No abstract

Implantation of occlusion devices is an effective approach for the treatment of congenital heart diseases in the clinic. However, most commercial clinical occlusion devices are currently made of nondegradable metals, which may lead to complications such as perforation, allergies, and erosion. In this work, 4D-printed novel, biodegradable, remotely controllable, and personalized shape memory occlusion devices are demonstrated and atrial septal defect occluders are exemplified. By incorporating Fe 3 O 4 magnetic particles into the shape memory poly(lactic acid) matrix, the deployment of the occluders can be controlled remotely after implantation. The excellent cytocompatibility and histocompatibility are conducive to cell adhesion and ingrowth of granulation tissues into the occluders, thus facilitating rapid endothelialization. In addition, personalized shape memory occluders ensure an ideal fit and provide sufficient support for defects. Therefore, 4D-printed shape memory occluders can be used as a potential substitute for metal occlusion devices.

No abstract

This review summarizes the advances and challenges of shape memory polymer-based flexible electronic devices.

Umbilical cord mesenchymal stem cells (UC-MSCs) have been suggested as a candidate for various clinical applications, however, major limitations include the lack of organ-specific accumulation and low survival rates of transplanted cells. In the present study, it was hypothesized that the paracrine effects of UC-MSCs may enhance stem cell-based tissue repair and regeneration by promoting the specific homing of stem/progenitor cells and the overall ability to drive them to the damaged area. UC-MSCs-derived conditioned medium (UC-CM) was analyzed using liquid chip and ELISA techniques. In vitro tube formation assays of human umbilical vein endothelial cells (HUVECs) and UC-MSCs were then performed to assess the angiogenic properties of UC-CM. Subsequently, UC-MSCs, HUVECs and fibroblasts were labeled with PKH26 for an in vivo cell migration assay. The expression levels of C-X-C chemokine receptor 4 (CXCR4), C-C chemokine receptor 2 (CCR2) and c-met were determined in the UC-MSCs, HUVECs and fibroblasts using reverse transcription-quantitative polymerase chain reaction and flow cytometry. UC-CM was incubated with or without antibodies, and the contribution of stromal cell-derived factor 1 (SDF-1), monocyte chemotactic protein 1 (MCP-1) and hepatocyte growth factor (HGF) on the migration of cells was investigated in vitro. The results demonstrated that UC-MSCs secreted different cytokines and chemokines, including increased quantities of SDF-1, MCP-1 and HGF, in addition to the angiogenic factors, vascular cell adhesion protein-1, interleukin-8, insulin-like growth factor-1 and vascular endothelial growth factor. The total lengths of the tubes were significantly increased in the UC-MSCs and HUVECs incubated in UC-CM compared with those incubated in Dulbecco’s modified Eagle’s medium. In vivo cell migration assays demonstrated that UC-CM was a chemotactic stimulus for the UC-MSCs and HUVECs. In vitro Matrigel migration and scratch healing assays demonstrated that UC-CM increased the migration of CXCR4-postive or/and CCR2-positive cells in a dose-dependent manner. In addition, different molecules were screened under antibody-based blocking migration conditions. The data revealed that the SDF-1/CXCR4 and MCP-1/CCR2 axes were involved in the chemoattractive activity of UC-CM and suggested that the effective paracrine factor of UC-CM is a large complex rather than a single factor. The results of the present study supported the hypothesis that UC-MSCs release soluble factors, which may extend the therapeutic applicability of stem cells.