Clinical and experimental approaches to knee cartilage lesion repair and mesenchymal stem cell chondrocyte differentiation.

Cartilage has poor regeneration capacity due to the scarcity of endogenous stem cells, its low metabolic activity and the avascular environment. Repair strategies vary widely, including microfracture, autologous or allogenic tissue implantation, and in vitro engineered tissues of autologous origin. However, unlike the advances that have been made over more than two decades with more complex organs, including vascular, cardiac or bone tissues, similar advances in tissue engineering for cartilage repair are lacking.

Glucose transporter 1 and monocarboxylate transporters 1, 2, and 4 localization within the glial cells of shark blood-brain-barriers.

Although previous studies showed that glucose is used to support the metabolic activity of the cartilaginous fish brain, the distribution and expression levels of glucose transporter (GLUT) isoforms remained undetermined. Optic/ultrastructural immunohistochemistry approaches were used to determine the expression of GLUT1 in the glial blood-brain barrier (gBBB). GLUT1 was observed solely in glial cells; it was primarily located in end-feet processes of the gBBB.

Ependymal cell differentiation and GLUT1 expression is a synchronous process in the ventricular wall.

Ependymal cells appear to be totally differentiated during the first 3 weeks in the mouse brain. Early during postnatal development ependymal cells differentiate and undergo metabolic activation, which is accompanied by increased glucose uptake. We propose that ependymal cells induce an overexpression of the glucose transporter, GLUT1, during the first 2 weeks after delivery in order to maintain the early metabolic activation.

Hypothalamic ependymal-glial cells express the glucose transporter GLUT2, a protein involved in glucose sensing.

The GLUT2 glucose transporter and the K-ATP-sensitive potassium channels have been implicated as an integral part of the glucose-sensing mechanism in the pancreatic islet beta cells. The expression of GLUT2 and K-ATP channels in the hypothalamic region suggest that they are also involved in a sensing mechanism in this area. The hypothalamic glial cells, known as tanycytes alpha and beta, are specialized ependymal cells that bridge the cerebrospinal fluid and the portal blood of the median eminence.