Biomedical subjects

G S Schultz

Publications and source records attributed to G S Schultz.

At least 55 records · Page 3Linked to original sources

PubMed1994

Elevation of transforming growth factor alpha in cat aqueous humor after corneal endothelial injury.

PURPOSE: To determine if a scrape injury to cat corneal endothelial cells increases the level of mitogenic proteins such as transforming growth factor alpha (TGF alpha) in aqueous humor. METHODS: Aqueous humor of cats was collected at 0, 2, 6, and 24 hours after wounding the endothelium by contact with a cannula tip. Aqueous humor samples collected from sham-wounded cats served as controls. Aqueous humor samples were analyzed for levels of protein, for mitogenic activity using incorporation of tritiated thymidine by cultures of bovine corneal endothelial cells, and for immunoreactive TGF alpha protein using a specific radioimmunoassay. RESULTS: The average protein level in aqueous humor obtained before wounding was low (0.5 mg/ml), increased 26-fold at 2 hours after injury (13 mg/ml), then progressively decreased at 6 hours (8 mg/ml) and 24 hours (2 mg/ml). Levels of mitogenic activity of aqueous humor samples collected 2, 6, and 24 hours after wounding were 2-fold, 2.5-fold, and 0.6-fold higher, respectively, compared to the level of mitogenic activity measured in aqueous humor collected before wounding (0 hours) or in aqueous humor collected from sham-wounded eyes. TGF alpha concentration in aqueous humor collected before endothelial wounding was low (6.8 ng/ml), increased 14-fold 2 hours after wounding (97.4 ng/ml), then progressively decreased at 6 hours (63.3 ng/ml) and 24 hours (35.5 ng/ml) after wounding. TGF alpha concentrations in aqueous humor collected from sham-wounded eyes at 2 hours (9.5 ng/ml) and 6 hours (5.3 ng/ml) were not significantly different from prewound levels. Detergent extracts of bovine corneal endothelial cells contained substantial levels of TGF alpha immunoreactive protein (20 ng/mg protein). CONCLUSIONS: Wounding of cat endothelium causes a rapid increase in mitogenic proteins in aqueous humor including TGF alpha, which may act by an autocrine mechanism to stimulate endothelial wound healing.

Animals↗

PubMed1993

Growth factors and wound healing: Part II. Role in normal and chronic wound healing.

Wound healing is a complex biologic process that involves the integration of inflammation, mitosis, angiogenesis, synthesis, and remodeling of the extracellular matrix. Part II of this two-part series reviews the results of experiments that indicate that growth factors and their receptors regulate key aspects of soft and hard tissue repair. Results of clinical studies are also reviewed that demonstrate that growth factor treatment accelerates healing of normal tissues and promotes healing of impaired wounds.

Animals↗

PubMed1993

Growth factors and wound healing: biochemical properties of growth factors and their receptors.

Wound healing is a complex biologic process that involves chemotaxis and division of cells, neovascularization, synthesis of extracellular matrix proteins, and remodeling of scar. Peptide growth factors have been shown to regulate many of these processes in vitro, leading to the hypothesis that peptide growth factors also regulate important phases of wound healing in vivo. Part I of this two-part series presents an overview of the biochemical properties of five families of peptide growth factors that are thought to be involved in wound healing: epidermal growth factor (EGF), transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), and fibroblast growth factor (FGF).

Animals↗

PubMed1993

Cellular distribution of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor in fascia and peritoneum during healing in the rat: an autoradiographic and immunohistochemical study.

The presence and cellular distribution of epidermal growth factor (EGF), TGF-alpha, and EGF-R were determined in the rat fascial and peritoneal tissue during healing of an incisional injury by means of immunohistochemistry and autoradiographic techniques. The immunostaining intensity for EGF in the regenerating wound area was substantially higher during the first 14 days, then decreased to near prewound levels during 14 to 35 days after surgery. Within the wound area, the most intense immunostaining occurred with inflammatory cells, followed by fascial striated muscle and arterioles, whereas fibroblasts in the regenerating area contained very low immunostaining intensity. The immunostaining pattern for TGF-alpha with the use of three separate polyclonal antibodies that were directed against the amino and carboxy termini of TGF-alpha precursor and a fragment of the mature 50-amino-acid form of TGF-alpha was similar to that seen with EGF and persisted until 28 days after injury. However, fibroblasts in the regenerating area immunostained intensely for TGF-alpha but not for EGF. Quantitative autoradiography of iodine 125-labeled EGF binding and immunohistochemical studies of the EGF-R with monoclonal antibodies that were directed against the extracellular binding domain of EGF-R demonstrated the presence of specific EGF-R in regenerating fascial and peritoneal tissue. Net grain density (100 microm(2)), representing specific binding of (125)I-EGF, was calculated for different cell types in the wound. The grain density over fascial striated muscle, migratory fibroblasts and peritoneal fibroblasts increased by two and one half, three, and four times, respectively, at 7 days and decreased to the values in adjacent unwounded tissue by 21 days after injury (p < 0.05). Immunostaining for the EGF-R generated similar patterns, which persisted for 14 days after injury. The grain density and immunostaining for EGF-R over the arterioles in the wound did not change during the course of healing and was similar to that of the uninjured regions. In summary, these observations indicate that the local levels of EGF, TGF-alpha, and EGF-R increase during the early phases of healing in fascial and peritoneal injury, which suggests a role for these growth factors in the normal mechanism of fascial/peritoneal wound healing and fibrous adhesion formation.

Journal Article↗

PubMed1993

Transforming growth factor-beta enhances connective tissue repair in perforated rat mesentery but not peritoneal macrophage chemotaxis.

The perforated rat mesentery model was used to study the effect of transforming growth factor-beta (TGF-beta) on connective tissue repair and influx of macrophages into the peritoneal cavity during such repair. Sprague-Dawley rats were laparotomized, and mesenteric wounds were made with a scalpel. A daily intraperitoneal injection of 0.5 microg TGF-beta was given for either 2 or 4 days. After 1 to 10 days, the animals received an intravenous injection of tritium-labeled thymidine before decapitation. Macrophages were collected by peritoneal washing, and the number of closed perforations was counted. Peritoneal cells were quantitated and a labeling index was determined by autoradiography. TGF-beta given for either 2 (p < 0.001) or 4 (p < 0.004) days accelerated closure of perforations on days 3 to 7 after injury. Laparotomy as such significantly increased leukocyte influx (p < 0.004), as well as macrophage-labeling index (p < 0.02). However, TGF-beta did not significantly influence either leukocyte influx or macrophage-labeling index. We concluded that TGF-beta significantly enhances connective tissue repair in this perforated rat mesentery model and that TGF-beta-induced stimulation of repair is not caused by an increased influx of macrophages into the peritoneal cavity.

Journal Article↗

PubMed1993

TGF-alpha protein and receptor localization in laryngotracheal tissue.

Both normal cell turnover and healing of laryngeal and tracheal injuries involve cell migration and mitosis. The proteins that regulate normal cell turnover and wound healing in the larynx and trachea have not been established. It is possible that peptide growth factors, such as transforming growth factor-alpha (TGF alpha) acting through its receptor (EGF/TGF alpha-R), participate in the regulation of these processes. To investigate this hypothesis, we analyzed laryngotracheal cells for TGF alpha protein and receptor in normal and postwounding conditions. TGF alpha protein was detected by immunohistochemical analysis in normal ferret laryngeal and tracheal mucosa. Specific binding to the EGF/TGF alpha receptor in membrane homogenates of ferret larynx and trachea reached saturation after 60 minutes at 37 degrees C, and was effectively displaced by unlabeled epidermal growth factor (EGF) or TGF alpha, but not by unlabeled insulin, angiotensin II, or basic fibroblast growth factor. Scatchard analysis of the specific binding indicated the presence of high-affinity (Kd = 117 pmol) and low-affinity (Kd = 40 nmol) binding sites. The maximum number of available binding sites was 73 fmol/mg protein. Localization of the EGF/TGF alpha receptor by autoradiographic analysis of 125I-EGF binding to sections of normal ferret larynx and trachea revealed EGF/TGF alpha receptors throughout the epithelium, with the highest grain density in the basal layers. Quantitative analysis of autoradiographic grain density between normal, intubated, and extubated animals revealed no significant differences. The presence of TGF alpha protein and its receptor in normal and wounded larynx and trachea supports the hypothesis that these proteins are involved in regulating physiologic responses of laryngotracheal cells.

Angiotensin II↗

PubMed1993

Detection of epidermal growth factor and transforming growth factor alpha protein in meningiomas and other tumors of the central nervous system in human beings.

Epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) are potent mitogens for normal cells of ectodermal and mesodermal origin. Evidence is accumulating that suggests that EGF, TGF alpha and their common receptor (EGF/TGF alpha-R) influence development and functioning of tissues of the central nervous system (CNS). To further investigate the possible roles of EGF, TGF alpha and their receptor in autocrine/paracrine regulation of tumor growth in the CNS, a series of tumors of the CNS were analyzed for the presence of specific, high affinity EGF/TGF alpha receptors and for the presence of immunoreactive TGF alpha protein. Binding of 125I-EGF to crude membranes from a pool of meningiomas was competed for equally well by low concentrations of unlabeled EGF or TGF alpha, but not by high concentrations of other protein hormones, demonstrating the high degree of specificity of the EGF/TGF alpha receptor. Specific binding of 125I-EGF was dependent upon time and temperature, with maximum specific binding achieved after two hours at 22 degrees C. Scatchard analysis of six tumors of the CNS large enough to permit titration analysis generated linear plots with an average kilodalton of 1.1 +/- 0.1 nanometer (+/- standard error of the mean), suggesting the presence of a single class of EGF/TGF alpha-R with high affinity. EGF also stimulated phosphorylation of a 170 kilodalton protein in membrane fraction of a meningioma, demonstrating that the EGF/TGF alpha-R in this tumor retained EGF-stimulated kinase autophosphorylating activity. Membranes for 17 additional smaller tumors of the CNS were analyzed for specific binding of 125I-EGF by single, high concentration method, and all 17 tumors were found to contain specific binding of 125I-EGF. The average level of 125I-EGF for all 23 tumors of the CNS was 46 +/- 27 femtomoles per milligram protein with a range of 1 femtomoles per milligram for both a pituitary adenoma and meningioma to 638 femtomoles per milligram for a glioblastoma. A series of 13 tumors of the CNS were analyzed for EGF alpha with use of a specific radioimmunoassay. TGF alpha immunoreactive protein was detected in all four malignant tumors of the CNS assayed at an average level of 2.6 +/- 1.1 nanograms per milligram soluble protein, whereas TGF alpha immunoreactive protein was detected in only two of nine benign tumors of the CNS. These results add support to the hypothesis that TGF alpha and its receptor may act by autocrine/paracrine mechanisms to influence growth of tumors of the CNS in vivo.

Central Nervous System Neoplasms↗

PubMed1993

Regulation of small intestinal glutamine transport by epidermal growth factor.

BACKGROUND: Epidermal growth factor (EGF) stimulates cell replication and increases DNA content of the small intestine, but its effects on mucosal amino acid transport are unknown. METHODS: To investigate these effects, we treated adult rats with vehicle or EGF (10 micrograms/100 gm body weight subcutaneously every 8 hours for three doses). Jejunal brush border membrane vesicles (BBMVs) from each group were prepared by Mg++ aggregation/differential centrifugation. BBMVs were enriched fifteen-fold in alkaline phosphatase, indicating BBMV purity. Transport of 3H-glutamine and 3H-alanine was studied by a rapid mixing filtration technique. Uptakes were primarily Na+ dependent, occurred in an osmotically active space, exhibited classic overshoots, and had similar 2-hour equilibrium values. RESULTS: Glutamine transport by BBMVs more than doubled in rats treated with EGF (16.4 +/- 0.1 pmol glutamine/mg protein/10 sec in EGF vs 7.1 +/- 0.5 pmol glutamine/mg protein/10 sec in controls; p < 0.001). Kinetic studies of the glutamine transporter showed that the increase in transport was the result of a 70% increase in maximal transport velocity (total maximum glutamine uptake = 193 +/- 8 pmol glutamine/mg protein/10 sec in EGF vs 114 +/- 7 pmol glutamine/mg protein/10 sec in controls; p < 0.0001 with no change in transporter affinity (transporter affinity = 224 +/- 6 mumol/L in EGF vs 242 +/- 37 mumol/L in controls; difference, not significant). Alanine uptake by BBMVs was also increased with EGF administration (10.2 +/- 2.0 pmol alanine/mg protein/10 sec in EGF vs 4.5 +/- 0.5 pmol alanine/mg protein/10 sec in controls; p < 0.005). Simultaneously, glucose transport was decreased by 50% in EGF-treated rats, indicating that the Na(+)-dependent glucose cotransporter is regulated independently from and opposite to amino acid transporters. CONCLUSIONS: We conclude that EGF up-regulates amino acid transport activity in jejunal BBMVs, an event that is most likely caused by an increase in de novo biosynthesis of transporter protein. The increase in amino acid uptake not only may support de novo protein synthesis but, in the case of glutamine, also may be required for energy production and nucleotide biosynthesis.

Alanine↗

PubMed1992

Intraoperative and post operative treatment with 5-fluorouracil and mitomycin-c: long term effects in vivo on subconjunctival and scleral fibroblasts.

Rabbits undergoing full thickness glaucoma filtering surgery were exposed to one of 4 treatments. Group 1 received intraoperative distilled water, group 2 received intraoperative mitomycin-c 0.2 mg/ml for 5 minutes, group 3 received 5 post operative injections of 5-Fluorouracil (5-FU) 5 mg in 0.1 ml, and group 4 received intraoperative 5-FU 50 mg/ml followed by 5 post operative injections of 5-FU. 30 days after the operation tissue biopsies were taken from the subconjunctival and scleral tissue at the treated area and 90 and 180 degrees from the treated area. The biopsies were then placed in tissue culture media and the outgrowths quantitated. The fibroblast outgrowths from all areas did not differ significantly from each other except for the outgrowths from the areas directly treated with mitomycin 0.2 mg/ml which were significantly smaller. In addition then cells were morphologically abnormal although there were foci of normal cells which appeared to be growing from localised areas in the tissue biopsies. The outgrowths from the areas 90 and 180 degrees from the treated area were normal. Intraoperative treatments with mitomycin-c result in long term inhibition of fibroblast proliferation limited to the treated area, when compared with intraoperative and postoperative treatment with 5-FU. Failure of filtration surgery in eyes treated with intraoperative mitomycin may in part be due to unaffected cells reproliferating.

Animals↗

PubMed1992

Epidermal growth factor accelerates connective tissue wound healing in the perforated rat mesentery.

Epidermal growth factor (EGF) has been reported to stimulate healing of wounds in skin, cornea, and gastric mucosa. In the present study, we further investigate the effect of endogenous and exogenous EGF in healing of connective tissue wounds using the rat perforated mesentery model. Healing of mesenteric perforations is accomplished by the connective tissue fibroblasts since there are no interfering variables such as interactions of epithelial cells, desiccation, or foreign materials such as sutures or subcutaneous implants. We performed laparotomy in 114 adult male Sprague-Dawley rats and made 20 standardized perforations in the mesentery of each rat with a scalpel. Rats were randomly assigned to five groups. Group I received no treatment after surgery; Group II received intraperitoneal injections of phosphate-buffered saline (PBS) after surgery and then twice daily for the following 3 days; Group III received 10 micrograms of EGF in the PBS injections according to the same regimen as Group II; Group IV had sham exploration of the submandibular salivary glands; and Group V animals had excision of the submandibular glands 3 days before laparotomy to deprive the main source of EGF in rat. On Days 4 through 10 after surgery rats were sacrificed and the percentage of perforations in each rat which were closed was determined. The curves for the time course of wound closure for Groups IV and V were not different indicating that endogenous submandibular EGF does not play a role in healing of mesenteric wounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Growth factors and corneal endothelial cells: I. Stimulation of bovine corneal endothelial cell DNA synthesis by defined growth factors.

Peptide growth factors and other physiological growth modifiers were evaluated for their ability to stimulate DNA synthesis in early passage cultures of bovine corneal endothelial cells (BCEC). Increasing concentrations of newborn bovine serum (0.5-10%) causes a progressive increase in DNA synthesis, which approached a plateau at 10% serum. Supplementing medium with 10% serum from different lots of newborn bovine serum or fetal bovine serum stimulated significantly different levels of DNA synthesis by BCEC. Addition of epidermal growth factor (EGF) (2 nM) to medium containing 10% newborn or fetal bovine serum further increased DNA synthesis. Dose-response curves for EGF, transforming growth factor-alpha, basic fibroblast growth factor (bFGF), and insulin-like growth factor I showed that each significantly stimulated high levels of DNA synthesis (200-700% increase) compared with BCEC cultured in serum-free medium. Vaccinia growth factor, insulin, and transforming growth factor-beta each significantly stimulated lower levels of DNA synthesis (30-200% increase), whereas nerve growth factor, multiplication stimulating activity, and platelet-derived growth factor all failed to significantly stimulate DNA synthesis above the level of serum-free medium. Other physiological growth modifiers were tested for their effects on DNA synthesis of BCEC. Transferrin and low levels of 3',5'-cyclic monophosphate (cAMP) stimulated very low levels of DNA synthesis (50% increase) whereas linoleic acid, high levels of selenium, or cAMP each inhibited DNA synthesis 25-75% below the level of BCEC cultured in serum-free medium. A series of eight formulations containing various combinations of EGF, FGF, insulin, transferrin, selenium, linoleic acid, retinoic acid, cAMP, heparin, and endothelial cell growth factor were tested for their mitogenic action on BCEC cultures. A formulation containing EGF, insulin, transferrin, selenium, and linoleic acid (EGF + ITSL) stimulated the highest level of DNA synthesis of BCEC, which was approximately 25% higher than the increase stimulated by addition of 10% newborn bovine serum. The formulation consisting of EGF + ITSL was also evaluated as a supplement to corneal storage media. Addition of EGF + ITSL to three corneal storage media (McCarey-Kaufman, K-Sol, CSM) significantly stimulated increases in cell numbers of approximately 50% above the unsupplemented corneal storage media. These results demonstrate that BCEC respond selectively to different defined peptide growth factors and physiological growth modifiers, and suggest that supplementation of corneal storage media with a defined formulation (EGF + ITSL) may enhance corneal endothelial cell density.

Animals↗

PubMed1992

Growth factors and corneal endothelial cells: II. Characterization of epidermal growth factor receptor from bovine corneal endothelial cells.

Epidermal growth factor (EGF) is a potent mitogen for corneal endothelial cells and may play a role in endothelial wound healing. To further characterize the interaction of EGF with endothelial cells, we measured biochemical parameters of 125I-EGF binding to cultured bovine corneal endothelial cells (BCEC), determined the pattern of EGF-induced protein phosphorylation, and investigated the influence of retinoic acid (RA) and transforming growth factor beta (TGF-beta) on EGF-induced DNA synthesis and receptor levels. Binding of 125I-EGF to BCEC was dependent on time, reaching a plateau after approximately 2 h at 37 degrees C, was specific for EGF, and had high affinity (Kd = 100 pM) with approximately 21,000 receptors per cell. Cellular substrates for the EGF receptor kinase, which may function as initial second messengers for EGF, were detected by autoradiography of sodium dodecyl sulfate polyacrylamide gels of 32P-labeled BCEC proteins. EGF stimulated phosphorylation of 170, 37, 21 and 20-kDa proteins. Addition of 1 nM, 100 nM, and 10 microM RA to BCEC cultured in serum-free medium for 24 h progressively inhibited DNA synthesis by up to 80% compared with control cultures. However, when added in combination with 5 nM EGF, 1 nM and 100 nM RA synergistically stimulated DNA synthesis by up to 80% above the level of EGF stimulation without altering EGF receptor levels or binding affinity. Thus, short-term exposure of BCEC to RA potentiated EGF-stimulated DNA synthesis, most likely by acting at a postreceptor step.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Treatment of alkali-injured rabbit corneas with a synthetic inhibitor of matrix metalloproteinases.

Healing of corneal alkali injuries remains a severe clinical challenge. The authors evaluated the effect of a new synthetic inhibitor of matrix metalloproteinases (GM6001 or N-[2(R)-2-(hydroxamido carbonylmethyl)-4-methylpentanoyl]-L-tryptophane methylamide) on preventing ulceration of rabbit corneas after alkali injury. Topical treatment of corneas with severe alkali injuries with 400 micrograms/ml or 40 micrograms/ml GM6001 alone prevented ulceration for 28 days, although 8 of 10 corneas treated with vehicle perforated. Corneas treated with 4 micrograms/ml GM6001 had midstromal depth ulcers. Corneas treated with 400 micrograms/ml of GM6001 contained very few inflammatory cells and had significantly reduced vessel ingrowth compared with vehicle-treated corneas. Epithelial regeneration after moderate alkali injuries also was investigated. Persistent epithelial defects developed 4 days after moderate alkali injury in rabbit corneas treated with vehicle and progressively increased to an average of 20% of the original 6 mm diameter wound by 27 days after moderate alkali injury. By contrast, epithelial regeneration was complete and persisted for 21 days for corneas treated with a formulation containing GM6001 (400 micrograms/ml), epidermal growth factor (10 micrograms/ml), fibronectin (500 micrograms/ml), and aprotinin (400 micrograms/ml). Sporadic punctate staining developed in 20% of the corneas treated with the combination of agents between days 21-28 after moderate alkali injury. These results demonstrate that topical application of GM6001 prevented corneal ulceration after severe alkali injury and that a combination containing GM6001, epidermal growth factor, fibronectin, and aprotinin promoted stable regeneration of corneal epithelium after moderate alkali injury.

Alkalies↗

PubMed1992

Effects of epidermal growth factor, fibroblast growth factor, and transforming growth factor-beta on corneal cell chemotaxis.

The effects of recombinant basic fibroblast growth factor (FGF), epidermal growth factor (EGF), and transforming growth factor-beta (TGF-beta) on migration of human and bovine corneal cells were determined using checkerboard analysis in Boyden chambers. EGF, FGF, and TGF-beta each stimulated high levels of chemotactic migration. Each growth factor, however, induced a different dose-response pattern. Migration stimulated by FGF reached a plateau at a concentration between 100 and 200 ng/ml for endothelial, epithelial, and stromal fibroblasts. By contrast, chemotactic responses to EGF peaked between 10 and 50 ng/ml, then decreased at higher concentrations. TGF-beta also stimulated a peak in migration in all three corneal cells, but the peak of migration occurred at an approximately 1000-fold lower concentration (1 pg/ml) than for EGF. Checkerboard analysis demonstrated that FGF and EGF, but not TGF-beta, stimulated chemokinesis of bovine, stromal, and endothelial cells. These results demonstrate that FGF, EGF, and TGF-beta induce migration in pure populations of bovine and human corneal cells and support the concept that these growth factors may play key roles in corneal wound healing by regulating migration of corneal cells.

Animals↗

PubMed1992

Detection of transforming growth factor-alpha messenger RNA and protein in human corneal epithelial cells.

Human corneal epithelial cells are normally shed from the apical surface and replaced primarily by mitosis of basal cells. Growth factors may regulate this process, but the sources for the growth factors have not been fully established. One potential source for growth factors is tear fluid, and epidermal growth factor (EGF) has been detected in the lacrimal gland and in tears. However, the hydrophilic structure and size of growth factors such as EGF may limit penetration to basal layers of intact epithelium. It is possible that turnover of basal human corneal epithelial cells might be regulated by growth factors acting by an autocrine mechanism. To determine if human corneal epithelial cells synthesize a potential autocrine growth factor, the authors analyzed human corneal epithelial cells for transforming growth factor-alpha (TGF-alpha) messenger RNA and protein, a growth factor that is structurally related to EGF and binds to the EGF receptor. Radioimmunoassay of human corneal epithelial cell cultures detected substantial levels of immunoreactive TGF-alpha (3 ng/10(6) cells). Immunohistochemical staining of human corneas also revealed the presence of immunoreactive TGF-alpha in the corneal epithelium. Northern hybridization with a 32P-labeled complementary DNA probe for TGF-alpha generated a single intense band at 4.4 kilobases, indicating the presence of TGF-alpha messenger RNA in cultured human corneal epithelial cells. These results support the hypothesis that normal turnover of corneal epithelium is controlled by the autocrine production of growth factors, such as TGF-alpha. Growth factors present in tears may function primarily as exocrine factors to stimulate healing of epithelial injuries after the epithelial barrier has been damaged.

Autoradiography↗

PubMed1991

Effect of topical recombinant TGF-beta on healing of partial thickness injuries.

Peptide growth factors produced by platelets, macrophages, epidermal, and dermal cells may play key roles in regulating healing of partial-thickness skin wounds. We examined the effects of recombinant transforming growth factor beta (TGF-beta) on cultures of epidermal and dermal cells in vitro and on healing of partial-thickness injuries in vivo. Increasing concentrations of TGF-beta (0.1, 1, and 10 ng/ml) progressively inhibited serum-stimulated DNA synthesis by up to 95% in cultures of adult human keratinocytes during 48 hr of exposure to TGF-beta. In contrast, TGF-beta (10 and 100 ng/ml) in serum-free media stimulated DNA synthesis by up to 80% compared to serum-free control cultures of adult human dermal fibroblasts. To evaluate the effects of TGF-beta on healing of partial-thickness injuries in vivo, wounds (20 x 20 x 0.6 mm) were created on the dorsal thoracolumbar region of adult pigs by an electrokeratome and were treated daily for 5 days after injury with vehicle or vehicle containing 0.1 or 1 microgram/ml TGF-beta and covered with occlusive dressing. Computerized planimetry of wound photographs demonstrated that TGF-beta treatment stimulated statistically significantly increases in the area of regenerated epidermis compared to wounds treated with saline vehicle on Days 3, 4, 5, and 7 after injury probably due to TGF-beta increasing the rate of epidermal cell migration. In addition, morphometry of biopsy specimens showed that TGF-beta treatment stimulated statistically significant increases in the cross-sectional depths of regenerated dermis compared to wounds treated with saline or Silvadene vehicles on Days 5, 6, and 8 after injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Neovascular growth factors.

Neovascularisation is the biological process of forming new blood vessels. Many conditions can initiate neovascularisation including trauma or chronic ischaemia produced by diseases such as diabetes. Neovascularisation proceeds through a series of steps beginning with destruction of the basement membrane surrounding the microvascular endothelial cells, which allows endothelial cells to extend cytoplasmic buds in the direction of chemotactic factors. Migrating endothelial cells elongate, divide and eventually form tube structures which join to form mature new capillaries. Results of in vitro experiments, in vivo experiments, and clinical studies suggest that peptide growth factors can play key regulatory roles in each step of neovascularisation through both direct and indirect actions. At sites of vascular injuries, degranulating platelets release PDGF, IGF-I, EGF, and TGF-beta. Macrophages and neutrophiles drawn into the ischaemic or injured areas synthesise and release TGF-alpha, TGF-beta, and PDGF, and wounded endothelial cells secrete FGF. These peptide growth factors can stimulate migration, mitosis and differentiation of endothelial cells in culture and can induce neovascularisation in animal models. Clinical correlations suggest that peptide growth factors in the vitreous such as IGF-I and bFGF may promote diabetic retinopathy. As the biological mechanisms of neovascular growth factors become better understood, it may be possible to develop therapeutic approaches to selectively inhibit the peptide growth factors which regulate neovascular diseases.

Angiogenesis Inducing Agents↗

PubMed1990

Epidermal growth factor binding and action on tympanic membranes.

A significant percentage of tympanic membrane (TM) perforations require some form of therapy to heal. Topical application of epidermal growth factor (EGF), a potent mitogen for epidermal and mesodermal cells, promotes healing of injuries in tissues histologically similar to TM, such as cornea and skin. We evaluated TM as a target tissue for EGF action. Specific, high affinity receptors for EGF were detected in TM (Kd = 3.1 nM, 150 fmol receptor/mg protein). Autoradiography of iodine 125-EGF binding to intact TMs revealed that EGF receptors were present on cells in the stratified squamous epithelial layer and in the stromal/mucoepithelial layer. Repetitive treatment of perforated cat TMs with 20 micrograms of EGF formulated in saline induced substantial hyperplasia of epithelial and stromal layers compared to paired TMs treated with saline. A single treatment of perforated cat TMs with 50 micrograms of EGF formulated in a hydrogel or in shredded Gelfoam produced significantly (p less than .05) smaller perforations at 6 days following the operation compared to paired TMs treated with vehicles. These results demonstrate that TM is a target tissue for EGF and that topical treatment with EGF stimulates healing of TM perforations.

Animals↗