Abnormal differentiation of the renal stem/progenitor pool into kidney tissue can lead to renal hypodysplasia (RHD), but the underlying causes of RHD are not well understood. In this multicenter study, we identified 20 Israeli pedigrees with isolated familial, nonsyndromic RHD and screened for mutations in candidate genes involved in kidney development, including PAX2, HNF1B, EYA1, SIX1, SIX2, SALL1, GDNF, WNT4, and WT1. In addition to previously reported RHD-causing genes, we found that two affected brothers were heterozygous for a missense variant in the WNT4 gene. Functional analysis of this variant revealed both antagonistic and agonistic canonical WNT stimuli, dependent on cell type. In HEK293 cells, WNT4 inhibited WNT3A induced canonical activation, and the WNT4 variant significantly enhanced this inhibition of the canonical WNT pathway. In contrast, in primary cultures of human fetal kidney cells, which maintain WNT activation and more closely represent WNT signaling in renal progenitors during nephrogenesis, this mutation caused significant loss of function, resulting in diminished canonical WNT/b-catenin signaling. In conclusion, heterozygous WNT4 variants are likely to play a causative role in renal hypodysplasia.

A novel heterozygous PTH/PTHrP receptor missense mutation (T410R) was identified in a male and his two sons who are all affected by a less severe form of Jansen's metaphyseal chondrodysplasia (JMC). JMC is a rare disorder that is typically characterized by severe growth plate abnormalities that lead to short-limbed dwarfism. Furthermore, affected individuals usually show significant hypercalcemia, despite normal or undetectable levels of PTH and PTHrP. In contrast, the three affected members of this new family showed only mild skeletal dysplasia, comparatively normal stature, and blood calcium concentrations either within or at the upper end of the normal range. However, PTH levels were suppressed, and urinary calcium excretion was elevated, which led to nephrolithiasis in both children. When expressed in COS-7 cells, the PTH/PTHrP receptor with the T410R mutation led to agonist-independent cAMP formation, which was less pronounced than that observed with the previously identified T410P mutant. Our findings indicate that a mild form of JMC has been identified that is characterized by less pronounced skeletal and laboratory abnormalities.

Using living donor organs for sequential liver and kidney transplantation (SeqLKT) in patients with primary hyperoxaluria type 1 (PH1) has emerged as a viable approach. Taking both organs from a single donor, however, is rare. There are 8 reported cases of SeqLKT in the literature, and in all but 1 case, children were the recipients. We present our experience with SeqLKT in 2 young adults with PH1. In the first case, with an interval between procedures of 4.5 months, SeqLKT was performed with a right liver lobe from a 47-year-old father for his 19-year-old son with PH1 who was on dialysis for 2 years before transplantation. Both the donor and the recipient had an uneventful recovery, although there was re-exploration for the control of bleeding in the recipient after liver transplantation. Thirty-three months after transplantation, the patient had normal liver and renal function. In the second case, with an interval between procedures of 22 days, SeqLKT was performed with organs from a 45-year-old father for his 19-year-old daughter with PH1 who was on dialysis for 8 months. The recipient procedures, including right liver lobe transplantation and kidney transplantation, were uneventful. The donor underwent percutaneous drainage of a subphrenic collection and subsequently fully recovered. Eighteen months after transplantation, the recipient's liver and renal allograft function was normal. In conclusion, because of the severe organ shortage, living related SeqLKT using the same donor should be carefully considered for young adults with PH1.

Uremic patients undergoing hemodialysis (HD) are known to be highly susceptible to infections. Recent data indicate that in addition to its well-known stimulating effects on red cell production, erythropoietin (EPO) may also have immunomodulating properties. The aim of this study was to examine the effect of EPO on lectin-induced T-lymphocyte transformation in uremic patients, as part of its effect on the immune response. Sixteen HD patients and 20 age- and sex-matched healthy controls were compared before and after 6 and 20 weeks of EPO treatment. T lymphocytes were analyzed for their mitogenic activity following treatment with phytohemagglutinin (PHA), concanavalin A (CON A) and anti-CD3 by measuring ³H-thymidine incorporation. HD patients showed reduced mitogenic responses to all mitogens tested, compared to healthy controls. During the 6 weeks of EPO administration, a significant increase in T-lymphocyte activity could be demonstrated following exposure to all three mitogens (PHA, from 32 ± 2 to 45 ± 8; CON A, from 11 ± 3 to 25 ± 9; anti-CD3, from 11 ± 3 to 22 ± 5, means ± SD). This increase was augmented after 5 months of EPO treatment. We conclude therefore that EPO improves in vitro T-cell mitogenic proliferation, even after short periods of treatment.

Background: The natriuretic/diuretic response to atrial natriuretic peptide (ANP), an important regulator of water and Na⁺ balance, is markedly attenuated in nephrotic syndrome (NS). It has been suggested that the diminished renal responsiveness to ANP may contribute to the pathogenesis of salt retention and edema formation in NS. However, the mechanisms underlying the renal hyporesponsiveness to ANP remain largely unknown. Methods: The acute effects of exogenous infusion of ANP (5 µg/kg + 10 µg/kg/h) were studied by clearance methodology in control rats, hypoalbuminemic rats with Adriamycin (ADR)-induced NS and in ADR-treated rats infused with hyperoncotic albumin sufficient to restore plasma albumin to normal levels. Results: Administration of ANP to control rats resulted in a significant increase in urinary flow rate, absolute rate of sodium excretion (+456%) and glomerular filtration rate (GFR). Mean arterial blood pressure decreased following infusion of the peptide. In the nephrotic rats, baseline GFR and Na⁺ excretion were significantly lower than in the control animals, and the renal effects of ANP were markedly blunt compared to the control animals. In contrast, the hypotensive effect of ANP in the ADR-treated rats was largely preserved. Infusion of hyperoncotic albumin prior to ANP administration reversed the decrease in baseline GFR and Na⁺ excretion and completely restored the renal effects of ANP in the nephrotic rats. Conclusion: These findings indicate that renal hyporesponsiveness to ANP in rats with ADR-induced NS is a reversible phenomenon that appears to be of functional origin rather than reflecting permanent cellular damage.