ALB and diabetic kidney disease: Urinary albumin excretion levels at 1 month (2 studies included) and at 2 months (7 studies included) were observed to be lower in the MSC-treated group than in the DKD group, although no significance at 1 month was observed (1 month: SMD = − 6.507, 95%CI − 17.935 to 4.921, p = 0.264; I2 = 98.3%; 2 months: SMD = − 4.386, 95%CI − 5.891 to − 2.881, p < 0.001; I2 = 85.5%).