Adipose tissue engineering for
breast reconstruction can be performed for patients who have undergone breast surgery. We have previously confirmed adipogenesis in mice implanted with
type I collagen sponge with controlled release of
fibroblast growth factor 2 (
FGF2) and human adipose tissue-derived stem cells. However, in order to use this approach to treat
breast cancer patients, a large amount of adipose tissue is needed, and
FGF2 is not readily available. Thus, we aimed to regenerate large amounts of adipose tissue without
FGF2 for a long period. Under
general anesthesia, cages made of
polypropylene mesh were implanted into the rabbits' bilateral fat pads. Each cage was 10 mm in radius and 10 mm in height. Minced
type I collagen sponge was injected as a scaffold into the cage. Regenerated tissue in the cage was examined with ultrasonography, and the cages were harvested 3, 6, and 12 months after the implantation. Ultrasonography revealed a gradually increasing homogeneous high-echo area in the cage. Histology of the specimen was assessed with
hematoxylin and
eosin staining. The percentages of regenerated adipose tissue area were 76.2 ± 13.0 and 92.8 ± 6.6 % at 6 and 12 months after the implantation, respectively. Our results showed de novo adipogenesis 12 months after the implantation of only
type I collagen sponge inside the space. Ultrasonography is a noninvasive and useful method of assessing the growth of the tissue inside the cage. This simple method could be a promising clinical modality in
breast reconstruction.