Matrix superhighways configurations: new concepts for complex organ regeneration.

New ideas and experimental models for tissue and organ regeneration are urgently needed. There are several exciting challenges in the field of organogenesis that need to be defined. The integrated signals and molecular repertoires that shape the particular architecture of specific organs like the kidney or the liver are not completely understood yet. To develop a new scientific platform to be able to build up complex organs we have established a research program using basically Acellular Xenogeneic Isomorphic Matrices (AXIMs) and mesenchymal stem cells (MSCs) generating the necessary concepts for the definition, production, and application of the specific configurations of these matrices for organ regeneration. New and interesting pathways for MSC differentiation were identified. We believe that all extracellular matrices were created fundamentally equal or at least very similar in nature. We also believe that there are true "matrix superhighway configurations" with different three-dimensional geometrical architectures as well as biochemical, electrical, and molecular properties that are tissue and organ specific that influence cell differentiation and organogenesis and will be fundamental for the in vitro regeneration of complex organs for transplantation.

Organ donation in Latin America.

Recently in Latin America, there has been a strong influence of the "Spanish model" of organ procurement. In 2001, The "Punta Cana Group" was created by Latin American transplantation coordinators with the objective of registering and improving the system of donation and procurement. In many countries there is no universal financial support from the government for medical treatment, including dialysis and transplantation. In other countries there is complete financial support for all of the population, including immunosuppressive drugs. Practically all countries have transplantation laws that follow ethical concepts, such as brain death diagnosis criteria, forms of consent, criteria of allocation, and inhibition of commerce. The rate of potential donors notified in countries that perform transplantations with deceased donors varied from 6 to 47 per million population yearly (pmp/y); The rate of effective donors varied from 1 to 20 pmp. In 2004, the mean rate of effective donors in Latin America was 5.4 pmp. The family refusal rate for the donation of organs varied from 28% in Uruguay to 70% in Peru. In some countries, such as Puerto Rico, Uruguay, and Cuba, it was more than 15 pmp, whereas in others countries deceased donors were practically not used. The number of patients on the waiting list for solid organ transplants in 12 Latin American countries is 55,000. Although the donation rate has increased by 100% during the last 10 years, it is lower than that in Europe (15 pmm/y) or the United States (20 pmp/y).

Bloodstream cells phenotypically identical to human mesenchymal bone marrow stem cells circulate in large amounts under the influence of acute large skin damage: new evidence for their use in regenerative medicine.

OBJECTIVES: Recent work has shown that human bone marrow contains mesenchymal stem cells (MSCs). However, little is known about their presence in peripheral blood. Since these cells are potentially responsible for tissue repair after injury, their number should be increased during these situations. To demonstrate their number during these situations, we measured MSCs in the peripheral blood of healthy donors and burn patients. MATERIALS AND METHODS: Blood samples were obtained from 15 acute burn patients and 15 healthy donors. We performed flow cytometric analysis, using a large monoclonal antibody panel: CD44, CD45, CD14, DR, CD34, CD19, CD13, CD29, CD105, CD1a, CD90, CD38, CD25. MSC phenotype was considered positive for CD44, CD13, CD29, CD90, and CD105, and negative for the other monoclonals. The testing was performed on day 3 after injury. We correlated the results with the age, sex, and size and type of burns. RESULTS: Cells expressing the MSC phenotype were detected in the peripheral blood of both groups. Noteworthy, compared with samples from healthy donors (0.0078 +/- 0.0044), blood obtained from burn patients showed a higher MSC percentage (0.1643 +/- 0.115; P < .001). The percentage of MSCs correlated with the size and severity of the burn. Increased values were also observed among younger patients. CONCLUSIONS: MSCs have an important role in regenerative processes of human tissues. We found cells phenotypically identical to MSCs circulating in physiological number in normal subjects, but in significantly higher amounts during acute large burns. Therefore, they may represent a previously unrecognized circulatory component to the process of skin regeneration.