Combined photodynamic and photothermal induced injury enhances damage to in vivo model blood vessels.

BACKGROUND AND OBJECTIVES: The degree of port wine stain (PWS) blanching following pulsed dye laser (PDL) therapy remains variable and unpredictable. Because of the limitations of current PDL therapy, alternative treatment approaches should be explored. The objective was to evaluate a novel methodology for selective vascular damage, combined photodynamic (PDT) and photothermal (PDL) treatment, using the in vivo chick chorioallantoic membrane (CAM) model. STUDY DESIGN/MATERIALS AND METHODS: Thirty microliters of benzoporphyrin derivative monoacid ring A (BPD) solution was administered intraperitoneally into chick embryos at day 12 of development. Study groups were: (1) control (no BPD, no light); (2) BPD alone; (3) continuous wave irradiation (CW) alone (576 nm, 60 mW/cm2, 125 seconds); (4) CW + PDL; (5) BPD+PDL; (6) PDT (BPD+CW); (7) PDL alone (585 nm, 4 J/cm(2)); and (8) PDT+PDL (BPD + CW followed immediately by PDL). Vessels were videotaped prior to, and at 1 hour post-intervention and then assessed for damage based on the following scale: 0, no damage; 1, coagulation; 1.5, vasoconstriction; 2.0, coagulation+vasoconstriction; 2.5, angiostasis; 3.0, hemorrhage. Damage scores were weighted by vessel "order." RESULTS: PDT + PDL resulted in significantly (P < 0.01) more severe vascular damage than was observed in any other study group: 127% more than PDT, 47% more than PDL alone. CONCLUSIONS: PDT + PDL is a novel and promising approach for selective vascular damage and may offer a more effective method for treatment of PWS and other vascular skin lesions.

Effects of intraoperative hyperthermia on canine sciatic nerve: histopathologic and morphometric studies.

Failure to achieve local control in the treatment of pelvic and retroperitoneal tumours results in a high rate of recurrences. The objective of intraoperative hyperthermia (IOHT) is to enhance the effect of intraoperative radiation therapy and to increase local tumour control. The tolerance of peripheral nerves to heat may limit the heat dose that can be applied to tumours. Histopathologic and histomorphometric changes of canine sciatic nerve after 60-min IOHT were studied in three groups of five dogs each for temperatures of 43, 44 and 45 degrees C. IOHT was performed using a water-circulating hyperthermia device with a multichannel thermometry system on surgically exposed sciatic nerve. Histopathologic and histomorphometric studies were done immediately, 3 weeks and 12 months after IOHT. Histologic changes observed immediately after treatment were minimal but at 3 weeks following 60-min 45 degrees C IOHT both axon and myelin loss and an increase in endoneurial fibrous tissue were observed. Twelve months after treatment a statistically significant decrease in axon, myelin and small vessel percentages as well as an increase in endoneurial and epineural connective tissue were observed for dog treated to 45 degrees C. Dog treated to 44 degrees C for 60 min had similar statistically significant but less severe changes. Twelve months after 43 degrees C IOHT for 60 min, nerve fibres appeared normal and endoneurial connective tissue was only increased mildly around small and medium-sized vessels. These results suggest that temperatures to the peripheral nerve > 44 degrees C for 60 min are likely to cause significant histopathologic changes that can be found 12 months after treatment. A hypothesis of the mechanism of heat injury to peripheral nerves was developed.

Endothelial cells and hyperthermia.

Most radiation oncologists are aware of the effects of clinical hyperthermia on neoplastic cells. Its effects on blood vessels, however, are not as well recognized. Yet, since the 1960s a number of investigators have described and categorized the effects of hyperthermia on microvessels (in vivo), and on cultured endothelial cells (EC) (in vitro). Both EC and microvessels can be lethally damaged by the hyperthermia doses used as antineoplastic therapy. In vitro data indicate that capillary EC are moderately sensitive to hyperthermia. Proliferating EC are more thermosensitive suggesting that microvessels of malignant neoplasms (which contain many proliferating EC) are more affected than microvessels of normal tissues. This differential sensitivity of microvessels has also been observed in blood flow studies. Furthermore, hyperthermia inhibits angiogenesis. Thus, some of the antineoplastic effects of heat are caused by ischaemia due to obstruction or destruction of the tumour vessels or to inability to form new vessels. Sublethal EC damage can also be demonstrated, resulting in decreased synthesis of most proteins including adhesion molecules (as well as increased expression of a few such as heat shock proteins) and producing reversible loss of cytoskeletal elements. The therapeutic advantage provided by the higher thermal sensitivity of neoplastic vessels should be exploited further, perhaps by developing strategies specifically aimed to the tumour microvasculature.

Differential thermal sensitivity of tumour and normal tissue microvascular response during hyperthermia.

The goal of this study was to investigate the heat sensitivity of the microcirculation in normal C3H murine leg muscle and a variety of transplanted tumour lines (KHT, SCC-VII, RIF-1, C3H mouse mammary carcinoma, two human mammary carcinomas MDA-468 and S5). Clearance rate of a radioactive tracer monitored following an intra-tissue injection was used as a measurement of microvascular integrity during heat treatment. Clearance rate in all tumours studied was significantly lower after 1 h of heating at 44 degrees C than the initial pretreatment clearance rate. Response of normal muscle differed from that of tumours in that the clearance rate after 1 h of heating at 44 degrees C was similar to the initial clearance rate. Vasculature in the KHT fibrosarcoma was more sensitive to heat treatment than that in other tumours. In response to a heat treatment at 43, 44, 45 and 46 degrees C the same level of microvascular damage occurred in half the time in KHT fibrosarcoma than in normal muscle. Furthermore, vascular damage in both muscle and KHT tumour followed the same relative isoeffect relationship, a 1 degree C change in temperature was equivalent to a change in heating time by a factor of two.

Activated neutrophils increase microvascular permeability in skeletal muscle: role of xanthine oxidase.

To determine the role of xanthine oxidase in the microvascular dysfunction produced by activated granulocytes, we examined the effect of xanthine oxidase depletion or inhibition on the increase in microvascular permeability produced by infusion of the neutrophil activator phorbol myristate acetate (PMA). Changes in vascular permeability were assessed by measurement of the solvent drag reflection coefficient for total plasma proteins (sigma) in rat hindquarters subjected to PMA infusion in xanthine oxidase-replete and -depleted animals, in animals pretreated with the xanthine oxidase inhibitor oxypurinol, and in animals depleted of circulating neutrophils by pretreatment with antineutrophil serum (ANS). Xanthine oxidase depletion was accomplished by administration of a tungsten-supplemented (0.7 g/kg diet) molybdenum-deficient diet. In animals fed the tungsten diet, muscle total xanthine dehydrogenase plus xanthine oxidase activity was decreased to less than 10% of control values. Estimates of sigma averaged 0.84 +/- 0.04 in control hindquarters, whereas PMA infusion was associated with a marked increase in microvascular permeability (decrease in sigma to 0.68 +/- 0.03). PMA infusion also caused an increase in the amount of the radical-producing oxidase form of xanthine oxidase (from 3.9 +/- 0.05 to 5.6 +/- 0.4 mU/g wet wt). ANS pretreatment attenuated this permeability increase (sigma = 0.77 +/- 0.04) and diminished the rise in xanthine oxidase activity (4.9 +/- 0.5 mU/g wet wt). Xanthine oxidase depletion with the tungsten diet or pretreatment with oxypurinol had no effect on this neutrophil-mediated microvascular injury (sigma = 0.69 +/- 0.06 and 0.67 +/- 0.03, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)