Manuela Malatesta

Procaine is a local anesthetic used at low concentrations in a complementary medical approach, neural therapy, due to its ability to promote antioxidant and anti-inflammatory response. Previous biochemical studies showed that low concentrations of procaine may also stimulate mitochondrial function. In the present study, low procaine concentrations were used to investigate in vitro the effects on mitochondria of human fibroblasts and mouse myoblasts. Histochemical, ultrastructural, and biomolecular techniques were employed. After 24 h from procaine treatment, mitochondrial membrane potential was unaltered in both cell types, but some mitochondrial features showed cell-specific modifications. In detail, in fibroblasts, procaine induced decreased mitochondrial cristae length and cellular adenosine triphosphate (ATP) levels. In myoblasts, procaine induced modifications of mitochondrial shape and oxidative phosphorylation subunit amount, together with increased cellular ATP levels. Most modifications were restored at 48 h. To explain the differential response of the two cell lines, we hypothesize a species-specific sensitivity to procaine or a cell-specific sensitivity related to the different extent of the endoplasmic reticulum, which is especially susceptible to procaine. Taken together, the results of this pilot study show that procaine at low concentration exerts a modulatory effect on mitochondrial features, opening the way to further studies aimed at elucidating the cellular pathways involved in the beneficial effects observed in procaine-based neural therapy.

During aging, skeletal muscle undergoes a decline in mass and strength. This condition, known as sarcopenia, involves many physiological and metabolic impairments, thus representing a healthcare, social, and economic burden. Various pharmacological and non-pharmacological approaches have been explored to counteract sarcopenia; however, no definite treatment has so far been found. The present narrative review summarizes nanotechnology-based strategies designed to promote muscle preservation and functional recovery in aging. Synthetic organic or inorganic nanoconstructs and natural extracellular vesicles have been used as nanocarriers for drug delivery, have been active as intrinsic therapeutic agents, have been employed to build biomimetic nanoscaffolds to sustain muscle regeneration, or have been combined to form hybrid nanosystems with multiple therapeutic functions. These nanotools demonstrated promising results in vitro and in animal models, being able to counteract major factors responsible for sarcopenia, such as oxidative stress, inflammation, mitochondrial dysfunction, increased proteolysis, and impaired stem cell function. However, nanotools have mostly been tested on biological models far from the physiologically aged human muscle. Moreover, limitations still remain to be solved to make these nanotools suitable for regenerative medicine; in particular, the systemic administration requires nanoconstruct functionalization for skeletal muscle targeting, and proper clearance should be ensured to avoid toxicity and immunogenicity related to long-term use.

In the last decades, ozone (O₃)-based medical treatments have become a widely applied complementary therapy for several pathological conditions. O₃ is administered at low dosages since the induction of a mild oxidative stress does not cause damage but stimulates the antioxidant cell response through the nuclear factor erythroid 2-related factor 2 (Nrf2). Mitochondria are sensitive to even mild oxidative stress, thus being a responsive target for O₃. This study aimed to evaluate the mitochondrial response to low O₃ doses used for medical treatments. As the skeletal muscle represents a primary target in local O₃ treatments, a murine non-tumoral muscle cell line was selected as an appropriate in vitro model. Transmission electron microscopy, biochemistry, and flow cytometry provided original information on the O₃ dose-dependent modifications of mitochondrial structural and molecular features. Low O₃ doses promoted an increase in mitochondrial area and in cristae extension, as well as an enhancement of the electron transport chain complexes and of antioxidant catalase and manganese-dependent superoxide dismutase. Nrf2 maintained its association with the outer mitochondrial membrane, thus exerting its protective role. All mitochondrial modifications were observed 24 h after treatment and disappeared after 48 h, demonstrating that cells promptly respond to the O₃-driven oxidative stress, effectively restoring homeostasis.

Ozone (O3) is an oxidizing natural gas widely applied as adjunctive therapeutic treatment for a variety of pathological conditions. Currently, O3-based therapies rely on the low-dose concept i.e., the administration of low O3 concentrations able to induce a mild oxidative stress stimulating antioxidant and anti-inflammatory response without causing cell damage. In addition, low O3 concentrations are thought to activate cellular and molecular mechanisms responsible for analgesic and regenerative effects. Due to these properties, in the last decade interest has arisen in the fields of orthopedics and regenerative medicine on the potential of O3 to counteract joint diseases involving cartilage degeneration. In this pilot study, we have explored the anti-degenerative potential of O3 on knee articular cartilage explanted from a healthy adult rabbit and maintained in vitro. Light and transmission electron microscopy were used to monitor chondrocyte and extracellular matrix features of cartilage samples undergoing O3 treatment every three days for two weeks. Results demonstrated that low O3 concentrations act on chondrocytes and the molecular components of the extracellular matrix of articular cartilage explants, significantly improving their preservation under in vitro conditions, likely by promoting both protective and pro-regenerative pathways. This opens promising perspectives for further investigations on the therapeutic potential of O3 for the treatment of cartilage degeneration not only as painkilling and anti-inflammatory agent but also as a cartilage regenerative agent.

Skeletal muscle is a complex organ that undergoes aging through a multifactorial process leading to muscle atrophy and strength reduction. Mitochondrial dysfunctions prove to be a critical contributor to skeletal muscle aging, affecting the regenerative functions and differentiation of muscle satellite cells (MuSCs). Physical exercise is a nonpharmacological approach that positively affects mitochondrial functions, promoting increased mitochondrial biogenesis, enzyme activities, and respiration in the aging skeletal muscle. By means of morphological and morphometrical analyses at transmission electron microscopy, this in vitro study identified the fine structural modifications induced in mitochondria of MuSC‐derived myoblasts by a long‐term adapted physical exercise applied to old mice, and verified the persistence of the exercise‐driven changes in the myoblast‐derived myotubes. In myoblasts, physical exercise decreased mitochondrial volume while increasing mitochondrial elongation and cristae extension in comparison to the sedentary condition, a mitochondrial remodeling suggestive of higher functionality. In myotubes, physical exercise increased mitochondrial volume and decreased cristae extension, partially reverting the age‐associated alterations. These findings demonstrate that physical exercise administered in elderly exerts positive effects on mitochondria of the progeny of resident MuSCs.

The intestine is a complex organ whose main functions are food digestion and nutrient absorption. It is therefore of great interest for pharmaceutical research as a preferred route for drug delivery. In vitro intestinal models are valuable tools for the preclinical evaluation of absorption, distribution, metabolism, and excretion of new therapeutic formulations; consequently, several attempts have been made to recreate the human intestine barrier in vitro. The models so far set up were aimed at mimicking specific intestinal features related to the molecules or processes under investigation. Artificial membranes are suitable to study passive absorption; systems based on 2D/3D cell cultures reproduce the transcellular pathway; organs-on-a-chip mimic the in vivo cellular and mechanical complexity, allowing the identification of the multiple factors involved in molecular interactions with the intestinal barrier; and intestine explants replicate in full the native organ under controlled conditions, thus providing the most comprehensive in vitro model. All these models have advantages and disadvantages but all have given important contribution to advance the knowledge on the interaction of drugs, toxins, and xenobiotic with the intestinal barrier.

Ozone (O₃) occurs in nature as a chemical compound made of three oxygen atoms. It is an unstable, highly oxidative gas that rapidly decomposes into oxygen. The therapeutic use of O₃ dates back to the beginning of the 20th century and is currently based on the application of low doses, inducing a moderate oxidative stress that stimulates the antioxidant cellular defenses without causing cell damage. Low O₃ doses also induce anti-inflammatory and regenerative effects, and their anticancer potential is under investigation. In addition, the oxidative properties of O₃ make it an excellent antibacterial, antimycotic, and antiviral agent. Thanks to these properties, O₃ is currently widely used in several medical fields. However, its chemical instability represents an application limit, and ozonated oil is the only stabilized form of medical O₃. In recent years, novel O₃ formulations have been proposed for their sustained and more efficient administration, based on nanotechnology. This review offers an overview of the nanocarriers designed for the delivery of medical O₃, and of their therapeutic applications. The reviewed articles demonstrate that research is active and productive, though it is a rather new entry in the nanotechnological field. Liposomes, nanobubbles, nanoconstructed hydrogels, polymeric nanoparticles, and niosomes were designed to deliver O₃ and have been proven to exert antiseptic, anticancer, and pro-regenerative effects when administered in vitro and in vivo. Improving the therapeutic administration of O₃ through nanocarriers is a just-started challenge, and multiple prospects may be foreseen.

Regenerative medicine is a relatively young field, born as a convergence of disparate disciplines aimed at restoring or replacing tissues and organs

The skeletal muscle is a complex organ mainly composed of multinucleated fibres responsible for contractile activity, but it also contains postnatal myogenic stem cells (i.e., satellite cells), connective cells and nervous cells. The skeletal muscle is severely affected by aging, undergoing a progressive reduction in muscle mass, strength and endurance in a condition known as sarcopenia. The mechanisms underlying sarcopenia still need to be completely clarified, but they are undoubtedly multifactorial, involving all cell types constituting the skeletal muscle. Immunohistochemistry has widely been used to investigate skeletal muscle aging, identifying age-related molecular alterations in the various myofibre components, as well as in the satellite cells and peri-fibre environment. The wide range of immunohistochemical data reported in this review is proof of the primary role played by this long-established, yet modern, technique. Its high specificity for the molecules of interest, and the possibility of imaging and quantifying the signal in the real histological or cytological sites where these molecules are located and active, makes immunohistochemistry a unique and irreplaceable tool among the laboratory techniques in biomedicine.