Matrix metalloproteinases regulate ECM accumulation but not larval heart growth in Drosophila melanogaster.

The Drosophila heart provides a simple model to examine the remodelling of muscle insertions with growth, extracellular matrix (ECM) turnover, and fibrosis. Between hatching and pupation, the Drosophila heart increases in length five-fold. If major cardiac ECM components are secreted remotely, how is ECM "self assembly" regulated? We explored whether ECM proteases were required to maintain the morphology of a growing heart while the cardiac ECM expanded. An increase in expression of Drosophila's single tissue inhibitor of metalloproteinase (TIMP), or reduced function of metalloproteinase MMP2, resulted in fibrosis and ectopic deposition of two ECM Collagens; type-IV and fibrillar Pericardin. Significant accumulations of Collagen-IV (Viking) developed on the pericardium and in the lumen of the heart. Congenital defects in Pericardin deposition misdirected further assembly in the larva. Reduced metalloproteinase activity during growth also increased Pericardin fibre accumulation in ECM suspending the heart. Although MMP2 expression was required to remodel and position cardiomyocyte cell junctions, reduced MMP function did not impair expansion of the heart. A previous study revealed that MMP2 negatively regulates the size of the luminal cell surface in the embryonic heart. Cardiomyocytes align at the midline, but do not adhere to enclose a heart lumen in MMP2 mutant embryos. Nevertheless, these embryos hatch and produce viable larvae with bifurcated hearts, indicating a secondary pathway to lumen formation between ipsilateral cardiomyocytes. MMP-mediated remodelling of the ECM is required for organogenesis, and to prevent assembly of excess or ectopic ECM protein during growth. MMPs are not essential for normal growth of the Drosophila heart.

Optical coherence angiography for pre-treatment assessment and treatment monitoring following photodynamic therapy: a basal cell carcinoma patient study.

Microvascular networks of human basal cell carcinomas (BCC) and surrounding skin were assessed with optical coherence angiography (OCA) in conjunction with photodynamic therapy (PDT). OCA images were collected and analyzed in 31 lesions pre-treatment, and immediately/24 hours/3-12 months post-treatment. Pre-treatment OCA enabled differentiation between prevalent subtypes of BCC (nodular and superficial) and nodular-with-necrotic-core BCC subtypes with a diagnostic accuracy of 78%; this can facilitate more accurate biopsy reducing sampling error and better therapy regimen selection. Post-treatment OCA images at 24 hours were 98% predictive of eventual outcome. Additional findings highlight the importance of pre-treatment necrotic core, vascular metrics associated with hypertrophic scar formation, and early microvascular changes necessary in both tumorous and peri-tumorous regions to ensure treatment success.

An improved treatment planning and quality assurance process for Collaborative Ocular Melanoma Study eye plaque brachytherapy.

PURPOSE: To develop a treatment planning platform for episcleral Collaborative Ocular Melanoma Study plaque therapy in an established treatment planning software and to improve an existing quality assurance (QA) process for nonuniformly loaded plaques that measures air kerma strengths (AKSs) and loading profile. MATERIALS AND METHODS: Treatment planning is performed in Pinnacle using scripts that let the planner choose plaque size and notching. Scripts load seed positions for each plaque and five source groups corresponding to available stock seeds that can be placed into each seed position. Contours are loaded that display the model eye and the plaque itself. Plaque QA is performed using a modification of our previous pinhole apparatus by replacing x-ray film exposure with an optical camera and scintillating film system. The captured image is processed to remove background and to correct the intensity of seeds on the plaque periphery. Measured total optical counts provide an estimate of total plaque AKS. RESULTS: Treatment planning of eye plaques using Pinnacle, in conjunction with our stock inventory of seeds, is established as standard practice at our center. Planned plaques can vary from uniformly loaded to asymmetrically loaded notched plaques. Using the optical camera system for assessment of the seed loadings has decreased QA time from 40 min/plaque to 10 min/plaque. Total AKS of each plaque can be measured using the optical camera with an accuracy of 10%. CONCLUSIONS: Treatment planning is performed on a Health Canada-approved software that accommodates nonuniform plaque loading. Optical imaging of the plaque provides absolute total AKS and the relative seed arrangement in the plaque.

Accurate early prediction of tumour response to PDT using optical coherence angiography.

Prediction of tumour treatment response may play a crucial role in therapy selection and optimization of its delivery parameters. Here we use optical coherence angiography (OCA) as a minimally-invasive, label-free, real-time bioimaging method to visualize normal and pathological perfused vessels and monitor treatment response following vascular-targeted photodynamic therapy (PDT). Preclinical results are reported in a convenient experimental model (CT-26 colon tumour inoculated in murine ear), enabling controlled PDT and post-treatment OCA monitoring. To accurately predict long-term treatment outcome, a robust and simple microvascular metric is proposed. It is based on perfused vessels density (PVD) at t = 24 hours post PDT, calculated for both tumour and peri-tumour regions. Histological validation in the examined experimental cohort (n = 31 animals) enabled further insight into the excellent predictive power of the derived early-response OCA microvascular metric. The results underscore the key role of peri-tumour microvasculature in determining the long-term PDT response.

In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography.

Mucositis is the limiting toxicity of radio(chemo)therapy of head and neck cancer. Diagnostics, prophylaxis and correction of this condition demand new accurate and objective approaches. Here we report on an in vivo longitudinal monitoring of the oral mucosa dynamics in 25 patients during the course of radiotherapy of oropharyngeal and nasopharyngeal cancer using multifunctional optical coherence tomography (OCT). A spectral domain OCT system with a specially-designed oral imaging probe was used. Microvasculature visualization was based on temporal speckle variations of the full complex signal evaluated by high-pass filtering of 3D data along the slow scan axis. Angiographic image quantification demonstrated an increase of the vascular density and total length of capillary-like-vessels before visual signs or clinical symptoms of mucositis occur. Especially significant microvascular changes compared to their initial levels occurred when grade two and three mucositis developed. Further, microvascular reaction was seen to be dose-level dependent. OCT monitoring in radiotherapy offers a non-invasive, convenient, label-free quantifiable structural and functional volumetric imaging method suitable for longitudinal human patient studies, furnishing fundamental radiobiological insights and potentially providing useful feedback data to enable adaptive radiotherapy (ART).

Photodynamic therapy monitoring with optical coherence angiography.

Photodynamic therapy (PDT) is a promising modern approach for cancer therapy with low normal tissue toxicity. This study was focused on a vascular-targeting Chlorine E6 mediated PDT. A new angiographic imaging approach known as M-mode-like optical coherence angiography (MML-OCA) was able to sensitively detect PDT-induced microvascular alterations in the mouse ear tumour model CT26. Histological analysis showed that the main mechanisms of vascular PDT was thrombosis of blood vessels and hemorrhage, which agrees with angiographic imaging by MML-OCA. Relationship between MML-OCA-detected early microvascular damage post PDT (within 24 hours) and tumour regression/regrowth was confirmed by histology. The advantages of MML-OCA such as direct image acquisition, fast processing, robust and affordable system opto-electronics, and label-free high contrast 3D visualization of the microvasculature suggest attractive possibilities of this method in practical clinical monitoring of cancer therapies with microvascular involvement.

In vivo real time monitoring of vasoconstriction and vasodilation by a combined diffuse reflectance spectroscopy and Doppler optical coherence tomography approach.

BACKGROUND AND OBJECTIVES: A combined diffuse reflectance (DR) spectroscopy and doppler optical coherence tomography (DOCT) approach may offer a powerful means for assessment of tissue function, and potentially provide a way for earlier cancer detection through non-invasive local blood supply measurements. The goal of the study was to compare a DR-derived blood-content-related index to a measure of local blood supply flow as furnished by DOCT during manipulations with blood circulation (vasoconstriction and vasodilation), investigate similarities and differences, complementarity of techniques, and then applying these results to the underlying biology. STUDY DESIGN/MATERIALS AND METHODS: Simultaneous DR-DOCT measurements of local blood supply were conducted during drug and mechanically-induced vasoconstriction and vasodilatation on an externalized intact rat gut in vivo. A simple heuristic metric, termed Blood Supply Index was derived from the spectroscopic DR data. This metric variance due to mechanical and pharmacological manipulation of the local blood supply was recorded, and compared with that of two DOCT-derived metrics, namely normalized blood velocity (v(rel)) and blood vessel diameter (D). SUMMARY AND CONCLUSIONS: During vasoconstriction and vasodilatation, the local blood response was successfully visualized by both DOCT and DR metrics and a reproducible correlation was found between these two measurements. A combined DR-DOCT approach may evolve into a technologically-viable method for cross-validation of the derived haemodynamic metrics, yielding a more reliable functional tissue assessment tool for accurate cancer diagnosis and staging.

Study of photodynamic reactions in human blood.

Comparative studies of oxygen consumption, changes of photosensitizer fluorescence, and photodestruction of erythrocytes, and photodestruction of oxygen transport protein hemoglobin were performed during photodynamic reaction in whole and hemolyzed blood with phthalocyanines, chlorines, porphyrins, and methylene blue photosensitizers in vitro and in selected cases in vivo. The present work deals with the investigation of blood oxygen saturation SO2 and photosensitizer fluorescence during and immediately after light irradiation in the photodynamic therapy process. It has been observed that SO2 behavior strongly correlates with the type of photosensitizer. The decrease of photosensitizer fluorescence (photobleaching) during light irradiation can be followed by the recovery of the photosensitizer fluorescence immediately after interruption of the irradiation within 6-8 min. The levels of photodestruction of erythrocytes in whole blood and photodestruction of hemoglobin in hemolyzed blood in combination with the above photosensitizers reveal the influence of photodynamic reactions upon the ability of blood to transport oxygen. Maximal photohemolysis activity has been found with chlorine p6 photosensitizers.

Three-dimensional optical phantom and its application in photodynamic therapy.

BACKGROUND AND OBJECTIVE: A technique to manufacture a stable, reproducible three-dimensional optical phantom is presented. This phantom reproduces the tissue's optical properties as well as the geometry and, to some extent, the mechanical properties of the organ concerned. Easy to make and to handle, this phantom is a useful tool for numerous medical applications involving light interaction with biological tissues. STUDY DESIGN/MATERIALS AND METHODS: The phantom is based on a transparent two-component silicone, which is molded into the desired shape and cured at room temperature. Specific optical properties are obtained by adding scatterers (Al2O3 particles or polystyrene microspheres) and absorbers (dyes or pigments). A method to measure the radiant energy fluence rate in the phantom is described. This method is based on a small isotropic optical detector. RESULTS: A three-dimensional phantom of the bronchial tree is presented. This phantom is used for testing new light distributors designed for photodynamic therapy of the bronchi. CONCLUSION: The proposed technique allows one to produce a stable three-dimensional phantom with accurately predictable optical properties.