Background: Soft tissue augmentation with processed fat has been used clinically for several years. This material has been termed "autologous collagen" since it was presumed it was composed primarily of collagen and fibrous tissue from lipocyte cell walls.
Objective: To examine the histologic behavior of dermis implanted with processed fat.
Method: Volunteers were injected with processed fat intradermally in the post auricular area and these sites were biopsied at one week, one month, and three months.
Results: Early biopsies revealed no intact adiopocytes but a significant inflammatory infiltrate. Subsequently biopsies revealed replacement of the inflammatory reaction with cellular fibrosis and expansion of the dermis.
Conclusion: Intradermal injection of processed fat results in deposition of fibrous material and collagen due to the response of the recipient site. The material itself contains very little collagen.