Mesenchymal stem cells express major histocompability complex (MHC)Ⅰin low levels, but do not express MHC Ⅱ, so it has a low immunogenicity. It can block maturity of dendritic cells, depress immune response of T lymphocytes, and also mediate immune suppression by secreting several soluble cytokines. In light of these characters, mesenchymal stem cell can avoid allograft rejection in human and animal transplantation. It has been reported previously that human mesenchymal stem cells cultivated in growing rodent embryos can grew out of new kidney and ureter. Furthermore, urea nitrogen and creatinine levels were significantly higher in liquid collected from the new ureter compared with the animal serum levels, which suggested that the new kidney had generated urine. This native kidney has low immunogenicity, little side-effect after transplantation, extensive sources, so it may have wide space in self-kidney transplantation.

Bone marrow-derived mesenchymal stem cells (MSCs) have potentials of proliferation, multilineage differentiation and homing to injured tissue and organs. Therefore, many researchers consider them as seed cells and attempt to use them to repair injured tissues and organs. In the allo- even xero-transplantation of these seed cells, graft rejection is an important problem. A large amount of data show that MSCs have specific immune characteristics; they block dendritic cell maturation, decrease immune response of T cells, do not express class Ⅱ major histocompatibility complex molecules, and mediate immunosuppression by secreting some dissoluble factors. The specific low immunogenicity of MSCs could avoid rejection in xero-trensplantation for human and animals in vivo, showing advantages in treatment. Therefore, they are promising to be used as seed cells for kidney construction.

Acute kidney injury is a serious global health problem and determinant of morbidity and mortality. Recent advancements in the field of stem cell research raise hopes for stem cell-based regenerative approaches to treat acute kidney diseases. In this review, the authors summarized the latest research advances of the adult resident renal progenitor cells (ARPCs) on kidney repair, the role of ARPCs on tubular regeneration after acute kidney injury, the current understanding of the mechanisms related to ARPC activation and modulation, as well as the challenges that remain to be faced.

Objective CXCR4-overexpressing bone marrow-derived mesenchymal stem cells (CXCR4-BMSC) were constructed and co-cultured with hypoxia/re-oxygenation pretreated renal tubular epithelial cells (HR-RTEC).Repair of HR-RTEC was detected and the possible mechanism was also discussed.Methods CXCR4-BMSC (CXCR4-BMSC/eGFP,eGFP as the tracer gene) and null-BMSC (BMSC/eGFP) were obtained by gene transfection technique,and the level of CXCR4 in the transfected cells was detected.RTEC was cultured under hypoxia/re-oxygenation condition for 12 h,respectively,to obtain HR-RTEC,which was used to simulate AKI in vitro.BMSC and HR-RTEC were co-cultured for 12 h,and the proportion of apoptotic cells among the HR-RTEC was assayed by immunofluorescence technique.Western blot was used to test the protein levels of cleaved Caspase-3 and Bcl-2.The number of migrating BMSC was also assayed.After culturing with the HR-RTEC culture supernatant,the expression of cytokeratin 18 (CK18) in BMSC was tested by immunofluorescence staining.Cytokines including bone morphogenetic protein-7 (BMP-7),hepatic growth factor (HGF) and interleukin-10 (IL-10) in the BMSC culture supernatant were detected by ELISA method.Results Expression of CXCR4 was enhanced in CXCR4-BMSC.Proportions of the apoptotic cells among HR-RTEC after being co-cultured with BMSC,CXCR4-BMSC and null-BMSC were all decreased,especially in the C/H group.The decreased cleaved Caspase-3 and enhanced Bcl-2 were also observed in HR-RTEC.The number of migrating CXCR4-BMSC was the highest.Proportions of CK18+ cells in BMSC,CXCR4-BMSC and null-BMSC were all low and showed no difference.However,CXCR4 overexpression in BMSC stimulated secretions of BMP-7,HGF and IL-10.Conclusions CXCR4-overexpressing BMSC has more repair effect on the co-cultured HR-RTEC,the enhanced migration ability and secretion ability of CXCR4-BMSC are the possible mechanisms.

Objective To observe the effect of different calcium concentration peritoneal dialysate on calcium-phosphorus metabohsm in uremia patients under peritoneal dialysis. Methods Forty uremia patients who the first entered peritoneal dialysis were divided into two groups: standard calcium concentration group (20 cases), low calcium concentration group (20 cases). Treated with continuous ambulatory peritoneal dialysis (CAPD), combining with oral calcium carbonate, observing 12 months. Results When the first entering CAPD, serum calcium, phosphorus, calcium-phosphorus product, immunoreactive parathyroid hormone (iPTH) of the two groups had no differences. Hyperphosphatemia, lower iPTH were universal. After 6 months' treatment, hypercalcemia and hyperphosphatemia in standard calcium concentration group got increasingly serious.While in low calcium concentration group, serum calcium, phosphorus, calcium-phosphorus product all decreased significantly, moreover, they were also lower than post-treatment standard calcium concentration group(P<0.01). In the following 6 months, in low calcium concentration group,serum calcium, calcium-phosphorus product maintained at the normal level serum phosphorus also decreased to the normal level iPTH maintained about 150 ng/L. During the treatment, all patients had no hypotension and hyperspasmia. Conclusion Low calcium concentration peritoneal dialysate can ameliorate disorder of calcium-phosphorus metabohsm, delay the appearance of its comphcations.

Objective To investigate the effect of erythropoietin (EPO) on mesenchymal stem cells (mMSCs) proliferation under acute kidney injury (AKI) microenvironment,and to study its possible mechanism.Methods C57BL/6 mice's MSCs (mMSCs) were isolated by Percoll density gradient centrifugation and adherence cultivation.Surface markers were identified by flow cytometry.AKI mice models were made by clamping bilateral renal pedicles for 30 minutes and reopening for 30 minutes.Then both renal cortex was drew immediately to make IR kidney homogenate supernatant.P3-mMSCs were divided into different groups: Group A: low glucose DMEM medium with 10% fetal bovine serum; Group B: low glucose DMEM medium with 10% fetal bovine serum plus IR kidney homogenate supernatant; Group C: low glucose DMEM medium with 10% fetal bovine serum plus IR kidney homogenate supernatant and different concentrations of EPO (1,5,10,50 U/ml).Each group was incubated for 1 d,3 d,5 d,7 d.Proliferation of mMSCs was detected by CCK-8,and apoptosis was detected by TUNEL.The protein expression of erythropoietin receptor(EPOR) and the proteins of proliferation/apoptosis related signal pathway were examined by Western blotting.Results Under IR kidney homogenate supernatant,the proliferation ability of mMSCs decreased significantly (P＜0.01),while the apoptoic percentage was significantly higher than that of Group A (P＜0.01).After intervention of EPO,mMSCs proliferation enhanced,at the same time,the apoptoic percentage decreased,in a dose-dependent manner.EPOR was positive in P3-mMSCs by Western blotting.EPO decreased the expression of caspase-3 in mMSCs under AKI microenvironment in a dose- and time-dependent manner,but increased the expression of Bcl-2.Cultured for 5 d,the expression of phosphor-Janus kinase2(p-JAK2) [(0.641 ±0.028) vs (0.456±0.012)] and phosphor-signal transducer and activator of transcription(p-STAT5)[(0.398±0.016) vs (0.209±0.020)] was significantly higher in 10 U/ml EPO group compared to group B.Conclusion Erythropoietin can promote proliferation of mMSCs in vitro under AKI microenvironment,which is mediated by EPOR and related with proliferation/apoptosis signal pathway.

Objective To investigate the migration of bone-marrow mesenchymal stem cells (BMSCs) under acute kidney injury (AKI) microenvironment in vitro and the effect of erythropoietin (EPO) intervention,and to explore its underlying mechanism.Methods Renal tubular epithelial cells (RTECs) were cultured in hypoxia/re-oxygenation (HR) condition for 12 h,respectively,in order to establish HR-RTEC.BMSCs and RTECs were co-cultured by Transwell system and were divided into 7 groups:control group (group①,only BMSC cultured),BMSC-RTEC co-culturing group (group ②),BMSC-HR-RTEC co-culturing + EPO intervention groups (group ③to group ⑦,EPO concentration:0,1,5,10,50 IU/ml).All the groups were cultured for 48 h and the number of migrating BMSCs was detected.Western blotting was applied for the detection of SDF-1 expression in RTECs and pMAPK and MAPK levels in BMSCs.SDF-1 concentration in the RTECs culture supernatant was tested by ELISA.Results The number of BMSCs migrating to the low chamber where HR-RTECs were cultured was increased,and EPO intervention further enhanced this migration which reached the peak at the concentration of 10 IU/ml [Compared with group③,(46.67±7.37) cells vs (19.00±2.37) cells,P ＜ 0.05].Intracellular expression level and the secreated level of SDF-1 in HR-RTECs in group③ were higher than those in RTECs of group② [0.37±0.01 vs 0.19±0.01,P ＜ 0.05; (61.64±4.88) μg/L vs (35.26±8.78) μg/L,P ＜ 0.05].EPO intervention increased above SDF-1 levels and reached the peak at the concentration of 10 IU/ml [group⑥ vs group③:(173.53± 14.66) μg/L vs (61.64±4.88) μg/L,P＜0.05],accompanied with enhanced phosphorylation of MAPK in BMSCs.Conclusions AKI microenvironment has obvious chemotaxis effect on BMSCs,and EPO intervention can strengthen this effect.The increased SDF-1 level and enhanced phosphorylation of MAPK,the downstream signal protein of SDF-1/CXCR4 axis,are the possible mechanism for EPO performance.

Objective To observe the changes of CD4+CD25+ regulatory T cells, Foxp3 mRNA and soluble interlukin 2 receptor (sIL-2R) in the peripheral blood of kidney transplantation recipients and to evaluate their effect on the diagnosis of acute rejection. Methods Forty-two renal transplant recipients and 30 healthy controls were enrolled in this study. CD4+CD25+ regulatory T cells proportion, Foxp3 mRNA and sIL-2R of pre-transplantation and those of day 7,14, 28, 56 of post-transplantation were measured by flow cytometer, fluorescent quantization PCR and enzyme-linked immunosorbent assay (ELISA), respectively. Biochemistry appliance was used to detect serum creatinine. The diagnosis of acute rejection in transplanted kidney was based on the clinical symptoms, the laboratory examinations, Doppler ultrasound and biopsy. Results (1)At day 7, 14, 28, 56 of post-transplantation, CD4+CD25+ regulatory T ceils proportion, Foxp3 mRNA level in acute rejection group were significantly decreased compared with those in non-acute rejection group. (2) There were significant differences of peripheral blood CD4+CD25+ regulatory Tcells[(9.22±3.53)% vs (6.09±1.99)%, P<0.01], Foxp3 mRNA[(0.82±0.36)×10-3 vs (0.50±0.28)×10-3, P<0.01] and sIL-2R levels [(856.30±108,24) U/ml vs (247.35±11.24) U/ml, P<0.01]between patients of pre-transplantation and healthy control group. (3)Plasma CD4+CD25+ regulatory T cells [(16.53±4.14)%] and the expression of Foxp3 mRNA [(4.97±1.94)×10-3] was significantly increased, but sIL-2R level [(463.72±31.23) U/ml] was significantly decreased as the transplanted renal function was restored (all P<0.01). (4) Plasma CD4+CD25+regulatory T cells [(12.18~2.86)%] and the expression of Foxp3 mRNA [(3.15±1.22)×10-3] was significantly decreased (P<0.01), and sIL-2R level [(748.36±115.41) U/ml] was significantly increased (P<0.01) when acute rejection occurred. The above changes had an earlier onset than the change of Scr. (5)The percentage of CD4+CD25+ regulatory T cells was positively correlated with the Foxp3 mRNA level (P<0.01), but was not correlated with sIL-2R level in all the patients. Conclusion The measurement of these markers in peripheral blood may be an important guideline to the diagnosis and prognosis of acute rejection in renal transplant recipients.