. Using single-cell secretomics, we establish key macrophage cytokines that comprise the in vivo wound niche and drive mitochondrial-based metabolism. Aging significantly alters macrophage heterogeneity and increases glycolytic metabolism, which can be restored to OxPHOS-based metabolism with young niche cytokines. These findings highlight the importance of the tissue niche in driving macrophage phenotypes, with implications for aging-related impairments in wound healing. HighlightsO_LISingle cell transcriptional analysis reveals that reveals that metabolic gene expression identifies distinct macrophage populations in early skin wounds. C_LIO_LISingle-cell secretomic data show that young macrophages contribute to the wound bed niche by secreting molecules such as IGF-1 and Chi3l3. C_LIO_LIOld wound macrophages display altered metabolomics, elevated glycolytic metabolism and glucose uptake, and reduced lipid uptake and mitochondrial mass/metabolism. C_LIO_LIChi3l3 but not IGF-1 secretion is altered in macrophages in an age dependent manner. C_LIO_LIChi3l3 can restore mitochondrial mass/metabolism in aged macrophages. C_LI

cell biology↗

bioRxiv2024

Transcriptional analysis of efferocytosis in mouse skin wounds

Defects in apoptotic cell clearance, or efferocytosis, can cause inflammatory diseases and prevent tissue repair due in part to inducing a pro-repair transcriptional program in phagocytic cells like macrophages. While the cellular machinery and metabolic pathways involved in efferocytosis have been characterized, the precise efferocytic response of macrophages is dependent on the identity and macromolecular cues of apoptotic cells, and the complex tissue microenvironment in which efferocytosis occurs. Here, we find that macrophages undergoing active efferocytosis in mid-stage mouse skin wounds in vivo display a pro-repair gene program, while efferocytosis of apoptotic skin fibroblasts in vitro also induces an inflammatory transcription response. These data provide a resource for understanding how the skin wound environment influences macrophage efferocytosis and will be useful for future investigations that define the role of efferocytosis during tissue repair.

cell biology↗

bioRxiv2023

Transcriptional heterogeneity in diabetic foot wounds

Wound repair requires the coordination of multiple cell types including immune cells and tissue resident cells to coordinate healing and return of tissue function. Diabetic foot ulceration is a type of chronic wound that impacts over 4 million patients in the US and over 7 million worldwide (Edmonds et al., 2021). Yet, the cellular and molecular mechanisms that go awry in these wounds are not fully understood. Here, by profiling chronic foot ulcers from non-diabetic (NDFUs) and diabetic (DFUs) patients using single-cell RNA sequencing, we find that DFUs display transcription changes that implicate reduced keratinocyte differentiation, altered fibroblast function and lineages, and defects in macrophage metabolism, inflammation, and ECM production compared to NDFUs. Furthermore, analysis of cellular interactions reveals major alterations in several signaling pathways that are altered in DFUs. These data provide a view of the mechanisms by which diabetes alters healing of foot ulcers and may provide therapeutic avenues for DFU treatments.

cell biology↗

bioRxiv2023

Apoptosis recognition receptors regulate skin tissue repair in mice

Apoptosis and clearance of apoptotic cells via efferocytosis are evolutionarily conserved processes that drive tissue repair. However, the mechanisms by which recognition and clearance of apoptotic cells regulate repair are not fully understood. Here, we use single-cell RNA sequencing to provide a map of the cellular dynamics during early inflammation in mouse skin wounds. We find that apoptotic pathways and efferocytosis receptors are elevated in fibroblasts and immune cells, including resident Lyve1+ macrophages, during inflammation. Interestingly, human diabetic foot wounds upregulate mRNAs for apoptotic genes and display increased and altered efferocytosis signaling via the receptor Axl. During early inflammation in mouse wounds, we detect upregulation of Axl in dendritic cells and fibroblasts via TLR3-independent mechanisms. Inhibition studies in vivo in mice reveal that Axl signaling is required for wound repair but is dispensable for efferocytosis. By contrast, inhibition of another efferocytosis receptor, Timd4, in mouse wounds decreases efferocytosis and abrogates wound repair. These data highlight the distinct mechanisms by which apoptotic cell detection coordinates tissue repair and provides potential therapeutic targets for chronic wounds in diabetic patients.

cell biology↗

bioRxiv2021

Single Cell Transcriptomic Landscape of Diabetic Foot Ulcers

To understand the diabetic wound healing microenvironment, we profiled 174,962 single cells from foot, forearm, and PBMCs using single-cell RNA sequencing (scRNASeq) approach. Our analysis shows enrichment of a unique population of fibroblasts overexpressing MMP1, MMP3, MMP11, HIF1A, CHI3L1, and TNFAIP6 genes and M1 macrophage polarization in the DFU patients with healing wounds. Further, scRNASeq of spatially separated samples from same patient and spatial transcriptomics (ST) revealed preferential localization of these healing associated fibroblasts toward deep wound/ulcer bed as compared to wound edge or non-wounded skin. ST also validated our findings of higher enrichment of M1 macrophages in healers and M2 macrophages in non-healers. Our analysis provides deep insights into the wound healing microenvironment, identifying cell types that could be critical in promoting DFU healing, and may inform novel therapeutic approaches for DFU treatment.

genomics↗

bioRxiv2021

Adipocyte lipolysis abrogates skin fibrosis in a Wnt/DPP4-dependent manner

Tissue fibrosis in many organs results from altered and excessive extracellular matrix (ECM) protein deposition 1. Concomitant with ECM expansion, resident lipid-filled cells including mature adipocytes are lost in human and mouse fibrosis2-5, yet the mechanisms that drive mature adipocyte lipid loss and their contribution to tissue fibrosis are unknown. Here, we identify an early, fibro-protective role of mature adipocyte lipolysis driven by Wnt signaling during fibrosis onset. Using chemical and genetic mouse models of skin fibrosis, we show that fibrotic stimuli induce and maintain lipolysis in mature dermal adipocytes. Loss of the lipolytic rate-limiting enzyme adipocyte triglyceride lipase (ATGL)6,7 in murine dermal adipocytes exacerbates bleomycin-induced fibrosis development. Adipocyte lipolysis is stimulated in the early stages of Wnt signaling-induced skin fibrosis and by Wnt agonists in vitro. Furthermore, deletion or inhibition of the Wnt target gene, CD26/Dipeptidyl peptidase 4 (DPP4) prevented Wnt-induced lipolysis and skin fibrosis in mice. Notably, DPP4 expression correlates with skin fibrosis severity in human patients. Thus, we propose that adipocyte-derived fatty acids and the Wnt-DPP4 axis act as essential regulators of ECM homeostasis within tissues and provide a therapeutic avenue to manipulate fibrosis.

cell biology↗

bioRxiv2020

The LINC complex transmits integrin-dependent tension to the nuclear lamina and represses epidermal differentiation

While the mechanisms by which chemical signals control cell fate have been well studied, how mechanical inputs impact cell fate decisions are not well understood. Here, using the well-defined system of keratinocyte differentiation in the skin, we examine whether and how direct force transmission to the nucleus regulates epidermal cell fate. Using a molecular biosensor, we find that tension on the nucleus through Linker of Nucleoskeleton and Cytoskeleton (LINC) complexes requires integrin engagement in undifferentiated epidermal stem cells, and is released during differentiation concomitant with decreased tension on A-type lamins. LINC complex ablation in mice reveals that LINC complexes are required to repress epidermal differentiation in vivo and in vitro and influence accessibility of epidermal differentiation genes, suggesting that force transduction from engaged integrins to the nucleus plays a role in maintaining keratinocyte progenitors. This work reveals a direct mechanotransduction pathway capable of relaying adhesion-specific signals to regulate cell fate.

cell biology↗

bioRxiv2019

Dynamic changes in innate immune and T cell function and composition at the nasal mucosa across the human lifespan

The very young and very old are at increased risk of serious infections, including pneumonia. This may relate to changes in the immune system as young children have limited immunological memory, while immunosenescence, inflammaging and a decreased pool of naive immune cells are described with advanced age. How the immune system changes with age at mucosal surfaces, from where infections frequently develop, is not very clear as access to human tissue samples is limited. Therefore, we aimed to assess the composition and activation state of the immune system at the human mucosa. Here, we profiled nasal immune cells from 207 individuals between 1 to 80 years old using flow cytometry. Neutrophil and monocyte functionality were measured using whole blood assays. Levels of thirty nasal cytokines were measured from nasal lining fluid. Nasopharyngeal colonization by Streptococcus pneumoniae was assessed using classical microbiology and associated with immune responses. We found that young children have a striking paucity of granulocytes at the nasal mucosa compared to adults. In addition, T cell numbers at the nasal mucosa decreased progressively with age and were almost absent in older adults. While nasopharyngeal colonization by Streptococcus pneumoniae was associated with elevated levels of inflammation it had a limited effect on nasal immune composition, including levels of monocytes and neutrophils. These results show that the immune system at the nasal mucosal surface changes drastically with age and provides explanations for the increased susceptibility to infections in young and old age.\n\nSignificance statementHow the immune system changes with age is an intensive area of research, but has been primarily studied in blood. However, blood poorly reflects the immune system at the mucosa, from where infections develop. This manuscript provides a first characterization of how the composition and function of the immune system in the upper respiratory tract changes with age, providing explanations for increased susceptibility to infection in the very young and old. Furthermore, by linking mucosal and systemic measurements with pneumococcal colonization, we observed that reduced monocyte and neutrophil responses associate with the increased burden of pneumococcal colonization in children. This study highlights the need to study the immune system also at other mucosal sites in the context of aging.

immunology↗