Three-dimensional ex vivo angiogenesis system
An in vitro tissue angiogenesis and vasculogenesis system is disclosed that allows the outgrowth of microvessels from a three-dimensional tissue fragment implanted in a matrix. The matrix may, for example, be a fibrin- or collagen-based matrix fed by a growth medium, for example, a mixture of tissue culture medium, serum, or a layer of growth medium containing a defined mixture of growth factors. This system, which may be used with human or other mammalian or animal tissues, may be used in assaying tumor angiogenic potential, or in promoting angiogenesis in other tissues, e.g., promoting angiogenesis prior to transplantation of a tissue. The angiogenic potential of a tissue can be determined by measuring the growth of microvessels into the matrix. The three-dimensional structure of the tumor or other tissue is maintained in the matrix, including blood vessels. In another aspect, the method allows for the proliferation of a tissue specimen, thus increasing the mass of cells available for subsequent transplant; and the method also provides for the proliferation of blood vessels from the tissue mass, thus enhancing the chance of successful engraftment.
1. A method for assaying the angiogenic potential of a particular tumor in a mammal; said method comprising the steps of:
(a) embedding a three-dimensional tissue sample in a matrix, wherein the tissue sample is taken from a particular tumor in a mammal; wherein the tissue sample has at least one cut surface exposing blood vessels; wherein the three-dimensional tissue sample comprises multiple layers of cells comprising blood vessels, supportive stromal elements, neural cells, and endothelial cells; wherein the architecture of the tissue sample is substantially intact and has not been disrupted as compared to that of comparable tissue in vivo; and wherein the three-dimensional tissue sample does not consist of an isolated artery or an isolated vein;
(b) supplying to the embedded tissue sample a medium that supports the growth of the tissue sample;
(c) incubating the embedded tissue sample in the medium for a time sufficient to allow any angiogenic vessels to grow into the matrix surrounding the tissue sample; and
(d) observing or measuring any angiogenic vessels that grow into the matrix surrounding the tissue sample;
whereby:
the growth or any angiogenic vessels into the matrix is a measure of the angiogenic potential of the particular tumor from which the tissue sample was taken.
2. A method as recited in claim 1 , wherein the medium comprises a serum-free medium that supports the growth of the tissue sample; wherein the medium contains substantially no exogenous angiogenesis-enhancing factors and substantially no exogenous angiogenesis-suppressing factors.
3. A method as recited in claim 1 , wherein the medium comprises serum.
4. A method as recited in claim 1 , wherein the medium comprises an angiogenesis-enhancing factor.
5. A method as recited in claim 4 , wherein the angiogenesis-enhancing factor is selected from the group consisting of platelet-derived growth factor, vascular endothelial growth factor, epidermal growth factor, fibroblast growth factor, and transforming growth factor β.
6. A method as recited in claim 1 , wherein the matrix comprises fibrin.
7. A method as recited in claim 1 , wherein the matrix comprises collagen.
8. A method as recited in claim 1 , wherein the matrix comprises gelatin.
9. A method as recited in claim 1 , wherein the matrix comprises agarose, agar, alginate, or silica gel.
10. A method as recited in claim 1 , wherein the matrix comprises Matrigel™ matrix.
11. A method as recited in claim 1 , additionally comprising the step of supplying a factor to the embedded tissue sample, and measuring the difference in angiogenesis for the tissue sample as compared to the angiogenesis of an otherwise identical and otherwise identically-treated control tissue sample that is not supplied with the factor; whereby the difference in observed angiogenesis is a measure of the angiogenic enhancement or angiogenic suppression characteristics of the supplied factor.
12. A method as recited in claim 1 , wherein said method additionally comprises the step of supplying an angiogenic suppression factor to the tissue sample, and measuring the difference in angiogenesis for the tissue sample as compared to the angiogenesis of an otherwise identical and otherwise identically-treated control tissue sample that is not supplied with the factor; whereby the measured difference in angiogenesis between the samples is a measure of the angiogenic suppression characteristics of the supplied factor against the tumor from which the sample was taken.
13. A method as recited in claim 1 , wherein said method additionally comprises the step of supplying an angiogenic stimulation factor to the embedded tissue sample, and measuring the difference in angiogenesis for the tissue sample as compared to the angiogenesis of an otherwise identical and otherwise identically-treated control tissue sample that is not supplied with the factor; whereby the measured difference in angiogenesis between the samples is a measure of the angiogenic stimulation characteristics of the supplied factor for the tissue from which the sample was taken.