Endochondral bone formation from hydrogel carriers loaded with BMP2-transduced cells

Area of Science:

• Biomaterials Engineering
• Tissue Engineering
• Regenerative Medicine

Background:

• Ex vivo gene therapy for bone formation requires spatial control of gene expression.
• Poly(ethylene glycol)-diacrylate (PEG-DA) hydrogels offer a non-degradable scaffold for cell encapsulation.

Purpose of the Study:

• To spatially localize gene expression for enhanced bone formation using BMP-2 secreting cells within hydrogels.
• To optimize BMP-2 secretion by varying polymer molecular weight and cell density.
• To evaluate the efficacy of encapsulated cells in promoting endochondral bone formation in vivo.

Main Methods:

• Adenovirus-transduced human diploid fetal lung fibroblasts (MRC-5) expressing BMP-2 were encapsulated in PEG-DA hydrogels.
• Hydrogels were prepared using PEG-DA polymers of varying molecular weights (6, 10, 20 kDa) and cell densities (1, 5, 10 million cells).
• Encapsulated cells and hydrogels were implanted intramuscularly into NOD/SCID mice, followed by Micro-CT and histological analysis.

Main Results:

• Hydrogels with 10 million transduced fibroblasts in PEG-DA 10 and 20 kDa showed highest BMP-2 secretion.
• Cell viability was 71% for MRC-5 and 58% for transduced fibroblasts post-encapsulation.
• Implanted hydrogels promoted significant mineralized tissue formation (39.5 mm3) and localized bone and cartilage, comparable to cell-injected controls.

Conclusions:

• PEG-DA hydrogels can successfully encapsulate BMP-2 secreting cells for localized gene delivery.
• Optimized cell density and hydrogel properties enhance BMP-2 secretion and bone formation.
• This system shows potential for improving ex vivo gene therapy strategies for bone regeneration.