Concise review: adipose-derived stromal cells for skeletal regenerative medicine

Abstract

As the average age of the population grows, the incidence of osteoporosis and skeletal diseases continues to rise. Current treatment options for skeletal repair include immobilization, rigid fixation, alloplastic materials, and bone grafts, all which have significant limitations, especially in the elderly. Adipose-derived stromal cells (ASCs) represent a readily available abundant supply of mesenchymal stem cells, which demonstrate the ability to undergo osteogenesis in vitro and in vivo, making ASCs a promising source of skeletal progenitor cells. Current protocols allow for the harvest of over one million cells from only 15 ml of lipoaspirate. Despite the clinical use of ASCs to treat systemic inflammatory diseases, no large human clinical trials exist using ASCs for skeletal tissue engineering. The aim of this review is to define ASCs, to describe the isolation procedure of ASCs, to review the basic biology of their osteogenic differentiation, discuss cell types and scaffolds available for bone tissue engineering, and finally, to explore imaging of ASCs and their potential future role in human skeletal tissue engineering efforts.

Figure 1

In vivo model for skeletal tissue engineering.(Left, Top) Superior view of mouse left inguinal fat pad. Red arrow points to the fat pad which is dissected and subsequently digested for ASC harvest. (Left, Bottom) Human lipoaspirate in sterile collection canister settled into two layers. The upper yellow layer (Green Arrow) is the adipose tissue from which ASCs are harvested. Subsequently ASCs are isolated in vitro. 150,000 cells can then be seeded on an osteoconductive scaffold (Middle) and then the ASC laden scaffold can be placed inside a critical sized calvarial defect in syngeneic for mASCs or nude athymic mice for hASCs (Right). Mice can then be imaged using IVIS systems to detect cell viability and MicroCT to quantify osseous healing (Right).