Phenotypic Plasticity of Fibroblasts during Mammary Carcinoma Development

Cancer-associated fibroblasts (CAFs) in the tumor microenvironment contribute to all stages of tumorigenesis and are usually considered to be tumor-promoting cells. CAFs show a remarkable degree of heterogeneity, which is attributed to developmental origin or to local environmental niches, resulting in distinct CAF subsets within individual tumors. While CAF heterogeneity is frequently investigated in late-stage tumors, data on longitudinal CAF development in tumors are lacking. To this end, we used the transgenic polyoma middle T oncogene-induced mouse mammary carcinoma model and performed whole transcriptome analysis in FACS-sorted fibroblasts from early- and late-stage tumors. We observed a shift in fibroblast populations over time towards a subset previously shown to negatively correlate with patient survival, which was confirmed by multispectral immunofluorescence analysis. Moreover, we identified a transcriptomic signature distinguishing CAFs from early- and late-stage tumors. Importantly, the signature of early-stage CAFs correlated well with tumor stage and survival in human mammary carcinoma patients. A random forest analysis suggested predictive value of the complete set of differentially expressed genes between early- and late-stage CAFs on bulk tumor patient samples, supporting the clinical relevance of our findings. In conclusion, our data show transcriptome alterations in CAFs during tumorigenesis in the mammary gland, which suggest that CAFs are educated by the tumor over time to promote tumor development. Moreover, we show that murine CAF gene signatures can harbor predictive value for human cancer.

Eradication of Hepatocellular Carcinoma by NKG2D-Based CAR-T Cells

Despite the great success of chimeric antigen receptor T (CAR-T)-cell therapy in the treatment of hematologic malignancies, CAR-T-cell therapy is limited in solid tumors, including hepatocellular carcinoma (HCC). NK group 2 member D (NKG2D) ligands (NKG2DL) are generally absent on the surface of normal cells but are overexpressed on malignant cells, offering good targets for CAR-T therapy. Indeed, analysis of The Cancer Genome Atlas and HCC tumor samples showed that the expression of most NKG2DLs was elevated in tumors compared with normal tissues. Thus, we designed a novel NKG2D-based CAR comprising the extracellular domain of human NKG2D, 4-1BB, and CD3ζ signaling domains (BBz). NKG2D-BBz CAR-T cells efficiently killed the HCC cell lines SMMC-7721 and MHCC97H in vitro, which express high levels of NKG2DLs, whereas they less efficiently killed NKG2DL-silenced SMMC-7721 cells or NKG2DL-negative Hep3B cells. Overexpression of MICA or ULBP2 in Hep3B improved the killing capacity of NKG2D-BBz CAR-T cells. T cells expressing the NKG2D-BBz CAR effectively eradicated SMMC-7721 HCC xenografts. Collectively, these results suggested that NKG2D-BBz CAR-T cells could potently eliminate NKG2DL-high HCC cells both in vitro and in vivo, thereby providing a promising therapeutic intervention for patients with NKG2DL-positive HCC.

Human Platelet Lysate Media Supplement Supports Lentiviral Transduction and Expansion of Human T Lymphocytes While Maintaining Memory Phenotype

Immune cell therapy has emerged as a promising approach to treat malignancies that were up until recently only treated on a palliative basis. Chimeric antigen receptor- (CAR-) modified T lymphocytes (T cells) in particular have proven to be very effective for certain hematological malignancies. The production of CAR T cells usually involves viral transduction and ex vivo culture of T cells. The aim of this study was to explore the use of human platelet lysate (HPL) compared to two commonly used supplements, human AB serum (ABS) and fetal bovine serum (FBS), for modified T cell production. For studying transduction, activated T cells were transduced with lentivirus to deliver GFP transgenes with three different promoters. Transduction efficiency (percent GFP) was similar among the supplements, and a modest increase in the transgene product (mean fluorescence intensity) was observed when HPL was used as a supplement compared to ABS. To study the effect of supplements on expansion, peripheral blood mononuclear cells (PBMCs) were activated and expanded in the presence of interleukin 2 (IL2) for fourteen days. T cell expansions using HPL and ABS were comparable and slightly less than the expansion obtained with FBS. Interestingly, cells expanded in media supplemented with HPL showed a higher percentage of T cells with a central memory phenotype compared to those expanded in ABS or FBS. Protein profiling revealed that the phenotypic differences may be explained by elevated levels of several cytokines in HPL, including IL7. The results suggest that the use of HPL as a cell culture supplement during the production of modified T cells is a reasonable alternative to ABS. Furthermore, the use of HPL may enhance in vivo performance of the final product by enriching for central memory T cells that are associated with long-term persistence following adoptive transfer.

Enhancement of the Soluble Form of OX40 and OX40L Costimulatory Molecules but Reduction of the Membrane Form in Type 1 Diabetes (T1D)

This study analyzed the expression of membrane OX40 and OX40L (mOX40 and mOX40L) and levels of soluble OX40 and OX40L (sOX40 and sOX40L) in T1D patients to determine their clinical significance. Peripheral blood (PB) was collected from patients with T1D and healthy control participants. Expression of mOX40 and mOX40L on immune cells was detected by flow cytometry. Levels of sOX40 and sOX40L in sera were measured by ELISA. We demonstrated for the first time enhanced sOX40 and sOX40L expression and reduced mOX40 and mOX40L levels in T1D patients which correlated with the clinical characteristics and inflammatory factors. These results suggest that OX40/OX40L signal may be promising biomarkers and associated with the pathogenesis of T1D.

Nanoparticles for nucleic acid delivery: Applications in cancer immunotherapy

Immunotherapy has recently emerged as a powerful tool for cancer treatment. Early clinical successes from cancer immunotherapy have led to a growing list of FDA approvals, and many new therapies are in clinical and preclinical development. Nucleic acid therapeutics, including DNA, mRNA, and genome editing systems, hold significant potential as a form of immunotherapy due to its robust use in cancer vaccination, adoptive T-cell therapy, and gene regulation. However, these therapeutics must overcome numerous delivery obstacles to be successful, including rapid in vivo degradation, poor uptake into target cells, required nuclear entry, and potential in vivo toxicity in healthy cells and tissues. Nanoparticle delivery systems have been engineered to overcome several of these barriers as a means to safely and effectively deliver nucleic acid therapeutics to immune cells. In this Review, we discuss the applications of nucleic acid therapeutics in cancer immunotherapy, and we detail how nanoparticle platforms have been designed to deliver mRNA, DNA, and genome editing systems to enhance the potency and safety of these therapeutics.

The Role of Airway Myofibroblasts in Asthma

Airway remodeling is a characteristic feature of asthma and is thought to play an important role in the pathogenesis of airway hyperresponsiveness. Myofibroblasts are key structural cells involved in injury and repair, and there is evidence that dysregulation of their normal function contributes to airway remodeling. Despite the importance of myofibroblasts, a lack of specific cellular markers and inconsistent nomenclature have limited recognition of their key role in airway remodeling. Myofibroblasts are increased several-fold in the airways in asthma, in proportion to the severity of the disease. Myofibroblasts are postulated to be derived from both tissue-resident and bone marrow-derived cells, depending on the stage of injury and the tissue. A small number of studies have demonstrated attenuation of myofibroblast numbers and also reversal of established myofibroblast populations in asthma and other inflammatory processes. In this article, we review what is currently known about the biology of myofibroblasts in the airways in asthma and identify potential targets to reduce or reverse the remodeling process. However, further translational research is required to better understand the mechanistic role of the myofibroblast in asthma.

Lactoferrin deficiency induces a pro-metastatic tumor microenvironment through recruiting myeloid-derived suppressor cells in mice

Lactoferrin, an innate immunity molecule, is involved in anti-inflammatory, anti-microbial, and anti-tumor activities. We previously reported that lactoferrin is downregulated in specimens of nasopharyngeal carcinoma and negatively associated with tumor progression and metastasis of patients with nasopharyngeal carcinoma. However, the relationship between lactoferrin and the pro-metastatic microenvironment has not been reported yet. Here, by using the lactoferrin knockout mouse, we found that lactoferrin deficiency facilitated melanoma cells metastasizing to lungs, through recruiting myeloid-derived suppressor cells (MDSCs) in the lungs. Mechanistic studies showed that in the lung microenvironment of the lactoferrin knockout mice, the TLR9 signaling was the most repressed signaling. Lactoferrin can induce MDSCs differentiation and apoptosis, as well as upregulate TLR9 expression. TLR9 agonist or lactoferrin treatment can rescue this phenotype in the tumor metastasis mouse model. Our results suggest a protective role of lactoferrin in cancer metastasis, along with a deficiency in certain components of the innate immune system, may lead to a pro-metastatic tumor microenvironment.

Construction of a biomimetic chemokine reservoir stimulates rapid in situ wound repair and regeneration

Skin is the first protection of human body. It is always challenged by a range of external factors, resulting in the wounds of skin. Hydrogel, as a dressing with multiple advantages, causes increasing interests or the applications in wound treatment. However, the function and importance of micro-environment of wound region are frequently neglected. In this study, we successfully developed a chemokine loaded biomimetic hydrogel as a functional reservoir to stimulate the rapid in situ recruitment of BMSCs for fast wound repair and regeneration. The biomimetic hydrogel was fabricated by using the Polyvinyl alcohol (PVA) combined with chitosan (CS) as the hybrid materials. The fabricated hydrogel possesses many features such as the porous structure, high swelling rate and moisture retention property. More importantly, the incorporated chemokine could be released with a sustained manner from the hydrogel and recruited the bone marrow mesenchymal stem cells (BMSCs) significantly both in vitro & in vivo. Moreover, the hydrogel was demonstrated to be highly biocompatible to the skin tissue without any side effect or irritation observed. Topical delivery of chemokine by the biomimetic PVA/CS hybrid material based hydrogel is demonstrated as a promising carrier to accelerate wound repair and regeneration without inducing scar formation and any other negative complications. The PVA/CS/SDF-1 hydrogel was shown a novel therapeutic system for wound therapy.

Systemic Sclerosis Serum Steers the Differentiation of Adipose-Derived Stem Cells Toward Profibrotic Myofibroblasts: Pathophysiologic Implications

Systemic sclerosis (SSc; scleroderma) is characterized by life-threatening progressive multiorgan fibrosis orchestrated by profibrotic myofibroblasts originating from different sources. Because recent data demonstrated that the majority of myofibroblasts in a murine scleroderma model arise from adipocytic progenitors through the adipocyte-myofibroblast transition process, we sought to determine whether the SSc microenvironment may affect the differentiation potential of adipose-derived stem cells (ADSC). Normal human ADSC from three donors were treated with serum from SSc patients (n = 6), serum from healthy individuals (n = 6), or recombinant human transforming growth factor-β1 (TGFβ1) as positive control of myofibroblastic phenotype induction. ADSC were subjected to in vitro adipogenic differentiation for up to 21 days in the presence of different stimuli followed by lipid content quantification. In selected experiments, adipocytic and mesenchymal/myofibroblast marker gene and protein expression levels were assessed by Real-Time PCR, immunoblotting and immunofluorescence after administration of different stimuli for 72 and 96 h, respectively. Cell contractile phenotype was assayed by collagen gel contraction assay. Likewise stimulation with TGFβ1, SSc serum was able to significantly inhibit the adipocyte differentiation of ADSC as testified by a strong decrease in red-colored lipid droplets after 21 days of adipogenic induction. Treatment of ADSC either with SSc serum or TGFβ1 resulted in the acquisition of a myofibroblast-like phenotype characterized by a reduced expression of the adipocytic markers perilipin and adiponectin, a significant upregulation of the mesenchymal/myofibroblast markers α-SMA+ stress fibers, S100A4 and type I collagen, and an ability to effectively contract collagen gels. In SSc, the pathologic environment may favor the differentiation of ADSC into profibrotic and contractile myofibroblast-like cells. These findings strengthen the notion that the generation of myofibroblasts from ADSC may be relevant in SSc pathophysiology potentially representing a new target for the prevention/treatment of multiorgan fibrosis.

The uPAR System as a Potential Therapeutic Target in the Diseased Eye

Dysregulation of vascular networks is characteristic of eye diseases associated with retinal cell degeneration and visual loss. Visual impairment is also the consequence of photoreceptor degeneration in inherited eye diseases with a major inflammatory component, but without angiogenic profile. Among the pathways with high impact on vascular/degenerative diseases of the eye, a central role is played by a system formed by the ligand urokinase-type plasminogen activator (uPA) and its receptor uPAR. The uPAR system, although extensively investigated in tumors, still remains a key issue in vascular diseases of the eye and even less studied in inherited retinal pathologies such as retinitis pigmantosa (RP). Its spectrum of action has been extended far beyond a classical pro-angiogenic function and has emerged as a central actor in inflammation. Preclinical studies in more prevalent eye diseases characterized by neovascular formation, as in retinopathy of prematurity, wet macular degeneration and rubeosis iridis or vasopermeability excess as in diabetic retinopathy, suggest a critical role of increased uPAR signaling indicating the potentiality of its modulation to counteract neovessel formation and microvascular dysfunction. The additional observation that the uPAR system plays a major role in RP by limiting the inflammatory cascade triggered by rod degeneration rises further questions about its role in the diseased eye.

Biological evaluation of porous nanocomposite scaffolds based on strontium substituted β-TCP and bioactive glass: An in vitro and in vivo study

In the current study, in vitro analysis of the osteogenic potential of different scaffolds based on strontium-substituted β-TCP (Sr-TCP) and bioactive glass (BG) ceramics was conducted using rabbit bone marrow-derived mesenchymal stem cells (rBMSCs) and the osteogenic ability of the prepared Sr-TCP and BG scaffold was evaluated through alkaline phosphatase activity, mineral deposition by Alizarin red staining, and osteoblastic gene expression experiments. The obtained in vitro results revealed that among experimental Sr-TCP/BG nanocomposite scaffold samples with the composition of Sr-TCP/BG: 100/0, 50/50, 75/25, and 25/75, the 50Sr-TCP/50BG sample presented better osteoinductive properties. Therefore, the optimized 50Sr-TCP/50BG nanocomposite scaffold was chosen for further in vivo experiments. In vivo implantation of 50Sr-TCP/50BG scaffold and hydroxyapatite (HA)/TCP granules in a rabbit calvarial defect model showed slow degradation of 50Sr-TCP/50BG scaffold and high resorption rate of HA/TCP granules at 5 months' post-surgery. However, the 50Sr-TCP/50BG scaffolds loaded by mesenchymal stem cells (MSCs) were mainly replaced with new bone even at 2 months post-implantation. Based on the obtained engineering and biological results, 50Sr-TCP/50BG nanocomposite scaffold containing MSCs could be considered as a promising alternative substitute even for load-bearing bone tissue engineering applications.

Regulation of Wound Healing by the NRF2 Transcription Factor-More Than Cytoprotection

The nuclear factor-erythroid 2-related factor 2 (NRF2) transcription factor plays a central role in mediating the cellular stress response. Due to their antioxidant properties, compounds activating NRF2 have received much attention as potential medications for disease prevention, or even for therapy. Accumulating evidence suggests that activation of the NRF2 pathway also has a major impact on wound healing and may be beneficial in the treatment of chronic wounds, which remain a considerable health and economic burden. While NRF2 activation indeed shows promise, important considerations need to be made in light of corresponding evidence that also points towards pro-tumorigenic effects of NRF2. In this review, we discuss the evidence to date, highlighting recent advances using gain- and loss-of-function animal models and how these data fit with observations in humans.

Immune Cytolytic Activity Is Associated With Genetic and Clinical Properties of Glioma

Background: Immunotherapy provided unprecedented advances in the treatment of several previously untreated cancers. However, these immunomodulatory maneuvers showed limited response to patients with glioma in clinical trials. Our aim was to depict the immune characteristics of glioma with immune cytolytic activity at genetic and transcriptome levels.

Methods: In total, 325 gliomas from CGGA dataset as training cohort and 699 gliomas from TCGA dataset as validation cohort were enrolled in our analysis. We calculated the immune cytolytic activity for 1,000 of gliomas. The characteristics of immune cytolytic activity in gliomas were interpreted by the corresponding clinical, molecular genetics and radiological information.

Results: We found that immune cytolytic activity was highly associated with molecular, clinical, and edema extent. High cytolytic activity gliomas were more likely to be diagnosed as glioblastoma and might be a potential marker of mesenchymal subtype. Moreover, those gliomas exhibited significantly increased copy number alterations including recurrent focal amplifications of PDGFA and EGFR, as well as recurrent deletions of CDKN2A/B. Subsequent biological function analysis revealed that the immune response and immune checkpoints expression were significantly correlated with the cytolytic activity of gliomas. Immune cytolytic activity was significantly positively associated with the extent of peri-tumor edema and was independently correlated with reduced survival time.

Conclusion: Our results highlighted the immunoregulatory mechanism heterogeneity of gliomas. Cytolytic activity, indirectly reflected by the extent of peri-tumor edema, may provide a potential index to evaluate the status of immune microenvironment and immune checkpoints in glioma, which should be fully valued for precision classification and immunotherapy.

Virtual learning object in hematopoietic stem cell transplantation for autoimmune diseases

ABSTRACT Objective: describe the development of a virtual learning object to provide information about autologous transplantation of hematopoietic stem cells to autoimmune diseases. Methods: methodological study of a website development, using the instructional design model that includes Analysis, Design, Development and Implementation. Results: the virtual object, available at http://www.transplantardai.com.br, was developed in a web platform, in the Hypertext Markup Language, using the software WebAcappella - Responsive Website Creator (Intuisphere, France 2016). The content was structured in the modules: History, Transplant, Autoimmune Diseases, Links, Guidelines, Speech Team and Doubts. The icons and menus were created in order to attract the user, facilitating the search for information and allowing maximum use of the resources available on the website. Conclusion: the methodology used allowed the development of the virtual learning object, which can be used as a tool to guide and disseminate knowledge about this treatment.

NextGen cell-based immunotherapies in cancer and other immune disorders

T lymphocyte and other cell therapies have the potential to transform how we treat cancers and other diseases that have few therapeutic options. Here, we review the current progress in engineered T cell therapies and look to the future of what will establish cell therapy as the next pillar of medicine. The tools of synthetic biology along with fundamental knowledge in cell biology and immunology have enabled the development of approaches to engineer cells with enhanced capacity to recognize and treat disease safely and effectively. This along with new modes of engineering cells with CRISPR and strategies to make universal 'off-the-shelf' cell therapies will provide more rapid, flexible, and cheaper translation to the clinic.

Helpful, albeit hazardous! Esophageal stem-cell injection in systemic sclerosis

Background

Over 90% of patients with systemic sclerosis suffer from gastroesophageal reflux. Esophageal motility disturbances are associated with a reduced life quality and may force interstitial lung disease progression. We wanted to determine whether we can improve gastroesophageal reflux in these patients by esophageal stem-cell injection.

Methods

We performed a pilot study including eights patients with systemic sclerosis and symptomatic gastroesophageal reflux. Sampling of adipose tissue was performed by an experienced plastic surgeon under local anesthesia. The collected fat was injected into the submucosa of the distal esophagus, each time 1 ml in all four quadrants starting 2, 4 and 6 cm proximal to the Z line (ending up to a total volume of 12 ml). Before the intervention, 3, 6 and finally 12 months after the procedure, patients answered the Gastroesophageal Reflux Disease Health-Related Quality of Life Questionnaire (GERD HRQL) and a high-resolution manometry was performed to quantify changes in motility function.

Results

All patients showed an improvement in the GERD HRQL score after the stem-cell injection and a lower dosage of proton-pump inhibitors. The manometric findings showed no change throughout the time. A serious adverse event occurred, as one patient developed multiple cerebellar embolic infarcts.

Conclusion

Because of the favorable effect in all patients, a safe route for esophageal fat injection needs to be developed.

Mesenchymal stem cells: Cell therapy and regeneration potential

Rapid advances in the isolation of multipotent progenitor cells, routinely called mesenchymal stromal/stem cells (MSCs), from various human tissues and organs have provided impetus to the field of cell therapy and regenerative medicine. The most widely studied sources of MSCs include bone marrow, adipose, muscle, peripheral blood, umbilical cord, placenta, fetal tissue, and amniotic fluid. According to the standard definition of MSCs, these clonal cells adhere to plastic, express cluster of differentiation (CD) markers such as CD73, CD90, and CD105 markers, and can differentiate into adipogenic, chondrogenic, and osteogenic lineages in vitro. However, isolated MSCs have been reported to vary in their potency and self-renewal potential. As a result, the MSCs used for clinical applications often lead to variable or even conflicting results. The lack of uniform characterization methods both in vitro and in vivo also contributes to this confusion. Therefore, the name "MSCs" itself has been increasingly questioned lately. As the use of MSCs is expanding rapidly, there is an increasing need to understand the potential sources and specific potencies of MSCs. This review discusses and compares the characteristics of MSCs and suggests that the variations in their distinctive features are dependent on the source and method of isolation as well as epigenetic changes during maintenance and growth. We also discuss the potential opportunities and challenges of MSC research with the hope to stimulate their use for therapeutic and regenerative medicine.

Synergistic combination of oncolytic virotherapy with CAR T-cell therapy

For patients with advanced hematological malignancies the therapeutic landscape has been transformed by the emergence of adoptive cell transfer utilizing autologous chimeric antigen receptor (CAR)-redirected T-cells. However, solid tumors have proved far more resistant to this approach. Here, we summarize the numerous challenges faced by CAR T-cells designed to target solid tumors, highlighting, in particular, issues related to impaired trafficking, expansion, and persistence. In parallel, we draw attention to exciting developments in the burgeoning field of oncolytic virotherapy and posit strategies for the synergistic combination of oncolytic viruses with CAR T-cells to improve outcomes for patients with advanced solid tumors.

Carbon nanotube doped pericardial matrix derived electroconductive biohybrid hydrogel for cardiac tissue engineering

Cardiovascular diseases represent a major socio-economic burden. In recent years, considerable effort has been invested in optimizing cell delivery strategies to advance cell transplantation therapies to restore heart function for example after an infarct. A particular issue is that the implantation of cells using a non-electroconductive matrix potentially causes arrhythmia. Here, we demonstrate that our hydrazide-functionalized nanotubes-pericardial matrix-derived electroconductive biohybrid hydrogel provides a suitable environment for maturation of human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes. hiPSC-derived cardiomyocytes exhibited an improved contraction amplitude (>500%) on conductive hydrogels compared to cells cultured on Matrigel®. This was accompanied by increased cellular alignment, enhanced connexin 43 expression, and improved sarcomere organization suggesting maturation of the hiPSC-derived cardiomyocytes. Sarcomeric length of these cells increased from 1.3 to 1.7 μm. Moreover, 3D cell-laden engineered tissues exhibited enhanced calcium handling as well as positive response to external electrical and pharmaceutical stimulation. Collectively, our data indicate that our biohybrid hydrogels consisting of solubilized nanostructured pericardial matrix and electroconductive positively charged hydrazide-conjugated carbon nanotubes provide a promising material for stem cell-based cardiac tissue engineering.

Diverse immunotherapies can effectively treat syngeneic brainstem tumors in the absence of overt toxicity

BACKGROUND

Immunotherapy has shown remarkable clinical promise in the treatment of various types of cancers. However, clinical benefits derive from a highly inflammatory mechanism of action. This presents unique challenges for use in pediatric brainstem tumors including diffuse intrinsic pontine glioma (DIPG), since treatment-related inflammation could cause catastrophic toxicity. Therefore, the goal of this study was to investigate whether inflammatory, immune-based therapies are likely to be too dangerous to pursue for the treatment of pediatric brainstem tumors.

METHODS

To complement previous immunotherapy studies using patient-derived xenografts in immunodeficient mice, we developed fully immunocompetent models of immunotherapy using transplantable, syngeneic tumors. These four models - HSVtk/GCV suicide gene immunotherapy, oncolytic viroimmunotherapy, adoptive T cell transfer, and CAR T cell therapy - have been optimized to treat tumors outside of the CNS and induce a broad spectrum of inflammatory profiles, maximizing the chances of observing brainstem toxicity.

RESULTS

All four models achieved anti-tumor efficacy in the absence of toxicity, with the exception of recombinant vaccinia virus expressing GMCSF, which demonstrated inflammatory toxicity. Histology, imaging, and flow cytometry confirmed the presence of brainstem inflammation in all models. Where used, the addition of immune checkpoint blockade did not introduce toxicity.

CONCLUSIONS

It remains imperative to regard the brainstem with caution for immunotherapeutic intervention. Nonetheless, we show that further careful development of immunotherapies for pediatric brainstem tumors is warranted to harness the potential potency of anti-tumor immune responses, despite their possible toxicity within this anatomically sensitive location.

Challenges in Clinical Development of Mesenchymal Stromal/Stem Cells: Concise Review

Identified 50 years ago, mesenchymal stromal/stem cells (MSCs) immediately generated a substantial interest among the scientific community because of their differentiation plasticity and hematopoietic supportive function. Early investigations provided evidence of a relatively low engraftment rate and a transient benefit for challenging congenital and acquired diseases. The reasons for these poor therapeutic benefits forced the entire field to reconsider MSC mechanisms of action together with their ex vivo manipulation procedures. This phase resulted in advances in MSCs processing and the hypothesis that MSC‐tissue supportive functions may be prevailing their differentiation plasticity, broadening the spectrum of MSCs therapeutic potential far beyond their lineage‐restricted commitments. Consequently, an increasing number of studies have been conducted for a variety of clinical indications, revealing additional challenges and suggesting that MSCs are still lagging behind for a solid clinical translation. For this reason, our aim was to dissect the current challenges in the development of still promising cell types that, after more than half a century, still need to reach their maturity. stem cells translational medicine2019;8:1135–1148

Human keratinocyte-derived microvesicle miRNA-21 promotes skin wound healing in diabetic rats through facilitating fibroblast function and angiogenesis

Skin wound healing is a complex physiological process that maintains the integrity of the skin tissues, involving a variety of distinct cell types and signaling molecules. The specific signaling pathways or extracellular cues that govern the healing processes remain elusive. Microvesicles (MVs) have recently emerged as critical mediators of cell communication by delivery of genetic materials to target cells. In this study, we found the direct delivery of HEKa-MVs expressing miR-21 mimics significantly promoted the healing of skin wound in diabetic rats. In-depth studies showed that MV miR-21 promoted fibroblast migration, differentiation, and contraction, induced a pro-angiogenic process of endothelial cells and mediated a pro-inflammatory response. Mechanically, MV miR-21 might target specific essential effector mRNA in fibroblasts such as MMP-1, MMP-3, TIMP3, and TIMP4 to increase MMPs expression and enzymatic activities. Moreover, MV miR-21 regulated ɑ-SMA and N-cadherin to induce fibroblast-myofibroblast differentiation. MV miR-21 up-regulated the IL-6 and IL-8 expressions and their secretion to amplify the immune response. Furthermore, MV miR-21 down-regulated PTEN and RECK in protein level, and activate MAPK/ERK signaling cascade, thereby promoting fibroblast functions. Thus, our study has provided for the first time the basis for the potential application of HEKa-MVs, and MV miR-21 in particular for wound healing.

The Secret Life of Exosomes: What Bees Can Teach Us About Next-Generation Therapeutics

Mechanistic exploration has pinpointed nanosized extracellular vesicles, known as exosomes, as key mediators of the benefits of cell therapy. Exosomes appear to recapitulate the benefits of cells and more. As durable azoic entities, exosomes have numerous practical and conceptual advantages over cells. Will cells end up just being used to manufacture exosomes, or will they find lasting value as primary therapeutic agents? Here, a venerable natural process-the generation of honey-serves as an instructive parable. Flowers make nectar, which bees collect and process into honey. Cells make conditioned medium, which laboratory workers collect and process into exosomes. Unlike flowers, honey is durable, compact, and nutritious, but these facts do not negate the value of flowers themselves. The parallels suggest new ways of thinking about next-generation therapeutics.

CD44 inhibits α-SMA gene expression via a novel G-actin/MRTF-mediated pathway that intersects with TGFβR/p38MAPK signaling in murine skin fibroblasts

Well-regulated differentiation of fibroblasts into myofibroblasts (MF) is critical for skin wound healing. Neoexpression of α-smooth muscle actin (α-SMA), an established marker for MF differentiation, is driven by TGFβ receptor (TGFβR)-mediated signaling. Hyaluronan (HA) and its receptor CD44 may also participate in this process. To further understand this process, primary mouse skin fibroblasts were isolated and treated in vitro with recombinant TGF-β1 (rTGF-β1) to induce α-SMA expression. CD44 expression was also increased. Paradoxically, CD44 knockdown by RNA interference (RNAi) led to increased α-SMA expression and α-SMA-containing stress fibers. Removal of extracellular HA or inhibition of HA synthesis had no effect on α-SMA levels, suggesting a dispensable role for HA. Exploration of mechanisms linking CD44 knockdown to α-SMA induction, using RNAi and chemical inhibitors, revealed a requirement for noncanonical TGFβR signaling through p38MAPK. Decreased monomeric G-actin but increased filamentous F-actin following CD44 RNAi suggested a possible role for myocardin-related transcription factor (MRTF), a known regulator of α-SMA transcription and itself regulated by G-actin binding. CD44 RNAi promoted nuclear accumulation of MRTF and the binding to its transcriptional cofactor SRF. MRTF knockdown abrogated the increased α-SMA expression caused by CD44 RNAi, suggesting that MRTF is required for CD44-mediated regulation of α-SMA. Finally, chemical inhibition of p38MAPK reversed nuclear MRTF accumulation after rTGF-β1 addition or CD44 RNAi, revealing a central involvement of p38MAPK in both cases. We concluded that CD44 regulates α-SMA gene expression through cooperation between two intersecting signaling pathways, one mediated by G-actin/MRTF and the other via TGFβR/p38MAPK.

Genetic and molecular biology of breast cancer among Iranian patients

Abstract

Background, Breast cancer (BC) is one of the leading causes of cancer related deaths in Iran. This high ratio of mortality had a rising trend during the recent years which is probably associated with late diagnosis.

Main body

Therefore it is critical to define a unique panel of genetic markers for the early detection among our population. In present review we summarized all of the reported significant genetic markers among Iranian BC patients for the first time, which are categorized based on their cellular functions.

Conclusions

This review paves the way of introducing a unique ethnic specific panel of diagnostic markers among Iranian BC patients. Indeed, this review can also clarify the genetic and molecular bases of BC progression among Iranians.

Co-expression network analysis identified candidate biomarkers in association with progression and prognosis of breast cancer

PURPOSE

Breast cancer is one of the most common malignancies among females, and its prognosis is affected by a complex network of gene interactions. Weighted gene co-expression network analysis was used to construct free-scale gene co-expression networks and to identify potential biomarkers for breast cancer progression.

METHODS

The gene expression profiles of GSE42568 were downloaded from the Gene Expression Omnibus database. RNA-sequencing data and clinical information of breast cancer from TCGA were used for validation.

RESULTS

A total of ten modules were established by the average linkage hierarchical clustering. We identified 58 network hub genes in the significant module (R² = 0.44) and 6 hub genes (AGO2, CDC20, CDCA5, MCM10, MYBL2, and TTK), which were significantly correlated with prognosis. Receiver-operating characteristic curve validated that the mRNA levels of these six genes exhibited excellent diagnostic efficiency in the test data set of GSE42568. RNA-sequencing data from TCGA showed that the expression levels of these six genes were higher in triple-negative tumors. One-way ANOVA suggested that these six genes were upregulated at more advanced stages. The results of independent sample t test indicated that MCM10 and TTK were associated with tumor size, and that AGO2, CDC20, CDCA5, MCM10, and MYBL2 were overexpressed in lymph-node positive breast cancer.

CONCLUSIONS

AGO2, CDC20, CDCA5, MCM10, MYBL2, and TTK were identified as candidate biomarkers for further basic and clinical research on breast cancer based on co-expression analysis.

Unraveling the Mechanobiology of Extracellular Matrix

Cells need to be anchored to extracellular matrix (ECM) to survive, yet the role of ECM in guiding developmental processes, tissue homeostasis, and aging has long been underestimated. How ECM orchestrates the deterioration of healthy to pathological tissues, including fibrosis and cancer, also remains poorly understood. Inquiring how alterations in ECM fiber tension might drive these processes is timely, as mechanobiology is a rapidly growing field, and many novel mechanisms behind the mechanical forces that can regulate protein, cell, and tissue functions have recently been deciphered. The goal of this article is to review how forces can switch protein functions, and thus cell signaling, and thereby inspire new approaches to exploit the mechanobiology of ECM in regenerative medicine as well as for diagnostic and therapeutic applications. Some of the mechanochemical switching concepts described here for ECM proteins are more general and apply to intracellular proteins as well.

Panax notoginseng saponins promotes cutaneous wound healing and suppresses scar formation in mice

BACKGROUND & AIM

Panax notoginseng saponins are believed to promote wound healing due to its anti-proliferative effect on fibroblasts. The present work was therefore aimed to examine the beneficial effect of PNS on wound healing in vitro and in a murine model of cutaneous wound.

METHODS

The in vitro effects of Panax notoginseng saponins on the proliferation of and nitric oxide (NO) synthesis in human fibroblast 3T3 cells were studied. The in vivo effects of Panax notoginseng saponins were examined in C57 mice with dorsal cutaneous wound. The healing rate and scar formation were followed after treatment with Panax notoginseng saponins. The histology and fibroblast accumulation in the wounds were studied using hematoxylin and eosin (H&E) staining. Expression of α-smooth muscle actin (α-SMA) was examined by immunohistochemistry.

RESULTS

Panax notoginseng saponins inhibited the proliferation of human fibroblast 3T3 with an EC₅₀ of 1.825 mM Panax notoginseng saponins (0.1 mM) significantly promoted NO production (P < 0.01) and NO synthase activity (P < 0.01) of 3T3. In C57 mice with dorsal cutaneous wounds, 0.1 mM Panax notoginseng saponins significant expedited wound healing by reducing the size of lesions and suppressing the formation of scar. H&E staining revealed that treatment with Panax notoginseng saponins suppressed fibroblast accumulation in wound areas, while immunohistochemistry showed a significant reduction in α-SMA expression by 0.1 mM Panax notoginseng saponins.

CONCLUSION

Panax notoginseng saponins are a promising drug candidate that can accelerate wound healing and reduce scar formation.

Alteration of Pressure-Induced Vasodilation in Aging and Diabetes, a Neuro-Vascular Damage

Skin is constantly subjected to pressure at different levels. Pressure-induced vasodilation (PIV) is one of the response mechanisms to low pressure that maintains the homeostasis of the skin. PIV results from the interaction of primary afferent nerves and vascular endothelium of skin vessels. Thanks to this cutaneous neuro-vascular interaction, the cutaneous blood flow increase allows the maintenance of an optimal level of oxygenation and minimizes the lack of vascularization of the skin tissue under low pressure. It seems to be associated with the cutaneous protection mechanisms to prevent pressure ulcers. In some contexts, where microangiopathy and neuropathy can occur, such as aging and diabetes, PIV is impaired, leading to a dramatic early decrease in local skin blood flow when low pressure is applied. In aging, PIV alteration is due to endothelial dysfunction, essentially from an alteration of the nitric oxide pathway. In the inflamm-aging context, oxidative stress increases leading to endothelial cell and nerve damages. An age-related sensory neuropathy will exacerbate the alteration of PIV during the aging process. In diabetes, non-controlled hyperglycaemia leads to an increase in several pathological biochemical pathways that involve oxidative stress and can affect PIV. Sorbinil, alagebrium and alpha-lipoic acid are able individually to restore PIV through a possible oxidative stress reduction. Candesartan, an angiotensin II type 1 receptor blocker, is also able to restore PIV and prevent pressure ulcer formation. The possibility of preventing pressure ulcer associated to diabetes and/or aging with the restoration of PIV seems to be a promising research path.

Role of metabolic syndrome and its components as mediators of the genetic effect on type 2 diabetes: A family-based study in China

BACKGROUND

Metabolic syndrome (MetS) share a genetic basis with type 2 diabetes (T2D). However, whether MetS and its components mediate genetic susceptibility to T2D is not completely understood.

METHODS

We assessed the effects of MetS and its components on associations T2D and 18 genome-wide association studies-identified variants using a two-stage strategy based on parametric models involving 7110 Chinese participants (2436 were T2D patients) across 2885 families. Multilevel logistic regression was used to account for the intrafamilial correlation.

RESULTS

Metabolic syndrome significantly mediated the effect of a melatonin receptor 1B (MTNR1B) polymorphism on T2D risk (OR of average causal mediation effect [OR_ACME ] 1.004; 95% confidence interval [CI] 1.001-1.008; P = 0.018). In addition, low high-density lipoprotein cholesterol (HDL-C) levels mediated the genetic effects of MTNR1B (OR_ACME 1.012; 95% CI 1.007-1.015; P < 0.001), solute carrier family 30 member 8 (SLC30A8; OR_ACME 1.001; 95% CI 1.000-1.007; P < 0.040), B-cell lymphoma/leukemia 11A (BCL11A; OR_ACME 1.009; 95% CI 1.007-1.016; P < 0.001), prospero homeobox 1 (PROX1; OR_ACME 1.005; 95% CI 1.003-1.011; P < 0.001) and a disintegrin and metallopeptidase with thrombospondin type 1 motif 9 (ADAMTS9; OR_ACME 1.006; 95% CI 1.001-1.009; P = 0.022), whereas increased fasting blood glucose (FBG) significantly mediated the genetic effect of BCL11A (OR_ACME 1.017; 95% CI 1.003-1.021; P = 0.012).

CONCLUSIONS

This study provides evidence that MetS and two of its components (HDL-C, FBG) may be involved in mediating the genetic predisposition to T2D, which emphasize the importance of maintaining normal HDL-C and FBG levels.

In Depth Quantification of Extracellular Matrix Proteins from Human Pancreas

Extracellular matrix (ECM) is an important component of the pancreatic microenvironment which regulates β cell proliferation, differentiation, and insulin secretion. Protocols have recently been developed for the decellularization of the human pancreas to generate functional scaffolds and hydrogels. In this work, we characterized human pancreatic ECM composition before and after decellularization using isobaric dimethylated leucine (DiLeu) labeling for relative quantification of ECM proteins. A novel correction factor was employed in the study to eliminate the bias introduced during sample preparation. In comparison to the commonly employed sample preparation methods (urea and FASP) for proteomic analysis, a recently developed surfactant and chaotropic agent assisted sequential extraction/on pellet digestion (SCAD) protocol has provided an improved strategy for ECM protein extraction of human pancreatic ECM matrix. The quantitative proteomic results revealed the preservation of matrisome proteins while most of the cellular proteins were removed. This method was compared with a well-established label-free quantification (LFQ) approach which rendered similar expressions of different categories of proteins (collagens, ECM glycoproteins, proteoglycans, etc.). The distinct expression of ECM proteins was quantified comparing adult and fetal pancreas ECM, shedding light on the correlation between matrix composition and postnatal β cell maturation. Despite the distinct profiles of different subcategories in the native pancreas, the distribution of matrisome proteins exhibited similar trends after the decellularization process. Our method generated a large data set of matrisome proteins from a single tissue type. These results provide valuable insight into the possibilities of constructing a bioengineered pancreas. It may also facilitate better understanding of the potential roles that matrisome proteins play in postnatal β cell maturation.

State-of-the-Art Strategies for the Vascularization of Three-Dimensional Engineered Organs

Engineering three-dimensional (3D) implantable tissue constructs is a promising strategy for replacing damaged or diseased tissues and organs with functional replacements. However, the efficient vascularization of new 3D organs is a major scientific and technical challenge since large tissue constructs or organs require a constant blood supply to survive in vivo. Current approaches to solving this problem generally fall into the following three major categories: (a) cell-based, (b) angiogenic factor-based, and (c) scaffold-based. In this review, we summarize state-of-the-art technologies that are used to develop complex, stable, and functional vasculature for engineered 3D tissue constructs and organs; additionally, we have suggested directions for future research.

Trabecular meshwork mesenchymal stem cell transplantation improve motor symptoms of parkinsonian rat model

Stem cell transplantation is a new therapeutic strategy in the treatment of neurodegenerative disorders such as Parkinson's disease (PD). Therefore, in this study, the therapeutic effects of Trabecular Meshwork Mesenchymal Stem Cells (TM-MSCs) transplantation, as a new source of mesenchymal stem cells, were evaluated in the animal model of PD. After the development and confirmation of hemi-parkinsonian rats by administration of 6-hydroxy dopamine (6-OHDA) and apomorphine-induced rotation test, green fluorescent protein (GFP) labeled TM-MSCs (normal and induced cells) were transplanted in the striatum of rats. Next, the rotation test, rotarod test, open field, passive avoidance memory tests and immunohistochemistry for tyrosine hydroxylase (TH) were done. The results showed that the number of turns significantly decreased and the improvement of motor performance was achieved after cell transplantation. However, there was no significant difference in passive avoidance memory of animals documented by shuttle box test. The number of GFP- labeled cells expressing TH significantly is increased compared to the vehicle group. Collectively, it seems that TM-MSCs and induced TM-MSCs cell transplantation have positive effects on some aspects of the animal model of PD. Other studies may reveal the potentially positive aspects of these cells in the laboratory and clinical studies.

Regeneration of Dermis: Scarring and Cells Involved

There are many studies on certain skin cell specifications and their contribution to wound healing. In this review, we provide an overview of dermal cell heterogeneity and their participation in skin repair, scar formation, and in the composition of skin substitutes. The papillary, reticular, and hair follicle associated fibroblasts differ not only topographically, but also functionally. Human skin has a number of particular characteristics that are different from murine skin. This should be taken into account in experimental procedures. Dermal cells react differently to skin wounding, remodel the extracellular matrix in their own manner, and convert to myofibroblasts to different extents. Recent studies indicate a special role of papillary fibroblasts in the favorable outcome of wound healing and epithelial-mesenchyme interactions. Neofolliculogenesis can substantially reduce scarring. The role of hair follicle mesenchyme cells in skin repair and possible therapeutic applications is discussed. Participation of dermal cell types in wound healing is described, with the addition of possible mechanisms underlying different outcomes in embryonic and adult tissues in the context of cell population characteristics and extracellular matrix composition and properties. Dermal white adipose tissue involvement in wound healing is also overviewed. Characteristics of myofibroblasts and their activity in scar formation is extensively discussed. Cellular mechanisms of scarring and possible ways for its prevention are highlighted. Data on keloid cells are provided with emphasis on their specific characteristics. We also discuss the contribution of tissue tension to the scar formation as well as the criteria and effectiveness of skin substitutes in skin reconstruction. Special attention is given to the properties of skin substitutes in terms of cell composition and the ability to prevent scarring.

Systematization of analytical studies of polycythemia vera, essential thrombocythemia and primary myelofibrosis, and a meta-analysis of the frequency of JAK2, CALR and MPL mutations: 2000-2018

BACKGROUND

Research into Philadelphia-negative chronic myeloproliferative neoplasms is heterogeneous. In addition, no systematization of studies of polycythemia vera (PV), essential thrombocythemia (ET) or primary myelofibrosis (PMF) have been carried out. The objective of this review is to characterize studies on BCR-ABL1-negative chronic myeloproliferative neoplasms and to compare the frequency of JAK2, MPL and CALR mutations in PV, ET and PMF.

METHOD

A systematic review of the scientific literature was conducted, as was meta-analysis with an ex-ante selection of protocol, according to phases of the PRISMA guide in three interdisciplinary databases. To guarantee reproducibility in the pursuit and retrieval of information, the reproducibility and methodological quality of the studies were evaluated by two researchers.

RESULTS

Fifty-two studies were included, the majority having been carried out in the United States, China, Brazil and Europe. The frequency of the JAK2V617F mutation ranged from 46.7 to 100% in patients with PV, from 31.3 to 72.1% in patients with ET, and from 25.0 to 85.7% in those with PMF. The frequency of the MPL mutation was 0% in PV, from 0.9 to 12.5% in ET, and from 0 to 17.1% in PMF. The CALR mutation occurred at a frequency of 0.0% in PV, whereas in ET, it ranged from 12.6 to 50%, and in PMF, it ranged from 10 to 100%. The risk of this mutation presenting in PV is 3.0 times that found for ET and 4.0 times that found for PMF.

CONCLUSION

Given the specificity and reported high frequencies of the JAK2V617F, MPL and CALR mutations in this group of neoplasms, the diagnosis of these diseases should not be made on clinical and hematological characteristics alone but should include genetic screening of patients.

Role of Ancillary Procedures in Facial Rejuvenation

Face-lift techniques have evolved beyond the concept of lifting and now include incorporating superficial and deep filling of facial fat compartments to address volume deflation and aging. In addition to traditional face-lift methods involving the excision and tightening of skin and the underlying soft tissues, the following ancillary procedures have become paramount in achieving an optimal result: blending the lid-cheek junction; chin augmentation; lobule augmentation; hand rejuvenation; perioral rejuvenation; chemical peels; and laser resurfacing. We presented a summary of these integral techniques.

[Management of CAR-T cell-related encephalopathy syndrome in adult and pediatric patients: Recommendations of the French Society of Bone Marrow transplantation and cellular Therapy (SFGM-TC)]

CAR-T cell-related encephalopathy syndrome (CRES) reflects the potential neurotoxicity of this therapeutic approach and must be considered in the presence of any neurological symptom after the infusion of the CAR-T. This is the second most common adverse event under this therapy and its incidence varies between 12 and 55%. The median time of the onset of the first neurologic symptoms is 4days after CAR-T infusion. The duration of CRES symptoms is generally between 2 and 4days, but late CRES may occur. Monitoring and diagnosis of CERS includes clinical exam, magnetic resonance imaging and electroencephalography. In addition to symptomatic treatments, corticosteroids represent the cornerstone of the high-grade CERS treatment. Drugs targeting IL-6 should be restricted to severe forms, especially those associated with cytokine release syndrome. The purpose of this workshop is to provide practical help in dealing with this complication.

Effect of pirfenidone injection on ferret vocal fold scars: A preliminary in vivo study

OBJECTIVES

This study examined the antifibrotic effect of pirfenidone (PFD), which has received regulatory approval in the United States and Japan for treatment of idiopathic pulmonary fibrosis, on the scarred ferret vocal fold (VF) in vivo.

METHODS

Eight male ferrets were divided into two groups: saline and PFD. All animals underwent unilateral scarring under anesthesia. The right VF was electrocauterized with ablation of the entire lamina propria. PFD (1.0 mg/mL) or saline injections into right-side scarred VFs were performed (under an operating microscope) 4 weeks later. After an additional 4 weeks, the larynges were harvested for histological analysis. Prior to harvesting, the ferrets were re-anesthetized, and the VFs were observed and recorded using a rigid video laryngoscope. We immunohistochemically evaluated the expression of collagen types I and III, alpha-smooth muscle actin (α-SMA), and fibronectin in the entire lamina propria. We compared the affected areas (calculated using ImageJ software) between the treated (right) and untreated (left) sides within the same animals and between groups.

RESULTS

Collagen type I (P = 0.0021) and α-SMA (P = 0.0021) expression levels were lower in the PFD group, but the collagen type III and fibronectin levels did not differ significantly between the two groups.

CONCLUSION

PFD injection into the scarred VF is a potentially promising novel antifibrotic treatment.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:726-731, 2020.

An international survey on the management of patients receiving CAR T-cell therapy for haematological malignancies on behalf of the Chronic Malignancies Working Party of EBMT

PURPOSE OF THE STUDY

Two chimeric antigen receptor (CAR) T-cell therapies - Tisagenlecleucel (Kymriah^™) and Axicabtagene ciloleucel (Yescarta^™) - have been approved for commercial use. In order to inform forthcoming EBMT guidelines on the management of adults and children undergoing autologous CAR T-cell therapy, we undertook a survey of experienced clinicians.

METHODS

An online survey with a dual focus on (1) 'real world' patient eligibility criteria and (2) models of care for patient follow-up was sent to experienced physicians.

RESULTS

There were 41 respondents (10 countries) and 93% worked in FACT-JACIE-accredited transplant centres. Most felt that a history of malignancy (57%), prior allo-HCT for B-NHL (78%-81%) and prior treatment with anti-CD19/CD3 BiTE antibodies (76%-86%) do not constitute contra-indications to CAR T therapy. Clinicians were divided as to whether CNS involvement represented an exclusion criterion. There was agreement that patients with viral infections (HIV, Hepatitis B or Hepatitis C) are not eligible. There is no common model of care for long-term follow-up. Most respondents believed that patients should attend the hospital two (43%) to three (33%) times weekly during the first month following discharge. A majority (69%) of respondents work in centres where there is an MDT meeting with a specific focus on follow-up following CAR T Therapy. Follow-up care is currently delivered either in HCT or haematology-oncology outpatient clinics.

CONCLUSION

The responses reveal wide variation in perceived patient eligibility criteria and highlight the need for consensus guidelines. The findings also illustrate the embryonic nature of current follow-up arrangements.

Toward understanding scarless skin wound healing and pathological scarring

The efficient healing of skin wounds is crucial for securing the vital barrier function of the skin, but pathological wound healing and scar formation are major medical problems causing both physiological and psychological challenges for patients. A number of tightly coordinated regenerative responses, including haemostasis, the migration of various cell types into the wound, inflammation, angiogenesis, and the formation of the extracellular matrix, are involved in the healing process. In this article, we summarise the central mechanisms and processes in excessive scarring and acute wound healing, which can lead to the formation of keloids or hypertrophic scars, the two types of fibrotic scars caused by burns or other traumas resulting in significant functional or aesthetic disadvantages. In addition, we discuss recent developments related to the functions of activated fibroblasts, the extracellular matrix and mechanical forces in the wound environment as well as the mechanisms of scarless wound healing. Understanding the different mechanisms of wound healing is pivotal for developing new therapies to prevent the fibrotic scarring of large skin wounds.