Exosomal mRNAs for Angiogenic-Osteogenic Coupled Bone Repair

Area of Science:

• Regenerative Medicine
• Biomaterials Science
• Tissue Engineering
• Nanotechnology

Background:

• Current regenerative medicine strategies for tissue engineering, particularly bone regeneration, often depend on stem cells and supraphysiological doses of growth factors.
• These conventional methods present challenges including high costs and potential for severe side effects, necessitating the development of safer and more efficient alternatives.

Purpose of the Study:

• To develop and evaluate a novel therapeutic system for bone regeneration using engineered small extracellular vesicles (t-sEVs).
• To investigate the efficacy of t-sEVs loaded with vascular endothelial growth factor A (VEGF-A) and bone morphogenetic protein 2 (BMP-2) mRNA, delivered via an injectable hydrogel, for challenging femur defects in rats.

Main Methods:

• Therapeutic small extracellular vesicles (t-sEVs) were produced using a cellular nanoelectroporation system (TM-nanoEP) to deliver plasmid DNA to human adipose-derived mesenchymal stem cells (hAdMSCs).
• The t-sEVs were endogenously loaded with VEGF-A and BMP-2 mRNAs and encapsulated within a customized PEGylated poly (glycerol sebacate) acrylate (PEGS-A) hydrogel.
• The system was tested in rats with critical-size femur defects, evaluating bone regeneration, angiogenic-osteogenic potential, and biodistribution.

Main Results:

• The TM-nanoEP system facilitated efficient production of t-sEVs, which were enriched with upregulated microRNAs enhancing angiogenic-osteogenic regeneration.
• Localized delivery of t-sEVs within the PEGS-A hydrogel promoted highly efficient bone regeneration in critical-size defects.
• The hydrogel system ensured controlled release and retention of t-sEVs at the defect site, with minimal accumulation in other organs, indicating improved safety.

Conclusions:

• Engineered t-sEVs loaded with therapeutic mRNAs and delivered via a PEGS-A hydrogel represent a promising, safe, and effective strategy for bone regeneration.
• This innovative approach overcomes limitations of traditional stem cell therapies, offering a superior method for treating challenging bone defects.