Autocrine IL-6 drives cell and extracellular matrix anisotropy in scar fibroblasts

Characterisation and correction of polarisation effects in fluorescently labelled fibres

Many biological structures take the form of fibres and filaments, and quantitative analysis of fibre organisation is important for understanding their functions in both normal physiological conditions and disease. In order to visualise these structures, fibres can be fluorescently labelled and imaged, with specialised image analysis methods available for quantifying the degree and strength of fibre alignment. Here we show that fluorescently labelled fibres can display polarised emission, with the strength of this effect varying depending on structure and fluorophore identity. This can bias automated analysis of fibre alignment and mask the true underlying structural organisation. We present a method for quantifying and correcting these polarisation effects without requiring polarisation-resolved microscopy and demonstrate its efficacy when applied to images of fluorescently labelled collagen gels, allowing for more reliable characterisation of fibre microarchitecture.

Skin organoid transplantation promotes tissue repair with scarless in frostbite

Frostbite is the most common cold injury and is caused by both immediate cold-induced cell death and the gradual development of localized inflammation and tissue ischemia. Delayed healing of frostbite often leads to scar formation, which not only causes psychological distress but also tends to result in the development of secondary malignant tumors. Therefore, a rapid healing method for frostbite wounds is urgently needed. Herein, we used a mouse skin model of frostbite injury to evaluate the recovery process after frostbite. Moreover, single-cell transcriptomics was used to determine the patterns of changes in monocytes, macrophages, epidermal cells, and fibroblasts during frostbite. Most importantly, human-induced pluripotent stem cell (hiPSC)-derived skin organoids combined with gelatin-hydrogel were constructed for the treatment of frostbite. The results showed that skin organoid treatment significantly accelerated wound healing by reducing early inflammation after frostbite and increasing the proportions of epidermal stem cells. Moreover, in the later stage of wound healing, skin organoids reduced the overall proportions of fibroblasts, significantly reduced fibroblast-to-myofibroblast transition by regulating the integrin α5β1-FAK pathway, and remodeled the extracellular matrix (ECM) through degradation and reassembly mechanisms, facilitating the restoration of physiological ECM and reducing the abundance of ECM associated with abnormal scar formation. These results highlight the potential application of organoids for promoting the reversal of frostbite-related injury and the recovery of skin functions. This study provides a new therapeutic alternative for patients suffering from disfigurement and skin dysfunction caused by frostbite.

The role of macrophages in hypertrophic scarring: molecular to therapeutic insights

Hypertrophic Scar (HS) is a common fibrotic disease of the skin, usually caused by injury to the deep dermis due to trauma, burns, or surgical injury. The main feature of HS is the thickening and hardening of the skin, often accompanied by itching and pain, which seriously affects the patient's quality of life. Macrophages are involved in all stages of HS genesis through phenotypic changes. M1-type macrophages primarily function in the early inflammatory phase by secreting pro-inflammatory factors, while M2-type macrophages actively contribute to tissue repair and fibrosis. Despite advances in understanding HS pathogenesis, the precise mechanisms linking macrophage phenotypic changes to fibrosis remain incompletely elucidated. This review addresses these gaps by discussing the pathological mechanisms of HS formation, the phenotypic changes of macrophages at different stages of HS formation, and the pathways through which macrophages influence HS progression. Furthermore, emerging technologies for HS treatment and novel therapeutic strategies targeting macrophages are highlighted, offering potential avenues for improved prevention and treatment of HS.

Chlorpheniramine maleate exerts an anti-keloid activity by regulation of IL-6/JAK1/STAT3 signaling pathway

Keloids are abnormal scars formed due to fibroblast dysfunction and excessively deposited extracellular matrix (ECM). Despite the unclear process leading to the occurrence of keloids, several studies have demonstrated that histamine and its H1 receptor can effectively regulate fibroblast functions, contributing to keloid formation. Chlorpheniramine maleate (CPM) as a first-generation H1 antihistamine has been widely applied in symptomatic treatment of allergic conditions but its effects on keloids are unknown. This study holds the objective of exploring its effect on keloids. Cell Counting Kit-8 (CCK-8), apoptosis, cell cycle and migration assays were conducted to determine the effects of CPM on human keloid fibroblasts (KFs), with its therapeutic effect evaluated by constructing a keloid model in nude mice. RNA sequencing analysis, ELISA, western blotting and immunohistochemistry assisted in examining the anti-keloid mechanism of CPM. It was observed that CPM inhibited the proliferation and migration of KFs, promoted apoptosis of KFs, and blocked the G0/G1 phase of KFs. Moreover, local intralesional injection of CPM into nude mice keloid model significantly reduced keloid scars. According to RNA sequencing analysis, the gene expression of IL-6 and JAK-STAT signaling pathway were both negatively related in CPM group versus the control group. According to the in vivo and vitro experiment results, the anti-keloid activity of CPM was attributed to its inhibitory effect on the IL-6/JAK1/STAT3 signal pathway. In summary, CPM holds great potential for localized treatment of keloids.

Biomimetic Topological Micropattern Arrays Regulate the Heterogeneity of Cellular Fates in Lung Fibroblasts between Fibrosis and Invasion

Idiopathic pulmonary fibrosis (IPF) is characterized by persistent tissue injury, dysregulated wound healing, and extracellular matrix (ECM) deposition by myofibroblasts (MFs) through the fibroblast-to-myofibroblast transition (FMT). Implicit in the FMT process are changes in the ECM and cellular topology, but their relationship with the lung fibroblast phenotype has not been explored. We engineered topological mimetics of alignment cues (anisotropy/isotropy) using lung decellularized ECM micropattern arrays and investigated the effects of cellular topology on cellular fates in MRC-5 lung fibroblasts. We found that isotropic MRC-5 cells presented changes of the cytoskeleton, increased cell-cell adhesions and a multicellular architecture with increased overlap, changes in actin-myosin development, and enhanced focal adhesion and cell junction with random alignment. Besides, anisotropic fibroblasts were activated into a regular phenotype with an ECM remodeling profile. In contrast, isotropic fibroblasts developed a highly invasive phenotype expressing molecules, including CD274/programmed death-ligand 1 (PD-L1), cellular communication network factor 2 (CCN2)/connective tissue growth factor (CTGF), hyaluronan synthase 2 (HAS2), and semaphorin 7A (SEMA7A), but with downregulated matrix genes. Moreover, isotropic fibroblasts also showed higher expressions of Ki-67 and cyclin D1 (CCND1), resistance to apoptosis/senescence, and decreased autophagy. The topology regulated the cellular heterogeneity and resulted in positive feedback between changes in the cellular phenotype and the ECM structure, which may aggravate fibrosis and lead to a priming of malignant microenvironment during carcinogenesis. Using the versatile platform of micropattern array, we can not only visualize the interaction mechanism between cells and the ECM but also select potential clinical targets for diagnosis and therapeutics.

A Dynamical Analysis of the Alignment Mechanism Between Two Interacting Cells

In this work we analytically investigate the alignment mechanism of self-propelled ellipse-shaped cells in two spatial dimensions interacting via overlap avoidance. By considering a two-cell system and imposing certain symmetries, we obtain an analytically tractable dynamical system, which we mathematically analyse in detail. We find that for elongated cells there is a half-stable steady state corresponding to perfect alignment between the cells. Whether cells move towards this state (i.e., become perfectly aligned) or not is determined by where in state space the initial condition lies. We find that a separatrix splits the state space into two regions, which characterise these two different outcomes. We find that some self-propulsion is necessary to achieve perfect alignment, however too much self-propulsion hinders alignment. Analysing the effect of small amounts of self-propulsion offers an insight into the timescales at play when a trajectory is moving towards the point of perfect alignment. We find that the two cells initially move apart to avoid overlap over a fast timescale, and then the presence of self-propulsion causes them to move towards a configuration of perfect alignment over a much slower timescale. Overall, our analysis highlights how the interaction between self-propulsion and overlap avoidance is sufficient to generate alignment.

Derivation and simulation of a computational model of active cell populations: How overlap avoidance, deformability, cell-cell junctions and cytoskeletal forces affect alignment

Collective alignment of cell populations is a commonly observed phenomena in biology. An important example are aligning fibroblasts in healthy or scar tissue. In this work we derive and simulate a mechanistic agent-based model of the collective behaviour of actively moving and interacting cells, with a focus on understanding collective alignment. The derivation strategy is based on energy minimisation. The model ingredients are motivated by data on the behaviour of different populations of aligning fibroblasts and include: Self-propulsion, overlap avoidance, deformability, cell-cell junctions and cytoskeletal forces. We find that there is an optimal ratio of self-propulsion speed and overlap avoidance that maximises collective alignment. Further we find that deformability aids alignment, and that cell-cell junctions by themselves hinder alignment. However, if cytoskeletal forces are transmitted via cell-cell junctions we observe strong collective alignment over large spatial scales.

Imaging actin organisation and dynamics in 3D

The actin cytoskeleton plays a critical role in cell architecture and the control of fundamental processes including cell division, migration and survival. The dynamics and organisation of F-actin have been widely studied in a breadth of cell types on classical two-dimensional (2D) surfaces. Recent advances in optical microscopy have enabled interrogation of these cytoskeletal networks in cells within three-dimensional (3D) scaffolds, tissues and in vivo. Emerging studies indicate that the dimensionality experienced by cells has a profound impact on the structure and function of the cytoskeleton, with cells in 3D environments exhibiting cytoskeletal arrangements that differ to cells in 2D environments. However, the addition of a third (and fourth, with time) dimension leads to challenges in sample preparation, imaging and analysis, necessitating additional considerations to achieve the required signal-to-noise ratio and spatial and temporal resolution. Here, we summarise the current tools for imaging actin in a 3D context and highlight examples of the importance of this in understanding cytoskeletal biology and the challenges and opportunities in this domain.