This study aimed at characterizing the regulation of oxygen-sensing pathway in human mesenchymal stem cells (hMSCs). Cells were extracted from umbilical cord blood (UCB), adult bone marrow, and pediatric bone marrow. Expression of HIF-1a and PHDs in the three cells were determined under hypoxia and normoxia. The following activities were performed while conducting the study: cell culture and osteoinduction, characterization of hMSCs using flow cytometric method, hypoxic exposure and Western blot analysis, Quantitative Real -Time RT-PCR (Q-PCR), Glucose and Lactate Assays, Transmission Electron Microscopy (TEM), Determination of pH of the culture media, and Statistical Analyses.
The results showed that there was high expression of HIF-1a mRNA in all the hMSCs under normoxia. The expression was found to be higher in UCB and pediatric bone marrow than in adult bone marrow. Stabilization of HIF-1a observed in the study could have been due to increase in the transcription of HIF1A instead of protein degradation by PHDs. It was also found that the ratio of mRNAs of HIF-1a to the mRNAs of PHDs was higher than 6.4 in all the hMSCs. The study also revealed that hMSCs are capable of retaining their signalling of hypoxia in environments other than the hypoxic stem cell niche. It further suggests that there are low activities of PHDs in hypoxic niches. Another important finding was that hMSCs have high levels of HIF when cultured under normal oxygen concentration: 21%.
Certain features are shared between cancer cells and hMSCs. For instance, both cancer and hMSCs have high demand for proliferation and downregulation of differentiation (Vander, Cantley, & Thompson, 2009). This study identified another common feature between the two cells: induced glycolysis. For cancer cells, induced glycolysis helps in conversion of glucose into biomass. Induced glycolysis has been found to be advantageous to the proliferation of hMSCs. The study also found that the highest proliferation rates were exhibited by UCBMSCs. The study further identified three markers for hMSCs: induced glycolysis, suppressed oxidative phosphorylation, and high normoxic HIF.
References
Vander, H. M. G., Cantley, L. C., & Thompson, C. B. (May 21, 2009). Understanding the Warburg Effect: The Metabolic Requirements of Cell Proliferation. Science, 324, 5930, 1029-1033.
