Quantitative histological changes in murine tail skin following photodynamic therapy

Abstract

Summary Mice were treated by an intravenous injection of 2 mg of the photosensitising drug meso-tetra (sulphonatophenyl) porphine (TPPS) and 24 h later a 2.5cm length of their tails was exposed to visible light (photodynamic therapy, PDT). Using cross-sections from the centre of the treatment field, the absolute areas occupied by epidermis, dermis, hypodermis, tendon and bone, and also the total number and area of the blood vessels in the dermis and hypodermis, were compared between control and PDT-treated animals. There was a significant increase in the mean cross-sectional area of the epidermis, dermis and hypodermis following both 90Jcm-2 (a dose expected to produce a low incidence of tail necrosis) and 180Jcm-2 (expected to produce a 100% tail necrosis rate), on day 1 and day 5 following light exposure. The cross-sectional area of the vascular compartment was also significantly increased by day 5 at both dose levels. Differences were observed between the two doses when the total number of blood vessels were compared. There was a significant increase in the number of blood vessels by day 5 following 90Jcm-2 in both the dermis and hypodermis, but not following 180JCcm-2. This appeared to be due to a significant increase in blood vessels with a cross-sectional area of <100 jIm2 by day 5 at the lower dose. It is concluded that angiogenesis-plays an important role in vascular recovery following PDT. There is increasing evidence that, in vivo, the vasculature both of tumours and normal tissues is promptly damaged by PDT. Castellani et al. (1963) (Bugelski et al., 1981). This has also been found to occur in normal tissue following PDT, by Zhou et al. (1985) in mouse skin, and by Berenbaum et al. (1986) in the brains of mice.Functional studies following PDT support these histological findings. Oxygen microelectrode measurements performed by Bicher et al. (1981) found a profound reduction in oxygen tension in a mouse mammary carcinoma within one hour of light exposure. Selman et al. (1985) demonstrated a significant decrease in blood flow to rat jejunum 10 min after PDT using a radioactive microscope technique. All these studies used HPD as the photosensitiser.Determination of blood flow in murine tail skin using the xenon clearance method, in animals treated with light 24h after exposure to the hydrophilic sensitiser TPPS, also revealed a significant decrease within 10min (Benstead & Moore, 1988a). We also observed recovery of blood flow between the first and fifth days after treatment with light doses below those that produced necrosis of the tail.Whether necrosis (defined here as complete loss of the tail distal to the proximal edge of the light beam) occurred in individual animals, following administration of a dose of PDT which produced a 50% incidence of necrosis, appeared to depend on the timing and degree of this recovery rather than the extent of the initial impairment of blood flow. The time course of this recovery also appeared to be important in determining the response of murine tail skin to a fract...

Radiographic assessment of photodynamic therapy as an adjunctive treatment on induced periodontitis in immunosuppressed rats

“…These results are in accordance with the literature, which has demonstrated PDT effectiveness in periodontal treatment for both animals 2 and humans 4 .…”

Treatment of experimental periodontal disease by photodynamic therapy in immunosuppressed rats

“…It was also evident in the present study that group D animals, which received PDT treatment, showed less bone loss compared with group ND animals, which received only SRP treatment, at 7‐ and 30‐day periods. The beneficial effects of PDT in the periodontal disease could be explained not only by the local anti‐microbial activity, described previously, but also by the increased angiogenesis that supplies more oxygenation to the area (Benstead & Moore 1989).…”

Clinical and immunohistochemical evaluation of psoriatic plaques treated with topical 5‐aminolaevulinic acid photodynamic therapy

“…The number of vessels visualized by the two different antibodies are not directly comparable as the staining was not performed on consecutive cryostat sections. A significantly increased number of blood vessels has previously been reported in the tails of mice 5 days after PDT using the photosensitizing drug mesotetra (sulphonatophenyl) porphine (TPSS) intravenously followed by exposure to visible light (16). This reaction was considered as a recovery phenomenon.…”