Hypoxic Preconditioning of Human Mesenchymal Stem Cells Overcomes Hypoxia-Induced Inhibition of Osteogenic Differentiation

Abstract

Osteogenic differentiation of human mesenchymal stem cells (hMSCs) into osteoblasts is a prerequisite for subsequent bone formation. Numerous studies have explored osteogenic differentiation under standard tissue culture conditions, which usually employ 21% of oxygen. However, bone precursor cells such as hMSCs reside in stem cell niches of low-oxygen atmospheres. Furthermore, they are subjected to low oxygen concentrations when cultured on three-dimensional scaffolds in vitro, and even more so after transplantation when vascularization has yet to be established. Similarly, hMSCs are exposed to low oxygen in the fracture microenvironment following bony injury. Recent studies revealed that hypoxic preconditioning improves cellular engraftment and survival in low-oxygen atmospheres. In our study we investigated the osteogenic differentiation potential of hMSCs under 2% O(2) (hypoxia) in comparison to a standard tissue culture oxygen atmosphere of 21% (normoxia). We assessed the osteogenic differentiation of hMSCs following hypoxic preconditioning to address whether this pretreatment is beneficial for subsequent differentiation processes as well. To validate our findings we carefully characterized the extent of hypoxia exerted and its effect on cell survival and proliferation. We found that hMSCs proliferate better if cultured under 2% of oxygen. We confirmed that osteogenic differentiation of hMSCs is indeed inhibited if osteogenic induction is carried out under constant hypoxia. Finally, we showed for the first time that hypoxic preconditioning of hMSCs prior to osteogenic induction restores osteogenic differentiation of hMSCs under hypoxic conditions. Collectively, our results indicate that maintaining constant levels of oxygen improves the osteogenic potential of hMSCs and suggest that low oxygen concentrations may preserve the stemness of hMSCs. In addition, our data support the hypothesis that if low-oxygen atmospheres are expected at the site of implantation, hypoxic pretreatment may be beneficial for the cells' subsequent in vivo performance.

Into the eyes of bone marrow-derived mesenchymal stem cells therapy for myocardial infarction and other diseases

“…Actually, when it comes to the role of autophagy on cell, it is still a controversial issue according to the present study (11,(38)(39)(40)(41). There is evidence demonstrated that autophagy can either protect cells or contribute to cell death depend on the intensity of stimulus.…”

“…However, poor viability of donor stem cells after transplantation limits their therapeutic efficiency, whereas, the underlying mechanism is still poorly understood (36). Autophagy, a highly conserved process of cellular degradation, is required for maintaining homeostasis and normal function including MI (37).Actually, when it comes to the role of autophagy on cell, it is still a controversial issue according to the present study (11,(38)(39)(40)(41). There is evidence demonstrated that autophagy can either protect cells or contribute to cell death depend on the intensity of stimulus.…”

Into the Eyes of Bone Marrow-Derived Mesenchymal Stem Cells Therapy for Myocardial Infarction and Other Diseases

“…Autophagy, a highly-conserved process of cellular degradation, is required for maintaining homeostasis and normal function including MI [42] (Figure 2). Actually, when it comes to the role of autophagy on cell, it is still a controversial issue according to the present study [16, [43][44][45][46]. There is evidence demonstrated that autophagy can either protect cells or contribute to cell death depend on the intensity of stimulus.…”

Targeting the hypoxic response in bone tissue engineering: A balance between supply and consumption to improve bone regeneration

“…Current literature points towards positive effects of hypoxia signalling on undifferentiated MSC during in vitro culture Volkmer et al, 2010), where it promotes the preservation of the proliferative and multipotency capacities of MSC, but the effect of hypoxia signalling on differentiating and mature osteoblasts has not been as conclusively determined. In other tissue models of regenerative MSC-based therapies, hypoxia signalling enhances the in vivo outcome Rey et al, 2011) by improving cell survival through adapting energy, pH and redox balance.…”