Stain-Free Characterization of Membranous Glomerulonephritis via Fourier Ptychographic Microscopy

Histology remains a cornerstone in diagnosis and prognosis of renal diseases. Histopathological analysis of kidney tissue is crucial for understanding renal pathophysiology. The availability of multiple stained sections is essential for conducting comprehensive histopathological analysis and achieving accurate diagnosis. Fourier ptychographic microscopy (FPM) has emerged as a promising microscopy technique. The ability to provide high-resolution, quantitative phase-contrast images over a wide area, particularly in a stain-free mode, makes FPM highly appealing to experts in histopathology. As renal pathologies are characterized by subtle morphologic changes encoded in tissue slides, phase maps obtained using FPM are well suited for providing detailed, high-contrast images of tissue structures. FPM provides a quantitative imaging tool that can be descriptive of the sample and/or expressive of the disease. Here, we explored FPM capability to image pathological kidney tissue, enabling pathologists to select regions of interest within the intricate architecture of renal tissue and zoom in to observe minute submicron structures, ranging from overall tissue organization and glomeruli distribution to individual basal membranes. Membranous glomerulonephritis (MG) was focused on because of its high dependence on histologic examination. We extracted descriptive features able to discriminate between healthy kidney tissues and those affected by MG. Moreover, FPM phase-contrast images allowed observing in detail the glomerular basal membranes and measuring the differences in lateral thickness with respect to healthy specimens. This is because of better glomerular membranes contrast in FPM images with respect to the hematoxylin-and-eosin-stained images. Our study shows the broad potential of FPM in characterizing hallmarks of MG disease even in stain-free tissue slides.