Sustained volume retention in vivo with adipocyte and lipoaspirate seeded silk scaffolds

Current approaches to soft tissue regeneration include the use of fat grafts, natural or synthetic biomaterials as filler materials. Fat grafts and natural biomaterials resorb too quickly to maintain tissue regeneration, while synthetic materials do not degrade or regenerate tissue. Here, we present a simple approach to volume stable filling of soft tissue defects. In this study, we combined lipoaspirate with a silk protein matrix in a subcutaneous rat model. Silk biomaterials can be tailored to fit a variety of needs, and here were processed silk biomaterials into a porous sponge format to allow for tissue ingrowth while remaining mechanically robust. Over an 18 month period, the lipoaspirate seeded silk protein matrix regenerated subcutaneous adipose tissue while maintaining the original implanted volume. A silk protein matrix alone was not sufficient to regenerate adipose tissue, but yielded a fibrous tissue, although implanted volume was maintained. This work presents a significant improvement to the standard approaches to filling soft tissue defects by matching biomaterial degradation and tissue regeneration profiles.