In murine and human hyperoxaluric conditions, macrophages can be seen surrounding renal calcium oxalate (CaOx) crystal deposits. We hypothesize that macrophages play a role in degrading and destroying these deposits and investigated inflammatory response and phagocytic mechanisms when macrophages are exposed to human kidney stones and inorganic crystals.
Human monocytes were differentiated into resting, fully-differentiated macrophages by treating with recombinant human M-CSF or GM-CSF for 6 days. After confirming phenotype by flow cytometry, macrophages were exposed for 20 hours to fragments of sterile human CaOx stones or CaOx crystals. Crystal uptake was determined, and supernatant cytokine and chemokine profiles were analyzed using antibody arrays. qRT-PCR was used to validate mRNA profile expression.
Under direct-vision fluorescent microscopy, activated human macrophages were noted to surround both stone fragments and synthesized crystals and destroy them in a step-by-step process that involved clathrin-mediated endocytosis and phagocytosis. An inflammatory cascade was released by macrophages, including chemokines CCL2, CCL3, interleukin-1 receptor antagonist (IL-1ra), complement component C5/C5a and IL-8. The response patterns to stone and crystal material was dependent on macrophage phenotype and activation status.
In our in vitro study, macrophages differentiated with M-CSF displayed a greater ability to phagocytize crystal deposits than those treated with GM-CSF. Following clathrin-mediated endocytosis, macrophages released a number of cytokines crucial for inflammatory immune response, suggesting that tissue macrophages play an important role in preventing kidney stone disease by removing and digesting interstitial renal crystal deposits.
The Journal of urology. 2015 Nov 25 [Epub ahead of print]
Sergei Kusmartsev, Paul R Dominguez-Gutierrez, Benjamin K Canales, Vincent G Bird, Johannes Vieweg, Saeed R Khan
Department of Urology, College of Medicine, University of Florida, Gainesville, Florida, 32610. Department of Urology, College of Medicine, University of Florida, Gainesville, Florida, 32610. , Department of Urology, College of Medicine, University of Florida, Gainesville, Florida, 32610. , Department of Urology, College of Medicine, University of Florida, Gainesville, Florida, 32610. , Department of Urology, College of Medicine, University of Florida, Gainesville, Florida, 32610. , Department of Urology, College of Medicine, University of Florida, Gainesville, Florida, 32610; Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, 32610.