Engineering new bone tissue in vitro on highly porous poly(alpha-hydroxyl acids)/hydroxyapatite composite scaffolds

Engineering new bone tissue with cells and a synthetic extracellular matrix (scaffolding) represents a new approach for the regeneration of mineralize d tissues compared with the transplantation of bone (autografts or allograf ts). In the present work, highly porous poly(L-lactic acid) (PLLA) and PLLA /hydroxyapatite (HAP) composite scaffolds were prepared with a thermally in duced phase separation technique. The scaffolds were seeded with osteoblast ic cells and cultured in vitro. In the pure PLLA scaffolds, the osteoblasts attached primarily on the outer surface of the polymer. In contrast, the o steoblasts penetrated deep into the PLLA/HAP scaffolds and were uniformly d istributed. The osteoblast survival percentage in the PLLA/HAP scaffolds wa s superior to that in the PLLA scaffolds. The osteoblasts proliferated in b oth types of the scaffolds, but the cell number was always higher in the PL LA/HAP composite scaffolds during 6 weeks of in vitro cultivation. Bone-spe cific markers (mRNAs encoding bone sialoprotein and osteocalcin) were expre ssed more abundantly in the FLLA/HAP composite scaffolds than in the PLLA s caffolds. The new tissue increased continuously in the PLLA/HAP composite s caffolds, whereas new tissue formed only near the surface of pure PLLA scaf folds. These results demonstrate that HAP imparts osteoconductivity and the highly porous PLLA/HAP composite scaffolds are superior to pure PLLA scaff olds for bone tissue engineering. (C) 2000 John Wiley & Sons, Inc.