Succinate Supplement Elicited “Pseudohypoxia” Condition to Promote Proliferation, Migration, and Osteogenesis of Periodontal Ligament Cells

Abstract

Most mesenchymal stem cells reside in a niche of low oxygen tension. Iron-chelating agents such as CoCl2 and deferoxamine have been utilized to mimic hypoxia and promote cell growth. The purpose of the present study was to explore whether a supplement of succinate, a natural metabolite of the tricarboxylic acid (TCA) cycle, can mimic hypoxia condition to promote human periodontal ligament cells (hPDLCs). Culturing hPDLCs in hypoxia condition promoted cell proliferation, migration, and osteogenic differentiation; moreover, hypoxia shifted cell metabolism from oxidative phosphorylation to glycolysis with accumulation of succinate in the cytosol and its release into culture supernatants. The succinate supplement enhanced hPDLC proliferation, migration, and osteogenesis with decreased succinate dehydrogenase (SDH) expression and activity, as well as increased hexokinase 2 (HK2) and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), suggesting metabolic reprogramming from oxidative phosphorylation to glycolysis in a normal oxygen condition. The succinate supplement in cell cultures promoted intracellular succinate accumulation while stabilizing hypoxia inducible factor-1α (HIF-1α), leading to a state of pseudohypoxia. Moreover, we demonstrate that hypoxia-induced proliferation was G-protein-coupled receptor 91- (GPR91-) dependent, while exogenous succinate-elicited proliferation involved the GPR91-dependent and GPR91-independent pathway. In conclusion, the succinate supplement altered cell metabolism in hPDLCs, induced a pseudohypoxia condition, and enhanced proliferation, migration, and osteogenesis of mesenchymal stem cells in vitro.

CircCDK8 regulates osteogenic differentiation and apoptosis of PDLSCs by inducing ER stress/autophagy during hypoxia

“…Hypoxia‐mimicking agents, such as CoCl 2 , have been tried in the expansion of stem cells 24 . A previous study reported that CoCl 2 mimics the hypoxic state and promotes the proliferation, migration, and osteogenesis of mesenchymal stem cells by intracellular succinate–induced HIF‐1α stabilization 25 . This study, as a novel finding, showed that hypoxia increased the nuclear accumulation of RUNX2 during the early stages of PDLSC exposure, and it subsequently promoted osteogenic differentiation through the stimulation of osteogenesis‐related genes.…”

Succinate Injection Rescues Vasculature and Improves Functional Recovery Following Acute Peripheral Ischemia in Rodents: A Multimodal Imaging Study

“…According to the literature, GPR91 seems to be implied in the activation of coping mechanisms upon adverse conditions, including stimulation of proliferation of different cell types, migration, and angiogenesis [ 1 , 7 , 12 , 19 , 20 , 21 , 22 ]. This has also been illustrated in ischemic conditions [ 23 , 24 , 25 ].…”

Ligament/Tendon Culture under Hypoxic Conditions: A Systematic Review

“…Fourteen studies performed a comparison with normoxic conditions (20% or 21% oxygen), three used 1% oxygen, 20,24,28 five used 2% oxygen, 8,22,25,26,29 two used 3% oxygen, 12,30 and four studies compared various hypoxia levels, including 1%, 2%, and 5% oxygen; 37 1% oxygen and a reoxygenation group (from 1% to 20% oxygen); 8,15 and 5% and 1% oxygen. 31 Overall, 15 studies evaluated the effects of certain oxygen concentrations: 3 used 5% oxygen, 13,14,32 1 used 3% oxygen, 34 5 used 2% oxygen, 7,19,21,27,35 2 used 1% oxygen, 20,36 3 used less than 1% oxygen, [16][17][18] and another used less than 0.1% oxygen. 33…”

“…28 Six studies reported an increase in osteogenic differentiation. 7,19,22,26,29,36 Hypoxic conditions also increased osteoclastogenesis, 17,27 improved the maintenance of pluripotent stem cells, 25 increased the expression of several mediators of apoptosis, and promoted tenocyte apoptosis. 20…”