H E A L T H I N N O V A T I O N , O V E R C O M I N G D I S E A S E S A N D P A N D E M I C S

S C I E N T I F I C H I G H L I G H T S

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Fig. 10: Photos of Perl s stained tissue with (a) 2.5× and (b) with 10× magnification of the selected region enclosed in the cyan box. X-ray fluorescence intensity maps of (c) calcium, (d) potassium, (e) iron, (f) silicon, (g) phosphorus, (h) sulfur, (i) manganese and (j) titanium were collected at 7.3 keV with a step size of 500 nm and 300 ms/pixel acquisition time. Scale bar is 20 μm.

X-ray microscopy reveals environmental pollutants incrusted in iron in endometriotic lesions

X-ray fluorescence microscopy has been used to track iron and other environmental pollutants in endometrial lesions. The presence of iron is associated with the accumulation of environmental metals, supporting the idea that environmental exposure to toxic chemicals could play a role in the disease.

Endometriosis is an inflammatory disease affecting 10 15% of women worldwide, caused when endometrial tissue similar to the lining of the uterus grows outside the uterine cavity, such as in the ovaries and fallopian tubes. This causes pain and, in many cases, infertility. While the factors that may lead to endometriosis are elusive, ranging from genetic predisposition to autoimmune diseases and environmental triggers, it is known that iron deposits are common in endometrial lesions, indicating an altered iron metabolism at this level. Parallel to iron, the presence and accumulation of traces of other chemical elements considered to be of environmental origin have been documented in the human endometrium, such as lead, mercury, cadmium, chromium and silver. Some of these metals are known to be metalloestrogens, which mimic the effects of estrogen and can bind to estrogen receptors and activate them, leading to estrogenic effects in the body. Many metals are not tolerated by humans at any concentration and may accumulate in tissues and organs as persistent environmental endocrine disruptors. Identifying a possible relationship between iron

dysmetabolism and the accumulation of environmental metals in endometrial lesions could therefore lead to therapeutic approaches.

This study aimed to investigate the iron overloads as well as the possible appearance of other metals in the endometrial lesions of women affected by endometriosis through the use of X-ray fluorescence (XRF) imaging, which can be used to characterise the distribution of elements in biological specimens with subcellular spatial resolution. Histological and histochemical (Perl s staining) analysis was combined with XRF microscopy at beamline ID21 to investigate the presence and distribution of iron and other heavy metals in the ovarian endometriomas of 12 endometriosis patients and in 7 healthy endometrium samples. The XRF analysis revealed the presence of iron with an increased sensitivity compared to histochemical staining, highlighting the intracellular distribution of iron in the epithelial endometrium, stroma and macrophages of the endometriotic lesions, as shown in Figure 10. The data showed that iron specifically accumulated in multiple micro-aggregates in these samples, reaching concentrations up to 10 20% p/p. Interestingly, other metals such as silicon (Figure 10f), manganese (Figure 10i) and titanium (Figure 10j) were also found to be accumulated in the region where iron was found.

In order to reach nanoscale spatial resolution and increase the number of detectable chemical elements, a select number of samples were studied using nano-XRF mapping at beamline ID16B. This analysis revealed the presence of a number of potentially toxic metals such as lead, bromine, titanium, aluminium, chromium, silicon and rubidium,