Adipose tissue presents an appealing alternative to bone marrow as a source of mesenchymal stem cells (MSC). However, in order to enhance cell proliferation and differentiation, 3-dimensional (3-D) culture may be required. A 3-D culture has benefits due to its more in vivo-like environment. Further, to form a functional tissue, a scaffold material is required to ensure proper shape and allow for efficient delivery of nutrients and growth factors. Alginate, a resorbable hydrogel, is a potential injectable scaffold for fat and bone tissue engineering due to its high biocompatibility, gelation with calcium and slow dissolution in a physiologic environment. In the present study, we examined the viability, gene expression and morphology of MSC, isolated from porcine adipose (ADSC) and bone marrow (BMSC), during osteogenic and adipogenic differentiation in a 3D alginate hydrogel environment for 0, 7 and 14 days (d). ADSC and BMSC were infused into alginate hydrogels, which polymerized upon the addition of Ca+2 ions. Both stem cell types were differentiated into osteoblasts using 0.1 μm dexamethasone, 10 mm beta glycerophosphate and 50 μm ascorbic acid, whereas adipocytes were differentiated using 10 μm insulin, 1 μm dexamethasone, and 0.5 mm IBMX. Osteogenic differentiation was confirmed using alkaline phosphatase, Von Kossa, and alizarin red S staining and adipogenic differentiation was confirmed using Oil Red O. Cell viability and proliferation was quantified using the MTT assay. Gene expression was measured using qPCR. The morphology of ADSC and BMSC differentiated toward osteogenic lineages changed with both cell types forming osteogenic nodules over time. The nodules formed by ADSC were larger in diameter than those formed by BMSC. Unlike the osteogenic cells that formed nodules, the ADSC and BMSC differentiated into adipogenic cells showed no significant changes in cell size or aggregation. Gene expression results indicated increased PPARG expression in BMSC with time whereas ADSC showed a peak of expression on day 7 and then decreased. ADSC showed increased (14-fold) PPRG expression when compared with BMSC. ADSC had 160-fold less expression of ALP than BMSC. BMSC showed a 16-fold higher expression level of BGLAP than ADSC. ADSC showed a 15.8% higher expression than BMSC for COL1a1. Both ADSC and BMSC showed similar trends SPARC expression, but BMSC had a 12-fold higher expression of SPP1 than ADSC. In summary, both types of mesenchymal stem cells successfully differentiated into both lineages and maintained viability in the hydrogel over time. In conclusion, alginate is a viable scaffold material for the differentiation of mesenchymal stem cells for tissue engineering applications. These results allow for future studies using the pig as an in vivo fat and bone tissue engineering model.
This research was supported by the Illinois Regenerative Medicine Institute.
Strategies for Bone Regeneration: From Graft to Tissue Engineering
