ORIGINAL PAPER Farooq A. Shiekh Æ Madhu Khullar Æ S. K. Singh Lithogenesis: induction of renal calcifications by nanobacteria Received: 28 September 2005 / Accepted: 16 November 2005 Ó Springer-Verlag 2006 Abstract Nanobacteria have been isolated from kidney stones and it has been suggested that they may act as a nucleus for the initiation of the renal stones. In the present study, we examine their role in biocrystallization and their in vivo effects on kidney pathology. Calcium oxalate monohydrate (COM) assay was carried out in the presence of nanobacteria to study biocrystallization. Wistar rats were given an intravenous injection of nanobacteria and the kidneys were examined for path- ological changes. The COM assay showed accelerated biocrystallization of 14 C-oxalate in the presence of nanobacteria, indicating them to be efficient candidates for biomineralization. Histopathological studies re- vealed bacteria induced renal tubular calcifications and various manifestations of infection. Our studies confirm that nanobacteria may be involved in the pathogenesis of renal tubular calcification. Keywords Lithogenesis Æ Nanobacteria Æ Calcification Æ Biocrystallization Æ Renal calculi Æ Rats Introduction Biocrystallization of calcium is encountered in many diseases such as kidney stone disease, atherosclerosis, chronic pancreatitis, rheumatoid arthritis, and various other tissues in the body [1]. Several theories have been put forward to explain the etiology of renal calcifica- tion but none has been able to answer fully the ques- tions concerning the genesis of renal calculi [2]. This is due to the fact that several factors such as hypercalci- uria, hyperoxaluria, stone matrix, promoter and inhibitor molecules, and bacteria, etc. may be involved in the etiology of this disease. These molecules may alter or modify crystal formation or may provide pre- existing surfaces for biocrystallization [3–7]. Bacteria and other cell types can create nucleation sites or nu- cleus, which is considered to be central in the genesis of kidney stones [8, 9]. It has been shown that microor- ganisms could be a factor in dental plaque calcium nucleation and the same may be true for urinary lithi- asis [7, 19, 20]. Recently, it was reported that a novel bacteria, nanobacteria, may be involved in the genesis of renal stones. These bacteria have been isolated from renal stones [9, 10]. These are the smallest described bacteria to date and are phylogenetically close relatives of mineral forming bacteria [11, 12]. Nanobacteria have been shown to mineralize calcium and phosphate even under physiological conditions, indicating that these bacteria could have a contributory role in urolithiasis [13, 14]. It has been proposed that nanobacteria may serve as biomineralization centers as they produce carbonate apatite on their cell walls for the initiation of kidney stones. Cuerpo et al. [15] showed that when these bacteria were injected intravenously, they accumulate in the kidney and produced apatite. These bacteria have been shown to accumulate in the kidney [16]; however, studies on in vivo effects of these bacteria on the kidneys are lacking. In our study we investigated the effects of intravenous administration of nanobacteria on kidney in Wistar rats. We found evidence of their inflammatory infiltration and accumulation in the cortex; in addition, small uniform renal calcification was seen on the surface of renal tubules. It could be that the kidney is a preferred site for mineralization by these tiny bacteria. It is also plausible that other body calcifications could have a nanobacterial element. F. A. Shiekh Æ M. Khullar (&) Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, 160012 Chandigarh, India E-mail: madhu_Khullar@hotmail.com Tel.: +91-172-2747585 Fax: +91-172-747403 S. K. Singh Department of Urology, Postgraduate Institute of Medical Education and Research, 160012 Chandigarh, India Urol Res (2006) DOI 10.1007/s00240-005-0034-0