MGF (Mechano Growth Factor) Research & Studies

Mechano-growth factor (MGF), which is a growth factor produced specifically in response to mechanical stimuli, with potential of tissue repair and regeneration. Our previous research has shown that MGF plays a crucial role in repair of damaged periodontal ligaments by promoting differentiation of periodontal ligament stem cells (PDLSCs). However, the molecular mechanism is not fully understood. This study aimed to investigated the regulatory effect of MGF on differentiation of PDLSCs and its molecular mechanism.

Mechano growth factor (MGF), an isoform of insulin-like growth factor 1 (IGF-1), is recognized as a typical mechanically sensitive growth factor and has been shown to play an indispensable role in the skeletal system. In the joint cavity, MGF is highly expressed in chondrocytes, especially in the damaged cartilage tissue caused by trauma or degenerative diseases such as osteoarthritis (OA). Cartilage is an extremely important component of joints because it functions as a shock absorber and load distributer at the weight-bearing interfaces in the joint cavity, but it can hardly be repaired once injured due to its lack of blood vessels, lymphatic vessels, and nerves. MGF has been proven to play an important role in chondrocyte behaviors, including cell proliferation, migration, differentiation, inflammatory reactions and apoptosis, in and around the injury site. Moreover, under the normalized mechanical microenvironment in the joint cavity, MGF can sense and respond to mechanical stimuli, regulate chondrocyte activity, and maintain the homeostasis of cartilage tissue. Recent reports continue to explain its effects on various cell types and sport-related tissues, but its role in cartilage development, homeostasis and disease occurrence is still controversial, and its internal biological mechanism is still elusive. In this review, we summarize recent discoveries on the role of MGF in chondrocytes and cartilage defects, including tissue repair at the macroscopic level and chondrocyte activities at the microcosmic level, and discuss the current state of research and potential gaps in knowledge.

To evaluate the effects of mechano growth factor E peptide (MGF) on the invasive properties of melanoma cells.

Epiphyseal growth plate is highly dynamic tissue which is controlled by a variety of endocrine, paracrine hormones, and by complex local signaling loops and mechanical loading. Mechano growth factor (MGF), the splice variant of the IGF-I gene, has been discovered to play important roles in tissue growth and repair. However, the effect of MGF on the growth plate remains unclear. In the present study, we found that MGF mRNA expression of growth plate chondrocytes was upregulated in response to mechanical stimuli. Treatment of MGF had no effect on growth plate chondrocytes proliferation and differentiation. But it could inhibit growth plate chondrocytes apoptosis and inflammation under mechanical overload. Moreover, both wound healing and transwell assay indicated that MGF could significantly enhance growth plate chondrocytes migration which was accompanied with YAP activation and nucleus translocation. Knockdown of YAP with YAP siRNA suppressed migration induced by MGF, indicating the essential role of YAP in MGF promoting growth plate chondrocytes migration. Furthermore, MGF promoted YAP activation through RhoA GTPase mediated cytoskeleton reorganization, RhoA inhibition using C3 toxin abrogated MGF induced YAP activation. Importantly, we found that MGF promoted focal adhesion(FA) formation and knockdown of YAP with YAP siRNA partially suppressed the activation of FA kinase, implying that YAP is associated with FA formation. In conclusion, MGF is an autocrine growth factor which is regulated by mechanical stimuli. MGF could not only protect growth plate chondrocytes against damage by mechanical overload, but also promote migration through activation of RhoA/YAP signaling axis. Most importantly, our findings indicate that MGF promote cell migration through YAP mediated FA formation to determine the FA-cytoskeleton remodeling.

To determine the possible beneficial effects of a synthetic mechano-growth factor E peptide (MGF-C25E) on the healing of rat Achilles tendon.

This study investigated whether mechano growth factor-E (MGF-E) peptide can regulate apoptosis and inflammation responses in fibroblast-like synoviocytes of osteoarthritis (OA).

Osteosarcoma is one of the most common bone tumors, and exhibits a high degree of malignancy. Gene therapy is a novel approach to its treatment, however, specific target genes are required to enable effective use of this therapy. In order to investigate the effects of the mechano-growth factor E (MGF-E) peptide, which is derived from the IGF-I alternative splicing isoform, on the regulation of the development of osteosarcoma, the expression of MGF was detected in osteosarcoma cell lines with different degrees of malignancy. Concomitantly, exogenous MGF-E peptide was used to stimulate these osteosarcoma cell lines. The results demonstrated that MGF was overexpressed in malignant osteosarcoma cells, while it was not expressed in the least malignant osteosarcoma cells. Furthermore, MGF-E treatment altered the cell cycle distribution, and promoted the proliferation, migration and invasion of osteosarcoma cells. The possible mechanisms underlying these effects were detected by quantitative polymerase chain reaction and western blotting. Based on these results, it was hypothesized that MGF may be a suitable biomarker for malignant osteosarcoma phenotypes.

Damaged cartilage has poor self-healing ability and usually progresses to scar or fibrocartilaginous tissue, and finally degenerates to osteoarthritis (OA). Here we demonstrated that one of alternative isoforms of IGF-1, mechano growth factor (MGF) acted synergistically with transforming growth factor β3 (TGF-β3) embedded in silk fibroin scaffolds to induce chemotactic homing and chondrogenic differentiation of mesenchymal stem cells (MSCs). Combination of MGF and TGF-β3 significantly increased cell recruitment up to 1.8 times and 2 times higher than TGF-β3 did in vitro and in vivo. Moreover, MGF increased Collagen II and aggrecan secretion of TGF-β3 induced hMSCs chondrogenesis, but decreased Collagen I in vitro. Silk fibroin (SF) scaffolds have been widely used for tissue engineering, and we showed that methanol treated pured SF scaffolds were porous, similar to compressive module of native cartilage, slow degradation rate and excellent drug released curves. At 7 days after subcutaneous implantation, TGF-β3 and MGF functionalized silk fibroin scaffolds (STM) recruited more CD29+/CD44+cells (P<0.05). Similarly, more cartilage-like extracellular matrix and less fibrillar collagen were detected in STM scaffolds than that in TGF-β3 modified scaffolds (ST) at 2 months after subcutaneous implantation. When implanted into articular joints in a rabbit osteochondral defect model, STM scaffolds showed the best integration into host tissues, similar architecture and collagen organization to native hyaline cartilage, as evidenced by immunostaining of aggrecan, collagen II and collagen I, as well as Safranin O and Masson's trichrome staining, and histological evalution based on the modified O'Driscoll histological scoring system (P<0.05), indicating that MGF and TGF-β3 might be a better candidate for cartilage regeneration. This study demonstrated that TGF-β3 and MGF functionalized silk fibroin scaffolds enhanced endogenous stem cell recruitment and facilitated in situ articular cartilage regeneration, thus providing a novel strategy for cartilage repair.

The Insulin like growth factor-I isoform mechano-growth factor (MGF), is expressed in the heart following myocardial infarction and encodes a unique E-domain region. To examine E-domain function, we delivered a synthetic peptide corresponding to the unique E-domain region of the human MGF (IGF-1Ec) via peptide eluting polymeric microstructures to the heart. The microstructures were made of poly (ethylene glycol) dimethacrylate hydrogel and bioengineered to be the same size as an adult cardiac myocyte (100 × 15 × 15 μm) and with a stiffness of 20 kPa. Peptide eluting microrods and empty microrods were delivered via intramuscular injection following coronary artery ligation in mice. To examine the physiologic consequences, we assessed the impact of peptide delivery on cardiac function and cardiovascular hemodynamics using pressure-volume loops and gene expression by quantitative RT-PCR. A significant decline in both systolic and diastolic function accompanied by pathologic hypertrophy occurred by 2 weeks which decompensated further by 10 weeks post-infarct in the untreated groups. Delivery of the E-domain peptide eluting microrods decreased mortality, ameliorated the decline in hemodynamics, and delayed decompensation. This was associated with the inhibition of pathologic hypertrophy despite increasing vascular impedance. Delivery of the empty microrods had limited effects on hemodynamics and while pathologic hypertrophy persisted there was a decrease in ventricular stiffness. Our data show that cardiac restricted administration of the MGF E-domain peptide using polymeric microstructures may be used to prevent adverse remodeling of the heart and improve function following myocardial infarction.

Mesenchymal stem cells (MSCs) can differentiate into chondroblasts, adipocytes, or osteoblasts under appropriate stimulation. Mechano-growth factor (MGF) reportedly displays a neuroprotective effect in cerebral regions that were exposed to ischemia and is expressed in stromal cells of the eutopic endometrium and in glandular cells of the ectopic endometrium.

Tendon injuries are common in sports and are frequent reasons for orthopedic consultations. The management of damaged tendons is one of the most challenging problems in orthopedics. Mechano-growth factor (MGF), a recently discovered growth repair factor, plays positive roles in tissue repair through the improvement of cell proliferation and migration and the protection of cells against injury-induced apoptosis. However, it remains unclear whether MGF has the potential to accelerate tendon repair. We used a scratch wound assay in this study to demonstrate that MGF-C25E (a synthetic mechano-growth factor E peptide) promotes the migration of rat tenocytes and that this promotion is accompanied by an elevation in the expression of the following signaling molecules: focal adhesion kinase (FAK) and extracellular signal regulated kinase1/2 (ERK1/2). Inhibitors of the FAK and ERK1/2 pathways inhibited the MGF-C25E-induced tenocyte migration, indicating that MGF-C25E promotes tenocyte migration through the FAK-ERK1/2 signaling pathway. The analysis of the mechanical properties showed that the Young's modulus of tenocytes was decreased through treatment of MGF-C25E, and an obvious formation of pseudopodia and F-actin was observed in MGF-C25E-treated tenocytes. The inhibition of the FAK or ERK1/2 signals restored the decrease in Young's modulus and inhibited the formation of pseudopodia and F-actin. Overall, our study demonstrated that MGF-C25E promotes rat tenocyte migration by lessening cell stiffness and increasing pseudopodia formation via the FAK-ERK1/2 signaling pathway.

A splice form of IGF-1, IGF-1Eb, is upregulated after exercise or injury. Physiological responses have been ascribed to the 24-amino acid COOH-terminal peptide that is cleaved from the NH3-terminal 70-amino acid mature IGF-1 protein. This COOH-terminal peptide was termed "mechano-growth factor" (MGF). Activities claimed for the MGF peptide included enhancing muscle satellite cell proliferation and delaying myoblast fusion. As such, MGF could represent a promising strategy to improve muscle regeneration. Thus, at our two pharmaceutical companies, we attempted to reproduce the claimed effect of MGF peptides on human and mouse muscle myoblast proliferation and differentiation in vitro. Concentrations of peptide up to 500 ng/ml failed to increase the proliferation of C2C12 cells or primary human skeletal muscle myoblasts. In contrast, all cell types exhibited a proliferative response to mature IGF-1 or full-length IGF-1Eb. MGF also failed to inhibit the differentiation of myoblasts into myotubes. To address whether the response to MGF was lost in these tissue culture lines, we measured proliferation and differentiation of primary mouse skeletal muscle stem cells exposed to MGF. This, too, failed to demonstrate a significant effect. Finally, we tested whether MGF could alter a separate documented in vitro effect of the peptide, activation of p-ERK, but not p-Akt, in cardiac myocytes. Although a robust response to IGF-1 was observed, there were no demonstrated activating responses from the native or a stabilized MGF peptide. These results call in to question whether there is a physiological role for MGF.

Mechano-growth factor (MGF), a splice variant of insulin-like growth factor I (IGF-I), was discovered by Goldspink and colleagues in 1996; since then many studies have implicated MGF as an important local tissue repair factor. Although the short 24-amino-acid C-terminal peptide of MGF (MGF-Ct24E) has a variety of biological activities, its role in bone formation has not yet been clarified. Accordingly, the aim of this study was to investigate the role of MGF-Ct24E in the proliferation, differentiation, and mineralization of rat calvarial osteoblasts. Interestingly, although MGF-Ct24E significantly increased the proliferation and retarded the differentiation of osteoblasts during the first 3 days, prolonged treatment with MGF-Ct24E for up to 3 weeks promoted cell differentiation. To determine the molecular mechanisms behind this plurality, we carried out global transcriptional profiling of osteoblasts in response to MGF-Ct24E and identified differentially expressed genes by bioinformatics analysis. Gene ontology analysis indicated that MGF-Ct24E enhanced the expression of genes associated with osteoblast proliferation and the cell cycle and downregulated genes involved with osteoblast differentiation, skeletal system, and bone development. Moreover, KEGG pathway-based analysis indicated that MGF-Ct24E directly altered focal adhesion and cell cycle progression, in addition to regulating the actin cytoskeleton and gap junctions. In conclusion, MGF-Ct24E has a marked ability to increase bone formation by increasing cell proliferation and delaying cell differentiation during prophase, as well as by stimulating osteoblast differentiation during the advanced stage. The mechanism of action of MGF-Ct24E during the initial stages of bone formation in vitro involves upregulation of the expression of genes involved in proliferation and cell cycle progression, and the repression of differentiation-related genes.

Mechano growth factor (MGF) and its C-terminal E-peptide with 24 amino acids, MGF-Ct24E, have superiority in resolving the delayed or failed bone repair derived from shortness of suitable biomechanical stimulation. The chitosan/tripolyphosphate microspheres encapsulated with MGF-Ct24E (CS/TPP/MGF-Ct24E) are prepared using emulsion-ionic cross-linking method in order to achieve the sustained release and preserve the bioactivity of MGF-Ct24E. The microspheres are micron-sized and spherical in shape with smooth surface morphology. The TPP component disintegrates in advance of CS matrix and the MGF-Ct24E maintains sustained delivery during in vitro hydrolytic degradation. With the disappearance of TPP, the total weight loss of CS/TPP/MGF-Ct24E is 32% and the release amount of MGF-Ct24E reaches 84.6% after degrading for 2 weeks. In vitro bioactivity assays reveal that the MGF-Ct24E can accelerate MC3T3-E1 cells proliferation and delay their differentiation as well. The encapsulated MGF-Ct24E shows long-term effects after being loaded in the CS/TPP microspheres and the cells exhibit excellent morphology on the surface of microspheres. The continuous delivery of MGF-Ct24E provides a new perspective on resolving the unsatisfactory bone reconstruction associated with microgravity and stress shielding.

IGF1Ec in humans or IGF1Eb in rodents (known as mechano growth factor (MGF)) has a unique E domain, and the C-terminal end of the E domain (MGF E peptide) plays important roles in proliferation, migration and differentiation of many cell types. Bone marrow mesenchymal stem cells (BMSCs) have multiple differentiation potentials and are considered as perfect seed cells for tissue repair. But the role of MGF E peptide on BMSCs is seldom investigated and the mechanism is still unclear. In this study, we investigated the effects of MGF E peptide on rat BMSCs (rBMSCs). Our results revealed that treatment with MGF E peptide had no effect on BMSC proliferation. However, both wound-healing and transwell assays indicated that MGF E peptide could significantly enhance rBMSCs migration ability. Further analysis indicated that MGF E peptide also reduced the expression levels of osteogenic genes, but increased the expression levels of adipogenic genes. Analysis of molecular mechanism showed that phosphorylation-Erk1/2 was activated by MGF E peptide and blockage of either Erk1/2 or IGF1 receptor could repress the migration effect of MGF E peptide. In conclusion, MGF E peptide is able to inhibit osteogenic differentiation but promote adipogenic differentiation. In addition, the migration effect of MGF E peptide on rBMSCs depends on IGF1 receptor via Erk1/2 signal pathway.

To assess the potential efficacy of mechano growth factor (MGF) for bone injury, we firstly investigated the effects of growth factors, including MGF, its E peptide (a short 24-amino acid C-terminal peptide, MGF-Ct24E), and insulin-like growth factor 1(IGF-1) on MC3T3-E1 osteoblast-like cell proliferation. MGF-Ct24E had the highest pro-proliferation activity among three growth factors, which was 1.4 times greater than that of IGF-1. Moreover, MGF-Ct24E promoted cell proliferation by inducing cell cycle arrest in the S and G(2)/M phase of the cell cycle, but also mainly by the activation of the MAPK-Erk1/2 pathway. In vivo, a 5-mm segmental bone defect in the radius of 27 rabbits was treated with MGF-Ct24E by two doses (28.5 and 57 μg /kg body weight) vs. non-growth factor injection for five consecutive days postoperatively. The cumulative rate of radiographically healed defects and histological scores of bone defect-healing revealed a statistical difference between high-dose treatment and non treatment (p < 0.01), which showed the treatment promoted defect healing. This report is the first to demonstrate that MGF-Ct24E possesses positive effects on osteoblast proliferation and bone-defect healing, suggesting a new strategy in fracture healing.

Loss of muscle mass and strength is a major problem during aging and the expression of Mechano Growth Factor (MGF), a member of the IGF-1 (insulin-like Growth Factor 1) super family, has been shown to be both exercise and age dependent. MGF, also called IGF-1Ec, has a unique E domain with a 49bp insert in humans (52bp in rodents; IGF-1Eb), which results in a reading frame shift during the IGF-1 gene splicing to produce a distinct mature isoform. We have studied the effects of the MGF-24aa-E peptide on proliferation and differentiation of primary human muscle cell cultures isolated from healthy subjects of different ages. We found that MGF-E peptide significantly increases the proliferative life span and delays senescence of satellite cells isolated from neonatal and young adult but not from old adult muscle, hypertrophy associated with a significant decrease in the percentage of reserve cells was observed in all cultures. It is concluded that the MGF-24aa-E peptide alone has a marked ability to enhance satellite cell activation, proliferation and fusion for muscle repair and maintenance and could provide a new strategy to combat age related sarcopenia without the oncogenic side effects observed for IGF1.

The transcription of the insulinlike growth factor 1 (igf-1) gene generates three mRNA isoforms, namely IGF-1Ea, IGF-1Eb and IGF-1Ec (or MGF [mechano growth factor]). Herein, we analyzed the expression of IGF-1 isoforms in eutopic and ectopic endometrium (red lesions and endometriotic cysts) of women with endometriosis, and we characterized the actions of a synthetic MGF E-peptide on KLE cells. Our data documented that all three igf-1 gene transcripts are expressed in the stromal cells of the eutopic and ectopic endometrium; however, endometriotic cysts contained significantly lower IGF-1 isoform expression, both at the mRNA and protein level, as was shown using semiquantitative PCR and immunohistochemical methods. In addition, the glandular cells of the eutopic endometrium did not express any of the IGF-1 isoforms; however, the glandular cells of the ectopic endometrium (red lesions) did express the IGF-1Ec at mRNA and protein level. Furthermore, synthetic MGF E-peptide, which comprised the last 24 amino acids of the MGF, stimulated the growth of the KLE cells. Experimental silencing of the type 1 IGF receptor (IGF-1R) and insulin receptor expression of KLE cells (siRNA knock-out methods) did not alter the mitogenic action of the synthetic MGF E-peptide, revealing that MGF E-peptide stimulates the growth of KLE cells via an IGF-1R-independent and insulin receptor-independent mechanism. These data suggest that the IGF-1Ec transcript might generate, apart from mature IGF-1 peptide, another posttranslational bioactive product that may have an important role in endometriosis pathophysiology.

The discovery that IGF-I mRNAs encoding isoforms of the pro-IGF-I molecule are differentially regulated in response to mechanical stress in skeletal muscle has been the impetus for a number of studies designed to demonstrate that alternative splicing of IGF-I pre-mRNA involving exons 4, 5, and 6 gives rise to a unique peptide derived from pro-IGF-I that plays a novel role in myoblast proliferation. Research suggests that after injury to skeletal muscle, the IGF-IEb mRNA splice variant is up-regulated initially, followed by up-regulation of the IGF-IEa splice variant at later time points. Up-regulation of IGF-IEb mRNA correlates with markers of satellite cell and myoblast proliferation, whereas up-regulation of IGF-IEa mRNA is correlated with differentiation to mature myofibers. Due to the apparent role of IGF-IEb up-regulation in muscle remodeling, IGF-IEb mRNA was also named mechano-growth factor (MGF). A synthetically manufactured peptide (also termed MGF) corresponding to the 24 most C-terminal residues of IGF-IEb has been shown to promote cellular proliferation and survival. However, no analogous peptide product of the Igf1 gene has been identified in or isolated from cultured cells, their conditioned medium, or in vivo animal tissues or biological fluids. This review will discuss the relationship of the Igf1 gene to MGF and will differentiate actions of synthetic MGF from any known product of Igf1. Additionally, the role of MGF in satellite cell activation, aging, neuroprotection, and signaling will be discussed. A survey of outstanding questions relating to MGF will also be provided.