Mesenchymal Stem Cells Home to but do not Modulate Acute Renal Injury in a Canine Model

Abstract

Background: Acute kidney injury (ARI) is a common clinical event that occurs in 5-35% of all hospitalizedpatients and is associated with a two-to five fold increased mortality risk., with no significant improvement on pharmacologic therapy. The need for better treatment strategies for ARI called for cellular based strategies aiming to regenerate damaged tissues. Mesenchymal stem cells (MSCs) hold special promise in attenuating kidney injury, since nephrons are largely of mesenchymal origin. Objectives: The objective of this study is to evaluate the role of bone marrow derived (MSCs) in regeneration of post-ischemic acute renal injury in mongrel dogs. Material and Methods: Fifteen adult male mongrel dogs were used in this study. Animals were divided into: Group I, normal group (3 dogs); Group II, nine dogs subjected to ischemic/reperfusion injury (IRI) by clamping both renal pedicles for 60 minutes and not subjected to stem cell therapy which were further divided into: 6 dogs without sham injection, 3 sacrificed 3 days and 3 after 7 days after IRI and 3 dogs with sham injection sacrificed 7 days after IRI. and Group III (3 dogs) which underwent IRI and received systemic autologous MSC injection. This group underwent aspiration of 15-20 ml bone marrow from posterior iliac spine, mononuclear cell separation and MSC separation. MSCs were tagged by iron oxide and injected in a dose of 2million /kg systemically through the femoral vein. Evaluation of Therapeutic Effect: 1. Functional evaluation of renal functions using serum creatinine preoperative and 30 minutes, 1 day, 2days, 4days, 7days postoperative.2. Renal histology and injury scores: using H&E, PAS using morphometry. 3. Tracing of injected MSCs (homing) in renal tissues using Prussian blue staining . 4. Immunohistochemical evaluation of the apoptosis and proliferative capacity of MSCs using caspase3 and KI 67. Results: Bone marrow derived MSCs were found in the renal cortex and medulla, epithelial lining of the cortical tubules, glomeruli, the Bowman's space, in some peritubular capillaries and among the epithelial lining of the renal tubules of treated animals. However,MSCs did not undergo transdifferentiation to renal cells, There was no difference in the regeneration, apoptosis or proliferation between treated and nontreated animals. Conclusions: Injected MSCs homed to but did not affect regeneration of renal tissue after acute injury. Although MSCs did not prove to differentiate into renal tissue, they can be used as vehicles for cytokines or growth factors as they home to injured sites.