| Summary: | Bone Morphogenetic Proteins (BMPs) belong to the Transforming Growth Factor Beta superfamily of growth factors. While BMP signaling has been shown to induce skeletogenic differentiation of mesenchymal stem cells and be involved in the formation of ectopic bone and ossification, BMPs also are involved in the differentiation of many other tissues including neurogenic tissues. Prior studies from our laboratory showed that BMP-2 induction of chondrogenic differentiation of the C3H10T1/2 murine mesenchymal stem cell line was associated with increased oxidative metabolism. This study was performed to test the hypothesis that BMP-2 promotes increased oxidative metabolism during the differentiation of other types of cells. Using the neurogenic cell line, SH-SY5Y, this study examined whether cellular differentiation induced by BMP-2 also was associated with increased oxidative phosphorylation in non-mesenchymal stem cells.
SH-SY5Y cells were grown in growth medium (DMEM/F12 with 10% FBS, 1% Penicillin/Streptomycin, L-glutamine, and non-essential amino acids). Cells were plated appropriately at differing seeding densities (Day 0), treated one time with ± 200ng/mL BMP-2 two days after plating and analyzed on Day 4. Oxidative metabolism was measured using a Seahorse XF Analyzer that measures oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). BMP-2 induction of neural cell differentiation was assayed by quantifying dendrite communication between neurons and decreased proliferative capacity as assessed by overall culture DNA contents. Mitochondrial density after BMP-2 treatment was examined using vital mitochondrial labeling.
Groups treated with BMP-2 contained significantly less DNA content than control groups (p=0.006). BMP-2 treated cells had on average more dendritic interactions with one or two and more processes than control groups (p=0.396; p=0.872), while there were a larger percentage of cells not treated with BMP-2 that had zero dendritic interactions (p=0.470). All parameters of oxidative metabolism were increased in cells treated with BMP-2. More specifically, basal respiration and ATP production were significantly increased in BMP-2 treated cells (p=0.031; p=0.010).
SH-SY5Y cells were significantly affected by BMP-2 treatment in both DNA content and oxidative phosphorylation. The diminished DNA content with BMP-2 treatment is consistent with the known decrease in cellular proliferation that is associated with neural cell differentiation. While there were small increases in dendritic interactions these were not significant and are inclusive for demonstrating BMP-2’s effect on neural differentiation. Upregulation of oxidative phosphorylation indicated after BMP-2 treatment was validated by the substantial increases in metabolic parameters associated with BMP-2 treatment. Through the utilization of the neural cell line, SH-SY5Y, this research suggests a more generalized functionality of BMP-2 in upregulation of oxidative metabolism as well as differentiation non-specific to bone and chondrocyte cell lineage.
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