Morphologic characterization of osteosarcoma growth on the chick chorioallantoic membrane

Angiogenic efficacy of Heparin on chick chorioallantoic membrane

Heparin is an anticoagulant agent known to have diverse effects on angiogenesis with some reports suggesting that it can induce angiogenesis while a few have indicated of its inhibitory property. Cancer patients treated for venous thromboembolism with low molecular heparin had a better survival than the unfractionated heparin (UFH). Heparin is known to interact with various angiogenic growth factors based on its sulfation modifications within the glycosaminoglycan chains. Therefore it is important to study the mechanism of action of heparin of different molecular weight to understand its angiogenic property. In this concern, we examined the angiogenic response of higher molecular weight Heparin (15 kDa) of different concentrations using late CAM assay. Growth of blood vessels in terms of their length and size was measured and thickness of the CAM was calculated morphometrically. The observed increase in the thickness of the CAM is suggestive of the formation of capillary like structures at the treated region. Analysis of the diffusion pattern showed internalized action of heparin that could affect gene expression leading to proliferation of endothelial cells. Angiogenesis refers to formation of new blood vessels from the existing ones and occurrence of new blood vessels at the treated area strongly confirms that heparin of 15 kDa molecular weight has the ability to induce angiogenesis on CAM vascular bed in a dose dependent manner. The results demonstrate the affinity of heparin to induce angiogenesis and provide a novel mechanism by which heparin could be used in therapeutics such as in wound healing process.

A short-term in vivo model for giant cell tumor of bone

Background

Because of the lack of suitable in vivo models of giant cell tumor of bone (GCT), little is known about its underlying fundamental pro-tumoral events, such as tumor growth, invasion, angiogenesis and metastasis. There is no existing cell line that contains all the cell and tissue tumor components of GCT and thus in vitro testing of anti-tumor agents on GCT is not possible. In this study we have characterized a new method of growing a GCT tumor on a chick chorio-allantoic membrane (CAM) for this purpose.

Methods

Fresh tumor tissue was obtained from 10 patients and homogenized. The suspension was grafted onto the CAM at day 10 of development. The growth process was monitored by daily observation and photo documentation using in vivo biomicroscopy. After 6 days, samples were fixed and further analyzed using standard histology (hematoxylin and eosin stains), Ki67 staining and fluorescence in situ hybridization (FISH).

Results

The suspension of all 10 patients formed solid tumors when grafted on the CAM. In vivo microscopy and standard histology revealed a rich vascularization of the tumors. The tumors were composed of the typical components of GCT, including (CD51+/CD68+) multinucleated giant cells whichwere generally less numerous and contained fewer nuclei than in the original tumors. Ki67 staining revealed a very low proliferation rate. The FISH demonstrated that the tumors were composed of human cells interspersed with chick-derived capillaries.

Conclusions

A reliable protocol for grafting of human GCT onto the chick chorio-allantoic membrane is established. This is the first in vivo model for giant cell tumors of bone which opens new perspectives to study this disease and to test new therapeutical agents.

In vitro imaging of angiogenesis using embryonic stem cell-derived endothelial cells

Angiogenesis is an important event during developmental processes, and it plays a key role in neovascularization. The development of an in vitro model that can be used for live imaging of vessel growth will facilitate the study of molecular and cellular mechanisms for the growth of blood vessels. Embryonic stem cells (ESCs) are considered to be a novel renewable source for the derivation of genetically manipulable endothelial cells (ECs). To derive green fluorescence protein (GFP)-expressing ECs, we used a transgenic ESC line in which a GFP reporter was driven by the endothelial-specific promoter fetal liver kinase 1. ESC-ECs were isolated from 11-day embryoid bodies by fluorescence-activated cell sorting. Embedding the aggregated ESC-ECs in a 3-dimensional collagen gel matrix resulted in ESC-EC migration out of the aggregates and coalescence into a capillary network. Time-lapse microscopy revealed EC migration, proliferation, lumen formation, and anastomosis to other capillary vessels during this process, which were reminiscent of angiogenic processes. Vascular endothelial growth factor plays major roles in the induction of ESC-EC angiogenesis in vitro. Blockage of the β1 integrin subunit severely impaired ESC-EC survival and migration. We demonstrate that our in vitro ESC-EC angiogenesis model represents a high-resolution dynamic video-image system for observing the cellular events underlying angiogenic cascades. We also consider this model as an image screening tool for the identification of pro-angiogenic and anti-angiogenic molecules.

E2F1 regulates cellular growth by mTORC1 signaling

During cell proliferation, growth must occur to maintain homeostatic cell size. Here we show that E2F1 is capable of inducing growth by regulating mTORC1 activity. The activation of cell growth and mTORC1 by E2F1 is dependent on both E2F1's ability to bind DNA and to regulate gene transcription, demonstrating that a gene induction expression program is required in this process. Unlike E2F1, E2F3 is unable to activate mTORC1, suggesting that growth activity could be restricted to individual E2F members. The effect of E2F1 on the activation of mTORC1 does not depend on Akt. Furthermore, over-expression of TSC2 does not interfere with the effect of E2F1, indicating that the E2F1-induced signal pathway can compensate for the inhibitory effect of TSC2 on Rheb. Immunolocalization studies demonstrate that E2F1 induces the translocation of mTORC1 to the late endosome vesicles, in a mechanism dependent of leucine. E2F1 and leucine, or insulin, together affect the activation of S6K stronger than alone suggesting that they are complementary in activating the signal pathway. From these studies, E2F1 emerges as a key protein that integrates cell division and growth, both of which are essential for cell proliferation.