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Quantitative histological changes in murine tail skin following photodynamic therapy
1Paterson Institute for Cancer Research, Christie Hospital and Holt Radium Institute, Manchester.
Abstract:
Mice were treated by an intravenous injection of 2 mg of the photosensitising drug meso-tetra (sulphonatophenyl) porphine (TPPS) and 24 h later a 2.5 cm 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 90J cm-2 (a dose expected to produce a low incidence of tail necrosis) and 180J cm-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 90 J cm-2 in both the dermis and hypodermis, but not following 180J cm-2. This appeared to be due to a significant increase in blood vessels with a cross-sectional area of less than 100 microns2 by day 5 at the lower dose. It is concluded that angiogenesis plays an important role in vascular recovery following PDT.
Insights
Photodynamic therapy (PDT) increases tissue and blood vessel size in mouse tails. Angiogenesis, or new blood vessel growth, is crucial for healing after PDT, especially at lower light doses.
Area of Science:
- Vascular Biology
- Tissue Regeneration
- Photodynamic Therapy
Background:
- Photodynamic therapy (PDT) utilizes photosensitizing agents and light to induce cell death.
- Understanding tissue and vascular responses to PDT is crucial for optimizing treatment outcomes.
Purpose of the Study:
- To investigate the effects of PDT on tissue morphology and vascularization in mouse tails.
- To determine the role of angiogenesis in vascular recovery following PDT.
Main Methods:
- Mice received intravenous meso-tetra (sulphonatophenyl) porphine (TPPS) followed by visible light exposure (PDT).
- Tissue cross-sections were analyzed to quantify epidermal, dermal, hypodermal, tendon, and bone areas.
- Blood vessel number and area in the dermis and hypodermis were measured in control and PDT-treated mice.
Main Results:
- PDT significantly increased the cross-sectional area of epidermis, dermis, and hypodermis at both 90 J/cm² and 180 J/cm² doses.
- The vascular compartment area increased significantly by day 5 post-PDT at both dose levels.
- A significant increase in the number of small blood vessels (<100 µm²) was observed at day 5 following the lower (90 J/cm²) PDT dose, but not the higher dose.
Conclusions:
- PDT induces tissue remodeling and vascular expansion in mouse tails.
- Angiogenesis is a key mechanism for vascular recovery after PDT.
- The dose of PDT influences the angiogenic response and vascular regeneration.