Evaluation of pediatric cadaver kidneys transplanted into adult recipients receiving cyclosporine

Structure of SWI/SNF chromatin remodeller RSC bound to a nucleosome

Chromatin remodelling complexes of the SWI/SNF family function in the formation of nucleosome-depleted, transcriptionally active promoter regions (NDRs)^1,2. The essential Saccharomyces cerevisiae SWI/SNF complex RSC³ contains 16 subunits, including the ATP-dependent DNA translocase Sth1^4,5. RSC removes nucleosomes from promoter regions^6,7 and positions the specialized +1 and –1 nucleosomes that flank NDRs^8,9. Here, we present the cryo-EM structure of RSC in complex with a nucleosome substrate. The structure reveals that RSC forms five protein modules and suggests key features of the remodelling mechanism. The body module serves as a scaffold for the four flexible modules that we call DNA-interacting, ATPase, arm and ARP modules. The DNA-interacting module binds extra-nucleosomal DNA and is involved in the recognition of promoter DNA elements^8,10,11 that influence RSC functionality¹². The ATPase and arm modules sandwich the nucleosome disc with their ‘SnAC’ and ‘finger’ elements, respectively. The translocase motor of the ATPase module engages with the edge of the nucleosome at superhelical location +2. The mobile ARP module may modulate translocase-nucleosome interactions to regulate RSC activity⁵. The RSC-nucleosome structure provides a basis for understanding NDR formation and the structure and function of human SWI/SNF complexes that are frequently mutated in cancer¹³.

TRANSPLANTE RENAL EM BLOCO DE DOADORES-CADÁVERES INFANTIS: EXPERIÊNCIA DO HCFMRP-USP

A grande procura de órgãos para transplante tornou necessária a aceitação de potenciais doadores pediátricos a fim de aumentar a oferta. Trabalhos anteriores relatando menor sobrevida do enxerto e taxas maiores de complicação fizeram com que cirurgiões considerassem o assunto com cautela. Esse é um estudo retrospectivo com o objetivo de analisar os resultados de transplantes renais em bloco de doadores infantis (< 2 anos) no HCFMRP-USP entre 1998 e 2000. Um total de cinco pacientes foi submetido a transplante renal em bloco de doadores com idades entre 9 meses e 2 anos de vida, pesando entre 8 e 14 kg. Apenas um paciente perdeu o enxerto no oitavo dia após transplante devido à trombose. Dois pacientes tiveram complicações ureterais, um com necrose do ureter e fístula urinária e outro com ruptura completa da anastomose ureterovesical. Ambos foram reparados com sucesso. Complicação intra-operatória foi observada em um paciente, com ruptura da anastomose arterial. Corrigiu-se com reperfusão in loco e reanastomose. Outro paciente apresentou ruptura do pólo renal inferior, tratada com nefrectomia polar no quarto dia pós-operatório. Seguimento médio de 20,7 meses mostrou, apesar de tais problemas, creatinina sérica variando entre 0,9 e 2 mg/100 ml, sem complicações sérias. Nossos achados sustentam o uso de rins infantis, em bloco, mesmo de doadores com menos de 2 anos de idade, desde que a necessidade do órgão seja maior que o risco oferecido pelo alto índice de complicações.

Outcome of en bloc and single kidney transplantation from very young cadaveric donors

BACKGROUND

The optimal use of very young cadaveric kidneys (from donors less than 4 years old) remains controversial. High rates of technical complications and poor functional results compared with adult donor kidneys have been reported. The use of en bloc transplantation to overcome these problems has been advocated, although en bloc transplantation halves the number of potential transplants from very young donors.

METHODS

We studied the technical and functional results of 91 transplants from very young donors performed at our institution between 1984 and 1995. This included 59 single and 22 en bloc procedures involving first transplants and 7 single and 3 en bloc procedures involving retransplantation. Individual surgeon preference dictated the use of either the single or en bloc technique. Kidneys smaller than 6 cm tended to be transplanted en bloc, and lighter patients were generally given preference for receiving pediatric kidneys. Patients received sequential cyclosporine-based quadruple immunosuppression.

RESULTS

En bloc kidneys had a 1-year and 5-year graft survival of 82% and 70%, respectively. Single kidneys had a 1-year and 5-year graft survival of 64% and 40%. Kidneys that avoided acute rejection episodes and that were transplanted into heavier or male recipients had better long-term survival. Kidneys from donors less than 2 years old did poorly whether transplanted en bloc or singly. Better HLA matching improved short-term, but not long-term, graft survival, whereas cold ischemic time did not have statistically significant association with differences in graft survival. Eleven percent of the transplants had ureteral leaks, but only one kidney was lost. Ten transplants had vascular complications leading to graft loss, whereas two episodes of arterial stenosis were successfully treated with percutaneous angioplasty.

CONCLUSIONS

En bloc transplantation optimizes the outcome of transplantation with very young kidneys. We recommend induction therapy and cyclosporine immunosuppression with cyclosporine levels similar to adult target levels to minimize rejection episodes and, thus, improve outcome. These kidneys should be distributed nationally, because better HLA matching is associated with improved short-term graft survival. Our high ureteral leak rate indicates that alternatives to unstented ureteroneocystostomy should be considered.

Long-term results with single pediatric donor kidney transplants in adult recipients

PURPOSE

We investigated whether transplantation of single pediatric donor kidneys into adults leads to an increased incidence of functional allograft impairment and complications, as previously reported.

MATERIALS AND METHODS

To evaluate long-term functional outcome using single pediatric donor kidneys 60 adults (study group) who underwent transplantation between March 1973 and December 1988 using single pediatric donor kidneys 6 years old or younger (mean donor age plus or minus standard deviation 41.1 +/- 17.9 months) were compared to 58 matched adults (control group) who underwent transplantation with adult kidneys (mean donor age 29.7 +/- 10.8 years). The groups were identical for era of transplantation, recipient age, sex and followup (82 versus 83 months).

RESULTS

There was no difference in patient survival between the study and control groups (p = 0.26). In the study group there were an increased requirement for early dialysis (45 versus 24%, p = 0.02), a higher incidence of proteinuria (greater than 0.8 gm./24 hours, 67 versus 48%, p = 0.04) and a higher incidence of rejection within the first 6 months (80 versus 64%, p = 0.05). There was also an increased incidence of graft failure from acute rejection in the study group. Early differences in serum creatinine levels in the 2 groups dissipated after 3 months. Renal allograft histopathology revealed no significant difference in the incidence of focal segmental glomerulosclerosis in the study versus control groups after transplantation (22.9 versus 13.3%, p = 0.70). However, focal segmental glomerulosclerosis manifested sooner after transplantation in study than control patients (mean 37 versus 82 months). After transplantation proteinuria developed in study patients with focal segmental glomerulosclerosis at a mean of 4.6 months compared to 31.8 months in controls with post-transplant focal segmental glomerulosclerosis. Graft survival in the study group was superior when cyclosporine was given rather than conventional noncyclosporine based immunosuppression. Five-year graft survival rates were 48 versus 44% for cyclosporine treated and 33 versus 44% for conventionally treated study versus control patients.

CONCLUSIONS

These data suggest that with cyclosporine immunosuppression transplanting single pediatric kidneys into adults yields the same long-term functional graft outcome as adult donor kidneys.