Neuroinflammatory Mechanisms of Connective Tissue Fibrosis: Targeting Neurogenic and Mast Cell Contributions

Immune Cells in Subretinal Wound Healing and Fibrosis

The subretinal space is devoid of any immune cells under normal conditions and is an immune privileged site. When photoreceptors and/or retinal pigment epithelial cells suffer from an injury, a wound healing process will be initiated. Retinal microglia and the complement system, as the first line of retinal defense, are activated to participate in the wound healing process. If the injury is severe or persists for a prolonged period, they may fail to heal the damage and circulating immune cells will be summoned leading to chronic inflammation and abnormal wound healing, i.e., subretinal or intraretinal fibrosis, a sight-threatening condition frequently observed in rhematogenous retinal detachment, age-related macular degeneration and recurrent uveoretinitis. Here, we discussed the principles of subretinal wound healing with a strong focus on the conditions whereby the damage is beyond the healing capacity of the retinal defense system and highlighted the roles of circulating immune cells in subretinal wound healing and fibrosis.

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.

Myofibroblasts: Function, Formation, and Scope of Molecular Therapies for Skin Fibrosis

Myofibroblasts are contractile, α-smooth muscle actin-positive cells with multiple roles in pathophysiological processes. Myofibroblasts mediate wound contractions, but their persistent presence in tissues is central to driving fibrosis, making them attractive cell targets for the development of therapeutic treatments. However, due to shared cellular markers with several other phenotypes, the specific targeting of myofibroblasts has long presented a scientific and clinical challenge. In recent years, myofibroblasts have drawn much attention among scientific research communities from multiple disciplines and specialisations. As further research uncovers the characterisations of myofibroblast formation, function, and regulation, the realisation of novel interventional routes for myofibroblasts within pathologies has emerged. The research community is approaching the means to finally target these cells, to prevent fibrosis, accelerate scarless wound healing, and attenuate associated disease-processes in clinical settings. This comprehensive review article describes the myofibroblast cell phenotype, their origins, and their diverse physiological and pathological functionality. Special attention has been given to mechanisms and molecular pathways governing myofibroblast differentiation, and updates in molecular interventions.

Sesquiterpene-Loaded Co-Polymer Hybrid Nanoparticle Effects on Human Mast Cell Surface Receptor Expression, Granule Contents, and Degranulation

Biodegradable polymeric nanoparticles (NPs) such as poly(lactic-co-glycolic acid) (PLGA) and polyvinyl alcohol (PVA) have been used as drug delivery systems for natural and synthetic compounds and are designed to control the loading and release of biodegradable materials to target cells, tissues, and organs. Eremophilane-type sesquiterpenes have anti-inflammatory properties but are lipophilic, cytotoxic, and not biocompatible with many cells. To determine whether biodegradable PLGA/PVA could improve the biocompatibility of sesquiterpenes, sesquiterpene-loaded NPs were synthesized and their effects on human mast cells (LAD2), the major effector cells of allergic inflammation, were determined. NPs composed of PLGA/PVA and two types of sesquiterpenes (fukinone, PLGA/PVA-21 and 10βH-8α,12-epidioxyeremophil-7(11)-en-8β-ol, PLGA/PVA-22) were produced using a microfluidic synthesis method. The NPs’ size distribution and morphology were evaluated by dynamic light scattering and cryogenic transmission electron microscopy (TEM). PLGA/PVA-21 and PLGA/PVA-22 were 60 to 70 nm and were readily internalized by LAD2 as shown by flow cytometry, fluorescence microscopy, and TEM. While unencapsulated sesquiterpenes decreased LAD2 cell viability by 20%, PLGA/PVA-21 and PLGA/PVA-22 did not alter LAD2 viability, showing that encapsulation improved the biocompatibility of the sesquiterpenes. PLGA/PVA-21 and PLGA/PVA-22 decreased the expression of genes encoding the subunits of the high affinity immunoglobulin E receptor (FcεR1α, FcεR1β, FcεR1γ) and the stem cell factor receptor (Kit,), suggesting that hybrid NPs could alter mast cell responses to antigens and shift their maturation. Similarly, PLGA/PVA-21 and PLGA/PVA-22 inhibited tryptase expression but had no effect on chymase expression, thereby promoting a shift to the tryptase-positive phenotype (MC_T). Lastly, PLGA/PVA-21 and PLGA/PVA-22 inhibited mast cell degranulation when the LAD2 cells were activated by IgE crosslinking and FcεRI. Overall, our results suggest that PLGA/PVA-21 and PLGA/PVA-22 alter human mast cell phenotype and activation without modifying viability, making them a more biocompatible approach than treating cells with sesquiterpenes alone.

Macrophage migration inhibitory factor activates the inflammatory response in joint capsule fibroblasts following post-traumatic joint contracture

Objectives: Joint capsule fibrosis caused by excessive inflammation leading to post-traumatic joint contracture (PTJC). Fibroblasts trigger inflammation under the challenge of various proinflammatory cytokines. Macrophage migration inhibitory factor (MIF) is a prominent proinflammatory cytokine involved in inflammation- and fibrosis-associated pathophysiology, we investigated the role of MIF in PTJC.

Methods: Using rat PTJC model and fibroblast inflammation model, we detected MIF expression in posterior joint capsule. Primary joint capsule fibroblasts (JFs) were used to investigate the effects of MIF on cell proliferation, migration and proinflammatory cytokines production. The mechanism of JF-mediated events was evaluated by qRT-PCR, western blot and immunoprecipitation. We screened the mRNA expression profile to identify gene candidates that mediate the effect of MIF on JFs.

Results: MIF increased in posterior joint capsule following PTJC and co-localized with fibroblasts. Injection of MIF inhibitor significantly suppressed joint capsule inflammation and fibrosis. In vitro, MIF promoted JF proliferation, migration, and inflammation by regulating mitogen-activated protein kinase/nuclear factor-κB pathway through coupling with CD74. Transcriptome analysis revealed that lipid metabolism-related factors Pla2g2a, Angptl4, and Sgpp2, downstream of MIF/CD74, were potentially implicated in JF inflammation.

Conclusion: MIF/CD74 axis elicited JF inflammation and may provide new therapeutic targets for joint capsule fibrosis in PTJC.

Migraines and keloids: a 15-year Taiwan claim database analysis

Background

Fibroproliferative lesions with intractable pruritus, pain and hyperesthesia that cause uncontrolled scar growth are known as keloids. Migraines are common upsetting headache disorders characterised by frequent recurrence and attacks aggravated by physical activity. Both keloids and migraines can cause physical exhaustion and discomfort in patients; they have similar pathophysiological pathways, that is, the transforming growth factor-β1 gene and neurogenic inflammation.

Objective

To investigate subsequent development of migraines in patients with keloids.

Methods

Data were retrieved from the Taiwan National Health Insurance Research Database. The keloids group included patients aged 20 years and older with a recent diagnosis of keloids(n=9864). The non-keloids group included patients without keloids matched for gender and age at 1–4 ratio (n=39 456). Migraine risk between groups was measured by Cox proportional hazards regression models. Incidence rates and hazard ratios were calculated.

Results

During the study period, 103 keloids patients and 323 non-keloids patients developed migraines. The keloids patients had a 2.29-fold greater risk of developing migraines compared with the non-keloids group after adjustment for covariates (1.81 vs 0.55 per 1000 person-years, respectively). In the keloids group, female or patients younger than 50 years were prone to developing migraines.

Conclusion

The higher tendency to develop migraines in the keloids group in comparison with the non-keloids group suggests that keloids could be a predisposing risk factor for migraine development in adults. Keloids patients who complain of headaches should be examined for migraines.

PrEvention of posttraumatic contractuRes with Ketotifen 2 (PERK 2) - protocol for a multicenter randomized clinical trial

Background

Injuries and resulting stiffness around joints, especially the elbow, have huge psychological effects by reducing quality of life through interference with normal daily activities such as feeding, dressing, grooming, and reaching for objects. Over the last several years and through numerous research results, the myofibroblast-mast cell-neuropeptide axis of fibrosis had been implicated in post-traumatic joint contractures. Pre-clinical models and a pilot randomized clinical trial (RCT) demonstrated the feasibility and safety of using Ketotifen Fumarate (KF), a mast cell stabilizer to prevent elbow joint contractures. This study aims to evaluate the efficacy of KF in reducing joint contracture severity in adult participants with operately treated elbow fractures and/or dislocations.

Methods/design

A Phase III randomized, controlled, double-blinded multicentre trial with 3 parallel groups (KF 2 mg or 5 mg or lactose placebo twice daily orally for 6 weeks). The study population consist of adults who are at least 18 years old and within 7 days of injury. The types of injuries are distal humerus (AO/OTA type 13) and/or proximal ulna and/or proximal radius fractures (AO/OTA type 2 U1 and/or 2R1) and/or elbow dislocations (open fractures with or without nerve injury may be included). A stratified randomization scheme by hospital site will be used to assign eligible participants to the groups in a 1:1:1 ratio. The primary outcome is change in elbow flexion-extension range of motion (ROM) arc from baseline to 12 weeks post-randomization. The secondary outcomes are changes in ROM from baseline to 6, 24 & 52 weeks, PROMs at 2, 6, 12, 24 & 52 weeks and impact of KF on safety including serious adverse events and fracture healing. Descriptive analysis for all outcomes will be reported and ANCOVA be used to evaluate the efficacy KF over lactose placebo with respect to the improvement in ROM.

Discussion

The results of this study will provide evidence for the use of KF in reducing post-traumatic joint contractures and improving quality of life after joint injuries.

Trial registration

This study was prospectively registered (July 10, 2018) with ClinicalTrials.gov reference: NCT03582176.

Adult Human Dermal Progenitor Cell Transplantation Modulates the Functional Outcome of Split-Thickness Skin Xenografts

Following full-thickness skin injuries, epithelialization of the wound is essential. The standard of care to achieve this wound "closure" in patients is autologous split-thickness skin grafting (STSG). However, patients living with STSGs report significant chronic impairments leading to functional deficiencies such as itch, altered sensation, fragility, hypertrophic scarring, and contractures. These features are attributable to the absence of functional dermis combined with the formation of disorganized fibrotic extracellular matrix. Recent work has demonstrated the existence of dermal progenitor cells (DPCs) residing within hair follicles that function to continuously regenerate mesenchymal tissue. The present work examines whether cultured DPCs could regenerate dermis within an STSG and improve overall graft function. Adult human DPCs were transplanted into a full-thickness skin wound in immune-compromised mice and closed with a human STSG. At 3 months, human DPCs (hDPCs) had successfully integrated into the xenograft and differentiated into various regionally specified phenotypes, improving both viscoelastic properties of the graft and mitigating pruritus.

Pathological mechanisms and therapeutic outlooks for arthrofibrosis

Arthrofibrosis is a fibrotic joint disorder that begins with an inflammatory reaction to insults such as injury, surgery and infection. Excessive extracellular matrix and adhesions contract pouches, bursae and tendons, cause pain and prevent a normal range of joint motion, with devastating consequences for patient quality of life. Arthrofibrosis affects people of all ages, with published rates varying. The risk factors and best management strategies are largely unknown due to a poor understanding of the pathology and lack of diagnostic biomarkers. However, current research into the pathogenesis of fibrosis in organs now informs the understanding of arthrofibrosis. The process begins when stress signals stimulate immune cells. The resulting cascade of cytokines and mediators drives fibroblasts to differentiate into myofibroblasts, which secrete fibrillar collagens and transforming growth factor-β (TGF-β). Positive feedback networks then dysregulate processes that normally terminate healing processes. We propose two subtypes of arthrofibrosis occur: active arthrofibrosis and residual arthrofibrosis. In the latter the fibrogenic processes have resolved but the joint remains stiff. The best therapeutic approach for each subtype may differ significantly. Treatment typically involves surgery, however, a pharmacological approach to correct dysregulated cell signalling could be more effective. Recent research shows that myofibroblasts are capable of reversing differentiation, and understanding the mechanisms of pathogenesis and resolution will be essential for the development of cell-based treatments. Therapies with significant promise are currently available, with more in development, including those that inhibit TGF-β signalling and epigenetic modifications. This review focuses on pathogenesis of sterile arthrofibrosis and therapeutic treatments.

Curbing Inflammation in Multiple Sclerosis and Endometriosis: Should Mast Cells Be Targeted?

Inflammatory diseases and conditions can arise due to responses to a variety of external and internal stimuli. They can occur acutely in response to some stimuli and then become chronic leading to tissue damage and loss of function. While a number of cell types can be involved, mast cells are often present and can be involved in the acute and chronic processes. Recent studies in porcine and rabbit models have supported the concept of a central role for mast cells in a “nerve-mast cell-myofibroblast axis” in some inflammatory processes leading to fibrogenic outcomes. The current review is focused on the potential of extending aspects of this paradigm into treatments for multiple sclerosis and endometriosis, diseases not usually thought of as having common features, but both are reported to have activation of mast cells involved in their respective disease processes. Based on the discussion, it is proposed that targeting mast cells in these diseases, particularly the early phases, may be a fruitful avenue to control the recurring inflammatory exacerbations of the conditions.