Preparation and characterization of 12-HSA-based organogels as injectable implants for the controlled delivery of hydrophilic and lipophilic therapeutic agents.

Organogels prepared with low molecular weight organogelators to structure liquid oils represent excellent matrices for the controlled delivery of a wide variety of drug molecules. Although studies on organogel systems are reported in the literature, relatively few investigate their potential as gels formed in situ intended for drug delivery. This study reports the development of injectable subcutaneous 12- hydroxystearic acid (12-HSA) organogels for the delivery of both lipophilic and hydrophilic drugs. The rheological characterization (flow, dynamic temperature ramp and amplitude oscillatory measurements) and physicochemical properties (syringeability, swelling and degradation studies), as well as permeability and cytotoxicity were analyzed to gain insights into the influence of the gel composition (surfactant addition, organogelator concentration) on the gelation process and organogel properties. Sol-gel phase transition temperature (Tgel) and gel-sol phase transition temperature (Tmelt) were determined by the tube-inverting method and complementary rheology studies. An increase in 12-HSA concentration led to an augmentation in gel strength and storage (G') and loss (G″) moduli values, evidencing the self-assembly of crystalline gelator structure entrapping the oil phase into a three-dimensional (3D) network. The addition of polysorbate 80 (Tween 80, T80) surfactant molecules in the system caused a weaker gel-like structure, with lower flow rate during syringeability assays, despite its lower apparent viscosity compared to those of 12-HSA organogels. In addition, the swelling studies of 12-HSA/12-HSA T80 organogels as a function of time in phosphate buffered saline (PBS) revealed that the erosion rates were modulated by the organogel compositions. The permeability of acyclovir (ACV) and clotrimazole (CTM), hydrophilic and lipophilic model drugs, respectively, loaded in 12-HSA-based organogels, was assessed in Franz diffusion cells. Organogel-loaded drugs presented lower in vitro release rates and ex vivo drug permeabilities compared to the corresponding drug solutions. Furthermore, 12-HSA T80 organogel could slow down the release of ACV by a factor of about 2.6-fold, up to 6 h, compared to CTM-loaded 12-HSA organogels. Finally, the cytotoxicity of 12-HSA-based organogels was evaluated through in vitro cell viability assays in human foreskin fibroblasts (HFF). Increased 12-HSA concentration resulted in higher cytotoxic effect, with a higher test sensitivity observed for the 3D collagen-embedded cell layer setup matrix versus 2-D cell cultures. Our results support the hypothesis that 12-HSA-based organogels are promising systems for controlled drug delivery as in situ-forming implants.

HDAC1 and HDAC2 restrain the intestinal inflammatory response by regulating intestinal epithelial cell differentiation.

Acetylation and deacetylation of histones and other proteins depends on histone acetyltransferases and histone deacetylases (HDACs) activities, leading to either positive or negative gene expression. HDAC inhibitors have uncovered a role for HDACs in proliferation, apoptosis and inflammation. However, little is known of the roles of specific HDACs in intestinal epithelial cells (IEC). We investigated the consequences of ablating both HDAC1 and HDAC2 in murine IECs. Floxed Hdac1 and Hdac2 homozygous mice were crossed with villin-Cre mice. Mice deficient in both IEC HDAC1 and HDAC2 weighed less and survived more than a year. Colon and small intestinal sections were stained with hematoxylin and eosin, or with Alcian blue and Periodic Acid Schiff for goblet cell identification. Tissue sections from mice injected with BrdU for 2 h, 14 h and 48 h were stained with anti-BrdU. To determine intestinal permeability, 4-kDa FITC-labeled dextran was given by gavage for 3 h. Microarray analysis was performed on total colon RNAs. Inflammatory and IEC-specific gene expression was assessed by Western blot or semi-quantitative RT-PCR and qPCR with respectively total colon protein and total colon RNAs. HDAC1 and HDAC2-deficient mice displayed: 1) increased migration and proliferation, with elevated cyclin D1 expression and phosphorylated S6 ribosomal protein, a downstream mTOR target; 2) tissue architecture defects with cell differentiation alterations, correlating with reduction of secretory Paneth and goblet cells in jejunum and goblet cells in colon, increased expression of enterocytic markers such as sucrase-isomaltase in the colon, increased expression of cleaved Notch1 and augmented intestinal permeability; 3) loss of tissue homeostasis, as evidenced by modifications of claudin 3 expression, caspase-3 cleavage and Stat3 phosphorylation; 4) chronic inflammation, as determined by inflammatory molecular expression signatures and altered inflammatory gene expression. Thus, epithelial HDAC1 and HDAC2 restrain the intestinal inflammatory response, by regulating intestinal epithelial cell proliferation and differentiation.