Intravital high-resolution optical imaging of individual vessel response to photodynamic treatment

Abstract

Intravital imaging using confocal microscopy facilitates high-resolution studies of cellular and molecular events in vivo. We use this, complemented by Doppler optical coherence tomography (OCT), to assess blood flow in a mouse dorsal skin-fold window chamber model to image the response of individual blood vessels to localized photodynamic therapy (PDT). Specific fluorescent cell markers were used to assess the effect on the vascular endothelial cell lining of the treated vessels. A fluorescently tagged antibody against an endothelial transmembrane glycoprotein (CD31) was used to image endothelial cell integrity in the targeted blood vessel. A cell permeability (viability) indicator, SYTOX Orange, was also used to further assess damage to endothelial cells. A fluorescently labeled anti-CD41 antibody that binds to platelets was used to confirm platelet aggregation in the treated vessel. These optical techniques enable dynamic assessment of responses to PDT in vivo, at both the vascular endothelial cell and whole vessel levels.

Photodynamic therapy selectively enhances liposomal doxorubicin uptake in sarcoma tumors to rodent lungs

“…Non-invasive longitudinal real-time in vivo observations are required for monitoring blood flow, vascular responses, and the distribution of macromolecular therapeutics in various tumors and normal tissues after various PDT conditions. Intravital microscopy has been shown to be a valid instrument to observe PDT-mediated vascular effects and the egress of fluorescent macromolecules across the endothelial barrier over time in dorsal skin fold chambers [28,29]. Previous experiments have shown a complex interplay between photosensitization, blood flow characteristics, and leukocyte/thrombocyte-mediated extravasation of fluorescent microspheres [18].…”

Interstitial Doppler Optical Coherence Tomography as a Local Tumor Necrosis Predictor in Photodynamic Therapy of Prostatic Carcinoma: AnIn vivoStudy

“…This leaves the possibility of a transient vascular response occurring through the creation and dislodging of vascular thrombi (52) and/or a subnecrotic PDT-induced vascular response, as alluded to above. We plan to use the mouse window chamber model (53) to limit possible vascular artifacts from the IS probe, while obtaining direct visualization of the PDT-induced vascular response via DOCT. In addition to suggesting further scientific investigations of the underlying vascular mechanisms in PDT, it thus remains to be seen if IS-DOCT can be used as a stand-alone treatment monitoring/predictive outcome.…”

Longitudinal optical imaging of tumor metabolism and hemodynamics

“…Optical imaging based on endogenous tissue contrast does not require exogenous contrast agents, and is thus well suited for long-term monitoring of cycling hypoxia in tumors. Hyperspectral imaging of hemoglobin oxygen saturation [21][22][23] coupled with 3-D Doppler optical coherence tomography ͑OCT͒ of calibrated microvessel blood flow rates [24][25][26][27] allow for accurate, dynamic, and noninvasive imaging of oxygen supply in tumors. 28 Doppler OCT also allows for visualization of vessel velocity profiles at any vessel cross section in the tumor, thus providing information on the shear rate on the vessel wall.…”