Abstract
Spina bifida is a congenital anomaly that is caused by incomplete closure of the neural tube before birth and it affects as many as 1 in 1000 births in the United States. Spina bifida typically leads to lifelong medical complications and decreased quality of life. Recent advances in surgical techniques have allowed for the use of in utero surgeries repairing the spinal cord defect before the fetus is born, however the damage from spina bifida is a permanent spinal cord injury and current surgeries only offer functional improvement in about forty percent of patients. Addition of chorionic villus mesenchymal stem cells derived from human placenta (P-MSCs) in a hydrogel scaffold covering the spinal cord followed by the in utero surgical repair has shown significant improvements in spinal cord recovery and function in a sheep model. While this repair model using P-MSCs holds great promise, the mechanism through which PMSCs rescue neurons in the spinal cord remains unknown. MSCs have been shown to rescue tissues and cells of various organs through paracrine secretions and modulations of the immune system particularly through the secretion of exosomes. P-MSCs are not the only attractive option for autologous in utero intervention as MSCs can also be obtained on a similar timeline from amniotic fluid (AF-MSCs). This project sought to compare differences in secreted proteins and exosomes of AF-MSCs and P-MSCs as well as their functional neuroprotective abilities. In order to do this AF-MSCs and P-MSCs were isolated from donor-matched tissues donated from v patients at the UC Davis Medical Center. To eliminate variability in secretion due to genetic differences between donors AF-MSCs and P-MSCs were isolated from the same donor. Following AF-MSC and P-MSC isolation, all cell lines were characterized as MSCs by the use of a positive and negative marker MSC flow cytometry panel, Adipogenic and Osteogenic differenentiation, and by growth kinetics. Following positive characterization of cell lines as MSCs, conditioned media was collected and analyzed for secreted proteins by ELISAs and proteome arrays. ELISAs showed an almost three-fold increase in BDNF secreted by AF-MSCs over P-MSCs, while there was almost no VEGF or HGF secretion by AF-MSCs, contrasting with robust secretion of both VEGF and HGF by P-MSCs. Angiogenesis and Cytokine proteome array panels were able to identify differences in five other proteins. Exosomes were successfully isolated by ultracentrifugation and characterized by western blot and nanotracker assay. Exosome proteomics identified almost 1100 proteins contained in the exosomes , but despite some minor differences gene ontology and pathway analysis showed the total protein content of exosomes to be almost functionally identical between AF-MSCs and P-MSCs. AF-MSCs cultured in an indirect co-culture system increased growth an neurite formation of staurosporin damaged SH-SY5Y more than P-MSCs. Both AF-MSCs and P-MSCS exhibited a substantial increase in neurite formation and growth over unprotected cells. Future research should focus on the potential role of the differentially secreted proteins and the role of exosomes on neuroprotective function.