Page 109 - Effects of radiotherapy and hyperbaric oxygen therapy on oral microcirculation Renee Helmers

Late radiation-induced oral microvascular changes
that these observations in the RT area could be a result of impairment of
endothelial function and telangiectatic neocapillaries. Transcutaneous oxygen
pressure was reported unaffected after irradiation even after several years.24 Histopathologic studies reported vascular loss and fibrosis over time after RT in
HNCP.7,22,25 Irradiated HNCP oral mucosal punch biopsies (3 mm cross-sectional
thickness) showed that vessel lumen diameters in buccal mucosa did not differ
in subepithelial capillaries, whereas a marked increase in vascular lumens in
deeper connective tissue was observed.22 Interestingly, our results indicate that
patterns of angioarchitecture can be used to identify (subclinically) epithelial
thickness changes such as atrophy. A difference between control tissue
and irradiated tissue was observed, indicated by a decreased Fd paired with
epithelial atrophy represented by class 3 angioarchitecture in irradiated tissue
vs. an increased Fd and intact epithelium with class 1 capillary loop patterns
in control tissue. The findings from our study confirm a loss in capillary loops
in buccal mucosa, represented by a class 3 angioarchitecture, and a marked
increase in Øbv was measured in irradiated buccal mucosa compared to healthy
mucosa. Our results confirm previous histopathological observations.7,22,25
The presence of flow is potentially necessary to discover increases in lumen 5 diameter that are otherwise overlooked in histologic specimens; for this reason,
in vivo measurements are most veracious in reflecting actual pathology.
A clear observation during the assessment of irradiated tissue microcirculation in this study was the manifestation of telangiectasias [Fig. 3]. In other studies, telangiectasias were frequently described in different areas of irradiated cutaneous tissue and were attributed to impaired vasoregulatory mechanisms that resulted in altered hemodynamics and stasis.2,22,23 The observed distended vascular effect might be due to breakdown of downstream capillaries 23 and the potential irradiation damage to small diameter nerves that regulate blood flow distribution.2 Another proposed pathophysiological mechanism associated with RT is that the radiation injured endothelial cells and oxygen deprived extracellular environment around capillaries stimulate proliferation of neocapillaries of irregular calibers and morphology.2 Figure 3 (panels e and f) illustrates potentially an example of such an oxygen deprived site as described by Baker et al. showing disorganized, irregularly formed capillaries. Interestingly, early in the 1950s in atomic bomb survivors similar distorted loops in the labial mucosa was observed using intravital microscopy.2
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