Transplantation of human chromaffin cells for control of intractable cancer pain

Bovine Chromaffin Cells for CNS Transplantation do not Elicit Xenogeneic T Cell Proliferative Responses in Vitro

Adrenal chromaffin cells have been utilized for several neural grafting applications, but limitations in allogeneic donor availability and dangers inherent in auto-grafting limit the widespread use of this approach clinically. While xenogeneic donors offer promise as a source for cell transplantation in the central nervous system (CNS), immunologic responses to cellular components of the adrenal medulla have not been well characterized. To further study the host T cell xenogeneic response to chromaffin and passenger cells of the adrenal medulla, an in vitro lymphocyte proliferation assay was used. Lymphocyte proliferation was determined by mixing rat lymphocytes with potential stimulator cell subpopulations of the bovine adrenal medulla: isolated chromaffin cells, isolated endothelial cells, or passenger nonchromaffin cells, which include a mixture of fibroblasts, smooth muscle cells, and endothelial cells. As a positive control, bovine aortic endothelial cells were also used. 3[H]-thymidine incorporation, corresponding to lymphocyte proliferation, was measured. Results indicated that isolated bovine chromaffin cells produce only a mild, statistically insignificant stimulation of rat lymphocytes. In contrast, there was a significant response to passenger nonchromaffin cells of the adrenal medulla, especially endothelial cells. The inclusion of low levels of cyclosporin A in the cultures completely eliminated the mild proliferative response to isolated bovine chromaffin cells, while near toxic levels were necessary to abrogate the response to endothelial cells. Immunocytochemical analysis revealed that routine chromaffin cell isolation procedures result in the inclusion of a small percentage of endothelial cells, which may be responsible for the slight lymphocyte stimulation. The results of this study indicate that isolated chromaffin cells possess low immunogenicity, and suggest that passenger cells in the adrenal medulla, particularly endothelial cells, may be primarily responsible for progressive rejection in CNS grafts. Thus, removal of passenger nonchromaffin cells from xenogeneic donor tissues prior to transplantation may produce a more tolerated graft in rodent models of neural transplantation.

One-Year Chromaffin Cell Allograft Survival in Cancer Patients with Chronic Pain: Morphological and Functional Evidence

The control of chronic pain through transplantation of chromaffin cells has been reported over the past few years. Analgesic effects are principally due to the production of opioid peptides and catecholamines by chromaffin cells. Clinical trials have been reported with allografts consisting of whole-tissue fragments implanted into the subarachnoid space of the lumbar spinal cord (14,19,36). In the present study, allogeneic grafts were successfully used to control chronic pain in two patients over a period of 1 yr based on patient reported pain scores, morphine intake, and CSF levels of Met-enkephalin. Macroscopic examination at autopsy located the transplanted tissue fragments in the form of multilobulated nodules at the level of the spinal axis and cauda equina. Immunocytochemical microscopy showed neuroendocrine cells are positive for chromagranin A (CGA), and enzymes tyrosine hydroxylase (TH) and dopamine-β-hydroxylase (DβH). The results suggest that there is a relationship between analgesic effect, Met-enkephalin levels in CSF, and the presence of chromaffin cells surviving in spinal subarachnoid space.

Antinociceptive effect of intrathecal microencapsulated human pheochromocytoma cell in a rat model of bone cancer pain

Human pheochromocytoma cells, which are demonstrated to contain and release met-enkephalin and norepinephrine, may be a promising resource for cell therapy in cancer-induced intractable pain. Intrathecal injection of alginate-poly (l) lysine-alginate (APA) microencapsulated human pheochromocytoma cells leads to antinociceptive effect in a rat model of bone cancer pain, and this effect was blocked by opioid antagonist naloxone and alpha 2-adrenergic antagonist rauwolscine. Neurochemical changes of cerebrospinal fluid are in accordance with the analgesic responses. Taken together, these data support that human pheochromocytoma cell implant-induced antinociception was mediated by met-enkephalin and norepinephrine secreted from the cell implants and acting at spinal receptors. Spinal implantation of microencapsulated human pheochromocytoma cells may provide an alternative approach for the therapy of chronic intractable pain.

Selective antinociceptive effects of a combination of the N-methyl-D-aspartate receptor peptide antagonist [Ser(1)]histogranin and morphine in rat models of pain

Numerous rather than a few analgesic endogenous neuropeptides are likely to work in concert in vivo in ameliorating pain. Identification of effective neuropeptide combinations would also facilitate the development of gene or cell-based analgesics. In this study, opioid peptides endomorphin-1 (EM-1) and endomorphin-2 (EM-2) and the peptide histogranin analogue [Ser¹]histogranin (SHG), which possess activity as an N-methyl-d-aspartate (NMDA) receptor antagonist, were intrathecally (i.t.) injected alone and in combination in rat models of acute and persistent pain. None of the peptides when injected alone altered hind paw responses of uninjured rats to acute noxious stimulation. EM-1 and EM-2 showed divergent efficacies in the persistent pain models. For example, EM-1 injected alone was antinociceptive in rats with neuropathic pain, whereas EM-2 demonstrated no efficacy. Demonstration of synergism was also divergent across the models. For example, while SHG combined with EM-1 did not alter the efficacy of EM-1 in rats with neuropathic pain, SHG significantly increased the efficacy of EM-1 in the formalin test. By contrast, the potency and efficacy of the peptides alone and combinations were much less than those of the reference analgesic morphine. Furthermore, morphine combined with the clinically used NMDA receptor antagonist ketamine showed synergism across a broad range of pain states. While the current set of neuropeptides could serve as a basis for analgesic therapeutics, there could be other neuropeptides with greater efficacy and potency and broader therapeutic application.

Cell transplantation as a pain therapy targets both analgesia and neural repair

Cell transplantation is a potentially powerful approach for the alleviation of chronic pain. The strategy of cell transplantation for the treatment of pain is focused on cell-based analgesia and neural repair. (1) Adrenal medullary chromaffin cells and the PC12 cell line have been used to treat cancer pain and neuropathic pain in both animal models and human cases. As biological or living minipumps, these cells produce and secrete pain-reducing neuroactive substances if administered directly into the spinal subarachnoid space. (2) Cell implantation for pain neurorestorative therapy is a new concept and an emerging research field for pain control along with neural repair. Possible neurorestorative mechanisms include neuroprotective, neurotrophic, neuroreparative, neuroregenerative, neuromodulation, or neuroconstructive interventions, as well as immunomodulation and enhancing the microcirculation. These factors may ultimately restore the damaged or irritated condition of the lesioned nerves. The growing preclinical and clinical data show that neural stem/progenitor cells, olfactory ensheathing cells, mesenchymal stromal cells, and CD34(+) cells have the capacity to manage intractable pain and improve neurological functions. Cell delivery routes include local, intrathecal, or intravascular implants. Although these strategies are still in their infancy phase for pain neurorestoratology, cell-based therapies could open up new avenues for the relief of pain. In this review, these aspects are critically analyzed based on our own investigations. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.

Targeted cell reprogramming produces analgesic chromaffin-like cells from human mesenchymal stem cells

Transplantation of allogeneic adrenal chromaffin cells demonstrated the promise of favorable outcomes for pain relief in patients. However, there is a very limited availability of suitable human adrenal gland tissues, genetically well-matched donors in particular, to serve as grafts. Xenogeneic materials, such as porcine and bovine adrenal chromaffin cells, present problems; for instance, immune rejection and possible pathogenic contamination are potential issues. To overcome these challenges, we have tested the novel approach of cell reprogramming to reprogram human bone marrow (BM)-derived mesenchymal stem cells (hMSCs) using cellular extracts of porcine chromaffin cells. We produced a new type of cell, chromaffin-like cells, generated from the reprogrammed hMSCs, which displayed a significant increase in expression of human preproenkephalin (hPPE), a precursor for enkephalin opioid peptides, compared to the inherent expression of hPPE in naive hMSCs. The resultant chromaffin-like cells not only expressed the key molecular markers of adrenal chromaffin cells, such as tyrosine hydroxylase (TH) and methionine enkephalin (Met-enkephalin), but also secreted opioid peptide Met-enkephalin in culture. In addition, intrathecal injection of chromaffin-like cells in rats produced significant analgesic effects without using immunosuppressants. These results suggest that analgesic chromaffin-like cells can be produced from an individual's own tissue-derived stem cells by targeted cell reprogramming and also that these chromaffin-like cells may serve as potential autografts for chronic pain management.

Review of the history and current status of cell-transplant approaches for the management of neuropathic pain

Treatment of sensory neuropathies, whether inherited or caused by trauma, the progress of diabetes, or other disease states, are among the most difficult problems in modern clinical practice. Cell therapy to release antinociceptive agents near the injured spinal cord would be the logical next step in the development of treatment modalities. But few clinical trials, especially for chronic pain, have tested the transplant of cells or a cell line to treat human disease. The history of the research and development of useful cell-transplant-based approaches offers an understanding of the advantages and problems associated with these technologies, but as an adjuvant or replacement for current pharmacological treatments, cell therapy is a likely near future clinical tool for improved health care.

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.

Tyrosine hydroxylase, chromogranin A, and steroidogenic acute regulator as markers for successful separation of human adrenal medulla

Progress in high throughput "-omic" techniques now allows the simultaneous measurement of expression levels of thousands of genes and promises the improved understanding of the molecular biology of diseases such as cancer. Detection of the dysfunction of molecular pathways in diseases requires healthy control tissue. This is difficult to obtain from pheochromocytomas (PHEOs), rare chromaffin tumors derived from adrenal medulla. The two options for obtaining adrenal tissue are: (1) whole organ removal post-mortem or during radical nephrectomy; (2) removal during PHEO surgery. Access to high quality normal adrenal tissue is limited. Removal of whole adrenals during nephrectomy is rare, because of improved surgical techniques. For adrenals removed post-mortem, the lag time to proper organ perfusion causes uncontrolled tissue degradation. Adjacent normal adrenal tissue can almost never be obtained from resected PHEOs, because they often replace the entire medulla or are well-encapsulated. If a margin of normal adrenal is attached to a resected PHEO, it seldom contains any medulla. The clean separation of medulla and cortex is further complicated, because their border is convoluted, and because adult adrenal consists of approximately 90% cortex. Thus, the quality of separation has to be evaluated with specific medullary and cortical markers. We describe the successful dissection of highly pure, medullary tissue from adrenals snap-frozen upon resection during radical nephrectomy or after brain death. Separation quality has been verified by quantitative reverse transcription with polymerase chain reaction for the medullary enzymes, tyrosine hydroxylase, and chromogranin A, and for the cortical enzyme, steroidogenic acute regulator.

Intrathecal analgesia for refractory cancer pain

The use of intrathecal analgesics is an important treatment consideration for many patients with chronic cancer pain. This review describes the various opioid and nonopioid analgesics that have been used in this setting, including morphine, hydromorphone, fentanyl, meperidine, methadone, sufentanil, local anesthetics, clonidine, ketamine, baclofen, midazolam, betamethasone, and octreotide. We discuss available evidence for their analgesic and adverse effects.

Deafferentation Pain Resulting from Cervical Posterior Rhizotomy is Alleviated by Chromaffin Cell Transplants into the Rat Spinal Subarachnoid Space

OBJECTIVE

Deafferentation pain is common after posttraumatic brachial plexus avulsion in humans. Alleviation of such pain is poorly achieved by most therapeutic interventions; the only efficient neurosurgical procedure currently available is lesioning of the dorsal root entry zone. Previous work has demonstrated that adrenal medullary transplants into the lumbar spinal subarachnoid space can alleviate neuropathic pain behavior resulting from peripheral nerve or spinal cord injury. The purpose of this study was to evaluate the potential effects of adrenal medullary transplants on brachial plexus deafferentation pain.

METHODS

The cervical posterior rhizotomy model was selected as an upper segmental deafferentation model because it mimics the pathological situation after traumatic brachial plexus avulsion in humans. Animals underwent a right posterior cervical rhizotomy extending from C5 to T1 and received either adrenal medullary transplants or control striated muscle transplants into the cervical subarachnoid space. The clinical evolution was evaluated daily for self-directed behaviors indicative of ongoing pain, including onset, dermatomal extent, and severity.

RESULTS

In animals with muscle control transplants, self-directed behaviors appeared in 83.3% of the group, with a mean delay between rhizotomy and onset of self-directed behaviors of 8 days. In contrast, only 30.8% of the animals implanted with chromaffin cells exhibited any signs of self-directed behaviors, and these had a mean onset delay of 14 days.

CONCLUSION

The suppression of self-directed behaviors by adrenal medullary transplants is similar to that observed after dorsal root entry zone lesioning and suggests that this approach may offer a nonablative alternative in the management of deafferentation pain resulting from dorsal root avulsion.

Intrathecal analgesic drug therapy

Intrathecal analgesic infusion therapy through an implantable pump system is a sophisticated medical therapy for those who suffer from chronic, severe pain who are unresponsive to traditional medical therapy. This article describes the patient selection and monitoring process and reviews available intrathecal medications and combinations.

Intrathecal grafting of porcine chromaffin cells reduces formalin-evoked c-Fos expression in the rat spinal cord

Chromaffin cells from the adrenal gland secrete a combination of neuroactive compounds including catecholamines, opioid peptides, and growth factors that have strong analgesic effects, especially when administered intrathecally. Preclinical studies of intrathecal implantation with xenogeneic bovine chromaffin cells in rats have provided conflicting data with regard to analgesic effects, and recent concern over risk of prion transmission has precluded their use in human clinical trials. We previously developed a new, safer source of adult adrenal chromaffin cells of porcine origin and demonstrated an in vivo antinociceptive effect in the formalin test, a rodent model of tonic pain. The goal of the present study was to confirm porcine chromaffin cell analgesic effects at the molecular level by evaluating neural activity as reflected by spinal cord c-Fos protein expression. To this end, the expression of c-Fos in response to intraplantar formalin injection was evaluated in animals following intrathecal grafting of 10(6) porcine or bovine chromaffin cells. For the two species, adrenal chromaffin cells significantly reduced the tonic phases of the formalin response. Similarly, c-Fos-like immunoreactive neurons were markedly reduced in the dorsal horns of animals that had received injections of xenogeneic chromaffin cells. This reduction was observed in both the superficial (I-II) and deep (V-VI) lamina of the dorsal horn. The present study demonstrates that both xenogeneic porcine and bovine chromaffin cells transplanted into the spinal subarachnoid space of the rat can suppress formalin-evoked c-Fos expression equally, in parallel with suppression of nociceptive behaviors in the tonic phase of the test. These findings confirm previous reports that adrenal chromaffin cells may produce antinociception by inhibiting activation of nociceptive neurons in the spinal dorsal horn. Taken together these results support the concept that porcine chromaffin cells may offer an alternative xenogeneic cell source for transplants delivering pain-reducing neuroactive substances.

Attenuation of pain perception after transposition of the greater omentum to the cauda equina region of rats--a preliminary observation

BACKGROUND

This paper addresses a specific experimental design to suggest the possible role of the greater omentum in the modulation of pain in rats.

METHODS

Fifteen male Sprague-Dawley rats weighing between 275 and 325 g were selected. The animals were randomized and then anesthetized with pentobarbital (35 mg/kg) and divided into three groups: (1) sham: laparotomy followed by laminectomy with exposure of the spinal epidural space (n=5); (2) transposition of pedicled omentum (n=5) to the cauda equina epidural space; and (3) transposition of pedicled omentum (n=5) to the cauda equina intradural space. The animals were operated upon and once more randomized by an independent investigator, so that the groups were thought to be similar during post-operative testing. The latency of paw withdrawal to noxious heat stimulation was tested and the values (seconds) plotted for 1, 3, 6, 11, 14 and 30 days after surgery. Randomization codes were open after the animals were euthanized. The analysis of variance (ANOVA) without replication was applied for each of the dataset and comparisons established among the different study groups involved. The omenta were removed and standard immunohistochemistry was performed for gamma-amino-butyric acid (GABA), serotonin, calcitonin-gene related protein (CGRP), vascular intestinal peptide (VIP) and Met-enkephalin.

RESULTS

The response to high heating rates of stimulation favored intradural versus sham and epidural omental transpositions. High and low noxious heat stimulation suggested an increased threshold to noxious stimulation after the 3 and 30 days of omental transposition. In the low heat stimulation series, responses were comparatively higher than in the sham animals.

CONCLUSIONS

The suggested increased threshold of response to noxious stimulation after transposition of the greater omentum onto the spinal cord of rats suggested a novel role of the omentum and a potential future application in the clinical arena.

Porcine chromaffin cells, culture, and transplant for antinociceptive effects in rodents and primates

It has been shown that xenografts and allografts of spinally transplanted adrenal chromaffin cells produce antinociception in animals and pain relief in patients with cancer pain. As there is a very limited availability of human adrenal tissue to serve as allografts, the clinical need for xenogeneic chromaffin cells as transplants is obvious. Bovine adrenal glands as a steady source of chromaffin cells have been extensively studied. There is however concern about the possible infection in humans with retrovirus following transplantation. The purpose of this study is to use the pig as a preferred donor animal species for xenotransplantation into rat and monkey. As pigs have been cloned, this opens the door to gene-targeted technologies and allows for genetic modifications, which possibly could improve the efficacy and safety of chromaffin cell transplantation. Porcine chromaffin cells were isolated from adrenal glands of 6-8-month-old pigs. After culturing cells for 1 week in a medium containing serum, the release of met-enkephalin and norepinephrine from the cells was detected by high-performance liquid chromatography and radioimmunoassay with nicotine stimulation, lasting approximately 3 weeks. Transplantation of these cells into the subarachnoid space of rats produced antinociceptive effects on Adelta and C fiber-mediated responses lasting 2-3 weeks. Similar findings were observed in studies with macaque monkeys. Compared with the same number of bovine chromaffin cells, porcine chromaffin cells showed a more robust and longer antinociceptive effect, and could be a better source of cells for human transplantation.

Intrathecal methods

Although the use of opioids for intrathecal anesthesia was first reported in 1901, it was not until 25 years ago that the first report of selective blockade of pain by spinal opioids was described. Since its beginning, the promise of selective analgesics derived from intraspinal administration has generated much development in the field of pain management. In fact, many anesthesiologists who had previously relegated themselves to the confines of the operating room discovered that their needles and catheters could reach even beyond the inpatient wards, affording patients outside the hospital the opportunity to receive neuraxial drugs. The goal of this article is to report on the current state of spinal analgesic chemotherapy as it is now known.

Enhanced antinociception by nicotinic receptor agonist epibatidine and adrenal medullary transplants in the spinal subarachnoid space

Adrenal medullary transplants in the spinal subarachnoid space can reduce nociception, via the release of catecholamines and other analgesic substances, and this may be enhanced by stimulation of transplanted chromaffin cell surface nicotinic acetylcholine receptors (nAChRs). In addition, spinal nAChRs have been implicated in modulating nociception and can interact synergistically with alpha-adrenergic agents. Thus, enhanced antinociception by potent nAChR agonists such as frog skin derivative epibatidine in adrenal-transplanted animals could potentially occur via multiple mechanisms, including nicotinic-alpha-adrenergic synergy and stimulation of chromaffin cell nicotinic receptors. In order to test this, male Sprague-Dawley rats were implanted with intrathecal catheters and either adrenal medullary or control striated muscle transplants in the spinal subarachnoid space at the lumbar enlargement. Animals were tested for nociceptive responses before and after intrathecal injection of several doses of epibatidine using acute analgesiometric tests (tail flick, paw pressure) and the formalin test. After adrenal medullary, but not control, transplantation, nociceptive thresholds to acute noxious stimuli were slightly but consistently elevated, and phase 2 formalin responses decreased. Following intrathecal injection of epibatidine, acute nociceptive response latencies were modestly elevated and phase 2 formalin flinches modestly suppressed in control animals, but only at the highest dose test, with some attendant motor side-effects. In contrast, in adrenal medullary-transplanted animals, epibatidine elevated responses to acute noxious stimuli and markedly suppressed phase 2 formalin responses in a dose-related fashion. The enhanced antinociceptive effect following epibatidine was attenuated with either nAChR antagonist mecamylamine or alpha-adrenergic receptor antagonist phentolamine. The current results demonstrate that intrathecal injection of the nAChR ligand epibatidine can produce significant antinociception in adrenal-transplanted rats in both acute and tonic nociceptive tests and suggest that the use of nicotinic agents in combination with adrenal medullary transplantation could provide maximal therapeutic benefit by synergistically improving antinociception while avoiding the detrimental side-effects of these agents.

Morphine inhibits indolactam V-induced U937 cell adhesion and gelatinase secretion

We demonstrate that indolactam V, a non-phorbol protein kinase C activator, promotes U937 cell attachment to fibronectin, type IV collagen and laminin. In the absence of indolactam V, 2-4% of U937 cells attach to all test substrates, however, in the presence of 100 nM indolactam V, 25, 16 and 11% of U937 cells attach to fibronectin, type IV collagen and laminin, respectively. When added concomitantly, 90 microM H-7, a protein kinase C inhibitor, reduces indolactam V-induced U937 cell adhesion to fibronectin by 91%. Monoclonal antibodies directed against both the beta1 and alpha 5 integrin subunits inhibit indolactam V-induced U937 cell adhesion to fibronectin by 62 and 52%, respectively. Indolactam V also promotes homotypic aggregation in U937 cells, which is blocked with either anti-ICAM or anti-LFA-1 antibodies. In addition, indolactam V promotes U937 cell secretion of a 92 kDa gelatinase as demonstrated by zymography. In the presence of low levels of morphine (10 nM-1.0 microM), the U937 cell attachment to matrix proteins was not significantly affected. However, in the presence of 10 microM morphine, the indolactam V treated cells exhibit a 71-74% reduction in cell adhesion to the matrix proteins. Further, 10 microM morphine also blocks indolactam V-induced homotypic aggregation and gelatinase secretion. The inhibitory effect of morphine on cell-matrix adhesion and gelatinase secretion was not inhibited by the opiate receptor antagonist naloxone (1 microM). While 10 microM naloxone did partially counteract the effect of 10 microM morphine on U937 cell attachment, this effect was likely non-specific since 10 microM naloxone alone increased cell adhesion. Supporting this conclusion, PCR analysis revealed that U937 cells do not express the mu high affinity morphine receptor. Also, indolactam V did not induce mu receptor expression, suggesting that morphine acts on U937 cells in a non-specific fashion.

Only early intervention with gamma-aminobutyric acid cell therapy is able to reverse neuropathic pain after partial nerve injury

Pharmacological treatment for neuropathic pain, although often effective for brief periods, can result in intractable persistent pain with certain patients. Cell therapy for neuropathic pain is a newly developing technology useful for an examination of enhanced normal sensory function after nerve injury with the placement of cells near the spinal cord, and grafts of immortalized cells bioengineered to chronically supply the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) have been used to reverse the chronic pain behaviors. However, it is not known whether there is a therapeutic window for the use of intervention with cell therapy after partial nerve injury. To investigate whether neuropathic pain is sensitive to the timing of placement of cell grafts, neuronal cells bioengineered to synthesize GABA were transplanted in the lumbar subarachnoid space one to four weeks after unilateral chronic constriction injury (CCI) of the sciatic nerve and sensory behaviors were evaluated before and after CCI and transplants. Both thermal hyperalgesia and tactile allodynia were reversed when transplants were placed either one or two weeks after partial nerve injury, compared to maintenance of these behaviors with the injury alone. However, if GABA cells were placed any later than 2 weeks after nerve injury, such intervention was ineffective to reverse the thermal and tactile hypersensitivities induced by the injury. This suggests that altered spinal GABA levels may contribute to the early development of chronic neuropathic pain and that early intervention with cellular therapy to restore GABA may prevent the development of that pain.

Identification of morphine in the adrenal medullary chromaffin PC-12 cell line

Morphine was identified in the adrenal medulla chromaffin PC-12 cell line by reversed-phase HPLC, following liquid and solid extraction. The morphine corresponding HPLC fractions (1.746+/-0.615 ng of morphine/million cells) were further analyzed by gas chromatography-mass spectrometry and found to be identical to synthetic morphine. Furthermore, using primers derived from the human neuronal mu 1 opiate receptor, we used RT-PCR to detect expression of mu transcripts from this cell line. The transcript was absent. The study conclusively proves morphine, but not a mu opiate receptor, is constitutively expressed in the adrenal medulla chromaffin PC-12 cell line.

Developing Techniques and Strategies for the Management of Cancer Pain

The past 20 years have seen a great surge of interest in understanding and treating pain. The introduction of sustained-release opioid delivery systems has tremendously advanced our ability to provide improved pain control. Parenteral opioid delivery systems, although available in many developed nations, remain expensive and cumbersome. New advances in parenteral sustained-release systems are currently in development. These advances include liposomal opioid preparations for intrathecal use, transcutaneous patient-controlled delivery, and implantable diffusion reservoirs. Even more exciting are new developments in tissue engineering that may allow the transplantation of human or animal cells, capable of producing natural analgesic substances, into the vicinity of the spinal cord.

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.

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.

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.

Exocytosis in chromaffin cells of the adrenal medulla

The chromaffin cell has been used as a model to characterize releasable components present in secretory granules and to understand the cellular mechanisms involved in catecholamine release. Recent physiological and biochemical developments have revealed that molecular mechanisms implicated in granule trafficking are conserved in all eukaryotic species: a rise in intracellular calcium triggers regulated exocytosis, and highly conserved proteins are essential elements which interact with each other to form a molecular scaffolding, ensuring the docking of granules at the plasma membrane, and perhaps membrane fusion. However, the mechanisms regulating secretion are multiple and cell specific. They operate at different steps along the life of a granule, from the time of granule biosynthesis up to the last step of exocytosis. With regard to cell specificity, noradrenaline and adrenaline chromaffin cells display different receptor and signaling characteristics that may be important to exocytosis. Characterization of regulated exocytosis in chromaffin cells provides not only fundamental knowledge of neurosecretion but is of additional importance as these cells are used for therapeutic purposes.

Update on cellular transplantation into the CNS as a novel therapy for chronic pain

The transplantation of cells that secrete neuroactive substances with analgesic properties into the CNS is a novel method that challenges current approaches in treating chronic pain. This review covers pre-clinical and clinical studies from both allogeneic and xenogeneic sources. One cell source that has been utilized successfully is the adrenal chromaffin cell, since such cells constitutively release catecholamines, opioid peptides, and neurotrophic factors; release can be augmented with nicotine. Other graft sources include AtT-20 and B-16 cell lines which release enkephalins and catecholamines, respectively. For grafting in rodents, adrenal medullary tissue pieces are transplanted to the subarachnoid space. Chromaffin cell transplants can decrease pain sensitivity in normal rats using standard acute pain tests (paw-pinch, hot-plate, and tail-flick). In addition, transplants can restore normal pain thresholds in rodent models of chronic pain (formalin, adjuvant-induced arthritis, and sciatic-nerve tie) which closely similate the pathologies of human chronic pain conditions. Xenografts have been studied due to concerns that future application for human pain may be limited by donor availability. Despite immune privileges of the CNS, xenografts require at least short-term immunosuppression to obtain a viable graft. Cell encapsulation is one method of sustaining a xenograft (in rat and human hosts) while circumventing the need for immunosuppression. Clinical studies have been initiated for terminal cancer patients with promising results as assessed by markedly reduced narcotic intake, visual analog scale ratings, and increased CSF levels of catecholamines and met-enkephalin.