The effect of mesenchymal stem cell sheets on structural allograft healing of critical sized femoral defects in mice

Abstract

Structural bone allografts are widely used in the clinic to treat critical sized bone defects, despite lacking the osteoinductive characteristics of live autografts. To address this, we generated revitalized structural allografts wrapped with mesenchymal stem/progenitor cell (MSC) sheets, which were produced by expanding primary syngenic bone marrow derived cells on temperature-responsive plates, as a tissue engineered periosteum. In vitro assays demonstrated maintenance of the MSC phenotype in the sheets, suggesting that short-term culturing of MSC sheets is not detrimental. To test their efficacy in vivo, allografts wrapped with MSC sheets were transplanted into 4-mm murine femoral defects and compared to allografts with direct seeding of MSCs and allografts without cells. Evaluations consisted of x-ray plain radiography, 3D microCT, histology, and biomechanical testing at 4- and 6-weeks post-surgery. Our findings demonstrate that MSC sheets induce prolonged cartilage formation at the graft-host junction and enhanced bone callus formation, as well as graft-host osteointegration. Moreover, a large periosteal callus was observed spanning the allografts with MSC sheets, which partially mimics live autograft healing. Finally, biomechanical testing showed a significant increase in the structural and functional properties of MSC sheet grafted femurs. Taken together, MSC sheets exhibit enhanced osteogenicity during critical sized bone defect repair, demonstrating the feasibility of this tissue engineering solution for massive allograft healing.

Uncovering the periosteum for skeletal regeneration: The stem cell that lies beneath

“…However, this did not completely mimic an autograft as slower resorption of the graft was observed [103]. More recently it has been reported that BM-MSC cell sheets can act as an engineered periosteum and promote bone callus formation during allograft healing [104], while PDC cell sheets may have applications in tendon-bone healing [105]. Evidently, the investigation of periosteum mimetics for skeletal regeneration and repair is gathering pace and further investigation is eagerly anticipated.…”

Bone Marrow Aspirate Concentrate in Animal Long Bone Healing

“…24 One study (3%) used a mouse model and investigated the femur. 48 One (3%) study used both rabbit and mice models in their study and investigated the radius. 22 …”

The rational use of animal models in the evaluation of novel bone regenerative therapies

“…Considering the wide diversity of conducted research, investigators should be extremely cautious to translate conclusion in-between models and species and pay special attention in designing the animal studies to draw valuable and reproducible results. Mouse: [185], [186] Rat: [187] (DM), [188] Rabbit: [189], [190], [191], [192] Dog: [193], [194] Sheep/Goat: [167], [170], [176], [195], [196], [197] human BM-derived MPCs…”