Mesenchymal stem cells promote endothelial progenitor cell migration, vascularization, and bone repair in tissue‐engineered constructs via activating CXCR2‐Src‐PKL/Vav2‐Rac1

Abstract

Tissue-engineered constructs (TECs) hold great promise for treating large bone defects. Incorporated mesenchymal stem cells (MSCs) can facilitate the vascularization of TECs. Nevertheless, the underlying mechanism remains ambiguous. Here we analyzed the roles of C-X-C chemokine receptor 2 (CXCR2) and its downstream signal pathways in MSC-induced endothelial progenitor cell (EPC) migration. Transwell assays and immunofluorescence staining were performed for cell migration analysis in vitro and in vivo, respectively. A series of signal inhibitors and short hairpin RNA was used for screening essential signaling molecules. We found that blockade of CXCR2 abolished the migration of EPCs toward MSCs as well as subsequent vascularization and bone repair in TECs. Moreover, screening results suggested that steroid receptor coactivator (Src) acted as a predominant downstream effector of CXCR2. Further molecular biologic and histomorphological experiments revealed that the action of Src required the phosphorylation of ras-related C3 botulinum toxin substrate 1 (Rac1), which was pivotal for the development of lamellipodia and filopodia. The phosphorylation and colocalization of paxillin kinase linker (PKL) and vav guanine nucleotide exchange factor 2 (Vav2) were essential for the activation of Rac1. Therefore, we demonstrated that MSCs promoted EPC migration via activating CXCR2 and its downstream Src-PKL/Vav2-Rac1 signaling pathway. These findings unveiled the molecular mechanism in the vascularization of TECs and were expected to provide novel targets for efficacy improvement.-Li, Z., Yang, A., Yin, X., Dong, S., Luo, F., Dou, C., Lan, X., Xie, Z., Hou, T., Xu, J., Xing, J. Mesenchymal stem cells promote endothelial progenitor cell migration, vascularization, and bone repair in tissue-engineered constructs via activating CXCR2-Src-PKL/Vav2-Rac1.

Bone Marrow-Derived CD44+Cells Migrate to Tissue-Engineered Constructs via SDF-1/CXCR4-JNK Pathway and Aid Bone Repair

“…As with bone defect modeling, we previously established a reliable and reproducible load-bearing, critical-size femoral defect model in mice with the help of a self-designed screw-plate fixation system. This model was successfully applied in basic research in the field of bone tissue engineering [16, 17]. In summary, the main research purpose, that is, to identify the origin of host cells involved in TEC-mediated bone repair, cannot be achieved in the absence of either model of GFP-BMT, parabiosis, or LSBD.…”

“…Decalcified bone matrix (DBM) scaffolds were chosen as cell carriers due to their excellent capacities of supporting the adhesion, growth, and proliferation of MSCs [16]. They were prepared using porcine trabecular bones from Yunnan miniature pigs according to a previously described method [17]. TECs were fabricated by dropwise instilling an aliquot (20 μ l, 1 × 10 6 cells/ml) of a single mBMSC suspension onto the two opposite surfaces of DBM.…”

CXCL8 derived from mesenchymal stromal cells supports survival and proliferation of acute myeloid leukemia cells through the PI3K/AKT pathway

“…In this study, we found that paracrine CXCL8 derived from BM‐MSCs also promoted AML cell proliferation and survival. CXCL8 exerts its effects on the target cells after binding to the CXCR2 receptor expressed on those cells; therefore, blocking the CXCL8–CXCR2 axis is of therapeutic potential in various solid tumors (20,30,39,43). Consistent with this, Schinke et al .…”

Arf GAPs as Regulators of the Actin Cytoskeleton—An Update

“…Active Rac1 and Cdc42 can then stimulate actin polymerization by activating actin nucleation-promoting factors like WAVE or N-WASP or activating PAK to activate ERK and cortactin. GIT2 was also reported to promote endothelial cell migration in response to CXCR2 by function with another Rac GEF, Vav2 [101]. Mechanistically, GIT2 appeared to stimulate Vav2, leading to Rac activation and increased migration induced by CXCR2.…”