Engineering bone tissue from human embryonic stem cells.

In extensive bone defects, tissue damage and hypoxia lead to cell death, resulting in slow and incomplete healing. Human embryonic stem cells (hESC) can give rise to all specialized lineages found in healthy bone and are therefore uniquely suited to aid regeneration of damaged bone. We show that the cultivation of hESC-derived mesenchymal progenitors on 3D osteoconductive scaffolds in bioreactors with medium perfusion leads to the formation of large and compact bone constructs. Notably, the implantation of engineered bone in immunodeficient mice for 8 wk resulted in the maintenance and maturation of bone matrix, without the formation of teratomas that is consistently observed when undifferentiated hESCs are implanted, alone or in bone scaffolds. Our study provides a proof of principle that tissue-engineering protocols can be successfully applied to hESC progenitors to grow bone grafts for use in basic and translational studies.

Acquired hemoglobin variants and exposure to glucose-6-phosphate dehydrogenase deficient red blood cell units during exchange transfusion for sickle cell disease in a patient requiring antigen-matched blood.

Red blood cell exchange (RBCEx) is frequently used in the management of patients with sickle cell disease (SCD) and acute chest syndrome or stroke, or to maintain target hemoglobin S (HbS) levels. In these settings, RBCEx is a category I or II recommendation according to guidelines on the use of therapeutic apheresis published by the American Society for Apheresis. Matching donor red blood cells (RBCs) to recipient phenotypes (e.g., C, E, K-antigen negative) can decrease the risk of alloimmunization in patients with multi-transfused SCD. However, this may select for donors with a higher prevalence of RBC disorders for which screening is not performed. This report describes a patient with SCD treated with RBCEx using five units negative for C, E, K, Fya, Fyb (prospectively matched), four of which were from donors with hemoglobin variants and/or glucose-6-phosphate dehydrogenase (G6PD) deficiency. Pre-RBCEx HbS quantification by high performance liquid chromatography (HPLC) demonstrated 49.3% HbS and 2.8% hemoglobin C, presumably from transfusion of a hemoglobin C-containing RBC unit during a previous RBCEx. Post-RBCEx HPLC showed the appearance of hemoglobin G-Philadelphia. Two units were G6PD-deficient. The patient did well, but the consequences of transfusing RBC units that are G6PD-deficient and contain hemoglobin variants are unknown. Additional studies are needed to investigate effects on storage, in-vivo RBC recovery and survival, and physiological effects following transfusion of these units. Post-RBCEx HPLC can monitor RBCEx efficiency and detect the presence of abnormal transfused units.

De novo thrombotic microangiopathy in renal transplant recipients: a comparison of hemolytic uremic syndrome with localized renal thrombotic microangiopathy.

BACKGROUND: Thrombotic microangiopathy (TMA) is a well-recognized and serious complication of renal transplantation, affecting 3% to 14% of patients administered calcineurin-inhibitor-based immunosuppression. METHODS: We reviewed 1,219 biopsy reports of 742 kidney and kidney-pancreas transplants performed during 15 years at our center and found 21 biopsy-confirmed cases of TMA. RESULTS: On presentation, the majority (62%) had systemic TMA with manifest hemolysis and thrombocytopenia, whereas a subset had TMA localized only to the graft (38%). There were no statistically significant differences in sex, type of transplant, age, race, or type of immunosuppression. Patients with systemic TMA were more likely to be treated with plasma exchange (38% versus 13%; P < 0.05), more often required dialysis therapy (54% versus 0%; P = 0.01), and had a greater rate of graft loss (38% versus 0%; P < 0.05). No patient with the localized variant had TMA-related graft loss. Patients with localized TMA often responded to reduction, conversion, or temporary discontinuation of calcineurin-inhibitor-based immunosuppression therapy and did not routinely require plasma exchange for graft salvage. We compare our findings with the literature regarding the prognosis of TMA. CONCLUSION: Classifying patients with post-renal transplantation TMA into those with localized and systemic disease is clinically useful because each group has distinct characteristics and clinical courses.

Two third-year medical student-level laboratory shock exercises without large animals.

BACKGROUND: Historically, medical schools have taught principles of hemodynamic shock using large animal models. Such exercises are infrequent today due to the increasing aversion of students and the wider community to the use of large animals in teaching. Herein, we describe two alternative exercises that communicated basic science and clinical principles of shock effectively. METHODS: We developed two complementary, distinct single-afternoon laboratory exercises for third-year medical students. The first exercise (lab) demonstrated three principles: (1) in vitro cytokine-induced apoptosis (illustrating mechanisms and consequences of sepsis), (2) the hemodynamic manifestations of hypovolemia and septic shock in rats, and (3) the effects of fluid resuscitation or vasopressor administration in these same rat models. In the second exercise, students managed the diagnosis, initial resuscitation, surgical treatment, and ICU care of a "patient" with abdominal sepsis, using a manikin-based patient simulator and actual patient test data. Current basic science and clinical literature were incorporated. RESULTS: Efficacy was evaluated by polling students in one of four rotations (n = 25). Educational value of the lab exercise was rated 3.70 (1, worst rating; 5, best rating), whereas its applicability to clinical care was rated 4.35. Educational value and clinical applicability of the patient simulator were rated 4.52 and 4.76, respectively. CONCLUSIONS: These exercises combining laboratory demonstrations of the pathophysiologic mechanisms and manifestations of shock with simulation were judged effective and clinically relevant while fulfilling the National Institutes of Health (NIH) mandate to reduce use of experimental animals.