Mechanisms of force generation and transmission by myofibroblasts

Radiotherapy-induced heart disease: a review of the literature

Radiotherapy as one of the four pillars of cancer therapy plays a critical role in the multimodal treatment of thoracic cancers. Due to significant improvements in overall cancer survival, radiotherapy-induced heart disease (RIHD) has become an increasingly recognized adverse reaction which contributes to major radiation-associated toxicities including non-malignant death. This is especially relevant for patients suffering from diseases with excellent prognosis such as breast cancer or Hodgkin’s lymphoma, since RIHD may occur decades after radiotherapy. Preclinical studies have enriched our knowledge of many potential mechanisms by which thoracic radiotherapy induces heart injury. Epidemiological findings in humans reveal that irradiation might increase the risk of cardiac disease at even lower doses than previously assumed. Recent preclinical studies have identified non-invasive methods for evaluation of RIHD. Furthermore, potential options preventing or at least attenuating RIHD have been developed. Ongoing research may enrich our limited knowledge about biological mechanisms of RIHD, identify non-invasive early detection biomarkers and investigate potential treatment options that might attenuate or prevent these unwanted side effects. Here, we present a comprehensive review about the published literature regarding clinical manifestation and pathological alterations in RIHD. Biological mechanisms and treatment options are outlined, and challenges in RIHD treatment are summarized.

Smad interacting protein 1 influences transforming growth factor-β1/Smad signaling in extracellular matrix protein production and hypertrophic scar formation

The transforming growth factor (TGF)-β/Smad signal transduction pathway is closely associated with hypertrophic scar (HS) formation. Smad interacting protein 1 (SIP1) is a cytoplasmic protein that efficiently regulates Smad2-/3-dependent signaling within the TGF-β₁ pathway. SIP1 influences collagen synthesis in the HS through a heretofore unknown mechanism. This study investigated the role of the SIP1-mediated TGF-β₁/Smad signaling pathway in extracellular matrix (ECM) protein production and hypertrophic scarring. SIP1 expression was markedly lower in HS vs. normal skin (NS) tissue, and α-smooth muscle actin (α-SMA) content and collagen I/III (Col I/III) synthesis were inversely correlated with SIP1 expression. Furthermore, SIP1 inhibited Smad2/3 phosphorylation in vitro, and improved the collagen-based architecture of the scar while reducing collagen expression and overall scar formation in a rabbit ear model of HS. Based on these findings, we propose that SIP1 acts as a molecular modulator capable of altering Smad2-/3-facilitated signaling through the control of Smad phosphorylation, thus inhibiting α-SMA and collagen upregulation in fibroblasts and, ultimately, HS formation. The low SIP1 content in scar tissue also suggests that SIP1 (and positive regulation thereof) is a prospective target for selective HS drug therapy.

Myofibroblast-Specific TGFβ Receptor II Signaling in the Fibrotic Response to Cardiac Myosin Binding Protein C-Induced Cardiomyopathy

RATIONALE

Hypertrophic cardiomyopathy occurs with a frequency of about 1 in 500 people. Approximately 30% of those affected carry mutations within the gene encoding cMyBP-C (cardiac myosin binding protein C). Cardiac stress, as well as cMyBP-C mutations, can trigger production of a 40kDa truncated fragment derived from the amino terminus of cMyBP-C (Mybpc3^40kDa). Expression of the 40kDa fragment in mouse cardiomyocytes leads to hypertrophy, fibrosis, and heart failure. Here we use genetic approaches to establish a causal role for excessive myofibroblast activation in a slow, progressive genetic cardiomyopathy-one that is driven by a cardiomyocyte-intrinsic genetic perturbation that models an important human disease.

OBJECTIVE

TGFβ (transforming growth factor-β) signaling is implicated in a variety of fibrotic processes, and the goal of this study was to define the role of myofibroblast TGFβ signaling during chronic Mybpc3^40kDa expression.

METHODS AND RESULTS

To specifically block TGFβ signaling only in the activated myofibroblasts in Mybpc3^40kDa transgenic mice and quadruple compound mutant mice were generated, in which the TGFβ receptor II (TβRII) alleles ( Tgfbr2) were ablated using the periostin ( Postn) allele, myofibroblast-specific, tamoxifen-inducible Cre ( Postnmcm) gene-targeted line. Tgfbr2 was ablated either early or late during pathological fibrosis. Early myofibroblast-specific Tgfbr2 ablation during the fibrotic response reduced cardiac fibrosis, alleviated cardiac hypertrophy, preserved cardiac function, and increased lifespan of the Mybpc3^40kDa transgenic mice. Tgfbr2 ablation late in the pathological process reduced cardiac fibrosis, preserved cardiac function, and prolonged Mybpc3^40kDa mouse survival but failed to reverse cardiac hypertrophy.

CONCLUSIONS

Fibrosis and cardiac dysfunction induced by cardiomyocyte-specific expression of Mybpc3^40kDa were significantly decreased by Tgfbr2 ablation in the myofibroblast. Surprisingly, preexisting fibrosis was partially reversed if the gene was ablated subsequent to fibrotic deposition, suggesting that continued TGFβ signaling through the myofibroblasts was needed to maintain the heart fibrotic response to a chronic, disease-causing cardiomyocyte-only stimulus.

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.

Ischemia Reperfusion Injury Produces, and Ischemic Preconditioning Prevents, Rat Cardiac Fibroblast Differentiation: Role of KATP Channels

Ischemic preconditioning (IPC) and activation of ATP-sensitive potassium channels (K_ATP) protect cardiac myocytes from ischemia reperfusion (IR) injury. We investigated the influence of IR injury, IPC and K_ATP in isolated rat cardiac fibroblasts. Hearts were removed under isoflurane anesthesia. IR was simulated in vitro by application and removal of paraffin oil over pelleted cells. Ischemia (30, 60 and 120 min) followed by 60 min reperfusion resulted in significant differentiation of fibroblasts into myofibroblasts in culture (mean % fibroblasts ± SEM in IR vs. time control: 12 ± 1% vs. 63 ± 2%, 30 min ischemia; 15 ± 3% vs. 71 ± 4%, 60 min ischemia; 8 ± 1% vs. 55 ± 2%, 120 min ischemia). IPC (15 min ischemia, 30 min reperfusion) significantly attenuated IR-induced fibroblast differentiation (52 ± 3%) compared to 60 min IR. IPC was mimicked by opening K_ATP with pinacidil (50 μM; 43 ± 6%) and by selectively opening mitochondrial K_ATP (mK_ATP) with diazoxide (100 μM; 53 ± 3%). Furthermore, IPC was attenuated by inhibiting K_ATP with glibenclamide (10 μM; 23 ± 5%) and by selectively blocking mK_ATP with 5-hydroxydecanoate (100 μM; 22 ± 9%). These results suggest that (a) IR injury evoked cardiac fibroblast to myofibroblast differentiation, (b) IPC attenuated IR-induced fibroblast differentiation, (c) K_ATP were involved in IPC and (d) this protection involved selective activation of mK_ATP.

Cardiac fibrosis - A short review of causes and therapeutic strategies

Fibrotic diseases cause annually more than 800,000 deaths worldwide, whereof the majority accounts for lung and cardiac fibrosis. A pathological remodeling of the extracellular matrix either due to ageing or as a result of an injury or disease leads to fibrotic scars. In the heart, these scars cause several cardiac dysfunctions either by reducing the ejection fraction due to a stiffened myocardial matrix, or by impairing electric conductance, or they can even lead to death. Today it is known that there are several different types of cardiac scars depending on the underlying cause of fibrosis. In this review, we present an overview of what is known about cardiac fibrosis including the role of cardiac cells and extracellular matrix in this disease. We will further summarize current diagnostic tools and highlight pre-clinical or clinical therapeutic strategies to address cardiac fibrosis.

Integrins, CAFs and Mechanical Forces in the Progression of Cancer

Cells respond to both chemical and mechanical cues present within their microenvironment. Various mechanical signals are detected by and transmitted to the cells through mechanoreceptors. These receptors often contact with the extracellular matrix (ECM), where the external signals are converted into a physiological response. Integrins are well-defined mechanoreceptors that physically connect the actomyosin cytoskeleton to the surrounding matrix and transduce signals. Families of α and β subunits can form a variety of heterodimers that have been implicated in cancer progression and differ among types of cancer. These heterodimers serve as the nexus of communication between the cells and the tumor microenvironment (TME). The TME is dynamic and composed of stromal cells, ECM and associated soluble factors. The most abundant stromal cells within the TME are cancer-associated fibroblasts (CAFs). Accumulating studies implicate CAFs in cancer development and metastasis through their remodeling of the ECM and release of large amounts of ECM proteins and soluble factors. Considering that the communication between cancer cells and CAFs, in large part, takes place through the ECM, the involvement of integrins in the crosstalk is significant. This review discusses the role of integrins, as the primary cell-ECM mechanoreceptors, in cancer progression, highlighting integrin-mediated mechanical communication between cancer cells and CAFs.

Amiodarone induces cell proliferation and myofibroblast differentiation via ERK1/2 and p38 MAPK signaling in fibroblasts

Amiodarone is a potent antidysrhythmic agent that can cause potentially life-threatening pulmonary fibrosis. Accumulating evidence has demonstrated that myofibroblast differentiation is related to the pathogenesis of pulmonary fibrosis. In the present study, we treated human embryonic lung fibroblasts (HELFs) with amiodarone, and investigated the relative molecular mechanism of amiodarone-induced pulmonary fibrosis and pathway determinants PD98059 (extracellular signal-regulated kinase (ERK) inhibitor) and SB203580 (p38 mitogen-activated protein kinase (MAPK) inhibitor). Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8). The secretion of collagen Ⅰ was detected by ELISA. The expressions of α-smooth muscle actin (α-SMA), vimentin, phosphorylated ERK1/2 (p-ERK1/2), ERK1/2, phosphorylated p38 MAPK (p-p38), and p38 MAPK were investigated using Western blot analysis. The levels of α-SMA and vimentin were also determined by immunofluorescence and qRT-PCR. We report that amiodarone promoted cell proliferation and collagen Ⅰ secretion, induced α-SMA and vimentin protein and mRNA expression accompanied by increased phosphorylation of ERK1/2 and p38 MAPK, and furthermore, PD98059 and SB203580 remarkably reduced the proliferative response of HELFs compared with amiodarone group and greatly attenuated α-SMA, vimentin and collagen Ⅰ protein production induced by amiodarone. Taken together, our study suggests that amiodarone regulates cell proliferation and myofibroblast differentiation in HELFs through modulating ERK1/2 and p38 MAPK pathways, and these signal pathways may therefore represent an attractive treatment modality in amiodarone-induced pulmonary fibrosis.

Differentiation of myofibroblasts in wounds after topical use of metronidazole: an experimental study

OBJECTIVE

to assess the effects of topical administration of metronidazole on fibroblast differentiation and on wound contraction during experimental secondary intention wound healing in rats.

METHODS

we submitted 108 rats to a circular wound on the back, 2cm in diameter, and divided them into six groups: control group, with application of saline solution on the wound and five experimental groups, divided according to the concentration of metronidazole solution used (4%, 6%, 8%, 10% and 12%). We changed the dressings daily throughout the trial period, which comprised three stages of analysis: three, seven and 14 days. We evaluated wound contraction by digital planimetry, and identified myofibroblasts and protomyofibroblasts using CD34 and α-SMA immunohistochemistry techniques.

RESULTS

wound contraction was not different between the experimental and the control groups. Protomyofibroblasts were significantly more numerous at seven days (p=0.022) in the 4%, 6% and 8% metronidazole groups. After 14 days, in the same groups, myofibroblasts predominated significantly (p=0.01).

CONCLUSION

the topical administration of metronidazole solution in skin wounds healing by secondary intention was able to improve the differentiation of fibroblasts. The contraction phase of wound healing remained unchanged, without significant reduction of the contraction evaluated by digital planimetry. These results can be used in favor of the wound healing process.

Cardiac Fibrotic Remodeling on a Chip with Dynamic Mechanical Stimulation

Cardiac tissue is characterized by being dynamic and contractile, imparting the important role of biomechanical cues in the regulation of normal physiological activity or pathological remodeling. However, the dynamic mechanical tension ability also varies due to extracellular matrix remodeling in fibrosis, accompanied with the phenotypic transition from cardiac fibroblasts (CFs) to myofibroblasts. It is hypothesized that the dynamic mechanical tension ability regulates cardiac phenotypic transition within fibrosis in a strain-mediated manner. In this study, a microdevice that is able to simultaneously and accurately mimic the biomechanical properties of the cardiac physiological and pathological microenvironment is developed. The microdevice can apply cyclic compressions with gradient magnitudes (5-20%) and tunable frequency onto gelatin methacryloyl (GelMA) hydrogels laden with CFs, and also enables the integration of cytokines. The strain-response correlations between mechanical compression and CFs spreading, and proliferation and fibrotic phenotype remolding, are investigated. Results reveal that mechanical compression plays a crucial role in the CFs phenotypic transition, depending on the strain of mechanical load and myofibroblast maturity of CFs encapsulated in GelMA hydrogels. The results provide evidence regarding the strain-response correlation of mechanical stimulation in CFs phenotypic remodeling, which can be used to develop new preventive or therapeutic strategies for cardiac fibrosis.

Immunohistochemical Expression of Myofibroblasts Using Alpha-smooth Muscle Actin (SMA) to Assess the Aggressive Potential of Various Clinical Subtypes of Ameloblastoma

Objective:

Ameloblastoma is a rare odontogenic neoplasm with high recurrence rates if improperly treated. If left untreated (or is treated inadequately), it can cause substantial morbidity, disfigurement, and even death. Hence, there is a need to explore the stromal cells too, which might play an important role in assessing its aggressive behavior and may help to predict the recurrence of different clinical variants of ameloblastoma. Myofibroblasts (MFs) are such cells which have been studied in various lesions.

Materials and Methods:

This retrospective study involved archival tissues of ameloblastoma. Among a total of 40 cases, 12 cases of SMA (solid multicystic ameloblastoma), 10 cases of unicystic ameloblastoma (UA), 8 cases of desmoplastic ameloblastoma, and 10 cases of oral squamous cell carcinoma were selected as control. Immunohistochemical staining with anti-alpha-smooth muscle actin antibody was done. Interpretation of ten examined fields was counted by three observers.

Results:

Significant difference in the number of MFs in SMA and UA and desmoplastic ameloblastoma and UA (P < 0.05) was found. However, there was no statistically significant difference in MFs of SMA and desmoplastic ameloblastomas (P > 0.05). In addition, there was no statistically significant difference in the staining intensity between the three variants (P > 0.05).

Conclusion:

A significant correlation was obtained between the number of MF in all the three clinical variants, i.e., SMA, UA, and desmoplastic ameloblastoma (P = 0.02), which is the unique feature of the study.

Extracellular matrix alignment dictates the organization of focal adhesions and directs uniaxial cell migration

Physical features of the extracellular matrix (ECM) heavily influence cell migration strategies and efficiency. Migration in and on fibrous ECMs is of significant physiologic importance, but limitations in the ability to experimentally define the diameter, density, and alignment of native ECMs in vitro have hampered our understanding of how these properties affect this basic cell function. Here, we designed a high-throughput in vitro platform that models fibrous ECM as collections of lines of cell-adhesive fibronectin on a flat surface to eliminate effects of dimensionality and topography. Using a microcontact printing approach to orthogonally vary line alignment, density, and size, we determined each factor's individual influence on NIH3T3 fibroblast migration. High content imaging and statistical analyses revealed that ECM alignment is the most critical parameter in influencing cell morphology, polarization, and migratory behavior. Specifically, increasing ECM alignment led cells to adopt an elongated uniaxial morphology and migrate with enhanced speed and persistence. Intriguingly, migration speeds were tightly correlated with the organization of focal adhesions, where cells with the most aligned adhesions migrated fastest. Highly organized focal adhesions and associated actin stress fibers appeared to define the number and location of protrusive fronts, suggesting that ECM alignment influences active Rac1 localization. Utilizing a novel microcontact-printing approach that lacks confounding influences of substrate dimensionality, mechanics, or differences in the adhesive area, this work highlights the effect of ECM alignment on orchestrating the cytoskeletal machinery that governs directed uniaxial cell migration.

LncRNA LINC00974 activates TGF-β/Smad signaling to promote oral fibrogenesis

BACKGROUND

Oral submucous fibrosis (OSF) is a progressive scarring disease and has been considered as a premalignant condition of the oral cavity. However, the detailed molecular mechanisms underlying the pathogenesis of OSF are still unclear.

METHOD

Here, we examined the expression of a novel long non-coding RNA LINC00974 in OSF and investigated its function role in myofibroblast transdifferentiation. Phenotypic analyses, including collagen gel contraction, migration, invasion and wound healing assays, were used to assess the myofibroblast activities following overexpression or inhibition of LINC00974.

RESULTS

We found that the expression of LINC00974 in OSF tissues or myofibroblasts was aberrantly upregulated, and there was a positive correlation between LINC00974 and myofibroblast markers. Our results showed that inhibition of LINC00974 suppressed the myofibroblast activities, while overexpression of LINC00974 increased the activation. We demonstrated that the expression levels of α-SMA, α-1 type I collagen, fibronectin were downregulated in the LINC00974-inhibited myofibroblasts. Additionally, the TGF-β secretion and phosphorylated Smad2 expression were also repressed in the LINC00974-inhibited myofibroblasts. We further demonstrated that silence of LINC00974 prevented the arecoline-induced myofibroblast activation, and LINC00974-increased myofibroblast activities were via TGF-β pathway.

CONCLUSION

Altogether, these findings suggested that arecoline-increased myofibroblast transdifferentiation was via LINC00974-mediated activation of TGF-β signaling.

The effects of cryotherapy on vocal fold healing in a rabbit model

OBJECTIVES/HYPOTHESIS

Cryotherapy has been shown to be a scarless treatment modality for dermal lesions; however, there are limited data addressing the effect of cryotherapy on vocal fold tissue. The aim of this study was to clarify the effectiveness of cryotherapy for prevention of postsurgical vocal fold scarring.

STUDY DESIGN

Prospective animal study in rabbits.

METHODS

The lamina propria of 20 rabbit vocal folds was bilaterally stripped, followed by randomized unilateral cryotherapy. Five larynges were harvested for real-time polymerase chain reaction (RT-PCR) analysis at 1 day, 3 days, and 7 days postinjury. The remaining five were harvested for histologic analysis at 3 months. Images of the healing phase were recorded by laryngoscopy. Analyses of RT-PCR for cyclooxygenase (COX)-2, interleukin (IL)-6, collagen I, collagen III, matrix metallopeptidase 1 (MMP1), transforming growth factor β (TGFβ1), α smooth muscle actin (α-SMA), and hyaluronan synthase 1 (HAS1) were completed. Histological samples were completed for collagen and hyaluronic acid analysis.

RESULTS

RT-PCR results revealed that higher expressions of HAS1 and MMP1 and lower expressions of COX-2, IL-6, collagen I, collagen III, TGFβ1, and α-SMA were observed, and histological examination showed significantly increased hyaluronic acid, decreased deposition, and more organized configuration of collagen in injury with the cryotherapy cohort compared with the injury cohort.

CONCLUSIONS

Cryotherapy can inhibit the inflammatory reaction and simulate a fetal healing environment in extracellular matrix synthesis to regenerate vocal fold tissue with less fibrosis. Histological results showed that cryotherapy achieves a mature healing result with less scar, which tends to return to normal. In summary, the findings of this study suggest that administration of cryotherapy at the time of injury has the potential to minimize vocal fold scarring.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E151-E157, 2019.

Cryotherapy has antifibrotic and regenerative effects on human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Vocal fold scarring remains a major treatment challenge, and scar prevention without residual lesions remains a dilemma. Cryotherapy has shown cosmetic outcomes on skin lesions with minimal scarring. The aim of this study was to clarify the beneficial effects of cryotherapy for the prevention and the treatment of vocal fold scarring.

STUDY DESIGN

In vitro.

METHODS

Primary cultures of human vocal fold fibroblasts (VFFs) were used in this study. Myofibroblast differentiation was stimulated by transforming growth factor β1 (TGF-β1). We mimicked the cryotherapy effect on vocal fold healing in vivo by freezing VFFs ± TGF-β1 in vitro. The influence of freezing on cell viability, proliferation, migration, and contractile properties were analyzed. The expression of collagen I, collagen III, fibronectin, TGF-β1, matrix metallopeptidase 1 (MMP1), hyaluronan synthase 1 (HAS1) were investigated by real-time polymerase chain reaction (RT-PCR), and the expression of alpha smooth muscle actin (α-SMA) and decorin were investigated by RT-PCR and Western blot.

RESULTS

Freezing was found to modify extracellular matrix (ECM) synthesis and differentiation of VFFs. Expression of collagen I, collagen III, fibronectin, α-SMA, and TGF-β1 was downregulated, and MMP1 was upregulated in VFFs + TGF-β1 (myofibroblast) by freezing. HAS1 and decorin were upregulated in both VFFs ± TGF-β1 by freezing. Freezing VFFs + TGF-β1 (myofibroblast) with fast thawing had a lower expression of α-SMA when compared with slow thawing. Freezing reduced the migration and collagen contraction of VFFs + TGF-β1 (myofibroblast).

CONCLUSION

Cryotherapy induces antifibrotic and regenerative ECM alterations in VFFs. These data provide insight into the prevention and the treatment of vocal fold scarring with cryotherapy in phonomicrosurgery.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E143-E150, 2019.

Gga-miR-205a Affecting Myoblast Proliferation and Differentiation by Targeting CDH11

Non-coding RNAs especially miRNAs have been found to play important roles during skeletal muscle development. Our previous RNA-Seq performed on breast muscle tissue from 7 weeks old Recessive White Rock and Xinhua Chicken and leg muscle tissue from female Xinghua Chicken at three development time points (11 embryo age, 16 embryo age, and 1 day post hatch) (accession number GSE62971 and GSE89355, respectively) showed that miR-205a and CDH11 were differentially expressed genes. In this study, we found that overexpression of CDH11 significantly facilitated Quail muscle clone (QM7) and chicken primary myoblast (CPM) proliferation and hampered CPM differentiation. MiR-205a can directly binding to the 3'UTR of CDH11 and the overexpression of miR-205a could inhibit both cell lines (QM7) and CPM proliferation, at the meantime promote the differentiation of myoblasts. The Dual-Luciferase Reporter Assay results and qRT-PCR results showed that myogenin (MyoG) could regulate the expression of miR-205a by binding to the active region of miR-205a. Altogether our data suggest that MyoG could stimulate miR-205a expression to suppress CDH11, which promotes myoblasts proliferation while represses the differentiation.

Expression of α-smooth muscle actin in the periodontal ligament during post-emergent tooth eruption

Objective This study was performed to explore the expression of α-smooth muscle actin (α-SMA) in the periodontal ligament (PDL) of young and adult rats during post-emergent tooth eruption in opposed and unopposed teeth at two time points: 3 and 15 days after antagonist loss. Methods Four-week-old (n = 20) and 22-week-old (n = 20) male Wistar rats were used. The right maxillary molar crowns were cut down. PDL samples were isolated from the first mandibular molars at two time points: 3 and 15 days after cut-down of the right maxillary molars. Quantitative reverse-transcription polymerase chain reaction and immunohistochemical staining were performed to detect differences in α-SMA expression in the PDL tissues of unopposed versus opposed molars. Results α-SMA was upregulated in the PDL of the unopposed molars in the 3-day group of young rats. The region around the root apex of the unopposed molars in this group exhibited strong immunostaining for α-SMA. The expression level and immunoreactivity of α-SMA did not differ in both time points in young controls and among all the adult groups. Conclusion α-SMA-positive myofibroblasts are implicated in post-emergent tooth eruption of unopposed molars of young animals.

RNAi screening identifies a mechanosensitive ROCK-JAK2-STAT3 network central to myofibroblast activation

Myofibroblasts play key roles in wound healing and pathological fibrosis. Here, we used an RNAi screen to characterize myofibroblast regulatory genes, using a high-content imaging approach to quantify α-smooth muscle actin stress fibers in cultured human fibroblasts. Screen hits were validated on physiological compliance hydrogels, and selected hits tested in primary fibroblasts from patients with idiopathic pulmonary fibrosis. Our RNAi screen led to the identification of STAT3 as an essential mediator of myofibroblast activation and function. Strikingly, we found that STAT3 phosphorylation, while responsive to exogenous ligands on both soft and stiff matrices, is innately active on a stiff matrix in a ligand/receptor-independent, but ROCK- and JAK2-dependent fashion. These results demonstrate how a cytokine-inducible signal can become persistently activated by pathological matrix stiffening. Consistent with a pivotal role for this pathway in driving persistent fibrosis, a STAT3 inhibitor attenuated murine pulmonary fibrosis when administered in a therapeutic fashion after bleomycin injury. Our results identify novel genes essential for the myofibroblast phenotype, and point to STAT3 as an important target in pulmonary fibrosis and other fibrotic diseases.

Identification of a small-molecule ligand of β-arrestin1 as an inhibitor of stromal fibroblast cell migration accelerated by cancer cells

Stromal fibroblasts, which occupy a major portion of the tumor microenvironment, play an important role in cancer metastasis. Thus, targeting of these fibroblasts activated by cancer cells (carcinoma‐associated fibroblasts; CAFs) might aid in the improved treatment of cancer metastasis. NIH3T3 fibroblasts cocultured with MCF7 cells displayed enhanced migration compared to NIH3T3 fibroblasts cultured alone. We used this system to identify the small‐molecule inhibitors responsible for their enhanced migration, a characteristic of CAFs. We selected β‐arrestin1, which showed high expression in cocultured cells, as a molecular target for such inhibitors. Cofilin, a protein downstream of β‐arrestin1, is activated/dephosphorylated in this condition. The small‐molecule ligands of β‐arrestin1 obtained by chemical array were then examined using a wound healing coculture assay. RKN5755 was identified as a selective inhibitor of activated fibroblasts. RKN5755 inhibited the enhanced migration of fibroblasts cocultured with cancer cells by binding to β‐arrestin1 and interfering with β‐arrestin1‐mediated cofilin signaling pathways. Therefore, these results demonstrate the role of β‐arrestin1 in the activation of fibroblasts and inhibiting this protein by small molecule inhibitor might be a potential therapeutic target for the stromal fibroblast activation (cancer–stroma interaction).

Periostin in the pathogenesis of skin diseases

Skin is an organ that is susceptible to damage by external injury, chronic inflammation, and autoimmunity. Tissue damage causes alterations in both the configuration and type of cells in lesional skin. This phenomenon, called tissue remodeling, is a universal biological response elicited by programmed cell death, inflammation, immune disorders, and tumorigenic, tumor proliferative, and cytoreductive activity. In this process, changes in the components of the extracellular matrix are required to provide an environment that facilitates tissue remodeling. Among these extracellular matrix components, periostin, a glycoprotein that is predominantly secreted from dermal fibroblasts, has attracted attention. Periostin localizes in the papillary dermis of normal skin, and is aberrantly expressed in the dermis of lesional skin in atopic dermatitis, scar, systemic/limited scleroderma, melanoma, cutaneous T cell lymphoma, and skin damage caused by allergic/autoimmune responses. Periostin induces processes that result in the development of dermal fibrosis, and activate or protract the immune response. The aim of this review was to summarize recent knowledge of the role of periostin in the pathogenesis of dermatoses, and to explore whether periostin is a potential therapeutic target for skin diseases.

On the Functional Role of Valve Interstitial Cell Stress Fibers: A Continuum Modeling Approach

The function of the heart valve interstitial cells (VICs) is intimately connected to heart valve tissue remodeling and repair, as well as the onset and progression of valvular pathological processes. There is yet only very limited knowledge and extant models for the complex three-dimensional VIC internal stress-bearing structures, the associated cell-level biomechanical behaviors, and how they change under varying activation levels. Importantly, VICs are known to exist and function within the highly dynamic valve tissue environment, including very high physiological loading rates. Yet we have no knowledge on how these factors affect VIC function. To this end, we extended our previous VIC computational continuum mechanics model (Sakamoto, et al., 2016, "On Intrinsic Stress Fiber Contractile Forces in Semilunar Heart Valve Interstitial Cells Using a Continuum Mixture Model," J. Mech. Behav. Biomed. Mater., 54(244-258)). to incorporate realistic stress-fiber geometries, force-length relations (Hill model for active contraction), explicit α-smooth muscle actin (α-SMA) and F-actin expression levels, and strain rate. Novel micro-indentation measurements were then performed using cytochalasin D (CytoD), variable KCl molar concentrations, both alone and with transforming growth factor β1 (TGF-β1) (which emulates certain valvular pathological processes) to explore how α-SMA and F-actin expression levels influenced stress fiber responses under quasi-static and physiological loading rates. Simulation results indicated that both F-actin and α-SMA contributed substantially to stress fiber force generation, with the highest activation state (90 mM KCL + TGF-β1) inducing the largest α-SMA levels and associated force generation. Validation was performed by comparisons to traction force microscopy studies, which showed very good agreement. Interestingly, only in the highest activation state was strain rate sensitivity observed, which was captured successfully in the simulations. These unique findings demonstrated that only VICs with high levels of αSMA expression exhibited significant viscoelastic effects. Implications of this study include greater insight into the functional role of α-SMA and F-actin in VIC stress fiber function, and the potential for strain rate-dependent effects in pathological states where high levels of α-SMA occur, which appear to be unique to the valvular cellular in vivo microenvironment.

Reactive Oxygen Species and NOX Enzymes Are Emerging as Key Players in Cutaneous Wound Repair

Our understanding of the role of oxygen in cell physiology has evolved from its long-recognized importance as an essential factor in oxidative metabolism to its recognition as an important player in cell signaling. With regard to the latter, oxygen is needed for the generation of reactive oxygen species (ROS), which regulate a number of different cellular functions including differentiation, proliferation, apoptosis, migration, and contraction. Data specifically concerning the role of ROS-dependent signaling in cutaneous wound repair are very limited, especially regarding wound contraction. In this review we provide an overview of the current literature on the role of molecular and reactive oxygen in the physiology of wound repair as well as in the pathophysiology and therapy of chronic wounds, especially under ischemic and hyperglycemic conditions.

MMI-0100 Inhibits Cardiac Fibrosis in a Mouse Model Overexpressing Cardiac Myosin Binding Protein C

Background

Cardiac stress can trigger production of a 40‐kDa peptide fragment derived from the amino terminus of the cardiac myosin‐binding protein C. Cardiac stress, as well as cMyBP‐C mutations, can trigger production of 1 such truncated protein fragment, a 40‐kDa peptide fragment derived from the amino terminus of cMyBP‐C. Genetic expression of this 40‐kDa fragment in mouse cardiomyocytes (cMyBP‐C^40k) leads to cardiac disease, fibrosis, and death within the first year. Fibrosis can occur in many cardiovascular diseases, and mitogen‐activated protein kinase––activated protein kinase‐2 signaling has been implicated in a variety of fibrotic processes. Recent studies demonstrated that mitogen‐activated protein kinase––activated protein kinase‐2 inhibition using the cell‐permeant peptide inhibitor MMI‐0100 is protective in the setting of acute myocardial infarction. We hypothesized that MMI‐0100 might also be protective in a chronic model of fibrosis, produced as a result of cMyBP‐C^40k cardiomyocyte expression.

Methods and Results

Nontransgenic and cMyBP‐C^40k inducible transgenic mice were given MMI‐0100 or PBS daily for 30 weeks. In control groups, long‐term MMI‐0100 was benign, with no measurable effects on cardiac anatomy, function, cell viability, hypertrophy, or probability of survival. In the inducible transgenic group, MMI‐0100 treatment reduced cardiac fibrosis, decreased cardiac hypertrophy, and prolonged survival.

Conclusions

Pharmaceutical inhibition of mitogen‐activated protein kinase––activated protein kinase‐2 signaling via MMI‐0100 treatment is beneficial in the context of fibrotic cMyBPC^40k disease.

Myofibroblast transdifferentiation: The dark force in ocular wound healing and fibrosis

Wound healing is one of the most complex biological processes to occur in life. Repair of tissue following injury involves dynamic interactions between multiple cell types, growth factors, inflammatory mediators and components of the extracellular matrix (ECM). Aberrant and uncontrolled wound healing leads to a non-functional mass of fibrotic tissue. In the eye, fibrotic disease disrupts the normally transparent ocular tissues resulting in irreversible loss of vision. A common feature in fibrotic eye disease is the transdifferentiation of cells into myofibroblasts that can occur through a process known as epithelial-mesenchymal transition (EMT). Myofibroblasts rapidly produce excessive amounts of ECM and exert tractional forces across the ECM, resulting in the distortion of tissue architecture. Transforming growth factor-beta (TGFβ) plays a major role in myofibroblast transdifferentiation and has been implicated in numerous fibrotic eye diseases including corneal opacification, pterygium, anterior subcapsular cataract, posterior capsular opacification, proliferative vitreoretinopathy, fibrovascular membrane formation associated with proliferative diabetic retinopathy, submacular fibrosis, glaucoma and orbital fibrosis. This review serves to introduce the pathological functions of the myofibroblast in fibrotic eye disease. We also highlight recent developments in elucidating the multiple signaling pathways involved in fibrogenesis that may be exploited in the development of novel anti-fibrotic therapies to reduce ocular morbidity due to scarring.

Mechanotransduction Dynamics at the Cell-Matrix Interface

The ability of cells to sense and respond to mechanical cues from the surrounding environment has been implicated as a key regulator of cell differentiation, migration, and proliferation. The extracellular matrix (ECM) is an oft-overlooked component of the interface between cells and their surroundings. Cells assemble soluble ECM proteins into insoluble fibrils with unique mechanical properties that can alter the mechanical cues a cell receives. In this study, we construct a model that predicts the dynamics of cellular traction force generation and subsequent assembly of fibrils of the ECM protein fibronectin (FN). FN fibrils are the primary component in primordial ECM and, as such, FN assembly is a critical component in the cellular mechanical response. The model consists of a network of Hookean springs, each representing an extensible domain within an assembling FN fibril. As actomyosin forces stretch the spring network, simulations predict the resulting traction force and FN fibril formation. The model accurately predicts FN fibril morphometry and demonstrates a mechanism by which FN fibril assembly regulates traction force dynamics in response to mechanical stimuli and varying surrounding substrate stiffness.

SH2 Domain-Containing Phosphatase-2 Is a Novel Antifibrotic Regulator in Pulmonary Fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal lung disease with dismal prognosis and no cure. The potential role of the ubiquitously expressed SH2 domain-containing tyrosine phosphatase-2 (SHP2) as a therapeutic target has not been studied in IPF.

OBJECTIVES

To determine the expression, mechanistic role, and potential therapeutic usefulness of SHP2 in pulmonary fibrosis.

METHODS

The effects of SHP2 overexpression and inhibition on fibroblast response to profibrotic stimuli were analyzed in vitro in primary human and mouse lung fibroblasts. In vivo therapeutic effects were assessed in the bleomycin model of lung fibrosis by SHP2-lentiviral administration and transgenic mice carrying a constitutively active SHP2 mutation.

MEASUREMENTS AND MAIN RESULTS

SHP2 was down-regulated in lungs and lung fibroblasts obtained from patients with IPF. Immunolocalization studies revealed that SHP2 was absent within fibroblastic foci. Loss of SHP2 expression or activity was sufficient to induce fibroblast-to-myofibroblast differentiation in primary human lung fibroblasts. Overexpression of constitutively active SHP2 reduced the responsiveness of fibroblasts to profibrotic stimuli, including significant reductions in cell survival and myofibroblast differentiation. SHP2 effects were mediated through deactivation of fibrosis-relevant tyrosine kinase and serine/threonine kinase signaling pathways. Mice carrying the Noonan syndrome-associated gain-of-function SHP2 mutation (SHP2^D61G/+) were resistant to bleomycin-induced pulmonary fibrosis. Restoration of SHP2 levels in vivo through lentiviral delivery blunted bleomycin-induced pulmonary fibrosis.

CONCLUSIONS

Our data suggest that SHP2 is an important regulator of fibroblast differentiation, and its loss as observed in IPF facilitates profibrotic phenotypic changes. Augmentation of SHP2 activity or expression should be investigated as a novel therapeutic strategy for IPF.

Talin2-mediated traction force drives matrix degradation and cell invasion

Talin binds to β-integrin tails to activate integrins, regulating cell migration, invasion and metastasis. There are two talin genes, TLN1 and TLN2, encoding talin1 and talin2, respectively. Talin1 regulates focal adhesion dynamics, cell migration and invasion, whereas the biological function of talin2 is not clear and, indeed, talin2 has been presumed to function redundantly with talin1. Here, we show that talin2 has a much stronger binding to β-integrin tails than talin1. Replacement of talin2 Ser339 with Cys significantly decreased its binding to β1-integrin tails to a level comparable to that of talin1. Talin2 localizes at invadopodia and is indispensable for the generation of traction force and invadopodium-mediated matrix degradation. Ablation of talin2 suppressed traction force generation and invadopodia formation, which were restored by re-expressing talin2 but not talin1. Furthermore, re-expression of wild-type talin2 (but not talin2^S339C) in talin2-depleted cells rescued development of traction force and invadopodia. These results suggest that a strong interaction of talin2 with integrins is required to generate traction, which in turn drives invadopodium-mediated matrix degradation, which is key to cancer cell invasion.

Exercise prior to, but not concomitant with, stress reverses stress-induced delayed skin wound healing

Stress-induced prolonged inflammation impairs cutaneous wound healing. Exercise may inhibit this effect via an anti-inflammatory mechanism. Our aim was to investigate the effect of moderate exercise on skin wound healing in chronically stressed mice. Mice were trained five times per week on a treadmill or received no training. Mice underwent daily rotational stress from the 6th week until euthanasia. During the 8th week, two wounds were created in the dorsum and collected 10 days later. A control group only received wounds. Exercise was performed prior to and simultaneous with stress for 2 weeks or only prior to stress. Stress increased normetanephrine levels 10 days after wounding, resulting in an increased amount of inflammatory cells and reduced expression of inflammatory cytokines as well as angiogenesis, myofibroblast differentiation and matrix deposition. Concomitant exercise and stress potentiated these effects, intensifying the delayed wound contraction. When exercise was performed only prior to stress, however, the mice showed reduced inflammatory cells in granulation tissue 10 days after wounding and improved wound healing compared with animals with exercise and concomitant stress. Moderate exercise in association with stress potentiates the stress effect; however, when exercise was performed prior to stress, wound healing was improved.

Intermittent pacing therapy favorably modulates infarct remodeling

Despite early revascularization, remodeling and dysfunction of the left ventricle (LV) after acute myocardial infarction (AMI) remain important therapeutic targets. Intermittent pacing therapy (IPT) of the LV can limit infarct size, when applied during early reperfusion. However, the effects of IPT on post-AMI LV remodeling and infarct healing are unknown. We therefore investigated the effects of IPT on global LV remodeling and infarct geometry in swine with a 3-day old AMI. For this purpose, fifteen pigs underwent 2 h ligation of the left circumflex coronary artery followed by reperfusion. An epicardial pacing lead was implanted in the peri-infarct zone. After three days, global LV remodeling and infarct geometry were assessed using magnetic resonance imaging (MRI). Animals were stratified into MI control and IPT groups. Thirty-five days post-AMI, follow-up MRI was obtained and myofibroblast content, markers of extracellular matrix (ECM) turnover and Wnt/frizzled signaling in infarct and non-infarct control tissue were studied. Results showed that IPT had no significant effect on global LV remodeling, function or infarct mass, but modulated infarct healing. In MI control pigs, infarct mass reduction was principally due to a 26.2 ± 4.4% reduction in infarct thickness (P ≤ 0.05), whereas in IPT pigs it was mainly due to a 35.7 ± 4.5% decrease in the number of infarct segments (P ≤ 0.05), with no significant change in infarct thickness. Myofibroblast content of the infarct zone was higher in IPT (10.9 ± 2.1%) compared to MI control (5.4 ± 1.6%; P ≤ 0.05). Higher myofibroblast presence did not coincide with alterations in expression of genes involved in ECM turnover or Wnt/frizzled signaling at 5 weeks follow-up. Taken together, IPT limited infarct expansion and altered infarct composition, showing that IPT influences remodeling of the infarct zone, likely by increasing regional myofibroblast content.

Provisional matrix: A role for versican and hyaluronan

Hyaluronan and versican are extracellular matrix (ECM) components that are enriched in the provisional matrices that form during the early stages of development and disease. These two molecules interact to create pericellular "coats" and "open space" that facilitate cell sorting, proliferation, migration, and survival. Such complexes also impact the recruitment of leukocytes during development and in the early stages of disease. Once thought to be inert components of the ECM that help hold cells together, it is now quite clear that they play important roles in controlling cell phenotype, shaping tissue response to injury and maintaining tissue homeostasis. Conversion of hyaluronan-/versican-enriched provisional matrix to collagen-rich matrix is a "hallmark" of tissue fibrosis. Targeting the hyaluronan and versican content of provisional matrices in a variety of diseases including, cardiovascular disease and cancer, is becoming an attractive strategy for intervention.

Myofibroblasts in Palatal Wound Healing: Prospects for the Reduction of Wound Contraction after Cleft Palate Repair

The surgical closure of orofacial clefts is considered to impair maxillary growth and dento-alveolar development. Wound contraction and subsequent scar tissue formation, during healing of these surgical wounds, contribute largely to these growth disturbances. The potential to minimize wound contraction and subsequent scarring by clinical interventions depends on the surgeon’s knowledge of the events responsible for these phenomena. Fibroblasts initiate wound contraction, but proto-myofibroblasts and mature myofibroblasts are by far the most important cells in this process. Myofibroblasts are characterized by their cytoskeleton, which contains alpha-smooth-muscle actin. Additionally, their contractile apparatus contains bundles of actin microfilaments and associated contractile proteins, such as non-muscle myosin. This contractile apparatus is thought to be the major force-generating element involved in wound contraction. After closure of the wound, the myofibroblasts disappear by apoptosis, and a less cellular scar is formed. A reduction of contraction and scarring might be obtained by inhibition of myofibroblast differentiation, stimulation of their de-differentiation, stimulation of myofibroblast apoptosis, or impairment of myofibroblast function. In this review, we will discuss all of these possibilities, which ultimately may lead to a better outcome of cleft palate surgery.

Semaphorin 4A enhances lung fibrosis through activation of Akt via PlexinD1 receptor

Semaphorin 4A plays a regulatory role in immune function and angiogenesis. However, its specific involvement in controlling lung fibrosis, a process that is closely related to angiogenesis and inflammation is still poorly understood. In the present study, we show that treatment of Sema4A on normal lung fibroblasts induces expression of proteins that contribute to a contractile phenotype, including alpha-smooth muscle actin (alpha-SMA), ezrin, moesin, and paxillin. We confirm that Sema4A enhances the ability of lung fibroblasts to contract collagen gel. Sema4A treatment led to resistance to apoptosis in normal lung fibroblasts. Relative to normal lung fibroblasts, fibroblasts cultured from scars of patients with the fibrotic disease Systemic Sclerosis (SSc) showed elevated Sema4A secretion, enhanced alpha-SMA, ezrin, moesin, and paxillin expression, and high ability to induce collagen gel contraction. Using neutralizing antibody against Sema4A receptor, PlexinD1, we found that endogenous Sema4A signalling in SSc fibroblast was through PlexinD1 receptor. We then identified the signalling mechanism through which Sema4A-PlexinD1 promotes the ability of normal fibroblasts to contract a collagen gel matrix. Western blot analysis showed that Sema4A activated the Akt pathway in lung fibroblasts, and the specific inhibitor of Akt pathway, Akt inhibitor III, blocked the ability of Sema4A to promote the ability of lung fibroblasts to contract a collagen gel matrix. Thus, blocking Sema4APlexinD1- Akt cascades might be beneficial in reducing pulmonary fibrosis.

Pathology and biology of radiation-induced cardiac disease

Heart disease is the leading global cause of death. The risk for this disease is significantly increased in populations exposed to ionizing radiation, but the mechanisms are not fully elucidated yet. This review aims to gather and discuss the latest data about pathological and biological consequences in the radiation-exposed heart in a comprehensive manner. A better understanding of the molecular and cellular mechanisms underlying radiation-induced damage in heart tissue and cardiac vasculature will provide novel targets for therapeutic interventions. These may be valuable for individuals clinically or occupationally exposed to varying doses of ionizing radiation.

Collective epithelial cell sheet adhesion and migration on polyelectrolyte multilayers with uniform and gradients of compliance

Polyelectrolyte multilayers (PEMUs) are tunable thin films that could serve as coatings for biomedical implants. PEMUs built layer by layer with the polyanion poly(acrylic acid) (PAA) modified with a photosensitive 4-(2-hydroxyethoxy) benzophenone (PAABp) group and the polycation poly(allylamine hydrochloride) (PAH) are mechanically tunable by UV irradiation, which forms covalent bonds between the layers and increases PEMU stiffness. PAH-terminated PEMUs (PAH-PEMUs) that were uncrosslinked, UV-crosslinked to a uniform stiffness, or UV-crosslinked with an edge mask or through a neutral density optical gradient filter to form continuous compliance gradients were used to investigate how differences in PEMU stiffness affect the adhesion and migration of epithelial cell sheets from scales of the fish Poecilia sphenops (Black Molly) and Carassius auratus (Comet Goldfish). During the progressive collective cell migration, the edge cells (also known as 'leader' cells) in the sheets on softer uncrosslinked PEMUs and less crosslinked regions of the gradient formed more actin filaments and vinculin-containing adherens junctions and focal adhesions than formed in the sheet cells on stiffer PEMUs or glass. During sheet migration, the ratio of edge cell to internal cell (also known as 'follower' cells) motilities were greater on the softer PEMUs than on the stiffer PEMUs or glass, causing tension to develop across the sheet and periods of retraction, during which the edge cells lost adhesion to the substrate and regions of the sheet retracted toward the more adherent internal cell region. These retraction events were inhibited by the myosin II inhibitor Blebbistatin, which reduced the motility velocity ratios to those for sheets on the stiffer PEMUs. Blebbistatin also caused disassembly of actin filaments, reorganization of focal adhesions, increased cell spreading at the leading edge, as well as loss of edge cell-cell connections in epithelial cell sheets on all surfaces. Interestingly, cells throughout the interior region of the sheets on uncrosslinked PEMUs retained their actin and vinculin organization at adherens junctions after treatment with Blebbistatin. Like Blebbistatin, a Rho-kinase (ROCK) inhibitor, Y27632, promoted loss of cell-cell connections between edge cells, whereas a Rac1 inhibitor, NSC23766, primarily altered the lamellipodial protrusion in edge cells. Compliance gradient PAH-PEMUs promoted durotaxis of the cell sheets but not of individual keratocytes, demonstrating durotaxis, like plithotaxis, is an emergent property of cell sheet organization.

Periostin as a multifunctional modulator of the wound healing response

During tissue healing, the dynamic and temporal alterations required for effective repair occur in the structure and composition of the extracellular matrix (ECM). Matricellular proteins (MPs) are a group of diverse non-structural ECM components that bind cell surface receptors mediating interactions between the cell and its microenviroment, effectively regulating adhesion, migration, proliferation, signaling, and cell phenotype. Periostin (Postn), a pro-fibrogenic secreted glycoprotein, is defined as an MP based on its expression pattern and regulatory roles during development and healing and in disease processes. Postn consists of a typical signal sequence, an EMI domain responsible for binding to fibronectin, four tandem fasciclin-like domains that are responsible for integrin binding, and a C-terminal region in which multiple splice variants originate. This review focuses specifically on the role of Postn in wound healing and remodeling, an area of intense research during the last 10 years, particularly as related to skin healing and myocardium post-infarction. Postn interacts with cells through various integrin pairs and is an essential downstream effector of transforming growth factor-β superfamily signaling. Across various tissues, Postn is associated with the pro-fibrogenic process: specifically, the transition of fibroblasts to myofibroblasts, collagen fibrillogenesis, and ECM synthesis. Although the complexity of Postn as a modulator of cell behavior in tissue healing is only beginning to be elucidated, its expression is clearly a defining event in moving wound healing through the proliferative and remodeling phases.

Stromal dynamic reciprocity in cancer: intricacies of fibroblastic-ECM interactions

Stromal dynamic reciprocity (SDR) consists of the biophysical and biochemical interplay between connective tissue elements that regulate and maintain organ homeostasis. In epithelial cancers, chronic alterations of SDR result in the once tumor-restrictive stroma evolving into a 'new' tumor-permissive environment. This altered stroma, known as desmoplasia, is initiated and maintained by cancer associated fibroblasts (CAFs) that remodel the extracellular matrix (ECM). Desmoplasia fuels a vicious cycle of stromal dissemination enriching both CAFs and desmoplastic ECM. Targeting specific drivers of desmoplasia, such as CAFs, either enhances or halts tumor growth and progression. These conflicting effects suggest that stromal interactions are not fully understood. This review highlights known fibroblastic-ECM interactions in an effort to encourage therapies that will restore cancer-restrictive stromal cues.

The Application of Ultrasound in 3D Bio-Printing

Three-dimensional (3D) bioprinting is an emerging and promising technology in tissue engineering to construct tissues and organs for implantation. Alignment of self-assembly cell spheroids that are used as bioink could be very accurate after droplet ejection from bioprinter. Complex and heterogeneous tissue structures could be built using rapid additive manufacture technology and multiple cell lines. Effective vascularization in the engineered tissue samples is critical in any clinical application. In this review paper, the current technologies and processing steps (such as printing, preparation of bioink, cross-linking, tissue fusion and maturation) in 3D bio-printing are introduced, and their specifications are compared with each other. In addition, the application of ultrasound in this novel field is also introduced. Cells experience acoustic radiation force in ultrasound standing wave field (USWF) and then accumulate at the pressure node at low acoustic pressure. Formation of cell spheroids by this method is within minutes with uniform size and homogeneous cell distribution. Neovessel formation from USWF-induced endothelial cell spheroids is significant. Low-intensity ultrasound could enhance the proliferation and differentiation of stem cells. Its use is at low cost and compatible with current bioreactor. In summary, ultrasound application in 3D bio-printing may solve some challenges and enhance the outcomes.

Apoptosis or senescence? Which exit route do epithelial cells and fibroblasts preferentially follow?

Senescence and apoptosis constitute types of cellular responses that normally ensure homeostasis, when endogenous or exogenous signals occur. Their deregulation is often observed in various pathologies, such as age and non-age related diseases including cancer. Although epithelial cells and fibroblasts are capable to exert both functions, under a plethora of insults, the fact that they exhibit notable intrinsic differences in cell/tissue homeostasis properties, might be a crucial determinant of the mode of response to a certain stress signal. Sparse evidence in the literature reveals that in the same tissue/organ context and under the same conditions, the cell type seems to drive the differential counteraction between epithelia and fibroblasts. Based on the above notion we propose that, upon stress insults, human fibroblasts seem to predominantly respond via senescence, while epithelial cells prefer to exert apoptosis. We suggest that considering the tissue as a whole (epithelium and stroma) would benefit research into new therapeutic strategies for chronic diseases and cancer.

Kynurenine Modulates MMP-1 and Type-I Collagen Expression Via Aryl Hydrocarbon Receptor Activation in Dermal Fibroblasts

Dermal fibrosis is characterized by a high deposition of extracellular matrix (ECM) and tissue cellularity. Unfortunately all means of treating this condition are unsatisfactory. We have previously reported the anti-fibrotic effects of Kynurenine (Kyn), a tryptophan metabolite, in fibrotic rabbit ear model. Here, we report the mechanism by which Kyn modulates the expression of key ECM components in dermal fibroblasts. The results showed that Kyn activates aryl hydrocarbon receptor (AHR) nuclear translocation and up-regulates cytochrome-P450 (CYP1A-1) expression, the AHR target gene. A specific AHR antagonist, 6,2',4'-trimethoxyflavone, inhibited the Kyn-dependent modulation of CYP1A-1, MMP-1, and type-I collagen expression. Establishing the anti-fibrogenic effect of Kyn and its mechanism of action, we then developed nano-fibrous Kyn slow-releasing dressings and examined their anti-fibrotic efficacy in vitro and in a rat model. Our results showed the feasibility of incorporating Kyn into PVA/PLGA nanofibers, prolonging the Kyn release up to 4 days tested. Application of medicated-dressings significantly improved the dermal fibrosis indicated by MMP-1 induction, alpha-smooth muscle actin and type-I collagen suppression, and reduced tissue cellularity, T-cells and myofibroblasts. This study clarifies the mechanism by which Kyn modulates ECM expression and reports the development of a new slow-releasing anti-fibrogenic dressing. J. Cell. Physiol. 231: 2749-2760, 2016. © 2016 Wiley Periodicals, Inc.

Myofascial techniques: What are their effects on joint range of motion and pain? - A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

This systematic review aimed to determine the evidence for the effect of a single manually applied myofascial technique (MFT) on joint range of motion (JROM) and pain in non-pathological symptomatic subjects.

METHODS

Authors independently searched the following databases: PEDro; Cochrane Library; NLM PubMed; EMBASE; Academic Search Premier; MEDLINE; Psychology and Behavioural Sciences Collection; PsycINFO; SPORTSDiscus; CINAHL Plus from 2003 to 2015. All randomised controlled trials (RCTs) that used JROM as an outcome measure were identified. RCT quality was independently evaluated using PEDro and Cochrane Risk of Bias tools and all reported outcome data were independently abstracted and presented. If post-intervention central tendencies and variance were reported, these were assessed for heterogeneity with a view to performing a meta-analysis.

RESULTS

Nine RCTs (n = 534) were systematically reviewed and outcome data presented; all trials concluded that MFT increased JROM and reduced pain levels in symptomatic patients. Two RCTs (n = 161) were judged 'moderately' heterogeneous (I(2) = 47.2%; Cochran's Q = 5.69; p = 0.128, df = 3) and meta-analysis using a fixed effects model suggested a 'moderate' effect size of MFTs on jaw opening (ES = 0.578; 95%CI 0.302 to 0.853).

CONCLUSION

Although results reported by each RCT indicate that MFT increases JROM and reduces pain scores, there are a number of threats that challenge the statistical inferences underpinning these findings. Only two trials could be meta-analysed, the results of which suggest that applying MFTs to symptomatic patients diagnosed with latent trigger-points in masseter muscle can increase jaw JROM.

Suppression of α Smooth Muscle Actin Accumulation by Bovine Fetal Dermal Collagen Matrix in Full Thickness Skin Wounds

The suppression of elements associated with wound contracture and unfavorable scarring is a potentially important strategy in clinical wound management. In this study, the presence of α smooth muscle actin (αSMA), a protein involved in wound contraction, was analyzed in a series of wounds in which bovine fetal collagen (BFC) acellular dermal matrix (PriMatrix) was used in staged split thickness skin graft procedures. The results obtained through histological and quantitative image analyses of incidental biopsies from these wounds demonstrated a suppression of αSMA in the wound regions occupied by assimilated BFC relative to increased levels of αSMA found in other areas of the wound. The αSMA levels found in assimilated BFC were similar to αSMA levels in uninjured human dermis. These findings suggest a mechanism by which application of BFC could decrease contraction of full thickness skin wounds.

A Combined In Vitro Imaging and Multi-Scale Modeling System for Studying the Role of Cell Matrix Interactions in Cutaneous Wound Healing

Many cell types remodel the extracellular matrix of the tissues they inhabit in response to a wide range of environmental stimuli, including mechanical cues. Such is the case in dermal wound healing, where fibroblast migrate into and remodel the provisional fibrin matrix in a complex manner that depends in part on the local mechanical environment and the evolving multi-scale mechanical interactions of the system. In this study, we report on the development of an image-based multi-scale mechanical model that predicts the short-term (24 hours), structural reorganization of a fibrin gel by fibroblasts. These predictive models are based on an in vitro experimental system where clusters of fibroblasts (i.e., explants) were spatially arranged into a triangular geometry onto the surface of fibrin gels that were subjected to either Fixed or Free in-plane mechanical constraints. Experimentally, regional differences in short-term structural remodeling and cell migration were observed for the two gel boundary conditions. A pilot experiment indicated that these small differences in the short-term remodeling of the fibrin gel translate into substantial differences in long-term (4 weeks) remodeling, particularly in terms of collagen production. The multi-scale models were able to predict some regional differences in remodeling and qualitatively similar reorganization patterns for the two boundary conditions. However, other aspects of the model, such as the magnitudes and rates of deformation of gel, did not match the experiments. These discrepancies between model and experiment provide fertile ground for challenging model assumptions and devising new experiments to enhance our understanding of how this multi-scale system functions. These efforts will ultimately improve the predictions of the remodeling process, particularly as it relates to dermal wound healing and the reduction of patient scarring. Such models could be used to recommend patient-specific mechanical-based treatment dependent on parameters such as wound geometry, location, age, and health.