Investigating Intracellular Mechanisms of Infection Stone Formation

• Applicant: Dr. Roman Herout
• Subject Area: Reproductive Medicine, Urology
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447437311

Infection stones are a distinct group among urinary stones which account for approximately 10-15% of all urinary stone cases. An associated infection with bacteria that produce an enzyme called urease is crucial for infection stone formation. In the presence of these bacteria that produce urease due to a rise in the pH level “struvite-apatite dust” is formed around and within the urease-producing bacteria, resulting in the initiation of crystal growth. The current knowledge of infectious stone formation is sparse and mainly limited to the hypothesis that crystal formation and growth is initiated by bacterial biofilm on the surface of the urothelium. Based on key preliminary data the research group at The Stone Centre at Vancouver General Hospital under the direction of Dr. Dirk Lange is pursuing an additional mechanism for struvite stone formation. Specifically, work in the literature and the Lange laboratory have shown that Proteus strains are able to invade uroepithelial cells, via mechanisms that remain to be elucidated. These findings are highly relevant to struvite stone formation, as intracellular crystal formation by invading Proteus has not been described to date. To expand our understanding of specific outer membrane components required for the adhesion and invasion process of Proteus mirabilis in kidney epithelial cells, we will study the ability for mutants deficient in outer surface to undergo these important pathogenic processes. Studying both adhesion and invasion processes of wild type (WT) and mutant strains will not only expand our knowledge on bacterial factors important for currently known biofilm-mediated struvite formation mechanisms but will also shed light on a potential intracellular mechanism that has not yet been described. As a next step we will study the role that P. mirabilis uroepithelial cell invasion plays in promoting recurrence of P. mirabilis-induced struvite stone formation using an in vivo mouse model of catheter-associated urinary tract infections, where Proteus is a key player in catheter encrustation and resultant pyelonephritis and struvite stones. Our primary aim is to study a potential new mechanism of struvite stone formation via invasion of Proteus mirabilis into kidney epithelial cells and subsequent intracellular crystal formation. Furthermore, the study of adherence and invasion mechanisms of Proteus mirabilis will provide important data to expand our understanding of factors important for P. mirabilis infection. The long-term goal of this research fellowship is to establish a long-lasting collaboration with the VGH Stone Centre and to further expand the research and especially the basic science research with regards to urolithiasis in Dresden. This fellowship represents a unique opportunity to be trained in translational research and take this knowledge back to constitute a stone research laboratory at the Technical University in Dresden in the future.

• DFG Programme: WBP Fellowship
• International Connection: Canada
• Host: Professor Dirk Lange, Ph.D.