Elimination of Senescent Osteocytes by Bone-Targeting Delivery of ß-Galactose-Modified Maytansinoid Prevents Age-Related Bone Loss.

The accumulation of senescent cells in bone during aging contributes to senile osteoporosis, and clearance of senescent cells by senolytics could effectively alleviate bone loss. However, the applications of senolytics are limited due to their potential toxicities. Herein, small extracellular vesicles (sEVs) have been modified by incorporating bone-targeting peptide, specifically (AspSerSer)6, to encapsulate galactose-modified Maytansinoids (DM1). These modified vesicles are referred to as (AspSerSer)6-sEVs/DM1-Gal, and they have been designed to specifically clear the senescent osteocytes in bone tissue. In addition, the elevated activity of lysosomal ß-galactosidase in senescent osteocytes, but not normal cells in bone tissue, could break down DM1-Gal to release free DM1 for selective elimination of senescent osteocytes. Mechanically, DM1 could disrupt tubulin polymerization, subsequently inducing senescent osteocytes apoptosis. Further, administration of bone-targeting senolytics to aged mice could alleviate aged-related bone loss without non-obvious toxicity. Overall, this bone-targeting senolytics could act as a novel candidate for specific clearance of senescent osteocytes, ameliorating age-related bone loss, with a promising therapeutic potential for senile osteoporosis.

ROS-responsive PPGF nanofiber membrane as a drug delivery system for long-term drug release in attenuation of osteoarthritis.

Excessive reactive oxygen species (ROS) are one of the leading mechanisms in the initiation and development of osteoarthritis (OA). However, conventional injection of ROS-responsive drug delivery systems (DDSs) such as nanoparticles and hydrogels usually cannot provide effective treatment due to rapid clearance and degradation or low bioavailability. In this study, a ROS-responsive nanofiber membrane named PLA/PEGDA-EDT@rGO-Fucoxanthin (PPGF) is fabricated by electrospinning, wherein PEGDA-EDT served as the ROS-responsive motif, reduced graphene oxide (rGO) as the drug carrier and fucoxanthin (Fx) as the antioxidative and anti-inflammatory agent. The results demonstrated that the PPGF nanofiber membrane exhibited sustained and long-term Fx release behavior (at least 66 days) in response to hydrogen peroxide (H2O2) in vitro. With low cytotoxicity and smart ROS responsiveness, PPGF showed excellent anti-inflammatory and antioxidative effects on IL-1ß-induced chondrocytes by potent ROS scavenging potential and upregulation of antioxidative enzymes. It also demonstrated the attenuation of OA progression with the reduced Osteoarthritis Research Society International (OARSI) score by 93.17% in 8 weeks. The smart ROS-responsive, biodegradable and biocompatible nanofiber membranes possess great potential for OA therapy under arthroscopy.

Platelet-rich plasma promotes the regeneration of cartilage engineered by mesenchymal stem cells and collagen hydrogel via the TGF-ß/SMAD signaling pathway.

The tissue engineering technique using mesenchymal stem cells (MSCs) and scaffolds is promising. Transforming growth factor-ß1 (TGF-ß1) is generally accepted as an chondrogenic agent, but immunorejection and unexpected side effects, such as tumorigenesis and heterogeneity, limit its clinical application. Autogenous platelet-rich plasma (PRP), marked by low immunogenicity, easy accessibility, and low-cost, may be favorable for cartilage regeneration. In our study, the effect of PRP on engineered cartilage constructed by MSCs and collagen hydrogel in vitro and in vivo was investigated and compared with TGF-ß1. The results showed that PRP promoted cell proliferation and gene and protein expressions of chondrogenic markers via the TGF-ß/SMAD signaling pathway. Meanwhile, it suppressed the expression of collagen type I, a marker of fibrocartilage. Furthermore, PRP accelerated cartilage regeneration on defects with engineered cartilage, advantageous over TGF-ß1, as evaluated by histological analysis and immunohistochemical staining. Our work demonstrates that autogenous PRP may substitute TGF-ß1 as a potent and reliable chondrogenic inducer for therapy of cartilage defect.

Andrographolide prevents human nucleus pulposus cells against degeneration by inhibiting the NF-κB pathway.

Intervertebral disc degeneration (IDD) is among the most common spinal disorders, pathologically characterized by excessive cell apoptosis and production of proinflammatory factors. Pharmacological targeting of nucleus pulposus (NP) degeneration may hold promise in IDD therapy, but it is limited by adverse side effects and nonspecificity of drugs. In this study, we used a natural compound, andrographolide (ANDRO), which has been widely used to intervene inflammatory and apoptotic diseases in the investigation of NP degeneration based on IDD-patients-derived NP cells by lipopolysaccharide (LPS) treatment for the preservation of degeneration. The results showed that LPS maintained the degeneration status of NP cells as evidenced by a high apoptosis rate and the expression of degenerative and inflammatory mediators after LPS treatment. ANDRO reversed the effects of LPS-caused degeneration of NP cells and maintained the phenotype of NP cells, as demonstrated by flow cytometry, degenerative mediators (ADAMTS4 and ADAMTS5), inflammatory factors (COX2, PGE2, MMP-13, and MMP-3), biomarkers of NP cells (SOX9, ACAN, and COL2A1) expressions, and glycosaminoglycan secretion. We also found the involvement of the nuclear factor kappa-light-chain-enhancer of the activated B cells (NF-κB) pathway in ANDRO treatment, indicating that ANDRO prevented the LPS-preserved degeneration of NP cells by inhibiting the NF-κB pathway. This study may provide a reference for clinic medication of IDD therapy.

Andrographolide protects chondrocytes from oxidative stress injury by activation of the Keap1-Nrf2-Are signaling pathway.

Recent studies have shown that andrographolide (AP) has the potential to be developed as a drug for therapy for osteoarthritis (OA). However, the role of AP in attenuating the progression of OA is still unknown. We hypothesized that its therapeutic effect may be associated with its antioxidant potential. In this study, we investigated the therapeutic effect of AP on chondrocytes injured by H2 O2 and the association with the oxidation-related signaling pathways through the detection of cell proliferation, cell viability, the expression of oxidative stress-specific genes (Sod1, Cat, and malonaldehyde [Mda]) and proteins (superoxide dismutase [SOD], catalase [CAT]) after a culture period of 3 and 5 days, respectively. Further exploration of the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) messenger RNA and protein was also performed. The results showed that 0.625 µg/ml and 2.5 µg/ml of AP decreased oxidative stress injury of chondrocytes by increasing cell proliferation reduced by H2 O2 and antioxidant enzyme activity, including SOD and CAT. Inflammation factors, such as matrix metallopeptidase 13 (Mmp13), tissue inhibitor of metalloproteinase 1 (Timp1), and interleukin-6 (Il6), were downregulated in the H2 O2 group with AP, demonstrating a decrease in the progression of OA. Pathway analyses identified that the kelch-like ECH-associated protein 1 (Keap1)-Nrf2-antioxidant response element (Are) pathway is an important mediator in AP therapy on H2 O2 -induced OA. This study indicates that AP exerts protection effects on oxidative stress via activation of the Keap1-Nrf2-Are pathway in chondrocytes injured by H2 O2 , which may be promising for the therapy of OA.