Background: Fibroses of vessels and soft tissue are side effects of radiotherapy. The authors assumed that there was an immediate direct radiogenic damage of collagen of bone, periosteum and skin.
Material and methods: 15 porcine jaws samples (group 1) were exposed to a total dose of 60 Gy (cobalt-60, 2 Gy/day, five fractions/week). 15 jaws samples were stored accordingly (group 2, no irradiation, control). Collagen fragments of bone, periosteum and skin samples of groups 1 and 2 were isolated by ultrafiltration. Collagen types were characterized by SDS-PAGE measurement of the mature collagen cross-links hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) by high-performance liquid chromatography (HPLC) and analysis of hydroxyproline (Hyp) was used to determine the ratio of the amount of collagen fragments from irradiated as opposed to nonirradiated samples.
Results: The concentrations of HP, LP and Hyp in ultrafiltrates of probes of irradiated bone, periosteum and skin were markedly increased (average factors for bone: 3.69, 1.84, and 3.40, respectively; average factors for periosteum: 1.55, 1.41, and 1.77, respectively; average factors for skin: 1.55, 1.60, and 2.23, respectively) as compared to nonirradiated probes. SDS-PAGE did show collagen types I and V in nonirradiated bone, I and III in nonirradiated skin, and I in nonirradiated periosteum samples. In irradiated samples, smeared bands illustrated fragmentation of the collagen molecule.
Conclusion: The increased concentrations of HP, LP and Hyp in ultrafiltrates indicated increased concentrations of split collagen. Direct and instant radiogenic damage of (extracellular matrix of) bone, periosteum and skin tissue collagen could be demonstrated.