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Biomedical subjects

Eric M Brey

Publications and source records attributed to Eric M Brey.

16 recordsLinked to original sources
PubMed2006

Improving endothelial healing with novel chimeric mitogens.

BACKGROUND: Chimeric proteins may be used to direct cell-specific activity. Heparin-binding growth-associated molecule (HBGAM) binds to cell receptors that are relatively more robust on endothelial cells, and it may confer endothelial cell selectivity to potent angiogens such as fibroblast growth factor-1 (FGF-1). METHODS: By ligating fibroblast growth factor or its potent mutant, S130K, to HBGAM, we tested their effect on re-endothelialization after angioplasty injury by using a canine model. RESULTS: Both HBGAM/S130K- and HBGAM/FGF-1-treated arteries had increased neointimal mitotic index and re-endothelialization rates at 30 days compared with control arteries without inducing a significant increase in the neointimal thickness or the ratio of neointimal to medial thickness between treatment and control groups. CONCLUSION: HBGAM/S130K and HBGAM/FGF-1 facilitates endothelial healing without myointimal thickening after canine carotid artery balloon angioplasty injury. Application of these growth factors in fibrin glue may improve endothelialization clinically after angioplasty or endarterectomy.

Animals↗
PubMed2006

Sustained low levels of fibroblast growth factor-1 promote persistent microvascular network formation.

BACKGROUND: Therapeutic neovascularization using high growth factor concentrations may lead to transient vessel formation and abnormal microvascular structure. The goal of this study was to quantify temporal and concentration effects of fibroblast growth factor-1 (FGF-1) on the persistence and morphology of microvascular networks. METHODS: Endothelial cells were incubated in suspension culture forming aggregates that were embedded in fibrin glue (FG) and stimulated with varying concentrations of FGF-1 with of heparin. Capillary networks formed were quantified for 21 days. RESULTS: High FGF-1 concentrations resulted in rapid and intense sprout formation, with excessive branching. At later times, these vessels regressed, with cellular debris in former vessel locations. At later times, the 1-ng/mL group surpassed the high concentration groups with continuous sprout growth and complete FG vascularization by 23 days. CONCLUSION: Sustained low levels of FGF-1 maintained a persistent microvascular network response, whereas higher levels resulted in abnormal phenotype followed by vessel regression.

Animals↗
PubMed2005

Spatial and temporal localization of FGF-2 and VEGF in healing tooth extraction sockets in a rabbit model.

PURPOSE: The purpose of this study was to test the hypothesis that spatial and temporal localization of growth factors FGF-2 and VEGF in a rabbit tooth extraction socket model correlate with the histologic events of healing. MATERIALS AND METHODS: Twenty-four male New Zealand white rabbits divided into 8 groups of 3 were used in the study. Incisor teeth were extracted from both jaws and the healing extraction socket with surrounding jaw bone was harvested at 48 hours, 4 days, 1, 2, 4, 8, 12, and 16 weeks. Tissues were fixed, decalcified, and processed for hematoxylin-eosin and immunohistochemical staining. The sections were stained to detect FGF-2 and VEGF. The stained sections were then imaged and an automated computer program was used to detect the brown diaminobenzidine stain that represented the growth factors of interest. Data was obtained in the form of percentage area and intensity of stain and analyzed using the analysis of variance (ANOVA - Tukey Kramer and Scheffe's post-test). RESULTS: Spatial and temporal differences in localization of FGF-2 and VEGF were observed across all time frames in both jaws. Statistically significant differences in percentage area and intensity of brown diaminobenzidine stain were seen temporally between FGF-2 and VEGF (P < .05). CONCLUSION: The results of this study showed positive correlation of histologic events to spatial and temporal localization of FGF-2 and VEGF in a rabbit tooth extraction model.

Analysis of Variance↗
PubMed2004

Effect of biomaterial properties on bone healing in a rabbit tooth extraction socket model.

In this work we sought to understand the effect of biomaterial properties upon healing bone tissue. We hypothesized that a hydrophilic polymer gel implanted into a bone tissue defect would impede the healing process owing to the biomaterial's prevention of protein adsorption and thus cell adhesion. To test this hypothesis, healing bone was investigated within a rabbit incisor extraction socket, a subcritical size bone defect that resists significant soft tissue invasion by virtue of its conformity. After removal of the incisor teeth, one tooth socket was left as an empty control, one was filled with crosslinked polymer networks formed from the hydrophobic polymer poly(propylene fumarate) (PPF), and one was filled with a hydrogel formed from the hydrophilic oligomer oligo(poly(ethylene glycol) fumarate) (OPF). At five different times (4 days as well as 1, 2, 4, and 8 weeks), jaw bone specimens containing the tooth sockets were removed. We analyzed bone healing by histomorphometrical analysis of hematoxylin and eosin stained sections as well as immunohistochemically stained sections. The proposed hypothesis, that a hydrophilic material would hinder bone healing, was supported by the histomorphometrical results. In addition, the immunohistochemical results reflect molecular signaling indicative of the early invasion of platelets, the vascularization of wound-healing tissue, the differentiation of migrating progenitor cells, and the formation and remodeling of bone tissue. Finally, the results emphasize the need to consider biomaterial properties and their differing effects upon endogenous growth factors, and thus bone healing, during the development of tissue engineering devices.

Animals↗
PubMed2004

Formation, architecture and polarity of female germline cyst in Xenopus.

Little is known about the formation of germline cyst and the differentiation of oocyte within the cyst in vertebrates. In the majority of invertebrates in the initial stages of gametogenesis, male and female germ cells develop in full synchrony as a syncytia of interconnected cells called germline cysts (clusters, nests). Using electron microscopy, immunostaining and three-dimensional reconstruction, we were able to elucidate the process of cyst formation in the developing ovary of the vertebrate Xenopus laevis. We found that the germline cyst in Xenopus contains 16 cells that are similar in general architecture and molecular composition to the cyst in Drosophila. Nest cells are connected by cytoplasmic bridges that contain ring canal-like structures. The nest cells contain a structure similar to the Drosophila fusome that that is probably involved in anchoring of the centrioles and organization of the primary mitochondrial cloud (PMC) around the centriole. We also find that in contrast to other organisms, in Xenopus, apoptosis is a rare event within the developing ovary. Our studies indicate that the processes responsible for the formation of female germline cysts and the establishment of germ cell polarity are highly conserved between invertebrates and vertebrates. The dissimilarities between Drosophila and Xenopus and the uniqueness of each system probably evolved through modifications of the same fundamental design of the germline cyst.

Animals↗
PubMed2004

Heparin-independent mitogenicity in an endothelial and smooth muscle cell chimeric growth factor (S130K-HBGAM).

BACKGROUND: Through site-directed mutagenesis we have created a favorable fibroblast growth factor-1 (FGF-1) mutant (S130K) and linked it to a heparin-binding growth-associated molecule (HBGAM) to form the chimera S130K-HBGAM creating a heparin-independent, endothelial cell (EC)-specific mitogen. METHODS: The proliferative responses of primary canine carotid artery smooth muscle cells (SMC) and jugular vein EC to FGF-1, S130K, or S130K-HBGAM, with and without heparin (5 U/mL), was quantitated by measuring tritiated thymidine uptake over 24 hours and expressing the results as percent of positive control (20% fetal bovine serum [FBS]) for group comparison. RESULTS: Unlike FGF-1, both S130K and S130K-HBGAM are heparin-independent mitogens for EC and SMC. S130K-HBGAM was equivalent to FGF-1 with heparin at 6 nmol/L. S130K-HBGAM did not demonstrate relative EC specificity in this assay. CONCLUSIONS: At higher concentrations, S130K-HBGAM is a potent, heparin-independent EC and SMC mitogen. Co-culture assays and in vivo delivery models may demonstrate EC specificity not identified in this single cell type proliferation assay.

Analysis of Variance↗
PubMed2004

Spatial and temporal localization of secretory IgA in healing tooth extraction sockets in a rabbit model.

PURPOSE: The purpose of this study was to look at the spatial and temporal localization of secretory IgA in healing tooth extraction sockets in a rabbit model. MATERIALS AND METHODS: Twenty-four male New Zealand White rabbits were used in the study. Incisor teeth were extracted from both jaws, and the healing extraction socket with the surrounding jaw bone was harvested at 48 hours, 4 days, and 1, 2, 4, 8, 12, and 16 weeks. Tissues were fixed, decalcified, and processed for hematoxylin and eosin and immunohistochemical staining. The sections were stained to detect secretory IgA. The stained sections were then imaged, and an automated computer program was used to detect the brown 3,3'-diaminobenzidine stain that represented the secretory IgA. The data were obtained in the form of percentage area and intensity of stain and analyzed using analysis of variance (Tukey-Kramer and Scheffé's tests). RESULTS: Spatial and temporal differences in localization of secretory IgA were observed across time frames in both jaws. CONCLUSION: The results of this study showed definite trends in the spatial and temporal localization of secretory IgA in healing tooth extraction sockets in a rabbit model.

Alveolar Process↗
PubMed2004

Three-dimensional, quantitative analysis of desmin and smooth muscle alpha actin expression during angiogenesis.

Angiogenic therapies have been designed for many pathological conditions, but when used as a single therapy, the clinical results have fallen short of expectations. In addition, strategies for vascularizing engineered tissues have been unsuccessful in promoting the formation of an extensive, stable vasculature. Recent evidence suggests that mural cells play a critical role in the success of these approaches, but our current understanding of the function of mural cells in the microvasculature is incomplete. We studied the three-dimensional spatial and temporal kinetics of the mural cell markers desmin and smooth muscle alpha actin during angiogenesis in an in vivo fibrin gel model. The results led to the following conclusions: (1) desmin and smooth muscle alpha actin positive cells are present during the initial development of vessel sprouts; (2) the presence of these cells in the microvasculature is not always an indicator of vessel stability; and (3) the mural cell markers desmin and smooth muscle alpha actin exhibit differential staining patterns during vessel formation. These findings shed new light on the complexity of the relationship between mural cells and the formation of a mature, stable microcirculation.

Actins↗
PubMed2003

Spatial and temporal localization of transforming growth factor-beta1, bone morphogenetic protein-2, and platelet-derived growth factor-A in healing tooth extraction sockets in a rabbit model.

PURPOSE: The purpose of this study was to test the hypothesis that spatial and temporal localization of growth factors transforming growth factor (TGF)-beta1, bone morphogenetic protein (BMP)-2, and platelet derived growth factor (PDGF)-A in a rabbit tooth extraction model correlate with the histologic events contributing toward healing. MATERIALS AND METHODS: Twenty-four male New Zealand White rabbits were used in the study. Incisor teeth were extracted from both jaws, and the healing extraction socket with the surrounding jaw bone was harvested at 48 hours, 4 days, and 1, 2, 4, 8, 12, and 16 weeks. Tissues were fixed, decalcified, and processed for hematoxylin and eosin and immunohistochemical staining. The sections were stained to detect TGF-beta1, BMP-2, and PDGF-A. Stained sections were then imaged, and an automated computer program was used to detect the brown 3,3'-diaminobenzidine regions representing the location of growth factors of interest. The data were collected in terms of percentage area and intensity of stain, and an analysis of variance was conducted (Tukey-Kramer and Scheffe's test) for statistical comparison between different time points, jaws, and growth factors. These results were also compared with hematoxylin and eosin-stained histologic specimens obtained at similar time points. RESULTS: Spatial and temporal differences in localization of TGF-beta1, BMP-2, and PDGF-A were observed across all time frames in both jaws. Statistically significant differences in percentage area and intensity of brown diaminobenzidine stain were detected temporally between TGF-beta1, BMP-2, and PDGF-A (P < or =.0001). CONCLUSION: The results of this study showed positive correlation between histologic events and the spatial and temporal localization of TGF-beta1, BMP-2, and PDGF-A in a rabbit tooth extraction model.

3,3'-Diaminobenzidine↗
PubMed2003

Automated selection of DAB-labeled tissue for immunohistochemical quantification.

The increased use of immunohistochemistry (IHC) in both clinical and basic research settings has led to the development of techniques for acquiring quantitative information from immunostains. Staining correlates with absolute protein levels and has been investigated as a clinical tool for patient diagnosis and prognosis. For these reasons, automated imaging methods have been developed in an attempt to standardize IHC analysis. We propose a novel imaging technique in which brightfield images of diaminobenzidene (DAB)-labeled antigens are converted to normalized blue images, allowing automated identification of positively stained tissue. A statistical analysis compared our method with seven previously published imaging techniques by measuring each one's agreement with manual analysis by two observers. Eighteen DAB-stained images showing a range of protein levels were used. Accuracy was assessed by calculating the percentage of pixels misclassified using each technique compared with a manual standard. Bland-Altman analysis was then used to show the extent to which misclassification affected staining quantification. Many of the techniques were inconsistent in classifying DAB staining due to background interference, but our method was statistically the most accurate and consistent across all staining levels.

Animals↗
PubMed2002

A technique for quantitative three-dimensional analysis of microvascular structure.

Research into angiogenesis and vascular microarchitecture has contributed to progress in a wide variety of biomedical fields, but increased understanding is limited, in part, by the available assays and imaging modalities. Techniques that allow quantitation of vascular microarchitecture are needed. A comprehensive method is presented that uses 6-microm-thick serial sections of frozen tissue samples, immunostaining for CD31, brightfield microscopy, automated alignment of two-dimensional serial sections, and volume rendering to produce high-resolution, three-dimensional, quantifiable images of microvascular structure. Application of the technique is shown by characterizing vascularization into a fibrin gel implanted against the skeletal muscle of rats and explanted after 7 days. Comparing measurements from automated and manually aligned MRI and fibrin samples verified quantitation. Automation removes concerns of observer bias or variation inherent in manual alignment and increases the speed of analysis. Analysis of the fibrin gel reveals a dense (4.3 +/- 1.1% endothelial cell density) network of tortuous (1.37 +/- 0.05 tortuosity) capillaries that replaces the gel as it degrades. There is a high level of void space (22.8 +/- 3.6%) in the gel, and average capillary length in the fibrovascular tissue was 93.0 +/- 7.4 microm. Data obtained from these automatically aligned images agreed with those obtained using manual analysis (no statistical difference), and the results are consistent with data from traditional methods.

Animals↗
PubMed2002

Quantification of vascular density using a semiautomated technique for immunostained specimens.

OBJECTIVE: To develop a semiautomated, quantitative techniquefor the assessment of vascular density in immunohistochemically stained tissue sections using diaminobenzidine tetrahydrochloride (DAB) and hematoxylin as chromagens. STUDY DESIGN: A semiautomated thresholding technique was developed to quantitate vascular density in tissue sections stained with anti-CD31 (1 degrees antibody). The immunohistochemically stained specimens were digitally imaged using a 24-bit color camera. The blue component of the RGB image was segmented using a variable high-pass filter. After thresholding, the segmented areas (CD31 positive) were quantified and vascular density determined. The validity of the method was verified by calculating the precision of the technique using the coefficient of repeatability and by quantifying its agreement with manual analysis according to the Bland-Altman approach. RESULTS: Vascular endothelial cells were specifically selected using anti-CD31 as the primary antibody and the appropriate horseradish peroxidase-conjugated secondary antibody. Utilizing the semiautomated thresholding technique, the separation of DAB-stained tissuefrom non-DAB-stained tissue was achieved. The method developed possesses a low coefficient of repeatability (0.49%), agrees well with manual assessment (mean difference = -0.29 +/- 0.92%), is highly automated and is user friendly. CONCLUSION: A novel semiautomated technique for the quantification of vascular density was developed. This technique provides a method for reproducible measurement of immunostaining procedures (immunohistochemistry, immunocytochemistry and in situ hybridization) utilizing immunoperoxidase techniques with DAB as a chromagen.

3,3'-Diaminobenzidine↗
PubMedDate not supplied

Ovine model for engineering bone segments.

We propose a large animal model for bone tissue engineering that yields quantitative data and simulates clinical methods and tissue needs. Skeletally mature domestic sheep (n = 20) were each implanted with three rectangular (1 x 1 x 4 cm), hollow tissue-molding chambers that were empty (control) or filled with equal weights (6.71-6.78 g) of particulate autologous bone graft (MBG) or bone graft that was autoclaved to denature stored growth factors (DeMBG). MBG provided scaffold and bioactive factors, and DeMBG provided only scaffold. The chambers were enclosed on five sides and securely implanted so that the open face was apposed to the osteogenic (i.e., cambium) layer of the rib periosteum for 3, 6, 9, 12, or 24 weeks, after which the chambers were harvested and the contents analyzed. Each chamber contained osseous and fibrovascular tissue. MBG-containing chambers had the best maintenance of tissue volume compared with DeMBG-containing or empty chambers, but it still decreased steadily over time. Despite this, the MBG-containing chambers showed continuous active bone formation. There was increasing calcified tissue with penetration of osteogenesis up to a mean of 0.75 +/- 0.15 cm from the periosteum by 9 weeks, and the osteogenic area peaked at 0.59 +/- 0.13 cm2 by 12 weeks. Using quantitative measures that reflect clinical needs (i.e., tissue volume, shape, and quality), it was possible to distinguish differences in performance associated with manipulation of implanted scaffold and bioactive factors. This ovine model may serve as a useful tool to develop clinical osseous tissue-engineering strategies.

Absorbable Implants↗
PubMedDate not supplied

Therapeutic neovascularization: contributions from bioengineering.

A number of pathological entities and surgical interventions could benefit from therapeutic stimulation of new blood vessel formation. Although strategies designed for promoting neovascularization have shown promise in preclinical models, translation to human application has met with limited success when angiogenesis is used as the single therapeutic mechanism. While clinical protocols continue to be optimized, a number of exciting new approaches are being developed. Bioengineering has played an important role in the progress of many of these innovative new strategies. In this review, we present a general outline of therapeutic neovascularization, with an emphasis on investigations using engineering principles to address this vexing clinical problem. In addition, we identify some limitations and suggest areas for future research.

Angiogenesis Inducing Agents↗