Employment of mesenchymal stem cells (MSCs) therapy represents an emergent strategy in neuro-urology field. Although this approach holds promise for management of neurogenic bladder (NGB), issues such as suitable sources and administration route of these cells as well as possible unknown side effects need more investigations. The possible effect of intrathecal administration of SCs in repairing central nervous has been raised, however, the efficacy of these cells on the recovery of NGB following spinal cord injury (SCI) especially in direct intra-bladder transplantation is not clearly documented. Here, we aimed to investigate whether intra bladder wall autologous bone marrow mesenchymal SC (BM-MSCs) transplantation, as a minimally invasive method, could able to improve NGB following SCI model in female rats.

A total of 42 adult female Wistar rats (weighing 220-260 g) were divided into 6 groups (n = 7 in each) as below; control, sham operated (sham), complete transection SCI (cSCI), hemisection SCI (hSCI), cSCI + BM-MSCs and hSCI + BM-MSCs groups. Control group didn’t receive any intervention, rats in sham group underwent T9 laminectomy by a posterior midline approach without spinal cord damage; In cSCI and hSCI rats, after laminectomy at the T9 vertebral level, either a T9 spinal cord hemisection on the left of the spinal cord or a T9 complete transection with a sharp blade visually was conducted and then they received injection of normal saline into bladder wall 4 weeks post injury. Animals in cSCI + BM-MSCs and hSCI + BM-MSCs groups received 1×106/120µl injection of BM - MSCs into 6 areas of bladder wall, 4 weeks post injury. Urodynamics study was used to evaluate the changes in bladder function in study groups 4 weeks post cell transplantation in all groups.Surgical procedure in the current experiment for laminectomy process, cell transplantation, and catheters implementation are illustrated in Figure 1. Animals were sacrificed by over dose of Ketamie/Xylazine after urodynamic assessment. DNA fragmentation (a marker of apoptotic cell death) was determined by using the In Situ Cell Death Detection Kit (Cat. No. 11 684 817 910, Roche Molecular Biochemicals) according to the manufacturer's instructions. Also, differentiation of the injected BM-MSCs to smooth muscle Brain-derived neurotrophic factor (BDNF) and c-Fos expression were assessed at the end of experiment. Statistical analysis was performed by using one-way analysis of variance (ANOVA) and Tukey adjustment method for post-hoc comparison. The significance was set as P < 0.05. SPSS 16.0 software (SPSS Inc., Chicago, Illinois, USA) was used for statistical analyses.

As urodynamics study findings showed cSCI and hSCI resulted in overactive bladders, while BM-MSCs transplantation only was able to reduce the amplitude of the uninhibited contraction in cSCI + BM-MSCs. Furthermore, the compliance and residual volume were recovered only in the hSCI + BM-MSCs group. The number of apoptotic (TUNEL positive cells) was increased after SCI induction in bladder tissue. In contrast, transplantation of the BM-MSCs decreased the number of TUNEL-positive cells in the SCI-induced rats. However, only in hSCI-MSC group it was statistically significant (p<0.05) (Fig.2.). In the present study, c-Fos expression was increased after SCI in the bladder and was suppressed by transplantation of the BM-MSCs . In our study, endogenous BDNF levels in the bladder were unchanged statistically after BM-MSCs transplantation. In the treated groups with BM-MSCs, transplanted cells expressing immunoreactivity against SMA were found, indicating that BM-MSCs differentiated into smooth muscle cells. The merged cells expressing yellow fluorescence was doubly positive for human mitochondria antigen and SMA, indicating that they were from BM-MSCs. increment of c-Fos expression in the bladder centers represented neuronal activation by overactive bladder in this study and it decreased significantly after treatment in both hSCI + BM-MSCs and cSCI + BM-MSCs groups (p<0.05) .

Neuro-regeneration in stem cell therapy to correct bladder dysfunction is a logical and promising strategy. According to the data from our study, the administration of stem cells could repair SCI-induced NGB by engaging various cellular mechanisms such as the promotion of cellular dynamics and differentiation into various lineages.

Our study added a notion that urinary dysfunction associated with SCI was improved following direct injection of autologous BM-MSC transplantation into bladder wall in the chronic phase of SCI injury.

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