Mesenchymal Stem Cells (MSCs) are non-hematopoietic multi-potent stem-like cells that are capable of differentiating into both mesenchymal and non-mesenchymal lineages. In fact, in addition to bone, cartilage, fat, and myoblasts, it has been demonstrated that MSCs are capable of differentiating into neurons and astrocytes in vitro and in vivo. MSCs are of interest because they are isolated from a small aspirate of bone marrow and can be easily expanded in vitro. As such, these cells are currently being tested for their potential use in cell and gene therapy for a number of human diseases. Nevertheless, there are still some open questions about origin, multipotentiality, and anatomical localization of MSCs. In this review, we discuss clinical trials based on the use of MSCs in cardiovascular diseases, such as treatment of acute myocardial infarction, endstage ischemic heart disease, or prevention of vascular restenosis through stem cell-mediated injury repair. We analyze data from clinical trials for treatment of osteogenesis imperfecta (OI), which is a genetic disease characterized by production of defective type I collagen. We describe progress for neurological disease treatment with MSC transplants. We discuss data on amyotrophic lateral sclerosis (ALS) and on lysosomal storage diseases (Hurler syndrome and metachromatic leukodystrophy). A section of review is dedicated to ongoing clinical trials, involving MSCs in treatment of steroid refractory Graft Versus Host Disease (GVHD); periodontitis, which is a chronic disease affecting periodontium and causing destruction of attachment apparatus, heart failure, and bone fractures. Finally, we will provide information about biotech companies developing MSC therapy.

Immunosuppression has been sporadically discontinued by noncompliant liver allograft recipients for whom an additional 4 1/2 years of follow-up is provided. These anecdotal observations prompted a previously reported prospective drug withdrawal program in 59 liver recipients. This prospective series has been increased to 95 patients whose weaning was be-

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Our ability to control both the cellular and humoral components of xenograft rejection in laboratory experiments, together with an organ shortage that has placed limits on clinical transplantation services, prompted us to undertake a liver transplantation from a baboon to a 35-year-old man with B virus-associated chronic active hepatitis and human immunodeficiency virus infection.Liver replacement was performed according to conventional surgical techniques. Immunosuppression was with the FK 506-prednisone-prostaglandin regimen used routinely for hepatic allotransplantation, to which a daily non-myelotoxic dose of cyclophosphamide was added. During 70 days of survival, there was little evidence of hepatic rejection by biochemical monitoring or histopathological examination. Products of hepatic synthesis, including clotting factors, became those of the baboon liver with no obvious adverse effects. Death followed a cerebral and subarachnoid haemorrhage that was caused by an angioinvasive aspergillus infection. However, the underlying cause of death was widespread biliary sludge that formed in the biliary tree despite a seemingly satisfactory choledochojejunostomy. During life and in necropsy samples, there was evidence of the chimerism that we believe is integral to the acceptance of both xenografts and allografts.Our experience has shown the feasibility of controlling the rejection of the baboon liver xenograft in a human recipient. The biliary stasis that was the beginning of lethal infectious complications may be correctable by modifications of surgical technique. In further trials, the error of overimmunosuppression should be avoidable.

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We correlated donor and recipient factors with graft outcome in 436 adult patients who underwent 462 liver transplants. Donor variables analyzed were age, gender, ABO blood group, cause of death, length of stay in the intensive care unit, use of pressors or pitressin, need for cardiopulmonary resuscitation, terminal serum transaminases, and ischemia time. Recipient variables analyzed were age, gender, primary diagnosis, history of previous liver transplant, ABO blood group, cytotoxic antibody crossmatch, United Network for Organ Sharing (UNOS) status, and waiting time (except for the cross-match results, they were all known at the time of the operation). The endpoint of the analysis was graft failure, defined as patient death or retransplantation. Using multivariate analysis, graft failure was significantly associated with donor age, donor gender, previous liver transplantation, and UNOS 4 status of the recipient. The effect of donor age became evident only when they were older than 45 years. Livers from female donors yielded significantly poorer results, with 2-year graft survival of female to male 55% (95% CI, 45% to 67%); female to female, 64% (95% CI, 54% to 77%); male to male, 72% (95% CI, 66% to 78%); and male to female, 78% (95% CI, 70% to 88%). The only donors identified as questionable for liver procurement were old (~60 years) women in whom the adverse age and gender factors were at least additive. However, rather than discard even these livers, in the face of an organ shortage crisis, their individualized use is suggested with case reporting in a special category.

Pulmonary infections are a significant cause of morbidity after liver transplantation; Gram-negative bacilli, cytomegalovirus, and Pneumocystis carinii were the usual pulmonary pathogens in the earlier studies in liver transplant recipients receiving cyclosporine. We prospectively assessed the impact of pulmonary infection in 101 consecutive liver transplant recipients receiving the new immunosuppressive agent tacrolimus (FK506). Fifteen percent (15/101) of the patients had 19 episodes of pneumonia; 58% (11/19) of the pneumonias were bacterial, 37% (7/19) were fungal, and 5% (1/19) were protozoal (Toxoplasma gondii). Twenty-seven percent of the bacterial pneumonias were due to Legionella. None of the patients had cytomegalovirus or P carinii pneumonia. Seven percent (7/10) of the study patients had fungal pneumonitis; 4% had invasive aspergillosis and 3% had cryptococcosis. Mortality was significantly higher (53%, 8/15) for patients with pneumonia than for patients without pneumonia (10%, 9/86, P = 0.0004). Only fungal pneumonias were the direct cause of death; 63% (5/8) of the deaths were in patients with fungal pneumonitis. Our data suggest a changing pattern of microbial etiologies of pneumonitis in the era of modern immunosuppressive agents. We show that P carinii pneumonia and cytomegalovirus can be effectively curtailed with appropriate prophylaxis. Fungal infections, on the contrary, not only constituted a major proportion of the pneumonia, but also carried the highest pneumonia-associated mortality. Legionella infections can be overlooked unless specialized laboratory methodology (cultured on selective media, urinary antigen) are applied routinely on all cases of pneumonia. We recommend routine culture on the water supply for Legionella in all transplant centers.

Hepatic retransplantation is controversial because the results are inferior to primary transplants and organs are so scarce. To determine the factors that are associated with poor outcome within the first year following retransplantation, we performed a multivariate analysis, using stepwise logistic regression, of 418 hepatic retransplantations performed at a single institution from November 1987 to December 1993. The minimum follow-up was 1 year. Seven variables were found to be independently associated with subsequent graft failure (defined as either patient death or retransplantation): donor age (odds ratio 2.2 for each lO-year increase over age 45, 95% CI 1.3 to 3.7), female donor sex (odds ratio 1.7,95% CI 1.05 to 2.7), recipient age (odds ratio 1.6 for each 10-year increase over age 45,95% CI 1.2 to 2.3), need for preoperative mechanical ventilation (odds ratio 1.8,95% CI 1.1 to 2.9), pretransplant serum creatinine (odds ratio 1.24 for each increase of 1 mg/dl, 95% CI 1.1 to 1.4), pretransplant total serum bilirubin (odds ratio 1.4 for each 10-mg/dl increase over 15 mg/dl, 95% CI 1.1 to 1.8), and the primary immunosuppressant, using tacrolimus as the reference category (odds ratio for cyclosporine·based immunosuppression 3.9, 95% CI 2.3 to 6.8). Although not part of the logistic regression model, the timing of retransplantation was also found to be important, with the overall probability of failure increasing from 0.58 on day 0 to a peak of 0.8 on day 38 and decreasing slowly after that. The implications of these results reo garding the appropriateness of retransplantation are discussed.