Soft-tissue augmentation with injectable alginate and syngeneic fibroblasts

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Tissue Engineering

Background:

• Soft-tissue augmentation currently involves independent injections of polymers and cell populations.
• Tissue engineering offers a combined approach using polymer scaffolds and cells.

Purpose of the Study:

• To develop and utilize an inbred rat model for comparing different hydrogel materials for soft-tissue augmentation.
• To evaluate the histologic behavior and shape/volume maintenance of calcium alginate hydrogels with and without fibroblasts.

Main Methods:

• Developed a subcutaneous injection model in Lewis rats using vacuum for consistent material comparison.
• Tested three calcium alginate forms: post-gel, pre-gel, and alginate-RGD, with and without syngeneic fibroblasts over 8 weeks.
• Assessed construct volume, geometry, histology, and material compression strength.

Main Results:

• Alginate post-gel demonstrated optimal geometry maintenance (58% volume at 8 weeks), enhanced to 88% with fibroblasts.
• Alginate pre-gel showed poorest volume retention (31% at 8 weeks), decreasing to 19% with fibroblasts.
• RGD-modified alginate showed intermediate results, with volume increasing from 25% to 41% with fibroblasts; histological analysis revealed fibrovascular ingrowth in pre-gel and RGD groups.

Conclusions:

• Calcium alginate gelled subcutaneously post-injection is a suitable agent for soft-tissue augmentation.
• Inclusion of syngeneic fibroblasts enhances volume maintenance, likely through increased gel stiffness rather than new tissue formation.
• The developed animal model and material testing provide a robust platform for evaluating soft-tissue augmentation materials.