Enhanced tissue production through redox control in stem cell-laden hydrogels.

Cellular bioenergetics and redox (reduction-oxidation) play an important role in cell proliferation and differentiation, key aspects of building new tissues. In the present study, we examined the metabolic characteristics of human adipose-derived stem cells (hASCs) during proliferation and differentiation in both monolayer and three-dimensional biomaterial scaffolds. In monolayer, hASCs exhibited higher glycolysis and lower ox-phos as compared to both adipogenic and osteogenic differentiated cells, and hASCs demonstrated the Warburg effect (aerobic glycolysis). However, reactive oxygen species (ROS) levels increased during adipogenic differentiation, but decreased during osteogenic differentiation. Similarly, a decrease in ROS levels along with a higher mitochondrial membrane potential and viability was observed in hASCs encapsulated in poly(ethylene glycol) (PEG) hydrogels containing an adhesion peptide (RGD), compared to PEG hydrogels with a scrambled control peptide (GRD), demonstrating that adhesion-dependent signaling can also regulate ROS production and bioenergetics. As a result, we hypothesized that we could modulate osteogenesis in PEG hydrogels containing the adhesion peptide (RGD) by further reducing ROS levels using a small therapeutic molecule, L-carnitine, a metabolite with purported antioxidant effects. We observed reduced ROS levels, no effect on mitochondrial membrane potential, and increased osteogenic differentiation and tissue production in cells in the presence of L-carnitine. These results suggest the potential to manipulate tissue production by modulating cellular metabolism.

Characterization of trkB immunoreactive cells in the intermediolateral cell column of the rat spinal cord.

The objective of the present study was to characterize the trkB receptor immunoreactive (-ir) cells in the intermediolateral cell column (IML) of the upper thoracic spinal cord. Small trkB-ir cells (area=56.1+/-4.4 microm(2)) observed in the IML showed characteristics of oligodendrocytes and were frequently observed in close apposition to choline acetyltransferase (ChAT)-ir cell bodies. Large trkB-ir cells (area=209.3+/-25.2 microm(2)) showed immunoreactivity for the neuronal marker NeuN, indicating their neuronal phenotype, as well as for ChAT, a marker for preganglionic neurons. TrkB and ChAT were co-localized in IML neurons primarily in cases that had received in vivo administration of nerve growth factor (NGF). These findings reveal two different cell types, oligodendrocytes and neurons, in the IML of the spinal cord that show trkB immunoreactivity, suggesting their regulation by brain derived neurotrophic factor (BDNF) and/or neurotrophin-4 (NT-4). In addition, there is evidence that NGF may play a role in the regulation of trkB-ir preganglionic neurons in the IML.