Functional regeneration in a rat Parkinson's model after intrastriatal grafts of glial cell line-derived neurotrophic factor and transforming growth factor beta1-expressing extra-adrenal chromaffin cells of the Zuckerkandl's organ

Intrabrain transplantation of chromaffin cell aggregates of the Zuckerkandl's organ, an extra-adrenal paraganglion that has never been tested for antiparkinsonian treatment, induced gradual improvement of functional deficits in parkinsonian rats. These beneficial effects were related to long survival of grafted cells, striatal reinnervation, and enhancement of dopamine levels in grafted striatum. Grafted cells were not dopaminergics, but they expressed glial cell line-derived neurotrophic factor (GDNF) and transforming growth factor-beta(1). These factors were detected in the host striatal tissue, indicating that chromaffin cells secreted them after grafting. Because glial cell line-derived neurotrophic factor possesses neurorestorative properties over dopaminergic neurons, and transforming growth factor-beta(1) is a cofactor that potentiates the neurotrophic actions of GDNF, functional regeneration was likely caused by the chronic trophic action of neurotrophic factors delivered by long-surviving grafted cells. This work should stimulate research on the clinical applicability of transplants of the Zuckerkandl's organ in Parkinson's disease.

Microencapsulated bovine chromaffin cell xenografts into hemiparkinsonian rats: a drug-induced rotational behavior and histological changes analysis

Bovine chromaffin cells were microencapsulated within alginate-polylysine-alginate (APA) membranes. Microencapsulated bovine chromaffin cells as well as unencapsulated cells and empty microcapsules were grafted into the brain of hemiparkinsonian rats with 6-hydroxydopamine (6-OHDA) lesions. Apomorphine-induced rotational behavior of the host animals and the survival of the grafted chromaffin cells were examined after transplantation. The animals receiving microencapsulated bovine chromaffin cells showed a significant decrease (17.6--35.6%) in apomorphine-induced rotation 1 week postimplantation that remained stable for the 10 month test period. Fluorescent histochemistry further revealed that microencapsulation increased the chromaffin cell survival with only a minimum host reaction for up to 10 months posttransplantation while the survival of free, unencapsulated chromaffin cells was only modest and was accompanied by a large inflammatory response. The reduction of apomorphine-induced rotations was correlated with the survival of bovine chromaffin cells in the host brain. The data indicate that encapsulation of bovine chromaffin cells in APA membranes reduces the host immune response to the xenograft and prolongs the viability of the grafted cells.

[Management of intractable cancer pain: from intrathecal morphine to cell allograft]

The durable effectiveness of intrathecal morphine administration is well established for the management of intractable cancer pain, after failure of systemic opioids, secondary to the persistence of non-reversible undesirable side effects. Many patients are referred to late in the disease course. This conservative method to control pain of malignant origin must not be reserved for last resort treatment for terminal patients. Intra-cerebro-ventricular morphine administration is a very effective and generally safe method for controlling intractable cancer pain. Because of the chronic implantation of an intra-ventricular catheter this method is somewhat invasive. Its indications remain a simple and effective alternative when the topography of nociceptive pain is diffuse or cephalic. In clinical practice, intrathecal and/or intra-cerebro-ventricular administration of opioids is limited by cost, the need for specialized maintenance and mechanical malfunctions if implantable drug delivery systems, or by the risk of bacterial contamination and ambulatory constraints when repeated daily injections via an intrathecal access port are used. To answer these limitations, cell therapy using intrathecal chromaffin cell allograft is a promising approach for the management of cancer pain refractory to traditional drug therapy and pain lesion surgery. The basic rationale and preclinical studies on experimental pain models have enabled starting prospective clinical trials. Prior to transplantation, handling and preparation of the chromaffin tissue is critical for allograft viability. The initial results of clinical trials with human chromaffin cell grafts from intractable cancer pain have reported long-lasting pain relief, in correlation with met-enkephalin release into the CSF. Convincing evidence will require controlled studies. The limitations of this innovative cell therapy and especially the lack of human adrenal gland availability point to the need for new sources of cells. Perspectives include xenogenic or engineered cell lines.

Intrathecal polymer-encapsulated bovine adrenal chromaffin cells fail to produce analgesic effects in the hotplate and formalin test

Numerous publications have reported that adrenal chromaffin cells implanted in the lumbar intrathecal space produce analgesic effects in rodent models of pain. The present study was intended to replicate and extend on the results of those previous publications. This study was conducted to determine: (1) if analgesic effects of polymer-encapsulated intrathecal adrenal chromaffin cells could be detected in the more sensitive low temperature hot-plate test without using nicotine to stimulate chromaffin cell output, (2) if a dose-response curve can be produced in the hot-plate and formalin tests with different numbers of adrenal chromaffin cells (0K, 120K, or 330K), (3) if cell viability and/or the magnitude of analgesic effects are affected by differences in implant site (i.e. thoracic versus lumbar implant site), and (4) the magnitude of the analgesic effects of adrenal chromaffin cells relative to doses of systemic morphine. No analgesic effects related to chromaffin cells were detected in the present study in the formalin test or in the hot-plate test, even with nicotine stimulation, regardless of the number of cells implanted or the intrathecal implant site. The reliability and sensitivity of the behavioral measures to the effects of mild analgesics are supported by the fact that consistent differences in performance between individual rats could be detected, the effects of fairly modest doses of nicotine and morphine were detectable, and consistent dose-response curves were evident with respect to both nicotine and morphine. Device performance appeared to be within the range of previous studies that reported analgesic effects of encapsulated adrenal chromaffin cells. It is unclear why analgesic effects of adrenal chromaffin cells were not detected in the present study.

Initial characterization of the transplant of immortalized chromaffin cells for the attenuation of chronic neuropathic pain

Cultures of embryonic day 17 (E17) rat adrenal and neonatal bovine adrenal cells were conditionally immortalized with the temperature-sensitive allele of SV40 large T antigen (tsTag) and chromaffin cell lines established. Indicative of the adrenal chromaffin phenotype, these cells expressed immunoreactivity (ir) for tyrosine hydroxylase (TH), the first enzyme in the synthetic pathway for catecholamines. At permissive temperature in vitro (33 degrees C), these chromaffin cells are proliferative, have a typical rounded chromaffin-like morphology, and contain detectable TH-ir. At nonpermissive temperature in vitro (39 degrees C), these cells stop proliferating and express increased TH-ir. When these immortalized chromaffin cells were transplanted in the lumbar subarachnoid space of the spinal cord I week after a unilateral chronic constriction injury (CCI) of the rat sciatic nerve, they survived longer than 7 weeks on the pia mater around the spinal cord and continued to express TH-ir. Conversely, grafted chromaffin cells lost Tag-ir after transplant and Tag-ir was undetectible in the grafts after 7 weeks in the subarachnoid space. At no time did the grafts form tumors after transplant into the host animals. These grafted chromaffin cells also expressed immunoreactivities for the other catecholamine-synthesizing enzymes 7 weeks after grafting, including: dopamine-beta-hydroxylase (DbetaH) and phenylethanolamine-N-methyltransferase (PNMT). The grafted cells also expressed detectable immunoreactivities for the opioid met-enkephalin (ENK), the peptide galanin (GAL), and the neurotransmitters y-aminobutyric acid (GABA) and serotonin (5-HT). Furthermore, after transplantation, tactile and cold allodynia and tactile and thermal hyperalgesia induced by CCI were significantly reduced during a 2-8-week period, related to the chromaffin cell transplants. The maximal antinociceptive effect occurred 1-3 weeks after grafting. Control adrenal fibroblasts, similarly immortalized and similarly transplanted after CCI, did not express any of the chromaffin antigenic markers, and fibroblast grafts had no effect on the allodynia and hyperalgesia induced by CCI. These data suggest that embryonic and neonatal chromaffin cells can be conditionally immortalized and will continue to express the phenotype of primary chromaffin cells in vitro and in vivo; grafted cells will ameliorate neuropathic pain after nerve injury and can be used as a homogeneous source to examine the mechanisms by which chromaffin transplants reverse chronic pain. The use of such chromaffin cell lines that are able to deliver antinociceptive molecules in models of chronic pain after nerve and spinal cord injury (SCI) offers a novel approach to pain management.

Transplants of adrenal medullary chromaffin cells reduce forelimb and hindlimb allodynia in a rodent model of chronic central pain after spinal cord hemisection injury

In the majority of patients, spinal cord injury (SCI) results in abnormal pain syndromes in which non-noxious stimuli become noxious (allodynia). To reduce allodynia, it would be desirable to implant a permanent biological pump such as adrenal medullary chromaffin cells (AM), which secrete catecholamines and opioid peptides, both antinociceptive substances, near the spinal cord. We tested this approach using a recently developed a mammalian SCI model of chronic central pain, which results in development of mechanical and thermal allodynia. Thirty day-old male Sprague-Dawley rats were spinally hemisected at T13 and allowed 4 weeks for recovery of locomotor function and development of allodynia. Nonimmunosuppressed injured animals received either control-striated muscle (n = 7) or AM (n = 10) transplants. Nociceptive behavior was tested for 4 weeks posttransplant as measured by paw withdrawals to von Frey filaments, radiant heat, and pin prick stimuli. Hemisected animals receiving AM demonstrated statistically significant reductions in both fore- and hindlimb mechanical and thermal allodynia, but not analgesia, when compared to hemisected animals receiving striated muscle transplants (P < 0.05). Tyrosine hydroxylase immunoreactivity indicated prolonged transplant survival and production of catecholamines. HPLC analysis of cerebrospinal fluid samples from animals receiving AM transplants demonstrated statistically significant increases in levels of dopamine (sevenfold), norepinephrine (twofold), and epinephrine (threefold), compared to control values several weeks following transplant (P < 0.05). By 28 days posttransplant, however, antinociceptive effects were diminished. These results support the therapeutic potential of transplanted AM in reducing chronic central pain following spinal cord injury.

Mutual induction of TGFbeta1 and NGF after treatment with NGF or TGFbeta1 in grafted chromaffin cells of the adrenal medulla

Chromaffin cells have been recognized for their ability to transform into sympathetic ganglion-like cells in response to nerve growth factor (NGF) or to stimulation of other neurotrophic factors. Transforming growth factor beta (TGFbeta) family members have been shown to potentiate the effect of different trophic factors. The aim of this study was to investigate if TGFbeta may influence NGF-induced neuronal transformation and regulation of NGF, TGFbeta1, and their receptors in the adult rat chromaffin tissue after grafting. Intraocular transplantation of adult chromaffin tissue was employed and grafts were treated with TGFbeta1 and/or NGF. Graft survival time was 18 days after which the grafts were processed for TGFbeta luciferase detection assay, NGF enzyme immunoassay, or in situ hybridization. In grafts stimulated with NGF, increased levels of TGFbeta1 and TGFbeta1 mRNA were detected. When grafts instead were treated with TGFbeta1, enhanced levels of NGF protein were found. Furthermore, a positive mRNA signal corresponding to the transforming growth factor II receptor (TbetaRII) was found in the chromaffin cells of the normal adrenal medulla as well as after grafting. No increase of TbetaRII mRNA levels was detected after transplantation or after TGFbeta1 treatment. Instead a reduction of TbetaRII mRNA expression was noted after NGF treatment. NGF stimulation of grafts increased the message for NGF receptors p75 and trkA in the chromaffin transplants. Grafts processed for evaluations of neurite outgrowth were allowed to survive for 28 days and were injected weekly with NGF and/or TGFbeta1. NGF treatment resulted in a robust innervation of the host irides. TGFbeta1 had no additive effect on nerve fiber formation when combined with NGF. Combined treatment of NGF and anti-TGFbeta1 resulted in a significantly larger area of reinnervation. In conclusion, it was found that NGF and TGFbeta1 may regulate the expression of each other's protein in adult chromaffin grafts. Furthermore, TbetaRII mRNA was present in the adult rat chromaffin cells and became downregulated as a result of NGF stimulation. Although no synergistic effects of TGFbeta1 were found on NGF-induced neurite outgrowth, it was found that TGFbeta1 and NGF signaling are closely linked in the chromaffin cells of the adrenal medulla.

Human chromaffin cell graft into the CSF for cancer pain management: a prospective phase II clinical study

A number of pre-clinical studies have demonstrated the value of adrenal medullary allografts in the management of chronic pain. The present longitudinal survey studied 15 patients transplanted for intractable cancer pain after failure of systemic opioids due to the persistence of undesirable side-effects. Before inclusion, all the patients had their pain controlled by daily intrathecal (I-Th) morphine administration. The main evaluation criteria of analgesic activity of the chromaffin cell allograft was the complementary requirement of analgesics and in particular the consumption of I-Th morphine required to maintain effective pain control. Out of the 12 patients who profited from enhanced analgesia with long-term follow-up (average 4.5 months), five no longer required the I-Th morphine (with prolonged interruption of systemic opioids as well), two durably decreased I-Th morphine intake and five were stabilized until the end of their follow-up. Durable decline and stabilization were interpreted as indicative of analgesic activity by comparison with the usual dose escalation observed during disease progression. In most cases, we noted a relationship between analgesic responses and CSF met-enkephalin levels. The results of this phase II open study demonstrate the feasibility and the safety of this approach using chromaffin cell grafts for long-term relief of intractable cancer pain. However, while analgesic efficacy was indicated by the reduction or stabilization in complementary opioid intake, these observations will need to be confirmed in a controlled trial in a larger series of patients.

Xenotransplantation of microencapsulated bovine chromaffin cells into hemiparkinsonian monkeys

This study examines the effects of xenografts of microencapsulated bovine chromaffin cells (BCCs) on the rotational behavior of hemiparkinsonian monkey recipients. In addition, it determines the content of monoamine neurotransmitters and their major metabolites in the neostriatum in hemiparkinsonian monkeys. The hemiparkinsonian model in monkeys was induced by a unilateral intracarotid injection of methyl-phenyl-tetrahydropyridine (MPTP). Unencapsulated BCCs, BCCs microencapsulated in alginate-polylysine-alginate (ALA) membranes as well as empty microencapsules were grafted into the neostriatum of the hemiparkinsonian monkeys. Following the transplantation the hemiparkinsonian symptoms subsided and the number of rotations induced by apomorphine decreased for up to nine months in the group of recipients grafted with microencapsulated BCCs, while only a temporary improvement (one month) was detected in the recipients of the unencapsulated BCCs. No change was observed in the recipients of empty microencapsules. Dopamine and its metabolites were found considerably depleted in the MPTP-lesioned side versus the unlesioned side of the neostriatum in the hemiparkinsonian monkeys(P<0.05).

Spinal CSF from rats with painful peripheral neuropathy evokes catecholamine release from chromaffin cells in vitro

The environment presented by host tissue may influence cellular transplants in the CNS depending on injury or disease. Here we examined whether chronic pain alters cerebrospinal fluid (CSF), thereby enhancing the analgesic effect of transplanted adrenal cells. CSF samples were taken intracisternally from rats with neuropathic pain induced by chronic constriction injury of the sciatic nerve. The samples were applied to cultured bovine chromaffin-cell clusters while catecholamine release was measured by fast cyclic voltammetry. This caused marked and sustained elevations in catecholamine levels, compared to CSF from sham-operated controls, which were reversible by the nicotinic antagonist mecamylamine. These results suggest that chronic neuropathic pain produces increased CSF levels of secretogogues for chromaffin cells, and illustrates the importance of host microenvironmental factors in determining graft function.

Emerging cell and molecular strategies for the study and treatment of painful peripheral neuropathies

Pharmacologic treatment for the symptoms of painful neuropathy has been problematic, because there has been limited understanding of the underlying etiologies and systemic levels that an effective dose can have on multiple side effects. The use of molecular methods, such as gene deletion from knockout mice and cellular minipumps for delivery of biologic antinociceptive molecules, has led to a better understanding of the underlying mechanisms of the induction of intractable neuropathic pain. The initiation of an excitatory cascade after injury or disease leads to the induction of various second messenger systems, loss or down-regulation of the endogenous inhibitory spinal GABA system and central sensitization, causing such pain. The development and use of cellular minipumps, immortalized cell lines bioengineered to secrete various antinociceptive molecules for the reversal of neuropathic pain, makes cellular therapy a strategy for clinical use in the next few years. The development of molecular "disimmortalization" technologies will make the use of such engineered cell lines safe for human use. Direct somatic gene transfer for neuropathic pain will eventually overcome the problems associated with transplantation of non-autologous and xenogenic cells. These virus-mediated methods, although at the early stages of evolution and use, offer large-scale production of biologic agents that can be conveniently and confidently used for the long-term relief of chronic neuropathic pain in a clinical setting, without systemic effects or surgical interventions.

[Clinical perspectives of xenografts: encapsulated chromaffin cells and pain]

Intrathecal allograft of chromaffin cells can be effectively used in replacement of more conventional therapies for treating intractable chronic pain, such as in cancer. The efficacy of this technique depends on the ability of those cells to produce analgesic opioids and on the immuno-privileged property of the central nervous system, in which rejection risks are limited. However, there are some limitations to the generalization of this new therapy, mainly due to the low number of available grafts. Thus other sources than humans have to be considered. Here we discuss the pros and cons of the xenogeneic chromaffin cells of bovine or porcine origin. Graft immuno-isolation, for example, by using cell encapsulation, seems to be unavoidable in spite of the graft site.

Expression and regulation of CNTF receptor-alpha in the in situ and in oculo grafted adult rat adrenal medulla

Cultured and transplanted adrenal medullary cells respond to ciliary neurotrophic factor (CNTF) with neurite formation and improved cell survival although the presence of the CNTF receptor-alpha (CNTFRalpha) has been unclear. This study show that CNTFRalpha mRNA was expressed in the postnatal day 1 as well as in the adult rat adrenal medulla. The highest CNTFRalpha mRNA signal was found in the ganglion cells of the adrenal medulla. After transplantation of adrenal medullary tissue the CNTFRalpha mRNA levels were down-regulated in the chromaffin cells. CNTF treatment of grafts did not normalize the receptor levels, but treatment with nerve growth factor (NGF) did. Thus, we demonstrate that CNTFRalpha mRNA is expressed in adrenal medulla, the levels becomes down-regulated after transplantation, but normalized after treatment with NGF.

Intrathecal grafting of unencapsulated adrenal medullary tissue can bring CD4 T lymphocytes into CSF: a potentially deleterious event for the graft

Adrenal medullary tissue including chromaffin cells was grafted intrathecally in cancer patients to relieve intractable pain. The central nervous system (CNS) is considered an immune privileged site. Therefore, non-HLA-matched and unencapsulated tissue was grafted in 15 patients and 1 sham control in a series of at least 20 grafts. We observed an increase in CSF lymphocyte counts in 15/20 allografts (75%). In contrast to peripheral blood, CD4 T cells predominated in the CSF, but failed to exhibit an activated phenotype (CD25+ CD45RO+ HLA-DR+). The positive effect of graft on pain, the high met-enkephalin levels, the absence of any increase in CSF cytokine levels particularly for IFN-gamma or IL-2 (but not IL-10 and IL-6), indirectly indicated that the graft was tolerated despite the presence of CSF lymphocytes. The single treatment failure and three of four cases of partial efficacy occurred in grafts where CSF lymphocytes were present. Moreover, when assayed (n = 7), the CD4+ CSF lymphocytes still retained the capacity to exhibit ex vivo a normal or enhanced frequency of T CD4 cells producing IFN-gamma and IL-2. Taken together, our observations indicate that impairment of the local immunosuppressive balance can lead to activation of those CSF CD4 T cells and drive a rejection process. This study suggests further work on the purification and/or the immunoisolation of tissues grafted in the CNS will be necessary, particularly when the possibility of long-term and repeated grafting is considered.

Fine structure of host-graft relationships between transplanted chromaffin cells and CNS

Our laboratory studies have shown that transplantation of adrenal medullary tissue or isolated chromaffin cells into central nervous system (CNS) pain modulatory regions (i.e., periaqueductal gray and subarachnoid lumbar spinal cord) can reduce pain sensitivity of rats in both acute and chronic pain. The analgesia produced by these transplants is thought to result from release of both opiate peptides and catecholamines. Morphologically, these animal studies also suggest that there is no development of tolerance over long periods of time, and the transplanted chromaffin cells appear to be robust and well integrated with the host tissue. In our initial clinical studies, where allografts of adrenal medullary tissue were transplanted intrathecally to relieve intractable cancer pain, patients obtained significant and long-lasting pain relief. Increased cerebrospinal fluid (CSF) levels of metenkephalin were correlated with the decreased pain scores. Histology of autopsy tissue obtained from two patients with 1 year transplants revealed viable transplanted chromaffin cells. Because of the limited availability of human adrenal glands, sources of xenogeneic chromaffin cells will need to be identified if effective transplantation therapy for chronic pain is to be developed further.

Purification of adrenal chromaffin cells increases antinociceptive efficacy of xenotransplants without immunosuppression

We have found that immunosuppression is necessary for the survival of xenogeneic adrenal medullary transplants. Because chromaffin cells are essentially nonimmunogenic, it is likely that the highly immunogenic "passenger" cells in the transplant preparation bring about rejection. This article describes a procedure that produces an essentially pure preparation of chromaffin cells for transplantation. Bovine adrenal medullary cells were isolated and differentially plated, resulting in a semipurified preparation of chromaffin cells. Ferromagnetic beads were added to the cell suspension, some of which were phagocytized by endothelial cells, which allowed their removal by exposure to a magnet. The remaining cells were then exposed to ferromagnetic beads coated with isolectin B4 from Griffonia simplicifolia and once again to a magnetic field. The "semipurified" preparation contained approximately 90% chromaffin cells, whereas the "highly purified" preparation was > 99.5% chromaffin cells as determined immunohistochemically. The immunogenicity of the two cell preparations was assessed in vitro by determining their capacity to evoke lymphocyte proliferation. Rat spleen lymphocytes were mixed with either a highly purified or semipurified population of bovine chromaffin cells. The results of this assay demonstrated that the highly purified preparation was a much weaker stimulant of lymphocyte proliferation than was the semipurified preparation and may demonstrate better graft survival in vivo. Transplantation via intrathecal catheter of either 80,000 or 250,000 cells from the highly or partially purified preparations onto the lumbar spinal cord of nonimmunosuppressed and non-nicotine-stimulated rats produced a cell number-dependent antinociception for both A(delta) and C fiber-mediated thermonociception at 6 days after transplantation. After 6 days and up to 28 days, only the "highly purified" preparation showed antinociception. These results suggest that nearly complete purification of bovine chromaffin cells minimizes immunorejection of xenogeneic transplants of these cells.

Transplant of cultured neuron-like differentiated chromaffin cells in a Parkinson's disease patient. A preliminary report

BACKGROUND

Treatment of Parkinson's Disease (PD) has been attempted by others by transplanting either the patient's own adrenal medullary tissue or fetal substantia nigra into caudate or putamen areas. However, the difficulties inherent in using the patient's own adrenal gland, or the difficulty in obtaining human fetal tissue, has generated the need to find alternative methods.

METHODS

We report here of an alternative to both procedures by using as transplant material cultured human adrenal chromaffin cells differentiated into neuron-like cells by extremely low frequency magnetic fields (ELF MF).

RESULTS

The results of this study show that human differentiated chromaffin cells can be grafted into the caudate nucleus of a PD patient, generating substantial clinical improvement, as measured by the Unified Rating Scale for PD, which correlated with glucose metabolism and D2 DA receptor increases as seen in a PET scan, while allowing a 70% decrease in L-Dopa medication.

DISCUSSION

This is the first preliminary report showing that transplants of cultured differentiated neuron-like cells can be successfully used to treat a PD patient.

Intrastriatal transplantation of rat adrenal chromaffin cells seeded on microcarrier beads promote long-term functional recovery in hemiparkinsonian rats

Possible biologic treatments for Parkinson's disease, a disorder caused by the deterioration of dopaminergic neurons bridging the nigrostriatal system, have recently focused on fetal cell transplantation. Because of ethical and tissue availability issues concerning fetal cell transplantation, alternative cell sources are being developed. The adrenal medulla has been used as a cell transplant source because of the capacity of the cells to provide catecholamines and to transform into a neuronal phenotype. However, adrenal tissue transplants have shown limited success, primarily because of their lack of long-term viability. Recently, seeding adrenal chromaffin cells on microcarrier beads has been shown to enhance the cell viability following neural transplantation. In the present study, we further investigated whether transplantation of rat adrenal chromaffin cells seeded on microcarrier beads into the striatum of 6-hydroxydopamine-induced hemiparkinsonian rats would result in a sustained functional recovery. Behavioral tests using the apomorphine-induced rotational and elevated body swing tests up to 12 months posttransplantation revealed a significant behavioral recovery in animals that received adrenal chromaffin cells seeded on microcarrier beads compared to animals that received adrenal chromaffin cells alone, medium alone, or beads alone. Histological examination of tissue at 14 months posttransplantation revealed evidence of tyrosine hydroxylase-positive cells and an on-going glial response in animals transplanted with adrenal chromaffin cells seeded on microcarrier beads, in contrast to absence of such immunoreactive responses in the other groups. These findings support a facilitator role for microcarrier beads in transplantation of adrenal chromaffin cells or other cells that are easily rejected by the CNS.

Long-term alleviation of allodynia-like behaviors by intrathecal implantation of bovine chromaffin cells in rats with spinal cord injury

Adrenal chromaffin cells produce analgesic substances, such as catecholamines and enkephalins, and intrathecal (i.t.) implantation of either allografted adrenal tissue or xenogenic chromaffin cells produce antinociception in animals. We evaluated the analgesic effect of bovine chromaffin cells in a model of central pain in which rats exhibit chronic allodynia-like behavior after photochemically induced ischemic spinal cord injury. Bovine chromaffin cells or endothelial cells were injected i.t. onto the lumbar spinal cord and their effects on mechanical and cold allodynia-like behaviors were studied for up to 8 weeks. The chronic allodynia-like behavior was stable for months without signs of remission and i.t. implantation of human endothelial cells did not alleviate the chronic allodynia-like behavior for the entire observation period. In contrast, 2 weeks after i.t. implantation of bovine chromaffin cells, the mechanical allodynia was abolished in the spinally injured rats, and the enhanced response to cold stimuli was significantly reduced. The overall effects were significant up to 8 weeks after i.t. implantation, although the anti-allodynic effect decreased towards the end of the observation period. No signs of side-effects were noted after i.t. implantation. The allodynia-like state was temporarily restored by naloxone (0.5 mg/kg) or phentolamine (0.3 mg/kg) injected intraperitoneally. Immunohistochemical examination revealed that tyrosine hydroxylase (TH)-positive chromaffin cells could be identified adjacent to the spinal cord up to 4 weeks after i.t. implantation, whereas at 8 weeks the TH-positive cells were sparse. It is concluded that bovine chromaffin cells stay viable in rat spinal cord for a considerable period of time after i.t. administration and alleviate chronic allodynia-like behavior in spinally injured rats, possibly through activation of opioid and alpha-adrenoceptors. The present results further document a new therapeutic approach for the treatment of chronic neuropathic pain.

The influence of xenotransplant immunogenicity and immunosuppression on host MHC expression in the rat CNS

During the early stages following neural transplantation, host immune responses are initiated that are not normally found in the CNS including the induction of major histocompatibility antigens (MHC I and II). Previous laboratory findings have demonstrated prolonged survival of bovine chromaffin cells (BCC) in the rat CNS following transient immunosuppression with cyclosporin A (CSA) providing chromaffin cells are isolated from highly immunogenic passenger cells. To assess the influence of passenger and chromaffin cells on host MHC I and II expression, either BCC, nonchromaffin cell adrenal constituents (NCC), or adrenal medullary endothelial cells (EC) were implanted into the host. At 2 weeks postimplantation, robust BCC survival was obtained in CSA-treated animals. This correlated with low expression of MHC I at the host-graft border and the virtual absence of MHC II. Good BCC survival with reduced MHC I expression only was seen at 6 weeks postimplantation in animals transiently immunosuppressed (4 weeks). In contrast, poor survival was seen in the EC group (even with CSA treatment). In addition, marked MHC I and II expression was found in and around these grafts at 2 weeks, and was particularly intense in EC implanted animals. The results of this study suggest that nonchromaffin passenger cells in BCC preparations, most notably endothelial cells, can induce strong immune responses even in the presence of immunosuppression. Based on MHC staining, removal of these passenger cells can reduce host responses and improve long term survival of xenogeneic chromaffin cells in the CNS.

Long-term enhanced chromaffin cell survival and behavioral recovery in hemiparkinsonian rats with co-grafted polymer-encapsulated human NGF-secreting cells

The transplantation of genetically modified cells represents one potential means of delivering trophic factors to the brain to support the survival of host neurons and to increase the survival of co-grafted cells. The present study examined the ability of encapsulated baby hamster kidney (BHK) fibroblasts, which were genetically modified to produce human nerve growth factor (hNGF), to provide long-term trophic support to co-grafted adrenal chromaffin cells. Following polymer encapsulation, BHK-hNGF cells were grafted into the striatum of hemiparkinsonian rats together with unencapsulated adrenal medullary chromaffin cells. Secretion of hNGF from the encapsulated cells, morphology of these cells, apomorphine-induced rotational behavior of the host animals, and survival of the co-grafted chromaffin cells were examined 1, 6, and 12 months after transplantation. Analysis of retrieved capsules revealed that the BHK cells survived and continued to release hNGF at a level of 2-3 ng/day even 12 months after transplantation. Although the animals receiving adrenal medulla alone did not show recovery of apomorphine-induced rotational behavior, the animals receiving adrenal medulla intrastriatal hNGF-secreting cells showed a significant decrease (40-50%) in apomorphine-induced rotation within 1 month postimplantation that remained stable for the 12-month test period. Tyrosine hydroxylase immunocytochemistry further revealed that while survival of chromaffin cells without hNGF support was poor, co-grafting of adrenal medulla and BHK-hNGF cells dramatically 926- to 32-fold) increased chromaffin cell survival 1, 6, and 12 months after transplantation. These results demonstrate that (1) encapsulated BHK cells survive for extended periods of time in vivo while continuing to secrete hNGF, (2) the continued secretion of hNGF provides trophic support for co-grafted adrenal chromaffin cells, and (3) the increased chromaffin cell survival is associated with long-term, stable behavioral recovery. These data further support the potential use of this approach for treating Parkinson's disease.