RESUMEN
A method previously used in this laboratory for entrapment of tumor cells in alginate beads has been extended to provide a slow release delivery system for growth factors with known in vivo angiogenic activity. Protein growth factors were entrapped in alginate beads in amounts sufficient to cause incorporation of 3H-thymidine by COMMA-D cells in vitro, and in vivo neovascularization when injected subcutaneously into Balb/c mice. Entrapment of 125I-labelled growth factors showed that the amount of molecule entrapped in alginate beads may vary with the charge of the molecule. In vitro cell proliferation studies showed that entrapment in alginate beads may provide a slow-release system or a stabilizing environment for the protein. In some cases biological activity of the growth factor in solution was increased by the presence of control alginate beads. When alginate-entrapped growth factors were injected into Balb/c mice, induction of new blood vessels could be monitored qualitatively by macroscopic photography and assessed quantitatively by measuring the pooling of radiolabelled red blood cells at the experimental site. Subcutaneous injection of purified angiogenic factors not entrapped in alginate beads did not cause neovascularization. Diffusion of 125I-labelled growth factors from alginate beads in the animal showed that release in vivo may depend on the charge of the protein molecule. These results indicate that injection of purified molecules entrapped in alginate beads provides an effective localized and slow-release delivery of biologically active molecules. This delivery system may extend the time of effectiveness of biologically active molecules in vivo compared to direct injection without alginate entrapment. The method of entrapment and injection has potential for identifying active factors in tumor-induced angiogenesis and testing new compounds as modulators of neovascularization.
Asunto(s)
Inductores de la Angiogénesis/administración & dosificación , Factor de Crecimiento Epidérmico/administración & dosificación , Factor 1 de Crecimiento de Fibroblastos/administración & dosificación , Factor 2 de Crecimiento de Fibroblastos/administración & dosificación , Alginatos , Inductores de la Angiogénesis/farmacología , Animales , Línea Celular , Preparaciones de Acción Retardada , Difusión , Factor de Crecimiento Epidérmico/farmacología , Femenino , Factor 1 de Crecimiento de Fibroblastos/farmacología , Factor 2 de Crecimiento de Fibroblastos/farmacología , Ácido Glucurónico , Ácidos Hexurónicos , Ratones , Ratones Endogámicos BALB C , Microesferas , Piel/irrigación sanguínea , Timidina/metabolismoRESUMEN
An in vivo model of tumor-induced angiogenesis was used to monitor two known inhibitors of angiogenesis, protamine sulfate and the steroid tetrahydro S. Tumor cells entrapped in alginate beads were injected s.c. into mice. Blood vessel induction was measured by two quantitative methods: measurement of hemoglobin at the alginate pellet site, and pooling of radiolabeled RBC to the alginate pellet site. The two methods gave parallel results. Tetrahydro S with or without heparin inhibited blood vessel growth by 50%, and protamine sulfate inhibited blood vessel growth by 85%. These results were supported by gross morphology and histological analysis of the alginate pellet site.