Myofibroblasts

When fed high fat diets, male LDLR-/- mice develop obesity, hyperlipidemia, hyperglycemia, and arteriosclerotic calcification. An osteogenic Msx-Wnt regulatory program is concomitantly upregulated in the vasculature. To better understand the mechanisms of diabetic arteriosclerosis, we generated SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- mice, assessing the impact of Msx1+Msx2 gene deletion in vascular myofibroblast and smooth muscle cells. Aortic Msx2 and Msx1 were decreased by 95% and 34% in SM22Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- animals, respectively, vs. Msx1(fl/fl);Msx2(fl/fl);LDLR-/- controls. Aortic calcium was reduced by 31% and pulse wave velocity - an index of stiffness - was decreased in SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- mice vs. controls. Fasting blood glucose and lipids did not differ, yet SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- siblings became more obese. Aortic adventitial myofibroblasts from SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- mice exhibited reduced osteog...

Negative-pressure wound therapy (NPWT) has significantly improved healing rates and patient comfort since its inception. However, a considerable number of questions have been raised regarding its mechanisms of action. Many health care workers and researchers have attempted to clarify the role of NPWT in wound healing. The purpose of this perspective article is to assemble some of the concepts that have been put forward in order to propose an integrated view of the mechanisms involved in NPWT. Particular emphasis will be placed on mechanically induced tissue deformations and their involvement in some of the key processes of wound healing, including nutrient and oxygen transport, blood vessel formation, and cellular proliferation and differentiation, mainly of myofibroblasts.

Laser and LED phototherapies accelerate tissue repair. Mast cells induce the proliferation of fibroblasts and the development of local fibrosis. Increased numbers of myofibroblasts and mast cells are frequently found together in a normal wound repair, suggesting that mediators produced by the mast cells could play a role in the regulation of myofibroblast differentiation and function. The aim of this study was to analyze the involvement of mast cells on the synthesis of collagen and their influence on myofibroblast differentiation in the late phase of tissue repair on wounds treated with LLLT (λ 660 nm, 10 J/cm2, 40 mW, 252 s) or LED (λ 630 ± 10 nm, 10 J/cm2, 115 mW, 87 s). A 1 × 1-cm surgical wound was created on the dorsum of 30 rats divided into three groups of ten animals each: control, laser, and LED. The animals of each group were irradiated and sacrificed 7 and 14 days after injury. The statistical analysis was performed using the Mann–Whitney and Spearman correlation tests. Laser light improved the collagen deposition rate along the time points (p = 0.22), but when compared to the control groups during the periods studied, the number of mast cells decreased significantly (p ≤ 0.05). With respect to myofibroblasts, the results showed a trend to their reduction. No statistical significances were observed for LED light according to the parameters used in this study. It is concluded that the mast cell and myofibroblast population might participate in the collagen formation of irradiated wounds particularly in relation to laser phototherapy.

Myofibroblasts, the culprit of organ fibrosis, can originate from mesenchymal and epithelial precursors through fibroblast–myofibroblast and epithelial–myofibroblast transition (EMyT). Because certain ciliopathies are associated with fibrogenesis, we sought to explore the fate and potential role of the primary cilium during myofibroblast formation. Here we show that myofibroblast transition from either precursor results in the loss of the primary cilium. During EMyT, initial cilium growth is followed by complete deciliation. Both EMyT and cilium loss require two-hit conditions: disassembly/absence of intercellular contacts and transforming growth factor-β1 (TGFβ) exposure. Loss of E-cadherin–dependent junctions induces cilium elongation, whereas both stimuli are needed for deciliation. Accordingly, in a scratch-wounded epithelium, TGFβ provokes cilium loss exclusively along the wound edge. Increased contractility, a key myofibroblast feature, is necessary and sufficient for deciliat...

Recent studies have shown that vagus nerve activation inhibits cytokine production in a variety of non-neural cells though activation of α7 nicotinic acetylcholine receptor (α7nAChR). Since chronic inflammation plays a pivotal role in liver fibrosis, this study was designed to investigate the role of hepatic vagus nerve in the progression of hepatic fibrosis in rats. Cirrhosis was induced by chronic ligation of the bile duct. Hepatic hydroxyproline level, portal pressure, serum transaminase level, hepatic TIMP-1 (tissue inhibitor of metalloproteinase-1) and MCP-1 (monocyte chemoattractant peptide-1) expression were measured in order to assess the progression of liver cirrhosis. α7nAChR expression was assessed using RT-PCR as well as immunostaining. RT-PCR analysis of the liver showed that α7nAChR mRNA is expressed in rat liver. Immunostaining study demonstrated that hepatic α7nAChR is mainly expressed in the hepatocytes of cirrhotic liver with minimum α7nAChR expression in biliary e...

From the histological point of view, fascia lata is a dense connective tissue. Although extracellular matrix is certainly the most predominant fascia’s feature, there are also several cell populations encountered within this structure. The aim of this study was to describe the existence and characteristics of fascia lata cell populations viewed through a transmission electron microscope. Special emphasis was placed on telocytes as a particular interstitial cell type, recently discovered in a wide variety of tissues and organs such as the heart, skeletal muscles, skin, gastrointestinal tract, uterus and urinary system. The conducted study confirmed the existence of a telocyte population in fascia lata samples. Those cells fulfil main morphological criteria of telocytes, namely, the presence of very long, thin cell processes (telopodes) extending from a relatively small cell body. Aside from telocytes, we have found fibroblasts, mast cells and cells with features of myofibroblastic differentiation. This is the first time it has been shown that telocytes exist in human fascia. Currently, the exact role of those cells within the fascia is unknown and definitely deserves further attention. One can speculate that fascia lata telocytes likewise telocytes in other organs may be involved in regeneration, homeostasis and intracellular signalling.

Chronic organ injury leads to fibrosis and eventually organ failure. Fibrosis is characterized
by excessive synthesis, remodeling, and contraction of extracellular matrix produced by
myofibroblasts. Myofibroblasts are the key cells in the pathophysiology of fibrotic disorders
and their differentiation can be triggered by multiple stimuli. To develop anti-fibrotic
therapies, it is of paramount importance to understand the molecular basis of the signaling
pathways contributing to the activation and maintenance of myofibroblasts. Several
signal transduction pathways, such as transforming growth factor (TGF)-β, Wingless/Int
(WNT), and more recently yes-associated protein 1 (YAP)/transcriptional coactivator with
PDZ-binding motif (TAZ) signaling, have been linked to the pathophysiology of fibrosis.
Activation of the TGF-β1-induced SMAD complex results in the upregulation of genes
important for myofibroblast function. Similarly, WNT-stabilized β-catenin translocates
to the nucleus and initiates transcription of its target genes. YAP and TAZ are two
transcriptional co-activators from the Hippo signaling pathway that also rely on nuclear
translocation for their functioning. These three signal transduction pathways have little
molecular similarity but do share one principle: the cytosolic/nuclear regulation of its
transcriptional activators. Past research on these pathways often focused on the isolated
cascades without taking other signaling pathways into account. Recent developments
show that parts of these pathways converge into an intricate network that governs the
activation and maintenance of the myofibroblast phenotype. In this review, we discuss
the current understanding on the signal integration between the TGF-β, WNT, and YAP/
TAZ pathways in the development of organ fibrosis. Taking a network-wide view on
signal transduction will provide a better understanding on the complex and versatile
processes that underlie the pathophysiology of fibrotic disorders.

We previously reported in vitro maintenance and proliferation of human small intestinal epithelium using Matrigel, a proprietary basement membrane product. There are concerns over the applicability of Matrigel-based methods for future human therapies. We investigated type I collagen as an alternative for the culture of human intestinal epithelial cells. Human small intestine was procured from fresh surgical pathology specimens. Small intestinal crypts were isolated using EDTA chelation. Intestinal subepithelial myofibroblasts were isolated from a pediatric sample and expanded in vitro. After suspension in Matrigel or type I collagen gel, crypts were co-cultured above a confluent layer of myofibroblasts. Crypts were also grown in monoculture with exposure to myofibroblast conditioned media; these were subsequently sub-cultured in vitro and expanded with a 1∶2 split ratio. Cultures were assessed with light microscopy, RT-PCR, histology, and immunohistochemistry. Collagen supported via...

Induction of epithelial–myofibroblast transition (EMyT), a robust fibrogenic phenotype change hallmarked by α-smooth muscle actin (SMA) expression, requires transforming growth factor-β1 (TGFβ) and the absence/uncoupling of intracellular contacts. This suggests that an “injured” epithelium may be topically susceptible to TGFβ. To explore this concept, we use an epithelial wound model in which intact and contact-deprived regions of the same monolayer can be analyzed simultaneously. We show that TGFβ elicits dramatically different responses at these two loci. SMA expression and initially enhanced nuclear Smad3 accumulation followed by Smad3 mRNA and protein down-regulation occur exclusively at the wound. Mechanistically, three transcriptional coactivators whose localization is regulated by cell contact integrity are critical for these local effects. These are myocardin-related transcription factor (MRTF), the driver of the SMA promoter; β-catenin, which counteracts the known inhibitor...

We previously reported in vitro maintenance and proliferation of human small intestinal epithelium using Matrigel, a proprietary basement membrane product. There are concerns over the applicability of Matrigel-based methods for future human therapies. We investigated type I collagen as an alternative for the culture of human intestinal epithelial cells. Human small intestine was procured from fresh surgical pathology specimens. Small intestinal crypts were isolated using EDTA chelation. Intestinal subepithelial myofibroblasts were isolated from a pediatric sample and expanded in vitro. After suspension in Matrigel or type I collagen gel, crypts were co-cultured above a confluent layer of myofibroblasts. Crypts were also grown in monoculture with exposure to myofibroblast conditioned media; these were subsequently sub-cultured in vitro and expanded with a 1∶2 split ratio. Cultures were assessed with light microscopy, RT-PCR, histology, and immunohistochemistry. Collagen supported via...