Search result
Totally 33 trials in 29 publications were included among which there were 28 animal studies [8-35] and 1 clinical trial [36]. In addition, there are 4 on-going clinical trials registered on NLM.
Among 32 trials of animal studies, the animal models in 24 trials were rats, 7 were mice and 1 was rhesus macaques. A single method or a combination of multiple methods was used to induce DM, including streptozotocin (STZ) injection, high-fat diet (HFD) dietary induction, nephrectomy and natural development of models. However, the dosage and frequency of STZ injection, the timing of detecting establishment of DN were different. Although MSCs were used in all the included trials, the details of source, dosage, frequency, administration and point in time varied. The sources of MSCs were bone marrow mesenchymal stem cells (BM-MSCs) in 22 trials, adipose-derived stem cells (ADSCs) in 4 trials, human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) in 5 trials, exfoliated deciduous teeth stem cells in 1 trial. Allogeneic transplantation was used in 23 trials while xenoplastic transplantation was used in 8 trials and autologous transplantation was used in 1 trial. The characteristic of included animal trials was summarized in Figure 1A.
The only 1 clinical trial, the multicenter, randomized, double-blind, dose-escalating, sequential, placebo-controlled study, was finished in 2016. Two doses of allogeneic mesenchymal precursor cells were separately infused into 10 patients with type 2 diabetes and advanced DN, and the efficacy and adverse events were observed. The main features of the clinical trial were showed in Figure 1B.
In animal experiments, allogeneic transplantation was seen in 23 trials while xenoplastic transplantation was 8 trials, and autologous transplantation was 1 trial. The only 1 included clinical trial was allogeneic transplantation. None of them reported the occurrence of graft-rejection after transplantation, but 2 MSCs-treated patients developed antibodies specific to the donor HLA in the clinical trial, but one transiently occurred while the other presented at baseline and persisted throughout the observation period without the appearance of adverse events. But strangely, antibodies specific to the donor HLA were also found in one placebo-treated patient. Six animal experiments specified the deaths or dropouts. Lang et al reported 6 deaths of model rats during the construction of diabetes model [22] while Wang et al reported 1 death in both MSCs-treated group and DN group besides 2 deaths because of anesthesia [16]. In the study of Li et al, there was 1 rats dead in the DN group and 2 in the MSCs-treated group [27]. During a 12-week observation, the mortality in the MSCs-treated group (75.0%, 9/12) was lower than that in the DN-group (33.3%, 4/12) [28]. Similarly, Xian et al found 2 deaths in the hUCB-MSCs group, which was obviously less than the T1DM group (6 deaths) at the end of the study [29]. An et al found no marked change in the immune system of rhesus macaques in the hUCB-MSCs treatment for DN models [34].
Quality assessment
Quality assessment of animal experiments and clinical trial were performed Table 2A and Table 2B. Table 2A showed a number of “unclear” in the quality assessment of animal experiments, and especially, the outcome assessment in a random order, concealment of allocation and outcome assessors blinding in all included experiments stayed unclear, largely due to absent awareness of randomization and blind method in animal experiments. In Table 2B, a total of 7 scores suggested high methodological quality of the included clinical trial.
Assessment of glucose
Glucose was almost detected after the MSCs treatment, except for 2 studies [27, 32]. Sixteen studies measured glucose for once at the end of the experiment [13-16, 18-24, 26, 28-31]. Seven studies had conducted blood glucose monitoring at several points in time [9-12, 17, 25, 35]. Five trials, 7 trials, 5 trials, 12 trials, 17 trials, 7 trials and 2 trials were respectively included to assess the effect of reducing blood glucose level at 1 week, 2 weeks, 3 weeks, 1 month, 2 months, 3 months and 6 months, all of which showed great significant hypoglycemic effect in the MSCs-treated group (1-week: SMD=-1.484, 95%CI: -2.586 to -0.381, I²=80.6%, p<0.001; 2-week: SMD=-2.312, 95%CI: -3.743 to -0.882, I²=89.6%, p=0.002; 3-week: SMD=-1.484, 95%CI: -2.586 to -0.381, I²=80.6%, p<0.001; 1-month: SMD=-1.740, 95%CI: -2.660 to -0.821, I²=83.8%, p<0.001; 2-month: SMD=-1.83, 95%CI: -2.633 to -1.028, I²=86.0%, p<0.001; 3-month: SMD=-1.649, 95%CI: -2.838 to -0.461, I²=84.6%, p=0.007; 6-month: SMD=-3.045, 95%CI: -5.895 to -0.195, I²=76.4%, p=0.036). Total hypoglycemic effect was also analyzed (SMD=-1.954, 95%CI: -2.389 to -1.519, I²= 85.1%, p<0.001). (Figure 1)
Assessment of serum creatinine (SCr)
There were 4 trials, 2 trials and 5 trials included in the assessment of SCr at 1 month, 2 months and 3 months. All of them showed statistically significant lower creatinine value in the MSCs-treated group (1-month: SMD=-4.126, 95%CI: -7.936 to -0.315, I²=76.4%, p=0.034; 2-month: SMD=-3.506, 95%CI: -4.735 to -2.278, I²=1.8%, p<0.001; 3-month: SMD=-6.736, 95%CI: -10.311 to -3.162, I²=89.0%, p<0.001). Total effect on SCr was also analyzed, suggesting MSCs decreased the SCr and improved the renal function (SMD= -4.838, 95%CI: -6.789 to -2.887, I²= 90.8%, p<0.001). (Figure 2)
Assessment of blood urea nitrogen (BUN)
Five different timing points of BUN were evaluated with relatively few trials included in each. At 2 weeks (2 trials included), 3 weeks (2 trials included), 1 month (2 trials included), 2 months (3 trials included), and 3 months (4 trials included), BUN decreased in the MSCs-treated group, though no statistical significance was seen at 3 weeks and 1 month (2-week: SMD=-2.463, 95%CI: -3.292 to -1.634, I²=37.3%, p<0.001; 3-week: SMD=-4.432, 95%CI: -9.220 to -0.356, I²=92%, p=0.070; 1-month: SMD=-10.392, 95%CI: -21.247 to -0.464, I²=95.6%, p=0.060; 2-month: SMD=-3.389, 95%CI: -6.679 to -0.099, I²=89.8%, p=0.044; 3-month: SMD=-5.902, 95%CI: -8.988 to -2.815, I²=85.0%, p<0.001). Total effect on BUN was also analyzed, suggesting MSCs decreased the BUN (SMD= -4.912, 95%CI: -6.402 to -3.422, I²= 89.3 %, p<0.001). (Figure 3)
Assessment of creatinine clearance rate (CCr)
The data of six trials were pooled to evaluate the CCr at 2 months after MSCs treatment, and CCr could be seen decreased significantly in the MSCs-treated group when comparing to the DKD group (2-month: SMD=-1.881, 95%CI: -2.842 to -0.921, I²=79.7%, p<0.001). (Figure 4)
Assessment of blood insulin level
Two trials were included in the assessment of insulinemia. The insulin level increased at 3 months after MSCs treatment though the significance was not notable (3-month: SMD=3.051, 95%CI: -0.091 to 6.193, I²=90.3%, p=0.057).
Assessment of urine protein
The measurement of urine protein varied in the included studies. Microalbumin, urinary albumin excretion, urinary albumin/urinary creatinine ratio and urinary protein/creatinine ration were used to assess the urine protein excretion in the DKD animals.
Urinary albumin excretion at 1 month (2 trials included) and at 2 months (7 trials included) were observed lower in the MSCs-treated group than the DKD group, though no significance of the 1-month was seen (1-month: SMD=-6.507, 95%CI: -17.935 to 4.921, I²=98.3%, p=0.264; 2-month: SMD=-4.386, 95%CI: -5.891 to -2.881, I²=85.5%, p<0.001). Total effect on urinary albumin excretion was also analyzed, suggesting MSCs decreased the urinary albumin excretion (SMD= -4.830, 95%CI: -6.602 to -3.058, I²= 92.5%, p<0.001).
Microalbumin was detected at 3 weeks and 3 months, both of which had 2 trials satisfied the inclusion. Microalbumin was found decreased in the MSCs-treated group at 3 months (3-week: SMD=-9.112, 95%CI: -21.627 to 3.404, I²=95.3%, p=0.154; 3-month: SMD=-4.431, 95%CI: -5.771 to -3.091, I²=0.0%, p<0.001). Total effect on microalbumin was analyzed, suggesting the microalbumin was significantly lower in the MSCs-treated group than that in the DKD group (SMD= -5.791, 95%CI: -8.681 to -2.901, I²= 86.3%, p<0.001).
Urinary albumin/urinary creatinine ratio at 1 month (6 trials included) and at 2 months (10 trials included) were observed significantly lower in the MSCs-treated group (1-month: SMD=-2.419, 95%CI: -3.070 to -1.769, I²=0.0%, p<0.001; 2-month: SMD=-2.648, 95%CI: -3.454 to -1.842, I²=58.9%, p<0.001). Total effect on urinary albumin/urinary creatinine ratio was analyzed, which suggested that the urinary albumin/urinary creatinine ratio was significantly lower in the MSCs-treated group than that in the DKD group (SMD= -2.539, 95%CI: -3.075 to -2.003, I²=42.6%, p<0.001).
Urinary protein/creatinine ratio was found no statistical difference at 2 weeks (2 trials included) after MSCs treatment (SMD=-2.779, 95%CI: -7.617 to 2.059, I²=92.6%, p=0.260).
Assessment of kidney weight
Kidney weight and kidney weight/body weight ratio were used to assess the kidney hypertrophia. No significance was found on the kidney weight at 1 month (2 trials included) between two groups after MSCs treatment (SMD=-0.674, 95%CI: -2.052 to 0.704, I²=67.0%, p=0.337).
Kidney weight/body weight ratio was found significantly decreased in the MSCs-treated group at 2 months (8 trials included, SMD=-1.364, 95%CI: -2.164 to 0.565, I²=79.7%, p=0.001), while no statistical difference was found at 3 months (2 trials included, SMD=-10.012, 95%CI: -29.753 to 9.729, I²=97.0%, p=0.32) between two groups. Total effect on kidney weight/body weight ratio was analyzed, which suggested lower kidney weight/body weight ratio was found in the MSCs-treated group (SMD=-1.624, 95%CI: -2.594 to -0.655, I²= 86.9%, p=0.001).
Assessment of body weight
There were 3 trials and 5 trials included in the assessment of 1-month and 2-month body weight. No significance was found on 1-month body weight between two groups (SMD=2.634, 95%CI: -0.730 to 5.999, I²=95.5%, p=0.125). At 2 months, the body weight in the MSCs-treated groups significantly increased when compared to the DKD groups (SMD=0.869 95%CI: 0.442 to 1.296, I²=40.2%, p<0.001). Total effect of MSCs treatment on body weight was also analyzed (SMD=1.499, 95%CI: 0.461 to 2.536, I²= 87.3%, p=0.005).
Assessment of renal fibrosis
Four trials were included to evaluate the glomerulosclerosis% at 2 months after MSCs treatment, and no significance was found (SMD=-0.350 95%CI: -4.173 to 3.473, I²=96.2%, p=0.858).
TGF-β was detected at different points in time in different method. At 1 month (2 trials included) and 2 months (3 trials included) by PCR, and at 2 month (2 trials included) by WB, TGF-β was seen decreased significantly in the MSCs-treated group (1-month PCR: SMD=-3.258, 95%CI: -4.133 to -2.383, I²=4.2%, p<0.001; 2-month PCR: SMD=-7.594, 95%CI: -13.274 to -1.915, I²=93.6%, p=0.009; 2-month WB: SMD=-9.287, 95%CI: -11.322 to -7.252, I²=16.2%, p<0.001). Total expression of TGF-β was also analyzed (SMD=-6.839, 95%CI: -9.367 to -4.312, I²= 90.5%, p<0.001).
Col-I was detected by IHC and PCR. At 2 months by PCR (3 trials included), Col-I was significantly decreased (SMD=-11.468, 95%CI: -13.685 to -9.252, I²=41.3%, p<0.001) in the MSCs-treated group while no significance was found at 2 months by IHC (2 trials included) between two groups (SMD=-4.714, 95%CI: -10.670 to 1.242, I²=95.3%, p=0.121). Total expression of Col-I was also analyzed (SMD= -9.081, 95%CI: -14.233 to -3.929, I²= 95.1%, p=0.001).
Three trials were included to evaluate fibronectin (FN) by IHC at 2 months after MSCs treatment, and statistically significant decreased was found in the MSCs-treated group (SMD=-7.781, 95%CI: -10.680 to -4.881, I²=71.3%, p<0.001).
Two trials were included to evaluate α-SMA by WB at 1 month after MSCs treatment while 3 trials included at 2 months by PCR. Both of them were seen statistically significant decreased was found in the MSCs-treated group (1-month WB: SMD=-2.514, 95%CI: -3.550 to -1.479, I²=0.0%, p<0.001; 2-month PCR: SMD=-2.098, 95%CI: -3.721 to -0.476, I²=83.4%, p=0.011). Total effect of MSCs treatment on the expression of α-SMA was analyzed (SMD= -2.249, 95%CI: -3.311 to -1.186, I²= 72.1%, p<0.001).
E-cadherin was detected by WB at 1 month (2 trials included) after MSCs treatment, and it was found notable significance in decrease of E-cadherin deposition (SMD=3.600, 95%CI: -2.338 to 4.861, I²=0.0%, p<0.001).
Assessment of inflammatory mediator
Monocyte chemokine protein-1 (MCP-1) was detected by IHC at 2 months (2 trials included) after MSCs treatment, no significance was found between two groups (SMD=-8.913, 95%CI: -20.994 to 3.167, I²=93.1%, p=0.148).
TNF-α was detected by ELISA at 2 weeks (3 trials included) and by PCR at 1 month (2 trials included) after MSCs treatment, both of which were seen statistically significant decreased was found in the MSCs-treated group (2-week ELISA: SMD=-3.853, 95%CI: -7.207 to -0.499, I²=90.4%, p=0.024; 1-month PCR: SMD=-3.7279, 95%CI: -4.684 to -2.769, I²=57.5%, p<0.001). Total effect of MSCs treatment on the expression of TNF-α was analyzed (SMD= -4.027, 95%CI: -5.955 to -2.098, I²= 84.9%, p<0.001).
Risk of bias
Given the sufficient data to assess publication bias, 2-month blood glucose was used to measure. There was a bias prompted by moderate asymmetry of the funnel plot, and the Egger’s test showed p=0.013. However, Trim and Fill didn’t identify any missing study (Figure 5).