Microstructures of Randall’s plaques and their interfaces with calcium oxalate monohydrate kidney stones reflect underlying mineral precipitation mechanisms

Abstract

Randall's plaques (RP) are preferred sites for the formation of calcium oxalate monohydrate (COM) kidney stones. However, although processes of interstitial calcium phosphate (CaP) plaque formation are not well understood, the potential of plaque microstructures as indicators of CaP precipitation conditions received only limited attention. We investigated RP-associated COM stones for structural details of the calcified tissues and microstructural features of plaque-stone interfaces as indicators of the initial processes of stone formation. Significantly increased CaP supersaturation can be expected for interstitial fluid, if reabsorbed ions from the tubular system continuously diffuse into the collagenous connective tissue. Densely packed, fine-grained CaP particles were found in dense textures of basement membranes while larger, laminated particles were scattered in coarse-meshed interstitial tissue, which we propose to be due to differential spatial confinements and restrictions of ion diffusion. Particle morphologies suggest an initial precipitation as metastable amorphous calcium phosphate (ACP). Morphologies and arrangements of first COM crystals at the RP-stone interface ranged from stacked euhedral platelets to skeletal morphologies and even porous, dendritic structures, indicating, in this order, increasing levels of COM supersaturation. Furthermore, these first COM crystals were often coated with CaP. On this basis, we propose that ions from CaP-supersaturated interstitial fluid may diffuse through porous RP into the urine, where a resulting local increase in COM supersaturation could trigger crystal nucleation and, hence, initiate stone formation. Ion-depleted fluid in persistent pores of initial COM layers may get replenished from interstitial fluid, leading to CaP precipitation in porous COM.

Effectiveness of Herbal Medicine in Renal Lithiasis: a Review

“…These plaques originate adjacent to the thin limbs of loops of Henle as spherical particles, which could be related to the high local ion concentrations at this site, and can extended to the interstitium. [14][15][16] Recent studies have investigated the role of oxalate-degrading bacteria. These form apatite structures that serve as a crystallization center for the formation of stones and could be a pharmacological target to avoid the nucleation process.…”

Factors Affecting the Environmentally Induced, Chronic Kidney Disease of Unknown Aetiology in Dry Zonal Regions in Tropical Countries—Novel Findings

“…As discussed in the Section 1.9, nanominerals are formed in both renal tubules and within tubular cell cytoplasm [59]. With chronic persisting supersaturation of tubular fluid, CaPO 4 nanoparticles with continue to grow [63]; however, the rate of growth is very slow, thus the disease takes over a decade to manifest. In addition to growth, these nanoparticles agglomerate, and some incorporates F − forming stable fluoroapatite.…”

“…The chronic dehydration of outdoor workers in CKDmfo-affected regions and the mentioned characteristics create an internal environment favourable for the precipitation of nanominerals in renal tubular tissues. These include calcium phosphate hydroxyapatite as well as CaOX and urate precipitates, based on their tissue and tubular fluid supersaturations [63].…”

Physicochemistry in medicine: some selected examples

“…142,143 As this point, it is worth underlining that calcium oxalate stone incidence has increased worldwide during the past decades. 143,144 The observation that a growing number of kidney stones are related to RP has motivated a large number of investigations based on last generation characterisation techniques (see, for example, recent References 145 and 146).…”