On the Anticoagulant Activities of Acidic Polysaccharides from the Western Mediterranean Sea Porifera

Innovation in the field of bioinspired therapeutic anticoagulants, as an alternative to heparin and its derivatives, is increasingly focused toward the discovery of new molecules from natural sources. Inspired by the compelling observation that marine organisms possess a wide array of acidic polysaccharides (APs) within their extracellular matrix (ECM) with promising anticoagulant potential, this study investigates AP topographic distribution, content, and bioactivity in the body of seven phylogenetically distant Mediterranean sponge species. Tissue architecture was evidenced by Alcian Blue histological staining whereas biochemical analyses were carried out on APs purified from papain-digested tissue extracts using anion-exchange chromatography. Four polysaccharide fractions were obtained and assessed for hexuronic acid content. The two most abundant ones, up to 98% of the total, were characterized by electrophoretic analyses, and assessed in vitro for inhibitory activity on blood coagulation. Histology evidenced a heterogeneous distribution of APs within the sponge’s ECM, along with marked interspecific variability in both concentration and electrophoretic profiles. Neither Tethya aurantium nor Crambe crambe showed any significant in vitro effects on coagulation, whereas the other species exhibited a strong inhibitory effect on both activated partial thromboplastin time (aPTT) and thrombin time (TT), comparable to standard heparin (Hep). Concerning aPTT, both I. retidermata and H. communis reached the endpoint of 300 s at 5 µgUA/mL, whereas S. spinosulus, O. lobularis, A. aerophoba reached it at 10 µgUA/mL. With reference to TT, A. aerophoba, I. retidermata, S. spinosulus and H. communis had comparable effects on coagulation time with respect to Hep (endpoint at 5 µgUA/mL), whereas O. lobularis was less effective (endpoint at 100 µgUA/mL). These findings show that Porifera, one of the most basal Metazoa, have an ECM rich in APs with anticoagulant properties towards both intrinsic and common pathways of coagulation, consistent with known inhibitory mechanisms reported for certain marine sulfated polysaccharides derived from other invertebrate taxa. These molecules, obtainable through sustainable blue technology, represent compelling candidates for bioinspired next-generation anticoagulant therapeutics, with broader applications in regenerative medicine and tissue engineering.