Biology subjects

Drummond, N. J.

Publications and source records attributed to Drummond, N. J..

3 recordsLinked to original sources

bioRxiv2026

Immunological responses to hydrogel-aided induced pluripotent stem cell-derived dopaminergic progenitor transplants in immunodeficient versus cyclosporine immunosuppressed rats.

The success of stem cell-derived brain repair for Parkinsons is limited by the variable survival and poor maturation of dopaminergic progenitors after transplantation into the Parkinsonian brain. One approach that has been developed to improve this is engraftment of the cells within a neurotrophin-enriched collagen hydrogel. Although this has been shown to improve progenitor survival and maturation in athymic nude rats, the same beneficial effects of the hydrogel were not seen in cyclosporine immunosuppressed rats. To determine the reasons for these differences, the aim of this study was to assess the local and systemic immune responses to progenitor transplantation in these two recipient groups. To do so, human induced pluripotent stem cell-derived dopaminergic progenitors were transplanted into 6-hydroxydopamine-lesioned striatum of athymic or cyclosporine immunosuppressed rats. The cells were transplanted either alone, with the neurotrophins GDNF and BDNF, in an unloaded collagen hydrogel, or in a neurotrophin-loaded collagen hydrogel. Post-mortem assessment included both graft site and blood analysis of immune cell populations. As expected, nude rats showed a pronounced innate immune cell response at the graft site but no T-cell recruitment or activation locally or systemically. In contrast, while the immunosuppressed rats also showed the expected innate immune cells response to the transplant, there was also infiltration of CD4+ and CD8+ T cells at the site of transplantation as well as circulating activated T-cells. Thus, this study suggests that the benefits of the hydrogel that were seen in the athymic nude rats did not manifest in the cyclosporine immunosuppressed rats due to incomplete immunosupression. This study shows the importance of careful optimisation of the immunosuppressive regime chosen before xenotransplantation experiments.

neuroscience↗

bioRxiv2020

Cryopreservation of midbrain dopaminergic neural cells differentiated from human embryonic stem cells

Recent advancements in protocols to differentiate human pluripotent stem cells into midbrain dopaminergic (mDA) neurons has improved the ability to model Parkinsons disease (PD) in a dish, and has provided a scalable source of donor cells for emerging PD cell replacement therapy (CRT). However, to facilitate reproducibility, collaboration, and clinical trials it would be highly beneficial to cryopreserve committed mDA neural precursors cells in a ready-to-use format. In terms of cell manufacturing for PD CRT trials, a cryopreserved transplantation-ready mDA cell product would provide a critical opportunity for quality control, efficacy testing, and safety assessments. To address this challenge, we have compared six (6) different clinical-grade cryopreservation media and different freezing conditions for mDA neural precursor cells differentiated from two human embryonic stem cell (ESC) lines, MasterShef7 and RC17. Significant differences in cell viability were observed at 24h post-thawing, but no differences were observed immediately upon thawing. This highlights the need to check cell viability over the first 24h after thawing, and that viability of freshly thawed cells is insufficient to gauge the success of a cryopreservation protocol. Considerable apoptosis occurs in the first 24h post-thawing, and significant differences between cryopreservation procedures were only revealed during this time period. The presence of ROCK inhibitors improved cell viability at 24h for all conditions tested. A faster cooling rate of 1-2{degrees}C/min was significantly better than 0.5{degrees}C/min for all conditions tested, while rapid thawing at 37{degrees}C was not always superior to slow thawing at 4{degrees}C. Indeed, the optimal cryopreservation and thawing conditions in this study, as determined by 24h post-thaw viability, were cells frozen in PSC Cryopreservation medium at a cooling rate of 1{degrees}C/min and slow thawing at 4{degrees}C. These conditions permitted recovery of 60%-70% live cells at 24h with respect to the starting number of cryopreserved cells. Importantly, cryopreservation of mDA neural precursor cells did not alter their potential to resume differentiation into mDA neurons. HighlightsO_LIFirst systematic comparison of multiple clinical-grade cryopreservation media for human ESC-derived mDA neural precursor cells C_LIO_LIDifferences in cell viability were observed at 24h after thawing, but not immediately upon thawing C_LIO_LICooling rates of 1{degrees}C/min or 2{degrees}C/min were significantly better than 0.5{degrees}C/min for all cryopreservation conditions tested C_LIO_LIA slow thawing condition at 4{degrees}C was significantly better than quick thawing at 37{degrees}C for cells frozen in PSC Cryopreservation medium C_LIO_LICryopreservation of mDA cells does not significantly alter their potential to differentiate into mDA neurons C_LI

cell biology↗

bioRxiv2017

A novel mitochondrial enriched antioxidant protects neurons against acute oxidative stress

Excessive reactive oxygen species (ROS) can damage proteins, lipids, and DNA, which result in cell damage and death. The outcomes can be acute, as seen in stroke, or more chronic as observed in age-related diseases such as Parkinsons disease. Here we investigate the antioxidant ability of a novel synthetic flavonoid, Proxison (7-decyl-3-hydroxy-2-(3,4,5-trihydroxyphenyl)-4-chromenone), using a range of in vitro and in vivo approaches. We show that, while it has radical scavenging ability on par with other flavonoids in a cell-free system, Proxison is orders of magnitude more potent than natural flavonoids at protecting neural cells against oxidative stress and is capable of rescuing damaged cells. The unique combination of a lipophilic hydrocarbon tail with a modified polyphenolic head group promotes efficient cellular uptake and mitochondrial localisation of Proxison. Importantly, in vivo administration of Proxison demonstrated effective and well tolerated neuroprotection against oxidative stress in a zebrafish model of dopaminergic neuronal loss.

cell biology↗