Reestablishing Brain Networks In Patients With End-Stage Renal Disease After Kidney Transplantation

Objective To explore alteration patterns of the resting-state brain networks after successful kidney transplantation in patients with end-stage renal disease (ESRD) by using independent component analysis method (ICA) and to further uncover the pathophysiological mechanisms underlying cognition changes of ESRD patients following kidney transplantation (KT).Materials and Methods Twenty-three ESRD patients who planned to undergo KT and 22 healthy subjects were included. All subjects underwent resting-state functional MRI scan (rs-fMRI) and psychological tests. Patients underwent the rs-fMRI scan and the psychological evaluation for three times:before transplantation and 1 month.6 months after KT. Seven resting sub-networks including default mode netwok (DMN), dorsal attention network (DAN), central executive network(CEN),self-referential network (SRN), somato-motor network (SMN), visual network (VN), and auditory network(AN) of each subject were identified by using ICA. One sample t test was used to explore the spatial patterns of resting-state sub-networks in each group. For comparing the functional connectivity of the resting-state networks of different groups, two-sample t tests or paired t tests were used. Thus the dynamic changes of each network were obtained. We also evaluated the relationship between the intergroup functional connectivity and results of neuropsychological or laboratory tests by using correlation analysis.Results Two samples t test or paired t test did not find any intergroup difference for the SRN. Compared with normal controls, all other six resting state sub-networks including DMN, DAN, CEN, SMN, AN, and VN showed decreased functional connectivity before KT. One month after KT, patients showed decreased functional connectivity in the DMN, CEN, SMN, AN, and VN. Decreased and increased functional connectivity was found for the DAN. After six months, the patient group did not show statistical functional connectivity for the DAN, CEN, AN, and VN when compared with normal controls. Both decreased and increased functional connectivity were found for DMN and SMN. Compared with patient group before KT, patients in the one month after KT group exhibited significantly increased functional connectivity in the DMN, DAN, CEN and SMN. No statistical change was found for AN and VN. All six sub-networks demonstrated increased functional connectivity for the patient group six months after KT when compared with pre-KT group. Compared with patients one month after KT group, the patients six months after KT showed both increased and decreased functional connectivity in the DMN and CEN. Only increased functional connectivity was found for the AN. Functional connectivity of DAN, SMN, and VN did not show statistical changes.The correlation analysis results found that the functional connectivity changes of the left superior parietal gyrus in the DAN between one-month after and pre-KT negatively correlated with the change of SDS and creatinine levels, the change in creatinine levels also negatively correlated with the functional connectivity changes in the right inferior frontal gyrus and right precentral gyrus. The changes of the left middle frontal gyrus in the DAN between six months after KT and pre-KT negatively correlated with the change of SDS; the functional connectivity changes of the left superior parietal gyrus also negatively correlated with the changes of the urea and creatinine. The changes of the right precentral gyrus in the SMN between six months after KT and pre-KT negatively correlated with the change of LTT.Conclusion The recovery patterns of seven resting state sub-networks differ from each other, which may be the neural basis of different cognition function recoveries following KT. The rapidly decreased levels of serum creatinine and urea may be associated with the functional changes in these networks.Objective A great many studies have demonstrated that the human brain shows small-worldness nature, which may be altered by various diseases. So far, no study is focus on the influence of kidney transplantation on the brain topological architectures. This study aimed to find out the small-world topological feature of functional and structural networks changes in patients one month and six month following kidney transplantation (KT).Materials and methods Twenty-one end-stage renal disease (ESRD) patients who planned to undergo KT and 21 healthy controls were included. All participants were right-handedness. All subjects underwent resting-state functional MRI scan (rs-fMRI) and a series of psychological tests. Patients underwent the rs-fMRI scan and the psychological evaluation for three times:before KT and 1 month,6 months after KT. Laboratory examination was also performed in the patient group. Graph theory was used to explore the characteristics of complex brain networks from the perspectives of function and structure in patients before, one month and six months after KT. Two samples t test or paired t test were used to compare the inter-group differences of overall small-world topological properties and nodal characteristics.Results ESRD patients before.one month and six months after KT and the control groups showed small-world features, however, differences were found for some properties between groups. ESRD patients had decreased clustering coefficient (Cp), local efficiency (Eloc) and global efficiency (gE), while increased shortest path length (Lp) at some sparsity thresholds in both the functional and structural networks. Cp, gE, and locE was lower and Lp was higher in patients one month after KT than the controls for the functional network. In the structural network, patients in the one month after KT group showed decreased Cp, Eloc and increased Lp, while no difference was found for the gE. No group difference was found for the patient group after six months and the controls. The gE and Eloc in the structural network of patients with KT after six months were increased compared with pre-transplantation and one month after KT. Significant difference was found for the nodal characteristics between groups. For the functional network,compared with normal controls, the left supplementary motor area (SMA) and cuneus in ESRD patients before and one month after KT showed increased node degree (Si) and node efficiency (Ei); left parahippocampus, SMA, and cunesu in the patient group six months after KT showed increased Si and Ei. Compared with the patients before KT, patients in the one and six months after KT showed decreased Si and Ei in the orbital part of left superior frontal gyrus. Patients with KT after six months showed increased Si and Ei in the functional network. In the structural network, Si and Ei in the ESRD patients before, one and six months after KT were decreased compared with the controls. Increased Si and Ei were observed for the patients one and six months after KT compared with pretransplantation. Both decreased and increased Si was observed for the patients six months after KT compared with that one month after KT. Only increased Ei was observed for the patients six months after KT compared with that one month after KT.Conclusion This study first found that altered small-word properties were found for the patient before KT and one month after KT. Different network properties showed different recovery patterns after KT. The recovery of both functional and structural brain networks may be time-dependent. This may provide imaging evidence for the different cognition function recovery after KT.