The receptor-interacting protein 1 (RIPK1)/RIPK3 kinases play important roles in necroptosis that is closely linked to inflammatory response. Although the activation of necroptosis is well characterized, how necroptosis is tuned down is largely unknown. Here, we found that Parkin (also known as PARK2 ), an E3 ubiquitin ligase implicated in Parkinson’s disease and a tumor suppressor, regulates necroptosis and inflammation by regulating necrosome formation. Parkin prevents the formation of the RIPK1-RIPK3 complex by promoting polyubiquitination of RIPK3. Parkin is phosphorylated and activated by the cellular energy sensor AMP-activated protein kinase (AMPK). Parkin-deficiency potentiates the RIPK1-RIPK3 interaction, RIPK3 phosphorylation, and necroptosis. Importantly, Parkin deficiency enhances inflammation and inflammation-associated tumorigenesis. These findings demonstrate that the AMPK-Parkin axis negatively regulates necroptosis via inhibiting the RIPK1-RIPK3 complex formation and this regulation may serve as an important mechanism to fine-tune necroptosis and inflammation.

The majority of periprosthetic joint infections occur shortly after primary joint replacement (<3 months) and require the removal of all implant components for the treatment period (~4 months). A clinically relevant animal model of periprosthetic infection should, therefore, establish an infection with implant components in place. Here, we describe a joint replacement model in the rat with ultrahigh molecular weight polyethylene (UHMWPE) and titanium components inoculated at the time of surgery by methicillin-sensitive Staphylococcus aureus (S. aureus), which is one of the main causative microorganisms of periprosthetic joint infections. We monitored the animals for 4 weeks by measuring gait, weight-bearing symmetry, von Frey testing, and micro-CT as our primary endpoint analyses. We also assessed the infection ex vivo using colony counts on the implant surfaces and histology of the surrounding tissues. The results confirmed the presence of a local infection for 4 weeks with osteolysis, loosening of the implants, and clinical infection indicators such as redness, swelling, and increased temperature. The utility of specific gait analysis parameters, especially temporal symmetry, hindlimb duty factor imbalance, and phase dispersion was identified in this model for assessing the longitudinal progression of the infection, and these metrics correlated with weight-bearing asymmetry. We propose to use this model to study the efficacy of using different local delivery regimens of antimicrobials on addressing periprosthetic joint infections. Statement of clinical significance: We have established a preclinical joint surgery model, in which postoperative recovery can be monitored over a multi-week course by assessing gait, weight-bearing, and allodynia. This model can be used to study the efficacy of different combinations of implant materials and medication regimens.

Nucleic acid-based therapeutics, including the use of messenger RNA (mRNA) as a drug molecule, has tremendous potential in the treatment of chronic diseases, such as age-related neurodegenerative diseases. In this study, we have developed a cationic liposomal formulation of mRNA and evaluated the potential of intranasal delivery to the brain in murine model. Preliminary in vitro studies in J774A.1 murine macrophages showed GFP expression up to 24 h and stably expressed GFP protein in the cytosol. Upon intranasal administration of GFP-mRNA/cationic liposomes (3 mg/kg dose) in mice, there was significantly higher GFP-mRNA expression in the brain post 24 h as compared to either naked mRNA or the vehicle-treated group. Luciferase mRNA encapsulated in cationic liposomes was used for quantification of mRNA expression distribution in the brain. The results showed increased luciferase activity in the whole brain in a dose-dependent manner. Specifically, the luciferase-mRNA/ cationic liposome group (3 mg/kg dose) showed significantly higher luciferase activity in the cortex, striatum, and midbrain regions as compared with the control groups, with minimal systemic exposure. Overall, the results of this study demonstrate the feasibility of brain-specific, nonviral mRNA delivery for the treatment of various neurological disorders.

No abstract

Tissue necrosis commonly accompanies the development of a wide range of serious diseases. Therefore, highly sensitive detection and precise boundary delineation of necrotic tissue via effective imaging techniques are crucial for clinical treatments; however, no imaging modalities have achieved satisfactory results to date. Although fluorescence molecular imaging (FMI) shows potential in this regard, no effective necrosis-avid fluorescent probe has been developed for clinical applications. Here, we demonstrate that indocyanine green (ICG) can achieve high avidity of necrotic tissue owing to its interaction with lipoprotein (LP) and phospholipids. The mechanism was explored at the cellular and molecular levels through a series of in vitro studies. Detection of necrotic tissue and real-time image-guided surgery were successfully achieved in different organs of different animal models with the help of FMI using in house-designed imaging devices. The results indicated that necrotic tissue with a 0.6 mm diameter could be effectively detected with precise boundary definition. We believe that the new discovery and the associated imaging techniques will improve personalized and precise surgery in the near future.

We investigated the antiwrinkle effects of cultured human fibroblasts and adipose-derived stem cells (ADSCs) and the mechanisms underlying the reduction of wrinkles in photoaged skin. The fibroblasts and ADSCs were isolated from human tissue and cultured. A total of 28 6-week-old female BALB/c nude mice were classified into four groups, including the normal control group and three groups that were irradiated six times a week for 6-weeks using ultraviolet B radiation to induce photoaged wrinkles. ADSCs were injected into the wrinkles in the skin of the second group and fibroblasts were injected into the wrinkles in the skin of the third group. The fourth group was the irradiated negative control group (no therapy). After 4 weeks of injections, the wrinkles were compared by replica analysis, biopsies were performed, and the dermal thickness and collagen densities were measured. We determined the amounts of type 1 collagen and matrix metalloproteinases (MMPs) 1, 2, 3, 9, and 13 using real-time polymerase chain reaction and Western blot analysis, and we assessed tropoelastin and fibrillin-1 expression in the dermis by immunohistochemistry. Replica analysis showed significant wrinkle reduction in the fibroblast group and the ADSC group. ADSCs stimulated collagen expression and decreased MMP expression. Although fibroblasts stimulated more collagen expression than ADSCs, they also increased MMP expression. Overall, the ADSC group showed higher collagen density and had better outcomes in the tropoelastin and fibrillin-1 assessments. Both cultured fibroblasts and ADSCs could play an important role in wrinkle reduction despite differences in their mechanisms of action.

A peripancreatic vascular reconstruction can reveal the vascular anatomy, variations of peripancreatic vascular, and tumor-induced vascular changes; the application of the simulation surgery platform could reduce surgical trauma and decrease operative time.

The proposed automatic approach achieves robust, accurate, and fast liver segmentation for 3D CTce datasets. The AdaBoost voxel classifier can detect liver area quickly without errors and provides sufficient liver shape information for model initialization. The AdaBoost profile classifier achieves sufficient accuracy and greatly decreases segmentation time. These results show that the proposed segmentation method achieves a level of accuracy comparable to that of state-of-the-art automatic methods based on ASM.