Genetic markers of osteogenesis and angiogenesis are altered in processed lipoaspirate cells when cultured on three-dimensional scaffolds.

Abstract

Liposuction-derived stem cells (processed lipoaspirate) have recently been shown to be capable of differentiating into bone. Most studies on osteoblastic growth and differentiation have been conducted in a conventional two-dimensional culture system; however, in native bone, osteoblasts are situated in a three-dimensional configuration. There have been limited studies of processed lipoaspirate behavior in three-dimensional systems. The authors studied the influence a three-dimensional scaffold has on the expression of genes related to osteogenesis and angiogenesis in processed lipoaspirate cells. One million processed lipoaspirate cells were seeded onto two-dimensional poly(l-lactide-co-glycolide) films or in three-dimensional poly(l-lactide-co-glycolide) scaffolds and incubated in osteogenic medium up to 21 days. RNA was extracted and analyzed with quantitative real-time polymerase chain reaction. When an inert three-dimensional poly(l-lactide-co-glycolide) scaffold was introduced, the pattern and sequence of gene expression changed significantly. Processed lipoaspirate cells cultured onto three-dimensional scaffolds had increased expression of interleukin-8 and vascular endothelial growth factor compared with two-dimensional controls at early time points. Osteogenesis markers-alkaline phosphatase, collagen type I, osteocalcin, osteonectin, and osteopontin-were significantly up-regulated in three-dimensional cultures relative to two-dimensional controls after 24 hours and persisted throughout the 21 days. In human processed lipoaspirate cells, the introduction of a three-dimensional scaffold significantly enhances gene markers of angiogenesis and osteogenesis. On three-dimensional scaffolds, processed lipoaspirate cells first up-regulate genes involved with vascular ingrowth and then those involved in bone formation. We believe these differences will significantly impact the design of a bone graft substitute for clinical application.