Evaluation of intracerebral grafting of dopamine-secreting PC12 cells into allogeneic and xenogeneic brain

Survival of neural progenitors allografted into the CNS of immunocompetent recipients is highly dependent on transplantation site

Allografts continue to be used in clinical neurotransplantation studies; hence, it is crucial to understand the mechanisms that govern allograft tolerance. We investigated the impact of transplantation site within the brain on graft survival. Mouse [Friend leukemia virus, strain B (FVB)] glial precursors, transfected with luciferase, were injected (3 × 10(5)) into the forceps minor (FM) or striatum (STR). Immunodeficient rag2(-/-) and immunocompetent BALB/c mice were used as recipients. Magnetic resonance imaging (MRI) confirmed that cells were precisely deposited at the selected coordinates. The graft viability was assessed noninvasively with bioluminescent imaging (BLI) for a period of 16 days. Regardless of implantation site, all grafts (n = 10) deposited in immunodeficient animals revealed excellent survival. In contrast, immunocompetent animals only accepted grafts at the STR site (n = 10), whereas all the FM grafts were rejected (n = 10). To investigate the factors that led to rejection of FM grafts, with acceptance of STR grafts, another group of animals (n = 19) was sacrificed during the prerejection period, on day 5. Near-infrared fluorescence imaging with IRDye 800CW-polyethylene glycol probe displayed similar blood-brain barrier disruption at both graft locations. The morphological distribution of FM grafts was cylindrical, parallel to the needle track, whereas cells transplanted into the STR accumulated along the border between the STR and the corpus callosum. There was significantly less infiltration by both innate and adaptive immune cells in the STR grafts, especially along the calloso-striatal border. With allograft survival being dependent on the transplantation site, the anatomical coordinates of the graft target should always be taken into account as it may determine the success or failure of therapy.

Intrathecal implantation of microencapsulated PC12 cells reduces cold allodynia in a rat model of neuropathic pain

The transplantation of cells into the central nervous system provides a constant and replenishable source of analgesic substances for the alleviation of chronic pain. In the present study, PC12 cells were microencapsulated in a semipermeable membrane that protected the cells from the host's immune system. A chronic neuropathic pain model was induced by chronic constriction injury (CCI) of the sciatic nerve in rats. Thirty Sprague-Dawley rats with CCI were divided randomly into two groups: the cell-loaded group received microencapsulated PC12 cells (n = 15) and the control group received empty capsules (n = 15). The microcapsules were implanted into the lumbar subarachnoid space. After implantation, a significant reduction of cold allodynia was observed in the rats of the cell-loaded group at 7, 14, 21, and 28 days compared to the control group with the empty capsules (P < 0.05). Furthermore, the levels of catecholamines and met-enkephalin in the cerebrospinal fluid of rats in the cell-loaded group were higher than the levels in the controls (P < 0.05). These results suggest that intrathecal microencapsulated PC12 cells could be a useful method for chronic neuropathic pain management.

Pharmacologically active microcarriers: a tool for cell therapy

To overcome certain problems encountered in cell therapy, particularly cell survival, lack of cell differentiation and integration in the host tissue, we developed pharmacologically active microcarriers (PAM). These biodegradable particles made with poly(D,L-lactic-co-glycolic acid) (PLGA) and coated with adhesion molecules may serve as a support for cell culture and may be used as cell carriers presenting a controlled delivery of active protein. They can thus support the survival and differentiation of the transported cells as well as their microenvironment. To develop this tool, nerve growth factor (NGF)-releasing PAM, conveying PC12 cells, were produced and characterized. Indeed, these cells have the ability to differentiate into sympathetic-like neurons after adhering to a substrate, in the presence of NGF, and can then release large amounts of dopamine. Certain parameters such as the size of the microcarriers, the conditions enabling the coating of the microparticles and the subsequent adhesion of cells were thus studied to produce optimized PAM.

Reduction of infarct volume and apoptosis by grafting of encapsulated basic fibroblast growth factor—secreting cells in a model of middle cerebral artery occlusion in rats

Object. This study was conducted to evaluate the effects of grafting encapsulated basic fibroblast growth factor (bFGF)—secreting cells in rat brains subjected to ischemic injury.

Methods. Two cell lines were used for encapsulated grafting in this experiment, namely, a bFGF-secreting cell line established by genetic manipulation of baby hamster kidney (BHK) cells, and a naive BHK cell line. Forty-seven Sprague—Dawley rats were used in this experiment. The animals were divided into the following three groups: those receiving grafts of encapsulated bFGF-secreting cells (BHK-bFGF group); those with grafts of encapsulated naive BHK cells (naive BHK group); and those with no grafts (control group). The authors implanted encapsulated cells into the right striatum of host rats in the BHK-bFGF and naive BHK groups. Six days after grafting, the host and control animals underwent permanent right middle cerebral artery occlusion (MCAO) with an intraluminal suture procedure. The infarct volume was evaluated using 2,3,5-triphenyltetrazolium chloride staining and computerized image analysis 24 hours after MCAO. Fragmentations of DNA in the host brains were analyzed using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling 12 hours after MCAO.

The authors found that the infarct volume in the BHK-bFGF group was reduced by approximately 30% compared with that in the naive BHK and control groups. In the ischemic penumbral area, the number of apoptotic cells in the BHK-bFGF group was significantly decreased compared with that in the other groups.

Conclusions. The grafting of encapsulated BHK bFGF-secreting cells protected the brain from ischemic injury. Encapsulation and grafting of genetically engineered cells such as bFGF-secreting cells is thus thought to be a useful method for protection against cerebral ischemia.

Stereotactic transplantation of a dopamine-producing capsule into the striatum for treatment of Parkinson disease: a preclinical primate study

OBJECT

The PC12 cells are well known for their ability to secrete dopamine and levodopa. In multiple animal mode encapsulated PC12 cells have been shown to ameliorate parkinsonian symptoms when transplanted into the striatum; technique is expected to be effective clinically as well. The present study was performed using nonhuman primates to ensure that the transplantation of encapsulated PC12 cells is likely to be both safe and effective in human clinical trials.

METHODS

Unencapsulated or encapsulated PC12 cells were implanted into the brains of Japanese monkeys (Macaca fuscata). Histological and immunocytochemical analyses were performed 1, 2, 4, and 8 weeks posttransplantation on the unencapsulated cells and 2, 4, and 8 weeks after transplantation on the encapsulated cells. The survival of the PC12 cells inside the capsule was determined by measuring the amounts of dopamine and levodopa released from the capsules a removal from the striatum. Magnetic resonance imaging was performed in both unencapsulated and encapsulated PC12 cell-grafted groups. Due to the immunological reaction of the host brain no unencapsulated PC12 cells remained in the grafted area 8 weeks after transplantation. On the contrary, encapsulated PC12 cells retrieved from the host brain continued to release dopamine and levodopa even 8 weeks after implantation. The host's reaction to the PC12-loaded capsule was much weaker than that to the unencapsulated PC12 cells.

CONCLUSIONS

These results suggest that the transplantation of encapsulated PC12 cells could be a safe and effective treatment modality for Parkinson disease in human patients.

Aggregation enhances catecholamine secretion in cultured cells

Transplanted cells and tissues have potential uses in the treatment of genetic, geriatric, and metabolic disorders, but optimal conditions for transplantation are not yet known. In this report, PC12 cells were aggregated in rotary and microgravity culture, using serum-free or serum-supplemented medium, and using a multifunctional polymer-peptide aggregation factor. Aggregates and single cells were then encapsulated and cultured within agarose gels, and the dopamine secretion in response to a depolarization buffer was measured using high-performance liquid chromatography combined with electrochemical detection (HPLC-ECD). On a per-cell basis, aggregated cells secreted higher levels of dopamine than did single cells. The size of the aggregates was also a factor in catecholamine secretion; dopamine release from the larger aggregates formed in rotary culture was observed to increase at a faster rate, then achieve a plateau level at an earlier time than did the smaller aggregates. Cells aggregated in microgravity culture exhibited a markedly different behavior, lacking the rapid rise in dopamine secretion characteristic of the rotary-aggregates cells: on a per-cell basis, the dopamine secretion remained at a level corresponding to the plateau level expressed by the rotary-aggregates cells. Dopamine secretion in aggregates may be enhanced by the increase in number of cell-cell contacts, as occurs during high-density culture of PC12 cells. These results provide further evidence that cell-cell contact regulates the behavior of differentiated cells, and therefore is important in tissue engineering.

Discordant xenografts: different outcome after mouse and rat neural tissue transplantation to guinea-pigs

Embryonic neural tissue obtained from other species has been considered as a donor tissue source in repair strategies for human neurodegenerative disorders. The neuro- and immunobiology of distantly related species combinations, discordant xenografts, need to be characterised. For this purpose, a small animal model would be an important research tool. Adult guinea-pigs, and adult rats as controls, received intrastriatal grafts of either mouse or rat embryonic ventral mesencephalic tissue. The survival rates and types of host immune response were assessed at 2 weeks after grafting using stereological techniques and semi-quantitative evaluations. In the mouse-to-guinea-pig group, all transplants were rejected and no tyrosine hydroxylase-immuno reactive (TH-IR) cells remained. In the rat-to-guinea-pig group, there was good survival of TH-IR cells (5050 SEM+/-1550), similar to that in the rat-to-rat group (4900 SEM+/-1540). In the mouse-to-rat group, half of the animals had no surviving TH-IR cells (520 SEM+/-230 for the whole group). These species combinations offer inexpensive, efficient, and suitable conditions to study important survival factors for discordant xenogeneic neural tissue transplants. The factors responsible for the divergent graft outcomes between the two combinations might provide clues on how to manipulate xenogeneic tissue to increase survival rates in the future.