Bone morphogenetic protein-induced cell differentiation involves Atg7 and Wnt16 sequentially in human stem...

Area of Science:

• Stem Cell Biology
• Osteogenesis Research
• Molecular Signaling Pathways

Background:

• Osteoblastic differentiation is critical for bone formation and repair.
• Human skeletal muscle stem cells (hSMSCs) offer a potential source for osteoprogenitors.
• Bone morphogenetic protein-2 (BMP-2) is a key regulator of osteogenesis.

Purpose of the Study:

• To establish a differentiation method for α7 integrin-positive hSMSCs (α7(+)hSMSCs) into osteoblast-like cells using BMP-2.
• To elucidate the early signaling cascade, specifically autophagy-related gene (Atg) and wingless/int1 (Wnt) signaling, in BMP-2-mediated osteoblastic differentiation.

Main Methods:

• BMP-2 treatment of α7(+)hSMSCs.
• Quantitative analysis of mRNA and protein expression for autophagy and Wnt signaling components.
• Gene silencing using siRNAs against Atg7 and Wnt16.
• Pharmacological manipulation of autophagy using chloroquine and rapamycin.
• Assessment of osteoblastic marker gene expression (BGLAP, SPP1, SP7).

Main Results:

• BMP-2 upregulated Atg7, Wnt16, and Lrp5/Fzd2, alongside autophagosome formation and autophagy flux.
• Silencing Atg7 or Wnt16 significantly suppressed BMP-2-induced osteoblastic differentiation.
• Autophagy inhibition (chloroquine) decreased osteoblastic phenotype, while enhancement (rapamycin) increased it.

Conclusions:

• A novel sequential cascade: BMP-2 → Atg7 → Wnt16 → Lrp5/Fzd2 → MMP-13 → osteoblastic differentiation was identified.
• Atg7, autophagy, and Wnt16 signaling play a unique and essential role in early BMP-2-induced osteoblastic differentiation of α7(+)hSMSCs.
• This pathway provides a new understanding of stem cell-based osteogenesis.