Steroid minimization in liver transplant recipients: impact on hepatitis C recurrence and post-transplant diabetes

BACKGROUND

Steroid minimization regimens have become increasingly popular for kidney transplant recipients. We studied outcomes for liver transplant recipients with a regimen using rapid discontinuation of prednisone (RDP).

RESULTS

The study group consisted of 83 recipients transplanted between June 2004 and January 2006. Immunosuppression consisted of tacrolimus, MMF, and two doses of basiliximab with six d of steroids. Patients with underlying autoimmune disorders (PSC, autoimmune hepatitis) were not included as they were maintained on steroids. The control group consisted of 83 recipients transplanted between January 2002 and May 2004. Immunosuppression consisted of tacrolimus, MMF and steroids, with no antibody induction. Mean MELD score at time of transplant was significantly higher in the steroid free group vs. the control group (28 vs. 23, p = 0.02); mean donor age was also higher (42 vs. 37 yr, p = 0.02). Other characteristics including recipient age, cold ischemic time, donor source, and cause of liver disease were similar (p = ns). Mean length of follow-up was 16.1 months in the RDP group and 32 months in the control group; a minimum of six months follow up was present for all patients. Patient and graft survival rates were not statistically different in the two groups (p = ns). Biopsy proven rejection was low in both groups and not significantly different (at one yr post-transplant 11% in the RDP group vs. 12% in control, p = 0.53). Based on protocol biopsy data, histologic recurrence of hepatitis C was demonstrated in 56% of the control group hepatitis C positive recipients vs. 39% in the RDP group (p = 0.05). There was a significantly lower incidence of post-transplant diabetes (PTDM) in the RDP vs. control group (at 6 months post-transplant 12% vs. 32%, p = 0.004).

CONCLUSIONS

Rapid discontinuation of prednisone in liver transplant recipients is not associated with an increased risk of rejection, and may be associated with lower morbidity, especially PTDM and hepatitis C recurrence.

Simultaneous liver-kidney transplantation: evaluation to decision making

Questions about appropriate allocation of simultaneous liver and kidney transplants (SLK) are being asked because kidney dysfunction in the context of liver failure enhances access to deceased donor organs. There is specific concern that some patients who undergo combined liver and kidney transplantation may have reversible renal failure. There is also concern that liver transplants are placed prematurely in those with end-stage renal disease. Thus to assure allocation of transplants only to those truly in need, the transplant community met in March 2006 to review post-MELD (model for end-stage liver disease) data on the impact of renal function on liver waitlist and transplant outcomes and the results of SLK.

Once-Daily Tacrolimus Extended Release Formulation: Experience at 2 Years Postconversion From a Prograf-Based Regimen in Stable Liver Transplant Recipients

Compliance with complex immunosuppressant drug therapies in transplant recipients might be improved with regimens that require less frequent dosing. A once-daily extended release (XL) formulation of tacrolimus has been developed that allows a 1:1 conversion from the twice-a-day tacrolimus (TAC) formulation and has a good exposure to trough concentration correlation. In an open-label, multicenter study, stable liver transplant recipients (n=69) were converted from twice-a-day TAC to XL once-daily in the morning, and were maintained for at least 2 years postconversion using the same therapeutic monitoring and patient care techniques employed with TAC. Two years after conversion, the incidence of biopsy-confirmed acute rejection was 5.8% (4 of 69); patient and graft survival was 98.6% (68 of 69). The safety profile of XL was consistent with that previously reported for TAC. Liver transplant recipients can be converted from twice-a-day TAC to once-daily XL and maintained for at least 2 years postconversion with neither unique efficacy nor safety concerns.

Long-term outcomes in liver transplant patients with hepatic C infection receiving tacrolimus or cyclosporine

Choice of calcineurin inhibitor may be a contributing factor to deteriorating patient and graft survival following liver transplantation for hepatitis C virus (HCV). In our multicenter, open-label LIS2T study, de novo liver transplant patients stratified by HCV status were randomized to cyclosporine or tacrolimus. Follow-up data were obtained in an observational study of 95 patients. Mean follow-up was 34 and 37 months, respectively, for cyclosporine-treated (n = 47) and tacrolimus-treated (n = 48) patients. In patients not receiving antiviral therapy, 22 of 31 given cyclosporine (72%) and 24 of 29 given tacrolimus (83%) had biochemical recurrence of HCV. In 68 patients with at least one biopsy, histological evidence of HCV-related hepatitis was present in 27 of 31 (87%) cyclosporine-treated patients and 37 of 37 (100%) tacrolimus-treated patients (P = .02, chi-square test). Three-year actuarial risk of fibrosis stage 2 was 66% with cyclosporine and 90% with tacrolimus; for fibrosis stage 3 or 4 it was 46% and 80%, respectively. Three graft losses were attributed to HCV recurrence in cyclosporine-treated patients and six in tacrolimus-treated patients. Tacrolimus may be associated with increased risk of histological HCV disease recurrence compared to cyclosporine.

Comparison of cyclosporine microemulsion and tacrolimus in 39 recipients of living donor liver transplantation

New immunosuppressive agents and regimens should be evaluated specifically in living donor liver transplant patients due to potential clinical and pharmacokinetic differences between deceased donor and living donor transplant recipients. The analysis presented here is the first direct comparison of clinical outcomes using cyclosporine microemulsion (CsA-ME) with monitoring of blood concentration at 2 hours postdose (C2) and tacrolimus-based immunosuppression in living donor liver transplantation. The analysis was conducted on the data provided by the 39 recipients of a living donor transplant out of the 495 patients enrolled in a 6-month, randomized, prospective, multicenter, open-label study (LIS2T). Patients were randomized to CsA-ME (C2 monitoring) or tacrolimus (monitoring of predose trough drug blood level [C0)]) and were administered corticosteroids with or without azathioprine. Twenty-three living-donor patients received CsA-ME and 16 received tacrolimus. By month 6, 9% of patients receiving CsA-ME and 19% of those receiving tacrolimus had lost their graft or died (not significant [NS]). Nine episodes of biopsy-proven acute rejection were reported: 4 in the CsA-ME group (17%) and 5 in the tacrolimus cohort (31%, NS). There were no significant differences in any safety parameter between groups. The most frequently reported serious adverse events were infections, which occurred in 14 patients in the CsA-ME group (61%) and 13 patients in the tacrolimus arm (81%, NS). Twelve patients in the CsA-ME arm (52%) and 5 in the tacrolimus arm (31%, NS) discontinued the study prematurely. In conclusion, CsA-ME C2 monitoring or tacrolimus both offer effective protection against rejection in living donor liver transplants while maintaining a good safety profile.

Conversion of stable liver transplant recipients from a twice-daily Prograf-based regimen to a once-daily modified release tacrolimus-based regimen

INTRODUCTION

Modified release (MR) tacrolimus is an extended release formulation administered once daily. The purpose of this pharmacokinetic (PK) study was to evaluate tacrolimus exposure in stable liver transplant recipients converted from Prograf twice a day to MR tacrolimus once daily.

METHODS

This was an open-label, multicenter study with a single sequence, four-period crossover design. Eligible patients were 18 to 65 years of age, >6 months posttransplant with stable renal and hepatic function and receiving stable doses of Prograf twice a day for >2 weeks prior to enrollment. Patients received Prograf twice a day on days 1 to 14 and 29 to 42. Patients were converted to the same milligram-for-milligram daily dose of MR once daily on days 15 to 28 and 43 to 56. Twenty-four-hour PK profiles were obtained on days 14, 28, 42, and 56. Laboratory and safety parameters were also evaluated.

RESULTS

Of 70 patients, 62 completed all four PK profiles. The AUC0-24 of tacrolimus was comparable for Prograf twice a day (days 14 and 42) and MR tacrolimus once daily (days 28 and 56). The 90% confidence intervals for MR tacrolimus versus Prograf at steady state (days 28 and 56 vs days 14 and 42) was 0.85 to 0.92 for AUC0-24. MR tacrolimus was well tolerated with a safety profile comparable to that of Prograf. AUC0-24 was highly correlated to Cmin for Prograf (day 14, r = .93; Day 42, r = .89) and for MR tacrolimus (day 28, r = .93; day 56, r = .92). Renal and liver function remained stable. One patient experienced acute rejection.

CONCLUSION

The steady-state tacrolimus exposure of MR tacrolimus once daily is equivalent to Prograf twice a day after a milligram-for-milligram conversion in stable liver transplant recipients.

Living donor and split-liver transplants in hepatitis C recipients: does liver regeneration increase the risk for recurrence?

Concern exists that partial liver transplants (either a living donor [LD] or deceased donor [DD] in hepatitis C virus (HCV)-positive recipients may be associated with an increased risk for recurrence. From 1999 to 2003, at our institution, 51 HCV-positive recipients underwent liver transplants: 32 whole-liver (WL) transplants, 12 LD transplants and 7 DD split transplants. Donor characteristics differed in that WL donors were older, and LD livers had lower ischemic times. Recipient characteristics were similar except that mean MELD scores in LD recipients were lower (p < 0.05). With a mean follow-up of 28.3 months, 46 (90%) recipients are alive: three died from HCV recurrent liver disease and two from tumor recurrence. Based on 1-year protocol biopsies, the incidence of histologic recurrence in the three groups is as follows: WL, 81%; LD, 50% and DD split, 86% (p = 0.06 for LD versus WL). The mean grade of inflammation on the biopsy specimens was: WL, 1.31; LD, 0.33 and DD split, 1.2 (p = 0.002 for LD versus WL; p = 0.03 for LD versus DD split). Mean stage of fibrosis was: WL, 0.96; LD, 0.22 and DD split, 0.60 (p = 0.07 for LD versus WL). Liver regeneration does not seem to affect hepatitis C recurrence as much, perhaps, as factors such as DD status, donor age and cold ischemic time.

Living donor and split-liver transplants in hepatitis C recipients: does liver regeneration increase the risk for recurrence?

Concern exists that partial liver transplants (either a living donor [LD] or deceased donor [DD] in hepatitis C virus (HCV)-positive recipients may be associated with an increased risk for recurrence. From 1999 to 2003, at our institution, 51 HCV-positive recipients underwent liver transplants: 32 whole-liver (WL) transplants, 12 LD transplants and 7 DD split transplants. Donor characteristics differed in that WL donors were older, and LD livers had lower ischemic times. Recipient characteristics were similar except that mean MELD scores in LD recipients were lower (p < 0.05). With a mean follow-up of 28.3 months, 46 (90%) recipients are alive: three died from HCV recurrent liver disease and two from tumor recurrence. Based on 1-year protocol biopsies, the incidence of histologic recurrence in the three groups is as follows: WL, 81%; LD, 50% and DD split, 86% (p = 0.06 for LD versus WL). The mean grade of inflammation on the biopsy specimens was: WL, 1.31; LD, 0.33 and DD split, 1.2 (p = 0.002 for LD versus WL; p = 0.03 for LD versus DD split). Mean stage of fibrosis was: WL, 0.96; LD, 0.22 and DD split, 0.60 (p = 0.07 for LD versus WL). Liver regeneration does not seem to affect hepatitis C recurrence as much, perhaps, as factors such as DD status, donor age and cold ischemic time.

A comparison of surgical outcomes and quality of life surveys in right lobe vs. left lateral segment liver donors

Concern remains regarding the possibly higher risk to living liver donors of the right lobe (RL), as compared with the left lateral segment (LLS). We studied outcomes and responses to quality of life (QOL) surveys in the two groups. From 1997 to 2004, we performed 49 living donor liver transplants (LDLTs): 33 RL and 16 LLS. Notable differences included a higher proportion of female and unrelated donors in the RL group. A significantly larger liver mass was resected in RL (vs. LLS) donors: 720 (vs. 310) g, p = 0.01; RL donors also had greater blood loss (398 vs. 240 mL, p = 0.04) and operative times (7.2 vs. 5.7 h, p = 0.05). However, those findings did not translate into significant differences in donor morbidity. The complication rate was 12.5% in LLS donors and 9.1% in RL donors (p = ns). Per a QOL survey at 6 months postdonation, no significant differences were noted in SF-12 scores for the two groups. Recovery times were somewhat longer for RL donors. Mean time off work was 61.0 days for RL donors and 32.4 days for LLS donors (p = 0.004). RL donation is associated with greater operative stress for donors, but not necessarily with a more complicated recovery or differences in QOL.

Living donor and split-liver transplants in hepatitis C recipients: does liver regeneration increase the risk for recurrence?

Concern exists that partial liver transplants (either a living donor [LD] or deceased donor [DD] in hepatitis C virus (HCV)-positive recipients may be associated with an increased risk for recurrence. From 1999 to 2003, at our institution, 51 HCV-positive recipients underwent liver transplants: 32 whole-liver (WL) transplants, 12 LD transplants and 7 DD split transplants. Donor characteristics differed in that WL donors were older, and LD livers had lower ischemic times. Recipient characteristics were similar except that mean MELD scores in LD recipients were lower (p < 0.05). With a mean follow-up of 28.3 months, 46 (90%) recipients are alive: three died from HCV recurrent liver disease and two from tumor recurrence. Based on 1-year protocol biopsies, the incidence of histologic recurrence in the three groups is as follows: WL, 81%; LD, 50% and DD split, 86% (p = 0.06 for LD versus WL). The mean grade of inflammation on the biopsy specimens was: WL, 1.31; LD, 0.33 and DD split, 1.2 (p = 0.002 for LD versus WL; p = 0.03 for LD versus DD split). Mean stage of fibrosis was: WL, 0.96; LD, 0.22 and DD split, 0.60 (p = 0.07 for LD versus WL). Liver regeneration does not seem to affect hepatitis C recurrence as much, perhaps, as factors such as DD status, donor age and cold ischemic time.

Regionwide sharing for status 1 liver patients--beneficial impact on waiting time and pre- and posttransplant survival

On August 21, 1999, Region 7 of the United Network for Organ Sharing (UNOS) adopted a policy of regionwide sharing of cadaver livers for UNOS Status 1 recipients. We examined what impact this policy had at our center on their waiting times, waiting list mortality, and outcomes. From January 1, 1995, through December 31, 2002, our center listed 39 patients for an emergent (Status 1) transplant, according to the current criteria for Status 1 listing: patients (adult and pediatric) with fulminant hepatic failure (FHF), hepatic artery thrombosis, or primary nonfunction early after a liver transplant, or critically ill pediatric patients with chronic liver disease. These 39 candidates were analyzed in 2 groups: those listed before regionwide sharing (Group I, n = 19) and those listed after (Group II, n = 20). Patient characteristics did not differ significantly between the 2 groups, including mean donor and recipient age, proportion of pediatric patients, and type of graft used (i.e., living or deceased donor, segmental or whole-organ). FHF was the most common cause of liver failure in both groups-74% versus 70% (P = ns). The next most common cause in both groups was hepatic artery thrombosis, followed by primary nonfunction. Most transplants used deceased donors; however, 2 of the transplants in Group I versus only 1 in Group II used living donors. Waiting list mortality (the patient death rate before a transplant could take place) was 32% in Group I versus only 5% in Group II (P =.03). The mean number of days on the waiting list was also substantially lower in Group II (2.9 days) than in Group I, (5.8 days) (P =.04). For patients who underwent a transplant, graft and patient survival rates at 6 months posttransplant were 69.2% in Group I versus 89.5% in Group II (P =.03). In conclusion, the introduction of regionwide sharing seems to have been of benefit for Status 1 patients at our center. They have a significantly lower risk of dying while waiting for a transplant and undergo one in a much shorter period of time.

Liver regeneration after adult living donor and deceased donor split-liver transplants

As the number of living donor (LD) and deceased donor (DD) split-liver transplants (SLTs) have increased over the last 5 years, so too has the interest in liver regeneration after such partial-liver transplants. We looked at liver regeneration, as measured by computed tomography (CT) volumetrics, to see if there were significant differences among LDs, right-lobe LD recipients, and SLT recipients. We measured liver volume at 3 months postoperatively by using CT, and we compared the result to the patient's ideal liver volume (ILV), which was calculated using a standard equation. The study group consisted of 70 adult patients who either had donated their right lobe for LD transplants (n = 24) or had undergone a partial-liver transplant (right-lobe LD transplants, n = 24; right-lobe SLTs, n = 11; left-lobe SLTs, n = 11). DD (vs. LDs) were younger (P < 0.01), were heavier (P = 0.06), and had longer ischemic times (P < 0.01). At 3 months postoperatively, LDs had attained 78.6% of their ILV, less than the percentage for right-lobe LD recipients (103.9%; P = 0.0002), right-lobe SLT recipients (113.6%; P = 0.01), and left-lobe SLT recipients (119.7%; P = 0.0006). When liver size at the third postoperative month was compared with the liver size immediately postoperatively, LDs had a 1.85-fold increase. This was smaller than the increase seen in right-lobe LD recipients (2.08-fold), right-lobe SLT recipients (2.17-fold), and left-lobe SLT recipients (2.52-fold). In conclusion, liver regeneration, as measured by CT volume, seems to be greatest in SLT recipients. LD recipients seem to have greater liver growth than their donors. The reason for this remains unclear.

Model for end-stage liver disease (MELD) and allocation of donor livers

BACKGROUND & AIMS

A consensus has been reached that liver donor allocation should be based primarily on liver disease severity and that waiting time should not be a major determining factor. Our aim was to assess the capability of the Model for End-Stage Liver Disease (MELD) score to correctly rank potential liver recipients according to their severity of liver disease and mortality risk on the OPTN liver waiting list.

METHODS

The MELD model predicts liver disease severity based on serum creatinine, serum total bilirubin, and INR and has been shown to be useful in predicting mortality in patients with compensated and decompensated cirrhosis. In this study, we prospectively applied the MELD score to estimate 3-month mortality to 3437 adult liver transplant candidates with chronic liver disease who were added to the OPTN waiting list at 2A or 2B status between November, 1999, and December, 2001.

RESULTS

In this study cohort with chronic liver disease, 412 (12%) died during the 3-month follow-up period. Waiting list mortality increased directly in proportion to the listing MELD score. Patients having a MELD score <9 experienced a 1.9% mortality, whereas patients having a MELD score > or =40 had a mortality rate of 71.3%. Using the c-statistic with 3-month mortality as the end point, the area under the receiver operating characteristic (ROC) curve for the MELD score was 0.83 compared with 0.76 for the Child-Turcotte-Pugh (CTP) score (P < 0.001).

CONCLUSIONS

These data suggest that the MELD score is able to accurately predict 3-month mortality among patients with chronic liver disease on the liver waiting list and can be applied for allocation of donor livers.

Improved clinical outcomes for liver transplant recipients using cyclosporine monitoring based on 2-hr post-dose levels (C2)

BACKGROUND

A prospective, open-label, study was conducted at 29 centers in 9 countries, involving 307 de novo liver transplant patients to compare the clinical usefulness of monitoring 2-hr post-dose cyclosporine (CsA) levels (C2) with conventional trough cyclosporine blood levels (pre-dose) (C0).

METHODS

Neoral oral therapy was initiated at 15 mg/kg/day and dose adjusted according to predetermined C2 or C0 target level ranges. The primary efficacy variable was treatment failure at 3 months, where evaluation was based on a composite endpoint of biopsy-proven rejection, treatment for rejection, graft loss, death, or premature withdrawal/discontinuation from the study.

RESULTS

Baseline characteristics were similar between groups. Graft loss at 12 weeks (retransplantation or death) occurred in 6.8% C2 and in 7.0% C0 patients. Overall incidence of treated acute rejection was lower for C2 (23.6%) than C0 patients (31.6%) (P=0.144, Cochran-Mantel-Haenszel [CMH] test). In hepatitis C virus (HCV)-negative patients, the incidence of rejection in the C2 group was significantly less than in the C0 group (21.2% vs. 33.0%; P<0.05), whereas in HCV-positive patients, the rejection rate was similar in both groups (26.7% for C2 group vs. 27.3% for C0 group: P=0.81). C2 patients (n=16) who reached minimum target CsA levels by day 3 had a notably low incidence of rejection (12.5%), whereas there was no difference in the incidence of rejection in C0 patients, irrespective of time to reach target level. For biopsy-proven acute rejections (21.6% for C2 vs. 30.4% for C0), the incidence of moderate and severe histological diagnosis was significantly lower in the C2 group than in the C0 group (47% vs. 73%; P=0.01). Safety profiles were similar between the two groups, with few patient withdrawals due to adverse events (9.5% for C2; 7.0% for C0).

CONCLUSIONS

Using C2 monitoring, the overall incidence of acute cellular rejection was lower compared with the C0 group, and the histological severity of acute rejections was shown to be significantly milder for the C2 group, indicative of good long-term prognosis. These data demonstrate that the use of C2 monitoring is superior to C0 and results in a reduction in the incidence and severity of acute cellular rejection without detrimental effect on the drug safety profile.

Penetrating esophageal injuries: multicenter study of the American Association for the Surgery of Trauma

OBJECTIVE

The purpose of this study was to define the period of time after which delays in management incurred by investigations cause increased morbidity and mortality. The outcome study is intended to correlate time with death from esophageal causes, overall complications, esophageal related complications, and surgical intensive care unit length of stay.

METHODS

This was a retrospective multicenter study involving 34 trauma centers in the United States, under the auspices of the American Association for the Surgery of Trauma Multi-institutional Trials Committee over a span of 10.5 years. Patients surviving to reach the operating room (OR) were divided into two groups: those that underwent diagnostic studies to identify their injuries (preoperative evaluation group) and those that went immediately to the OR (no preoperative evaluation group). Statistical methods included Fisher's exact test, Student's T test, and logistic regression analysis.

RESULTS

The study involved 405 patients: 355 male patients (86.5%) and 50 female patients (13.5%). The mean Revised Trauma Score was 6.3, the mean Injury Severity Score was 28, and the mean time interval to the OR was 6.5 hours. There were associated injuries in 356 patients (88%), and an overall complication rate of 53.5%. Overall mortality was 78 of 405 (19%). Three hundred forty-six patients survived to reach the OR: 171 in the preoperative evaluation group and 175 in the no preoperative evaluation group. No statistically significant differences were noted in the two groups in the following parameters: number of patients, age, Injury Severity Score, admission blood pressure, anatomic location of injury (cervical or thoracic), surgical management (primary repair, resection and anastomosis, resection and diversion, flaps), number of associated injuries, and mortality. Average length of time to the OR was 13 hours in the preoperative evaluation group versus 1 hour in the no preoperative evaluation group (p < 0.001). Overall complications occurred in 134 in the preoperative evaluation group versus 87 in the no preoperative evaluation group (p < 0.001), and 74 (41%) esophageal related complications occurred in the preoperative evaluation group versus 32 (19%) in the no preoperative evaluation group (p = 0.003). Mean surgical intensive care unit length of stay was 11 days in the preoperative evaluation group versus 7 days in the no preoperative evaluation group (p = 0.012). Logistic regression analysis identified as independent risk factors for the development of esophageal related complications included time delays in preoperative evaluation (odds ratio, 3.13), American Association for the Surgery of Trauma Organ Injury Scale grade >2 (odds ratio, 2.62), and resection and diversion (odds ratio, 4.47).

CONCLUSION

Esophageal injuries carry a high morbidity and mortality. Increased esophageal related morbidity occurs with the diagnostic workup and its inherent delay in operative repair of these injuries. For centers practicing selective management of penetrating neck injuries and transmediastinal gunshot wounds, rapid diagnosis and definitive repair should be made a high priority.

Psychotropic medications from natural products: a review of promising research and recommendations

Most psychotropic agents employed in allopathic medicine have limited efficacy and significant side effects. Although usually beneficial, synthetic psychotropics are unavailable to approximately 80% of the world's population. Improved understanding of appropriate and safe uses of naturally occurring substances as psychotropic agents will greatly contribute to global mental healthcare. Empirical validation of non-allopathic treatments to ensure safety and efficacy is important because increasing numbers of patients in economically developed countries are using natural substances as medicinal agents. Patients and clinicians often lack accurate information, resulting in poor treatment outcomes or the possibility of drug-drug interactions when herbal medications are used with synthetic psychotropic medications. An important objective of this paper is to distinguish compelling scientific evidence supporting the use of natural products in psychiatry from political or institutional biases that have been misrepresented as scientific arguments. Following an overview of historical, legal, and regulatory issues, this paper presents findings of a systematic literature review on natural products used to treat neuropsychiatric disorders. Significant recent research is reviewed, including emerging treatments of seizure disorders, schizophrenia, dementia and age-related cognitive decline, depression, anxiety states, and substance abuse. Substantial evidence is advanced for safety and efficacy of many natural products used to treat neuropsychiatric symptoms or disorders. Preliminary findings suggest that several treatments based on natural substances are as effective and safe as synthetic pharmaceuticals in current use. Additional studies are indicated to confirm these findings, to elucidate mechanisms of action, and to elaborate standards for safe and appropriate treatment indications. In conclusion, strategic approaches aimed at facilitating improved networking, accelerating promising research directions, and enhancing quality standards of ongoing investigations into putative psychotropic agents from natural sources are recommended.

Reversible programming of pluripotent cell differentiation

We have undertaken an in vitro differentiation analysis of two related, interconvertible, pluripotent cell populations, ES and early primitive ectoderm-like (EPL) cells, which are most similar in morphology, gene expression, cytokine responsiveness and differentiation potential in vivo to ICM and early primitive ectoderm, respectively. Pluripotent cells were differentiated in vitro as aggregates (embryoid bodies) and the appearance and abundance of cell lineages were assessed by morphology and gene expression. Differentiation in EPL cell embryoid bodies recapitulated normal developmental progression in vivo, but was advanced in comparison to ES cell embryoid bodies, with the rapid establishment of late primitive ectoderm specific gene expression, and subsequent loss of pluripotent cell markers. Nascent mesoderm was formed earlier and more extensively in EPL cell embryoid bodies, and resulted in the appearance of terminally differentiated mesodermal cell types prior to and at higher levels than in ES cell embryoid bodies. Nascent mesoderm in EPL cell embryoid bodies was not specified but could be programmed to alternative fates by the addition of exogenous factors. EPL cells remained competent to form primitive endoderm even though this is not the normal fate of primitive ectoderm in vivo. The establishment of primitive ectoderm-like gene expression and inability to participate in embryogenesis following blastocyst injection is therefore not directly associated with restriction in the ability to form extra-embryonic lineages. However, the EPL cell embryoid body environment did not support differentiation of primitive endoderm to visceral endoderm, indicating the lack of an inductive signal for visceral endoderm formation deduced to originate from the pluripotent cells. Similarly, the inability of EPL cells to form neurons when differentiated as embryoid bodies was attributable to perturbation of the differentiation environment and loss of inductive signals rather than a restricted differentiation potential. Reversion of EPL cells to ES cells was accompanied by restoration of ES cell-like differentiation potential. These results demonstrate the ability of pluripotent cells to adopt developmentally distinct, stable cell states with altered differentiation potentials.

Developmental complexity of early mammalian pluripotent cell populations in vivo and in vitro

Early mammalian embryogenesis is characterised by the coordinated proliferation, differentiation, migration and apoptosis of a pluripotent cell pool that is able to give rise to extraembryonic lineages and all the cell types of the embryo proper. These cells retain pluripotent differentiation capability, defined in this paper as the ability to form all cell types of the embryo and adult, until differentiation into the three embryonic germ layers at gastrulation. Our understanding of pluripotent cell biology and molecular regulation has been hampered by the difficulties associated with experimental manipulation of these cells in vivo. However, a more detailed understanding of pluripotent cell behaviour is emerging from the application of molecular technologies to early mouse embryogenesis. The construction of mouse mutants by gene targeting, mapping of gene expression in vivo, and modelling of cell decisions in vitro are providing insight into the cellular origin, identity and action of key developmental regulators, and the nature of pluripotent cells themselves. In this review we discuss the properties of early embryonic pluripotent cells in vitro and in vivo, focusing on progression from inner cell mass (ICM) cells in the blastocyst to the onset of gastrulation.

Lymphocyte targeting of the brain in adoptive transfer cryolesion-EAE

Lymphocyte infiltration and microglial activation in experimental autoimmune encephalomyelitis (EAE) are mainly centred on the spinal cord. However, a cryolesion to one cerebral hemisphere (cryolesion-EAE) induces six-fold enhancement of EAE in the cerebral hemispheres and removal of the cervical lymph nodes reduces such enhancement by 40 per cent. This study tests the hypothesis that lymphocytes from donor rats with cryolesion-EAE will selectively target the brain rather than the spinal cord when transferred to naive recipients. Acute EAE was induced in 15 Lewis rats (donors); ten donors received a cryolesion to the left cerebral hemisphere 8 days post-inoculation of antigen and adjuvant. Five rats with EAE received no cryolesion. Lymphocytes from cryolesion-EAE donors or from EAE-only donors were cultured for 72 h in medium containing myelin basic protein and then injected into a total of 21 naive recipients, which were killed 8 days later. The severity of EAE in brains and spinal cords was assessed in immunocytochemically stained sections by quantifying the number of vessels showing lymphocyte cuffs (W3/13 antibody) and the level of MHC class II antigen expression by microglia (OX6 antibody). When compared with recipients of EAE-only donor lymphocytes, the severity of cerebral EAE was increased 2- to 2.6-fold in the recipients of crylesion-EAE donor lymphocytes (p < 0.01); EAE in the spinal cord was reduced. These results suggest that lymphocytes from cryolesion-EAE donors preferentially target the brain in recipient animals in preference to the spinal cord. By analogy with cryolesion-EAE, focal central nervous system (CNS) damage with drainage of auto-antigens to regional lymph nodes in man may play a role in determining the site and timing of initial and recurrent multiple sclerosis lesions.