Page 88 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

Chapter 4
DISCUSSION
The aim of the present study was to develop a pilot IR model in which the effects of late IR injury could be measured noninvasively in the oral mucosal microcirculation and in mandibular bone by histological analysis. Using the MicroScan it was possible to sequentially measure the mucosal microcirculation over an extended period of time to monitor and quantify functional and anatomic changes. Interestingly, at the end of 11 weeks the results showed that RT administered in different fractions and intensities corresponding with cumulative doses equivalent to 22.4 Gy, 26 Gy, 30 Gy and 32 Gy established no evident altered perfusion or lasting microvascular changes besides bud-like telangiectasia observed after a single dose of 30 Gy. There was a gradual IR dose-dependent increase in pathophysiological changes observed in groups II-IV that presented most prominently as reduced vascularity, fibrosis of soft tissue and bone and necrosis of teeth and bone tissue after a single dose of 30 Gy.
SDFI previously showed changes in oral microcirculation in rabbit wound vascularization studies in response to chemotherapy and hyperbaric oxygen therapy.12,22 Although no clear late IR effect could be detected in our microcirculation data at T11 in all groups, there was a notable recurring effect around T5 regarding clinical side effects (no regrowth of hair at side of irradiation in Group IV), reduced TVD and PVD (Group I, II and IV) and decreased PLTs (Group I, III and IV) compared to baseline. This suggests that our study may reflect microcirculation dynamics potentially associated with the onset of IR injury in a transition phase prior to late IR injury. The observation of a transient decrease in functionality of the microcirculation could be a result of leaking or thrombosed capillaries injured by IR. A decrease in PLTs associated with locoregional IR, which is supported although not valued as clinically relevant by the scarcely available literature,36,37 could further reduce angiogenesis and repair in compromised IR tissue as they contain platelet-derived growth factors.30 Recently in an observational clinical study, late IR injury in oral mucosal microcirculation was described as showing significant rarefaction in capillary density, irregularly enlarged blood vessel diameters and telangiectasias.13 Interestingly, group IV showed scattered bud-like telangiectasia in the microcirculation with this appearing most prominently at T2, i.e. 2 weeks after RT. Since none of the other groups showed this type of phenomenon in the microcirculation, a higher
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