Trimodal rescue of hind limb ischemia with growth factors, cells, and nanocarriers: fundamentals to clinical trials

An Innovative Delivery System of Oxygen-Releasing Nanospheres and Self-Healing Hydrogels Enhances the Therapeutic Effectiveness of Bone Marrow Mesenchymal Stem Cells for Chronic Limb-Threatening Ischemia

Purpose

Bone marrow mesenchymal stem cells (BMSCs) have emerged as promising candidate for postoperative therapeutics in chronic limb-threatening ischemia (CLTI). Nevertheless, their effectiveness is limited by their low survival rate and impaired functionality in the ischemic microenvironment. To overcome these challenges, we have devised an innovative delivery approach to support the utilization of BMSCs in CLTI therapy.

Methods

We synthesized oxygen-releasing nanospheres and self-healing hydrogels. The in vivo functionality of the hydrogel-nanosphere delivery system was evaluated via a multimodality animal live imaging system. A unilateral lower limb ischemia model was established in mice, and a delivery system loaded with BMSCs was administered. The experimental groups included normal mice, ischemic mice, ischemic mice treated with BMSCs in PBS, and ischemic mice treated with BMSCs in the delivery system. Blood perfusion was quantitatively measured via a laser doppler flowmeter (LDF). Immunofluorescence, Masson's trichrome staining, immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) were also used.

Results

For cell viability analysis 80 μg.mL-1 was considered the optimal concentration for cell survival. In vivo, 18 days after injection, the cell membrane fluorescence signal in the delivery system was significantly greater (5.65510±8.2268) p/s/cm²/sr than that in the other groups (p=0.043). Ischemic mice treated with BMSCs in the delivery system presented an improved limb salvage rate (0.926±0.12)% compared with that of ischemic mice treated with BMSCs in PBS (0.841±0.029)% at the 5th week after ischemia establishment (p=0.0033).

Conclusion

Our findings suggest that the survival time of BMSCs is prolonged in this innovative delivery system. The combination of nanospheres and hydrogels effectively restored vascular blood perfusion while exerting minimal toxicity on BMSCs. This novel approach combining oxygen-releasing nanospheres and self-healing hydrogels as a delivery system represents an advancement in enhancing the functionality of BMSCs to treat CLTI.

Adipose-derived stem cell/FGF19-loaded microfluidic hydrogel microspheres for synergistic restoration of critical ischemic limb

The efficacy of stem cell therapy is substantially compromised due to low cell survival rate and poor local retention post-delivery. These issues drastically limit the application of stem cells for ischemic limb therapy, which requires effective blood perfusion and skeletal muscle regeneration. Herein, based on microfluidic technology, an integrated stem cell and cytokine co-delivery system designed for functional ischemic limb salvage was constructed by first incorporating the myogenic cytokine, fibroblast growth factor 19 (FGF19), into microspheres composed of methacrylate gelatin (GelMA). Then adipose-derived stem cells (ADSCs) were highly absorbed into the porous structure of the microspheres, overcoming the insufficient loading efficiency and activities by conventional encapsulation strategy. The fabricated ADSCs/FGF19@μsphere system demonstrated a uniform size of about 180 μm and a highly porous structure with pore sizes between 20 and 40 μm. The resultant system allowed high doses of ADSCs to be precisely engrafted in the lesion and to survive, and achieved sustained FGF19 release in the ischemic region to facilitate myoblast recruitment and differentiation and myofibrils growth. Furthermore, the combination of ADSCs and FGF19 exhibited a positive synergistic effect which substantially improved the therapeutic benefit of angiogenesis and myogenesis, both in vitro and in vivo. In summary, a stem cell and cytokine co-delivery system with the properties of easy preparation and minimal invasiveness was designed to ensure highly efficient cell delivery, sustained cytokine release, and ultimately realizes effective treatment of ischemic limb regeneration.

Cyclic Nigerosyl-Nigerose as Oxygen Nanocarrier to Protect Cellular Models from Hypoxia/Reoxygenation Injury: Implications from an In Vitro Model

Heart failure (HF) prevalence is increasing among the aging population, and the mortality rate remains unacceptably high despite improvements in therapy. Myocardial ischemia (MI) and, consequently, ischemia/reperfusion injury (IRI), are frequently the basis of HF development. Therefore, cardioprotective strategies to limit IRI are mandatory. Nanocarriers have been proposed as alternative therapy for cardiovascular disease. Controlled reoxygenation may be a promising strategy. Novel nanocarriers, such as cyclic nigerosyl-nigerose (CNN), can be innovative tools for oxygen delivery in a controlled manner. In this study we analyzed new CNN-based formulations as oxygen nanocarriers (O₂-CNN), and compared them with nitrogen CNN (N₂-CNN). These different CNN-based formulations were tested using two cellular models, namely, cardiomyoblasts (H9c2), and endothelial (HMEC) cell lines, at different concentrations. The effects on the growth curve during normoxia (21% O₂, 5% CO₂ and 74% N₂) and their protective effects during hypoxia (1% O₂, 5% CO₂ and 94% N₂) and reoxygenation (21% O₂, 5% CO₂ and 74% N₂) were studied. Neither O₂-CNN nor N₂-CNN has any effect on the growth curve during normoxia. However, O₂-CNN applied before hypoxia induces a 15–30% reduction in cell mortality after hypoxia/re-oxygenation when compared to N₂-CNN. O₂-CNN showed a marked efficacy in controlled oxygenation, which suggests an interesting potential for the future medical application of soluble nanocarrier systems for MI treatment.