## 4 Discussion  
In recent years, intensive efforts have been made to identify new treatments to stop chronic hepatopathies' progression and improve their prevention. The possible options also include dietary supplements and nutraceuticals [28; 29]. These products are commonly used worldwide, both as a supplement to conventional drug therapies and as a replacement for them. However, there is a dispute about the real therapeutic effect of food supplements and considering the increasing use of these products both in the US and in the EU [7; 30; 31; 32; 33], their possible hepatotoxicity is an issue that is increasingly worrying the scientific community. The main difficulty in evaluating the real therapeutic action of these supplements lies in the qualitative and quantitative variability of their components. There is a broad spectrum of food supplements of different nature and origin. They are often produced from natural herbs or prepared as mixtures of biologically active substances such as vitamins, minerals, amino acids, and/or proteins. In some cases, they can sometimes contain anabolic steroids or other synthetic compounds, potentially harmful to the liver [33]. Since the liver is the organ responsible for the inactivation of most toxins from the body, some of the components of the supplements and their metabolites can cause damage at different degrees, such as cellular stress, mitochondrial inhibition, and immune reactions [34]. In addition to the risk associated with the components of the food supplements, some other factors increase the risk of the onset of hepatotoxicity, including older age, female sex, high dosage, malnutrition, alcohol abuse, genetic factors, interactions with other drugs, or the presence of concomitant diseases [35; 36]. The clinical symptoms presentation and severity can be extremely variable, starting from mild hepatitis up to acute liver failure [37]. Furthermore, these supplements are generally administered without a prescription or specific medical advice and without monitoring over time. Moreover, unlike conventional drugs, food supplements' safety and efficacy are not always well-defined and or/declared by the producer [7]. In the last years, liver extract has been investigated as a drug for improving liver functions and restoring homeostasis in chronic liver diseases [38]. Most of the studies have been performed in vitro or in animal experimental models aimed to demonstrate the role of liver-specific environment on tissue homeostasis and regeneration. Since hepatocytes' specific characteristics are lost when cells are removed from their native environment, the identification of biological substrates or supplement resembling the liver environment is an active field of research aimed at ensuring proper cell growth, differentiation and, in perspective, organ reconstruction [10]. Liver extracts are a complex mixture of bioactive factors: soluble molecules (proteins, low-molecular-weight nutrients, vitamins, microelements), extracellular matrix components, and more complex supra-molecular structures such as exosomes and microvesicles [10; 22]. Recent findings suggest that the liver itself produces a secretone endowed with anti-inflammatory properties [22]. In this context, a supplement based on liver from healthy animals could be worthy of analysis [39], both as nutraceutical and substrate for studying hepatocyte biology. The aim of this work was the preliminary assessment of the in vitro bioactivity and safety of a freeze-dried liver preparation of porcine origin. The lyophilized liver powder's (LLP's) effects on metabolic and proliferative activity have been evaluated on two cell lines: the human-derived immortalized HepG2 hepatic cell line and the primary culture of mesenchymal stromal cells (MSCs) derived from adipose tissue (At-MSCs). The HepG2 cell line represents a model widely used by scientific literature to evaluate hepatocyte biology in vitro since it maintains many differentiated hepatic functions [25].