Sleeping Beauty transposon system for GDNF overexpression of entrapped stem cells in fibrin hydrogel in a rat model of Parkinson's disease.

There is currently no causal treatment available for Parkinson's disease (PD). However, the use of glial cell line-derived neurotrophic factor (GDNF) to provide regenerative effects for neurons is promising. Such approaches require translational delivery systems that are functional in diseased tissue. To do so, we used a non-viral Sleeping Beauty (SB) transposon system to overexpress GDNF in adipose tissue-derived mesenchymal stromal cells (adMSCs). Entrapment of cells in fibrin hydrogel was used to boost potential neurorestorative effects. Functional GDNF-adMSCs were able to secrete 1066.8 ± 169.4 ng GDNF/120,000 cells in vitro. The GDNF-adMSCs were detectable for up to 1 month after transplantation in a mild 6-hydroxydopamine (6-OHDA) hemiparkinson male rat model. Entrapment of GDNF-adMSCs enabled GDNF secretion in surrounding tissue in a more concentrated manner, also tending to prolong GDNF secretion relatively. GDNF-adMSCs entrapped in hydrogel also led to positive immunomodulatory effects via an 83% reduction of regional IL-1ß levels compared to the non-entrapped GDNF-adMSC group after 1 month. Furthermore, GDNF-adMSC-treated groups showed higher recovery of tyrosine hydroxylase (TH)-expressing cells, indicating a neuroprotective function, although this was not strong enough to show significant improvement in motor performance. Our findings establish a promising GDNF treatment system in a PD model. Entrapment of GDNF-adMSCs mediated positive immunomodulatory effects. Although the durability of the hydrogel needs to be extended to unlock its full potential for motor improvements, the neuroprotective effects of GDNF were evident and safe. Further motor behavioral tests and other disease models are necessary to evaluate this treatment option adequately.

Transposon-mediated glial cell line-derived neurotrophic factor overexpression in human adipose tissue-derived mesenchymal stromal cells: A potential approach for neuroregenerative medicine?

Glial cell line-derived neurotrophic factor (GDNF) has neuroprotective effects and may be a promising candidate for regenerative strategies focusing on neurodegenerative diseases. As GDNF cannot cross the blood-brain barrier to potentially regenerate damaged brain areas, continuous in situ delivery with host cells is desired. Here, a non-viral Sleeping Beauty transposon was used to achieve continuous in vitro overexpression of GDNF in immune-privileged human adipose tissue-derived mesenchymal stromal cells (GDNF-tASCs). In addition, in vivo survival, tolerance, and effectiveness of transfected cells were tested in a very mild 6-hydroxydopamine (6-OHDA)-induced dopamine depletion rat model by means of intrastriatal injection on a sample basis up to 6 months after treatment. GDNF-tASCs showed vast in vitro gene overexpression up to 13 weeks post-transfection. In vivo, GDNF was detectable 4 days following transplantation, but no longer after 1 month, although adipose tissue-derived mesenchymal stromal cells (ASCs) could be visualized histologically even after 6 months. Despite successful long-term in vitro GDNF overexpression and its in vivo detection shortly after cell transplantation, the 6-OHDA model was too mild to enable sufficient evaluation of in vivo disease improvement. Still, in vivo immunocompatibility could be further examined. ASCs initially induced a pronounced microglial accumulation at transplantation site, particularly prominent in GDNF-tASCs. However, 6-OHDA-induced pro-inflammatory immune response was attenuated by ASCs, although delayed in the GDNF-tASCs group. To further test the therapeutic potential of the generated GDNF-overexpressing cells in a disease-related context, a follow-up study using a more appropriate 6-OHDA model is needed.