Regulation of intracellular transition metal ion level with a pH-sensitive inorganic nanocluster to improve therapeutic angiogenesis by enriching conditioned medium retrieved from human adipose derived stem cells

Abstract

Cell therapy based on human adipose derived stem cells (hADSCs) is a known potential therapeutic approach to induce angiogenesis in ischemic diseases. However, the therapeutic efficacy of direct hADSC injection is limited by a low cell viability and poor cell engraftment after administration. To improve the outcomes of this kind of approach, various types of nanoparticles have been utilized to improve the therapeutic efficacy of hADSC transplantation. Despite their advantages, the adverse effects of nanoparticles, such as genetic damage and potential oncogenesis based on non-degradable property of nanoparticles prohibit the application of nanoparticles toward the clinical applications. Herein, we designed a transition metal based inorganic nanocluster able of pH-selective degradation (ps-TNC), with the aim of enhancing an hADSC based treatment of mouse hindlimb ischemia. Our ps-TNC was designed to undergo degradation at low pH conditions, thus releasing metal ions only after endocytosis, in the endosome. To eliminate the limitations of both conventional hADSC injection and non-degradable property of nanoparticles, we have collected conditioned medium (CM) from the ps-TNC treated hADSCs and administrated it to the ischemic lesions. We found that intracellular increment of transition metal ion upregulated the hypoxia-inducible factor 1α, which can induce vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) expressions. Based on the molecular mechanism, the secretion of VEGF and bFGF by ps-TNC treated hADSCs showed a significant improvement compared to that of untreated cells. Injecting the CM collected from ps-TNC treated hADSCs into the mouse hindlimb ischemia model (ps-TNC-CM group) showed significantly improved angiogenesis in the lesions, with improved limb salvage and decreased muscle degeneration compared to the group injected with CM collected from normal hADSCs (CM group). This study suggests a novel strategy, combining a known angiogenesis molecular mechanism with both an improvement on conventional stem cell therapy and the circumvention of some limitations still present in modern approaches based on nanoparticles.

Engineered Nano–Bio Interfaces for Stem Cell Therapy

“…The delivery of metal (Fe) ions to enhance hMSC-based wound healing has been achieved by engineered bioreducible ETIN. Fe ions could be released within the cells in response to the low-pH conditions in endosomes. ,, To strongly confirm those mechanisms, Kim and co-workers demonstrated that ps-TNCs can improve the angiogenic efficacy of hADSCs by controlling the intracellular transition ion level, which has also been applied to ischemic lesions the CM derived from psTNC-treated hADSCs as shown in Figure a–c …”

“…125,126,128 To strongly confirm those mechanisms, Kim and co-workers demonstrated that ps-TNCs can improve the angiogenic efficacy of hADSCs by controlling the intracellular transition ion level, which has also been applied to ischemic lesions the CM derived from psTNC-treated hADSCs as shown in Figure 8a−c. 141 Despite the mechanisms mentioned above, however, the low viability of hMSCs following transplantation has been identified as the problem. Park et al addressed this challenge by developing Fe ion-releasing gold NPs for advanced tumortargeted photothermal therapy using hMSCs where Fe ions are released in hMSCs under low pH conditions.…”

Iron Oxide Nanoparticles in Mesenchymal Stem Cell Detection and Therapy

“…2 ) [ 58 ]. Iron-ion-induced ROS also upregulates hypoxia inducible factor-1α (HIF-1α) expression in MSCs, which in turn, can elevate MSC secretion of paracrine factors like VEGF (supports angiogenesis during wound repair) and basic fibroblast growth factor (bFGF) (supports angiogenesis) [ 59 ]. Essentially, HIF-1α acts as a transcription factor, binds to VEGF promoter and induces VEGF expression [ 56 , 60 , 61 ].…”

Tenascin-C: A Key Regulator in Angiogenesis during Wound Healing

“…TNC itself is continuously up-regulated during the wound repair process. A large number of experiments have established that TNC exerts pro-angiogenic effects [ 9 , 10 , 11 , 12 ]. However, angiogenesis did not increase significantly during the inflammatory phase of tissue injury [ 13 , 14 ], although TNC levels gradually increased.…”