Delayed Collagen Production without Myofibroblast Formation Contributes to Reduced Scarring in Adult Skin Microwounds

In adult mammals, wound healing predominantly follows a fibrotic pathway, culminating in scar formation. However, cutaneous microwounds generated through fractional photothermolysis, a modality that produces a constellation of microthermal zones, exhibit a markedly different healing trajectory. Our study delineates the cellular attributes of these microthermal zones, underscoring a temporally limited, subclinical inflammatory milieu concomitant with rapid re-epithelialization within 24 hours. This wound closure is facilitated by the activation of genes associated with keratinocyte migration and differentiation. In contrast to macrothermal wounds, which predominantly heal through a robust myofibroblast-mediated collagen deposition, microthermal zones are characterized by absence of wound contraction and feature delayed collagen remodeling, initiating 5-6 weeks after injury. This distinct wound healing is characterized by a rapid re-epithelialization process and a muted inflammatory response, which collectively serve to mitigate excessive myofibroblast activation. Furthermore, we identify an initial reparative phase characterized by a heterogeneous extracellular matrix protein composition, which precedes the delayed collagen remodeling. These findings extend our understanding of cutaneous wound healing and may have significant implications for the optimization of therapeutic strategies aimed at mitigating scar formation.

Single-cell, single-nucleus, and spatial transcriptomics characterization of the immunological landscape in the healthy and PSC human liver

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is an immune-mediated cholestatic liver disease for which there is an unmet need to understand the cellular composition of the affected liver and how it underlies disease pathogenesis. We aimed to generate a comprehensive atlas of the PSC liver using multi-omic modalities and protein-based functional validation.

METHODS

We employed single-cell and single-nucleus RNA sequencing (47,156 cells and 23,000 nuclei) and spatial transcriptomics (one sample by 10x Visium and five samples with Nanostring GeoMx DSP) to profile the cellular ecosystem in 10 PSC livers. Transcriptomic profiles were compared to 24 neurologically deceased donor livers (107,542 cells) and spatial transcriptomics controls, as well as 18,240 cells and 20,202 nuclei from three PBC livers. Flow cytometry was performed to validate PSC-specific differences in immune cell phenotype and function.

RESULTS

PSC explants with parenchymal cirrhosis and prominent periductal fibrosis contained a population of cholangiocyte-like hepatocytes that were surrounded by diverse immune cell populations. PSC-associated biliary, mesenchymal, and endothelial populations expressed chemokine and cytokine transcripts involved in immune cell recruitment. Additionally, expanded CD4+ T cells and recruited myeloid populations in the PSC liver expressed the corresponding receptors to these chemokines and cytokines, suggesting potential recruitment. Tissue-resident macrophages, by contrast, were reduced in number and exhibited a dysfunctional and downregulated inflammatory response to lipopolysaccharide and interferon-γ stimulation.

CONCLUSIONS

We present a comprehensive atlas of the PSC liver and demonstrate an exhaustion-like phenotype of myeloid cells and markers of chronic cytokine expression in late-stage PSC lesions. This atlas expands our understanding of the cellular complexity of PSC and has potential to guide the development of novel treatments.

IMPACT AND IMPLICATIONS

Primary sclerosing cholangitis (PSC) is a rare liver disease characterized by chronic inflammation and irreparable damage to the bile ducts, which eventually results in liver failure. Due to a limited understanding of the underlying pathogenesis of disease, treatment options are limited. To address this, we sequenced healthy and diseased livers to compare the activity, interactions, and localization of immune and non-immune cells. This revealed that hepatocytes lining PSC scar regions co-express cholangiocyte markers, whereas immune cells infiltrate the scar lesions. Of these cells, macrophages, which typically contribute to tissue repair, were enriched in immunoregulatory genes and demonstrated a lack of responsiveness to stimulation. These cells may be involved in maintaining hepatic inflammation and could be a target for novel therapies.

Inhibition of CK2 Diminishes Fibrotic Scar Formation and Improves Outcomes After Ischemic Stroke via Reducing BRD4 Phosphorylation

Fibrotic scars play important roles in tissue reconstruction and functional recovery in the late stage of nervous system injury. However, the mechanisms underlying fibrotic scar formation and regulation remain unclear. Casein kinase II (CK2) is a protein kinase that regulates a variety of cellular functions through the phosphorylation of proteins, including bromodomain-containing protein 4 (BRD4). CK2 and BRD4 participate in fibrosis formation in a variety of tissues. However, whether CK2 affects fibrotic scar formation remains unclear, as do the mechanisms of signal regulation after cerebral ischemic injury. In this study, we assessed whether CK2 could modulate fibrotic scar formation after cerebral ischemic injury through BRD4. Primary meningeal fibroblasts were isolated from neonatal rats and treated with transforming growth factor-β1 (TGF-β1), SB431542 (a TGF-β1 receptor kinase inhibitor) or TBB (a highly potent CK2 inhibitor). Adult SD rats were intraperitoneally injected with TBB to inhibit CK2 after MCAO/R. We found that CK2 expression was increased in vitro in the TGF-β1-induced fibrosis model and in vivo in the MCAO/R injury model. The TGF-β1 receptor kinase inhibitor SB431542 decreased CK2 expression in fibroblasts. The CK2 inhibitor TBB reduced the increases in proliferation, migration and activation of fibroblasts caused by TGF-β1 in vitro, and it inhibited fibrotic scar formation, ameliorated histopathological damage, protected Nissl bodies, decreased infarct volume and alleviated neurological deficits after MCAO/R injury in vivo. Furthermore, CK2 inhibition decreased BRD4 phosphorylation both in vitro and in vivo. The findings of the present study suggested that CK2 may control BRD4 phosphorylation to regulate fibrotic scar formation, to affecting outcomes after ischemic stroke.

TANGO1 inhibitors reduce collagen secretion and limit tissue scarring

Uncontrolled secretion of ECM proteins, such as collagen, can lead to excessive scarring and fibrosis and compromise tissue function. Despite the widespread occurrence of fibrotic diseases and scarring, effective therapies are lacking. A promising approach would be to limit the amount of collagen released from hyperactive fibroblasts. We have designed membrane permeant peptide inhibitors that specifically target the primary interface between TANGO1 and cTAGE5, an interaction that is required for collagen export from endoplasmic reticulum exit sites (ERES). Application of the peptide inhibitors leads to reduced TANGO1 and cTAGE5 protein levels and a corresponding inhibition in the secretion of several ECM components, including collagens. Peptide inhibitor treatment in zebrafish results in altered tissue architecture and reduced granulation tissue formation during cutaneous wound healing. The inhibitors reduce secretion of several ECM proteins, including collagens, fibrillin and fibronectin in human dermal fibroblasts and in cells obtained from patients with a generalized fibrotic disease (scleroderma). Taken together, targeted interference of the TANGO1-cTAGE5 binding interface could enable therapeutic modulation of ERES function in ECM hypersecretion, during wound healing and fibrotic processes.

Exogenous Transforming Growth Factor-β1 and Its Helminth-Derived Mimic Attenuate the Heart's Inflammatory Response to Ischemic Injury and Reduce Mature Scar Size

Coronary reperfusion after acute ST-elevation myocardial infarction (STEMI) is standard therapy to salvage ischemic heart muscle. However, subsequent inflammatory responses within the infarct lead to further loss of viable myocardium. Transforming growth factor (TGF)-β1 is a potent anti-inflammatory cytokine released in response to tissue injury. The aim of this study was to investigate the protective effects of TGF-β1 after MI. In patients with STEMI, there was a significant correlation (P = 0.003) between higher circulating TGF-β1 levels at 24 hours after MI and a reduction in infarct size after 3 months, suggesting a protective role of early increase in circulating TGF-β1. A mouse model of cardiac ischemia reperfusion was used to demonstrate multiple benefits of exogenous TGF-β1 delivered in the acute phase. It led to a significantly smaller infarct size (30% reduction, P = 0.025), reduced inflammatory infiltrate (28% reduction, P = 0.015), lower intracardiac expression of inflammatory cytokines IL-1β and chemokine (C-C motif) ligand 2 (>50% reduction, P = 0.038 and 0.0004, respectively) at 24 hours, and reduced scar size at 4 weeks (21% reduction, P = 0.015) after reperfusion. Furthermore, a low-fibrogenic mimic of TGF-β1, secreted by the helminth parasite Heligmosomoides polygyrus, had an almost identical protective effect on injured mouse hearts. Finally, genetic studies indicated that this benefit was mediated by TGF-β signaling in the vascular endothelium.

Anti-Angiogenic and Anti-Scarring Dual Effect of Galectin-3 Inhibition in Mouse Models of Corneal Wound Healing

Corneal scarring is the third leading cause of global blindness. Neovascularization of ocular tissues is a major predisposing factor in scar development. Although corneal transplantation is effective in restoring vision, some patients are at high risk for graft rejection due to the presence of blood vessels in the injured cornea. Current treatment options for controlling corneal scarring are limited, and outcomes are typically poor. In this study, topical application of a small-molecule inhibitor of galectin-3, GB1265, in mouse models of corneal wound healing, led to the reduction of the following in injured corneas: i) corneal angiogenesis; ii) corneal fibrosis; iii) infiltration of immune cells; and iv) expression of the proinflammatory cytokine IL-1β. Four independent techniques (RNA sequencing, NanoString, real-time quantitative RT-PCR, and Western blot analysis) determined that decreased corneal opacity in the galectin-3 inhibitor-treated corneas was associated with decreases in the numbers of genes and signaling pathways known to promote fibrosis. These findings allowed for a high level of confidence in the conclusion that galectin-3 inhibition by the small-molecule inhibitor GB1265 has dual anti-angiogenic and anti-scarring effects. Targeting galectin-3 by GB1265 is, thus, attractive for the development of innovative therapies for a myriad of ocular and nonocular diseases characterized by pathologic angiogenesis and fibrosis.

Fibroblast mediated dynamics in diffusively uncoupled myocytes: a simulation study using 2-cell motifs

In healthy hearts myocytes are typically coupled to nearest neighbours through gap junctions. Under pathological conditions such as fibrosis, or in scar tissue, or across ablation lines myocytes can uncouple from their neighbours. Electrical conduction may still occur via fibroblasts that not only couple proximal myocytes but can also couple otherwise unconnected regions. We hypothesise that such coupling can alter conduction between myocytes via introduction of delays or by initiation of premature stimuli that can potentially result in reentry or conduction blocks. To test this hypothesis we have developed several 2-cell motifs and investigated the effect of fibroblast mediated electrical coupling between uncoupled myocytes. We have identified various regimes of myocyte behaviour that depend on the strength of gap-junctional conductance, connection topology, and parameters of the myocyte and fibroblast models. These motifs are useful in developing a mechanistic understanding of long-distance coupling on myocyte dynamics and enable the characterisation of interaction between different features such as myocyte and fibroblast properties, coupling strengths and pacing period. They are computationally inexpensive and allow for incorporation of spatial effects such as conduction velocity. They provide a framework for constructing scar tissue boundaries and enable linking of cellular level interactions with scar induced arrhythmia.

Lupus dermal fibroblasts are proinflammatory and exhibit a profibrotic phenotype in scarring skin disease

Fibroblasts are stromal cells known to regulate local immune responses important for wound healing and scar formation; however, the cellular mechanisms driving damage and scarring in patients with cutaneous lupus erythematosus (CLE) remain poorly understood. Dermal fibroblasts in patients with systemic lupus erythematosus (SLE) experience increased cytokine signaling in vivo, but the effect of inflammatory mediators on fibroblast responses in nonscarring versus scarring CLE subtypes is unclear. Here, we examined responses to cytokines in dermal fibroblasts from nonlesional skin of 22 patients with SLE and CLE and 34 individuals acting as healthy controls. Notably, inflammatory cytokine responses were exaggerated in SLE fibroblasts compared with those from individuals acting as healthy controls. In lesional CLE biopsies, these same inflammatory profiles were reflected in single-cell RNA-Seq of SFRP2+ and inflammatory fibroblast subsets, and TGF-β was identified as a critical upstream regulator for inflammatory fibroblasts in scarring discoid lupus lesions. In vitro cytokine stimulation of nonlesional fibroblasts from patients who scar from CLE identified an upregulation of collagens, particularly in response to TGF-β, whereas inflammatory pathways were more prominent in nonscarring patients. Our study revealed that SLE fibroblasts are poised to hyperrespond to inflammation, with differential responses among patients with scarring versus nonscarring disease, providing a potential skin-specific target for mitigating damage.

The TGFβ1/SMADs/Snail1 signaling axis mediates pericyte-derived fibrous scar formation after spinal cord injury

AIMS

The deposition of fibrous scars after spinal cord injury (SCI) affects axon regeneration and the recovery of sensorimotor function. It has been reported that microvascular pericytes in the neurovascular unit are the main source of myofibroblasts after SCI, but the specific molecular targets that regulate pericyte participation in the formation of fibrous scars remain to be clarified.

METHODS

In this study, a rat model of spinal cord dorsal hemisection injury was used. After SCI, epigallocatechin gallate (EGCG) was intraperitoneally injected to block the TGFβ1 signaling pathway or LV-Snail1-shRNA was immediately injected near the core of the injury using a microsyringe to silence Snail1 expression. Western blotting and RT-qPCR were used to analyze protein expression and transcription levels in tissues. Nissl staining and immunofluorescence analysis were used to analyze neuronal cell viability, scar tissue, and axon regeneration after SCI. Finally, the recovery of hind limb function after SCI was evaluated.

RESULTS

The results showed that targeted inhibition of Snail1 could block TGFβ1-induced pericyte-myofibroblast differentiation in vitro. In vivo experiments showed that timely blockade of Snail1 could reduce fibrous scar deposition after SCI, promote axon regeneration, improve neuronal survival, and facilitate the recovery of lower limb motor function.

CONCLUSION

In summary, Snail1 promotes the deposition of fibrous scars and inhibits axonal regeneration after SCI by inducing the differentiation of pericytes into myofibroblasts. Snail1 may be a promising therapeutic target for SCI.

Pericardial delta like non-canonical NOTCH ligand 1 (Dlk1) augments fibrosis in the heart through epithelial to mesenchymal transition

BACKGROUND

Heart failure due to myocardial infarction (MI) involves fibrosis driven by epicardium-derived cells (EPDCs) and cardiac fibroblasts, but strategies to inhibit and provide cardio-protection remains poor. The imprinted gene, non-canonical NOTCH ligand 1 (Dlk1), has previously been shown to mediate fibrosis in the skin, lung and liver, but very little is known on its effect in the heart.

METHODS

Herein, human pericardial fluid/plasma and tissue biopsies were assessed for DLK1, whereas the spatiotemporal expression of Dlk1 was determined in mouse hearts. The Dlk1 heart phenotype in normal and MI hearts was assessed in transgenic mice either lacking or overexpressing Dlk1. Finally, in/ex vivo cell studies provided knowledge on the molecular mechanism.

RESULTS

Dlk1 was demonstrated in non-myocytes of the developing human myocardium but exhibited a restricted pericardial expression in adulthood. Soluble DLK1 was twofold higher in pericardial fluid (median 45.7 [34.7 (IQR)) μg/L] from cardiovascular patients (n = 127) than in plasma (median 26.1 μg/L [11.1 (IQR)]. The spatial and temporal expression pattern of Dlk1 was recapitulated in mouse and rat hearts. Similar to humans lacking Dlk1, adult Dlk1-/- mice exhibited a relatively mild developmental, although consistent cardiac phenotype with some abnormalities in heart size, shape, thorax orientation and non-myocyte number, but were functionally normal. However, after MI, scar size was substantially reduced in Dlk1-/- hearts as compared with Dlk1+/+ littermates. In line, high levels of Dlk1 in transgenic mice Dlk1fl/fl xWT1GFPCre and Dlk1fl/fl xαMHCCre/+Tam increased scar size following MI. Further mechanistic and cellular insight demonstrated that pericardial Dlk1 mediates cardiac fibrosis through epithelial to mesenchymal transition (EMT) of the EPDC lineage by maintaining Integrin β8 (Itgb8), a major activator of transforming growth factor β and EMT.

CONCLUSIONS

Our results suggest that pericardial Dlk1 embraces a, so far, unnoticed role in the heart augmenting cardiac fibrosis through EMT. Monitoring DLK1 levels as well as targeting pericardial DLK1 may thus offer new venues for cardio-protection.

Single-Cell Mapping of Large and Small Arteries During Hypertensive Aging

Vascular aging is directly related to several major diseases including clinical primary hypertension. Conversely, elevated blood pressure itself accelerates vascular senescence. However, the interaction between vascular aging and hypertension has not been characterized during hypertensive aging. To depict the interconnectedness of complex mechanisms between hypertension and aging, we performed single-cell RNA sequencing of aorta, femoral and mesentery arteries, respectively, from male Wistar Kyoto rats and male spontaneously hypertensive rats aging 16 or 72 weeks. We integrated 12 data sets to map the blood vessels of senile hypertension from 3 perspective: vascular aging, hypertension, and vascular type. We found that aging and hypertension independently exerted a significant impact on the alteration of cellular composition and artery remodeling, even greater when superimposed. Consistently, smooth muscle cells (SMCs) underwent phenotypic switching from contractile toward synthetic, apoptotic, and senescent SMCs with aging/hypertension. Furthermore, we identified 3 subclusters of Spp1high, encoding protein osteopontin (OPN), synthetic SMCs, Spp1high matrix activated fibroblasts, and Spp1high scar-associated macrophage involved in hypertensive aging. Spp1high scar-associated macrophage enriched for reactive oxygen species metabolic process and cell migration-associated function. Cell-cell communication analysis revealed Spp1-Cd44 receptor pairing was markedly aggravated in the hypertensive aging condition. Importantly, the concentration of serum OPN significantly potentiated in aged hypertensive patients compared with the normal group. Thus, we provide a comprehensive cell atlas to systematically resolve the cellular diversity and dynamic cellular communication changes of the vessel wall during hypertensive aging, identifying a protein marker OPN as a potential regulator of vascular remodeling during hypertensive aging.

Integrin αV mediated activation of myofibroblast via mechanoparacrine of transforming growth factor β1 in promoting fibrous scar formation after myocardial infarction

BACKGROUND

Myocardial infarction (MI) dramatically changes the mechanical stress, which is intensified by the fibrotic remodeling. Integrins, especially the αV subunit, mediate mechanical signal and mechanoparacrine of transforming growth factor β1 (TGF-β1) in various organ fibrosis by activating CFs into myofibroblasts (MFBs). We investigated a possible role of integrin αV mediated mechanoparacrine of TGF-β1 in MFBs activation for fibrous reparation in mice with MI.

METHODS

Heart samples from MI, sham, or MI plus cilengitide (14 mg/kg, specific integrin αV inhibitor) treated mice, underwent functional and morphological assessments by echocardiography, and histochemistry on 7, 14 and 28 days post-surgery. The mechanical and ultrastructural changes of the fibrous scar were further evaluated by atomic mechanics microscope (AFM), immunofluorescence, second harmonic generation (SHG) imaging, polarized light and scanning electron microscope, respectively. Hydroxyproline assay was used for total collagen content, and western blot for protein expression profile examination. Fibroblast bioactivities, including cell shape, number, Smad2/3 signal and expression of extracellular matrix (ECM) related proteins, were further evaluated by microscopic observation and immunofluorescence in polyacrylamide (PA) hydrogel with adjustable stiffness, which was re-explored in fibroblast cultured on stiff matrix after silencing of integrin αV. The content of total and free TGF-β1 was tested by enzyme-linked immunosorbent assay (ELISA) in both infarcted tissue and cell samples.

RESULT

Increased stiffness with heterogeneity synchronized with integrin αV and alpha smooth muscle actin (α-SMA) positive MFBs accumulation in those less mature fibrous areas. Cilengitide abruptly reduced collagen content and disrupted collagen alignment, which also decreased TGF-β1 bioavailability, Smad2/3 phosphorylation, and α-SMA expression in the fibrous area. Accordingly, fibroblast on stiff but not soft matrix exhibited obvious MFB phenotype, as evidenced by enlarged cell, hyperproliferation, well-developed α-SMA fibers, and elevated ECM related proteins, while silencing of integrin αV almost abolished this switch via attenuating paracrine of TGF-β1 and nuclear translocation of Smad2/3.

CONCLUSION

This study illustrated that increased tissue stiffness activates CFs into MFBs by integrin αV mediated mechanoparacrine of TGF-β1, especially in immature scar area, which ultimately promotes fibrous scar maturation.

Identification of Periostin as a critical niche for myofibroblast dynamics and fibrosis during tendon healing

Tendon injuries are a major clinical problem, with poor patient outcomes caused by abundant scar tissue deposition during healing. Myofibroblasts play a critical role in the initial restoration of structural integrity after injury. However, persistent myofibroblast activity drives the transition to fibrotic scar tissue formation. As such, disrupting myofibroblast persistence is a key therapeutic target. While myofibroblasts are typically defined by the presence of αSMA+ stress fibers, αSMA is expressed in other cell types including the vasculature. As such, modulation of myofibroblast dynamics via disruption of αSMA expression is not a translationally tenable approach. Recent work has demonstrated that Periostin-lineage (PostnLin) cells are a precursor for cardiac fibrosis-associated myofibroblasts. In contrast to this, here we show that PostnLin cells contribute to a transient αSMA+ myofibroblast population that is required for functional tendon healing, and that Periostin forms a supportive matrix niche that facilitates myofibroblast differentiation and persistence. Collectively, these data identify the Periostin matrix niche as a critical regulator of myofibroblast fate and persistence that could be targeted for therapeutic manipulation to facilitate regenerative tendon healing.

Dysfunctional Epithelial Barrier Is Characterized by Reduced E-Cadherin in Idiopathic Subglottic Stenosis

OBJECTIVES

To aim of the study was to characterize the molecular profile and functional phenotype of idiopathic subglottic stenosis (iSGS)-scar epithelium.

METHODS

Human tracheal biopsies from iSGS scar (n = 6) and matched non-scar (n = 6) regions were analyzed using single-cell RNA sequencing (scRNA-seq). Separate specimens were used for epithelial cell expansion in vitro to assess average growth rate and functional capabilities using transepithelial-electrical resistance (TEER), fluorescein isothiocyanate-dextran flux permeability assay, ciliary coverage, and cilia beating frequency (CBF). Finally, epithelial tight junction protein expression of cultured cells was quantified using immunoblot assay (n = 4) and immunofluorescence (n = 6).

RESULTS

scRNA-seq analysis revealed a decrease in goblet, ciliated, and basal epithelial cells in the scar iSGS cohort. Furthermore, mRNA expression of proteins E-cadherin, claudin-3, claudin-10, occludin, TJP1, and TJP2 was also reduced (p < 0.001) in scar epithelium. Functional assays demonstrated a decrease in TEER (paired 95% confidence interval [CI], 195.68-890.83 Ω × cm2 , p < 0.05), an increase in permeability (paired 95% CI, -6116.00 to -1401.99 RFU, p < 0.05), and reduced epithelial coverage (paired 95% CI, 0.1814-1.766, fold change p < 0.05) in iSGS-scar epithelium relative to normal controls. No difference in growth rate (p < 0.05) or CBF was found (paired 95% CI, -2.118 to 3.820 Hz, p > 0.05). Immunoblot assay (paired 95% CI, 0.0367-0.605, p < 0.05) and immunofluorescence (paired 95% CI, 13.748-59.191 mean grey value, p < 0.05) revealed E-cadherin reduction in iSGS-scar epithelium.

CONCLUSION

iSGS-scar epithelium has a dysfunctional barrier and reduced structural protein expression. These results are consistent with dysfunctional epithelium seen in other airway pathology. Further studies are warranted to delineate the causality of epithelial dysfunction on the downstream fibroinflammatory cascade in iSGS.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:374-381, 2024.

The expression pattern of cytokeratin 6a in epithelial cells of different origin in dermo-epidermal skin substitutes in vivo

Keratinocytes are the predominant cell type of skin epidermis. Through the programmed process of differentiation, they form a cornified envelope that provides a physical protective barrier against harmful external environment. Keratins are major structural proteins of keratinocytes that together with actin filaments and microtubules form the cytoskeleton of these cells. In this study, we examined the expression pattern and distribution of cytokeratin 6a (CK6a) in healthy human skin samples of different body locations, in fetal and scar skin samples, as well as in dermo-epidermal skin substitutes (DESSs). We observed that CK6a expression is significantly upregulated in fetal skin and scar tissue as well as in skin grafts after short-term transplantation. Importantly, the abundance of CK6a corresponds directly to the expression pattern of wound healing marker CK16. We postulate that CK6a is a useful marker to accurately evaluate the homeostatic state of DESSs.

Automated spatially targeted optical micro proteomics identifies fibroblast- and macrophage-specific regulation of myocardial infarction scar maturation in rats

Myocardial infarction (MI) results from occlusion of blood supply to the heart muscle causing death of cardiac muscle cells. Following myocardial infarction (MI), extracellular matrix deposition and scar formation mechanically stabilize the injured heart as damaged myocytes undergo necrosis and removal. Fibroblasts and macrophages are key drivers of post-MI scar formation, maturation, and ongoing long-term remodelling; however, their individual contributions are difficult to assess from bulk analyses of infarct scar. Here, we employ state-of-the-art automated spatially targeted optical micro proteomics (autoSTOMP) to photochemically tag and isolate proteomes associated with subpopulations of fibroblasts (SMA+) and macrophages (CD68+) in the context of the native, MI tissue environment. Over a time course of 6-weeks post-MI, we captured dynamic changes in the whole-infarct proteome and determined that some of these protein composition signatures were differentially localized near SMA+ fibroblasts or CD68+ macrophages within the scar region. These results link specific cell populations to within-infarct protein remodelling and illustrate the distinct metabolic and structural processes underlying the observed physiology of each cell type.

Biological effect of laser-assisted scar healing (LASH) on standardized human three-dimensional wound healing skin models using fractional non-ablative 1540 nm Er:Glass or 1550 nm diode lasers

PURPOSE

In postoperative wound healing after surgical operations or ablative laser treatments, recent studies suggest the timely use of non-ablative fractional laser treatments with the aim to improve wound healing and prevent pathological scar formation. However, the underlying molecular mechanisms are poorly understood. The aim of this study was to investigate the effects of laser-assisted scar healing (LASH) at the molecular level and to combine it with already established wound healing-promoting local treatments.

METHODS

We irradiated full-thickness 3D skin models with a fractional ablative Er:YAG laser to set standardized lesions to the epidermal and upper dermal layer. Subsequently, LASH was induced by irradiating the models with either a fractional non-ablative 1540 nm Er:Glass or 1550 nm diode laser. In addition, we tested the combination of non-ablative fractional laser treatment and topical aftercare with a dexpanthenol-containing ointment (DCO).

RESULTS

Histological analysis revealed that models irradiated with the 1540 nm Er:Glass or 1550 nm diode laser exhibited accelerated but not complete wound closure after 16 h. In contrast, additional topical posttreatment with DCO resulted in complete wound closure. At gene expression level, both non-ablative laser systems showed similar effects on epidermal differentiation and mild anti-inflammatory properties. The additional posttreatment with DCO enhanced the wound-healing effects of LASH, especially the upregulation of epidermal differentiation markers and anti-inflammatory cytokines at the gene expression level.

CONCLUSION

This in vitro study deciphers the biological effects of LASH with a fractional non-ablative 1540 nm Er:Glass or a 1550 nm diode laser in 3D skin models. These data help to better understand the biological properties of the LASH technique and is important to optimize its application.

Structural and dynamical changes of the Streptococcus gordonii metalloregulatory ScaR protein induced by Mn2+ ion binding

Divalent metal ions are essential micronutrients for many intercellular reactions. Maintaining their homeostasis is necessary for the survival of bacteria. In Streptococcus gordonii, one of the primary colonizers of the tooth surface, the cellular concentration of manganese ions (Mn2+) is regulated by the manganese-sensing transcriptional factor ScaR which controls the expression of proteins involved in manganese homeostasis. To resolve the molecular mechanism through which the binding of Mn2+ ions increases the binding affinity of ScaR to DNA, a variety of computational (QM and MD) and experimental (ITC, DSC, EMSA, EPR, and CD) methods were applied. The computational results showed that Mn2+ binding induces a conformational change in ScaR that primarily affects the position of the DNA binding domains and, consequently, the DNA binding affinity of the protein. In addition, experimental results revealed a 1:4 binding stoichiometry between ScaR dimer and Mn2+ ions, while the computational results showed that the binding of Mn2+ ions in the primary binding sites is sufficient to induce the observed conformational change of ScaR.

[Study of senescence protein p66Shc on myocardial tissue repair in adult mice]

Our previous study has shown that p66Shc plays an important role in the process of myocardial regeneration in newborn mice, and p66Shc deficiency leads to weakened myocardial regeneration in newborn mice. This study aims to explore the role of p66Shc protein in myocardial injury repair after myocardial infarction in adult mice, in order to provide a new target for the treatment of myocardial injury after myocardial infarction. Mouse myocardial infarction models of adult wild-type (WT) and p66Shc knockout (KO) were constructed by anterior descending branch ligation. The survival rate and heart-to-body weight ratio of two models were compared and analyzed. Masson's staining was used to identify scar area of injured myocardial tissue, and myocyte area was determined by wheat germ agglutinin (WGA) staining. TUNEL staining was used to detect the cardiomyocyte apoptosis. The protein expression of brain natriuretic peptide (BNP), a common marker of myocardial hypertrophy, was detected by Western blotting. The results showed that there was no significant difference in survival rate, myocardial scar area, myocyte apoptosis, and heart weight to body weight ratio between the WT and p66ShcKO mice after myocardial infarction surgery. Whereas the protein expression level of BNP in the p66ShcKO mice was significantly down-regulated compared with that in the WT mice. These results suggest that, unlike in neonatal mice, the deletion of p66Shc has no significant effect on myocardial injury repair after myocardial infarction in adult mice.

CD36/Lyn kinase interactions within macrophages promotes pulmonary fibrosis in response to oxidized phospholipid

Recent data from human studies and animal models have established roles for type II alveolar epithelial cell (AEC2) injury/apoptosis and monocyte/macrophage accumulation and activation in progressive lung fibrosis. Although the link between these processes is not well defined, we have previously shown that CD36-mediated uptake of apoptotic AEC2s by lung macrophages is sufficient to drive fibrosis. Importantly, apoptotic AEC2s are rich in oxidized phospholipids (oxPL), and amongst its multiple functions, CD36 serves as a scavenger receptor for oxPL. Recent studies have established a role for oxPLs in alveolar scarring, and we hypothesized that uptake and accrual of oxPL by CD36 would cause a macrophage phenotypic change that promotes fibrosis. To test this hypothesis, we treated wild-type and CD36-null mice with the oxPL derivative oxidized phosphocholine (POVPC) and found that CD36-null mice were protected from oxPL-induced scarring. Compared to WT mice, fewer macrophages accumulated in the lungs of CD36-null animals, and the macrophages exhibited a decreased accumulation of intracellular oxidized lipid. Importantly, the attenuated accrual of oxPL in CD36-null macrophages was associated with diminished expression of the profibrotic mediator, TGFβ. Finally, the pathway linking oxPL uptake and TGFβ expression was found to require CD36-mediated activation of Lyn kinase. Together, these observations elucidate a causal pathway that connects AEC2 injury with lung macrophage activation via CD36-mediated uptake of oxPL and suggest several potential therapeutic targets.

Decoding fibrosis in the human central nervous system

Recent advancements in human tissue analyses and animal models have revealed that fibrotic scarring is a common response to various lesions in the central nervous system (CNS). Perivascular cells within the brain or spinal cord give rise to stromal fibroblasts that form fibrotic scar tissue. In this review, we summarize the current understanding of fibrotic scar formation in different CNS lesions and evaluate published human single-cell gene expression datasets to gather information on perivascular cells. Specifically, we highlight the classification of pericytes and fibroblast subtypes and compare the marker expression of perivascular cells across different datasets.

Glucocorticoid Receptor Antagonism and Cardiomyocyte Regeneration Following Myocardial Infarction: A Systematic Review

Myocardial regeneration has been a topic of interest in literature and research in recent years. An evolving approach reported is glucocorticoid (GC) receptor antagonism and its role in the regeneration of cardiomyocytes. The authors of this study aim to explore the reported literature on GC receptor antagonism and its effects on cardiomyocyte remodeling, hypertrophy, scar formation, and ongoing cardiomyocyte death following cardiac injury. This article overviews cellular biology, mechanisms of action, clinical implications, challenges, and future considerations. The authors of this study conducted a systematic review utilizing the Cochrane methodology and PRISMA guidelines. This study includes data collected and interpreted from 30 peer-reviewed articles from 3 databases with the topic of interest. The mammalian heart has regenerative potential during its embryonic and fetal phases which is lost during its developmental processes. The microenvironment, intrinsic molecular mechanisms, and systemic and external factors impact cardiac regeneration. GCs influence these aspects in some cases. Consequently, GC receptor antagonism is emerging as a promising potential target for stimulating endogenous cardiomyocyte proliferation, aiding in cardiomyocyte regeneration following a cardiac injury such as a myocardial infarction (MI). Experimental studies on neonatal mice and zebrafish have shown promising results with GC receptor ablation (or brief pharmacological antagonism) promoting the survival of myocardial cells, re-entry into the cell cycle, and cellular division, resulting in cardiac muscle regeneration and diminished scar formation. Transient GC receptor antagonism has the potential to stimulate cardiomyocyte regeneration and help prevent the dreaded complications of MI. More trials based on human populations are encouraged to justify their applications and weigh the risk-benefit ratio.

Fingolimod (FTY720) Hinders Interferon-γ-Mediated Fibrotic Scar Formation and Facilitates Neurological Recovery After Spinal Cord Injury

Following spinal cord injury (SCI), fibrotic scar inhibits axon regeneration and impairs neurological function recovery. It has been reported that T cell-derived interferon (IFN)-γ plays a pivotal role in promoting fibrotic scarring in neurodegenerative disease. However, the role of IFN-γ in fibrotic scar formation after SCI has not been declared. In this study, a spinal cord crush injury mouse was established. Western blot and immunofluorescence showed that IFN-γ was surrounded by fibroblasts at 3, 7, 14, and 28 days post-injury. Moreover, IFN-γ is mainly secreted by T cells after SCI. Further, in situ injection of IFN-γ into the normal spinal cord resulted in fibrotic scar formation and inflammation response at 7 days post-injection. After SCI, the intraperitoneal injection of fingolimod (FTY720), a sphingosine-1-phosphate receptor 1 (S1PR1) modulator and W146, an S1PR1 antagonist, significantly reduced T cell infiltration, attenuating fibrotic scarring via inhibiting IFN-γ/IFN-γR pathway, while in situ injection of IFN-γ diminished the effect of FTY720 on reducing fibrotic scarring. FTY720 treatment inhibited inflammation, decreased lesion size, and promoted neuroprotection and neurological recovery after SCI. These findings demonstrate that the inhibition of T cell-derived IFN-γ by FTY720 suppressed fibrotic scarring and contributed to neurological recovery after SCI.

Autophagy protects against vocal fold injury-induced fibrosis

Vocal fold scar formation due to vocal fold injury (VFI) is a common cause of surgery or trauma-induced voice disorders. Severe scar formation can lead to reduced voice quality or even be life-threatening. Here, we investigated the role of autophagy in VFI, focusing on fibrosis as a consequence of autophagy in inducing VFI. A VFI model was constructed in rats by dissecting the lamina propria tissue from the thyroarytenoid muscle. Real-time PCR and Western blot were used to analyze expressions of autophagy markers, including Beclin1 and Atg7, in VFI. Tgfb1 and Col1a1 were assessed to determine the correlation of fibrosis with VFI progression and autophagy levels. Rat vocal fold fibroblasts were also treated with TGF-β1 or rapamycin, which activates and suppresses autophagy respectively, to explore how autophagy regulates fibrosis in VFI. Initially, we observed that autophagy was downregulated in vocal fold mucosa after VFI in rats. This was particularly evident by the time-dependent downregulation of Beclin1 and Atg7 following VFI. Concurrently, levels of Tgfb1 and Col1a1 also surged, hinting at elevated fibrosis levels. Furthermore, our experiments with TGF-β1 stimulation revealed that it inhibited autophagy in rat vocal fold fibroblasts. Interestingly, when we introduced rapamycin, this effect was reversed. Our data suggest that autophagy is a suppressor of VFI by alleviating fibrosis, making targeting autophagy a potential therapeutic route in VFI.NEW & NOTEWORTHY The study has demonstrated that autophagy is a suppressor of VFI by alleviating fibrosis, making autophagy a potential therapeutic target in VFI.

Building a pathway to recovery: Targeting ECM remodeling in CNS injuries

Extracellular matrix (ECM) is a complex and dynamic network of proteoglycans, proteins, and other macromolecules that surrounds cells in tissues. The ECM provides structural support to cells and plays a critical role in regulating various cellular functions. ECM remodeling is a dynamic process involving the breakdown and reconstruction of the ECM. This process occurs naturally during tissue growth, wound healing, and tissue repair. However, in the context of central nervous system (CNS) injuries, dysregulated ECM remodeling can lead to the formation of fibrotic and glial scars. CNS injuries encompass various traumatic events, including concussions and fractures. Following CNS trauma, the formation of glial and fibrotic scars becomes prominent. Glial scars primarily consist of reactive astrocytes, while fibrotic scars are characterized by an abundance of ECM proteins. ECM remodeling plays a pivotal and tightly regulated role in the development of these scars after spinal cord and brain injuries. Various factors like ECM components, ECM remodeling enzymes, cell surface receptors of ECM molecules, and downstream pathways of ECM molecules are responsible for the remodeling of the ECM. The aim of this review article is to explore the changes in ECM during normal physiological conditions and following CNS injuries. Additionally, we discuss various approaches that target various factors responsible for ECM remodeling, with a focus on promoting axon regeneration and functional recovery after CNS injuries. By targeting ECM remodeling, it may be possible to enhance axonal regeneration and facilitate functional recovery after CNS injuries.

Modified human respiratory tract model to describe the retention of plutonium in scar tissues

The Human Respiratory Tract Model described in Publication 130 of the International Commission on Radiological Protection provides some mechanisms to account for retention of material that can be subject to little to no mechanical transport or absorption into the blood. One of these mechanisms is 'binding', which refers to a process by which a fraction ('bound fraction') of the dissolved material chemically binds to the tissue of the airway wall. The value of the bound fraction can have a significant impact on the radiation doses imparted to different parts of the respiratory tract. To properly evaluate-and quantify-bound fraction for an element, one would need information on long-term retention of the element in individual compartments of the respiratory tract. Such data on regional retention of plutonium in the respiratory tract of four workers-who had inhaled materials with solubility ranging from soluble nitrate to very insoluble high-fired oxides-were obtained at the United States Transuranium and Uranium Registries. An assumption of bound fraction alone was found to be inconsistent with this dataset and also with a review of the literature. Several studies show evidence of retention of a large amount of Pu activity in the scar tissues of humans and experimental animals, and accordingly, a model structure with scar-tissue compartments was proposed. The transfer rates to these compartments were determined using Markov Chain Monte Carlo analysis of the bioassay and post-mortem data, considering the uncertainties associated with deposition, dissolution and particle clearance parameters. The models predicted that a significant amount-between 20 and 100% for the cases analyzed-of plutonium retained in the respiratory tract was sequestered in the scar tissues. Unlike chemically-bound Pu that irradiates sensitive epithelial cells, Pu in scar tissues may not be dosimetrically significant because the scar tissues absorb most, if not all, of the energy from alpha emissions.

Niclosamide inhibits TGF-β1-induced fibrosis of human Tenon's fibroblasts by regulating the MAPK-ERK1/2 pathway

Preventing postoperative bleb scar formation is an effective way of improving glaucoma filtration surgery (GFS) outcome. Use of more effective antifibrotic drugs with fewer adverse effects may be a good way to address the problem. In the present study, we use a primary cell model, consisting of Tenon's fibroblasts obtained from patients with glaucoma, which were stimulated with TGF-β1 to induce the fibrotic phenotype. We explored the effects of niclosamide on TGF-β1-induced fibrosis in these cells and examined its underlying mechanism of action. A transcriptome sequencing assay was used to explore possible signaling pathways involved. Niclosamide inhibited cell proliferation and migration, and decreased the levels of alpha-smooth muscle actin, type I and type III collagen in human Tenon's fibroblasts induced by TGF-β1. Niclosamide also induced apoptosis and counteracted TGF-β1-induced cytoskeletal changes and extracellular matrix accumulation. Moreover, niclosamide decreased TGF-β1-induced phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) protein expression in human Tenon's fibroblasts. The results indicate that niclosamide inhibits TGF-β1-induced fibrosis in human Tenon's fibroblasts by blocking the MAPK-ERK1/2 signaling pathway. Thus, niclosamide is a potentially promising antifibrotic drug that could improve glaucoma filtration surgery success rate.

Inhibition of heat shock protein 47 suppressed collagen production in Tenon's capsule fibroblasts

INTRODUCTION

Glaucoma is the leading cause of irreversible blindness worldwide, and conjunctival bleb scarring remains the most frequent reason for the failure of glaucoma filtration surgery. Excessive proliferation of fibroblasts from Tenon's capsule and excessive deposition of collagen contribute to the scarification of the conjunctival bleb. Heat shock protein 47 (HSP47) is assumed to act as a collagen-specific molecular chaperone, and thereby involved in the pathogenesis of fibrotic diseases. Therefore, we investigated the effect of HSP47 knockout against collagen type I (COLI) production in rat tenon's fibroblasts.

MATERIAL AND METHODS

Newborn rat tenon's fibroblasts were cultured and verified by anti-vimentin antibody. Transfection efficiency of small interference RNA targeted against HSP47 was confirmed by quantitative real-time polymerase chain reaction (RT-qPCR) at 48 h after siRNA transfection and by western blot at 72 h after transfection. The mRNA and protein expression of HSP 47 and COLI were detected by RT-qPCR and western blot. The proliferation of cells was measured by cell counting kit-8 assay.

RESULTS

HSP47 siRNA down-regulated the mRNA and protein levels of HSP47 in rat Tenon's fibroblasts, and suppressed the mRNA and protein expression of COLI. Moreover, HSP47 siRNA had no significant effect on proliferation of rat Tenon's fibroblasts.

CONCLUSIONS

HSP47 siRNA inhibits the production of COLI in rat Tenon's fibroblasts, and may be the potential therapeutic method in bleb scarring after glaucoma filtration surgery.

Effects of Ripasudil, a Rho-Kinase Inhibitor, on Scar Formation in a Mouse Model of Filtration Surgery

PURPOSE

Glaucoma is a leading cause of blindness worldwide. Characteristic changes occur in the optic nerve and visual field of patients with glaucoma; optic nerve damage can be mitigated by lowering intraocular pressure. Treatment modalities include drugs and lasers; filtration surgery is necessary for patients with insufficient intraocular pressure reduction. Scar formation often contributes to glaucoma filtration surgery failure by increasing fibroblast proliferation and activation. Here, we examined the effects of ripasudil, a Rho-associated protein kinase (ROCK) inhibitor, on postoperative scar formation in human Tenon's fibroblasts.

METHODS

Collagen gel contraction assays were used to compare contractility activity among ripasudil and other anti-glaucoma drugs. The effect of Ripasudil in combination with other anti-glaucoma drugs and transforming growth factor-β (TGF-β), latanoprost and timolol-induce contractions were also tested in this study. Immunofluorescence and Western blotting were used to study the expression of factors relating scarring formation.

RESULTS

Ripasudil inhibited contraction in collagen gel assay and reduced α-smooth muscle actin (SMA) and vimentin (scar formation-related factors) expression, which was inversely promoted by latanoprost, timolol or TGF-β. Ripasudil also inhibited contraction on TGF-β, latanoprost and timolol-induced contraction. Furthermore, we investigated the effects of ripasudil on postoperative scarring in a mouse model; ripasudil suppressed postoperative scar formation by altering the expression of α-SMA and vimentin.

CONCLUSIONS

These results suggest that ripasudil, ROCK inhibitor may inhibit excessive fibrosis after glaucoma filtering surgery vis inhibition the transdifferentiation of tenon fibroblast into myofibroblast and may have a potential effect as anti-scarring for glaucoma filtration surgery.

Nestin identifies a subpopulation of rat ventricular fibroblasts and participates in cell migration

Fibroblast progenitor cells migrate to the endocardial region during cardiogenesis, and the migration of ventricular fibroblasts to the ischemically damaged region of the infarcted adult heart is a seminal event of reparative fibrosis. The intermediate filament protein nestin is implicated in cell migration and expression identified in a subpopulation of scar-derived myofibroblasts. The present study tested the hypothesis that fibroblast progenitor cells express nestin, and the intermediate filament protein drives the migratory phenotype of ventricular fibroblasts. Transcription factor 21 (Tcf21)- and Wilms tumor 1 (WT1)-fibroblast progenitor cells identified in the epicardial/endocardial regions of the E12.5- to E13.5-day embryonic mouse heart predominantly expressed nestin. Nuclear Tcf21/WT1 staining was identified in neonatal rat ventricular fibroblasts (NNVFbs), and a subpopulation coexpressed nestin. Nuclear Tcf21/WT1 expression persisted in adult rat ventricular fibroblasts, whereas nestin protein levels were downregulated. Nestin-expressing NNVFbs exhibited a unique phenotype as the subpopulation was refractory to cell cycle reentry in response to selective stimuli. Nestin(-)- and nestin(+)-scar-derived rat myofibroblasts plated in Matrigel unmasked a migratory phenotype characterized by the de novo formation of lumen-like structures. The elongated membrane projections emanating from scar myofibroblasts delineating the boundary of lumen-like structures expressed nestin. Lentiviral short-hairpin RNA (shRNA)-mediated nestin depletion inhibited the in vitro migratory response of NNVFbs as the wound radius was significantly larger compared with NNVFbs infected with the empty lentivirus. Thus, nestin represents a marker of embryonic Tcf21/WT1(+)-fibroblast progenitor cells. The neonatal rat heart contains a distinct subpopulation of nestin-immunoreactive Tcf21/WT1(+) fibroblasts refractory to cell cycle reentry, and the intermediate filament protein may preferentially facilitate ventricular fibroblast migration during physiological/pathological remodeling.NEW & NOTEWORTHY Tcf21/WT1(+)-fibroblast progenitor cells of the embryonic mouse heart predominantly express the intermediate filament protein nestin. A subpopulation of Tcf21/WT1(+)-neonatal rat ventricular fibroblasts express nestin and are refractory to selective stimuli influencing cell cycle reentry. Scar-derived myofibroblasts plated in Matrigel elicit the formation of lumen-like structures characterized by the appearance of nestin(+)-membrane projections. Lentiviral shRNA-mediated nestin depletion in a subpopulation of neonatal rat ventricular fibroblasts suppressed the migratory response following the in vitro scratch assay.

p53 Regulates the Extent of Fibroblast Proliferation and Fibrosis in Left Ventricle Pressure Overload

BACKGROUND

Cardiomyopathy is characterized by the pathological accumulation of resident cardiac fibroblasts that deposit ECM (extracellular matrix) and generate a fibrotic scar. However, the mechanisms that control the timing and extent of cardiac fibroblast proliferation and ECM production are not known, hampering the development of antifibrotic strategies to prevent heart failure.

METHODS

We used the Tcf21 (transcription factor 21)MerCreMer mouse line for fibroblast-specific lineage tracing and p53 (tumor protein p53) gene deletion. We characterized cardiac physiology and used single-cell RNA-sequencing and in vitro studies to investigate the p53-dependent mechanisms regulating cardiac fibroblast cell cycle and fibrosis in left ventricular pressure overload induced by transaortic constriction.

RESULTS

Cardiac fibroblast proliferation occurs primarily between days 7 and 14 following transaortic constriction in mice, correlating with alterations in p53-dependent gene expression. p53 deletion in fibroblasts led to a striking accumulation of Tcf21-lineage cardiac fibroblasts within the normal proliferative window and precipitated a robust fibrotic response to left ventricular pressure overload. However, excessive interstitial and perivascular fibrosis does not develop until after cardiac fibroblasts exit the cell cycle. Single-cell RNA sequencing revealed p53 null fibroblasts unexpectedly express lower levels of genes encoding important ECM proteins while they exhibit an inappropriately proliferative phenotype. in vitro studies establish a role for p53 in suppressing the proliferative fibroblast phenotype, which facilitates the expression and secretion of ECM proteins. Importantly, Cdkn2a (cyclin-dependent kinase inhibitor 2a) expression and the p16Ink4a-retinoblastoma cell cycle control pathway is induced in p53 null cardiac fibroblasts, which may eventually contribute to cell cycle exit and fulminant scar formation.

CONCLUSIONS

This study reveals a mechanism regulating cardiac fibroblast accumulation and ECM secretion, orchestrated in part by p53-dependent cell cycle control that governs the timing and extent of fibrosis in left ventricular pressure overload.

Excess KLHL24 Impairs Skin Wound Healing through the Degradation of Vimentin

Start codon variants in ubiquitin ligase KLHL24 lead to a gain-of-function mutant KLHL24-ΔN28, which mediates the excessive degradation of keratin 15, desmin, and keratin 14, resulting in alopecia, cardiopathy, and epidermolysis bullosa syndrome. Patients with alopecia, cardiopathy, and epidermolysis bullosa syndrome normally present atrophic scars after wounds heal, which is rare in KRT14-related epidermolysis bullosa. The mechanisms underlying the formation of atrophic scars in epidermolysis bullosa of patients with alopecia, cardiopathy, and epidermolysis bullosa syndrome remain unclear. This study showed that KLHL24-ΔN28 impaired skin wound healing by excessively degrading vimentin. Heterozygous Klhl24c.3G>T knock-in mice displayed delayed wound healing and decreased wound collagen deposition. We identified vimentin as an unreported substrate of KLHL24. KLHL24-ΔN28 mediated the excessive degradation of vimentin, which failed to maintain efficient fibroblast proliferation and activation during wound healing. Furthermore, by mediating vimentin degradation, KLHL24 can hinder myofibroblast activation, which attenuated bleomycin-induced skin fibrosis. These findings showed the function of KLHL24 in regulating tissue remodeling, atrophic scarring, and fibrosis.

Scar/WAVE has Rac GTPase-independent functions during cell wound repair

Rho family GTPases regulate both linear and branched actin dynamics by activating downstream effectors to facilitate the assembly and function of complex cellular structures such as lamellipodia and contractile actomyosin rings. Wiskott-Aldrich Syndrome (WAS) family proteins are downstream effectors of Rho family GTPases that usually function in a one-to-one correspondence to regulate branched actin nucleation. In particular, the WAS protein Scar/WAVE has been shown to exhibit one-to-one correspondence with Rac GTPase. Here we show that Rac and SCAR are recruited to cell wounds in the Drosophila repair model and are required for the proper formation and maintenance of the dynamic actomyosin ring formed at the wound periphery. Interestingly, we find that SCAR is recruited to wounds earlier than Rac and is still recruited to the wound periphery in the presence of a potent Rac inhibitor. We also show that while Rac is important for actin recruitment to the actomyosin ring, SCAR serves to organize the actomyosin ring and facilitate its anchoring to the overlying plasma membrane. These differing spatiotemporal recruitment patterns and wound repair phenotypes highlight the Rac-independent functions of SCAR and provide an exciting new context in which to investigate these newly uncovered SCAR functions.

Establishment and characterization of immortalized human vocal fold fibroblast cell lines

PURPOSE

Vocal fold scarring is abnormal scar tissue in the lamina propria layer of the vocal fold. To facilitate investigation of vocal fold scarring, we established and characterized immortalized human vocal fold fibroblast (iHVFF) cell lines.

METHODS

Human vocal fold fibroblasts were immortalized by introducing Simian virus 40 large T antigen (SV40TAg) by transfection. Successfully transfected fibroblasts were sorted using flow cytometry. Immunofluorescence cytochemistry and western blot were applied to analyze the expression of fibronectin, vimentin, alpha-smooth muscle actin (α-SMA) and fibroblast activation protein (FAP). Cell proliferation rate was measured by CCK-8 assay. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to analyze the mRNA expression level.

RESULTS

The iHVFFs continued to proliferate for more than 30 generations and appeared spindle-shaped. The expression of Vimentin and α-SMA were detected in both iHVFFs and primary fibroblasts, and enhanced expression of FAP was observed in iHVFFs. Furthermore, iHVFFs exhibited an increased proliferative capability compared with the primary fibroblasts. RT-qPCR results suggested that collagen type III alpha 1 chain (COL3A1), interleukin-6, cyclooxygenase 2 (COX2), hyaluronan synthase 2 (HAS2), hepatocyte growth factor (HGF) in the iHVFFs significantly increased, whereas transforming growth factor-β1 (TGF-β1), elastin and matrix metallopeptidase-1 (MMP-1) expression significantly downregulated. No differences in mRNA expression of α-SMA, fibronectin and collagen type I alpha 2 chain (COL1A2) were noted between iHVFFs and primary fibroblasts.

CONCLUSION

iHVFFs can be used as a novel tool cell for future researches on the mechanisms of pathogenesis and treatment of vocal fold scarring.

MiR-155-5p Aggravated Astrocyte Activation and Glial Scarring in a Spinal Cord Injury Model by Inhibiting Ndfip1 Expression and PTEN Nuclear Translocation

Central nervous injury and regeneration repair have always been a hot and difficult scientific questions in neuroscience, such as spinal cord injury (SCI) caused by a traffic accident, fall injury, and war. After SCI, astrocytes further migrate to the injured area and form dense glial scar through proliferation, which not only limits the infiltration of inflammatory cells but also affects axon regeneration. We aim to explore the effect and underlying mechanism of miR-155-5p overexpression promoted astrocyte activation and glial scarring in an SCI model. MiR-155-5p mimic (50 or 100 nm) was used to transfect CTX-TNA2 rat brain primary astrocyte cell line. MiR-155-5p antagonist and miR-155-5p agomir were performed to treat SCI rats. MiR-155-5p mimic dose-dependently promoted astrocyte proliferation, and inhibited cell apoptosis. MiR-155-5p overexpression inhibited nuclear PTEN expression by targeting Nedd4 family interacting protein 1 (Ndfip1). Ndfip1 overexpression reversed astrocyte activation which was induced by miR-155-5p mimic. Meanwhile, Ndfip1 overexpression abolished the inhibition effect of miR-155-5p mimic on PTEN nuclear translocation. In vivo, miR-155-5p silencing improved SCI rat locomotor function and promoted astrocyte activation and glial scar formation. And miR-155-5p overexpression showed the opposite results. MiR-155-5p aggravated astrocyte activation and glial scarring in a SCI model by targeting Ndfip1 expression and inhibiting PTEN nuclear translocation. These findings have ramifications for the development of miRNAs as SCI therapeutics.

Targeting Lysyl Oxidase as a Potential Therapeutic Approach to Reducing Fibrotic Scars Post-operatively: Its Biological Role in Post-Surgical Scar Development

Abdominal and pelvic surgery, or any surgical injury of the peritoneum, often leads to chronic abdominal adhesions that may lead to bowel obstruction, infertility, and pain. Current therapeutic strategies are usually ineffective, and the pathological mechanisms of the disease are unclear. Excess collagen cross-linking is a key mediator for extra-cellular matrix deposition and fibrogenesis. Lysyl oxidase is a key enzyme that catalyzes the formation of stabilizing cross-links in collagen. Dysregulation of Lysyl oxidase (Lox) expressing upregulates collagen cross-linking, leading ECM deposition. Tissue hypoxia during surgery induces molecular mechanisms and active transcription factors to promote the expression of several genes related to inflammation, oxidative stress, and fibrosis, such as transforming growth factor beta, and Lox. Studies have shown that targeting Lox improves clinical outcomes and fibrotic parameters in liver, lung, and myocardial fibrosis, therefore, Lox may be a potential drug target in the prevention of postsurgical adhesion.

The cardiac wound healing response to myocardial infarction

Myocardial infarction (MI) is defined as evidence of myocardial necrosis consistent with prolonged ischemia. In response to MI, the myocardium undergoes a series of wound healing events that initiate inflammation and shift to anti-inflammation before transitioning to tissue repair that culminates in scar formation to replace the region of the necrotic myocardium. The overall response to MI is determined by two major steps, the first of which is the secretion of proteases by infiltrating leukocytes to breakdown extracellular matrix (ECM) components, a necessary step to remove necrotic cardiomyocytes. The second step is the generation of new ECM that comprises the scar; and this step is governed by the cardiac fibroblasts as the major source of new ECM synthesis. The leukocyte component resides in the middle of the two-step process, contributing to both sides as the leukocytes transition from pro-inflammatory to anti-inflammatory and reparative cell phenotypes. The balance between the two steps determines the final quantity and quality of scar formed, which in turn contributes to chronic outcomes following MI, including the progression to heart failure. This review will summarize our current knowledge regarding the cardiac wound healing response to MI, primarily focused on experimental models of MI in mice. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Immune System Diseases > Molecular and Cellular Physiology.

Nature of β-1,3-Glucan-Exposing Features on Candida albicans Cell Wall and Their Modulation

Candida albicans exists as a commensal of mucosal surfaces and the gastrointestinal tract without causing pathology. However, this fungus is also a common cause of mucosal and systemic infections when antifungal immune defenses become compromised. The activation of antifungal host defenses depends on the recognition of fungal pathogen-associated molecular patterns (PAMPs), such as β-1,3-glucan. In C. albicans, most β-1,3-glucan is present in the inner cell wall, concealed by the outer mannan layer, but some β-1,3-glucan becomes exposed at the cell surface. In response to host signals, such as lactate, C. albicans induces the Xog1 exoglucanase, which shaves exposed β-1,3-glucan from the cell surface, thereby reducing phagocytic recognition. We show here that β-1,3-glucan is exposed at bud scars and punctate foci on the lateral wall of yeast cells, that this exposed β-1,3-glucan is targeted during phagocytic attack, and that lactate-induced masking reduces β-1,3-glucan exposure at bud scars and at punctate foci. β-1,3-Glucan masking depends upon protein kinase A (PKA) signaling. We reveal that inactivating PKA, or its conserved downstream effectors, Sin3 and Mig1/Mig2, affects the amounts of the Xog1 and Eng1 glucanases in the C. albicans secretome and modulates β-1,3-glucan exposure. Furthermore, perturbing PKA, Sin3, or Mig1/Mig2 attenuates the virulence of lactate-exposed C. albicans cells in Galleria. Taken together, the data are consistent with the idea that β-1,3-glucan masking contributes to Candida pathogenicity. IMPORTANCE Microbes that coexist with humans have evolved ways of avoiding or evading our immunological defenses. These include the masking by these microbes of their "pathogen-associated molecular patterns" (PAMPs), which are recognized as "foreign" and used to activate protective immunity. The commensal fungus Candida albicans masks the proinflammatory PAMP β-1,3-glucan, which is an essential component of its cell wall. Most of this β-1,3-glucan is hidden beneath an outer layer of the cell wall on these microbes, but some can become exposed at the fungal cell surface. Using high-resolution confocal microscopy, we examine the nature of the exposed β-1,3-glucan at C. albicans bud scars and at punctate foci on the lateral cell wall, and we show that these features are targeted by innate immune cells. We also reveal that downstream effectors of protein kinase A (Mig1/Mig2, Sin3) regulate the secretion of major glucanases, modulate the levels of β-1,3-glucan exposure, and influence the virulence of C. albicans in an invertebrate model of systemic infection. Our data support the view that β-1,3-glucan masking contributes to immune evasion and the virulence of a major fungal pathogen of humans.

Matrix Adhesiveness Regulates Myofibroblast Differentiation from Vocal Fold Fibroblasts in a Bio-orthogonally Cross-linked Hydrogel

Repeated mechanical and chemical insults cause an irreversible alteration of extracellular matrix (ECM) composition and properties, giving rise to vocal fold scarring that is refractory to treatment. Although it is well known that fibroblast activation to myofibroblast is the key to the development of the pathology, the lack of a physiologically relevant in vitro model of vocal folds impedes mechanistic investigations on how ECM cues promote myofibroblast differentiation. Herein, we describe a bio-orthogonally cross-linked hydrogel platform that recapitulates the alteration of matrix adhesiveness due to enhanced fibronectin deposition when vocal fold wound healing is initiated. The synthetic ECM (sECM) was established via the cycloaddition reaction of tetrazine (Tz) with slow (norbornene, Nb)- and fast (trans-cyclooctene, TCO)-reacting dienophiles. The relatively slow Tz-Nb ligation allowed the establishment of the covalent hydrogel network for 3D cell encapsulation, while the rapid and efficient Tz-TCO reaction enabled precise conjugation of the cell-adhesive RGDSP peptide in the hydrogel network. To mimic the dynamic changes of ECM composition during wound healing, RGDSP was conjugated to cell-laden hydrogel constructs via a diffusion-controlled bioorthognal ligation method 3 days post encapsulation. At a low RGDSP concentration (0.2 mM), fibroblasts residing in the hydrogel remained quiescent when maintained in transforming growth factor beta 1 (TGF-β1)-conditioned media. However, at a high concentration (2 mM), RGDSP potentiated TGF-β1-induced myofibroblast differentiation, as evidenced by the formation of an actin cytoskeleton network, including F-actin and alpha-smooth muscle actin. The RGDSP-driven fibroblast activation to myofibroblast was accompanied with an increase in the expression of wound healing-related genes, the secretion of profibrotic cytokines, and matrix contraction required for tissue remodeling. This work represents the first step toward the establishment of a 3D hydrogel-based cellular model for studying myofibroblast differentiation in a defined niche associated with vocal fold scarring.

The joint action of unfolded protein response, circZc3h4, and circRNA Scar in procymidone-induced testicular injury in adolescent mice

Procymidone (PCM) is a low toxicity fungicide, and an endocrine-disrupting chemical (EDC) that particularly damages the reproductive system of male vertebrates. In present study, adolescent mice in control, low-, medium-, and high-dose groups were orally administered 0 (equal volume of soybean oil), 50, 100, and 200 mg/kg/day PCM, respectively, for 21 days. Additionally, a three-dimensional culture of mouse testes was performed in vitro, and the control, low dose (0.33 × 10^-5  M), medium dose (1 × 10^-5  M), and high dose (3 × 10^-5  M) PCM groups were established. We have found that, under both in vivo and in vitro conditions, all doses of PCM caused damage to mouse testes. Moreover, the levels of circZc3h4 RNA and Zc3h4 decreased while miR-212 increased in all treatment groups, with a corresponding rise in circRNA Scar and fall in Atp5b, compared to those in the control group, and all the changes showed a dose-response relationship. Besides, we have identified that low doses of PCM could activate the Ire1-Xbp1 pathway, whereas the medium and high doses activated the Perk-Elf2α-Atf4, Ire1-Xbp1, and Atf6 pathways. And it is, therefore, speculated that the unfolded protein response (UPR), circZc3h4 and circRNA Scar may have taken joint action in testicular injury in adolescent mice induced by PCM at the no observed adverse effect level (NOAEL, 100 mg/kg/day) and below NOAEL doses.

Understanding Scarring in the Oral Mucosa

Significance: Skin inevitably heals with the formation of a fibrotic scar. Patients affected by skin scarring suffer from long-term psychological and physical burdens. Recent Advances: Since the discovery of fetal scarless skin-wound healing, research has hoped to identify and mimic scarless healing for adult skin. Oral mucosa healing in adults provides the closest example to fetal scarless healing. Injuries to the oral mucosa heal with very minimal scarring. Understanding the mechanisms through which this process occurs may bring us closer to achieving scarless healing in adults. Critical Issues: In this review, we summarize the current evidence that illustrates distinct mechanisms involved in oral mucosal healing. We discuss the role of the oral niche in contributing to wound repair. The intrinsic properties of immune cells, fibroblasts, and keratinocytes within the oral mucosa that support regenerative repair are provided. We highlight the contribution of cytokines, growth factors, and chemokine secretion in permitting a scarless mucosal environment. Furthermore, we discuss the role of stem cell-like progenitor populations in the mucosa that may contribute to wound healing. We also provide suggestions for future studies that are needed to achieve scarless healing in adults. Future Directions: Many characteristics of the oral mucosa have been shown to contribute to decreased scarring, but the specific mechanism(s) is unclear. Advancing our understanding of oral healing may yield therapeutic therapies that can be used to overcome dermal scarring.

Perivascular Mesenchymal Stem/Stromal Cells, an Immune Privileged Niche for Viruses?

Mesenchymal stem cells (MSCs) play a critical role in response to stress such as infection. They initiate the removal of cell debris, exert major immunoregulatory activities, control pathogens, and lead to a remodeling/scarring phase. Thus, host-derived ‘danger’ factors released from damaged/infected cells (called alarmins, e.g., HMGB1, ATP, DNA) as well as pathogen-associated molecular patterns (LPS, single strand RNA) can activate MSCs located in the parenchyma and around vessels to upregulate the expression of growth factors and chemoattractant molecules that influence immune cell recruitment and stem cell mobilization. MSC, in an ultimate contribution to tissue repair, may also directly trans- or de-differentiate into specific cellular phenotypes such as osteoblasts, chondrocytes, lipofibroblasts, myofibroblasts, Schwann cells, and they may somehow recapitulate their neural crest embryonic origin. Failure to terminate such repair processes induces pathological scarring, termed fibrosis, or vascular calcification. Interestingly, many viruses and particularly those associated to chronic infection and inflammation may hijack and polarize MSC’s immune regulatory activities. Several reports argue that MSC may constitute immune privileged sanctuaries for viruses and contributing to long-lasting effects posing infectious challenges, such as viruses rebounding in immunocompromised patients or following regenerative medicine therapies using MSC. We will herein review the capacity of several viruses not only to infect but also to polarize directly or indirectly the functions of MSC (immunoregulation, differentiation potential, and tissue repair) in clinical settings.

Topical Losartan and Corticosteroid Additively Inhibit Corneal Stromal Myofibroblast Generation and Scarring Fibrosis After Alkali Burn Injury

Purpose

To evaluate the efficacy of losartan and prednisolone acetate in inhibiting corneal scarring fibrosis after alkali burn injury in rabbits.

Methods

Sixteen New Zealand White rabbits were included. Alkali injuries were produced using 1N sodium hydroxide on a 5-mm diameter Whatman #1 filter paper for 1 minute. Four corneas in each group were treated six times per day for 1 month with 50 µL of (1) 0.8 mg/mL losartan in balanced salt solution (BSS), (2) 1% prednisolone acetate, (3) combined 0.8 mg/mL losartan and 1% prednisolone acetate, or (4) BSS. Area of opacity and total opacity were analyzed in standardized slit-lamp photos with ImageJ. Corneas in both groups were cryofixed in Optimal cutting temperature (OCT) compound at 1 month after surgery, and immunohistochemistry was performed for alpha-smooth muscle actin (α-SMA) and keratocan or transforming growth factor β1 and collagen type IV with ImageJ quantitation.

Results

Combined topical losartan and prednisolone acetate significantly decreased slit-lamp opacity area and intensity, as well as decreased stromal myofibroblast α-SMA area and intensity of staining per section and confined myofibroblasts to only the posterior stroma with repopulation of the anterior and mid-stroma with keratocan-positive keratocytes after 1 month of treatment. Corneal fibroblasts produced collagen type IV not associated with basement membranes, and this production was decreased by topical losartan.

Conclusions

Combined topical losartan and prednisolone acetate decreased myofibroblast-associated fibrosis after corneal alkali burns that produced full-thickness injury, including corneal endothelial damage. Increased dosages and duration of treatment may further decrease scarring fibrosis.

Translational Relevance

Topical losartan and prednisolone acetate decrease myofibroblast-mediated scarring fibrosis after corneal injury.

Spatiotemporal Dynamics of the Molecular Expression Pattern and Intercellular Interactions in the Glial Scar Response to Spinal Cord Injury

Nerve regeneration in adult mammalian spinal cord is poor because of the lack of intrinsic regeneration of neurons and extrinsic factors - the glial scar is triggered by injury and inhibits or promotes regeneration. Recent technological advances in spatial transcriptomics (ST) provide a unique opportunity to decipher most genes systematically throughout scar formation, which remains poorly understood. Here, we first constructed the tissue-wide gene expression patterns of mouse spinal cords over the course of scar formation using ST after spinal cord injury from 32 samples. Locally, we profiled gene expression gradients from the leading edge to the core of the scar areas to further understand the scar microenvironment, such as neurotransmitter disorders, activation of the pro-inflammatory response, neurotoxic saturated lipids, angiogenesis, obstructed axon extension, and extracellular structure re-organization. In addition, we described 21 cell transcriptional states during scar formation and delineated the origins, functional diversity, and possible trajectories of subpopulations of fibroblasts, glia, and immune cells. Specifically, we found some regulators in special cell types, such as Thbs1 and Col1a2 in macrophages, CD36 and Postn in fibroblasts, Plxnb2 and Nxpe3 in microglia, Clu in astrocytes, and CD74 in oligodendrocytes. Furthermore, salvianolic acid B, a blood-brain barrier permeation and CD36 inhibitor, was administered after surgery and found to remedy fibrosis. Subsequently, we described the extent of the scar boundary and profiled the bidirectional ligand-receptor interactions at the neighboring cluster boundary, contributing to maintain scar architecture during gliosis and fibrosis, and found that GPR37L1_PSAP, and GPR37_PSAP were the most significant gene-pairs among microglia, fibroblasts, and astrocytes. Last, we quantified the fraction of scar-resident cells and proposed four possible phases of scar formation: macrophage infiltration, proliferation and differentiation of scar-resident cells, scar emergence, and scar stationary. Together, these profiles delineated the spatial heterogeneity of the scar, confirmed the previous concepts about scar architecture, provided some new clues for scar formation, and served as a valuable resource for the treatment of central nervous system injury.

Potential therapeutic role of microvesicles derived from mesenchymal stem cells and platelet-rich plasma in murine burn wound healing: scar regulation and antioxidant mechanism

BACKGROUND

Microvesicles (MVs) derived from mesenchymal stem cells exhibited an emerging promising therapy in many animal model diseases. Post-burn scars represent one of the significant challenges in wound healing processes. The present study investigated the possible role of MVs derived from mesenchymal stem cells vs. platelet-rich plasma (PRP) in murine burn wound healing.

MATERIALS AND METHODS

Wistar rats (n = 40) were assigned into four equal groups (control, burn, burn + PRP, burn + MVs). Small-sized burns were induced, morphologically followed for 3 weeks, then rats were sacrificed and skin lesions were analysed biochemically and immunohistochemically.

RESULTS

Both MVs and PRP modulated the burn healing process with better results in the MVs group than in PRP. MVs significantly (p < 0.05) accelerated burn wound size healing and dramatically modulated tissue interleukin (IL)-10, IL-6, and hyaluronidase. Both MVs and PRP significantly downregulated gene expression of miRNA203 and alpha smooth muscle actin and immunoblotting analysis of matrix metalloproteinases 3 and transforming growth factor beta compared with the burn group. The immune-staining intensity of tumour necrosis factor alpha was dramatically reversed in the MVs group compared with the burn group, whereas that of connective tissue growth factor, collagen I and III was significantly reduced in both groups. The antioxidant Nrf2 immune-staining intensity had been dramatically enhanced particularly in MVs.

CONCLUSIONS

Microvesicles derived from mesenchymal stem cells and PRP may improve burn wound healing via regulating scar formation and antioxidant mechanism.

A bio-functional polymer that prevents retinal scarring through modulation of NRF2 signalling pathway

One common cause of vision loss after retinal detachment surgery is the formation of proliferative and contractile fibrocellular membranes. This aberrant wound healing process is mediated by epithelial-mesenchymal transition (EMT) and hyper-proliferation of retinal pigment epithelial (RPE) cells. Current treatment relies primarily on surgical removal of these membranes. Here, we demonstrate that a bio-functional polymer by itself is able to prevent retinal scarring in an experimental rabbit model of proliferative vitreoretinopathy. This is mediated primarily via clathrin-dependent internalisation of polymeric micelles, downstream suppression of canonical EMT transcription factors, reduction of RPE cell hyper-proliferation and migration. Nuclear factor erythroid 2-related factor 2 signalling pathway was identified in a genome-wide transcriptomic profiling as a key sensor and effector. This study highlights the potential of using synthetic bio-functional polymer to modulate RPE cellular behaviour and offers a potential therapy for retinal scarring prevention.

Network modeling predicts personalized gene expression and drug responses in valve myofibroblasts cultured with patient sera

Aortic valve stenosis (AVS) patients experience pathogenic valve leaflet stiffening due to excessive extracellular matrix (ECM) remodeling. Numerous microenvironmental cues influence pathogenic expression of ECM remodeling genes in tissue-resident valvular myofibroblasts, and the regulation of complex myofibroblast signaling networks depends on patient-specific extracellular factors. Here, we combined a manually curated myofibroblast signaling network with a data-driven transcription factor network to predict patient-specific myofibroblast gene expression signatures and drug responses. Using transcriptomic data from myofibroblasts cultured with AVS patient sera, we produced a large-scale, logic-gated differential equation model in which 11 biochemical and biomechanical signals were transduced via a network of 334 signaling and transcription reactions to accurately predict the expression of 27 fibrosis-related genes. Correlations were found between personalized model-predicted gene expression and AVS patient echocardiography data, suggesting links between fibrosis-related signaling and patient-specific AVS severity. Further, global network perturbation analyses revealed signaling molecules with the most influence over network-wide activity, including endothelin 1 (ET1), interleukin 6 (IL6), and transforming growth factor β (TGFβ), along with downstream mediators c-Jun N-terminal kinase (JNK), signal transducer and activator of transcription (STAT), and reactive oxygen species (ROS). Lastly, we performed virtual drug screening to identify patient-specific drug responses, which were experimentally validated via fibrotic gene expression measurements in valvular interstitial cells cultured with AVS patient sera and treated with or without bosentan-a clinically approved ET1 receptor inhibitor. In sum, our work advances the ability of computational approaches to provide a mechanistic basis for clinical decisions including patient stratification and personalized drug screening.

E8002 Reduces Adhesion Formation and Improves Joint Mobility in a Rat Model of Knee Arthrofibrosis

Knee arthrofibrosis is a common complication of knee surgery, caused by excessive scar tissue, which results in functional disability. However, no curative treatment has been established. E8002 is an anti-adhesion material that contains L-ascorbic acid, an antioxidant. We aimed to evaluate the efficacy of E8002 for the prevention of knee arthrofibrosis in a rat model, comprising injury to the surface of the femur and quadriceps muscle 1 cm proximal to the patella. Sixteen male, 8-week-old Sprague Dawley rats were studied: in the Adhesion group, haemorrhagic injury was induced to the quadriceps and bone, and in the E8002 group, an adhesion-preventing film was implanted between the quadriceps and femur after injury. Six weeks following injury, the restriction of knee flexion owing to fibrotic scarring had not worsened in the E8002 group but had worsened in the Adhesion group. The area of fibrotic scarring was smaller in the E8002 group than in the Adhesion group (p < 0.05). In addition, the numbers of fibroblasts (p < 0.05) and myofibroblasts (p < 0.01) in the fibrotic scar were lower in the E8002 group. Thus, E8002 reduces myofibroblast proliferation and fibrotic scar formation and improves the range of motion of the joint in a model of knee injury.

Disassembly and Mislocalization of AQP4 in Incipient Scar Formation after Experimental Stroke

There is an urgent need to better understand the mechanisms involved in scar formation in the brain. It is well known that astrocytes are critically engaged in this process. Here, we analyze incipient scar formation one week after a discrete ischemic insult to the cerebral cortex. We show that the infarct border zone is characterized by pronounced changes in the organization and subcellular localization of the major astrocytic protein AQP4. Specifically, there is a loss of AQP4 from astrocytic endfoot membranes that anchor astrocytes to pericapillary basal laminae and a disassembly of the supramolecular AQP4 complexes that normally abound in these membranes. This disassembly may be mechanistically coupled to a downregulation of the newly discovered AQP4 isoform AQP4ex. AQP4 has adhesive properties and is assumed to facilitate astrocyte mobility by permitting rapid volume changes at the leading edges of migrating astrocytes. Thus, the present findings provide new insight in the molecular basis of incipient scar formation.

Corneal Opacity: Cell Biological Determinants of the Transition From Transparency to Transient Haze to Scarring Fibrosis, and Resolution, After Injury

Purpose

To highlight the cellular, matrix, and hydration changes associated with opacity that occurs in the corneal stroma after injury.

Methods

Review of the literature.

Results

The regulated transition of keratocytes to corneal fibroblasts and myofibroblasts, and of bone marrow-derived fibrocytes to myofibroblasts, is in large part modulated by transforming growth factor beta (TGFβ) entry into the stroma after injury to the epithelial basement membrane (EBM) and/or Descemet's membrane. The composition, stoichiometry, and organization of the stromal extracellular matrix components and water is altered by corneal fibroblast and myofibroblast production of large amounts of collagen type I and other extracellular matrix components-resulting in varying levels of stromal opacity, depending on the intensity of the healing response. Regeneration of EBM and/or Descemet's membrane, and stromal cell production of non-EBM collagen type IV, reestablishes control of TGFβ entry and activity, and triggers TGFβ-dependent myofibroblast apoptosis. Eventually, corneal fibroblasts also disappear, and repopulating keratocytes reorganize the disordered extracellular matrix to reestablish transparency.

Conclusions

Injuries to the cornea produce varying amounts of corneal opacity depending on the magnitude of cellular and molecular responses to injury. The EBM and Descemet's membrane are key regulators of stromal cellularity through their modulation of TGFβ. After injury to the cornea, depending on the severity of the insult, and possibly genetic factors, trace opacity to severe scarring fibrosis develops. Stromal cellularity, and the functions of different cell types, are the major determinants of the level of the stromal opacity.