Insulin-like Growth Factor-1 Growth Factor Research Articles

Hematoma Resolution In Vivo Is Directed by Activating Transcription Factor 1.

The efficient resolution of tissue hemorrhage is an important homeostatic function. In human macrophages in vitro, heme activates an AMPK (AMP-activated protein kinase)/ATF1 (activating transcription factor-1) pathway that directs Mhem macrophages through coregulation of HO-1 (heme oxygenase-1; HMOX1) and lipid homeostasis genes. We asked whether this pathway had an in vivo role in mice. Perifemoral hematomas were used as a model of hematoma resolution. In mouse bone marrow-derived macrophages, heme induced HO-1, lipid regulatory genes including LXR (lipid X receptor), the growth factor IGF1 (insulin-like growth factor-1), and the splenic red pulp macrophage gene Spic. This response was lost in bone marrow-derived macrophages from mice deficient in AMPK (Prkab1-/-) or ATF1 (Atf1-/-). In vivo, femoral hematomas resolved completely between days 8 and 9 in littermate control mice (n=12), but were still present at day 9 in mice deficient in either AMPK (Prkab1-/-) or ATF1 (Atf1-/-; n=6 each). Residual hematomas were accompanied by increased macrophage infiltration, inflammatory activation and oxidative stress. We also found that fluorescent lipids and a fluorescent iron-analog were trafficked to lipid-laden and iron-laden macrophages respectively. Moreover erythrocyte iron and lipid abnormally colocalized in the same macrophages in Atf1-/- mice. Therefore, iron-lipid separation was Atf1-dependent. Taken together, these data demonstrate that both AMPK and ATF1 are required for normal hematoma resolution. Graphic Abstract: An online graphic abstract is available for this article.

Exposure to a Glyphosate-based Herbicide Alters the Expression of Key Regulators of Mammary Gland Development on Pre-pubertal Male Rats

We previously reported that exposure during gestation and lactation to a low dose of glyphosate-based herbicide (GBH) reduced the area and perimeter of male offspring mammary gland at postnatal day 60 (PND60), whereas a higher dose increased the longitudinal growth of the gland. Here, our aim was to assess whether perinatal exposure to GBH exhibits endocrine disruptive action in male mammary gland at an early time point (pre-puberty), which could be related to the changes observed after puberty. We also wanted to explore whether an early evaluation of the male rat mammary gland is appropriate to assess exposure to potential endocrine disrupting chemicals (EDCs). Pregnant rats were orally exposed, through the diet, to vehicle (saline solution), 3.5 or 350 mg/kg/day of GBH from gestational day 9 until weaning. At PND21, the male offspring were euthanized, and mammary gland samples were collected. The histology and proliferation index of the mammary glands were evaluated, and the mRNA expression of estrogen (ESR1) and androgen (AR) receptors, cyclin D1 (Ccnd1), amphiregulin (Areg), insulin-like growth factor 1 (IGF1), epidermal growth factor receptor (EGFR) and IGF1 receptor (IGF1R) were assessed. Moreover, the phosphorylated-Erk1/2 (p-ERK1/2) protein expression was determined. No differences were observed in mammary epithelial structures and AR expression between experimental groups; however, the proliferation index was reduced in GBH3.5-exposed males. This result was associated with decreased ESR1, Ccnd1, Areg, IGF1, EGFR and IGF1R mRNA expressions, as well as reduced p-Erk1/2 protein expression in these animals. ESR1, Ccnd1, IGF1R and EGFR expressions were also reduced in GBH350-exposed males. In conclusion, the mammary gland development of pre-pubertal male rats is affected by perinatal exposure to GBH. Although further studies are still needed to understand the molecular mechanisms involved in GBH350 exposure, the present results may explain the alterations observed in mammary gland growth of post-pubertal males exposed to low doses of GBH. Our results also suggest that early evaluation of the male rat mammary gland is useful in assessing exposure to potential EDCs. However, analysis of EDCs effects at later time points should not be excluded.

Effect of sex class on the levels of some biochemical variables in thalassemia patients

The study was conducted at Azadi Teaching Hospital - Thalassemia Center for the period from 1/10/2017 to 1/4/2018. It included 60 patients including 30 males and 30 females, as well as control group which included 20 Healthy people were all 10 to 21 years of age. The following variables were studied: ferritin, GSH, insulin-like growth factor-1 (IGF-1) Malondialdehyde (MDA) Interleukin-6 (IL-6), and Cortisol. The analysis of correlation coefficients and simple linear regression was carried out to determine the effect of the variables among them. The results were as follows: Thalassemia patients recorded the lowest levels of GSH, IGF-1 and cortisol at 2.2 μmol / L and 50.4 ng / ml and 10.11 μg / dL respectively, while the same group recorded the highest levels of ferritin, MDA and IL- 6 was 3083 ng / ml, 941 mmol / L and 368 pg / mol. There were significant effects of both sexes in the group of thalassemia patients in both ferritin, GSH, IGF-1, MDA, and IL-6 with 2573, 3592 μg / dL, 2.821, 1.573 μmol / L, 63.3, 37.47 ng / ml and 1163.1 719.3 mmol / L 300.9 and 435.6 pg / mol for males and females, respectively. The results of the correlation coefficient analysis showed existence of and low correlations in the negative and positive direction between the study variables of the two groups of patients and control. The results of the simple linear regression analysis showed positive and negative regression ratios of IL-6 and IGF-1 growth factor on the rest of the study variables.

Assessment of Serum Levels of Growth Factors IGF1 and IGFBP3 in Children with Cystic Fibrosis

Background: Cystic fibrosis (CF) is a multi-systemic disorder with an autosomal recessive inheritance. It is characterized by recurrent pulmonary infections and gastrointestinal problems, particularly pancreas insufficiency. Objectives: The aim of this study was to evaluate growth peptides in CF patients. Methods: This cross sectional study was approved by Mashhad University of Medical Sciences ethical committee. Patients were between six months to 18 years old, who were referred to Dr. Sheikh Hospital subspecialty clinic. They were enrolled for the study after obtaining a written constant. Demographic data was recorded. Of all cases, 10-cc blood sample was obtained and growth peptide levels were determined and measured. Data were analyzed by SPSS version 16 and Mann Whitney and χ2 tests were used. Results: Patients’ mean age at onset was 3.4 ± 1.1 months. Overall, 36 (60%) children were male and 24 (40%) were female. Mean body mass index (BMI) was 15.9 ± 3.2 kg/m2. Mean levels of growth hormone was 1.9 ± 0.37 (ng/mL), insulin-like growth factor 1 (IGF1) was 85.8 ± 9.6 microg/L and insulin-like growth factor binding protein 3 (IGFBP3) level was 18538 ± 10643 pg/mL. Conclusions: The mean serum levels of GH, IGF1, and IGFBP3 in CF children with growth failure was lower than children without growth failure. Regarding the relatively high prevalence of growth disorders in children with cystic fibrosis, selected, appropriate, and standard medical treatments could improve the outcome for these children.

The Interaction of Protein-tyrosine Phosphatase α (PTPα) and RACK1 Protein Enables Insulin-like Growth Factor 1 (IGF-1)-stimulated Abl-dependent and -independent Tyrosine Phosphorylation of PTPα

Protein tyrosine phosphatase α (PTPα) promotes integrin-stimulated cell migration in part through the role of Src-phosphorylated PTPα-Tyr(P)-789 in recruiting and localizing p130Cas to focal adhesions. The growth factor IGF-1 also stimulates PTPα-Tyr-789 phosphorylation to positively regulate cell movement. This is in contrast to integrin-induced PTPα phosphorylation, that induced by IGF-1 can occur in cells lacking Src family kinases (SFKs), indicating that an unknown kinase distinct from SFKs can target PTPα. We show that this IGF-1-stimulated tyrosine kinase is Abl. We found that PTPα binds to the scaffold protein RACK1 and that RACK1 coordinates the IGF-1 receptor, PTPα, and Abl in a complex to enable IGF-1-stimulated and Abl-dependent PTPα-Tyr-789 phosphorylation. In cells expressing SFKs, IGF-1-stimulated phosphorylation of PTPα is mediated by RACK1 but is Abl-independent. Furthermore, expressing the SFKs Src and Fyn in SFK-deficient cells switches IGF-1-induced PTPα phosphorylation to occur in an Abl-independent manner, suggesting that SFK activity dominantly regulates IGF-1/IGF-1 receptor signaling to PTPα. RACK1 is a molecular scaffold that integrates growth factor and integrin signaling, and our identification of PTPα as a RACK1 binding protein suggests that RACK1 may coordinate PTPα-Tyr-789 phosphorylation in these signaling networks to promote cell migration.

Identification and characterization of a mirror-image oligonucleotide that binds and neutralizes sphingosine 1-phosphate, a central mediator of angiogenesis.

The sphingolipid S1P (sphingosine 1-phosphate) is known to be involved in a number of pathophysiological conditions such as cancer, autoimmune diseases and fibrosis. It acts extracellularly through a set of five G-protein-coupled receptors, but its intracellular actions are also well documented. Employing in vitro selection techniques, we identified an L-aptamer (Spiegelmer®) to S1P designated NOX-S93. The binding affinity of NOX-S93 to S1P had a Kd value of 4.3 nM. The Spiegelmer® shows equal binding to dihydro-S1P, but no cross-reactivity to the related lipids sphingosine, lysophosphatidic acid, ceramide, ceramide-1-phosphate or sphingosine phosphocholine. In stably transfected CHO (Chinese-hamster ovary) cell lines expressing the S1P receptors S1PR1 or S1PR3, NOX-S93 inhibits S1P-mediated β-arrestin recruitment and intracellular calcium release respectively, with IC50 values in the low nanomolar range. The pro-angiogenic activity of S1P, and of the growth factors VEGF-A (vascular endothelial growth factor-A), FGF-2 (fibroblast growth factor-2) and IGF-1 (insulin-like growth factor-1), was effectively blocked by NOX-S93 in a cellular angiogenesis assay employing primary human endothelial cells. These data provide further evidence for the relevance of extracellular S1P as a central mediator of angiogenesis, suggesting pharmacological S1P neutralization as a promising treatment alternative to current anti-angiogenesis approaches.

Effects of perioperative hypothermia on healing of anastomosis of the colon in rats

We evaluated the hypothesis that induced perioperative hypothermia in rats causes adverse effects on the healing of colonic anastomosis. Forty-eight Wistar rats were divided into eight groups of six animals that underwent laparotomy, sigmoid section, and anastomosis. Four groups were operated under normothermic conditions (36 ± 1 °C) and four under hypothermic conditions (32 ± 1 °C). The reoperations were performed on days 3, 7, and 14 post-surgery, and two groups where SHAM reoperated on day 3. We evaluated anastomotic bursting pressure and tissue hydroxyproline content; performed a histological analysis of inflammatory parameters and healing (inflammatory cell infiltrate, edema, fibrin, collagen deposition and apoptotic cells) with categorization scores = 0, 1, 2, 3; and examined the relative quantification gene expression (cDNA) of inflammatory cytokines [interleukin 1 (IL-1), interleukin 6 (IL-6), and interleukin 10 (IL-10)] and growth factors [vascular endothelial growth factor and insulin-like growth factor 1 (IGF-1)] by reverse transcription polymerase chain reaction. Both of the hypothermic groups showed lower anastomotic burst pressure on days 7 and 14 post-surgery, reduced hydroxyproline content on day 14, reduction of inflammatory infiltrates and edema at day 3, and less collagen deposition on day 14. In animals that were hypothermic, the cytokine gene expression showed reduced IL-1 on day 3, reduced IL-6 on days 7 and 14, and reduced IL-10 on days 7 and 14 and a reduction in the growth factor IGF-1 on day 7. Perioperative hypothermia had detrimental effects on the healing of colonic anastomosis in rats.

Insulin-like growth factor 1 and 2 (IGF1, IGF2) expression in human microglia: differential regulation by inflammatory mediators

BackgroundRecent studies in experimental animals show that insulin-like growth factor 1 (IGF1) plays a trophic role during development and tissue injury and that microglia are important sources of IGF1. However, little information is available regarding the expression, regulation, and function of IGF1 and related proteins in human brain cells. In the current study, we examined the expression of IGF1 and IGF2 in human microglia in vivo and in vitro.MethodsExpression of IGF1 and IGF2 was examined by immunohistochemistry in post-mortem human brain sections derived from HIV+ and HIV− brains. In primary cultures of human fetal microglia, IGF1 and IGF2 mRNA and protein expression was examined by Q-PCR, ELISA, and Western blot analysis. Additionally, the role of IGF1 and IGF2 in neuroprotection was examined in primary human neuronal glial cultures.ResultsImmunohistochemistry of human brain tissues showed that nonparenchymal cells (vessels and meninges), as well as parenchymal microglia and macrophages were positive for IGF1, in both HIV encephalitis and control brains, while IGF2 was undetectable. Cultured microglia expressed IGF1 mRNA and produced pg/ml levels of IGF1 protein; this was significantly suppressed by proinflammatory mediators, such as lipopolysaccharide (LPS), poly(I:C), and IFNγ. The Th2 cytokines IL-4 and IL-13 had no significant effect, but the cAMP analog (dibutyryl cAMP) significantly increased IGF1 production. In contrast, microglial IGF2 mRNA and protein (determined by Western blot) were upregulated by LPS. IGF1 receptor (IGF1R) immunoreactivity was predominantly expressed by neurons, and both IGF1 and IGF2 significantly protected neurons from cytokine (IL-1/IFNγ) induced death.ConclusionsOur study in human brain tissues and cells indicates that microglia are important sources of neurotrophic growth factors IGF1 and IGF2, and that microglial activation phenotypes can influence the growth factor expression. Importantly, our results suggest that chronic neuroinflammation and upregulation of proinflammatory cytokines could lead to neurodegeneration by suppressing the production of microglia-derived neuronal growth factors, such as IGF1.

Sodium-coupled vitamin C transporter (SVCT2): expression, function, and regulation in intervertebral disc cells

Background contextVitamin C (ascorbic acid [AA]) is essential for the synthesis of collagen and also acts as an antioxidant in the intervertebral disc (IVD). However, there is very little information currently available on the identity of the transporter that facilitates AA entry into IVD cells and the factors that mediate the transport process. PurposeTo investigate the expression of the two known isoforms of Na+-coupled vitamin C transporter, SVCT1 and SVCT2, in IVD cells and its regulation by insulin-like growth factor 1 (IGF-1) and the steroid hormone dexamethasone. Study designTo identify the expression and functional activity of the sodium-dependent vitamin C transporter (SVCT) in the IVD. MethodsUptake studies were carried out with rabbit annulus fibrosis and nucleus pulposus cells in 24-well plates using [14C]-AA. To characterize SVCT transporter, uptake was done in the presence and absence of Na+ in the uptake buffer. Time dependency, Na+ activation kinetics, saturation kinetics, and substrate selectivity studies were performed. Regulatory studies were performed in the presence of IGF-1 and the steroid hormone dexamethasone. Gene expression was analyzed by quantitative polymerase chain reaction. ResultsOur real-time polymerase chain reaction results showed the presence of SVCT2 but not SVCT1 in IVD cells. Uptake of vitamin C in IVD cells is Na+ dependent and saturable. The Michaelis constant for the process is 96±11 μM. The activation of vitamin C uptake by Na+ exhibits a sigmoidal relationship, indicating involvement of more than one Na+ in the activation process. The uptake system does not recognize any other water-soluble vitamin as a substrate. Immunocytochemical analysis shows robust expression of SVCT2 protein in IVD cells. The growth factors IGF-1 and the steroid hormone dexamethasone upregulate the expression of SVCT2 in IVD cells. ConclusionsOur studies demonstrate that the active SVCT2 is expressed in IVD cells and that the expression of this transporter is regulated by growth factors IGF-1 and dexamethasone.

Effects of low-level laser therapy on ROS homeostasis and expression of IGF-1 and TGF-β1 in skeletal muscle during the repair process

The aim of the present study was to determine the effects of low-level laser therapy (LLLT) on the homeostasis of reactive oxygen species (ROS) and expression of IGF-1 and TGF-β1 in the gastrocnemius muscles of rats following contusion. Muscle regeneration involves cell proliferation, migration, and differentiation and is regulated by growth factors. A growing body of evidence suggests that LLLT promotes skeletal muscle regeneration and accelerates tissue repair. Adult male Sprague-Dawley rats (n=96) were randomly divided into three groups: control group (no lesion, untreated, n=6), contusion group (n=48), and contusion-plus-LLLT group (n=42). Gallium aluminum arsenide (GaAlAs) laser irradiation (635 nm; beam spot, 0.4 cm(2); output power, 7 mW; power density, 17.5 mW/cm(2); 20 min) was administered to the gastrocnemius contusion for 20 min daily for 10 days. Muscle remodeling was evaluated at 0 h and 1, 2, 3, 7, 14, 21, and 28 days after injury. Hematoxylin and eosin and Van Gieson staining were used to evaluate regeneration and fibrosis; muscle superoxide dismutase (SOD) and malondialdehyde (MDA) were detected via biochemical methods; expression of transforming growth factor beta-1 (TGF-β1) and insulin-like growth factor-1 (IGF-1) were investigated via immunohistochemistry. The results showed that LLLT markedly promoted the regeneration of muscle and reduced scar formation. LLLT also significantly enhanced muscle SOD activity and significantly decreased muscle MDA levels 1, 2, and 3 days after injury. LLLT increased the expression of IGF-1 2, 3, and 7 days after injury and decreased the expression of IGF-1 21 and 28 days after injury. LLLT decreased the expression of TGF-β1 3 and 28 days after injury but increased expression at 7 and 14 days after injury. Our study showed that LLLT could modulate the homeostasis of ROS and of the growth factors IGF-1 and TGF-β1, which are known to play important roles in the repair process. This may constitute a new preventive approach to muscular fibrosis.

Ischemia-Reperfusion Injury and Pregnancy Initiate Time-Dependent and Robust Signs of Up-Regulation of Cardiac Progenitor Cells

To explore how cardiac regeneration and cell turnover adapts to disease, different forms of stress were studied for their effects on the cardiac progenitor cell markers c-Kit and Isl1, the early cardiomyocyte marker Nkx2.5, and mast cells. Adult female rats were examined during pregnancy, after myocardial infarction and ischemia-reperfusion injury with/out insulin like growth factor-1(IGF-1) and hepatocyte growth factor (HGF). Different cardiac sub-domains were analyzed at one and two weeks post-intervention, both at the mRNA and protein levels. While pregnancy and myocardial infarction up-regulated Nkx2.5 and c-Kit (adjusted for mast cell activation), ischemia-reperfusion injury induced the strongest up-regulation which occurred globally throughout the entire heart and not just around the site of injury. This response seems to be partly mediated by increased endogenous production of IGF-1 and HGF. Contrary to c-Kit, Isl1 was not up-regulated by pregnancy or myocardial infarction while ischemia-reperfusion injury induced not a global but a focal up-regulation in the outflow tract and also in the peri-ischemic region, correlating with the up-regulation of endogenous IGF-1. The addition of IGF-1 and HGF did boost the endogenous expression of IGF and HGF correlating to focal up-regulation of Isl1. c-Kit expression was not further influenced by the exogenous growth factors. This indicates that there is a spatial mismatch between on one hand c-Kit and Nkx2.5 expression and on the other hand Isl1 expression. In conclusion, ischemia-reperfusion injury was the strongest stimulus with both global and focal cardiomyocyte progenitor cell marker up-regulations, correlating to the endogenous up-regulation of the growth factors IGF-1 and HGF. Also pregnancy induced a general up-regulation of c-Kit and early Nkx2.5+ cardiomyocytes throughout the heart. Utilization of these pathways could provide new strategies for the treatment of cardiac disease.

Long Range Interactions Regulate Igf2 Gene Transcription during Skeletal Muscle Differentiation

The differentiation, maintenance, and repair of skeletal muscle is controlled by interactions between genetically determined transcriptional programs regulated by myogenic transcription factors and environmental cues activated by growth factors and hormones. Signaling through the insulin-like growth factor 1 (IGF1) receptor by locally produced IGF2 defines one such pathway that is critical for normal muscle growth and for regeneration after injury. IGF2 gene and protein expression are induced as early events in muscle differentiation, but the responsible molecular mechanisms are unknown. Here we characterize a distal DNA element within the imprinted mouse Igf2-H19 locus with properties of a muscle transcriptional enhancer. We find that this region undergoes a transition to open chromatin during differentiation, whereas adjacent chromatin remains closed, and that it interacts in differentiating muscle nuclei but not in mesenchymal precursor cells with the Igf2 gene found more than 100 kb away, suggesting that chromatin looping or sliding to bring the enhancer in proximity to Igf2 promoters is also an early event in muscle differentiation. Because this element directly stimulates the transcriptional activity of an Igf2 promoter-reporter gene in differentiating myoblasts, our results indicate that we have identified a bona fide distal transcriptional enhancer that supports Igf2 gene activation in skeletal muscle cells. Because this DNA element is conserved in the human IGF2-H19 locus, our results further suggest that its muscle enhancer function also is conserved among different mammalian species.

Transcripts of PTTG and Growth Factors bFGF and IGF-1 are Correlated in Pituitary Adenomas

The reasons for the increase of pituitary tumor-transforming gene (PTTG) transcripts in about 90% of pituitary adenomas are still not fully understood, although upregulation by basic fibroblast growth factor (bFGF) has been discussed as a potential cause. A possible influence of the Insulin like Growth Factor 1 (IGF-1) might be of interest, since this protein is also synthesized in most pituitary adenomas. Moreover, the principal regulation of the PTTG gene by IGF-1 and Insulin has been demonstrated in astrocytoma and breast cancer cells. We analyzed a large group (103 patients) of unselected clinical pituitary adenoma samples. From total RNA of frozen tumor samples (all subtypes) cDNA ( COMPLEMENTARY DNA) was synthesized and transcripts of PTTG, bFGF, IGF-1 were measured by Real-Time-PCR. Not only mRNA ( MESSENGER RNA) levels of bFGF, but also of IGF-1, correlated strongly with PTTG transcripts. This result was obtained, when all pituitary adenoma samples were included in the statistical calculations, irrespective of their subclassification. Our study suggests a connection between PTTG and IGF-1 in pituitary adenomas.

Epigallocatechin‐3‐Gallate suppresses early stage, but not late stage prostate cancer in TRAMP mice: Mechanisms of action

Prostate cancer (PCa) is the second leading cause of cancer-related death in men in the United States. Many men have implemented purported chemopreventive agents into their daily diet in an attempt to delay the early onset of a PCa. Green tea polyphenols, one such agent, has been shown to be chemopreventive in skin, breast, and prostate cancers. We hypothesized that Epigallocatechin-3-Gallate (EGCG), the major polyphenol found in green tea, will exert its chemopreventive effect in the prostate via regulation of sex steroid receptor, growth factor-signaling, and inflammatory pathways. Five-week-old male TRAMP (Transgenic Adenocarcinoma Mouse Prostate) offspring were fed AIN-76A diet and 0.06% EGCG in tap water. Animals were sacrificed at 28 weeks of age and the entire prostates were scored histopathologically. In addition, animals were sacrificed at 12 weeks of age and ventral (VP) and dorsolateral (DLP) prostates were removed for histopathological evaluation and immunoblot analyses or ELISA. EGCG, inhibited early but not late stage PCa in the current study. In the VP, EGCG significantly reduced cell proliferation, induced apoptosis, and decreased androgen receptor (AR), insulin-like growth factor-1 (IGF-1), IGF-1 receptor (IGF-1R), phospho-extracellular signal-regulated kinases 1 and 2 (phospho-ERKs 1 and 2), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). The attenuation of the AR, the down-regulation of potent growth factor IGF-1, modulation of inflammation biomarkers, and decrease in the MAPK signaling may contribute to the reduction in cell proliferation and induction of apoptosis and hence provide a biochemical basis for EGCG suppressing PCa without toxicity.

Effect of Growth Factors on Bovine Retinal Pigment Epithelial Cell Migration and Proliferation

Background: To examine the effects of platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), acidic fibroblast growth factor (aFGF), insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF), and transforming growth factor beta 2 (TGF_β2) on bovine retinal pigment epithelial (RPE) cell migration and proliferation. Materials and Methods: Cultured bovine RPE cells were treated with 10 ng/ml PDGF, bFGF, aFGF, IGF-1, EGF, or TGF_β2. RPE cell migration studies were performed in multiwell plates confluently covered with RPE cells. After inhibition of proliferation and denudation of half of each well, cells were incubated with various growth factors. Migration was measured as the number of cells that had entered the denuded area after 20 h. RPE cell proliferation was determined by [³H]thymidine incorporation after growth factor stimulation for 24 h. Results: RPE cell migration was significantly enhanced after incubation with PDGF (stimulation of 213% compared to the negative control, p = 0.002), bFGF (206%, p = 0.003), aFGF (175%, p = 0.003), IGF-1 (150%, p = 0.003), and EGF (144%, p = 0.003). RPE cell proliferation was stimulated by bFGF (322% compared to the negative control, p < 0.005), PDGF (119%, p < 0.005), aFGF (121%, p < 0.005), and EGF (94%, p < 0.005). IGF-1 showed no significant effect on RPE cell proliferation; TGF_β2 displayed no effect on RPE cell migration nor on proliferation. Conclusions: The peptide growth factors PDGF, bFGF, aFGF, IGF-1, and EGF play an important role in initiating RPE cell migration. Basic FGF, PDGF, aFGF, and EGF stimulate RPE cell DNA synthesis.

Effect of Twice Daily Administration of GH-releasing Peptide-2 for 10 Days on Growth Performance, Plasma GH Responses and Insulin-like Growth Factor-1 Concentrations in Swine

An increase in frequency of administration of exogenous growth hormone (GH) or GH-releasing hormone was reported to be a model to increase blood circulating insulin-like growth factor-1 (IGF-1) and to improve growth performance in animals. We have investigated the effect of twice daily administration of GH-releasing peptide-2 (GHRP-2) on growth performance, GH responsiveness and plasma insulin-like growth factor IGF-1 in swine. We administered to eight swine, 3 control and 5 treatment, a twice daily s.c. injections of GHRP-2 (30 µg/kg BW) for a period of 10 days. Every day blood samples immediately taken before injections of GHRP-2 or saline, at 08:00 h and 16:00 h, were measured for IGF-1 concentrations. Blood samples for GH assay were collected every 20 min on days 1, 6 and 10, from 1 hour before and 3 h after GHRP-2 or saline injections at 08:00 h. GH peak concentrations and GH area under curve (GH AUC) on day 1, 6 and 10 in treatment group of swine were higher than those in control swine (p<0.05). Twice daily administration of GHRP-2 caused a significantly attenuation (p<0.05) of GH peak concentrations (80.25±13.87, 39.73±5.72 and 27.57±6.06 ng/ml for day 1, 6 and 10, respectively) and GH AUCs (3,536.15±738.35, 1,310.31±203.55 and 934.37±208.99 ng/ml for day 1, 6 and 10, respectively). However, there was no significant difference in GH peak concentration and GH AUC between day 6 and 10. Plasma IGF-1 concentration levels were higher in treatment than control group of swine (p<0.05) after 3 days of the treatment, and the levels reached a plateau from day 3 to 10 of experiment. Growth performance did not alter by GHRP-2 administration, even though a numerical increase of body weight gain and feed efficiency was observed. These results indicate that twice daily administration of GHRP-2 for 10 days in swine did not significantly influence on growth performance, caused an overall attenuation of GH response, and that elevation of plasma GH concentrations caused by GHRP-2 administration increased plasma IGF-1 concentrations, even though an attenuation of GH response was observed. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 8 : 1193-1198)

Local application of growth factors (insulin-like growth factor-1 and transforming growth factor-β1) from a biodegradable poly( d,l-lactide) coating of osteosynthetic implants accelerates fracture healing in rats

In vitro and in vivo studies have demonstrated an osteoinductive effect of growth factors such as insulin-like growth factor-1 (IGF-1) and transforming growth factor-β1 (TGF-β1). However, for therapeutic use in fracture treatment, questions remain with regard to the local application of these proteins. A controlled, local release of growth factors from a biodegradable polylactide coating of osteosynthetic implants may have a stimulating effect on fracture healing. Such implants could stabilize the fracture and their bioactive surface could function simultaneously as a local drug-delivery system. Previous studies have demonstrated the high mechanical stability of an approximately 10–14-μm-thick poly( d,l-lactide) (PDLLA) coating on metallic implants, which can even withstand the process of intramedullary insertion. Following an initial peak, 80% of incorporated growth factors IGF-1 and TGF-β1 were continuously released within 42 days. The effect of locally applied IGF-1 and TGF-β1 from a biodegradable PDLLA coating of intramedullary implants on fracture healing was investigated in a rat model. Midshaft fractures of the right tibia of 5-month-old female Sprague-Dawley rats (n = 127) were stabilized with coated vs. uncoated titanium Kirschner wires. X-ray examinations and blood analyses were performed, and body weight and body temperature measurements were taken throughout the experimental period. After 28 and 42 days, respectively, tibiae were dissected for mechanical torsional testing and histomorphometrical analyses. X-rays demonstrated an almost completely consolidated fracture, biomechanical testing showed a significantly higher maximum load and torsional stiffness, and histological and histomorphometric analyses demonstrated progressed remodeling after 28 and 42 days in the group treated with growth factors as compared with controls. Interestingly, the PDLLA coating itself revealed a positive effect on fracture healing even without incorporated growth factors. No systemic changes of serum parameters, including IGF-1 and IGF binding proteins, and no differences in body weight and body temperature were observed within and between groups. These findings suggest that the local application of growth factors from a biodegradable PDLLA coating of osteosynthetic implants accelerates fracture healing significantly without systemic side effects.

Insulin-like growth factor-1 suppresses pyrophosphate elaboration by transforming growth factor β1-stimulated chondrocytes and cartilage

Our objective was to examine the effect of insulin-like growth factor-1 (IGF-1) on extracellular pyrophosphate (ePPi) elaboration by porcine cartilage. These studies further define the factors influencing ePPi accrual, a key step in calcium pyrophosphate dihydrate (CPPD) crystal formation. ePPi was measured in adult porcine organ and monolayer culture media in the presence of IGF-1, transforming growth factor beta-1 (TGFbeta-1), IGF-1 antibody and synovial fluid (SF). As previously shown, TGFbeta-1 stimulated ePPi elaboration by cartilage and chondrocytes. IGF-1 significantly inhibited the stimulatory effect of TGFbeta-1 on ePPi elaboration by both cartilage explants and chondrocytes. Anti-IGF-1 antibody blocked this inhibition. Anti-IGF-1 antibody also decreased the inhibitory effect of SF on ePPi elaboration, suggesting the presence of active IGF-1. These results support an important regulatory role for IGF-1 in cartilage ePPi elaboration. IGF-1 inhibited the effects of the ePPi-stimulatory factor TGFbeta-1 and thus may protect normal joints from excess accumulation of ePPi and subsequent CPPD crystal formation.

Insulin-like growth factor 1 (IGF-1) in burn patients

Variations in growth factor IGF-1 levels during wound healing were assessed in 23 patients with bums of varying extent and severity. The patients were followed during the postburn period and the IGF-1 levels were regularly measured by radioimmunoassay. All patients with large burns had reduced IGF-1 levels which correlated with the surface area of burn. The most plausible reason for the suppressed IGF-1 level in these patients may be diffusion from the burned skin as we have found a strong correlation between IGF-1 and serum albumin. The reduced IGF-1 levels may contribute to impaired wound healing in these patients.

Local application of growth-factor IGF-1 to healing bone. Experiments with a titanium chamber in rabbits.

In order to study the effects of bone healing, insulin-like growth factor 1 (IGF-1) was continuously applied with a minipump to a healing bone callus located inside a titanium chamber in a rabbit tibia. After 2 weeks, 99mTc-MDP uptake and calcium content were measured. IGF-1 decreased 99mTc-MDP uptake, and thus the mineral turnover rate, but the amount of bone mineral was unchanged. Probably the normal endogenous production of IGF-1 is already optimal for healing in this model.