RESUMEN
We used cre/loxP-based genetic lineage tracing analysis to test a previously proposed hypothesis that in vitro cultured adult pancreatic beta-cells undergo epithelial-mesenchymal transition (EMT) to generate a highly proliferative, differentiation-competent population of mesenchymal islet "progenitor" cells. Our results in the mouse that are likely to be directly relevant to the human system show that adult mouse beta-cells do not undergo EMT in vitro and that the mesenchymal cells that arise in cultures of adult pancreas are not derived from beta-cells. We argue that these cells most likely originate from expansion of mesenchymal cells integral to the heterogeneous pancreatic islet preparations. As such, these mesenchymal "progenitors" might not represent the best possible source for generation of physiologically competent beta-cells for treatment of diabetes.
Asunto(s)
Células Epiteliales/citología , Células Secretoras de Insulina/citología , Mesodermo/citología , Animales , Sitios de Ligazón Microbiológica/genética , Técnicas de Cultivo de Célula , Diferenciación Celular , División Celular , Células Cultivadas , Expresión Génica , Genes Reporteros/genética , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Células Secretoras de Insulina/metabolismo , Integrasas/genética , Integrasas/metabolismo , Ratones , Ratones Transgénicos , RatasRESUMEN
Regenerative medicine aims to restore homeostasis of diseased tissues and organs. With time, engineered replacement tissue constructs will play an increasingly important role in achieving this goal. Equally important, however, will be the ability to resolve disease-associated inflammation and to optimize tissue regenerative capacity by specifically patterning the host tissue microenvironment. The tools of bioengineering are uniquely suited to meet these challenges. Here, the candidate molecular and cellular targets for manipulating the host's inflammatory environment and tissue regenerative capacity are briefly discussed within the context of current and emerging bioengineering strategies. The objective is to draw the attention of basic scientists and engineers to the importance of regulating inflammation in achieving the goals of tissue engineering and regenerative medicine.
Asunto(s)
Regeneración/fisiología , Ingeniería de Tejidos , Cicatrización de Heridas/fisiología , Animales , HumanosRESUMEN
Transplantation of pancreatic islets can provide long-lasting insulin independence for diabetic patients, but the current islet supply is limited. Here we describe a new in vitro system that utilizes adult human pancreatic islet-enriched fractions to generate hormone-producing cells over 3-4 weeks of culture. By labeling proliferating cells with a retrovirus-expressing green fluorescent protein, we show that in this system hormone-producing cells are generated de novo. These hormone-producing cells aggregate to form islet-like cell clusters. The cell clusters, when tested in vitro, release insulin in response to glucose and other secretagogues. After transplantation into immunodeficient, nondiabetic mice, the islet-like cell clusters survive and release human insulin. We propose that this system will be useful as an experimental tool for investigating mechanisms for generating new islet cells from the postnatal pancreas, and for designing strategies to generate physiologically competent pancreatic islet cells ex vivo.