Effect of pegylated phosphatidylserine-containing liposomes in experimental chronic arthritis

Towards the Development of Long Circulating Phosphatidylserine (PS)- and Phosphatidylglycerol (PG)-Enriched Anti-Inflammatory Liposomes: Is PEGylation Effective?

The anionic phospholipids (PLs) phosphatidylserine (PS) and phosphatidylglycerol (PG) are endogenous phospholipids with anti-inflammatory and immunomodulatory activity. A potential clinical use requires well-defined systems and for several applications, a long circulation time is desirable. Therefore, we aimed the development of long circulating liposomes with intrinsic anti-inflammatory activity. Hence, PS- and PG-enriched liposomes were produced, whilst phosphatidylcholine (PC) liposomes served as control. Liposomes were either formulated as conventional or PEGylated formulations. They had diameters below 150 nm, narrow size distributions and composition-dependent surface charges. Pharmacokinetics were assessed non-invasively via in vivo fluorescence imaging (FI) and ex vivo in excised organs over 2 days. PC liposomes, conventionally formulated, were rapidly cleared from the circulation, while PEGylation resulted in prolongation of liposome circulation robustly distributing among most organs. In contrast, PS and PG liposomes, both as conventional or PEGylated formulations, were rapidly cleared. Non-PEGylated PS and PG liposomes did accumulate almost exclusively in the liver. In contrast, PEGylated PS and PG liposomes were observed mainly in liver and spleen. In summary, PEGylation of PS and PG liposomes was not effective to prolong the circulation time but caused a higher uptake in the spleen.

Reduction of fibrous encapsulation by polyethylene glycol-grafted liposomes containing phosphatidylserine

Biomedical implants tend to induce fibrous encapsulation which can cause malfunction of devices and local discomfort of patients. The purpose of this study was to reduce foreign body-induced fibrous capsule formation by immunomodulation of macrophages. Polyethylene-glycol-grafted liposomes containing phosphatidylserine (PEG-PSLs) were used to modulate macrophages. Mixed cellulose ester (MCE) membranes coated with a PEG-PSLs-entrapped alginate-gelatin matrix were subcutaneously implanted into rats, and the thickness of the fibrous capsule around each MCE membrane was analyzed after four weeks. PEG-PSLs significantly reduced fibrous capsule thickness, while liposomes containing phosphatidylserine (PSLs) did not affect fibrosis. In in vitro assays, PEG-PSLs suppressed TGF-β1 secretion and multinucleated giant cell (MGC) formation in IL-4-treated RAW 264.7, a murine macrophage cell line. Although PSLs inhibited MGC formation, they exerted no effect on the secretion of TGF- β1, which is known to be an important factor in tissue fibrosis. Therefore, our results suggest that PEG-PSLs reduce fibrous capsule formation by mediating the suppression of TGF-β1 secretion from macrophages.

Phosphatidylserine (PS) and phosphatidylglycerol (PG) enriched mixed micelles (MM): A new nano-drug delivery system with anti-inflammatory potential?

Phosphatidylserine (PS) and phosphatidylglycerol (PG) are naturally occurring phospholipids (PL) with intrinsic anti-inflammatory properties. The therapeutic potential of PS and PG has not been extensively explored and the main focus had been directed towards PS- and PG-liposomes. In order to increase the formulation options, we explored whether mixed micelles (MM) could be an alternative to liposomes. Potential advantages of MM are their thermodynamic stability, small size and ease of manufacture. DOPS- and DOPG-enriched MM were obtained via a co-precipitation technique and physicochemical characterization was performed. The MM, approximately 10 nm in diameter, showed no toxicity on fibroblast cell lines in vitro and virtually no hemolytic activity. The MM suppressed the TNFα-production of mIFNγ/LPS-stimulated mouse peritoneal macrophages (MPM) in vitro similar to DOPS- and DOPG-liposomes. Therefore, DOPS- and DOPG-loaded MM are promising new options for the treatment of inflammatory diseases.

Bioactive factors for cartilage repair and regeneration: Improving delivery, retention, and activity

Articular cartilage is a remarkable tissue whose sophisticated composition and architecture allow it to withstand complex stresses within the joint. Once injured, cartilage lacks the capacity to self-repair, and injuries often progress to joint wide osteoarthritis (OA) resulting in debilitating pain and loss of mobility. Current palliative and surgical management provides short-term symptom relief, but almost always progresses to further deterioration in the long term. A number of bioactive factors, including drugs, corticosteroids, and growth factors, have been utilized in the clinic, in clinical trials, or in emerging research studies to alleviate the inflamed joint environment or to promote new cartilage tissue formation. However, these therapies remain limited in their duration and effectiveness. For this reason, current efforts are focused on improving the localization, retention, and activity of these bioactive factors. The purpose of this review is to highlight recent advances in drug delivery for the treatment of damaged or degenerated cartilage. First, we summarize material and modification techniques to improve the delivery of these factors to damaged tissue and enhance their retention and action within the joint environment. Second, we discuss recent studies using novel methods to promote new cartilage formation via biofactor delivery, that have potential for improving future long-term clinical outcomes. Lastly, we review the emerging field of orthobiologics, using delivered and endogenous cells as drug-delivering "factories" to preserve and restore joint health. Enhancing drug delivery systems can improve both restorative and regenerative treatments for damaged cartilage. STATEMENT OF SIGNIFICANCE: Articular cartilage is a remarkable and sophisticated tissue that tolerates complex stresses within the joint. When injured, cartilage cannot self-repair, and these injuries often progress to joint-wide osteoarthritis, causing patients debilitating pain and loss of mobility. Current palliative and surgical treatments only provide short-term symptomatic relief and are limited with regards to efficiency and efficacy. Bioactive factors, such as drugs and growth factors, can improve outcomes to either stabilize the degenerated environment or regenerate replacement tissue. This review highlights recent advances and novel techniques to enhance the delivery, localization, retention, and activity of these factors, providing an overview of the cartilage drug delivery field that can guide future research in restorative and regenerative treatments for damaged cartilage.

Suppressing mPGES-1 expression by sinomenine ameliorates inflammation and arthritis

Recently, microsomal prostaglandin E synthase 1 (mPGES-1) has attracted much attention from pharmacologists as a promising strategy and an attractive target for treating various types of diseases including rheumatoid arthritis (RA), which could preserve the anti-inflammatory effect while reducing the adverse effects often occur during administration of non-steroidal anti-inflammatory drugs (NSAIDs). Here, we report that sinomenine (SIN) decreased prostaglandin (PG)E₂ levels without affecting prostacyclin (PG)I₂ and thromboxane (TX)A₂ synthesis via selective inhibiting mPGES-1 expression, a possible reason of low risk of cardiovascular event compared with NSAIDs. In addition, mPGES-1 protein expression was down-regulated by SIN treatment in the inflamed paw tissues both in carrageenan-induced edema model in rats and the collagen-II induced arthritis (CIA) model in DBA mice. More interestingly, SIN suppressed the last step of mPGES-1 gene expression by decreasing the DNA binding ability of NF-κB, paving a new way for drug discovery.

Cartilage-targeting drug delivery: can electrostatic interactions help?

Current intra-articular drug delivery methods do not guarantee sufficient drug penetration into cartilage tissue to reach cell and matrix targets at the concentrations necessary to elicit the desired biological response. Here, we provide our perspective on the utilization of charge-charge (electrostatic) interactions to enhance drug penetration and transport into cartilage, and to enable sustained binding of drugs within the tissue's highly negatively charged extracellular matrix. By coupling drugs to positively charged nanocarriers that have optimal size and charge, cartilage can be converted from a drug barrier into a drug reservoir for sustained intra-tissue delivery. Alternatively, a wide variety of drugs themselves can be made cartilage-penetrating by functionalizing them with specialized positively charged protein domains. Finally, we emphasize that appropriate animal models, with cartilage thickness similar to that of humans, must be used for the study of drug transport and retention in cartilage.