Comparison of fresh and cryopreserved porcine ventral mesencephalon cells transplanted in A rat model of Parkinson's disease

The immunological challenges of cell transplantation for the treatment of Parkinson's disease

Dopaminergic cell transplantation is an experimental therapy for Parkinson's disease (PD). It has many potential theoretical advantages over current treatment strategies such as providing continuous local dopaminergic replenishment, eliminating motor fluctuations and medication-induced dyskinesias, slowing down disease progression or even reversing disease pathology in the host. Recent studies also show that dopaminergic cell transplants provide long-term neuromodulation in the basal ganglia that simulates the combined effects of oral dopaminergic therapy and surgical therapies like deep brain stimulation, the contemporary therapeutic approach to advanced PD. However, dopaminergic cell transplantation in PD as not been optimized and current experimental techniques have many drawbacks. In published experiments to date of attempted dopaminergic grafting in PD, the major challenges are unacceptable graft-induced dyskinesias or failure of such grafts to exceed the benefits afforded by sham surgery. A deleterious host immune response to the transplant has been implicated as a major putative cause for these adverse outcomes. This article focuses on recent advances in understanding the immunology of the transplantation in PD and possible methods to overcome adverse events such that we could translate cell replacement strategies into viable clinical treatments in the future.

Cell-based therapeutic approaches for Parkinson's disease: progress and perspectives

Motor dysfunctions in Parkinson's disease are believed to be primarily due to the degeneration of dopaminergic neurons located in the substantia nigra pars compacta. Because a single-type cell population is depleted, Parkinson's disease is considered a primary target for cell replacement-based therapeutic strategies. Extensive studies have confirmed transplantation of donor neurons could be beneficial, yet identifying an alternative cell source is clearly essential. Human embryonic stem cells (hESCs) have been proposed as a renewable source of dopaminergic neurons for transplantation in Parkinson's disease; other potential sources could include neural stem cells (hNSCs) and adult mesenchymal stem cells (hMSCs). However, numerous difficulties avert practical application of stem cell-based therapeutic approaches for the treatment of Parkinson's disease. Among the latter, ethical, safety (including xeno- and tumor formation-associated risks) and technical issues stand out. This review aims to provide a balanced and updated outlook on various issues associated with stem cells in regard to their potential in the treatment of Parkinson's disease. Essential features of the individual stem cell subtypes, principles of available differentiation protocols, transplantation, and safety issues are discussed extensively.

Principles and practical issues for cryopreservation of nerve cells

Nerve cells isolated from the brain have a number of research and clinical applications, not the least of which is their transplantation to patients with Parkinson's disease. Neural primary and precursor cells of several areas of the brain are potential candidates for transplantation and research. However, supply of suitable tissue is one of the major problems associated with the widespread application of such techniques. The ability to store such tissue for prolonged periods would greatly alleviate this problem. Cryopreservation allows indefinite storage, provided the storage temperature is sufficiently low. Whilst many of the potentially usable cell types have been shown to be capable of surviving cryopreservation to some degree, survival post-thaw needs to be considerably improved. Cryopreservation techniques applied to date are mostly crude and often adopted from those used for unrelated cell types. Studies involving cryopreservation of primary neural cells and stem cells are reviewed, the basic principles of cryopreservation explained and suggestions made for improvements to the low temperature storage of these cells.

Transplantation of hypocretin neurons into the pontine reticular formation: preliminary results

STUDY OBJECTIVES

The sleep disorder narcolepsy is now considered a neurodegenerative disease because there is a massive loss of neurons containing the neuropeptide, hypocretin, and because narcoleptic patients have very low cerebrospinal fluid levels of hypocretin. Transplants of various cell types have been used to induce recovery in a variety of neurodegenerative animal models. In models such as Parkinson disease, cell survival has been shown to be small but satisfactory. Currently, there are no data indicating whether hypocretin neurons can survive when grafted into host tissue. Here we examined the survival of hypocretin-containing neurons grafted into the pontine reticular formation, a region traditionally regarded to be key for rapid eye movement sleep generation.

DESIGN

In 2 experiments, a suspension of cells from the posterior hypothalamus of 8- to 10-day old rat pups was injected into the pons (midline, at the level of the locus coeruleus) of adult rats. Control rats received cells from the cerebellum, tissue that is devoid of hypocretin neurons. In the first experiment (n = 33), the adult rats were sacrificed 1, 3, 6, 12, 24, or 36 days after transplant, and cryostat-cut coronal sections of the brainstem were examined for presence of hypocretin-immunoreactive neurons. In the second experiment (n = 9), the transplant medium was modified to include agents that stimulate cell growth, and recipient rats were sacrificed 9, 12, and 36 days after receiving the graft.

SETTINGS

Basic neuroscience research laboratory.

MEASUREMENTS AND RESULTS

In the first experiment, clearly defined hypocretin-immunoreactive containing somata and varicosities were visible in pons of rats sacrificed 1 day after grafting of posterior hypothalamic cells but not in rats receiving cerebellum tissue. The hypocretin-immunoreactive somata were not visible in rats sacrificed at 12, 24, or 36 days, indicating that the neurons had died. However, in the second experiment, where enriched transplant medium was used, clearly defined hypocretin-immunoreactive somata with processes and varicosities were present in the graft zone 36 days after implant. These somata were similar in size and appearance to adult rat hypocretin-immunoreactive neurons.

CONCLUSIONS

These results indicate that hypocretin neurons obtained from rat pups can be grafted into a host brain, and efforts should be made to increase survival of these neurons.

Cryopreserved rat cortical cells develop functional neuronal networks on microelectrode arrays

Neurons growing on microelectrode arrays (MEAs) are promising tools to investigate principal neuronal network mechanisms and network responses to pharmaceutical substances. However, broad application of these tools, e.g. in pharmaceutical substance screening, requires neuronal cells that provide stable activity on MEAs. Cryopreserved cortical neurons (CCx) from embryonic rats were cultured on MEAs and their immunocytochemical and electrophysiological properties were compared with acutely dissociated neurons (Cx). Both cell types formed neuritic networks and expressed the neuron-specific markers microtubule associated protein 2, synaptophysin, neurofilament and gamma-aminobutyric acid (GABA). Spontaneous spike activity (SSA) was recorded after 9 up to 74 days in vitro (DIV) in CCx and from 5 to 30 DIV in Cx, respectively. Cx and CCx exhibited synchronized burst activity with similar spiking characteristics. Tetrodotoxin (TTX) abolished the SSA of both cell types reversibly. In CCx SSA-inhibition occurred with an IC50 of 1.1 nM for TTX, 161 microM for magnesium, 18 microM for D,L-2-amino-5-phosphonovaleric acid (APV) and 1 microM for GABA. CCx cells were easy to handle and developed long living, stable and active neuronal networks on MEAs with similar characteristics as Cx. Thus, these neurochips seem to be suitable for studying neuronal network properties and screening in pharmaceutical research.