Early Effects of Ionizing Radiation on the Collagen Hierarchical Structure of Bladder and Rectum Visualized by Atomic Force Microscopy

Abstract

Radiation therapy, widely used in the treatment of a variety of malignancies in the pelvic area, is associated with inevitable damage to the surrounding healthy tissues. We have applied atomic force microscopy (AFM) to track the early damaging effects of ionizing radiation on the collagen structures in the experimental animals' bladder and rectum. The first signs of the low-dose radiation (2 Gy) effect were detected by AFM as early as 1 week postirradiation. The observed changes were consistent with initial radiation destruction of the protein matrix. The alterations in the collagen fibers' packing 1 month postirradiation were indicative of the onset of fibrotic processes. The destructive effect of higher radiation doses was probed 1 day posttreatment. The severity of the radiation damage was proportional to the dose, from relatively minor changes in the collagen packing at 8 Gy to the growing collagen matrix destruction at higher doses and complete three-dimensional collagen network restructuring towards fibrotic-type architecture at the dose of 22 Gy. The AFM study appeared superior to the optical microscopy-based studies in its sensitivity to early radiation damage of tissues, providing valuable additional information on the onset and development of the collagen matrix destruction and remodeling.

Rectal-cancer radiotherapy damages the perineal muscle floor

“…[ 1 ] about radiation injury on the rectum deserves to be integrated with observations regarding the equivalent damage to the perineal striated muscles. In approaching this topic, not yet extensively studied, we were interested at first in delineating its basic pathology by histological methods, as already proposed [ 2 , 3 ]. For this, we selected from our anatomopathological archive 20 surgical specimens of abdominoperineal resections.…”

Late Changes in the Extracellular Matrix of the Bladder after Radiation Therapy for Pelvic Tumors

“…Although AFM is extensively applied in the studies on the ECM of different tissues, no systematic research utilizing AFM has been conducted so far on the radiation-affected human bladder ECM. In our previous study using an animal model [ 25 ], we demonstrated dependence of the early changes in the bladder ECM structure on the radiation dose. Here, we implement this approach to the clinical samples from patients after radiation therapy in addition to a novel quantitative assessment of the ECM structural alterations.…”

“…The packing pattern of collagen fibrils at the nanoscale generally repeats that of collagen fibers observed at the microscale (Figure 4a), and the fibrils are covered with an unstructured proteinaceous material (Figure 4f). Such a pattern was present in the animal bladder ECM [25], as well as in certain other types of connective tissue (a "basket-weave" packing of collagen fibers in the skin or arterial walls) [19,32].…”

“…In vivo studies of the collagen state after application of ionizing radiation in clinically relevant doses in tendon collagen [ 24 ] and in an animal model [ 15 ] by optical and physical techniques allowed for the revealing of the basic principles of the development of collagen radiation destruction and subsequent remodeling, depending on the level of its hierarchical organization (molecules, fibrils, fibers, and fiber bundles). The main manifestations of the post-radiation collagen alterations at the level of fibrils and fibers (at the nanoscale) appeared to be the formation of thicker fibers relative to the intact ones, disordering of the 3D structure and formation of deep ruptures in the matrix structure, as well as appearance of a large amount of an amorphous substance (presumably, proteoglycans) [ 25 ]. TPM revealed a decrease in the intensity of the second harmonics generation (SHG) signal from collagen [ 15 ] that reflected the processes of degradation and disordering of its 3D structure.…”

Collagen fibrillar structures in vocal fold scarring and repair using stem cell therapy: a detailed histological, immunohistochemical and atomic force microscopy study

“…Our own experience includes AFM application in tracking characteristic ECM changes in a variety of pathological processes (see, e.g. Kotova et al ., and references therein). Vocal fold ECM has also been studied with AFM, as we mentioned in Introduction (Sivasankar & Ivanisevic, ; Heris et al ., ; Lee et al ., ).…”