Pleiotropic FTY720 Is a Specific and Potent Therapy for Hypertrophic Scars

Melatonin inhibits fibroblast cell functions and hypertrophic scar formation by enhancing autophagy through the MT2 receptor-inhibited PI3K/Akt /mTOR signaling

Hypertrophic scar (HS) is a fibrotic skin condition and characterized by abnormal proliferation of myofibroblasts and accumulation of extracellular matrix. Melatonin, an endogenous hormone, can alleviate fibrosis in multiple models of diseases. This study examined the effect of melatonin on fibrosis in primary fibroblasts from human HS (HSFs) and a rabbit ear model and potential mechanisms. Melatonin treatment significantly decreased the migration and contraction capacity, collagen and α-smooth muscle actin (α-SMA) production in HSFs. RNA-sequencing and bioinformatic analyses indicated that melatonin modulated the expression of genes involved in autophagy and oxidative stress. Mechanistically, melatonin treatment attenuated the AKT/mTOR activation through affecting the binding of MT2 receptor with PI3K to enhance autophagy, decreasing fibrogenic factor production in HSFs. Moreover, melatonin treatment inhibited HS formation in rabbit ears by enhancing autophagy. The anti-fibrotic effects of melatonin were abrogated by treatment with an autophagy inhibitor (3-methyladenine, 3-MA), an Akt activator (SC79), or an MT2 selective antagonist (4-phenyl-2propionamidotetralin, 4-P-PDOT). Therefore, melatonin may be a potential drug for prevention and treatment of HS.

Pleiotropic effect of intramucosal injection of FTY720 on angiogenesis and tissue healing after free gingival graft surgery: a comparative experimental study in rabbits

OBJECTIVES

Free gingival graft surgery is the gold standard for increasing the size of keratinized tissue. Blood supply in the recipient site is critical for healing. Therefore, in this study, the effect of FTY720 on angiogenesis, healing, and scar tissue presence following free gingival graft surgery is investigated.

MATERIALS AND METHODS

Surgeries were performed on 10 New Zealand white rabbits. Rabbits were randomly assigned to two groups. In the experimental group, immediately after surgery, 2 and 4 days later, FTY-720 was injected into the tissue surrounding the recipient site. In the control group, the same frequency of placebo vehicle was injected. After 30 days, tissue samples were assessed histologically and histomorphometrically.

RESULTS

The blood vessel count (P < 0.000) and rete ridge formation (P < 0.05) in the experimental group were significantly higher, while the epithelial thickness was lower in this group (P < 0.000). There was no significant difference in the percentage of regions occupied by collagen fibres between the groups (P = 0.987). Furthermore, a significant and negative relationship between epithelial thickness and blood vessel count was shown (Pearson correlation coefficient =  - 0.917).

CONCLUSIONS

The findings indicate that the angiogenic effects of FTY-720 in the recipient site of free gingival graft can be employed to promote tissue healing and reduce scar tissue presence.

CLINICAL RELEVANCE

A significant decrease in epithelial thickness and increase in angiogenesis as well as rete ridge formation score in the FTY-720 group were shown, which can be translated into improved tissue healing and less presence of scar tissue.

FTY720 in immuno-regenerative and wound healing technologies for muscle, epithelial and bone regeneration

In 2010, the FDA approved the administration of FTY720, S1P lipid mediator, as a therapy to treat relapsing forms of multiple sclerosis. FTY720 was found to sequester pro-inflammatory lymphocytes within the lymph node, preventing them from causing injury to the central nervous system due to inflammation. Studies harnessing the anti-inflammatory properties of FTY720 as a pro-regenerative strategy in wound healing of muscle, bone and mucosal injuries are currently being performed. This in-depth review discusses the current regenerative impact of FTY720 due to its anti-inflammatory effect stratified into an assessment of wound regeneration in the muscular, skeletal, and epithelial systems. The regenerative effect of FTY720 in vivo was characterized in three animal models, with differing delivery mechanisms emerging in the last 20 years. In these studies, local delivery of FTY720 was found to increase pro-regenerative immune cell phenotypes (neutrophils, macrophages, monocytes), vascularization, cell proliferation and collagen deposition. Delivery of FTY720 to a localized wound environment demonstrated increased bone, muscle, and mucosal regeneration through changes in gene and cytokine production primarily by controlling the local immune cell phenotypes. These changes in gene and cytokine production reduced the inflammatory component of wound healing and increased the migration of pro-regenerative cells (neutrophils and macrophages) to the wound site. The application of FTY720 delivery using a biomaterial has demonstrated the ability of local delivery of FTY720 to promote local wound healing leveraging an immunomodulatory mechanism.

FTY720 administration results in a M2 associated immunoregulatory effect that positively influences the outcome of alveolar bone repair outcome in mice

The alveolar bone repair process may be influenced by multiple local and systemic factors, which include immune system cells and mediators. Macrophages allegedly play important roles in the repair process, and the transition of an initial inflammatory M1 profile into a pro-reparative M2 profile theoretically contributes to a favorable repair outcome. In this context, considering immunoregulatory molecules as potential targets for improving bone repair, this study evaluated the role of the immunoregulatory molecule FTY720, previously described to favor the development of the M2 phenotype, in the process of alveolar bone healing in C57Bl/6 (WT) mice. Experimental groups submitted to tooth extraction and maintained under control conditions or treated with FTY720 were evaluated by microtomographic (μCT), histomorphometric, immunohistochemical and molecular analysis to characterize healing and host response features at 0, 1, 3, 7 and 14 days. Our results demonstrated that the FTY720 group presented higher bone tissue density, higher bone tissue volume, greater tissue volume fraction, greater number and thickness of trabeculae and a higher number of osteoblasts and osteoclasts than the control group. Accordingly, the bone markers BMP2, BMP7, ALPL, SOST and RANK mRNA expressions increased in the FTY720 treated group. Furthermore, the levels of FIZZ, ARG2 and IL-10 mRNA increased in the FTY720 group together with the presence of CD206⁺ cells, suggesting that the boost of bone formation mediated by FTY720 involves an increased polarization and activity of M2 macrophages in healing sites. Thus, our results demonstrate that FTY720 favored the process of alveolar bone repair, probably trough a strengthened M2 response, associated with an increased expression of markers osteogenic differentiation and activity markers. Immunoregulatory strategies based in the modulation of macrophage polarization profile can comprise effective tools to improve the bone repair process.

Lycorine Inhibits Hypertrophic Scar Formation by Inducing ROS-Mediated Apoptosis

Background: Hypertrophic scar (HS) is a fibrotic cutaneous disease with few effective therapies. Lycorine is a drug with pro-apoptotic ability and anti-fibrosis potential. This study aimed to test whether lycorine could trigger the apoptosis of hypertrophic scar fibroblasts (HSFs) to inhibit HS formation.

Methods: The proapoptotic and anti-fibrosis effects of lycorine on the viability and apoptosis of human primary HSFs and their reactive oxygen species (ROS) production as well as a rabbit ear model of HS were determined by CCK-8, flow cytometry, Western blot, immunofluorescence, transwell migration, collagen gel contraction assays.

Results: Lycorine treatment selectively decreased the viability of HSFs, and induced their apoptosis, but not normal fibroblasts (NFs). Lycorine treatment increased the relative levels of Bax and cleaved PARP expression, cytochrome C cytoplasm translocation, but decreased Bcl-2, caspase-3 and caspase-9 expression, the mitochondrial membrane potential (MMP) in HSFs. Lycorine inhibited the migration and contraction of HSFs, and reduced the expression of collagen I, collagen III and α-SMA. Mechanistically, lycorine treatment stimulated high levels of ROS production, leading to apoptosis of HSFs while treatment with NAC, a ROS inhibitor, significantly mitigated or abrogated the pro-apoptotic and antifibrotic activity of lycorine in HSFs. Moreover, lycorine treatment mitigated the severity of HS in rabbit ears by inducing fibroblast apoptosis.

Conclusion: These results indicate that lycorine has a potent anti-fibrotic activity and is a potential drug for intervention of HS.

The ASIC3-M-CSF-M2 macrophage-positive feedback loop modulates fibroblast-to-myofibroblast differentiation in skin fibrosis pathogenesis

Inflammation is one of the main pathological features leading to skin fibrosis and a key factor leading to the progression of skin fibrosis. Acidosis caused by a decrease in extracellular pH is a sign of the inflammatory process. Acid-sensing ion channels (ASICs) are ligand-gated ion channels on the cell membrane that sense the drop in extracellular pH. The molecular mechanisms by which skin fibroblasts are regulated by acid-sensing ion channel 3 (ASIC3) remain unknown. This study investigated whether ASIC3 is related to inflammation and skin fibrosis and explored the underlying mechanisms. We demonstrate that macrophage colony-stimulating factor (M-CSF) is a direct target of ASIC3, and ASIC3 activation promotes M-CSF transcriptional regulation of macrophages for M2 polarization. The polarization of M2 macrophages transduced by the ASIC3-M-CSF signal promotes the differentiation of fibroblasts into myofibroblasts through transforming growth factor β1 (TGF-β1), thereby producing an ASIC3-M-CSF-TGF-β1 positive feedback loop. Targeting ASIC3 may be a new treatment strategy for skin fibrosis.

Sphingosine 1-Phosphate Signaling at the Skin Barrier Interface

Sphingosine 1-phosphate (S1P) is a product of membrane sphingolipid metabolism. S1P is secreted and acts via G-protein-coupled receptors, S1PR1-5, and is involved in diverse cellular functions, including cell proliferation, immune suppression, and cardiovascular functions. Recent studies have shown that the effects of S1P signaling are extended further by coupling the different S1P receptors and their respective downstream signaling pathways. Our group has recently reported that S1P inhibits cell proliferation and induces differentiation in human keratinocytes. There is a growing understanding of the connection between S1P signaling, skin barrier function, and skin diseases. For example, the activation of S1PR1 and S1PR2 during bacterial invasion regulates the synthesis of inflammatory cytokines in human keratinocytes. Moreover, S1P-S1PR2 signaling is involved in the production of inflammatory cytokines and can be triggered by epidermal mechanical stress and bacterial invasion. This review highlights how S1P affects human keratinocyte proliferation, differentiation, immunoreaction, and mast cell immune response, in addition to its effects on the skin barrier interface. Finally, studies targeting S1P-S1PR signaling involved in inflammatory skin diseases are also presented.

Selenium nanoparticles coated with pH responsive silk fibroin complex for fingolimod release and enhanced targeting in thyroid cancer

Cancer-targeted drug delivery systems based on nanoparticles (NPs) have been considered promising therapies. In this study, we developed a pH-responsive smart NPs drug delivery system using silk fibroin (SF), selenium nanoparticles (Se NPs), fingolimod (FTY720), and heptapeptide (T7). The prepared FTY720@T7-SF-Se NPs were spheres with an average diameter of 120 nm, which would contribute to the enhanced permeability and retention effects in tumour regions. The encapsulation efficiency (EE) of the FTY720@T7-SF-Se NPs was 71.95 ± 3.81%. The release of FTY720 from the nanocarriers was pH-dependent, and the release of FTY720 was accelerated in an acidic environment. Both in vitro and in vivo studies showed that FTY720@T7-SF-Se NPs had an enhanced cellular uptake selectivity and antitumor activity for thyroid cancer. The bio-distribution study in vivo further demonstrated that FTY720@T7-SF-Se NPs could effectively accumulate in the tumour region, thereby enhancing the ability to kill cancer cells in vivo. In addition, studies of histology and immunohistochemistry showed that FTY720@T7-SF-Se NPs had low toxicity to the major organs of tumour-bearing mice, indicating the prepared NPs has good biocompatibility in vivo. These results suggest that the tumour-targeted NPs delivery system (FTY720@T7-SF-Se NPs) has great potential as a new tool for thyroid cancer therapy.

Backstage players of fibrosis: NOX4, mTOR, HDAC, and S1P; companions of TGF-β

The fibrotic process could be easily defined as a pathological excess of extracellular matrix deposition, leading to disruption of tissue architecture and eventually loss of function; however, this process involves a complex network of several signal transduction pathways. Virtually almost all organs could be affected by fibrosis, the most affected are the liver, lung, skin, kidney, heart, and eyes; in all of them, the transforming growth factor-beta (TGF-β) has a central role. The canonical and non-canonical signal pathways of TGF-β impact the fibrotic process at the cellular and molecular levels, inducing the epithelial-mesenchymal transition (EMT) and the induction of profibrotic gene expression with the consequent increase in proteins such as alpha-smooth actin (α-SMA), fibronectin, collagen, and other extracellular matrix proteins. Recently, it has been reported that some molecules that have not been typically associated with the fibrotic process, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), mammalian target of rapamycin (mTOR), histone deacetylases (HDAC), and sphingosine-1 phosphate (S1P); are critical in its development. In this review, we describe and discuss the role of these new players of fibrosis and the convergence with TGF-β signaling pathways, unveiling new insights into the panorama of fibrosis that could be useful for future therapeutic targets.

Direct Delivery of Apatite Nanoparticle-Encapsulated siRNA Targeting TIMP-1 for Intractable Abnormal Scars

Hypertrophic scars (HSs) and keloids are histologically characterized by excessive extracellular matrix (ECM) deposition. ECM deposition depends on the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteases (TIMPs). TIMP-1 has been linked to ECM degradation and is therefore a promising therapeutic strategy. In this study, we generated super carbonate apatite (sCA) nanoparticle-encapsulated TIMP-1 small interfering RNA (siRNA) (siTIMP1) preparations and examined the effect of local injections on mouse HSs and on ex vivo-cultured keloids. The sCA-siTIMP1 injections significantly reduced scar formation, scar cross-sectional areas, collagen densities, and collagen types I and III levels in the lesions. None of the mice died or exhibited abnormal endpoints. Apatite accumulation was not detected in the other organs. In an ex vivo keloid tissue culture system, sCA-siTIMP1 injections reduced the thickness and complexity of collagen bundles. Our results showed that topical sCA-siTIMP1 injections during mechanical stress-induced HS development reduced scar size. When keloids were injected three times with sCA-siTIMP1 during 6 days, keloidal collagen levels decreased substantially. Accordingly, sCA-siRNA delivery may be an effective approach for keloid treatment, and further investigations are needed to enable its practical use.

FTY720 ameliorates GvHD by blocking T lymphocyte migration to target organs and by skin fibrosis inhibition

BACKGROUND

Fibrosis is the formation of excess connective tissue in an organ or tissue during a reparative or reactive process. Graft-versus-host disease (GvHD) is a medical complication of allogeneic tissue transplantation with transplanted donor T cell-mediated inflammatory response; it is characterized by a severe immune response with fibrosis in the final stage of the inflammatory process. T helper 17 cells play a critical role in the pathogenesis of GvHD. Fingolimod (FTY720), an analogue of sphingosine-1-phosphate (S1P), is an effective immunosuppressive agent in experimental transplantation models.

METHODS

In this study, we evaluated the effects of FTY720 as a treatment for an animal GvHD model with inflammation and fibrosis. The splenocytes, lymph nodes, blood, tissues from Syngeneic mice and GvHD-induced mice treated vehicle or FTY720 were compared using flow cytometry, hematological analyses, histologic analyses.

RESULTS

FTY720 reduced clinical scores based on the following five clinical parameters: weight loss, posture, activity, fur texture, and skin integrity. FACS data showed that T lymphocyte numbers increased in mesenteric lymph nodes and decreased in splenocytes of FTY720-treated mice. Tissue analysis showed that FTY720 reduced skin, intestinal inflammation, and fibrotic markers. FTY720 dramatically decreased α-smooth muscle actin, connective tissue growth factor, and fibronectin protein levels in keloid skin fibroblasts.

CONCLUSIONS

Thus, FTY720 suppressed migration of pathogenic T cells to target organs, reducing inflammation. FTY720 also inhibited fibrogenesis marker expression in vitro and in vivo. Together, these results suggest that FTY720 prevents GvHD progression via immunosuppression of TH17 and simultaneously acts an anti-fibrotic agent.

Emerging evidence for the roles of peptide in hypertrophic scar

Hypertrophic scar is a dermal fibroproliferative disorder characterized by excess collagen deposition. There are many existing treatment modalities, but none works perfectly in all individuals. Recently, evidence is increasing that peptides can play crucial roles in the prevention or treatment of hypertrophic scar. The peptides may be derived from growth factors, hormones, and intracellular products of proteolysis. In vitro and in vivo studies have revealed that a number of peptides, usually topically applied, have beneficial effects on fibroblasts in rat, mouse, hamster, pig and rabbit scar models. The length of such peptides typically ranges between 10 and 15 amino acids (aa). Peptides may reduce scar progenitors, prevent excessive scarring, decrease scar growth, speed re-epithelialization and promote scar maturation through multiple mechanisms. They may target TGF-β signaling, fibroblast function or collagen modulation, inflammation, renin angiotensin system, gap junction and other pathways. However, there is a paucity of evidence regarding specific binding sites for these peptides in scar models. Here, we review current research progress on the roles of peptides and underlying mechanisms in hypertrophic scar. We also discuss the clinical potential of peptides as therapeutic agents in scarring. Finally, the functions of several peptide-related compounds in hypertrophic scar are summarized.

Sphingosine 1-Phosphate (S1P)/ S1P Receptor Signaling and Mechanotransduction: Implications for Intrinsic Tissue Repair/Regeneration

Tissue damage, irrespective from the underlying etiology, destroys tissue structure and, eventually, function. In attempt to achieve a morpho-functional recover of the damaged tissue, reparative/regenerative processes start in those tissues endowed with regenerative potential, mainly mediated by activated resident stem cells. These cells reside in a specialized niche that includes different components, cells and surrounding extracellular matrix (ECM), which, reciprocally interacting with stem cells, direct their cell behavior. Evidence suggests that ECM stiffness represents an instructive signal for the activation of stem cells sensing it by various mechanosensors, able to transduce mechanical cues into gene/protein expression responses. The actin cytoskeleton network dynamic acts as key mechanotransducer of ECM signal. The identification of signaling pathways influencing stem cell mechanobiology may offer therapeutic perspectives in the regenerative medicine field. Sphingosine 1-phosphate (S1P)/S1P receptor (S1PR) signaling, acting as modulator of ECM, ECM-cytoskeleton linking proteins and cytoskeleton dynamics appears a promising candidate. This review focuses on the current knowledge on the contribution of S1P/S1PR signaling in the control of mechanotransduction in stem/progenitor cells. The potential contribution of S1P/S1PR signaling in the mechanobiology of skeletal muscle stem cells will be argued based on the intriguing findings on S1P/S1PR action in this mechanically dynamic tissue.

The Akt/FoxO/p27Kip1 axis contributes to the anti-proliferation of pentoxifylline in hypertrophic scars

Hypertrophic scars (HS) are characterized by the excessive production and deposition of extracellular matrix (ECM) proteins. Pentoxifylline (PTX), a xanthine derived antioxidant, inhibits the proliferation, inflammation and ECM accumulation of HS. In this study, we aimed to explore the effect of PTX on HS and further clarify the mechanism of PTX‐induced anti‐proliferation. We found that PTX could significantly attenuate proliferation of HS fibroblasts and fibrosis in an animal HS model. PTX inhibited the proliferation of HSFs in a dose‐ and time‐dependent manner, and this growth inhibition was mainly mediated by cell cycle arrest. Transcriptome sequencing showed that PTX affects HS formation through the PI3K/Akt/FoxO1 signalling pathway to activate p27^Kip1. PTX down‐regulated p‐Akt and up‐regulated p‐FoxO1 in TGF‐β1 stimulated fibroblasts at the protein level, and simultaneously, the expression of p27^Kip1 was activated. In a mouse model of HS, PTX treatment resulted in the ordering of collagen fibres. The results revealed that PTX regulates TGFβ1‐induced fibroblast activation and inhibits excessive scar formation. Therefore, PTX is a promising agent for the treatment of HS formation.

Sphingosine-1-Phosphate Receptor 5 Modulates Early-Stage Processes during Fibrogenesis in a Mouse Model of Systemic Sclerosis: A Pilot Study

Systemic sclerosis (SSc) is a rare multi-organ autoimmune disease characterized by progressive skin fibrosis. Inflammation, type 2 immunity, and fibrogenic processes are involved in disease development and may be affected by sphingolipids. However, details about early-stage pathophysiological mechanisms and implicated mediators remain elusive. The sphingolipid sphingosine-1-phosphate (S1P) is elevated in the sera of SSc patients, and its receptor S1P5 is expressed in skin tissue. Nevertheless, almost nothing is known about the dermatological contribution of S1P5 to inflammatory and pro-fibrotic processes leading to the pathological changes seen in SSc. In this study, we observed a novel effect of S1P5 on the inflammatory processes during low-dose bleomycin (BLM)-induced fibrogenesis in murine skin. By comparing 2-week-treated skin areas of wild-type (WT) and S1P5-deficient mice, we found that S1P5 is important for the transcriptional upregulation of the Th2 characteristic transcription factor GATA-3 under treatment-induced inflammatory conditions, while T-bet (Th1) and FoxP3 (Treg) mRNA expression was regulated independently of S1P5. Additionally, treatment caused a regulation of S1P receptor 1 and S1P receptor 3 mRNA as well as a regulation of long-chain ceramide profiles, which both differ significantly between the genotypes. Despite S1P5-dependent differences regarding inflammatory processes, similar macroscopic evidence of fibrosis was detected in the skin histology of WT and S1P5-deficient mice after 4 weeks of subcutaneous BLM treatment. However, at the earlier 2-week point in time, the mRNA data of pro-collagen type 1 and SMAD7 indicate a pro-fibrotic S1P5 contribution in the applied SSc mouse model. In conclusion, we propose that S1P5 plays a role as a novel modulator during the early phase of BLM-caused fibrogenesis in murine skin. An immediate relationship between dermal S1P5 expression and fibrotic processes leading to skin alterations, such as formative for SSc pathogenesis, is indicated but should be studied more profound in further investigations. Therefore, this study is an initial step in understanding the role of S1P5-mediated effects during early stages of fibrogenesis, which may encourage the ongoing search for new therapeutic options for SSc patients.