Platelet-derived growth factor and epidermal growth factor play a major role in human colonic fibroblast repair activities

Applications of decellularized materials in tissue engineering: advantages, drawbacks and current improvements, and future perspectives

Decellularized materials (DMs) are attracting more and more attention in tissue engineering because of their many unique advantages, and they could be further improved in some aspects through various means.

PDGF in organ fibrosis

Fibrosis is part of a tissue repair response to injury, defined as increased deposition of extracellular matrix. In some instances, fibrosis is beneficial; however, in the majority of diseases fibrosis is detrimental. Virtually all chronic progressive diseases are associated with fibrosis, representing a huge number of patients worldwide. Fibrosis occurs in all organs and tissues, becomes irreversible with time and further drives loss of tissue function. Various cells types initiate and perpetuate pathological fibrosis by paracrine activation of the principal cellular executors of fibrosis, i.e. stromal mesenchymal cells like fibroblasts, pericytes and myofibroblasts. Multiple pathways are involved in fibrosis, platelet-derived growth factor (PDGF)-signaling being one of the central mediators. Stromal mesenchymal cells express both PDGF receptors (PDGFR) α and β, activation of which drives proliferation, migration and production of extracellular matrix, i.e. the principal processes of fibrosis. Here, we review the role of PDGF signaling in organ fibrosis, with particular focus on the more recently described ligands PDGF-C and -D. We discuss the potential challenges, opportunities and open questions in using PDGF as a potential target for anti-fibrotic therapies.

A comparison of high throughput core–shell 2D electrospinning and 3D centrifugal spinning techniques to produce platelet lyophilisate-loaded fibrous scaffolds and their effects on skin cells

Nanofibres enriched with bioactive molecules, as actively acting scaffolds, play an important role in tissue engineering.

Thrombospondin-1 contributes to mortality in murine sepsis through effects on innate immunity

Background

Thrombospondin-1 (TSP-1) is involved in many biological processes, including immune and tissue injury response, but its role in sepsis is unknown. Cell surface expression of TSP-1 on platelets is increased in sepsis and could activate the anti-inflammatory cytokine transforming growth factor beta (TGFβ1) affecting outcome. Because of these observations we sought to determine the importance of TSP-1 in sepsis.

Methodology/Principal Findings

We performed studies on TSP-1 null and wild type (WT) C57BL/6J mice to determine the importance of TSP-1 in sepsis. We utilized the cecal ligation puncture (CLP) and intraperitoneal E.coli injection (IP E.coli) models of peritoneal sepsis. Additionally, bone-marrow-derived macrophages (BMMs) were used to determine phagocytic activity. TSP-1−/− animals experienced lower mortality than WT mice after CLP. Tissue and peritoneal lavage TGFβ1 levels were unchanged between animals of each genotype. In addition, there is no difference between the levels of major innate cytokines between the two groups of animals. PLF from WT mice contained a greater bacterial load than TSP-1−/− mice after CLP. The survival advantage for TSP-1−/− animals persisted when IP E.coli injections were performed. TSP-1−/− BMMs had increased phagocytic capacity compared to WT.

Conclusions

TSP-1 deficiency was protective in two murine models of peritoneal sepsis, independent of TGFβ1 activation. Our studies suggest TSP-1 expression is associated with decreased phagocytosis and possibly bacterial clearance, leading to increased peritoneal inflammation and mortality in WT mice. These data support the contention that TSP-1 should be more fully explored in the human condition.

Epidermal growth factor serum levels and the 61 G/A polymorphism in patients with acute pancreatitis

BACKGROUND

Epidermal growth factor (EGF) binds to pancreatic acinar cells and facilitates recovery from acute pancreatitis (AP). In animal models, EGF protects against pancreatic injury and prevents septic complications. The role of EGF in human AP is unknown.

AIMS

The aim of this study was to assess EGF serum levels in AP patients and whether the EGF +61 G/A single nucleotide polymorphism (SNP) affects susceptibility and/or severity of AP.

METHODS

Hospitalized AP patients were prospectively enrolled. Demographics, clinical features, DNA and early serum samples were collected when available. Patients were classified into mild (79%) and severe AP (21%) based on organ failure for >or=48 h. Early serum samples were quantitatively assayed for EGF levels. The EGF +61 G/A SNP was evaluated by restriction fragment length polymorphism analysis.

RESULTS

There were 179 patients ascertained with AP. EGF levels were measured in a subgroup of 60 patients with early serum samples (17 severe) and in serum from 58 healthy controls. Serum EGF levels within 48 h from the onset of pain were significantly lower in AP patients (mean 13.5 pg/ml) compared to controls (25.2 pg/ml; P=0.015). Furthermore, EGF levels were significantly lower in severe patients when compared to mild (7.8 vs. 14.3 pg/ml; P=0.026). DNA from all 179 patients and 189 healthy controls was sequenced. The EGF +61 G/A SNP did not affect susceptibility to or severity of AP.

CONCLUSIONS

EGF serum levels are decreased early in the course of AP and are further suppressed in severe AP. The EGF +61 G/A polymorphism has no effect on AP.

Does low molecular weight heparin impair anastomotic wound healing?

BACKGROUND

Enoxaparin is an important molecule which had been using in prophylaxis and treatment of deep venous thrombosis. Also, it is showed that it prevents postsurgical peritoneal adhesions in rats. It is aimed to evaluate its effects on gastrointestinal wound healing.

METHODS

Thirty Wistar albino rats were divided into three groups as control, subcutan, and intraperitoneal enoxaparin groups. Left colon anastomoses were performed. On postoperative seventh day, anastomotic healing was evaluated by measuring anastomotic bursting pressure, tissue hydroxyproline levels, and histopathological examination.

RESULTS

The anastomotic bursting pressure was highest in subcutan enoxaparin group (p < 0.001), intraperitoneal enoxaparin group (p < 0.01) came the second, and the control group has the worst value. The hydroxyproline results were found nearly similar to the bursting pressure values (subcutan (p < 0.001) > intraperitoneal (p < 0.05) > control). Neovascularization in subcutan group (p < 0.001) has a statistically significant difference to other groups.

CONCLUSION

Enoxaparin did not interfere with colonic anastomotic resistance but improved the intestinal wound healing.

Combination of fibrin glue with growth hormone augments healing of incomplete intestinal anastomoses in a rat model of intra-abdominal sepsis: a dynamic study

This study was devised to investigate whether fibrin glue (FG) in combination with growth hormone (GH) could have a beneficial effect at a late period (14 days) after injury. Male Wistar rats, with abdominal sepsis induced by an incomplete anastomosis, were divided into three groups. In the control group, the rats got incomplete anastomoses sutured alone; in the FG and FG/GH groups, anastomoses protection was performed with application of FG alone or in combination with GH. The anastomotic bursting pressure (ABP) was significantly higher in the FG/GH group than that of the FG group on postoperative day (POD) 5 (p < .01), while it could not be measured from POD 7 to POD 14 because of intestinal dehiscence. There was no difference between FG and FG/GH group on POD 3 and POD 5 in anastomotic tensile strength, which was significantly higher in the FG/GH group than that of the FG group from POD 7 to POD 14 (p < .001). Hydroxyproline content of the FG/GH group was significantly higher than that of the control from POD 3 and that of the FG group from POD 5 (p < .05). Combination of FG with GH had a synergistic effect to improve intestinal anastomotic healing over a limited 14-day course of observation.

Effects of enoxaparin on the healing of abdominal wall in rats: study on breaking strength and histopatology

PURPOSE: To evaluate the influence of enoxaparin on the abdominal wall healing. METHODS: Sixty Wistar male rats were randomly distributed into two experimental groups. Group E: consisted of 30 rats, submitted to abdominal suture and treated with enoxaparin in a dose of 1 mg/kg of body weight, subcutaneously administered from immediate postoperative until the 7th day; Group C: consisted of 30 rats submitted to abdominal suture and treated with the equivalent dose per volume of NaCl 0.9%. The animals were submitted to median laparotomy and were operated again at the 3rd, 7th or 14th postoperative day for the resection of the anterior abdominal wall. The tissue's stretching resistance was tested and a histopathological evaluation was performed. Through Mann-Whitney's U test, a statistical analysis was conducted considering significant values for p <0.05. RESULTS: The tensile breaking strength presented a median of 0.64N for group C and 0.41N for group E (p=0.60) at the 3rd postoperative day; of 2.27N for group C and of 4.32N for group E (p=0.01) at the 7th POD; of 5.72N for group C and of 6.62N for group E (p=0.97) at the 14th POD. In relation to the histopathological study, the results did not show significant statistical differences, except for the amount of collagen at the 7th POD, which medians were 2 on group C and 1 on group E (p=0.007). CONCLUSION: Considering the conditions in which this study was conducted, the administration of enoxaparin led to an strengthening of the tissue's breaking resistance at the 7th POD; on the histopathological exam, a significant difference was observed at the 7th POD, with a better collagen disposition on group C.

Pax-6 expression in posthatch chick retina during and recovery from form-deprivation myopia

The expression of Pax-6 in fully-differentiated chick retina remains largely confined to the amacrine and ganglion cell layers. In the developing posthatch chick retina, Pax-6 expression shows a biphasic pattern; a decrease by posthatch day 17 followed by a steady increase in the adult eye. Interestingly, we find that this biphasic expression of Pax-6 is reflected in the biphasic growth pattern of the posthatch chick eye, which is disrupted by form-deprivation myopia (FDM). We have now examined the pattern of Pax-6 accumulation in 3-day-old chick eyes subjected to 2 weeks of FDM followed by 2 weeks of recovery from FDM. Quantitative RT-PCR (with a homologous internal control) revealed that after 2 weeks of occlusion the contralateral non occluded eyes, the occluded eyes and the normal nonexperimental chick eyes did not show any drastic changes in the number of Pax-6 transcripts. The data obtained suggests that the contralateral eye does not represent a 'normal' control eye; similar but nonidentical changes are seen, at the molecular level, in both the contralateral and the occluded eyes. Comparisons with the control nonexperimental animals, however, are meaningful. Even after 2 weeks of recovery under normal light conditions, the occluded eyes do not seem to reach the same level of Pax-6 expression (number of molecules per mg tissue) as seen in normal control eyes, suggesting that exposure of the posthatch chick eye to FDM impedes developmental progression that normally culminates in emmetropia.

Toll-like receptor signaling stimulates cell cycle entry and progression in fibroblasts

Toll-like receptors (TLRs) are proteins involved in recognition of foreign pathogen-associated molecular patterns and activation of processes leading to innate immune recognition. We show that stimulation of fibroblasts with a TLR5 ligand, flagellin, can induce proliferation of serum-starved cells or prevent cell cycle exit upon serum withdrawal independently of autologous growth factor secretion. Other TLR ligands, such as poly(I:C) and lipopolysaccharide, can have a similar effect only if the action of type I interferons is blocked. Flagellin stimulation can prevent cell cycle arrest induced by overexpression of exogenous cyclin-dependent kinase inhibitor p27. Stimulation of TLR5 and overexpression of MyD88, but not TRIF, TIRAP, or TRAM, result in p27 degradation, which can be suppressed by dominant negative Akt and mutation of the p27 C-terminal Thr(187) site. These data provide evidence for a nonimmune and cell autonomous role of TLR signaling, whereby TLR stimulation provides a positive signal for cell division.

Cytokine secretion from mononuclear cells culturedin vitro with starch-based polymers and poly-L-lactide

The cytokine network is one of the major controlling systems of the inflammatory process, driving the magnitude and duration of the host response against invading microorganisms, foreign materials, or altered internal stimuli. Pro- and antiinflammatory cytokines were quantified after in vitro culture of a mixed population of monocytes/macrophages and lymphocytes with biodegradable polymers. Different blends of starch-based polymers and their composites filled with hydroxyapatite were studied and compared with poly-L-lactide. Interleukin (IL)-1beta, IL-6, and tumour necrosis factor-alpha were investigated as the markers of immunological reactivity because they are known to act at the early stages of injury/invasion. Interferon-gamma, recognized as a proinflammatory cytokine, although not present during early responses was also investigated. Contrarily, IL-4 derived from T lymphocytes, was investigated because it is an immunoregulator that counteracts some aspects of inflammation. T lymphocyte activation was also determined by quantifying IL-2. The results support the hypothesis that different biodegradable polymers can affect mononuclear cell activation and the production of several cytokines associated with the inflammatory process. No IL-2 or interferon-gamma was found in the culture supernatants after 3, 7, and 14 days in the presence of any of the materials. IL-6 was detected in the highest amounts, for all the conditions, followed by tumour necrosis factor-alpha. IL-1beta was produced in very low amounts, being undetectable with some of the starch-based materials. IL-4 was the only cytokine that did not demonstrate any significant difference within this group of materials. Starch-based polymers and composites induced lower production of proinflammatory cytokines in comparison to poly-L-lactide.

[Effect of exogenous administration of platelet-derived growth factor and epidermal growth factor on duodenal ulcer healing in rats treated with indomethacin]

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) delay peptic ulcer healing through mechanisms that are still not entirely understood. Growth factors play a significant role in healing.

AIM

To evaluate whether exogenous administration of platelet-derived growth factor (PDGF) reverses the effect of indomethacin in experimental duodenal ulcers in rats and to define the potential mechanisms involved in this process.

METHOD

Duodenal ulcer was induced in male Wistar rats with acetic acid. The rats were then administered indomethacin (2 mg/kg/day), PDGF-BB (30 ng/100 g/day), epidermal growth factor (EGF) (50 /kg/day) or famotidine (positive control) or the possible combinations of these. Macroscopic area, reduction in microscopic diameter, epithelial and granulation tissue proliferation, collagen secretion by granulation tissue, and gastric acid secretion were analyzed.

RESULTS

Indomethacin delayed duodenal ulcer healing by decreasing cellular proliferation and inhibiting collagen secretion. PDGF and EGF accelerated healing and reversed the effects of indomethacin. The mechanisms involved were associated with an increase in collagen proliferation and secretion without affecting gastric acid secretion. Famotidine also accelerated healing and reversed the effect of indomethacin, and these effects were associated with a marked inhibition of gastric acid secretion and increase in collagen secretion by granulation tissue.

CONCLUSIONS

Exogenous administration of PDGF and EGF accelerated healing and reversed the harmful effects of indomethacin in an experimental model of duodenal ulcer.

Hepatocyte growth factor attenuates pancreatic damage in caerulein-induced pancreatitis in rats

Hepatocyte growth factor (HGF) overexpression was reported in experimental and clinical acute pancreatitis. These observations prompted us to determine the effect of HGF administration on the development of caerulein-induced pancreatitis in rats. Acute pancreatitis was induced by s.c. infusion of caerulein (10 microg/kg/h) for 5 h. HGF was administrated twice (30 min before caerulein or saline infusion and 3 h later) at the doses: 0.4, 2, 10 or 50 microg/kg s.c. Immediately after cessation of caerulein or saline infusion, the pancreatic blood flow, plasma amylase and lipase activity, plasma cytokines concentration, cell proliferation, and morphological signs of pancreatitis were examined. Caerulein administration induced acute edematous pancreatitis manifested by 41% decrease in DNA synthesis, 53% inhibition of pancreatic blood flow, a significant increase in plasma amylase and lipase activity, plasma interleukin-1beta and interleukin-6 concentration, as well as, the development of the histological signs of pancreatic damage (edema, leukocyte infiltration, and vacuolization). Administration of HGF without induction of pancreatitis increased plasma interleukin-10. Treatment with HGF, during induction of pancreatitis, increased plasma interleukin-10 and attenuated the pancreatic damage, what was manifested by histological improvement of pancreatic integrity, the partial reversion of the drop in DNA synthesis and pancreatic blood flow, and the reduction in pancreatitis evoked increase in plasma amylase, lipase, and interleukin-1beta and interleukin-6 levels. HGF administrated at the dose 2 microg/kg exhibited a similar beneficial effect as administration of HGF at the doses 10 or 50 microg/kg. Treatment with HGF at the dose 0.4 microg/kg was less effective. We conclude that: (1) administration of HGF attenuates pancreatic damage in caerulein-induced pancreatitis; (2) this effect seems to be related to the increase in production of interleukin-10, the reduction in release of interleukin-1beta and interleukin-6, and the improvement of pancreatic blood flow.

NFAT4 movement in native smooth muscle. A role for differential Ca(2+) signaling

The transcription factor NFAT (nuclear factor of activated T-cells) plays a central role in mediating Ca(2+)-dependent gene transcription in a variety of cell types. Sustained increases in intracellular calcium concentration ([Ca(2+)]i) are presumed to be required for NFAT dephosphorylation by the Ca(2+)/calmodulin-dependent protein calcineurin and its subsequent nuclear translocation. Here, we provide the first identification and characterization of NFAT in native smooth muscle, showing that NFAT4 is the predominant isoform detected by reverse transcriptase-polymerase chain reaction and Western blot analysis. PDGF induces NFAT4 translocation in smooth muscle, leading to an increase in NFAT transcriptional activity. NFAT4 activation by PDGF depends on Ca(2+) entry through voltage-dependent Ca(2+) channels, because its nuclear accumulation is prevented by the Ca(2+) channel blocker nisoldipine and the K(+) channel opener pinacidil. Interestingly, elevation of [Ca(2+)]i by membrane depolarization or ionomycin treatment are not effective stimuli for NFAT4 nuclear accumulation, indicating that Ca(2+) influx is necessary but not sufficient for NFAT4 activation. In contrast, membrane depolarization readily activates the Ca(2+)-dependent transcription factor CREB (cAMP-responsive element-binding protein). The calcineurin blockers CsA and FK506 also prevented the PDGF-induced NFAT4 nuclear localization. These results indicate that both the nature of the calcium signal and PDGF-induced modulation of nuclear import-export of NFAT are critical for NFAT4 activation in this tissue.