Enhanced intestinal anastomotic healing with gelatin hydrogel incorporating basic fibroblast growth factor

Anastomotic leakage is a common complication of intestinal surgery. In an attempt to resolve this issue, a promising approach is enhancement of anastomotic wound healing. A method for controlled release of basic fibroblast growth factor (bFGF) using a gelatin hydrogel was developed with the objective of investigating the effects of this technology on intestinal anastomotic healing. The small intestine of Wistar rats was cut, end-to-end anastomosis was performed and rats were divided into three groups: bFGF group (anastomosis wrapped with a hydrogel sheet incorporating bFGF), PBS group (wrapped with a sheet incorporating phosphate-buffered saline solution) and NT group (no additional treatment). Degradation profiles of gelatin hydrogels in vivo and histological examinations were performed using gelatin hydrogels with various water contents and bFGF concentrations to define the optimal bFGF dose and hydrogel biodegradability. The anastomotic wound healing process was evaluated by histological examinations, adhesion-related score and bursting pressure. The optimal water content of the hydrogel and bFGF dose was determined as 96% and 30 µg per sheet, respectively. Application of bFGF significantly enhanced neovascularization, fibroblast infiltration and collagen production around the anastomotic site when compared with the other groups. Bursting pressure was significantly increased in the bFGF group. No significant difference was observed in the adhesion-related score among the groups and no anastomotic obstruction and leakage were observed. Therefore controlled release of bFGF enhanced healing of an intestinal anastomosis during the early postoperative period and is a promising method to suppress anastomotic leakage. Copyright © 2013 John Wiley & Sons, Ltd.

Bioengineering a highly vascularized matrix for the ectopic transplantation of islets

Islet transplantation is a promising treatment for Type 1 diabetes; however limitations of the intra-portal site and poor revascularization of islets must be overcome. We hypothesize that engineering a highly vascularized collagen-based construct will allow islet graft survival and function in alternative sites. In this study, we developed such a collagen-based biomaterial. Neonatal porcine islets (NPIs) were embedded in collagen matrices crosslinked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide containing combinations of chondroitin-6-sulfate, chitosan, and laminin, and compared with controls cultured in standard media. Islets were examined for insulin secretory activity after 24 h and 4 d and for apoptotic cell death and matrix integrity after 7 d in vitro. These same NPI/collagen constructs were transplanted subcutaneously in immunoincompetent B6.Rag-/- mice and then assessed for islet survival and vascularization. At all time points assessed during in vitro culture there were no significant differences in insulin secretory activity between control islets and those embedded in the collagen constructs, indicating that the collagen matrix had no adverse effect on islet function. Less cell death was observed in the matrix with all co-polymers compared with the other matrices tested. Immunohistochemical analysis of the grafts post-transplant confirmed the presence of intact insulin-positive islets; grafts were also shown to be vascularized by von Willebrand factor staining. This study demonstrates that a collagen, chondroitin-6-sulfate, chitosan, and laminin matrix supports islet function in vitro and moreover allows islet survival and vascularization post-transplantation; therefore, this bio-engineered vascularized construct is capable of supporting islet survival.

Cell-based approaches to the engineering of vascularized bone tissue

This review summarizes recent efforts to create vascularized bone tissue in vitro and in vivo through the use of cell-based therapy approaches. The treatment of large and recalcitrant bone wounds is a serious clinical problem, and in the United States approximately 10% of all fractures are complicated by delayed union or non-union. Treatment approaches with the use of growth factor and gene delivery have shown some promise, but results are variable and clinical complications have arisen. Cell-based therapies offer the potential to recapitulate key components of the bone-healing cascade, which involves concomitant regeneration of vasculature and new bone tissue. For this reason, osteogenic and vasculogenic cell types have been combined in co-cultures to capitalize on the function of each cell type and to promote heterotypic interactions. Experiments in both two-dimensional and three-dimensional systems have provided insight into the mechanisms by which osteogenic and vasculogenic cells interact to form vascularized bone, and these approaches have been translated to ectopic and orthotopic models in small-animal studies. The knowledge generated by these studies will inform and facilitate the next generation of pre-clinical studies, which are needed to move cell-based orthopaedic repair strategies into the clinic. The science and application of cytotherapy for repair of large and ischemic bone defects is developing rapidly and promises to provide new treatment methods for these challenging clinical problems.

Unravelling the blood supply to the zebrafish pharyngeal jaws and teeth

We describe the vascular supply to the pharyngeal jaws and teeth in zebrafish, from larval stages to juveniles, using serial high quality semithin sections and 3D reconstructions. We have identified that the arterial blood supply to the last pair of branchial arches, which carries the teeth, issues from the hypobranchial artery. Surprisingly, the arteries supplying the pharyngeal jaws show an asymmetric branching pattern that is modified over ontogeny. Moreover, the blood vessel pattern that serves each jaw can best be described as a sinusoidal cavity encircling the bases of both the functional and replacement teeth. Capillaries branching from this sinusoidal cavity enter the pulp and constitute the intrinsic blood supply to the attached teeth. The role of these blood vessels during tooth development (whether instructive or nutritive) remains to be determined and requires further study. However, we have provided a firm morphological basis that will aid in the interpretation of experiments addressing this question.

Increased porosity of electrospun hybrid scaffolds improved bladder tissue regeneration

The object of this study was to investigate the role of scaffold porosity on tissue ingrowth using hybrid scaffolds consisting of bladder acellular matrix and electrospun poly (lactide-co-glycolide) (PLGA) microfibers that mimic the morphological characteristics of the bladder wall in vitro and in vivo. We compared single-spun (SS) PLGA scaffolds with more porous cospun (CS) scaffolds (PLGA and polyethylene glycol). Scaffolds were characterized by scanning electron microscopy. Bladder smooth muscle cells (SMCs) were seeded, and proliferation and histological assays were performed. Sixteen rats were subjected to augmentation cystoplasty with seeded SS or CS scaffolds, morphological, and histological studies were performed 2 and 4 weeks after implantation. The porosities of SS and CS scaffolds were 73.1 ± 2.9% and 80.9 ± 1.5%, respectively. The in vitro evaluation revealed significantly deeper cell migration into CS scaffolds. The in vivo evaluation showed significant shrinkage of SS scaffolds (p = 0.019). The histological analysis revealed a bladder wall-like structure with urothelial lining and SMC infiltration in both groups. The microvessel density was significantly increased in the CS scaffolds (p < 0.001). Increasing the porosity of electrospun hybrid scaffolds is an effective strategy to enhance cell proliferation and distribution in vitro and tissue ingrowth in vivo.

Color-coded imaging of spontaneous vessel anastomosis in vivo

Vessel anastomosis is important in tumor angiogenesis as well as for vascularization therapy for ischemia and other diseases. We report here the development of a color-coded imaging model that can visualize the anastomosis between blood vessels of red fluorescent protein (RFP)-expressing vessels in vascularized Gelfoam® previously transplanted into RFP transgenic mice and then re-transplanted into nestin-driven green fluorescent protein (ND-GFP) mice where nascent blood vessels express GFP. Gelfoam® was initially transplanted subcutaneously in the flank of transgenic RFP nude mice. Skin flaps were made at 14 days after transplantation of Gelfoam® to allow observation of vascularization of the Gelfoam® using confocal fluorescence imaging. The implanted Gelfoam® became highly vascularized with RFP vessels. Fourteen days after transplantation into RFP transgenic nude mice, the Gelfoam® was removed and re-transplanted into the subcutis on the flank of ND-GFP transgenic nude mice in which nascent blood vessels express GFP. Skin flaps were made and anastomosis between the GFP-expressing nascent blood vessels of ND-GFP transgenic nude mice and RFP blood vessels in the Gelfoam® was imaged 14 and 21 days after re-transplantation. The results presented in this report indicate a possible mechanism for tumor angiogenesis and suggest a new paradigm of therapeutic revascularization of ischemic organs requiring new blood vessels and in other diseases.

Slowly degradable porous silk microfabricated scaffolds for vascularized tissue formation

There is critical clinical demand for tissue-engineered (TE), three-dimensional (3D) constructs for tissue repair and organ replacements. Current efforts toward this goal are prone to necrosis at the core of larger constructs because of limited oxygen and nutrient diffusion. Therefore, critically sized 3D TE constructs demand an immediate vascular system for sustained tissue function upon implantation. To address this challenge the goal of this project was to develop a strategy to incorporate microchannels into a porous silk TE scaffold that could be fabricated reproducibly using microfabrication and soft lithography. Silk is a suitable biopolymer material for this application because it is mechanically robust, biocompatible, slowly degrades in vivo, and has been used in a variety of TE constructs. We report the fabrication of a silk-based TE scaffold that contains an embedded network of porous microchannels. Enclosed porous microchannels support endothelial lumen formation, a critical step toward development of the vascular niche, while the porous scaffold surrounding the microchannels supports tissue formation, demonstrated using human mesenchymal stem cells. This approach for fabricating vascularized TE constructs is advantageous compared to previous systems, which lack porosity and biodegradability or degrade too rapidly to sustain tissue structure and function. The broader impact of this research will enable the systemic study and development of complex, critically-sized engineered tissues, from regenerative medicine to in vitro tissue models of disease states.

Heparinized collagen scaffolds with and without growth factors for the repair of diaphragmatic hernia: construction and in vivo evaluation

A regenerative medicine approach to restore the morphology and function of the diaphragm in congenital diaphragmatic hernia is especially challenging because of the position and flat nature of this organ, allowing cell ingrowth primarily from the perimeter. Use of porous collagen scaffolds for the closure of surgically created diaphragmatic defects in rats has been shown feasible, but better ingrowth of cells, specifically blood vessels and muscle cells, is warranted. To stimulate this process, heparin, a glycosaminoglycan involved in growth factor binding, was covalently bound to porous collagenous scaffolds (14%), with or without vascular endothelial growth factor (VEGF; 0.4 µg/mg scaffold), hepatocyte growth factor (HGF; 0.5 µg/mg scaffold) or a combination of VEGF + HGF (0.2 + 0.5 µg/mg scaffold). All components were located primarily at the outside of scaffolds. Scaffolds were implanted in the diaphragm of rats and evaluated after 2 and 12 weeks. No herniations or eventrations were observed, and in several cases, growth factor-substituted scaffolds showed macroscopically visible blood vessels at the lung site. The addition of heparin led to an accelerated ingrowth of blood vessels at 2 weeks. In all scaffold types, giant cells and immune cells were present primarily at the liver side of the scaffold, and immune cells and individual macrophages at the lung side; these cell types decreased in number from week 2 to week 12. The addition of growth factors did not influence cellular response to the scaffolds, indicating that further optimization with respect to dosage and release profile is needed.

Accelerating the early angiogenesis of tissue engineering constructs in vivo by the use of stem cells cultured in matrigel

In tissue engineering research, generating constructs with an adequate extent of clinical applications remains a major challenge. In this context, rapid blood vessel ingrowth in the transplanted tissue engineering constructs is the key factor for successful incorporation. To accelerate the microvascular development in engineered tissues, we preincubated osteoblast-like cells as well as mesenchymal stem cells or a combination of both cell types in Matrigel-filled PLGA scaffolds before transplantation into the dorsal skinfold chambers of balb/c mice. By the use of preincubated mesenchymal stem cells, a significantly accelerated angiogenesis was achieved. Compared with previous studies that showed a decisive increase of vascularization on day 6 after the implantation, we were able to halve this period and achieve explicitly denser microvascular networks 3 days after transplantation of the tissue engineering constructs. Thereby, the inflammatory host tissue response was acceptable and low, comparable with former investigations. A co-incubation of osteoblast-like cells and stem cells showed no additive effect on the density of the newly formed microvascular network. Preincubation of mesenchymal stem cells in Matrigel is a promising approach to develop rapid microvascular growth into tissue engineering constructs. After the implantation into the host organism, scaffolds comprising stem cells generate microvascular capillary-like structures exceptionally fast. Thereby, transplanted stem cells likely differentiate into vessel-associated cells. For this reason, preincubation of mesenchymal stem cells in nutrient solutions supporting different steps of angiogenesis provides a technique to promote the routine use of tissue engineering in the clinic.

Beautiful, complicated--and intelligent? Novel aspects of the thigmonastic stamen movement in Loasaceae

In a recent study we investigated the complex mechanisms regulating the pollen release via thigmonastic stamen movement found exclusively in Loasaceae subfamily Loasoideae. We demonstrated that stamen movement is modulated by abiotic (light and temperature) as well as biotic stimuli (pollinator availability and visitation frequency). This is explained as a mechanism to adjust the rate of stamen movement and thus pollen dispensation to different environmental conditions in order to optimize pollen transfer. Stamen movement is rapid and thus a near-immediate response to pollinator visits. However, Loasaceae flowers also show a response to biotic stimuli on a longer time scale, by adjusting the duration of both the staminate and the carpellate phase of the anthesis. We here present two additional data sets on species not previously studied, underscoring the shortening of the staminate phase in the presence of pollinator visits vs. their absence and the shortening of the carpellate phase after pollination. Overall, the plant shows not only a rapid but an "intelligent" reaction to its environment in adjusting anthesis and pollen presentation to a range of factors. The physiological and morphological bases of the stamen movement are poorly understood. Our previous study showed that there is no direct spatial relationship between the place of stimulation in the flower and the stamen bundle activated. We here further show the morphological basis for stamen movement from a reflexed into an erect position: Only the basal part of the filament curves around the receptacle, while the upper part of the filament retains its shape. We hypothesize that the stimulus is transmitted over the entire receptacle and the place of reaction is determined by stamen maturity, not the location of the stimulus.

Mesenteric neovascularization with distraction-induced intestinal growth: enterogenesis

BACKGROUND

Distraction-induced enterogenesis, whereby the intestine lengthens with application of linear forces, is an emerging area which may provide a unique treatment for short bowel syndrome. With an increase in overall tissue mass, there is an increase in oxygen and nutrient demand. We hypothesized that a neovascularization within the mesentery is necessary to support the growing small bowel.

METHODS

A curvilinear hydraulic device was used to induce growth within the small bowel of Yorkshire pigs, and the intestine was harvested after 14 days. High-resolution gross pictures were recorded of the mesentery at implantation and at harvest, and CT imaging of the bowel and mesentery was performed at harvest after dye injection.

RESULTS

After 2 weeks of distraction, an average of 72.5 % (8.7 cm) bowel lengthening was achieved. Gross images of the mesentery between major vessels showed a blossoming of the microvasculature and this was confirmed by CT imaging with 3D reconstruction. Mesenteric sample taken from the distracted segment had a fourfold increase in the volume of microvasculature versus controls.

CONCLUSION

Enterogenesis results not only in increased bowel length, but also significant increase in the mesenteric microvascularity. Presumably, this sustains the lengthened segment after application of longitudinal forces.

Uterine artery embolization for leioyomas, ultrasonography and angiography aspects

OBJECTIVE AND RATIONALE

The purpose of this study is to evaluate the degree of fibroid shrinkage which well correlates with symptom regression, and thus to assess the effectiveness of the procedure.

METHOD

31 patients were included in the trial after selection. All the patients were thoroughly evaluated before embolization, the following day and at a month after but also at 3 months for 10 of them. A certain protocol was followed passing through well established steps. The purpose was to discover and rule out any associated possible disease and to assess and grade the symptoms, ultrasound and angiographic aspects.

RESULTS

Regarding the uterus, its volume evolution registered a descending trend, the mean decrease at 30 days being of 25% (-81,6 cm³) and at 90 days of 52%(-173,15 cm³). The fibroids also decreased statistically, the mean global variation at 30 days registering a decrease of -17,66 cm³(27%) and 61% at day 90. The mean global reduction at 30 days was of 44% (-33,18 cm³) and of 62% (-60,85 cm³) at 90 days. Absence of uterine anastomoses lead to proper fibroid decrease whereas their presence diminished the chances.

CONCLUSIONS

The uterine and fibroid volumes registered a statistical volume decrease at 30 and 90 days in comparison with the volumes before embolization. Absence of uterine anastomoses led to proper fibroid decrease. Longer evaluation time is needed for an accurate evaluation of volume reduction degree.

Vascularization of carotid plaque in recently symptomatic patients is associated with the occurrence of transcranial microembolic signals

BACKGROUND AND PURPOSE

Microembolic signals (MES) are detectable in the middle cerebral artery by transcranial ultrasound downstream to atherosclerotic lesions of the internal carotid artery (ICA) in patients with stroke or transient ischaemic attack. The occurrence of MES predicts future risk of stroke in patients with symptomatic and asymptomatic carotid stenosis. The detection of intra-plaque neo-vascularization by contrast-enhanced ultrasound (CEUS) in atherosclerotic plaques of the ICA is associated with future cardiovascular/cerebrovascular events. We investigated whether there is an association between both surrogate markers of future vascular events.

METHODS

Forty-one patients with symptomatic atherosclerotic plaques underwent ipsilateral transcranial ultrasound MES detection for 30 min followed by a CEUS investigation of the plaque. The occurrence and number of MES was documented, and the degree of intra-plaque neo-vascularization was measured semi-quantitatively.

RESULTS

During the 30 min investigation, 17 patients had MES and nine of them showed neo-vascularization of the atherosclerotic plaque. The remaining 24 patients did not have MES, and only in four patients of this group could plaque neo-vascularization be demonstrated (P = 0.020).

CONCLUSIONS

We found an association between the occurrence of MES and the presence of neo-vascularization in patients with symptomatic atherosclerotic carotid plaque. Therefore, plaque neo-vascularization might also be a surrogate marker of future stroke risk.

Enhanced endothelial differentiation of adipose-derived stem cells by substrate nanotopography

Adipose-derived stem cells (ADSCs) have great potential as a cell source for tissue engineering and regenerative medicine because they are easier to obtain, have lower donor-site morbidity and are available in larger numbers than stem cells harvested using bone marrow aspiration. Until now, little has been known about how nanotopography affects the proliferation and endothelial differentiation of ADSCs. In the present study, two nanograting substrates with a period (ridge and groove) of about 250 and 500 nm, respectively, were fabricated on quartz and their effect on ADSC fate was investigated. The results showed that proliferation of ADSCs on nanograting substrates decreased while cell attachment was not significantly affected compared to a flat substrate. Endothelial differentiation of ADSCs on both flat and nanograting substrates can be induced with vascular endothelial growth factor, as shown by immunofluorescent staining. Quantitative real-time PCR analysis showed significantly enhanced upregulation of vWF, PECAM-1 and VE-cadherin at the gene level by ADSCs on the nanograting substrates. In vitro angiogenesis assay on Matrigel showed that nanograting substrates enhanced capillary tube formation. This study highlights the beneficial influence of nanotopography on the differentiation of ADSC into endothelial cells which play an important role in vascularization.

HGF Airway Over-expression Leads to Enhanced Pulmonary Vascularization without Induction of VEGF

The hepatocyte growth factor (HGF)/c-Met signaling pathway mediates angiogenesis. We have previously reported that airway expression of a human HGF transgene (HGF TG) produced mice that were more susceptible to lung tumorigenesis induced by 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK). Here we show untreated HGF TG mice display enhanced vascularization (40 wks) and enhanced lymph vessel formation (20 wks) in the lungs compared to wild-type (WT) littermates, as ascertained by microvessel density. We profiled mRNA expression from HGF TG and WT mice for genes involved in angiogenesis. We consistently found significant decreases in expression of the VEGF family of angiogenic genes, including Vegfa, Vegfb, Vegfc, and Vegfd / Figf. Decreases were confirmed in whole lung protein extracts by immunoblot. Similar patterns of down-regulation were observed at 10, 20, and 40 wks of age. Vandetanib, an inhibitor of VEGFR2 and VEGFR3, did not prevent the increase in microvessel density observed in HGF TG mice. Reduction in VEGF pathway genes was also detected in lung tumors derived from NNK-treated HGF TG mice. HGF TG lung tumors also showed increased expression of five Cxcl family genes including Cxcl1 and Cxcl2 (murine forms of IL8). These results suggest increased vascularization produced by airway over-expression of HGF occurs through direct activation of c-Met on endothelial cells, rather than induction of VEGF pathways. Elevated HGF may also increase expression of inflammatory mediators that contribute to lung tumor progression.

Composite islet-kidneys from single baboon donors cure diabetes across fully allogenic barriers

We have previously reported that transplantation (Tx) of prevascularized donor islets as composite islet-kidneys (IK) reverses diabetic hyperglycemia in miniature swine. In order to test the potential clinical applicability of this strategy, we have extended it to a fully allogeneic nonhuman primate model. IKs were prepared in baboons by isolating islets from 50% to 70% partial pancreatectomies and injecting them under the autologous renal capsule, allowing vascularization before allogeneic Tx. Baboons with diabetes induced by stereptozotocin or total pancreatectomy, received composite IKs (n = 3) or free islets under the renal capsule or intraportally (n = 3), across fully allogeneic barriers with an immunosuppressive regimen consisting of ATG followed by MMF and tacrolimus. FBS of two of IK recipients decreased immediately after Tx and no insulin therapy was required throughout the experimental period (225 and 301 days). In contrast, all recipients of allogeneic free islets showed unstable FBS levels and required insulin within 2 months. We conclude that in addition to maintaining creatinine in the normal range, fully allogeneic IKs from single primate donors can achieve glucose regulation without insulin therapy, while free islets do not. These results support the feasibility of composite allogeneic IK Tx as a potential cure for end-stage diabetic nephropathy.

Vascularization of three-dimensional collagen hydrogels using ultrasound standing wave fields

The successful fabrication of large, three-dimensional (3-D) tissues and organs in vitro requires the rapid development of a vascular network to maintain cell viability and tissue function. In this study, we utilized an application of ultrasound standing wave field (USWF) technology to vascularize 3-D, collagen-based hydrogels in vitro. Acoustic radiation forces associated with USWF were used to noninvasively organize human endothelial cells into distinct, multicellular planar bands within 3-D collagen gels. The formation and maturation of capillary-like endothelial cell sprouts were monitored over time and compared with sham-exposed collagen constructs, which were characterized by a homogeneous cell distribution. USWF-induced cell banding accelerated the formation and elongation of capillary-like sprouts, promoted collagen fiber alignment and resulted in the maturation of endothelial cell sprouts into lumen-containing, anastomosing networks found throughout the entire volume of the collagen gel. USWF-induced endothelial cell networks contained large, arteriole-sized lumen areas that branched into smaller, capillary-sized structures indicating the development of vascular tree-like networks. In contrast, sprout formation was delayed in sham-exposed collagen gels and endothelial cell networks were absent from sham gel centers and failed to develop into the vascular tree-like structures found in USWF-exposed constructs. Our results demonstrate that USWF technology leads to rapid and extensive vascularization of 3-D collagen-based engineered tissue and, therefore, provide a new strategy to vascularize engineered tissues in vitro.

MtbHLH1, a bHLH transcription factor involved in Medicago truncatula nodule vascular patterning and nodule to plant metabolic exchanges

This study aimed at defining the role of a basic helix-loop-helix (bHLH) transcription factor gene from Medicago truncatula, MtbHLH1, whose expression is upregulated during the development of root nodules produced upon infection by rhizobia bacteria. We used MtbHLH1 promoter::GUS fusions and quantitative reverse-transcription polymerase chain reaction analyses to finely characterize the MtbHLH1 expression pattern. We altered MtbHLH1 function by expressing a dominantly repressed construct (CRES-T approach) and looked for possible MtbHLH1 target genes by transcriptomics. We found that MtbHLH1 is expressed in nodule primordia cells derived from pericycle divisions, in nodule vascular bundles (VBs) and in uninfected cells of the nitrogen (N) fixation zone. MtbHLH1 is also expressed in root tips, lateral root primordia cells and root VBs, and induced upon auxin treatment. Altering MtbHLH1 function led to an unusual phenotype, with a modified patterning of nodule VB development and a reduced growth of aerial parts of the plant, even though the nodules were able to fix atmospheric N. Several putative MtbHLH1 regulated genes were identified, including an asparagine synthase and a LOB (lateral organ boundary) transcription factor. Our results suggest that the MtbHLH1 gene is involved in the control of nodule vasculature patterning and nutrient exchanges between nodules and roots.

A systems biology representation of developmental anatomy

The formation of any tissue involves differentiation, cell dynamics and interactions with adjacent tissues. This paper suggests that the complexity of the system as a whole can be represented as a mathematical graph, that is, a set of connected triples of the general form [term] [term]. Computationally, such graphs are widely used for modeling data; visually, they form hierarchies and networks. For morphogenesis, the triples are of the general structure , where nouns cover tissues, molecules and networks and verbs describe processes such as moves, differentiates, grows and apoptoses. The paper considers the general formalism of graphs, where graphs are already used in biology, and how developmental anatomy may be described using this format. Representing morphogenesis as a visual graph is complicated as the formalism has to incorporate tissue types, molecular signals, networks, dynamic processes and some aspects, at least, of tissue geometry. The formation of a capillary sprout is chosen as an example of how this complexity can be represented graphically, with colour used to distinguish tissues and molecules. There are three key benefits, beyond its compactness, in using the graph formalism of morphogenesis to complement experimentation. First, it emphasizes the distributed nature of causality in morphogenesis. Secondly, producing all the triples for the visual graph requires explicit formalization of each aspect of the process, and this, in turn, often exposes gaps in knowledge and so suggests new experiments. Thirdly, once the graph has been formalized, triples can be annotated with associated information or IDs (e.g. cell types, publications, gene-expression data) that link to external online resources that may be regularly updated. Such annotations allow the graph to be viewed as a self-maintaining review. The graph approach sees dynamic processes as the drivers of developmental momentum and, because the same processes are used many times during development, it seems appropriate to view them as modules and their underlying networks as genomic subroutines.

Controlled release of chitosan/heparin nanoparticle-delivered VEGF enhances regeneration of decellularized tissue-engineered scaffolds

Regeneration deficiency is one of the main obstacles limiting the effectiveness of tissue-engineered scaffolds. To develop scaffolds that are capable of accelerating regeneration, we created a heparin/chitosan nanoparticle-immobilized decellularized bovine jugular vein scaffold to increase the loading capacity and allow for controlled release of vascular endothelial growth factor (VEGF). The vascularization of the scaffold was evaluated in vitro and in vivo. The functional nanoparticles were prepared by physical self-assembly with a diameter of 67–132 nm, positive charge, and a zeta potential of ∼30 mV and then the nanoparticles were successfully immobilized to the nanofibers of scaffolds by ethylcarbodiimide hydrochloride/hydroxysulfosuccinimide modification. The scaffolds immobilized with heparin/chitosan nanoparticles exhibited highly effective localization and sustained release of VEGF for several weeks in vitro. This modified scaffold significantly stimulated endothelial cells’ proliferation in vitro. Importantly, utilization of heparin/chitosan nanoparticles to localize VEGF significantly increased fibroblast infiltration, extracellular matrix production, and accelerated vascularization in mouse subcutaneous implantation model in vivo. This study provided a novel and promising system for accelerated regeneration of tissue-engineering scaffolds.

Intravital microscopy in the mouse dorsal chamber model for the study of solid tumors

Intra-Vital Microscopy (IVM) is used to visualize tumors in animals and analyze various aspects of cancer physiology such as tumor vascularization, cell migration and metastasis. The main advantages of IVM include the real -time analysis of dynamic processes with single-cell resolution. The application of IVM, however, is limited by the availability of animal models that carry visually accessible tumors. These models have evolved over time to become more and more relevant to human tumors. The latest step is the development of a pseudo-orthotopic, syngeneic model for tumor growth and metastasis. In this model, tissue from a variety of mouse organs are grafted in a dorsal skinfold chamber and allowed to revascularize, whereupon tumor cell spheroids are implanted. These spheroids develop into tumors that bear a much closer resemblance to human tumors than xenografts. Unlike xenografts, the vasculature is well-ordered and, because the model is syngeneic, there are no cross-species host immune reactions. The use of fluorescence-tagged pseudo-organs and tumor cells allows IVM analysis and provides real-time access to the development of tumors that closely resemble the real disease. This model can be used to test therapeutics and to image tumor development and stroma-tumor interactions.

Cell interactions in bone tissue engineering

Bone fractures, where the innate regenerative bone response is compromised, represent between 4 and 8 hundred thousands of the total fracture cases, just in the United States. Bone tissue engineering (TE) brought the notion that, in cases such as those, it was preferable to boost the healing process of bone tissue instead of just adding artificial parts that could never properly replace the native tissue. However, despite the hype, bone TE so far could not live up to its promises and new bottom-up approaches are needed. The study of the cellular interactions between the cells relevant for bone biology can be of essential importance to that. In living bone, cells are in a context where communication with adjacent cells is almost permanent. Many fundamental works have been addressing these communications nonetheless, in a bone TE approach, the 3D perspective, being part of the microenvironment of a bone cell, is as crucial. Works combining the study of cell-to-cell interactions in a 3D environment are not as many as expected. Therefore, the bone TE field should not only gain knowledge from the field of fundamental Biology but also contribute for further understanding the biology of bone. In this review, a summary of the main works in the field of bone TE, aiming at studying cellular interactions in a 3D environment, and how they contributed towards the development of a functional engineered bone tissue, is presented.

In vivo imaging demonstrates a time-line for new vessel formation in islet transplantation

Vascularization of transplanted islets must be maintained to provide long-term graft function. In vivo assessment of new vessel formation in islet grafts has been poorly documented. The purpose of this study was to investigate whether neovascularization was detectable in vivo in a Feridex-labeled murine syngeneic subcapsular islet mass using DCE MRI over 180 days. Subcapsular transplants could be visualized at post-transplant days three, seven, 14, and 28 using T2-weighted MRI and at post-transplant day 180 by immunohistochemistry. Injection of the contrast agent gadolinium (Gd)-DTPA for DCE at three, seven, and 14 days showed increased signal in the transplant area consistent with new vessel formation. Areas under contrast enhancement curves suggested peak angiogenesis at 14 days. At 180 days, there was no observable change in signal intensity after contrast injection suggesting established vascularization or islet mass reduction. Immunohistochemistry confirmed MRI and DCE findings. These data suggest that islet angiogenesis occurs early after transplantation and is likely established after one month of transplantation. This study provides an in vivo time-line of neovascularization in subcapsular islet grafts. We anticipate that contrast extravasation captured by MRI may provide useful monitoring of graft angiogenesis if reproduced in a clinically relevant intraportal model.

Exogenous expression of caspase-14 induces tumor suppression in human salivary cancer cells by inhibiting tumor vascularization

BACKGROUND

Current therapeutic approaches to salivary gland cancer are often associated with severe disfigurement and loss of glandular function, which are traumatic to the patients. Exploration of novel treatment approaches, such as gene therapy, is needed.

MATERIALS AND METHODS

The human salivary gland cancer cell line HSG was transiently transfected with full length human caspase-14 cDNA. Photomicroscopy, BrdU assay, cell counting, MTT assay, and TUNEL assay were applied. To determine the tumorigenicity, tumor volume, tumor pathology and vascularization were analyzed in vivo.

RESULTS

Cell growth and viability were inhibited significantly by transient caspase-14 expression. Caspase-14 expression resulted in a significant reduction of tumorigenicity. Importantly, a significant decrease in tumor blood vessel formation was observed.

CONCLUSION

Salivary gland cancer cells underwent growth inhibition, cell death, and reduced tumorigenicity in vivo when exogenous caspase-14 was expressed, which could be due, in part, to an inhibitory effect of caspase-14 on tumor vascularization.

The pro-apoptotic substance thapsigargin selectively stimulates re-growth of brain capillaries

Thapsigargin is a pro-apoptotic chemical, which has been shown to be useful to study cell death of cholinergic or dopaminergic neurons, or cells, which degenerate in Alzheimer's disease or Parkinson's disease, respectively. The aim of the present work was to study the effects of thapsigargin in the well established organotypic brain co-slice model composed of the basal nucleus of Meynert (nBM), ventral mesencephalon (vMes), dorsal striatum (dStr) and parietal cortex (Ctx). Cholinergic acetyltransferase-positive neurons in the nBM and dStr and dopaminergic tyrosine hydroxylase-positive neurons in the vMes survived, when cultured for 4 weeks with nerve growth factor and glial cell line-derived neurotrophic factor. Nerve fibers of cholinergic nBM neurons grew into the cortex and dopaminergic nerve fibers sprouted into dopamine D2 receptor-positive dStr. The whole co-slice contained a dense laminin-positive capillary network. Treatment of co-cultures with 3 microM thapsigargin for 24 hr significantly decreased the number of cholinergic neurons and dopaminergic neurons. This cell death displayed apoptotic DAPI-positive malformed nuclei and enhanced TUNEL-positive cells. Thapsigargin selectively stimulated the laminin-positive capillary growth between the nBM and Ctx. In conclusion, the induced cell death of cholinergic and dopaminergic neurons may be accompanied by enhanced angiogenic activity.

The Allantoic Core Domain: new insights into development of the murine allantois and its relation to the primitive streak

The whereabouts and properties of the posterior end of the primitive streak have not been identified in any species. In the mouse, the streak's posterior terminus is assumed to be confined to the embryonic compartment, and to give rise to the allantois, which links the embryo to its mother during pregnancy. In this study, we have refined our understanding of the biology of the murine posterior primitive streak and its relation to the allantois. Through a combination of immunostaining and morphology, we demonstrate that the primitive streak spans the posterior extraembryonic and embryonic regions at the onset of the neural plate stage ( approximately 7.0 days postcoitum, dpc). Several hours later, the allantoic bud emerges from the extraembryonic component of the primitive streak (XPS). Then, possibly in collaboration with overlying allantois-associated extraembryonic visceral endoderm, the XPS establishes a germinal center within the allantois, named here the Allantoic Core Domain (ACD). Microsurgical removal of the ACD beyond headfold (HF) stages resulted in the formation of allantoic regenerates that lacked the ACD and failed to elongate; nevertheless, vasculogenesis and vascular patterning proceeded. In situ and transplantation fate mapping demonstrated that, from HF stages onward, the ACD's progenitor pool contributed to the allantois exclusive of the proximal flanks. By contrast, the posterior intraembryonic primitive streak (IPS) provided the flanks. Grafting the ACD into T(C)/T(C) hosts, whose allantoises are significantly foreshortened, restored allantoic elongation. These results revealed that the ACD is essential for allantoic elongation, but the cues required for vascularization lie outside of it. On the basis of these and previous findings, we conclude that the posterior primitive streak of the mouse conceptus is far more complex than was previously believed. Our results provide new directives for addressing the origin and development of the umbilical cord, and establish a novel paradigm for investigating the fetal/placental relationship.

Sorafenib inhibits tumor growth and vascularization of rhabdomyosarcoma cells by blocking IGF-1R-mediated signaling

The growth of many soft tissue sarcomas is dependent on aberrant growth factor signaling, which promotes their proliferation and motility. With this in mind, we evaluated the effect of sorafenib, a receptor tyrosine kinase inhibitor, on cell growth and apoptosis in sarcoma cell lines of various histological subtypes. We found that sorafenib effectively inhibited cell proliferation in rhabdomyosarcoma, synovial sarcoma and Ewing’s sarcoma with IC₅₀ values <5 μM. Sorafenib effectively induced growth arrest in rhabdomyosarcoma cells, which was concurrent with inhibition of Akt and Erk signaling. Studies of ligand-induced phosphorylation of Erk and Akt in rhabdomyosarcoma cells showed that insulin-like growth factor-1 is a potent activator, which can be blocked by treatment with sorafenib. In vivo sorafenib treatment of rhabdomyosarcoma xenografts had a significant inhibitory effect on tumor growth, which was associated with inhibited vascularization and enhanced necrosis in the adjacent tumor stroma. Our results demonstrate that in vitro and in vivo growth of rhabdomyosarcoma can be suppressed by treatment with sorafenib, and suggests the possibilities of using sorafenib as a potential adjuvant therapy for the treatment of rhabdomyosarcoma.

Effect of age on vascularization during fracture repair

Age affects fracture repair; however, the underlying mechanisms are not well understood. The goal of this study was to assess the effects that age has on vascularization during fracture healing. Tibial fractures were created in juvenile (4-week-old), middle-aged (6-month-old), and elderly (18-month-old) mice. The length density and surface density of blood vessels within fracture calluses were analyzed using stereology at 7 days after fracture. The expression of molecules that regulate vascular invasion of the fracture callus was also compared among the three age groups by immunohistochemistry and in situ hybridization. At 7 days after fracture, juvenile mice had a higher surface density of blood vessels compared to the middle-aged and elderly. Hypoxia-inducible factor-1 alpha protein and transcripts of vascular endothelial growth factor were detected at 3 days postinjury in juvenile but not middle-aged and elderly mice. Stronger Mmp-9 and -13 expression was detected in fracture calluses at day 7 in the juvenile compared to the middle-aged and elderly mice. At 21 days postfracture, expression of both Mmps was more robust in the elderly than juvenile and middle-aged animals. These data indicate that age affects vascularization during fracture repair, and the changes we observed are directly correlated with altered expression of biochemical factors that regulate the process of angiogenesis. However, whether the increased vascularization is the cause or result of accelerated bone repair in juvenile animals remains unknown. Nonetheless, our results indicate that enhancing vascularization during fracture repair in the elderly may provide unique therapeutic opportunities.

Spatial and temporal patterns of bone formation in ectopically pre-fabricated, autologous cell-based engineered bone flaps in rabbits

Biological substitutes for autologous bone flaps could be generated by combining flap pre-fabrication and bone tissue engineering concepts. Here, we investigated the pattern of neotissue formation within large pre-fabricated engineered bone flaps in rabbits. Bone marrow stromal cells from 12 New Zealand White rabbits were expanded and uniformly seeded in porous hydroxyapatite scaffolds (tapered cylinders, 10-20 mm diameter, 30 mm height) using a perfusion bioreactor. Autologous cell-scaffold constructs were wrapped in a panniculus carnosus flap, covered by a semipermeable membrane and ectopically implanted. Histological analysis, substantiated by magnetic resonance imaging (MRI) and micro-computerized tomography scans, indicated three distinct zones: an outer one, including bone tissue; a middle zone, formed by fibrous connective tissue; and a central zone, essentially necrotic. The depths of connective tissue and of bone ingrowth were consistent at different construct diameters and significantly increased from respectively 3.1+/-0.7 mm and 1.0+/-0.4 mm at 8 weeks to 3.7+/-0.6 mm and 1.4+/-0.6 mm at 12 weeks. Bone formation was found at a maximum depth of 1.8 mm after 12 weeks. Our findings indicate the feasibility of ectopic pre-fabrication of large cell-based engineered bone flaps and prompt for the implementation of strategies to improve construct vascularization, in order to possibly accelerate bone formation towards the core of the grafts.

Effects of visual experience on vascular endothelial growth factor expression during the postnatal development of the rat visual cortex

The development of the cortical vascular network depends on functional maturation. External inputs are an essential requirement in the modeling of the visual cortex, mainly during the critical period, when the functional and structural properties of visual cortical neurons are particularly susceptible to alterations. Vascular endothelial growth factor (VEGF) is the major angiogenic factor, a key signal in the induction of vessel growth. Our study focused on the role of visual stimuli on the development of the vascular pattern correlated with VEGF levels. Vascular density and the expression of VEGF were examined in the primary visual cortex of rats reared under different visual environments (dark rearing, dark-rearing in conditions of enriched environment, enriched environment, and laboratory standard conditions) during postnatal development (before, during, and after the critical period). Our results show a restricted VEGF cellular expression to astroglial cells. Quantitative differences appeared during the critical period: higher vascular density and VEGF protein levels were found in the enriched environment group; both dark-reared groups showed lower vascular density and VEGF levels, which means that enriched environment without the physical exercise component does not exert effects in dark-reared rats.

Placental villous vascular endothelial growth factor expression and vascularization after estrogen suppression during the last two-thirds of baboon pregnancy

We have recently shown that placental cytotrophoblast vascular endothelial growth factor (VEGF) expression and vessel density were increased by elevating estrogen and decreased by suppressing estrogen in early baboon pregnancy. The present study determined whether the elevation in estrogen which occurs in the last two-thirds of baboon pregnancy also has a role in the regulation of placental villous VEGF expression and angiogenesis. Placentas were obtained on day 170 of gestation (term, 184 days) from baboons untreated or treated with the aromatase inhibitor CGS 20267 or CGS 20267 plus estradiol daily on days 30-169. Serum estradiol levels in CGS 20267-treated baboons were decreased (P < 0.001) by 95%, however, placental cytotrophoblast VEGF mRNA levels (means +/- SE, attomoles/microg RNA) were similar in untreated (25,807 +/- 5,873), CGS 20267-treated (23,900 +/- 1,940) and CGS 20267 plus estradiol-treated (26,885 +/- 2,569) baboons. VEGF mRNA levels in the syncytiotrophoblast (2,008 +/- 405) and inner villous stromal cell (1,724 +/- 287) fractions of untreated baboons also were not altered by CGS 20267. However, whole villous VEGF mRNA levels in CGS 20267-treated baboons (18,590 +/- 2,315) were 4-fold greater (P < 0.001) than in untreated animals and restored to normal by estradiol. Percent vascularized area (15.88 +/- 0.88%) and vessel density (1,375 +/- 71/mm(2)) of the villous placenta in untreated animals were not altered by estrogen deprivation. We propose that villous cytotrophoblasts lose their responsivity to estrogen and that placental villous cytotrophoblast VEGF expression and angiogenesis are regulated by estrogen in a cell- and gestational age-specific manner, and that factors other than estrogen maintain VEGF expression in the last two-thirds of pregnancy.

Tissue engineering of bone: the reconstructive surgeon's point of view

Bone defects represent a medical and socioeconomic challenge. Different types of biomaterials are applied for reconstructive indications and receive rising interest. However, autologous bone grafts are still considered as the gold standard for reconstruction of extended bone defects. The generation of bioartificial bone tissues may help to overcome the problems related to donor site morbidity and size limitations. Tissue engineering is, according to its historic definition, an "interdisciplinary field that applies the principles of engineering and the life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function". It is based on the understanding of tissue formation and regeneration and aims to rather grow new functional tissues than to build new spare parts. While reconstruction of small to moderate sized bone defects using engineered bone tissues is technically feasible, and some of the currently developed concepts may represent alternatives to autologous bone grafts for certain clinical conditions, the reconstruction of large-volume defects remains challenging. Therefore vascularization concepts gain on interest and the combination of tissue engineering approaches with flap prefabrication techniques may eventually allow application of bone-tissue substitutes grown in vivo with the advantage of minimal donor site morbidity as compared to conventional vascularized bone grafts. The scope of this review is the introduction of basic principles and different components of engineered bioartificial bone tissues with a strong focus on clinical applications in reconstructive surgery. Concepts for the induction of axial vascularization in engineered bone tissues as well as potential clinical applications are discussed in detail.

Vascularized thymic lobe transplantation in miniature swine: thymopoiesis and tolerance induction across fully MHC-mismatched barriers

As the major site of self-nonself discrimination in the immune system, the thymus, if successfully transplanted, could potentially carry with it the induction of central tolerance to any other organ or tissue from the same donor. We have recently developed a technique for transplantation of an intact, vascularized thymic lobe (VTL) in miniature swine. In the present study, we have examined the ability of such VTL allografts to support thymopoiesis and induce transplantation tolerance across fully MHC-mismatched barriers. Six miniature swine recipients received fully MHC-mismatched VTL grafts with a 12-day course of tacrolimus. Three of these recipients were thymectomized before transplantation and accepted their VTL allografts long-term, with evidence of normal thymopoiesis. In contrast, three euthymic recipients rejected their VTL allografts. Donor renal allografts, matched to the donor VTL grafts, were transplanted without immunosuppression into two of the three thymectomized recipients, and one of the three euthymic recipients. These renal allografts were accepted by thymectomized recipients, but rejected by the euthymic recipient in an accelerated fashion. This study thus demonstrates that successful transplantation of a vascularized thymus across a fully MHC-mismatched barrier induces tolerance in this preclinical, large-animal model. This procedure should enable studies on the role of the thymus in transplantation immunology as well as offer a potential strategy for tolerance induction in clinical transplantation.

Development of pharyngeal arch arteries in early mouse embryo

The formation and transformation of the pharyngeal arch arteries in the mouse embryo, from 8.5 to 13 days of gestation (DG), was observed using scanning electron microscopy of vascular casts and graphic reconstruction of 1-microm serial epoxy-resin sections. Late in 8.5-9DG (12 somites), the paired ventral aortae were connected to the dorsal aortae via a loop anterior to the foregut which we call the 'primitive aortic arch', as in the chick embryo. The primitive aortic arch extended cranio-caudally to be transformed into the primitive internal carotid artery, which in turn gave rise to the primitive maxillary artery and the arteries supplying the brain. The second pharyngeal arch artery (PAA) appeared late in 9-9.5DG (16-17 somites), and the ventral aorta bent dorsolaterally to form the first PAA anterior to the first pharyngeal pouch by early in 9.5-10DG (21-23 somites). The third PAA appeared early in 9.5-10DG (21-23 somites), the fourth late in 9.5-10DG (27-29 somites), and the sixth at 10DG (31-34 somites). By 10.5DG (35-39 somites), the first and second PAAs had been transformed into other arteries, and the third, fourth and sixth PAAs had developed well, though the PAA system still exhibited bilateral symmetry. By 13DG, the right sixth PAA had disappeared, and the remaining PAAs formed an aortic-arch system that was almost of the adult type.

FLOOZY of petunia is a flavin mono-oxygenase-like protein required for the specification of leaf and flower architecture

The mechanisms that determine the relative positions of floral organs, and thereby their numbers, is a poorly understood aspect of flower development. We isolated a petunia mutant, floozy (fzy), in which the formation of floral organ primordia in the outermost three floral whorls and one of the two bracts at the base of the flower is blocked at an early stage. In addition, fzy mutants fail to generate secondary veins in leaves and bracts and display a decreased apical dominance in the inflorescence. FZY encodes an enzyme with homology to flavin mono-oxygenases and appears to be the ortholog of YUCCA genes of Arabidopsis. FZY is expressed in young leafs and bracts and in developing flowers. In young floral meristems FZY is expressed in the center of the meristem dome and, later, expression becomes localized on the flanks of the initiating petal and stamen primordia and at several sites in maturing anthers and carpels. These findings indicate that FZY is involved in synthesizing a signaling compound that is required for floral organ initiation and specification of the vascularization pattern in leaves. Although fzy mutants contain normal auxin levels, ectopic expression of FZY results in excessive auxin accumulation, suggesting that the signaling compound is auxin.

Angiogenic switch occurs late in squamous cell carcinomas of human skin

Angiogenesis is a crucial event in carcinogenesis and its onset has been associated with premalignant tumour stages. In order to elucidate the significance of angiogenesis in different stages of epithelial skin tumours, we analysed the vessel density in ten normal skin samples, 14 actinic keratosis (AK), 12 hypertrophic AKs, and in nine early- and 16 late-stage squamous cell carcinomas (SCCs). Mean vascular density was quantitated by counting the number of CD 31-immunostained blood vessels and by morphometric assessment of stained vessel area by computer-assisted image analysis. The results from both methods were well correlated. Mean vascular density was similar in normal dermis and in AK, and only slightly elevated in hypertrophic AKs and early SCC stages (tumour thickness < 2 mm). Only late-stage SCCs infiltrating the subcutis exhibited a significant increase in vascularization. Vessel density was independent of tumour localization, degree of proliferation and inflammatory cell infiltration. Furthermore, tumour vascularization was not correlated with the expression of vascular endothelial growth factor, a major angiogenic factor, as revealed by in situ hybridization and immunohistochemistry. The restriction of enhanced vascularization to increased tumour thickness may be a major reason for the rather low metastatic spread of cutaneous SCCs.

Intravital fluorescence videomicroscopy to study tumor angiogenesis and microcirculation

Angiogenesis and microcirculation play a central role in growth and metastasis of human neoplasms, and, thus, represent a major target for novel treatment strategies. Mechanistic analysis of processes involved in tumor vascularization, however, requires sophisticated in vivo experimental models and techniques. Intravital microscopy allows direct assessment of tumor angiogenesis, microcirculation and overall perfusion. Its application to the study of tumor-induced neovascularization further provides information on molecular transport and delivery, intra- and extravascular cell-to-cell and cell-to-matrix interaction, as well as tumor oxygenation and metabolism. With the recent advances in the field of bioluminescence and fluorescent reporter genes, appropriate for in vivo imaging, the intravital fluorescent microscopic approach has to be considered a powerful tool to study microvascular, cellular and molecular mechanisms of tumor growth.

Inhibition of tumor growth, angiogenesis, and microcirculation by the novel Flk-1 inhibitor SU5416 as assessed by intravital multi-fluorescence videomicroscopy

Vascular endothelial growth factor (VEGF) plays a fundamental role in mediating tumor angiogenesis and tumor growth. Here we investigate the direct effect of a novel small molecule inhibitor of the Flk-1-mediated signal transduction pathway of VEGF, SU5416, on tumor angiogenesis and microhemodynamics of an experimental glioblastoma by using intravital multifluorescence videomicroscopy. SU5416 treatment significantly suppressed tumor growth. In parallel, SU5416 demonstrated a potent antiangiogenic activity, resulting in a significant reduction of both the total and functional vascular density of the tumor microvasculature, which indicates an impaired vascularization as well as significant perfusion failure in treated tumors. This malperfusion was not compensated for by changes in vessel diameter or recruitment of nonperfused vessels. Analyses of the tumor microcirculation revealed significant microhemodynamic changes after angiogenesis blockage such as a higher red blood cell velocity and blood flow in remnant tumor vessels when compared with controls. Our results demonstrate that the novel antiangiogenic concept of targeting the tyrosine kinase of Flk-1/KDR by means of a small molecule inhibitor represents an efficient strategy to control growth and progression of angiogenesis-dependent tumors. This study provides insight into microvascular consequences of Flk-1/KDR targeting in vivo and may have important implications for the future treatment of angiogenesis-dependent neoplasms.

Intrinsic control of vascularization in developing cartilage rudiments

The vascularization of developing cartilage rudiments is temporally and spatially defined. By using an in vivo angiogenesis model, the chorioallantoic membrane (CAM) of the chick embryo and chick embryo cartilage rudiments, we conclude that the factors controlling the vascular invasion of cartilage rudiments are intrinsic. Intact rudiments, separate hypertrophic zones and separate rounded cell zones, when grafted onto the CAM, become vascularized in the same temporal and spatial manner as occurs in ovo. When grown as organ cultures prior to CAM grafting, rudiments still become vascularized in the same temporal and spatial manner. The integrity of the extracellular matrix and the presence of the periosteum are two physical factors regulating the control of vascularization. Removal of the periosteum from hypertrophic regions caused a cessation of the invasion. Insults to the matrix via brief enzymatic degradation of extracellular matrix components resulted in invasion and erosion of rounded cell zones at an earlier time than is ordinarily seen both in ovo and on the CAM.

Parameters derived from integrated nuclear fluorescence, syntactic structure analysis, and vascularization in human lung carcinomas

Combined measurements of integrated nuclear fluorescence (INF) and vascularization were performed on surgical specimens of human lung carcinomas. Histological slides of formalin-fixed, paraffin-embedded tissue samples were treated with Texas Red-labeled antibody to factor VIII and the fluorochrome DAPI. The resulting images were analyzed with an epi-illumination fluorescence microscope and two different filter blocks. The first image displayed the vessels, and the second the DAPI-stained nuclei of surrounding cells. The extent of vascularization was assessed by calculating the volume fraction (Vv), the surface fraction (Sv), the area, and the minimum diameter of the vessels. The INF was measured in tumour cells and lymphocytes, and was grouped according to the distance from the nearest vascular boundary into the intervals of 0-20, 21-40, 41-60, 61-80, and > 80 mu. The numerical densities (Nv) as well as the percentages of S-phase-related tumour cell fraction (SPRF) and of tumour cells with an INF > 5C were computed. A minimum of 50 vessels and 300 tumour cells were examined. The material included 100 cases with primary lung carcinoma (39 epidermoid carcinomas, 39 adenocarcinomas, 13 large cell carcinomas, three small cell anaplastic carcinomas, and 6 carcinoid tumours). On the average, the volume density of the stroma amounts to 16.7%, and that of the vessels (Vv) to 12.8%. The minimum diameter of the intratumoral vessels is 13 mu and the measured circumference 138 mu. The numerical densities of tumour cells (lymphocytes) decrease with increasing distance from the vascular boundary from 6.3 (1.7) to 1.0 (0.1). A reduction is also seen in the percentage of the SPRF from 10.7 to 8.1%. The percentage of tumour cells with an INF > 5C, however, is positively correlated to the distance from the vascular surfaces from 34.2 to 38.2%. The measurements reveal that tumour cells are densely positioned and have an increased proportion of proliferation in the populations close to perivascular spaces, whereas chromosome abnormalities are seen more frequently, when tumour cells are located at a distance > 20 mu from the vascular surfaces.