Cryopreservation of human brain tissue

Effective cryopreservation of human brain tissue and neural organoids

Human brain tissue models and organoids are vital for studying and modeling human neurological disease. However, the high cost of long-term cultured organoids inhibits their wide-ranging application. It is therefore urgent to develop methods for the cryopreservation of brain tissue and organoids. Here, we establish a method using methylcellulose, ethylene glycol, DMSO, and Y27632 (termed MEDY) for the cryopreservation of cortical organoids without disrupting the neural cytoarchitecture or functional activity. MEDY can be applied to multiple brain-region-specific organoids, including the dorsal/ventral forebrain, spinal cord, optic vesicle brain, and epilepsy patient-derived brain organoids. Additionally, MEDY enables the cryopreservation of human brain tissue samples, and pathological features are retained after thawing. Transcriptomic analysis shows that MEDY can protect synaptic function and inhibit the endoplasmic reticulum-mediated apoptosis pathway. MEDY will enable the large-scale and reliable storage of diverse neural organoids and living brain tissue and will facilitate wide-ranging research, medical applications, and drug screening.

Effects of Hibernation or Cryopreservation on the Survival and Integration of Striatal Grafts Placed in the Ibotenate-Lesioned Rat Caudate-Putamen

Tissue storage prior to intracerebral transplantation would represent a major advantage when conducting clinical transplantation trials in that the procurement of the embryonic donor tissue and the timing of neurosurgery could be planned more efficiently. In the present study, the effects of storing rat embryonic striatal tissue at either +4°C or below freezing temperature prior to grafting to the adult striatum, were assessed with regard to transplant survival, morphology and integration. Eleven days following a unilateral injection of ibotenic acid into the head of the caudate-putamen, a control group of rats received grafts of striatal primordium prepared immediately after dissection from rat embryos (embryonic day 16). A second group of rat embryonic striatal tissue was stored at 4°C (hibernation) for 5 days and then transplanted. A third group of the striatal donor tissue was cryopreserved in liquid nitrogen for 5 days before implantation surgery. Six to seven weeks following transplantation surgery, the grafts were analysed in brain sections processed for acetylcholinesterase histochemistry, DARPP-32 (dopamine and cyclic AMP regulated phosphoprotein with a molecular weight of 32 kDa) and tyrosine hydroxylase (TH) immunocytochemistry. The mean total graft volume and the relative size of the AChE-positive regions were not significantly different between the three groups. Striatal-specific graft regions, positively stained for AChE and DARPP-32, generally exhibited TH immunoreactivity, suggesting that they had received dopaminergic afferents from the host brain. We conclude that embryonic rat striatal tissue can be cryopreserved or hibernated over 5 days without significant impairment in the yield of striatal neurons following intrastriatal implantation and without markedly affecting transplant morphology.

Neural Transplantation in Huntington's Disease: The NEST-UK Donor Tissue Microbiological Screening Program and Review of the Literature

Neural transplantation of human fetal tissue for Huntington's disease (HD) is now entering the clinical arena. The safety of the procedure has now been demonstrated in a number of studies, although the efficacy of such an approach is still being investigated. Stringent but practicable screening of the donor tissue for potential pathogens is an essential prerequisite for successful implementation of any novel transplant program that uses human fetal tissue. In this article we summarize the UK-NEST protocol for the screening of human fetal tissue being grafted to patients with mild to moderate HD. We describe the results of microbiological screening of 87 potential tissue donors in a pilot study, and of the first four donor–recipient patients included in the UK-NEST series. The rationale for the adoption and interpretation of the various tests is described and our methodology is compared with those previously used by other centers. This article therefore presents a comprehensive, logical yet pragmatic screening program that could be employed in any clinical studies that use human fetal tissue for neurotransplantation.

Effects of Deep Cooling and Re-Warming on Ionotropic Glutamatergic Receptors In Vitro

We studied the effects of cooling to -10°C and re-warming to 37°C on slices of rat olfactory cortex. The amplitudes of action potential in the lateral olfactory tract and excitatory postsynaptic potential activated by AMPA recovered during slow cooling/re-warming (0.1°C/min), while during rapid cooling/re-warming (9°C/min), they surpassed the control values. NMDA receptor-dependent mechanism was blocked in both cooling/re-warming modes. Swelling of the brain slices was observed during re-warming, especially during rapid cooling/re-warming. Nerve fibers of the lateral olfactory tract and AMPA-related processes survived deep cooling/re-warming, while NMDA-related processes were irreversibly blocked.

Cryopreservation of cortical tissue blocks for the generation of highly enriched neuronal cultures

In this study, we outline a standardized protocol for the successful cryopreservation and thawing of cortical brain tissue blocks to generate highly enriched neuronal cultures. For this protocol the freezing medium used is 10% dimethyl sulfoxide (DMSO) diluted in Hank's Buffered Salt Solution (HBSS). Blocks of cortical tissue are transferred to cryovials containing the freezing medium and slowly frozen at -1°C/min in a rate-controlled freezing container. Post-thaw processing and dissociation of frozen tissue blocks consistently produced neuronal-enriched cultures which exhibited rapid neuritic growth during the first 5 days in culture and significant expansion of the neuronal network within 10 days. Immunocytochemical staining with the astrocytic marker glial fibrillary acidic protein (GFAP) and the neuronal marker beta-tubulin class III, revealed high numbers of neurons and astrocytes in the cultures. Generation of neural precursor cell cultures after tissue block dissociation resulted in rapidly expanding neurospheres, which produced large numbers of neurons and astrocytes under differentiating conditions. This simple cryopreservation protocol allows for the rapid, efficient, and inexpensive preservation of cortical brain tissue blocks, which grants increased flexibility for later generation of neuronal, astrocyte, and neuronal precursor cell cultures.

Principles and practical issues for cryopreservation of nerve cells

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

Cryopreservation of rat hippocampal slices by vitrification

Although much interest has attended the cryopreservation of immature neurons for subsequent therapeutic intracerebral transplantation, there are no reports on the cryopreservation of organized adult cerebral tissue slices of potential interest for pharmaceutical drug development. We report here the first experiments on cryopreservation of mature rat transverse hippocampal slices. Freezing at 1.2 degrees C/min to -20 degrees C or below using 10 or 30% v/v glycerol or 20% v/v dimethyl sulfoxide yielded extremely poor results. Hippocampal slices were also rapidly inactivated by simple exposure to a temperature of 0 degree C in artificial cerebrospinal fluid (aCSF). This effect was mitigated somewhat by 0.8 mM vitamin C, the use of a more "intracellular" version of aCSF having reduced sodium and calcium levels and higher potassium levels, and the presence of a 25% w/v mixture of dimethyl sulfoxide, formamide, and ethylene glycol ("V(EG) solutes"; Cryobiology 48, pp. 22-35, 2004). It was not mitigated by glycerol, aspirin, indomethacin, or mannitol addition to aCSF. When RPS-2 (Cryobiology 21, pp. 260-273, 1984) was used as a carrier solution for up to 50% w/v V(EG) solutes, 0 degree C was more protective than 10 degrees C. Raising V(EG) concentration to 53% w/v allowed slice vitrification without injury from vitrification and rewarming per se, but was much more damaging than exposure to 50% w/v V(EG). This problem was overcome by using the analogous 61% w/v VM3 vitrification solution (Cryobiology 48, pp. 157-178, 2004) containing polyvinylpyrrolidone and two extracellular "ice blockers." With VM3, it was possible to attain a tissue K(+)/Na(+) ratio after vitrification ranging from 91 to 108% of that obtained with untreated control slices. Microscopic examination showed severe damage in frozen-thawed slices, but generally good to excellent ultrastructural and histological preservation after vitrification. Our results provide the first demonstration that both the viability and the structure of mature organized, complex neural networks can be well preserved by vitrification. These results may assist neuropsychiatric drug evaluation and development and the transplantation of integrated brain regions to correct brain disease or injury.

Cryopreservation of human brain tissue allowing timely production of viable adult human brain cells for autologous transplantation

BACKGROUND

Autologous transplantation is an attractive approach to treat some neurological diseases. A major obstacle is the capacity to produce cells for transplantation at the appropriate time. We describe a cryopreservation procedure for adult human brain tissue allowing the generation of cells in vitro.

METHODS

Neurological resections were dissected to separate white and grey matter. Fractions were frozen in a specific cryopreservation medium containing a selected serum and stored in liquid nitrogen. Tissue was thawed, cells were mechanically dissociated, expanded in culture and characterized by immunochemistry.

RESULTS

Adult human brain tissue cryopreserved for up to two years was successfully used to generate brain cells that could be maintained in culture for up to 100 days. Cells expressed a variety of neuroectodermal markers including GFAP, S100beta, and neurofilament.

CONCLUSION

A successful procedure for cryopreservation of adult human brain tissue has been established that might facilitate future autologous transplantation strategies.

Cryopreservation and primary culture of cerebral neurons from cynomolgus monkeys (Macaca fascicularis)

We established the procedures for cryopreservation and primary culture of fetal cerebral neurons of cynomolgus monkeys (Macaca fascicularis). Three developmental stages of fetuses (80, 93, and 102 days of gestation) were compared to determine the optimal stage of cerebrum development for primary culture. Among the three fetuses, the 80-day-old fetus produced the most process-rich neurons with the highest survival. The number of total recovery cells from the cryopreserved 80-day-old fetus corresponded to 83.4% of that from fresh tissue. Besides, synchronous oscillations of intracellular calcium were first seen in primate cerebral neurons, which suggested the formation of synapse-networks. Cultured neurons expressed synaptophysin protein. Successful cryopreservation and subsequent cell culture of primate neurons would be useful tools for neuroscience research with species specificity.

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

To evaluate whether cryopreservation of porcine ventral mesencephalon cells influences graft survival and function in vivo, we have transplanted either freshly prepared or cryopreserved cells into the striatum of 6-hydroxydopamine-lesioned rats. A single cell suspension of porcine ventral mesencephalon cells from the same isolation either was stored at 4 degrees C and transplanted the next day or was cryopreserved for 4 weeks in liquid nitrogen vapor. The cryopreserved cells were then rapidly thawed, rinsed, and transplanted in the same manner as the fresh cells, with the same dose of viable cells. All animals received daily injections of cyclosporin A to prevent xenograft rejection. To monitor graft function, amphetamine-induced rotation was measured every 3 weeks between 6 and 15 weeks posttransplantation. After sacrifice at 15 weeks posttransplantation, histological methods were used to compare fresh cell and cryopreserved cell transplants with respect to graft survival, differentiation and integration, and host immune response. Cryopreserved cells were found to be either equivalent or in some cases superior to fresh cells with respect to rotational correction, graft survival, graft volume, numbers of graft-derived dopaminergic neurons, and host immune responses. In conclusion, the results indicate that it is feasible to cryopreserve porcine ventral mesencephalon cells for long-term storage of cells prior to transplantation in an animal model of Parkinson's disease.

Cryopreservation of brain tissue for primary culture

Factors affecting recovery of brain cells from cryopreserved cerebral tissues of fetal rats were examined based on yields of viable cells on cell culture. Favorable preservation was obtained with freezing small pieces (less than 1 mm cube) of brain tissues rather than whole tissues or dissociated single cells, and use of 10% dimethylsulfoxide as a cryoprotectant in liquid nitrogen. As for cell preparation procedures, cell survival was improved when tissues were heated at 32 degrees C during papain digestion and centrifugation. Under favorable conditions, the number of brain cells recovered from cryopreserved tissues corresponded to 20-30% of those from fresh control tissues. Immunocytochemical characteristics of cultured neurons, astrocytes, and oligodendrocytes from cryopreserved and fresh tissues were indistinguishable. Semi-quantitive analyses of microtubule-associated protein-2 (MAP-2) and synaptophysin revealed that there was no difference in the amounts of these markers between cultures from both fresh and cryopreserved tissues. These results suggest that most of all cell types including neurons were equally susceptible to the cryopreservation procedures. We concluded that cryopreservation in liquid nitrogen is an effective method for preservation of embryonic brain tissues for later use in cell culture studies.

Methylcellulose during cryopreservation of ventral mesencephalic tissue fragments fails to improve survival and function of cell suspension grafts

Cryopreservation may allow long-term storage of fetal ventral mesencephalon (VM) for transplantation in patients suffering from Parkinson's disease (PD). We investigated whether the polymer methylcellulose protects fetal rat VM during cryopreservation in liquid nitrogen and improves survival and function of this tissue as intrastriatal suspension grafts in the 6-hydroxydopamine (6-OHDA) rat model. VM tissue fragments (E14-E15) were either immediately dissociated and grafted as a cell suspension (FRESH) or cryopreserved under controlled conditions for 7 days in a conventional cryoprotective medium (CRYO) or a medium containing 0.1% methylcellulose (mCRYO) and then dissociated and grafted. Rats from the cryo-groups showed only limited behavioral compensation in contrast to complete compensation observed in rats from the FRESH group. Cryopreservation of fetal rat VM decreased the viability of cell suspensions in vitro to about 70%, survival of grafted tyrosine hydroxylase-immunoreactive (TH-IR) neurons to 11% and 20%, and transplant volume to 8% and 17% (mCRYO and CRYO, respectively, compared to FRESH). The addition of 0.1% methylcellulose to tissue fragments during freezing did neither improve in vitro viability nor survival of TH-IR neurons nor behavioral compensation when compared to the control CRYO group. These results suggest that methylcellulose failed to improve survival of cryopreserved dopaminergic ventral mesencephalic neurons.

Psychiatric status after human fetal mesencephalic tissue transplantation in Parkinson's disease

This report describes the prospective and systematic psychiatric assessment of nine patients who received transplantation of human fetal mesencephalic tissue into the caudate nucleus for treatment of Parkinson's disease. Unlike adrenal medullary transplantation, which often causes psychosis or delirium, this procedure appeared to have few perioperative sequelae. On longer-term follow-up, there was some statistical evidence of deterioration in psychiatric status, as manifested primarily in depressive and nonspecific emotional and behavioral symptoms. This group effect was partly attributable to the occurrence of discrete episodes of illness (major depression and panic disorder with agoraphobia) in some patients, but it was unclear whether such episodes occurred more often than would ordinarily be expected in Parkinson's disease. Differences in the neurobiological effects of fetal mesencephalic and adrenal medullary grafts may account for differences in the psychiatric sequelae of patients receiving these procedures.

Preservation of fetal ventral mesencephalic cells by cool storage: in-vitro viability and TH-positive neuron survival after microtransplantation to the striatum

Preservation of fetal ventral mesencephalic (VM) dopaminergic tissue prior to transplantation has been hampered by the fact that the cells are vulnerable to mechanical and osmotic stress after storage. Previous quantitative studies have shown that cool storage in a so-called 'hibernation medium' prior to grafting, can be used safely for up to 2 days without morphological or functional losses [16,32] using standard transplantation techniques. In the present study on rat fetal VM tissue we have investigated (i) the accuracy of different vital stains (trypan blue exclusion and ethidium bromide stain) to predict in vivo viability of VM cell suspensions after grafting; (ii) the influence of different storage media (glucose-saline, HBSS, DMEM, CO2-independent medium and hibernation medium), temperatures (+4 degrees C or +21 degrees C) and preparations (cell suspension or intact pieces) on the viability scores and total number of cells in vitro; and (iii) the survival and functional effects of intrastriatally grafted VM tissue after preservation by cool storage for up to 12 days using a less traumatic microtransplantation technique. The results show that cool storage at +4 degrees C of intact VM pieces in hibernation medium gives the best in vitro viability scores. Microtransplantation of cell suspensions prepared from cool-stored VM tissue produced good survival of tyrosine hydroxylase (TH)-positive graft neurons for up to 8 days of storage, and functional compensation in the amphetamine-rotation test for up to 12 days of storage. The total yield of surviving TH-positive neurons was unchanged, compared to fresh grafts, after 5 and 8 days of storage, and only reduced by 48% in the grafts stored for 12 days prior to implantation. These findings highlight the potential usefulness of a combination of cool storage and microtransplantation techniques to be able to extend the preservation periods of VM tissue. Such procedures may ultimately help to increase the safety and flexibility in experimental and clinical studies on neural transplantation of dopaminergic neurons.

Long-term survival of dopaminergic neurones in free-floating roller tube cultures of human fetal ventral mesencephalon

Transplantation of human fetal ventral mesencephalon (VM) to Parkinsonian patients has shown beneficial effects in several clinical trials. However, further improvements in the transplantation technique are needed. Delayed surgery, i.e., the in vitro maintenance of the tissue prior to transplantation would present several advantages. The roller tube technique as initially described by Gähwiler (1981) was modified in several aspects for the long-term maintenance of dopaminergic neurones of human fetal VM. Tissue cultures were maintained free-floating in the medium for up to 42 days. The human fetal material was obtained from legal induced suction abortions. The embryonic age ranged from 5 to 12 weeks post-conception. Identification of VM was possible in 43% of the cases. Neurones in cultures were demonstrated by means of immunohistochemistry for tyrosine hydroxylase (TH) and gamma-amino butyric acid (GABA), by electron microscopy and by hybridisation histochemistry using a TH-mRNA-sensitive probe. A high variability in the number of TH-positive cells in individual cultures derived from the same embryo was observed. In 20 microns frozen sections of such tissue cultures the mean +/- SEM of TH-positive cells was 6.5 +/- 1.2/0.1 mm2 (n = 79; range: 0-73). The technique described insures the growth of long-term cultures of human fetal VM.

Human embryonic dopamine neurons xenografted to the rat: effects of cryopreservation and varying regional source of donor cells on transplant survival, morphology and function

When grafting human mesencephalic tissue to patients suffering from Parkinson's disease, the number of surviving dopamine (DA) neurons in the graft is probably crucial. It may be possible to increase the number of DA neurons available for grafting to a patient by pooling tissue from many human embryos collected over several days or by obtaining more DA neurons from each embryo. We have addressed these issues by cryopreserving human mesencephalic DA neurons prior to transplantation and also by grafting human embryonic diencephalic DA neurons. The effects of cryopreservation were assessed 4-15 weeks after xenografting ventral mesencephalic tissue into the DA-depleted striatum of immunosuppressed rats with unilateral 6-hydroxydopamine lesions of the mesostriatal pathway. Control rats grafted with fresh mesencephalic tissue displayed robust reductions in amphetamine-induced turning following transplantation. Functional effects of the cryopreserved mesencephalic grafts were only observed in the one rat out of nine which contained the largest graft in this group. The number of tyrosine hydroxylase immunoreactive neurons in animals transplanted with cryopreserved tissue was significantly reduced to 9% of fresh tissue control grafts. Morphological analysis showed that cryopreserved DA neurons were approximately 22% and 28% smaller regarding the length of the long and short axis, respectively, when compared to the neurons found in fresh grafts. In the second part of the study, the survival and function of human embryonic diencephalic DA neurons were examined following xenografting into the DA-depleted rat striatum. A reduction of motor asymmetry was observed in two out of seven diencephalon-grafted rats. This finding was consistent with a good graft survival in these particular rats, which both contained large grafts rich in tyrosine hydroxylase immunoreactive neurons. Moreover, there was immunopositive staining for graft-derived fibers in the rat striatum containing tyrosine hydroxylase and human neurofilament, both in rats grafted with mesencephalic and diencephalic DA neurons. These findings suggest that cryopreservation, using the current technique, is not a suitable storage method for use in clinical trials of DA neuron grafting in Parkinson's disease. On the other hand, the application of alternative sources of DA neurons may in the future develop into a strategy which can increase the number of neurons obtainable from each human embryo.

Low-pressure aspiration abortion for obtaining embryonic and early gestational fetal tissue for research purposes

Successful transplantation of cadaver embryonic neural tissue is highly dependent on the method used to obtain the tissue. It is important that the tissue not be contaminated bacteriologically by vaginal flora during the procedure, and that it not be disrupted mechanically. A low-pressure aspiration abortion technique has been developed that allows for the safe, effective obtainment of embryonic tissue and reduces the risk of transmitting infection. Tissue was cultured in vitro in 102 cases with minimal evidence of contamination by vaginal flora. Transplants of neural tissue into over 300 rodents have resulted in no intracranial abscesses, even in the setting of immunosuppression. The suction apparatus and low-pressure aspiration minimize disruption of the embryonic tissue. Use of low pressure adds no significant additional risk to the patient. In over 300 cases, there have been no medical complications specifically attributable to the technique. Because local anesthetic is used and sonography is not routinely required, the procedure can easily be performed in an outpatient setting during routine elective abortions, with minimal slowing or disruption of the clinic's surgical schedule. In conclusion, the low-pressure aspiration abortion technique can be safely and effectively used to obtain embryonic and early gestational fetal tissue that is almost always free from bacterial, fungal, and yeast contamination and that is frequently structurally intact. It requires no significant alteration in indications for abortion, risks, methodology, timing of the abortion, or patient management.

Cryopreservation and storage of embryonic rat mesencephalic dopamine neurons for one year: comparison to fresh tissue in culture and neural grafts

Blocks of embryonic rat ventral mesencephalic tissue containing the developing A8-A10 dopamine (DA) cell groups were cryopreserved and stored for approximately 1 year, at which time this tissue was thawed, dissociated into a cell suspension, and compared to a similar preparation of fresh mesencephalic tissue for viability in tissue culture and neural grafts. Estimates of total cell number immediately prior to plating in culture indicated that cryopreserved tissue yields fewer cells, but when this reduced cell number is compensated for, and equal numbers of cells were plated in culture, approximately equal total numbers of neurons, as well as tyrosine hydroxylase (TH)-positive neurons, were present in cultures from cryopreserved and fresh tissue. Grafting of equal numbers of fresh and cryopreserved mesencephalic cells into the striatum of adult rats with large unilateral lesions of the nigrostriatal DA pathway tended to yield smaller grafts with fewer surviving TH-positive cells with less extensive neuronal processes when tissue was previously cryopreserved. However, grafts derived from freeze-stored tissue provided a similar time-course and extent of behavioral recovery in amphetamine-induced rotational tests to that provided by fresh tissue grafts. Taken together, our findings indicate that while cryopreservation of mesencephalic tissue has its costs--reduced cell yield in cultures and grafts, and compromised morphology in grafts--sufficient numbers of cryopreserved neurons survive the grafting procedure to ameliorate behavioral signs of DA depletion in the lesioned rat model.

Neural transplantation for neurodegenerative diseases: past, present, and future

After almost 100 years of sporadic, and marginally successful, studies of neural transplantation in animals, we are now on the threshold of a clinical treatment of the damaged brain. The initial studies of neural transplantation have focused on Parkinson's disease, primarily as a model for a more general strategy of "repair by cellular replacement." Parkinson's is known to result from the loss of a small population of cells that produce the essential neuromodulator, dopamine, for much of the brain. Further, the disease is improved significantly, during the early part of its course, by chemical augmentation of dopamine activity through drug therapies, such as L-dopa. Finally, the disease is often fatal in spite of the best medical treatments, therefore justifying more radical therapeutic experiments. If transplantation of brain cells can be accomplished successfully in humans, as it has been in animals, then replacement of a small population of dopamine-producing cells in Parkinson's disease should have important functional effects and possibly reverse the course and symptoms of the disease. Other useful applications will surely follow for conditions affecting millions of people for whom medicine now has only palliative and ineffective treatments. Just as Parkinson's disease is a model clinical condition for testing cellular replacements, fetal neural tissue transplants are also a first step for a broader strategy of molecular and cellular therapies. Fetal cells are, in many respects, the best replacements one could imagine, since precursor cells have the capacity to develop into every cell found in the adult. So, the best replacement for a dopamine neuron would likely be a precursor dopamine neuron or "neuroblast." Animal research through 1985 had demonstrated the unique properties of such fetal cells, but survivability after transplantation had not been attained with primate or human neural tissue. Our programs developed techniques to transplant monkey fetal neural tissue, to cryopreserve it, and to reverse functional effects of the neurotoxin, MPTP, in monkeys. This technique was applied to the collection and preservation of human tissue, and preliminary successful results have been obtained in patients with idiopathic Parkinson's disease. Others have reported success with different techniques in two MPTP-Parkinsonian patients and a small number of patients with idiopathic disease. If the most dramatic improvements can be replicated consistently and the benefits last for a reasonable period without complications, a clinical treatment might develop using "random-source" fetal cadaver cells.

Susceptibility of human foetal brain tissue to cool- and freeze-storage

Human second trimester foetal brain tissue was stored for a period of 1-6 weeks under various conditions in an attempt to evaluate factors influencing its susceptibility (cell loss) and survivability. Post-storage viability of mesencephalon, striatum, cerebellum and occipital cortex was assessed by a protocol combining vital staining with cell density counts so that tissue viability and cell loss could be evaluated simultaneously; tissue survivability was evaluated by cell culture. A significant amount of cell loss occurred after 24 h storage at room temperature, after one week at 4 degrees C and by two weeks at -20 degrees C in all structures; storage at -196 degrees C resulted in 17-21% cell loss at the end of a 6 week period. At -20 degrees C the cryoprotective effect of 20% FCS was equivalent to that of 15% FCS + 7% DMSO combined, suggesting potential use of serum in replacement of chemical additives. The procedure for removal of DMSO was critical to cell viability and survivability: single step dilution led to 27-39% greater cell loss than slow, multi-step dilutions. In comparison to fresh, non-stored tissue, immunocytochemical characterization of in vitro propagated stored tissue revealed no changes in the populations of major constituent cell types including neurones, dopaminergic neurones, glial and fibroblast cells. These results provide information on possible conditions under which transplant tissue can be satisfactorily stored depending on the prevailing requirements.

Cryopreservation and culture of the human fetal brain tissues

Human embryos after 3-4.5 months of gestation were obtained with abortion. The brain tissue of the bodies was scissored up to obtain 1-3 mm3 pieces, and 7% dimethyl sulfoxide (DMSO), as a cryoprotectant, was added, and then stored at -70 degrees C for 1-30 days or at -196 degrees C for 1-84 days. The survival rate of stored cells was 64%-88%. During 6 days of storage with neuron culture medium, the survival rate of cells at 4 degrees C is over 50% each day, but, as time goes on, the count of the cells is getting less and less. The cells washed out DMSO after cryopreservation and the planting fresh cells can adhere to the wall of the culture bottle, grow, display various forms of neurons and gliacytes. From the above findings, it was suggested that: 1) The fetal human brain tissue, handled properly, can endure cryopreservation with 7% DMSO as a cryoprotective agent; 2) The storage time was related insignificantly to the survival rate of the tissues stored; 3) It is available for a short preservation at 4 degrees C; and 4) It is possible to set up a bank of fetal human brain tissue.

Neurotransplantation: a clinical update

The use of grafts to correct neurological disorders has great promise. The progress toward this goal, as it relates to Parkinson's disease, is briefly reviewed. Although there are a number of questions that remain unanswered, recent reports of improvement in parkinsonian symptoms are very encouraging. In order to successfully evaluate the clinical trials, multicenter and/or standardized reporting techniques will be required. Future studies will need to concentrate on improving the graft survival and ability of the graft to reinnervate the host. Eventually alternative tissues may alleviate the need for fetal tissue. The use of neurotrophic factors should prove an important adjuvant to the repair and restoration of lost neurological function. As this technology is applied to other neurological diseases, it will be important to evaluate the appropriateness of grafting through extensive animal model studies and to balance the potential benefits of such therapy against the degree of risk from surgery and the severity of the disease.

Unilateral transplantation of human fetal mesencephalic tissue into the caudate nucleus of patients with Parkinson's disease

BACKGROUND

Parkinson's disease is characterized by the loss of midbrain dopamine neurons that innervate the caudate and the putamen. Studies in animals suggest that fetal dopaminergic neurons can survive transplantation and restore neurologic function. This report compares the clinical results in four case patients with severe Parkinson's disease who underwent stereotaxic implantation of human fetal ventral mesencephalic tissue in one caudate nucleus with the results in a control group of similar subjects assigned at random to a one-year delay in surgery.

METHODS

Each case patient received cryopreserved tissue from one fetal cadaver (gestational age, 7 to 11 weeks). Before implantation, adjacent midbrain tissue underwent microbiologic, biochemical, and viability testing. Cyclosporine was administered for six months postoperatively.

RESULTS

The procedure was well tolerated. Three case patients showed bilateral improvement on motor tasks, as assessed on videotape, and were more functional in the activities of daily living, as assessed by themselves and neurologists, during both optimal drug therapy and "drug holiday" periods. One case patient, who died after four months from continued disease progression, had striatonigral degeneration at autopsy. In the patients who received transplants, optimal control was achieved with a lower dose of antiparkinsonian medications, whereas the controls required more medication. Positron-emission tomography with [18F]fluorodopa before and after surgery in one patient revealed a bilateral restoration of caudate dopamine synthesis to the range of normal controls, but continued bilateral deficits in the putamen.

CONCLUSIONS

Although the case patients continued to be disabled by their disease, unilateral intracaudate grafts of fetal tissue containing dopamine diminished the symptoms and signs of parkinsonism during 18 months of evaluation.

Cryopreservation, survival and function of intrastriatal fetal mesencephalic grafts in a rat model of Parkinson's disease

In the present study we quantitatively assessed to what extent freeze-storage at liquid nitrogen temperature influences the survival and function of fetal mesencephalic grafts in the dopamine-depleted rat striatum. Ventral mesencephalic (VM) tissue was dissected from rat fetuses and stored overnight in a preservative medium at 4 degrees C (hibernation). It was grafted intrastriatally either as a fresh cell suspension or was frozen as tissue fragments or as a cell suspension after stepwise incubation in ascending concentrations of dimethyl-sulphoxide. Following a cryopreservation interval of 80 days in liquid nitrogen, the frozen samples were rapidly thawed, rinsed, and grafted. Cellular viabilities of graft cell suspensions, as assessed by ethidium bromide/acridine orange staining, were decreased from 90% in fresh tissue to 38-35% in frozen and thawed tissue. Amphetamine-induced turning behavior at 6 weeks post-grafting was significantly attenuated in hosts that had received fresh grafts or grafts that were frozen as tissue fragments. Tyrosine hydroxylase-(TH-) immunocytochemistry of recipient brains revealed significant decreases in TH-positive graft cell numbers in rats grafted with cryopreserved tissue (38-42% of fresh tissue). Moreover, the dye exclusion viability of thawed VM tissue was found to accurately predict the subsequent graft survival. There was no difference with respect to graft cell numbers between the two freezing methods employed, though block storage seems to be more simple from a practical point of view.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel approach to neural transplantation in Parkinson's disease: use of polymer-encapsulated cell therapy

Transplantation of dopaminergic neurons derived from fetal or adrenal tissue into the striatum is a potentially useful treatment for Parkinson's disease (PD). Although initially promising, recent clinical studies using adrenal autografts have demonstrated limited efficacy. The use of human fetal cells, despite promising preliminary results, is complicated by tissue availability and ethical concerns. An attractive alternative is based on encapsulating dopamine-producing cells into polymer capsules prior to transplantation. Polymer capsules can be fabricated to surround the cells with a semi-permeable and immunoprotective barrier. The semi-permeable membrane allows nutrients to enter the capsule, so the encapsulated cells will survive and function, and dopamine and other low molecular weight constituents to diffuse out into the host tissue. Thus, the technique allows use of unmatched human tissue (allografts), or even animal tissue (xenografts) without immunosuppression of the recipient. Cell-loaded polymer capsules can also be retrieved if necessary or desired. The demonstration that striatal implants of encapsulated dopamine-producing cells promote behavioral recovery in rodent and primate models of PD further suggests that cellular encapsulation may be a useful strategy for ameliorating the behavioral consequences of PD.

Cryopreservation and transplantation of immature rat retina into adult rat retina

A bank of freeze-stored donor retinas would free transplantation research from dependence on availability of fresh donor tissue. Donor retinas from E13, E16, E19 and E22 (P1) rat embryos were cryoprotected and stored in liquid nitrogen for up to 8 months. Cryopreserved and fresh donor retinas were grafted to adult rat retina. After 4 weeks survival, transplants were evaluated according to a scoring protocol for the criteria of size, viability, lamination and integration. All donor ages of fresh and cryopreserved retina resulted in successful transplants, with the exception of cryopreserved E13. Cryopreserved grafts were significantly less laminated than grafts of fresh tissue. The best lamination scores of cryopreserved transplants were achieved with donor age E16. Surviving transplants were found in the epiretinal and/or subretinal space. Subretinal transplants had higher viability scores than did epiretinal grafts; the difference was more pronounced with transplants of cryopreserved than with fresh tissue. Fresh subretinal transplants were also significantly better laminated than fresh epiretinal transplants. This study shows that (1) cryopreserved retinal donor tissue can successfully be transplanted to rat retina; and (2) the subretinal space appears to be more favorable than the epiretinal space for retinal transplants.