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This study investigates the effect of porosity and pore shape on the biological and mechanical behavior of additively manufactured scaffolds for bone tissue engineering (BTE). Polylactic acid scaffolds with varying porosity levels (15-78%) and pore shapes, including regular (rectangular pores), gyroid, and diamond (triply periodic minimal surfaces) structures, are fabricated by fused filament fabrication. Murine-derived macrophages and human bone marrow-derived mesenchymal stromal cells (hBMSCs) are seeded onto the scaffolds. The compressive behavior and surface morphology of the scaffolds are characterized. The results show that scaffolds with 15%, 30%, and 45% porosity display the highest rate of macrophage and hBMSC growth. Gyroid and diamond scaffolds exhibit a higher rate of macrophage proliferation, while diamond scaffolds exhibit a higher rate of hBMSC proliferation. Additionally, gyroid and diamond scaffolds exhibit better compressive behavior compared to regular scaffolds. Of particular note, diamond scaffolds have the highest compressive modulus and strength. Surface morphology characterization indicates that the surface roughness of diamond and gyroid scaffolds is greater than that of regular scaffolds at the same porosity level, which is beneficial for cell attachment and proliferation. This study provides valuable insights into porosity and pore shape selection for additively manufactured scaffolds in BTE., (© 2023 Wiley-VCH GmbH.)

Impaction allograft as a scaffold for bone-forming cells is a tissue-engineering approach for filling bone defects that are commonly encountered during revision total joint replacement (THR). The purpose of this in vitro study is to assess the viability of mesenchymal stem cells (MSC) grown on allograft following impaction using forces similar to those measured during revision total hip replacements. Impaction forces of 0, 3, 6, and 9 kN were used representing normal and high impact. The results showed that the viability in the 3 and 6 kN groups was not significantly reduced compared with that of the 0 kN group, while the survival of the MSCs was significantly reduced after 9 kN impaction force. This study suggests that the addition of MSCs to the allograft scaffold will survive normal impaction force in revision THR.

Reconstructing segmental bone defects after resection of malignant bone tumors is a long-standing clinical problem. Treatment of bone tumors such as osteosarcoma involves chemotherapy. These chemotherapeutic agents are potent inhibitors of cell division and these drugs may affect regeneration of bone from osteoprogenitor cells. It may be possible to reconstruct segmental bone defects by a tissue-engineering approach. The aim of this study was to investigate the use of mesenchymal stem cells (MSCs) in a fibrin glue carrier to enhance bone regeneration after chemotherapy. Bone marrow was harvested from young adult male rats of the Wistar strain; stem cells were isolated and expanded. Bone regeneration in normal and chemotherapy-treated rats was investigated in 1.5-mm rat femoral defects created by osteotomizing the femur and stabilizing the femoral fragments by external fixation. The osteotomy gap was left either unfilled, filled with fibrin glue alone, or filled with glue containing stem cells. Bone formation within the gap was determined by radiography, dual-energy X-ray absorptiometry, and histology. It was shown that MSCs encapsulated within fibrin glue could remain viable for up to 96 h in tissue culture. Chemotherapy significantly reduced bone formation in unfilled defects and defects filled only with fibrin glue. When MSCs were used in conjunction with fibrin glue, even in non-chemotherapy-treated rats bone formation in the gap was significantly increased. Using stem cells, the effects of chemotherapy on bone formation could be alleviated by bone formation in the gap similar to that seen in non-chemotherapy-treated animals with MSCs. These studies demonstrated that a tissue-engineering approach in patients undergoing chemotherapy may be beneficial for treating segmental bone defects after tumor resection.