Mobilization of endogenous stem cells attenuates tubular cell damage and calcium oxalate crystal formation in the rat hyperoxaluric kidney
Ho-Shiang Huang1, Ming-Chieh Ma2
Department of Urology1, National Cheng Kung University, Tainan, Taiwan;
School of Medicine2, Fu Jen Catholic University, New Taipei City, Taiwan
Purpose: Cell therapy has been demonstrated to be beneficial for treatment of disease by enhancing self and/or endogenous repair in various organ tissues. Whether cell therapy is effective to alleviate tubular cell injury caused by hyperoxaluria during kidney stone formation is still unclear. This study aims to test whether mobilization of endogenous stem cells from bone marrow may protect kidneys against hyperoxaluria and further calcium oxalate (CaOx) crystal deposition.
Materials and Methods: Male Wistar rats were divided into control rats received standard diet and hyperoxaluric rats fed with 5% hydroxyl-L-proline (HP) in daily diet for 7 and 28 days. Another group of HP rats was received plerixafor, a selective CXCR4 blocker (AMD3100), continuously via a subcutaneous implant of mini-osmotic pump as CXCR4 antagonism is known to mobilize endogenous stem/progenitor cells into circulation. The 24 h of urine sample was collected to evaluate degree of supersaturation by estimation of the ionic activity of calcium oxalate (CaOx) and the amount of calcium crystal excretion in urine sedimentation. Blood sample was collected to evaluate the circulating level of CD34+CXCR4+ cells. Crystal distribution within the kidneys will be examined by counting crystal deposits by von Kossa staining. Protein expressions in renal tissues and in urine were quantitatively analyzed.
Results: Compared to the vehicle-treated HP rats, plerixafor significantly attenuated CaOx crystal deposition and increased the amount of urinary sediment after 28-day treatment but without any effect on hyperoxaluria and supersaturation at both time-points. Interestingly, circulating CD34+CXCR4+ cells were markedly elevated in the plerixafor-treated rats after 7 days and persisted thereafter. This was associated with an increase in renal expression of stromal cell-derived factor 1 (SDF-1) in the plerixafor-treated kidneys for 7 and 28 days. The urinary contents of two anticrystallization molecules, osteopontin (OPN) and Tamm-Horsfall protein (THP), in the plerixafor-treated HP rats were significantly increased as compared to those in the vehicle-treated HP groups for 7 and 28 days. This associated with an attenuation of enzymuria for tubular damage markers, a- and μ-glutathione-S-transferase (GST). Moreover, renal contents of OPN, THP, aGST, and μGST in the plerixafor-treated HP rats were higher than those in the vehicle-treated HP groups at both time-points.
Conclusion: These results clearly indicate that the anticrystallization effect of plerixafor is possibly related to an increase in CD34+CXCR4+ cell homing to the injured hyperoxaluric kidney with a higher SDF-1 expression, which attenuates tubular cell injury and against CaOx crystal formation by maintenance of renal production of OPN and THP. Attenuation of cell debris desquamated from damaged tubular cells may prevent seeding effect for calcium crystal formation in growth.