The success of skeletal muscle reconstruction depends on finding the most effective, clinically suitable strategy to engineer myogenic cells and biocompatible scaffolds. Satellite cells (SCs), freshly isolated or transplanted within their niche, are presently considered the best source for muscle regeneration. Here, we designed and developed the delivery of either SCs or muscle progenitor cells (MPCs) via an in situ photo-cross-linkable hyaluronan-based hydrogel, hyaluronic acid-photoinitiator (HA-PI) complex. Partially ablated tibialis anterior (TA) of C57BL/6J mice engrafted with freshly isolated satellite cells embedded in hydrogel showed a major improvement in muscle structure and number of new myofibers, compared to muscles receiving hydrogel + MPCs or hydrogel alone. Notably, SCs embedded in HA-PI also promoted functional recovery, as assessed by contractile force measurements. Tissue reconstruction was associated with the formation of both neural and vascular networks and the reconstitution of a functional SC niche. This innovative approach could overcome previous limitations in skeletal muscle tissue engineering.

The mammalian Target of Rapamycin (mTOR) is a molecular complex equipped with kinase activity which controls cell viability being key in the PI3K/PTEN/Akt pathway. mTOR acts by integrating a number of environmental stimuli to regulate cell growth, proliferation, autophagy, and protein synthesis. These effects are based on the modulation of different metabolic pathways. Upregulation of mTOR associates with various pathological conditions, such as obesity, neurodegeneration, and brain tumors. This is the case of high-grade gliomas with a high propensity to proliferation and tissue invasion. Glioblastoma Multiforme (GBM) is a WHO grade IV malignant, aggressive, and lethal glioma. To date, a few treatments are available although the outcome of GBM patients remains poor. Experimental and pathological findings suggest that mTOR upregulation plays a major role in determining an aggressive phenotype, thus determining relapse and chemoresistance. Among several activities, mTOR-induced autophagy suppression is key in GBM malignancy. In this article, we discuss recent evidence about mTOR signaling and its role in normal brain development and pathological conditions, with a special emphasis on its role in GBM.

An in vitro muscle-like structure with parallel-oriented contractile myotubes is needed as a model of muscle tissue regeneration. For this purpose, it is necessary to reproduce a controllable microscale environment mimicking the in vivo cues. In this work we focused on the application of topological and electrical stimuli on muscle precursor cell (MPC) culture to influence MPC orientation and induce myotube alignment. The two stimulations were tested both independently and together. A structural and topological template was achieved using micropatterned poly-(L-lactic acid) membranes. Electrical stimulation, consisting of square pulses of 70 mV/cm amplitude each 30 s, was applied to the MPC culture. The effect of different pulse durations on cultures was evaluated by galvanotaxis analysis. The highest cell displacement rate toward the cathode was observed for 3 ms pulse stimulation, which was then applied in combination with topological stimuli. Topological and electrical stimuli had an additive effect in enhancing differentiation of cultured MPC, shown by high Troponin I protein production and, in parallel, Myogenin and Desmin genes, down- and upregulation respectively.

The production of engineered three-dimensional (3D) skeletal muscle grafts holds promise for treatment of several diseases. An important factor in the development of such approach involves the capability of preserving myogenicity and regenerative potential during ex vivo culturing. We have previously shown that electrical stimulation of myogenic cells grown in monolayer could improve the differentiation process. Here we investigated the effect of exogenous electrical field, specifically designed to mimic part of the neuronal activity, on muscle precursor cells (MPCs) cultured within 3D collagen scaffolds. Our data showed that electric stimulation did not affect cell viability and increased by 65.6% the release rate of NO(x), an early molecular activator of satellite cells in vivo. NO(x) release rate was decreased by an inhibitor of NO synthase, both in stimulated and non-stimulated cultures, confirming the endocrine origin of the measured NO(x). Importantly, electrical stimulation also increased the expression of two myogenic markers, MyoD and desmin. We also carried out some preliminary experiments aimed at determining the biocompatibility of our seeded collagen scaffolds, implanting them in the tibialis anterior muscles of syngeneic mice. Ten days after transplantation, we could observe the formation of new myofibers both inside the scaffold and at the scaffold/muscle interface. Altogether, our findings indicate that electrical stimulation could be a new strategy for the effective 3D expansion of muscle precursor cells in vitro without losing myogenic potential and that 3D collagen matrices could be a promising tool for delivering myogenic cells in recipient muscles.