Engineered BMP2/BMP7 extracellular vesicles induce autocrine BMP release driving SMAD phosphorylation to promote bone...

Area of Science:

• Biotechnology
• Regenerative Medicine
• Orthopedics

Background:

• Impaired bone healing affects hundreds of thousands annually in the US.
• Current bone morphogenetic protein 2 (rhBMP2) therapies face challenges with bone quality and side effects.

Purpose of the Study:

• To investigate extracellular vesicles (EVs) engineered to produce BMP2 and BMP2/7 as an alternative bone regenerative therapy.
• To evaluate the osteogenic potential and mechanism of BMP2-EVs and BMP2/7-EVs.

Main Methods:

• Mesenchymal stem cells were engineered to produce BMP2-EVs and BMP2/7-EVs.
• Osteoblast differentiation was assessed via calcium deposition, alkaline phosphatase activity, and gene expression (osterix, RUNX2, osteocalcin, osteopontin).
• BMP receptor dependence was confirmed using a BMP I receptor inhibitor (DMH1).
• EV encapsulation and potency were verified against BMP antagonist Noggin.
• BMP2/7-EV efficacy was tested in a rat calvarial defect model using micro-computed tomography and histopathology.

Main Results:

• BMP2-EVs and BMP2/7-EVs significantly increased calcium deposition and alkaline phosphatase activity.
• Osteoblast differentiation markers (osterix, RUNX2, osteocalcin, osteopontin) were upregulated.
• BMP2/7-EVs induced SMAD phosphorylation, confirming BMP receptor signaling, which was inhibited by DMH1.
• Encapsulated BMPs within EVs retained potency after Noggin treatment.
• BMP2/7-EVs demonstrated enhanced bone formation in vivo, comparable to rhBMP2.

Conclusions:

• Engineered EVs, particularly BMP2/7-EVs, represent a viable alternative for stimulating bone formation.
• EVs offer a promising platform for delivering tailored, polyvalent regenerative biotherapies for bone defects.