Direct measurement of hypoxia in a xenograft multiple myeloma model by optical-resolution photoacoustic microscopy

Abstract

Using photoacoustic microscopy (PAM), we evaluated non-invasively oxygenation and vascularization in vivodue to multiple myeloma (MM) progression. Mice injected with MM.1S-GFP were monitored with a fluorescence microscope for tumor progression. In vivo PAM of the cerebral bone marrow quantified the total oxygen saturation (sO_2). At 28 days after the MM cell injection, the total sO_2 had decreased by half in the developing tumor regions, while in the non-tumor regions it had decreased by 20% compared with the value at one day post MM injection. The blood vessel density was reduced by 35% in the developing tumor regions, while in the non-tumor regions it was reduced by 8% compared with the value at one day post MM injection. Hence, PAM corroborated the development of hypoxia due to MM progression and demonstrated decreased vascularization surrounding the tumor areas.