Open Research Projects

The role of oxalate transporters in maintaining kidney health

Prinicipal Investigator

Prof. Dr. Felix Knauf,
PD Dr. Martin Reichel
Dr. Harald Stachelscheid

Scientific interest within the context of the graduate college:

Our laboratory focuses on the mechanisms involved in maintaining oxalate homeostasis. Oxalate is a component of various foods and is absorbed via the intestine. High urinary oxalate concentrations lead to kidney stones, the second most common kidney disease after hypertension. Furthermore, we have shown that elevated blood oxalate concentrations are associated with cardiovascular disease.1 We are working translationally and recently demonstrated that oxalate uptake in the intestine can be reduced via an enzyme isolated from bacteria in patients.2

Our research group has cloned the first oxalate transporter (SLC26A6).3 SLC26A6 is expressed in different organs. The transporter is located on the apical side of epithelia and actively secretes oxalate into the intestinal lumen4 and urine.5,6 Via this transport process, the oxalate concentration in the body is kept low. If the transporter is missing, there is an increased uptake of oxalate from the intestine, and consequently the formation of kidney stones and progressive kidney damage.7

The subject of our current scientific work is the role of oxalate in the kidney and specifically its influence on the progression of renal diseases. For this purpose, we are working with pluripotent stem cells from which kidney organoids are derived as models.

Specifically, the question of our proposed thesis project is to what extent oxalate has toxic effect(s) on kidney cells. Here we have concrete preliminary data that an accumulation of oxalate has an intracellular toxic effect and that deletion of oxalate transporter SLC26A6 promotes cell death.

Project description:

WP 1: Characterization of renal organoids from pluripotent stem cells. SLC26A6 deficient human pluripotent stem cells have been generated using CRISP/Cas technology in collaboration with BIH Stem Cell Core. As a first step, you will 1) grow kidney organoids and 2) characterize the organoids using kidney cell markers.

WP 2: Examine the effect of oxalate accumulation using kidney organoids. You will be exposing human kidney organoids to oxalate in the presence and absence of the oxalate transporter SLC26A6. You will be examining the mechanism of cell death induced by oxalate by the 1) release of LDH, 2) changes in membrane integrity and 3) the activation of Casp-3 (by western blotting, immunohistochemistry of cleaved Casp-3, and measurement of cleavage activity using fluorescent substrate).

Application details

References

  1. Pfau A, Ermer T, Coca SG, […], Aronson PS, Drechsler C, Knauf F. High Oxalate Concentrations Correlate with Increased Risk for Sudden Cardiac Death in Dialysis Patients. J Am Soc Nephrol. 2021; 32:2375-2385, doi: 10.1681/ASN.2020121793.
  2. Lieske JC, Lingeman JE, Ferraro PM, […], Tosone C, Kausz AT, Knauf F. Randomized Placebo-Controlled Trial of Reloxaliase in Enteric Hyperoxaluria. N Engl J Med Evid. 2022. doi: 10.1056/EVIDoa2100053.
  3. Knauf F, Yang CL, Thomson RB, Mentone SA, Giebisch G, Aronson PS. Identification of a chloride-formate exchanger expressed on the brush border membrane of renal proximal tubule cells. Proc Natl Acad Sci USA. 2001; 98:9425-9430, doi: 10.1073/pnas.141241098.
  4. Neumeier LI, Thomson RB, Reichel M, Eckardt KU, Aronson PS, Knauf F. Enteric Oxalate Secretion Mediated by Slc26a6 Defends against Hyperoxalemia in Murine Models of Chronic Kidney Disease. J Am Soc Nephrol. 2020; 31:1987-1995. doi: 10.1681/ASN.2020010105.
  5. Knauf F, Ko N, Jiang Z, […], van Itallie CM, Anderson JM, Aronson PS.Net intestinal transport of oxalate reflects passive absorption and SLC26A6-mediated secretion. J Am Soc Nephrol. 2011; 22:2247-2255. doi: 10.1681/ASN.2011040433.
  6. Knauf F, Thomson RB, Heneghan JF, […], Egan ME, Alper SL, Aronson PS. Loss of Cystic Fibrosis Transmembrane Regulator Impairs Intestinal Oxalate Secretion. J Am Soc Nephrol. 2017; 28:242-249. doi: 10.1681/ASN.2016030279.
  7. Jiang Z, Asplin JR, Evan AP, […], Nottoli TP, Binder HJ, Aronson PS. Calcium oxalate urolithiasis in mice lacking anion transporter Slc26a6. Nat Genet. 2006; 38:474-478. doi: 10.1038/ng1762.