An in vitro reconstruction of three-dimensional (3D) tissues without the use of scaffolds may be an alternative strategy for tissue engineering. We have developed a novel tissue engineering strategy, termed magnetic force-based tissue engineering (Mag-TE), in which magnetite cationic liposomes (MCLs) with a positive charge at the liposomal surface, and magnetic force were used to construct 3D tissue without scaffolds. In this study, human mesenchymal stem cells (MSCs) magnetically labeled with MCLs were seeded onto an ultra-low attachment culture surface, and a magnet (4000 G) was placed on the reverse side. The MSCs formed multilayered sheet-like structures after a 24-h culture period. MSCs in the sheets constructed by Mag-TE maintained an in vitro ability to differentiate into osteoblasts, adipocytes, or chondrocytes after a 21-day culture period using each induction medium. Using an electromagnet, MSC sheets constructed by Mag-TE were harvested and transplanted into the bone defect in the crania of nude rats. Histological observation revealed that new bone surrounded by osteoblast-like cells was formed in the defect area 14 days after transplantation with MSC sheets, whereas no bone formation was observed in control rats without the transplant. These results indicated that Mag-TE could be used for the transplantation of MSC sheets using magnetite nanoparticles and magnetic force, providing novel methodology for bone tissue engineering.
To engineer functional tissues, a large number of cells must be successfully seeded into scaffolds. We previously proposed a methodology for tissue engineering using magnetite nanoparticles and magnetic force, which we termed "Mag-TE." In the present study, we applied the Mag-TE technique to a cell seeding process and have termed the technique "Mag-seeding." The cell-seeding efficiency of NIH/3T3 fibroblasts (FBs) by Mag-seeding was investigated using six types of commercially available scaffolds (5 collagen sponges and 1 D,D-L,L polylactic acid sponge) having various pore sizes. FBs were magnetically labeled with our original magnetite cationic liposomes (MCLs), which have a positive surface charge, to improve adsorption onto the cell surface. FBs labeled with MCLs were seeded onto a scaffold, and a magnet (4 kG) was placed under the scaffold. Mag-seeding facilitated successful cell seeding into the deep internal space of the scaffolds. Cell-seeding efficiency increased significantly in all scaffolds when compared to those without magnetic force. Moreover, when a high-intensity magnet (10 kG) was used, cell-seeding efficiency was significantly enhanced. These results suggest that Mag-seeding is a promising approach for tissue engineering.
Objective-Therapeutic angiogenesis with cell transplantation represents a novel strategy for severe ischemic diseases.However, some patients have poor response to such conventional injection-based angiogenic cell therapy. Here, we investigated a therapeutic potential of mesenchymal stem cell (MSC) sheet created by a novel magnetite tissue engineering technology for reparative angiogenesis. Methods and Results-Human MSCs incubated with magnetic nanoparticle-containing liposomes were cultured, and a magnet was placed on the reverse side. Magnetized MSCs formed multilayered cell sheets according to magnetic force. Nude mice were subjected to unilateral hind limb ischemia and separated into 3 groups. For the control group, saline was injected into ischemic tissue. In the MSC-injected group, mice received magnetized MSCs by conventional needle injections without sheet formula as a control cell group. In the MSC-sheet group, MSC sheet was layered onto the ischemic tissues before skin closure. Blood flow recovery and the extent of angiogenesis were assessed by a laser Doppler blood flowmetry and histological capillary density, respectively. The MSC-sheet group had a greater angiogenesis in ischemic tissues compared to the control and MSC-injected groups. The angiogenic and tissuepreserving effects of MSC sheets were attributable to an increased expression of vascular endothelial growth factor and reduced apoptosis in ischemic tissues. In cultured MSCs, magnetic labeling itself inhibited apoptosis via a catalase-like antioxidative mechanism. Key Words: angiogenesis Ⅲ ischemia Ⅲ mesenchymal stem cells Ⅲ nanotechnology Ⅲ tissue engineering P eripheral artery disease (PAD) is characterized by a reduced blood supply due to narrowed or blocked arteries. Therapeutic angiogenesis is a novel strategy to treat no-option patients with severe PAD by promoting the formation of collateral vessels and angiogenesis. We previously reported therapeutic angiogenesis using autologous bone marrow mononuclear cell transplantation (TACT trial) into the ischemic tissues in patients with severe PAD. [1][2][3] Although the safety and efficiency of the TACT have been confirmed, a certain portion of patients showed poor response to the TACT procedure. 3 In general, patients with severe PAD and multiple coronary risk factors had reduced responses to any angiogenic cell therapies. 4 -7 The most common and widely used method of cell transplantation is direct injections of cell suspensions using injection needles. However, this simple method has several disadvantages such as rapid cell loss caused by a leakage of injected fluid, late cell loss due to unstable cell homing, and needle-mediated direct tissue damages. 8 -10 Thus, alternative cell source and/or cell application strategy have been explored. Conclusion-MSCRecent studies showed that mesenchymal stem cells (MSCs) have an ability to regenerate damaged tissues. Bone marrow-derived MSCs, for example, are multipotent cells that can differentiate into osteoblasts, chondrocytes, adipocytes, and...
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