Tokunori Yamamoto

Renal L-Type Fatty Acid–Binding Protein in Acute Ischemic Injury

Fatty acid-binding proteins (FABPs) bind unsaturated fatty acids and lipid peroxidation products during tissue injury from hypoxia. We evaluated the potential role of L-type FABP (L-FABP) as a biomarker of renal ischemia in both human kidney transplant patients and animal models. Urinary L-FABP levels were measured in the first urine produced from 12 living-related kidney transplant patients immediately after reperfusion of their transplanted organs, and intravital video analysis of peritubular capillary blood flow was performed simultaneously. A significant direct correlation was found between urinary L-FABP level and both peritubular capillary blood flow and the ischemic time of the transplanted kidney (both P < 0.0001), as well as hospital stay (P < 0.05). In human-L-FABP transgenic mice subjected to ischemia-reperfusion injury, immunohistological analyses demonstrated the transition of L-FABP from the cytoplasm of proximal tubular cells to the tubular lumen. In addition, after injury, these transgenic mice demonstrated lower blood urea nitrogen levels and less histological injury than injured wild-type mice, likely due to a reduction of tissue hypoxia. In vitro experiments using a stable cell line of mouse proximal tubule cells transfected with h-L-FABP cDNA showed reduction of oxidative stress during hypoxia compared to untransfected cells. Taken together, these data show that increased urinary L-FABP after ischemic-reperfusion injury may find future use as a biomarker of acute ischemic injury.

Hypoperfusion of peritubular capillaries induces chronic hypoxia before progression of tubulointerstitial injury in a progressive model of rat glomerulonephritis.

Chronic hypoxia likely plays a pivotal role in chronic renal disease, but the specifics of its involvement remain unclear. To elucidate how chronic hypoxia occurs and whether hypoxia participates in the progression of renal disease, the authors established an irreversible glomerulonephritis model induced by uninephrectomy and repeated anti-Thy-1 antibody injections. Glomerulosclerosis with microvascular obliteration was complete at 2 wk after antibody injection and was not restored until 11 wk. Tubulointerstitial injury was mild at 2 wk and was gradually exacerbated until 11 wk, a pattern that was in accordance with the loss of peritubular capillaries. Immunohistochemical analysis using pimonidazole revealed the augmentation of hypoxia in the cortex before the aggravation of tubulointerstitial injury and subsequent peritubular capillary loss. The preexistence of hypoxia implies that it had substantial participation in the progression of tubulointerstitial injury. To test whether blood flow was inhibited in diseased kidneys, capillaries with intact blood flow were identified by tail vein injection of biotinylated lectin specific to endothelial cells. The renal microvasculature was well recognized by lectin in the controls, whereas lectin binding to peritubular capillaries was strikingly decreased in diseased kidneys, suggesting a disturbance of blood flow. Intravital microscopy analysis confirmed that blood flow in peritubular capillaries was decreased by approximately 40% in the disease group compared with the controls. In conclusion, stagnation of blood flow in peritubular capillaries induced chronic hypoxia at an early stage in this model, which was followed by progressive tubulointerstitial injury and a loss of peritubular capillaries.

Periurethral injection of autologous adipose-derived stem cells for the treatment of stress urinary incontinence in patients undergoing radical prostatectomy: report of two initial cases.

Objectives:  To report a novel cell therapy using autologous adipose tissue‐derived stem cells (ADSC) for stress urinary incontinence caused by urethral sphincteric deficiency and the outcomes in two initial cases undergoing periurethral injection of stem cells for the treatment of urinary incontinence after radical prostatectomy.

Ischemic Renal Damage after Nephron-Sparing Surgery in Patients with Normal Contralateral Kidney

BACKGROUND Although nephron-sparing surgery (NSS) has been reported not to affect total renal function, the functional damage of the operated kidney is masked by the contralateral kidney in elective indications. OBJECTIVE To determine ischemic renal damage after NSS. DESIGN, SETTING, AND PARTICIPANTS From August 2005 to October 2007, 32 consecutive patients with elective indications underwent NSS. The mean tumor diameter was 2.6 cm. INTERVENTION Of our patients, the open surgery was performed in 20 patients, and laparoscopic surgery was performed in 12 patients. NSS was performed by hilar clamping with a warm ischemic time of 24.3 min. MEASUREMENTS We analyzed effective renal plasma flow (ERPF) calculated from (99m)Tc-mercaptoacetyltriglycine ((99m)Tc-MAG-3) renal scintigraphy and renal parenchymal volume (RPV) measured from computed tomography (CT) scan. In addition, we analyzed (99m)Tc-MAG-3 uptake regionally in the surgically non-affected parts. (99m)Tc-MAG-3 and CT scans were performed preoperatively and 1 wk and 6 mo postoperatively. RESULTS AND LIMITATIONS One week after NSS, ERPF of the operated kidney decreased by 28.7% (from 158.9 to 113.3 ml/min per 1.73 m(2), p<0.001), and RPV decreased by 12.6% (from 149.8 to 131.0 cm(3), p<0.001). These changes were stable for 6 mo. Regional (99m)Tc-MAG-3 uptake of the operated kidney with an ischemic time of > or = 25 min decreased to 61.8% after 1 wk and 70.9% after 6 mo. In contrast, with ischemic times within 25 min, regional (99m)Tc-MAG-3 uptake was 87.4% after 1 wk and 94.4% after 6 mo. This is a relatively small study, and the follow-up period is short. A larger sample size and longer follow-up may be required. CONCLUSIONS Although total renal function was almost unaffected before and after NSS, a warm ischemic time of > or = 25 min caused irreversible damage distributed diffusely throughout the operated kidney.

Periurethral injection of autologous adipose‐derived regenerative cells for the treatment of male stress urinary incontinence: Report of three initial cases

Objectives:  To report a novel cell therapy using autologous adipose tissue‐derived regenerative cells for male stress urinary incontinence caused by urethral sphincteric deficiency, and the outcomes in the initial cases undergoing periurethral injection of adipose tissue‐derived regenerative cells.

Regenerative treatment of male stress urinary incontinence by periurethral injection of autologous adipose-derived regenerative cells: 1-year outcomes in 11 patients.

To assess the efficacy and safety of a novel cell therapy for male stress urinary incontinence consisting of periurethral injection of autologous adipose‐derived regenerative cells, and to determine the 1‐year outcomes.

Distribution of hydrogen sulfide (H2S)-producing enzymes and the roles of the H2S donor sodium hydrosulfide in diabetic nephropathy

BackgroundHydrogen sulfide (H2S) has recently been found to play beneficial roles in ameliorating several diseases, including hypertension, atherosclerosis and cardiac/renal ischemia–reperfusion injuries. Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), the main enzymes in the transsulfuration pathway, catalyze H2S production in mammalian tissues. However, the distributions and precise roles of these enzymes in the kidney have not yet been identified.MethodsThe present study examined the localization of both enzymes in the normal kidney and the effect of the H2S donor sodium hydrosulfide (NaHS) in the renal peritubular capillary (PTC) under conditions of diabetic nephropathy, using pancreatic β-cell-specific calmodulin-overexpressing transgenic mice as a model of diabetes.ResultsIn the normal kidney, we detected expression of both CBS and CSE in the brush border and cytoplasm of the proximal tubules, but not in the glomeruli, distal tubules and vascular endothelial cells of renal PTCs. Administration of NaHS increased PTC diameter and blood flow. We further evaluated whether biosynthesis of H2S was altered in a spontaneous diabetic model that developed renal lesions similar to human diabetic nephropathy. CSE expression was markedly reduced under diabetic conditions, whereas CBS expression was unaffected. Progressive diabetic nephropathy showed vasoconstriction and a loss of blood flow in PTCs that was ameliorated by NaHS treatment.ConclusionThese findings suggest that CSE expression in the proximal tubules may also regulate tubulointerstitial microcirculation via H2S production. H2S may represent a target of treatment to prevent progression of ischemic injury in diabetic nephropathy.

Blood Velocity Profiles in the Human Renal Artery by Doppler Ultrasound and Their Relationship to Atherosclerosis

Blood velocity profiles were measured in the renal branch (diameter 5.9 +/- 1.3 mm) of the aortorenal bifurcation using a 20-MHz 80-channel pulsed Doppler velocimeter during retroperitoneal surgery in 10 patients. The peak Reynolds number was 1145 +/- 140 and the frequency parameter (Wormersley parameter) was 3.0 +/- 0.8. Immediately distal to the ostium of the renal artery, reverse flow, indicating flow separation, was observed near the cranial wall mainly during the first part of the cardiac cycle. There were flows from the cranial to the caudal side of the artery at this location, indicating the presence of strong secondary flows. Two diameters downstream of the ostium, the velocity profiles were skewed to the caudal side in all patients. Four diameters downstream, the flow profile was symmetrical (3 patients) or only slightly skewed (7 patients) and virtually parabolic throughout the cardiac cycle. These observations mean that the flow on the cranial side of the renal branch of the human aortorenal bifurcation is characterized by (1) a bidirectional oscillation of the flow, (2) separation of the flow during systole, and (3) low time-averaged shear rate. These blood velocity patterns may be related to the localization and development of atheromatous plaque that occurs preferentially in this region of the renal artery. Conversely, the unidirectional, axisymmetrical flow found in more distal parts of the renal artery are associated with a very low incidence of lesions.

Role of Asymmetrical Dimethylarginine in Renal Microvascular Endothelial Dysfunction in Chronic Renal Failure with Hypertension

We examined whether endothelial function of the renal microcirculation was impaired in a model of chronic renal failure (CRF), and further assessed the role of asymmetrical dimethylarginine (ADMA) and its degrading enzyme, dimethylarginine dimethylaminohydrolase (DDAH), in mediating the deranged nitric oxide (NO) synthesis in CRF. CRF was established in male mongrel dogs by subtotal nephrectomy, and the animals were used in experiments after a period of 4 weeks. The endothelial function of the renal afferent and efferent arterioles was evaluated according to the response to acetylcholine, using an intravital needle-lens charge-coupled device camera. Intrarenal arterial infusion of acetylcholine (0.01 μg/kg/min) elicited 22±2% and 20±2% dilation of the afferent and efferent arterioles in normal dogs. In dogs with CRF, this vasodilation was attenuated (afferent, 12±2%; efferent, 11±1%), and the attenuation paralleled the diminished increments in urinary nitrite+nitrate excretion. In the animals with CRF, plasma concentrations of homocysteine (12.2 ±0.7 vs. 6.8±0.4 μmol/l) and ADMA were elevated (2.60±0.13 vs. 1.50 ±0.08 μmol/l). The inhibition of S-adenosylmethionine-dependent protein arginine N-methyltransferase by adenosine dialdehyde decreased plasma ADMA levels, and improved the acetylcholine-induced changes in urinary nitrite+nitrate excretion and arteriolar vasodilation. Acute methionine loading impaired the acetylcholine-induced renal arteriolar vasodilation in CRF, but not normal dogs, and the impairment in CRF dogs coincided with the changes in plasma ADMA levels. Real-time polymerase chain reaction revealed downregulation of the mRNA expression of DDAH-II in the dogs with CRF. Collectively, these results provide direct in vivo evidence of endothelial dysfunction in canine CRF kidneys. The endothelial dysfunction was attributed to the inhibition of the NO production by elevated ADMA, which involved the downregulation of DDAH-II. The deranged NO metabolic pathway including ADMA and DDAH is a novel mechanism for the aggravation of renal function.

Change in Contralateral Renal Parenchymal Volume 1 Week After Unilateral Nephrectomy

OBJECTIVES To measure the contralateral renal parenchymal volume (RPV) before and after nephrectomy and investigate the factors influencing compensatory hypertrophy. Unilateral nephrectomy induces compensatory hypertrophy in the contralateral kidney. METHODS From December 2003 to January 2008, 142 patients undergoing nephrectomy were enrolled in this study. All patients underwent preoperative technetium-99m dimercaptosuccinic acid renal scintigraphy. The percentage of technetium-99m dimercaptosuccinic acid uptake in the resected kidney was 37.2% +/- 15.3%. Contrast-enhanced computed tomography was performed preoperatively and 1 week and 6 months postoperatively, and RPV was calculated as the normally functioning tissue, excluding tumors or nonenhanced areas. RESULTS The mean RPV of the remaining kidney was 164.2 cm(3) preoperatively and 184.1 and 178.8 cm(3) at 1 week and 6 months postoperatively, respectively. Multivariate regression analysis revealed that the increase in RPV was positively associated with the percentage of technetium-99m dimercaptosuccinic acid uptake in the resected kidney (P < .001) and negatively associated with patient age (P = .008). Logistic regression analysis showed that the group with an RPV increase of <15% had a 4.1-fold increased risk of a 10% decrease in the glomerular filtration rate during the next 6 postoperative months compared with the risk in the group with an RPV increase of >or=15% (P = .004). CONCLUSIONS The change in contralateral RPV occurred during the first week after nephrectomy and remained stable for >or=6 months. The change in RPV increased when the removed kidney had greater function and decreased with increasing patient age. The risk of progression to renal insufficiency can be predicted according to the change in RPV.