Development of Targeted Nanoscale Drug Delivery System for Osteoarthritic Cartilage Tissue.

Osteoarthritis is a severe and debilitating joint disease, which is characterized as results from damage and degeneration of the articular cartilage of the joint surfaces. The incidence of osteoarthritis is growing increasingly high while current treatment methods remain suboptimal. The major issue for current osteoarthritic medications is that patients frequently experience adverse, nonspecific side effects that are not a direct result of the specific pharmacological action of the drug. The treatment processes could be made more effective, safe, and comfortable if it were possible to deliver the drugs specifically to cartilage tissue. Therefore, developing site-specific and controlled drug release delivery systems is needed for overcoming the aforementioned issues. We have developed a poly(lactic-co-glycolic acid) (PLGA)-based nanoscale drug delivery system based on a short cartilage-targeting peptide sequence: WYRGRL. Nanoparticles (NPs) made of methoxy-poly(ethylene glycol) (PEG)-PLGA and maleimide-PEG-PLGA were prepared using a water-in-oil-in-water double emulsion and solvent evaporation method. Fluorescein isothiocyanate (FITC)-tagged WYRGRL peptide was then linked to the surface of the nanoparticles through the alkylation reaction between the sulfhydryl groups at the N-terminal of the peptide and the C═C double bond of maleimide at one end of the polymer chain to form thioether bonds. The conjugation of FITC-tagged WYRGRL peptide to PLGA NPs was confirmed by NMR technique. We further demonstrated that the novel delivery system binds very specifically to cartilage tissue in vitro and ex vivo. Given that biodegradable PLGA-based NPs have shown promise for drug delivery, they could be used for a positive advancement for treatments of osteoarthritic patients by creating a more effective treatment process that achieves healing results faster and with fewer deleterious side effects. Taken together, these promising results indicated that this nanoscale targeting drug delivery system was able to bind to cartilage tissue and might have a great potential for treating osteoarthritis.

Osteotropic nanoscale drug delivery systems based on small molecule bone-targeting moieties.

Bone-targeted drug delivery is an active research area because successful clinical applications of this technology can significantly advance the treatment of bone injuries and disorders. Molecules with bone-targeting potential have been actively investigated as promising moieties in targeted drug delivery systems. In general, bone-targeting molecules are characterized by their high affinity for bone and their predisposition to persist in bone tissue for prolonged periods, while maintaining low systemic concentrations. Proteins, such as monoclonal antibodies, have shown promise as bone-targeting molecules; however, they suffer from several limitations including large molecular size, high production cost, and undesirable immune responses. A viable alternative associated with significantly less side effects is the use of small molecule-based targeting moieties. This review provides a summary of recent findings regarding small molecule compounds with bone-targeting capacity, as well as nanoscale targeted drug delivery approaches employing these molecules.

Controlling the Growth of the Skin Commensal Staphylococcus epidermidis Using d-Alanine Auxotrophy.

Using live microbes as therapeutic candidates is a strategy that has gained traction across multiple therapeutic areas. In the skin, commensal microorganisms play a crucial role in maintaining skin barrier function, homeostasis, and cutaneous immunity. Alterations of the homeostatic skin microbiome are associated with a number of skin diseases. Here, we present the design of an engineered commensal organism, Staphylococcus epidermidis, for use as a live biotherapeutic product (LBP) candidate for skin diseases. The development of novel bacterial strains whose growth can be controlled without the use of antibiotics or genetic elements conferring antibiotic resistance enables modulation of therapeutic exposure and improves safety. We therefore constructed an auxotrophic strain of S. epidermidis that requires exogenously supplied d-alanine. The S. epidermidis NRRL B-4268 Δalr1 Δalr2 Δdat strain (SEΔΔΔ) contains deletions of three biosynthetic genes: two alanine racemase genes, alr1 and alr2 (SE1674 and SE1079), and the d-alanine aminotransferase gene, dat (SE1423). These three deletions restricted growth in d-alanine-deficient medium, pooled human blood, and skin. In the presence of d-alanine, SEΔΔΔ colonized and increased expression of human ß-defensin 2 in cultured human skin models in vitro. SEΔΔΔ showed a low propensity to revert to d-alanine prototrophy and did not form biofilms on plastic in vitro. These studies support the potential safety and utility of SEΔΔΔ as a live biotherapeutic strain whose growth can be controlled by d-alanine.IMPORTANCE The skin microbiome is rich in opportunities for novel therapeutics for skin diseases, and synthetic biology offers the advantage of providing novel functionality or therapeutic benefit to live biotherapeutic products. The development of novel bacterial strains whose growth can be controlled without the use of antibiotics or genetic elements conferring antibiotic resistance enables modulation of therapeutic exposure and improves safety. This study presents the design and in vitro evidence of a skin commensal whose growth can be controlled through d-alanine. The basis of this strain will support future clinical studies of this strain in humans.

Repositioning Tacrolimus: Evaluation of the Effect of Short-Term Tacrolimus Treatment on Osteoprogenitor Cells and Primary Cells for Bone Regenerative Engineering.

Small-molecule-based bone regenerative engineering is an encouraging strategy for repair and regeneration of skeletal tissue. Using osteogenic small molecules for engineering bone tissue has several potential benefits over polypeptide-based approaches. Interestingly, hundreds of such small molecules possess the capability to promote osteogenesis, and several of these are already approved by the FDA for use in other applications, indicating their safety for human use. However, the need for their use at a high frequency and/or duration, due to their short half-life and nonspecificity, is still problematic. We, and others, have identified several non-FDA-approved small-molecule-based compounds that induce long-lasting osteogenic effects following short-term (<24 h) treatment. In this study, however, we have performed a proactive screen to investigate and compare the osteogenic effects of several preselected FDA-approved small-molecule drugs in vitro using osteoprogenitor MC3T3-E1 cells. Our results demonstrate that treatment with the small-molecule drug tacrolimus (FK-506) for 24 h significantly enhanced long-lasting osteogenic responses in both osteoprogenitor cells and primary cell cultures. In addition, we tested whether a short-term treatment with FK-506 is able to induce osteogenic differentiation of cells seeded on a polymeric scaffold in vitro. Using an osteogenic small molecule that has long-lasting effects despite a short duration of exposure to cells may alleviate the undesirable effects often seen with many osteogenic small molecules.

Engineered Bone Tissue with Naturally-Derived Small Molecules.

Natural products remain the best resources of drugs and drug leads. Recently, there is growing recognition that identifying new small molecules to promote bone regeneration is a laudable translational goal. In fact, new approaches for bone repair and regeneration that involve inexpensive naturally-derived compounds would have an important impact on the treatment of bone disorders and injuries. Over the past several decades, a number of naturally-derived small molecules with the potential of regenerating bone tissue (i.e. osteoinductive) have been reported in the literature. Here, we review the current literature, paying attention to the prospects for natural small molecule-based bone regenerative engineering. We also review various delivery strategies of the selected naturally- derived small molecules for bone regenerative engineering applications.

Harnessing cAMP signaling in musculoskeletal regenerative engineering.

This paper reviews the most recent findings in the search for small molecule cyclic AMP analogues regarding their potential use in musculoskeletal regenerative engineering.