Hydrogen Sulfide Maintains Mesenchymal Stem Cell Function and Bone Homeostasis via Regulation of Ca2+ Channel Sulfhydration

Abstract

SUMMARY Gaseous signaling molecules such as hydrogen sulfide (H2S) are produced endogenously and mediate effects through diverse mechanisms. H2S is one such gasotrasmitter which regulates multiple signaling pathways in mammalian cells, and abnormal H2S metabolism has been linked to defects in bone homeostasis. Here, we demonstrate that bone marrow mesenchymal stem cells (BMMSCs) produce H2S to regulate their self-renewal and osteogenic differentiation, and H2S deficiency results in defects in BMMSC differentiation. H2S deficiency causes aberrant intracellular Ca2+ influx, due to reduced sulfhydration of cysteine residues on multiple Ca2+ TRP channels. This decreased Ca2+ flux downregulates PKC/Erk-mediated Wnt/β-catenin signaling which controls osteogenic differentiation of BMMSCs. Consistently, H2S-deficient mice display an osteoporotic phenotype, which can be rescued by small molecules which release H2S. These results demonstrate H2S regulates BMMSCs, and restoring H2S levels via non-toxic donors may provide treatments for diseases such as osteoporosis which can arise from H2S deficiencies.

Cystathionine γ-Lyase–Hydrogen Sulfide Induces Runt-Related Transcription Factor 2 Sulfhydration, Thereby Increasing Osteoblast Activity to Promote Bone Fracture Healing

“…H2S is a metabolic production of homocysteine by transsulfuration dependent on CBS, CSE, or MPST combined with cysteine aminotransferase (37). Recent studies highlight that H2S plays an essential role in osteoclast differentiation (11,23) and bone marrow MSC osteogenesis (26). In this study, we identified that osteoblasts predominantly expressed the CSE-H2S system, which sulfhydrated RUNX2 at C122 and C132 sites to increase RUNX2 activity, thereby enhancing osteoblast biologic function to promote bone fracture healing.…”

“…The sulfhydration modification depends on H2S generation (27). CSE or CBS knockdown had similar effects on H2S generation and osteogenesis marker expression in MSCs (26). MSCs differentiated into osteoprogenitors and then preosteoblasts (6).…”

“…Both CBS and CSE are expressed in MSCs, and CBS is necessary for MSC osteogenesis (26). However, the CSE role in MSCs is not fully investigated.…”

“…Finally, H2S promotes bone MSC mineralization by Wnt signals (12) and reduces MC3T3-E1 preosteoblast cell injury induced by H2O2 (39). CBS deficiency lowers MSC osteogenesis ability, which can be rescued by an H2S donor (26). However, the key enzyme generating H2S in osteoblasts and the role of the enzyme/H2S system in their maturation and differentiation activity and the molecular mechanism are unclear.…”

“…Overexpressed CSE increased endogenous H2S production, and then increased Wnt expression (12), sulfhydrated TRPV6, and promoted MSC differentiation into preosteoblasts (26); sulfhydrated RUNX2 at the runt domain thereby increased its transcription, consequently enhancing the expression of RUNX2 target genes OCN (8), collagen aI, BSP, and OPN (9) to promote osteoblast extracellular matrix secretion and mineralization. H2S also increased BMP2 expression, an important molecule to induce osteoblast differentiation and biological function (1), but the molecular mechanism needs to be investigated.…”