Introduction: Iron deficiency anemia (IDA) represents a major public health problem. Oral administration has been recognized as the most convenient and safest route for iron treatment. However, most of the traditional iron supplements encounter several obstacles when orally administrated due to their poor solubility and bioavailability. The absorption of commonly used ferrous iron salts is low as the soluble form ferrous iron is easily oxidized to a poorly soluble one ferric iron and also because the absorption of ferrous iron is mediated by the divalent metal transporter 1. In order to overcome gastrointestinal barriers, there is a need for new absorption and protective enhancers acting as carriers and able to promote iron absorption. Microfold cells (M cells) of the Peyer's patches (PP) are found in the gut and mucosa-associated lymphoid tissues. These cells are known for the transport of microbes and particles across the epithelial cell layer from the gut lumen to the lamina propria where interactions with immune cells take place. Previous studies demonstrate that M cells are a common pathway for oral nanoparticles absorption. However physicochemical properties of particles critically influence the efficacy of oral delivery to the lymphatic system. Recently, we have developed a new oral Iron formulation named Sucrosomial® Iron. This oral formulation is an innovative preparation of ferric pyrophosphate, covered by a phospholipids plus sucrester matrix, with high bioavailability, tolerability and gastro-resistance properties that shows an improvement in Hb levels similarly to intravenous iron and without any gastrointestinal side effects; thus, Sucrosomial®Iron can be used as an alternative to common iron salts to improve iron supplementation effectiveness.
Aim: to investigate Sucrosomial® Iron absorption pathways using different experimental models.
Methods: In order to study the absorption pathways of Sucrosomial® Iron, absorption and transport experiments were performed using in vitro CACO2/RajiB co-culture system and MatTek EpiIntestinalTM human 3D in vitro small intestinal tissue model with epithelialpolarity. Furthermore, the bioavailability of Sucrosomial® Iron was assessed, in terms of tissue distribution and iron metabolism markers expression, using in vivo and ex-vivo models.
Results: in vitro transport study using MatTek EpiIntestinalTM model showed a fast increase in iron concentration in the basolateral compartment over time in tissues treated with Sucrosomial® Iron (2,7 ug ±1,7) compare to samples treated with Ferrous Sulfate (1,3 ug ±1,1) or Iron Bisglycinate (1,6 ug ±1,1), indicating an endocytosis mediated uptake confirmed by TEM analysis (Figure 1A-B). M cells involvement was evaluated using in vitro CACO2/RajiB co-culture system. After cells incubation, the iron content in apical media of cells (monocultures and co-cultures) treated with Sucrosomial® Iron was significantly lower compare to cells treated with other iron formulations (Figure 2A). Iron to protein ratio showed a significant iron increase in co-colture cells treated with Sucrosomial® Iron compared to other iron samples (Figure 2B). Sucrosomial® Iron, passed through M cells, was taken up by CD68+ macrophage cells as confirmed by ex-vivo experiments, in which fluorescein tagged Sucrosomial® Iron was added to an isolated rat intestine using Hussing chamber-like model, then analyzed by immunohistochemistry. To study the reticuloendothelial system involvement, tissue distribution and bioavailability of Sucrosomial® Iron were analyzed using anemic newborn piglets. Animals were treated with Sucrosomial® Iron or Iron dextran and piglets treated with Sucrosomial® Iron showed anincreased Hb concentration and a preferential iron accumulation in spleen (Figure 3A-B). Hepcidin and Ferroportin, but not Dmt1 gene expression were induced at duodenum level (Figure 3C).
CONCLUSIONS: these results showed that Sucrosomial® Iron can be directly absorbed bypassing the conventional iron absorption pathway and that M cells, through the reticuloendothelial system, may contribute to its absorption and tissue distribution.
Brilli: Pharmanutra S.p.A.: Consultancy. Tarantino: Pharmanutra S.p.A.: Employment.
Asterisk with author names denotes non-ASH members.