Chronic systemic treatment with epidermal growth factor induces smooth muscle cell hyperplasia and hypertrophy in the urinary tract of mature Goettingen minipigs

Epidermal growth factor in clinical practice - a review of its biological actions, clinical indications and safety implications

Chemotaxis, mitogenesis, motogenesis and cytoprotection are common cellular events involved in both tumourigenesis and tissue repair, which appear amplified upon growth factors exposure. Epidermal growth factor (EGF) promotes these events in epithelial and mesenchymal cells through the binding to a specific tyrosine kinase receptor. In experimental oncology settings, EGF does not initiate malignant transformation but exhibits 'tumour promotion'. These observations have raised doubts on the clinical use of EGF despite solid demonstrations of efficacy in experimental conditions and clinical trials. The results of a Pubmed and Bioline investigation on EGF clinical uses and preclinical safety data are presented here. EGF topical administration has been used since 1989 to enhance the healing process of a variety of peripheral tissues wounds (16 clinical reports), as well as its intravenous, oral and rectal administration for gastrointestinal damages (11 clinical reports). EGF therapeutic efficacy and excellent tolerability seem demonstrated. Lack of long-term adverse effects is highlighted in those studies with 6, 12 and 24 months of patients follow-up. Although post-treatment follow-up may fall short for malignant growth, there are no reports on evidences linking EGF clinical use with cancer. A multicentre, nationwide survey in Cuba, 15 years after randomly using silver sulphadiazine with EGF or not in burn victims yielded that cancer incidence was comparable between EGF-treated and control subjects and that such incidence rate does not differ from the age-matched national incidence for those 15-year period. All the animal species subjected to long-term EGF systemic administration exhibit dose-dependent and reversible epithelial organs hyperplasia with no changes in cells phenotypic differentiation. Histotypic pre-malignant markers were not identified. The results emerged from co-carcinogenesis studies and from transgenic mice over-expressing EGF are conflicting and indicate that EGF overexposure, either innate or postnatal, may not be sufficient to transform cells. The ability of EGF to heal injured tissues in life-threatening scenarios or to assist in preventing physical and social disability advocates for its clinical use under a rational medical risk/benefit balance.

Alterações morfométricas da musculatura dos músculos longitudinal e circular de ratos submetidos à criação de piloros no intestino delgado

OBJETIVO: Realizar um estudo morfométrico comparativo da musculatura longitudinal e circular do intestino delgado de ratos submetidos à construção cirúrgica de um e de dois piloros no intestino delgado utilizando-se da técnica de criação de piloros proposta por Rena et al. MÉTODO: Foram utilizados 52 ratos Wistar machos divididos em três grupos. O Grupo A, destacado como controle, composto de 10 animas, cada um forneceu 20mm de segmento de intestino para o estudo. Os animais do Grupo B, composto de 32 animais, foram submetidos à construção de dois piloros, um a 100mm e outro a 150mm da válvula ileocecal e os animais do grupo C, composto de 10 animais, foram submetidos à construção de um piloro a 100mm da mesma. A eutanásia ocorreu no décimo dia. A morfometria das camadas musculares longitudinal e circular acima e abaixo dos piloros foi estudada com utilização do microscópico modelo "Axiostar plus" conectado à câmera "Axioncam Version 5.05.10" com objetiva X5 / 0,12 no o programa "AxioVision 3.1.2.1". RESULTADOS: As alças apresentaram aumento da espessura da camada muscular acima e abaixo do ponto da operação. O estudo morfométrico comparativo das camadas musculares longitudinal e circular mostrou aumento significativo em comparação ao controle, não demonstrando significância entre os grupos B e C. CONCLUSÃO: Os resultados deste estudo revelaram importante aumento de espessura das camadas musculares, porém, menos acentuados que aqueles descritos na literatura quando foram realizados em animais submetidos à estenose fixa. Esses dados indicam que a construção operatória de piloros pela técnica utilizada promove alterações musculares de menor monta, possivelmente, pela função valvular do piloro.

Comprehensive evaluation of ureteral healing after electrosurgical endopyelotomy in a porcine model: original report and review of the literature

PURPOSE

Endopyelotomy (EP) has yet to equal the success achieved with open dismembered pyeloplasty. To understand better the ureteral response to EP we performed a timed histopathological evaluation of the porcine ureter after Acucise (Applied Medical, Rancho Santa Margarita, California) EP.

MATERIALS AND METHODS

In 28 domestic pigs bilateral Acucise EPs were performed and bilateral 7Fr stents were placed. The kidneys, ureters and bladder were harvested after EP at 0, 1, 2, 3, 6, 12 and 18 hours, 1, 3 and 5 days, and 1, 2, 4 and 8 weeks. The stents were removed after 4 weeks. The healing area of the ureter was sectioned. Half was fixed in formalin 10%, stained and evaluated by light microscopy. The other half was frozen and reverse transcriptase-polymerase chain reaction was performed to measure steady state levels of epidermal growth factor, transforming growth factor (TGF)-alpha, TGF-beta 1, TGF-beta 2, TGF-beta 3, keratinocyte growth factor, vascular endothelial growth factor, insulin-like growth factor, platelet derived growth factor, collagen type 1, integrin and fibronectin transcript expression. Immunohistochemistry for actin, desmin and myosin expression was completed. The same studies were applied to the mid portion of the unoperated ureter.

RESULTS

Initial sealing of the ureterotomy defect was by blood clot and periureteral fat. Complete healing of the mucosa was observed at 2 weeks in animals without an associated urinoma. However, in no case did the muscle layer bridge the whole circumference of the ureter despite followup out to 8 weeks. In the operated ureter elevated expression of keratinocyte growth factor, vascular endothelial growth factor, TGF-alpha, TGF-beta 1, TGF-beta 3 and integrin was detected 2 hours after the operation and sustained for 7 to 14 days after the procedure. Immunohistochemistry revealed that most presumed myocytes seen in the defect were actually myofibroblasts. Persistent urinoma formation beyond the first few days appeared to slow the healing process.

CONCLUSIONS

Urothelium regenerated rapidly over an iatrogenic ureteral defect despite the absence of a lamina propria. Muscle cell coverage failed to occur completely at 8 weeks. In the initial 8 weeks of the healing process myofibroblasts appear to be prevalent. A persistent urinoma negatively impacts the healing process.

The expression of epidermal growth factor and transforming growth factor-beta1 in the stenotic tissue of congenital pelvi-ureteric junction obstruction in children

PURPOSE

The aim of this study was to test the hypothesis that expression of epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGF-beta 1) may be altered in stenotic tissue of patients with congenital hydronephrosis caused by pelviureteric junction (PUJ) obstruction and to evaluate the role of these 2 growth factors.

METHODS

The expression of EGF and TGF-beta 1 was evaluated in tissue specimens in 25 children with PUJ obstruction and 15 controls with normal PUJs by immunohistochemistry, in situ hybridization, and reverse transcriptase polymerase chain reaction (RT-PCR) techniques. All the signals of mRNA products were normalized to the mRNA levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) a housekeeping gene, as a ratio.

RESULTS

On RT-PCR study, the amount of TGF-beta 1 mRNA in stenotic tissue was higher than in controls, in addition, EGF gene expression in the obstructed junction was significantly lower than in normal junctions. The TGF-beta 1 to GAPDH ratio was 0.57 +/- 0.26 and 0.36 +/- 0.19 in the stenotic tissue and the normal ureter, respectively (P =.012). The EGF to GAPDH ratio was 0.17 +/- 0.08 and 0.37 +/- 0.14 in the stenotic tissue and the normal ureter, respectively (P =.0001). Furthermore, the positive correlations were found between TGF-beta1 gene and protein expression (r = 0.601; P =.001), TGF-beta 1 gene and drainage clearance half-time (T1/2) (r = 0.474; P =.017), TGF-beta 1 protein expression, and T1/2 (r = 0.516; P =.008). A negative correlation was found between EGF gene and T1/2 (r = -0.448; P =.025). On immunolabeling and in situ hybridization labeling, the expression of TGF-beta 1 protein was strongly positive and confined to the muscle cells, spindle cells, and collagen fibers in the stenotic tissue; the expression of TGF-beta 1 mRNA was moderately positive and mainly distributed in the collagen of the stenotic segment, both the expression of EGF protein and mRNA were negative in the normal ureter.

CONCLUSIONS

There were increased TGF-beta 1 mRNA expression and decreased EGF mRNA expression in the stenotic tissue after clinical ureteropelvic junction obstruction. The alteration of EGF and TGF-beta 1 expression may be involved in the pathogenesis of congenital hydronephrosis.

Use of epidermal growth factor and collagen synthesis inhibition as adjuvant to healing of ureteroureteral anastomosis

BACKGROUND AND PURPOSE

When treating a ureteral narrowing by endopyelotomy or endoureterotomy, the urologist hopes that after the narrowed area is cut, it will heal with a patent lumen. A ureteral stent is usually left in place to provide a framework for healing. In cases of failure, histologic examination shows a predominance of collagen. We evaluated the effects of epidermal growth factor (EGF) and a collagen synthesis inhibitor, halofuginone, as adjuncts to ureteral healing.

MATERIALS AND METHODS

Ten female pigs underwent ureteroureteral anastomosis bilaterally, with the left side being stented. They were then randomized to receive EGF (N = 4), halofunginone (N = 3), or saline (control; N = 3). On postoperative day 30, the ureters were examined grossly and histologically.

RESULTS

The lumens of the ureters were significantly larger in the animals that received either EGF or funginone than in the control animals. The epithelium was significantly thicker in the animals that received halofunginone than in the controls or animals receiving EGF. The thickness of the smooth muscle and adventitia was similar in the three groups. Stenting improved the results.

CONCLUSION

Both EGF and halofuginone show promise as adjuncts to endopyelotomy and endoureterotomy.

Increased local synthesis of epidermal growth factors in infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is characterized by hypertrophy of the pyloric muscle. The growth of smooth muscle cells is regulated by several growth factors. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor are potent mitogens for smooth muscle cells. In the present study, we investigated immunohistochemical localization of EGF and EGF-related peptides and EGF mRNA expression in pyloric smooth muscle cells to determine whether the EGF family is involved in the process of pyloric muscle hypertrophy in IHPS. Pyloric muscle biopsy specimens were obtained at the time of pyloromyotomy from 10 patients with IHPS. Control material included 10 pyloric muscle specimens taken at autopsy from age-matched cases without evidence of gastrointestinal disease. Indirect immunohistochemistry was performed using the avidin-biotin-peroxidase complex method with anti-EGF, anti-EGF receptor, and anti-heparin-binding EGF-like growth factor antibody. In situ hybridization was performed using digoxigenin-labeled EGF-specific oligonucleotide probe. The pattern of immunoreactivity in pyloric muscle with EGF, EGF receptor, and heparin-binding EGF-like growth factor was similar in all specimens. There was a marked increase in EGF, EGF receptor, and heparin-binding EGF-like growth factor immunoreactivity and EGF mRNA expression in smooth muscle cells in pyloric circular and longitudinal muscle from patients with IHPS compared with control specimens. These data suggest that the upregulated local synthesis of EGF and EGF-related peptides in pyloric muscle may play a critical role in the development of pyloric muscle hypertrophy in IHPS.

Differentiation of coronary smooth muscle cells to a cell cycle-arrested hypertrophic growth status by a synthetic non-toxic heparin-mimicking compound

Studies on the mode of action of basic fibroblast growth factor (bFGF) identified an essential role of heparan sulfate and heparin-like molecules in the formation of distinct bFGF-heparan sulfate-bFGF-receptor complexes that are required for bFGF-induced signal transduction. In coronary smooth muscle cells that express 6-8 ng bFGF mg(-1) cell protein, the heparan sulfate chains of membrane-associated proteoheparan sulfate are implicated in bFGF signaling and thus are involved in the regulation of proliferation and differentiation of vascular smooth muscle cells. We studied the mode of action of a synthetic non-sulfated heparin-mimicking compound termed RG-13,577 (poly-4-hydroxyphenoxy acetic acid, Mr approximately 5 kD) and found a dose-dependent antiproliferative effect that was characterized by a block of G(1)/S-phase transition indicated by a marked (80%) reduction of [3H]thymidine incorporation at a concentration of 5 microg ml(-1) RG-13,577. Cell cycle analysis showed a block of cell division in the G(1)-phase. In response to RG-13,577 the cells were converted into a hypertrophic growth status within 72 h as judged from a doubling of the cellular protein content and measurement of cell and nucleus size. The increased cell protein content resulted from a de novo synthesis and was also associated with an increase in the incorporation of [35S]sulfate into cell-associated proteoglycans, including the proteoheparan sulfate coreceptor of bFGF. In contrast, the compound-induced G(1)-phase arrest was associated with an extensive downregulation of the cellular and pericellular bFGF level. The reduced bFGF content was accompanied by downregulation of the bFGF signaling-involved protein kinase C-alpha and MAP kinase, abrogation of MAP kinase phosphorylation and overexpression of protein kinase C-gamma. RG-13,577 failed to elicit apoptotic reactions at a concentration range of 0.5-10 microg ml(-1) and its effect was reversible upon removal of the compound. It appears that RG-13,577 induces a phenotype transformation of coronary SMC into a metabolically active hypertrophic status that could promote repair processes after balloon angioplasty (PTCA) without stimulating cell proliferation. Development of non-toxic polyanionic compounds may provide an effective strategy to inhibit cell proliferation associated with restenosis following balloon angioplasty and coronary artery bypass surgery.