Lukáš Nedorost

Asymptomatic Abdominal Aortic Aneurysms Show Histological Signs of Progression: A Quantitative Histochemical Analysis

Objective: Abdominal aortic aneurysm (AAA) is a serious disease due to its covert nature, relatively high prevalence and fatal prognosis in the case of rupture. To obtain new insights into AAA pathogenesis, we examined the relationships between histopathology, multiplex in vitro immunoassay data, diameter and symptomatology. Methods: In a prospective, non-randomised study, we evaluated samples from 6 normal infrarenal aortae and 65 AAA patients (65 walls, 55 thrombi). The AAA patients were either asymptomatic (n = 44), symptomatic (n = 7) or with ruptured AAA (n = 14). The AAA diameter was classified as small (<5 cm, n = 18), medium (5–7 cm, n = 26) and large (>7 cm, n = 21). We quantified the histopathology of the AAA wall and the adjacent thrombus. We assessed the expression of proteins in the same samples. Results: Asymptomatic AAAs had walls with more abundant inflammatory infiltrates, lower amounts of PAI-1, a higher number of tPA-positive elements, a tendency towards decreased collagen content, whereas the adjacent thrombi had a greater concentration of VCAM-1 and MMP-2 when compared with symptomatic AAAs. Compared with the aneurysmatic aorta, the normal aorta contained less collagen and more elastin, actin, desmin and PAI-1-positive elements; in addition, it was more vascular. Medium-sized AAAs were the most actin and vimentin rich, and large AAAs were the most vascular. Conclusion: Our results show that asymptomatic AAA walls often have more potentially deleterious histopathological alterations than symptomatic AAA walls. This result indicates that a progression from an asymptomatic AAA to rupture can be expected and screening patients who are at risk of rupture could be beneficial.

Vasa vasorum quantification in human varicose great and small saphenous veins

Recent research regarding saphenous vasa vasorum (VV) has focused on two main topics: the VV during varicogenesis in chronic venous insufficiency and the VV in saphenous grafts used in reconstructive vascular surgery. Our aim has been (i) to establish a technique for the histological quantification of the VV in human varicose great and small saphenous veins and (ii) to describe the density and distribution of the vasa vasorum within varicose veins. Great (n=11) and small (n=5) saphenous veins (length, 15-40cm) were collected from 12 patients who were undergoing venous stripping due to chronic venous insufficiency (Clinical-Etiology-Anatomy-Pathophysiology class 2-3). The veins were divided into 5-cm long segments. In total, 92 tissue blocks were collected to trace the variability of the density and distribution of the vasa vasorum in the proximo-distal direction. The endothelium was detected by immunohistochemistry using the von Willebrand factor. We quantified the number of microvessel profiles per section area and the relative distance of the microvessels from the outer border of the adventitia. The VV did not exhibit a preferential orientation in the varicose veins. VV density profiles were highest in the middle third of the venous wall and lowest in the inner third of the venous wall. Both the density and distribution of VV were uniform along the veins, and no differences were observed between the great and small saphenous veins. The VV density was statistically independent of the relative distance from the adventitia. The usability of this technique for perioperative frozen sections remains to be tested.

Quantification of compact bone microporosities in the basal and alveolar portions of the human mandible using osteocyte lacunar density and area fraction of vascular canals

Based on the orientation of the osteons, the basal portion and the alveolar portion of the body of the human mandible can be distinguished. In the compact bone, two types of microporosities can be quantified, the osteocyte lacunae and the vascular canals. Our aim was (i) to perform three-dimensional reconstruction of osteocyte lacunae to suggest an efficient means of sampling to estimate their numerical density and (ii) to compare bone microporosities in the basal and the alveolar portions of ten mandibles. Using optical disector, we estimated the density of osteocyte lacunae, and using a stereological point-counting technique, we quantified the area fraction of the vascular canals. The diameter of the lacunae was 14±3μm. While the fraction of vascular canals was comparable in both parts of the body of the mandible, the numerical density of osteocyte lacunae was higher (p=0.007) in the alveolar portion (17056±1264/mm(3)) than in the basal portion (14522±665/mm(3)). The lacunar and vascular microporosities were statistically independent of each other. As this is the first three-dimensional counting of osteocyte lacunae, we discuss the relation of this parameter to the biomechanics of the mandible, and we compare our data with previously used two-dimensional methods. We present an efficient sampling method that is useful for the histological description of bone microporosities. When taking into account the spatial characteristics of lacunae, the locally specific numerical density of lacunae can be easily assessed with the three-dimensional counting method, which is not biased by the variation in size and orientation of the lacunae.

Correlating Micro-CT Imaging with Quantitative Histology

Advanced biomechanical models of biological tissues should be based on statistical morphometry of tissue architecture. A quantitative description of the microscopic properties of real tissue samples is an advantage when devising computer models that are statistically similar to biological tissues in physiological or pathological conditions. The recent development of X-ray microtomography (micro-CT) has introduced resolution similar to that of routine histology. The aim of this chapter is to review and discuss both automatic image processing and interactive, unbiased stereological tools available for micro-CT scans and histological micrographs. We will demonstrate the practical usability of micro-CT in two different types of three-dimensional (3-D) ex vivo samples: (i) bone scaffolds used in tissue engineering and (ii) microvascular corrosion casts.

Analysis of microcracks caused by drop shatter testing of porcine kidneys.

Although kidney trauma is a relatively common injury, its microscopic biomechanics are poorly understood. Experimental low-grade trauma in pig kidneys was studied using optical microscopy. We observed ruptures in the cortex as well as in the medulla. Both parts of the renal parenchyma were damaged, even in areas of the kidneys that were free of macroscopic cracks on the surface. To determine which constituents of the renal cortex and medulla, i.e. tubular parts of the nephron or the interstitial connective tissue, were less resistant to injury during the drop shatter test, we applied a simple stereological method to discriminate between random and tissue-specific rupture propagation. The ruptures propagated predominantly through the interstitial connective tissue of the renal cortex and medulla. The volume fraction of the tubules assessed by the Cavalieri principle was 90.4% within the renal cortex and 52.4% within the medulla. The most frequently affected blood vessels were the arcuate and interlobular veins, followed by the arcuate and interlobular arteries. No disruptions of the renal calyces were found.