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Biomedical subjects

P Aebischer

Publications and source records attributed to P Aebischer.

At least 109 records · Page 6Linked to original sources
PubMed1993

Substance P containing polymer implants protect against striatal excitotoxicity.

The present study examined whether substance P (Sub P) could protect against quinolinic acid (QA)-induced lesions of the striatum, as measured by a loss of striatal D1 dopamine receptors. Sub P was extruded into Evac polymer rods for slow release. One 4 mm rod segment was implanted unilaterally into the striatum of each rat. One week later, animals received a striatal injection of QA (50, 75 or 100 nmol/microliters) medial to the implanted rod. Controls received QA alone. Three weeks later, there was a dose-dependent loss of D1 receptors following QA. Sub P rods protected the striatum from QA-induced D1 receptor loss at this time. These results support the neuroprotection role of Sub P on excitotoxicity.

Animals↗
PubMed1993

Selective neuronal cell attachment to a covalently patterned monoamine on fluorinated ethylene propylene films.

The patterned covalent surface addition of a monoamine to fluorinated ethylene propylene films (FEP) controls both cellular attachment and differentiation in defined media conditions. A radio frequency glow discharge (RFGD) process was used to replace FEP surface fluorine atoms with hydroxyl groups. The primary amine was then covalently attached by polymerizing aminopropyl-triethoxysilane (APTES) via the hydroxyl functionalities. The selective attachment of cells to the APTES regions was determined to be dependent upon the initial adsorption of albumin to the patterned FEP membrane. Albumin was determined to enhance cellular attachment to the APTES regions and prevent attachment to the unmodified FEP areas for both an NB2a neuroblastoma cell line and primary rat endothelial cells. If albumin were not preadsorbed onto the membrane, selective attachment to the modified regions would not occur. Radiolabeling albumin with 125I demonstrated the preference of albumin for adsorption onto the monoamine surface where the cells preferentially attached. Both hydrophobic and ionic forces contributed to the adsorption process. Although selective cellular attachment to the patterned APTES regions could be achieved by albumin preadsorption to the surface, the neuroblastoma cells did not significantly differentiate unless additional serum components were supplemented to the media.

Adsorption↗
PubMed1993

Magnitude and polarity of a fluoroethylene propylene electret substrate charge influences neurite outgrowth in vitro.

Positively charged coating materials such as polylysine improve neuronal attachment in vitro. Due to the structural complexity of these charged molecules, it is unclear whether neuronal effects are due to charge or to physicochemical effects, or both. Polymeric materials with charge storage capabilities and defined surface properties may provide a model in which electrical charge and surface property effects can be separated. Fluorinated ethylenepropylene (FEP) films can store negative or positive charges injected through a corona charging process, thus generating a negative or positive external electrostatic field. In the present study, mouse neuroblastoma (Nb2a) cells were cultured on positive, negative, and uncharged FEP substrates, in both serum-containing and serum-free media. Cell attachment, differentiation, and neurite outgrowth were assessed 24, 48, 72 and 96 h after plating. Electron spectroscopy for chemical analysis (ESCA), contact angle analysis, and scanning electron microscopy (SEM) revealed no differences in surface chemistry and topography between positive, negative, and uncharged FEP. No significant differences in the levels of cell attachment on positive, negative, and uncharged substrates were observed. Significantly higher levels of neurite outgrowth, however, were observed with positive substrates as compared to negative and uncharged substrates, in both media conditions. Substrates charged to +1000 V showed greater levels of outgrowth compared to +500 and +3000 V, suggesting the presence of an optimal range of charge for neurite outgrowth. These results show that cell/charge interactions mediate cell effects on electrically charged substrates with identical surface chemistry, topography and adhesivity.

Animals↗
PubMed1993

Transplantation of a polymer-encapsulated cell line genetically engineered to release NGF.

The delivery of nerve growth factor (NGF) to the lateral ventricle of a fimbria-fornix-lesioned rat prevents the lesion-induced reduction in choline acetyltransferase (ChAT) expression by medial septal cells. Although delivery has been achieved through neural grafting of genetically engineered cell lines which release NGF, transplanted cells have grown beyond the implantation site and formed tumors. The encapsulation of cells within a permselective polymer capsule prior to transplantation allows cell growth only within the capsule space, while allowing molecular exchange between the host tissue and enclosed cells. Rat fibroblasts from the parent cell line (R208F) or fibroblasts genetically modified to produce NGF (R208N.8) were loaded within a thermoplastic hollow fiber-based capsule. Only the capsules loaded with the genetically engineered cells released measurable amounts of NGF in culture. Adult rats received unilateral aspirative fimbria-fornix lesions, followed by intraventricular implantation of a R208F capsule (n = 6) or a R208N.8 capsule (n = 6). After 2 weeks, rats receiving encapsulated cells showed no undue reaction to the implants. With both cell types, the cells remained viable and confined to the capsule space. R208N.8 capsules released sufficient NGF to prevent the lesion-induced loss of septal ChAT expression, whereas R208F capsules did not. This study suggests that encapsulated genetically engineered cells can provide an efficient means for future applications involving delivery of neurotrophic factors.

Acetylcholinesterase↗
PubMed1993

Patterned neuronal attachment and outgrowth on surface modified, electrically charged fluoropolymer substrates.

Fluorinated ethylenepropylene copolymer (FEP) and polyvinylidene fluoride (PVDF) can generate static and transient electrical charges, respectively, after bulk molecular rearrangements induced by electrical charging techniques. Neurons cultured on electrically active FEP and PVDF show increased levels of nerve fiber outgrowth compared to electrically neutral material. The purpose of the present study was to determine if the addition of charged surface groups to the surfaces of FEP and PVDF would modify the influence of bulk electrical charges on cultured neurons. Mouse neuroblastoma (Nb2a) cells were cultured on electrically charged and uncharged FEP and PVDF substrates with covalently modified surfaces containing hydroxyl (OH) and amine (NH2) groups. Surface chemical modification was performed on the entire surface or in discrete striped regions. Nb2a cells cultured on electrically active FEP and PVDF showed greater levels of differentiation than cells on electrically neutral substrates. The presence of NH2 groups attenuated these responses in serum-containing media. Cells attached to NH2 rich surfaces generally displayed a flatter morphology and tended to remain attached for longer time periods. Cells cultured on stripe-modified substrates in serum-containing media showed a strong preferential attachment to modified regions, especially on NH2 stripes. In summary, bulk electrical charges are more important than surface charges in stimulating Nb2a cell differentiation. Surface groups serve to modulate neuronal morphology and confer specific attachment promoting properties in serum-containing media. The development of an optimal neuronal regeneration template may require the incorporation of specific bulk and surface properties.

Animals↗
PubMed1993

Transplants of immunologically isolated xenogeneic chromaffin cells provide a long-term source of pain-reducing neuroactive substances.

Adrenal medullary chromaffin cells are a potential source of neuroactive substances for transplantation into the CNS to alleviate neurochemical deficits. In particular, work in our laboratory has suggested that adrenal medullary transplants in the spinal subarachnoid space can alleviate pain by providing sustained local delivery of catecholamines and opioid peptides. One of the major limitations for clinical application of neural transplantation is the availability of donor material in sufficient quantities. This limitation may be overcome by the use of xenogeneic donors if long-term graft rejection can be prevented. The purpose of this study was to assess whether xenogeneic chromaffin cells immunologically isolated by semipermeable membranes could survive and continue to reduce pain when transplanted into the CNS. Isolated bovine chromaffin cells were encapsulated by semipermeable polymer membranes and implanted into the rat spinal subarachnoid space. Pain sensitivity was assessed at several intervals up to 3 months following implantation. Results indicated that encapsulated bovine chromaffin cell implants, but not empty control capsules, could repeatedly reduce pain sensitivity with nicotine stimulation for the duration of the study. This response was dose related, indicating that pharmacologic integrity of the transplanted chromaffin cells is retained. The analgesia induced by encapsulated chromaffin cell implants could be attenuated by the opiate antagonist naloxone and the alpha-adrenergic antagonist phentolamine, suggesting the involvement of both opioid peptides and catecholamines in mediating this response. In addition, in vitro neurochemical studies of recultured capsules revealed sustained release of Met-enkephalin and catecholamines from encapsulated cells 3 months following implantation into the spinal subarachnoid space.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Growth of tumour cell lines in polymer capsules: ultrastructure of encapsulated PC12 cells.

Recent studies indicate that polymer-encapsulated PC12 cells release sufficient amounts of dopamine to significantly alter behavioural paradigms in animals with unilateral lesions of dopaminergic midbrain neurons. Because cell fine structure provides a useful measure for assessment of storage function, exocytosis, metabolism, cell activity and cell viability, we examined the ultrastructure of PC12 cells grown in semi-permeable polymer capsules maintained in vitro or implanted into the forebrain of rats or guinea pigs. Encapsulated PC12 cells remained viable and continued to divide for the entire evaluation period of six months. Overall morphologies of encapsulated PC12 cells were similar in both environments and they resembled PC12 cells grown in monolayer cultures. In short-term cultures, encapsulated PC12 cells typically contained abundant quantities of chromaffin cell-like granules. The encapsulated cells had initially abundant microvilli on their surfaces which decline in frequency over time. After long-term enclosure for ten weeks or more, fewer secretory granules were detected in the cytoplasm of cells in capsules cultured in vitro and in brain-implanted capsules. Some cells in implanted capsules had long slender filipodia that were not present on PC12 cells in cultured capsules. The morphological changes of PC12 cells may correlate with altered growth conditions such as serum and oxygen concentrations, the presence or absence of growth factors in different environments, and with changes of cell interactions related to cell densities and build up of debris within the capsules over time. Since dopaminergic PC12 pheochromocytoma cells remain viable in semi-permeable polymer capsules for at least six months, such 'cell-capsules' could provide an alternative to dopamine-secreting embryonic neural grafts in dopamine replacement therapies.

Animals↗
PubMed1992

Electrically charged polymeric substrates enhance nerve fibre outgrowth in vitro.

The physical, chemical and electrical properties of synthetic guidance devices are known to influence nerve regeneration in vivo. In the present study, neurons were cultured directly on electrically charged polymer growth substrates to determine if local electrical charges enhance nerve fibre outgrowth in vitro. Piezoelectric polymers such as polyvinylidene fluoride (PVDF) generate transient surface charges under minute mechanical strain. Mouse neuroblastoma (Nb2a) cells were cultured directly on electrically poled (i.e. piezoelectric) and unpoled (i.e. nonpiezoelectric) PVDF substrates in serum-free and serum-containing media. Nerve fibre outgrowth was analysed 24, 48, 72 and 96 h after plating. Piezoelectric PVDF substrates generated 2-3 mV at 1200 Hz when placed on standard incubator shelves and unpoled PVDF substrates showed no output. Nb2a cells grown on piezoelectric substrates exhibited significantly greater levels of process outgrowth and neurite lengths at all time periods for both media conditions. Detailed surface characterization of PVDF substrates using electron spectroscopy for chemical analysis (ESCA) and a comprehensive wettability profile revealed that poled and unpoled PVDF was chemically indistinguishable and showed similar surface wettabilities and adhesive properties. Therefore, we conclude that enhanced process outgrowth was induced by the film's piezoelectric output, making poled PVDF a unique biomaterial for which cell/polymer interactions are mediated predominantly through bulk electrical properties rather than surface properties.

Animals↗
PubMed1992

Polymer-encapsulated PC12 cells: long-term survival and associated reduction in lesion-induced rotational behavior.

Intrastriatal implantation of a dopaminergic cell line surrounded by a permeable, thermoplastic membrane was investigated as a method of long-term dopamine (DA) delivery within the central nervous system (CNS). An increase in DA release from PC12 cell-loaded capsules maintained in vitro was associated with an increase in mitotic activity of the encapsulated cell line. A significant reduction in apomorphine-induced rotational behavior was observed after PC12 cell-containing capsules were implanted into unilaterally 6-hydroxydopamine (6-OHDA) lesioned rats, which was sustained for 24 wk. Four wk after implantation, microdialysis studies revealed the presence of DA near PC12 cell-containing capsules, which was comparable to extracellular striatal levels of unlesioned controls. Extracellular striatal DA was undetectable by microdialysis in lesioned animals near empty polymer capsules. Histological analysis after 24 wk in vivo demonstrated that encapsulated PC12 cells survived, continued to express tyrosine hydroxylase, and that encapsulation prevented tumorigenesis. The data suggested that the release of a diffusible substance, most likely DA, from an implant is sufficient to exert a long-term functional influence upon 6-OHDA unilaterally lesioned rats and that capsules containing DA-secreting cells may be an effective method of long-term DA delivery in the CNS.

Acrylic Resins↗
PubMed1992

Syngeneic Schwann cells derived from adult nerves seeded in semipermeable guidance channels enhance peripheral nerve regeneration.

At present, clinical strategies to repair injured peripheral nerve concentrate on efforts to attain primary suture of the cut nerve ends. If this is not possible, autografts are used to unite the separated nerve segments. Both strategies are based on the recognition that the Schwann cells resident in the peripheral nerve trunk play a crucial role in the regenerative process. Neither strategy may be feasible, however, in extensive or multiple injuries because the amount of autograft material is limited, and allografts are subject to immune rejection. Artificially produced nerve bridges constructed of autologous Schwann cells seeded in guidance channels could be used to overcome these limitations. In the present experiments, the potential of Schwann cells derived from adult nerves and seeded in permselective guidance channels to promote neurite regeneration across an 8 mm nerve gap was evaluated in transected rat sciatic nerves. Immunological sequalae were evaluated by comparing Schwann cells from syngeneic and heterologous rat strains. Schwann cells from either adult outbred (Sprague-Dawley, CD) rats or inbred (Fisher, F) rats were suspended in a Matrigel solution at a density of 80 x 10(6) cells/ml (CD) or 40, 80, or 120 x 10(6) cells/ml (F-40, F-80, and F-120 channels, respectively). Channels containing Schwann cells were compared to sciatic nerve autografts, empty channels, or channels filled with Matrigel alone. One day after seeding permselective synthetic guidance channels with a Schwann cell suspension, a central cable of Schwann cells oriented along the axis of the tube was formed due to syneresis of the hydrogel. By 3 weeks postimplantation, regenerating axons had grown into all channels and autografts. Sciatic nerve autografts supported extensive regeneration, containing 4-5 x 10(4) myelinated axons at the graft midpoint. The ability of channels containing syngeneic Schwann cells to foster regeneration was dependent on the Schwann cell seeding density. At the channel's midpoint, the myelinated axon population in F-120 tubes was intermediate between that in sciatic nerve autografts and F-80 channels, and was significantly higher than in F-40 or control channels. The nerve cable in Schwann cell-containing tubes consisted of larger, more organotypic fascicles than acellular control channels. In contrast, heterologous (CD) Schwann cells elicited a strong immune reaction that impeded nerve regeneration. The present study shows that cultured adult syngeneic Schwann cells seeded in permselective synthetic guidance channels support extensive peripheral nerve regeneration.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Comparison of dorsal and ventral spinal root regeneration through semipermeable guidance channels.

Semipermeable guidance channels have been shown to support nerve regeneration in the peripheral nervous system (PNS) possibly through interactions with the wound healing environment. This study quantitatively assesses the ability of such channels to support regeneration in the PNS segment of the spinal roots across a 4 mm gap and compares the resultant dorsal and ventral root regeneration. Acrylic copolymer guidance channels with a molecular weight (Mw) cutoff of 50,000 Da were used in a transected rat spinal root model. Cohorts of 23 animals (11 ventral, 12 dorsal) were examined at four weeks; 6 animals (3 ventral, 3 dorsal) at ten weeks; and 10 animals (5 ventral, 5 dorsal) at twenty-four weeks post-implantation. Both the dorsal and ventral roots were able to regenerate across the gap within the semipermeable channel. At all time periods, the regenerated dorsal roots contained fewer myelinated axons than found in the contralateral control root and consisted of an abundance of collagenous tissue. In contrast, by ten weeks the regenerated ventral roots contained twice the contralateral control number of myelinated axons and were composed predominantly of large, myelinated axons. At twenty-four weeks the number of unmyelinated axons was also quantified, with the regenerated dorsal root containing only one-fifth of the control number and the regenerated ventral root containing more than four times the control. Due to the proximity of the dorsal root lesion to the axonal cell bodies, the dorsal root ganglion (DRG) neuronal cell loss was investigated at four weeks post-implantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Transplantation of microencapsulated bovine chromaffin cells reduces lesion-induced rotational asymmetry in rats.

Surrounding bovine chromaffin cells by a semipermeable membrane may protect the transplanted cells from a host immune response and shield them from the inflammatory process resulting from the surgical trauma. Encapsulation of the chromaffin cells was achieved by interfacial adsorption of a polycation on a polyanionic colloid matrix in which the chromaffin cells were entrapped. Basal and potassium-evoked release of catecholamines from encapsulated bovine chromaffin cells was analyzed over a 4-week period in vitro. Norepinephrine and dopamine release remained constant over time whereas epinephrine release significantly decreased. The chromaffin cells also retained the capacity for depolarization-elicited catecholamine release 4 weeks following the encapsulation procedure. Morphological analysis revealed the presence of intact chromaffin cells with well-preserved secretory granules. Striatal implantation of chromaffin cell-loaded capsules significantly reduced apomorphine-induced rotation compared to empty polymer capsules in animals lesioned with 6-hydroxydopamine for at least 4 weeks. Intact chromaffin cells expressing tyrosine hydroxylase and dopamine-beta-hydroxylase were observed in all capsules implanted in the striatum for 4 weeks. The assessment of the clinical potential of transplanting encapsulated adrenal chromaffin cells of either allo- or xenogeneic origin for Parkinson's disease will require long-term behavioral studies. The present study suggests, however, that the polymer encapsulation procedure may offer an alternative to adrenal autografts as a source of dopaminergic tissue.

Animals↗
PubMed1991

Repair of the blood-brain barrier following implantation of polymer capsules.

Past studies of polymer-encapsulated cell lines implanted in the brain indicated their usefulness for transmitter replacement therapy in animal models. Such grafts may have potentially important clinical applications, but their placement into neural parenchyma may cause a traumatic injury resulting in a leaky blood-brain barrier around the implant. This study investigated whether or not injury repair and reformation of the barrier takes place near a polymer capsule implanted in the brain of Sprague-Dawley rats. The two methods used for detection of a leaky barrier were immunocytochemical localization of extravasated serum albumin and circulating Evans blue that binds to serum albumin. Immunocytochemical staining for glial filament protein provided a measure for evaluating injury associated gliosis. Polymer capsules implanted for 10, 16 and 18 days were surrounded by microvessels that leaked detectable quantities of serum albumin into interstitial spaces and, by secondary uptake, into some nearby neurons and reactive astrocytes. Reactive astroglia were observed within the outer regions of the capsule wall and in the near vicinity of the implant after these early survival times. In contrast, at post-implantation times of 46 and 54 days, serum albumin was no longer detected in the neural parenchyma near the macrocapsules and only few reactive astrocytes remained. These findings show that polymer capsules implanted within the cerebrum permit (a) reformation of the blood-brain barrier and (b) occurrence of repair processes that lead to minimal deposition of reactive astroglia near the implanted polymer capsule.

Animals↗
PubMed1991

Mast cells and tissue reaction to intraperitoneally implanted polymer capsules.

The inflammatory reaction to implanted biomaterials often compromises the clinical usefulness of implantable devices. Dexamethasone, an anti-inflammatory agent, acts on macrophages to decrease production of inflammatory mediators, and on mast cells to prevent degranulation. Systemic administration of dexamethasone (dms) in rats decreases the tissue reaction to intraperitoneally implanted vinyl chloride-acrylic copolymer capsules. Local release of even smaller amounts of dms from a polymeric substrate placed inside an acrylic copolymer capsule may control the tissue reaction while avoiding the undesirable side effects of systemic treatment. Such a system also allows investigation of the local effect of soluble molecules on tissue-material interactions without altering the surface properties of the implant or adding the effect of a releasing material. In the present study, we investigated the effect of dms released from ethylene vinyl acetate (EVAc) rods placed in acrylic copolymer capsules and implanted in the peritoneal cavity of rats. In vitro the release of dms from EVAc rods was quasilinear for 5 weeks. When implanted intraperitoneally into rats, polymer capsules containing EVAc/dms rods generated a tissue reaction that was significantly thinner and featured fewer fibroblast and collagen layers than that around capsules containing pure EVAc rods at all time points studied. The tissue reaction layer was also thinner than that previously described in rats treated systemically with dms. The trabeculae of implants with dms-loaded EVAc rods contained significantly more intact mast cells than implants with EVAc alone, suggesting that degranulation of mast cells is involved in the tissue reaction to intraperitoneal polymer implants.

Analysis of Variance↗
PubMed1991

Peripheral nerve regeneration is impeded by interleukin-1 receptor antagonist released from a polymeric guidance channel.

Interleukin-1 receptor antagonist (IL-1ra), a true antagonist of the interleukin-1 (IL-1) receptors, is released by activated macrophages and binds specifically to the IL-1 receptors without triggering IL-1 effects. Following peripheral nerve axotomy, activated macrophages release IL-1, which induces the expression of nerve growth factor (NGF) mRNA in Schwann cells. IL-1ra may therefore impede peripheral nerve regeneration by blocking the NGF-mediated effect of IL-1. Peripheral nerve regeneration occurring through polymeric guidance channels releasing IL-1ra was investigated in a 4-mm gap transected mouse sciatic nerve model. Cohorts of five animals were implanted with tubes releasing either bovine serum albumin (BSA), BSA with IL-1ra, or BSA with deactivated IL-1ra (dIL-1ra) for 4 weeks. In vitro release kinetics indicated that after an initial burst, IL-1ra release was linear for the next 3 1/2 weeks. Following implantation of a polymeric guidance channel, a regenerated cable bridged the nerve gap in all animals. The cables were similar in size and were composed of nerve microfascicles containing both unmyelinated and myelinated axons in association with their Schwann cells. Tissue regenerated in tubes releasing BSA-IL-1ra contained, however, significantly fewer myelinated and unmyelinated axons and blood vessels than did tubes releasing BSA alone or BSA-dIL-1ra. We conclude that a naturally occurring antagonist of IL-1 receptors impedes peripheral nerve regeneration, suggesting that macrophages play an essential role in controlling peripheral nerve regeneration through the release of stimulatory and/or inhibitory molecules.

Animals↗
PubMed1991

Behavioral recovery following intrastriatal implantation of microencapsulated PC12 cells.

The motor deficits associated with Parkinson's disease may be ameliorated by intrastriatal placement of dopamine-secreting cells in a polymer capsule. Water soluble polyelectrolytes were utilized for membrane encapsulation of dopamine-secreting PC12 cells. Membrane permeability studies revealed exclusion of radiolabeled 69,000 Da albumin, whereas 30,000 Da carbonic anhydrase was able to cross the membrane. No cytolytic activity was observed following incubation of the encapsulated PC12 cells with PC12 cell-directed antiserum and fresh complement. In vitro, dopamine release and the surface area of intact cells per microcapsule, reached a plateau at 4 weeks that was maintained for at least 12 weeks. Viable PC12 cells were observed in microcapsules implanted for 4 and 8 weeks in nonlesioned guinea pig striata. The behavioral effect of intrastriatal dopamine release from microencapsulated PC12 cells was evaluated in the 6-hydroxydopamine unilaterally lesioned rat model. From 1 to 4 weeks postimplantation a significant reduction in rotation behavior under apomorphine challenge was observed with PC12 cell-loaded microcapsules as compared to empty microcapsules. Tyrosine hydroxylase immunopositive PC12 cells were observed 4 weeks postimplantation in all animals exhibiting a reduction in turning behavior. Implantation of polymer-encapsulated cells may provide a means for long-term delivery of neurotransmitters and growth factors to the nervous system.

Animals↗
PubMed1991

Long-term cross-species brain transplantation of a polymer-encapsulated dopamine-secreting cell line.

Cross-species transplantation of dopamine-releasing cell lines protected against immune rejection by a semi-permeable synthetic membrane may provide a source of neurotransmitters for the treatment of Parkinson's disease. Experiments were carried out to assess whether polymer-encapsulated PC12 cells, a catecholaminergic cell line derived from a rat pheochromocytoma, could survive in vitro as well as in vivo after implantation in the striatum of adult guinea pigs. When maintained in vitro, the encapsulated PC12 cells exhibited good survival, proliferated, and spontaneously released dopamine for at least 6 months. They also retained the capacity for depolarization-elicited dopamine release. In vivo, well-preserved tyrosine hydroxylase-positive PC12 cells were observed in capsules implanted for 4, 8, and 12 weeks. Unencapsulated PC12 cells or cells in nonintact capsules did not survive transplantation at any of these time periods. The survival of encapsulated PC12 cells transplanted across species suggests that polymer encapsulation may provide an alternative for xenotransplantation of secretory cells in the absence of systemic immunosuppression.

Adrenal Gland Neoplasms↗