Liver-Inspired Polyetherketoneketone Scaffolds Simulate Regenerative Signals and Mobilize Anti-Inflammatory Reserves to Reprogram Macrophage Metabolism for Boosted Osteoporotic Osseointegration

A bioactive Cu-grafted gel coating with micro-nano structures for simultaneous enhancement of bone regeneration and infection resistance

Prosthetic joint infection (PJI) remains a significant challenge in clinical applications. It not only impedes the recovery of bone tissue at the site of bone defect but also leads to multiple debridements, long-lasting antibiotic treatment and even secondary replacement. Titanium alloy Ti6Al4V (TC4) is widely used in orthopedic implants due to its excellent mechanical properties and biocompatibility; however, it lacks inherent antibacterial and osteoinductive functions. In this study, a composite coating based on polyvinyl alcohol (PVA) with tissue repair and antibacterial properties was applied on the surface of TC4. A PVA gel coating functionalized with terpyridine and catechol groups (PVA-TP-CA) was synthesized and subsequently complexed with copper (Cu) ions. The differential binding affinities of TP and CA groups to Cu enabled a sustained and controlled release of metal ions. Furthermore, a micro-nano surface structure was fabricated on TC4 using femtosecond laser technology to achieve a micro-nano structure interface and enhanced bonding strength. Biological evaluations demonstrated that the modified surface significantly improved the antibacterial, angiogenic, and osteogenic properties of TC4. These findings indicate that this multifunctional composite coating holds great promise for surface modification of orthopedic implants, offering an effective strategy for preventing PJI while promoting bone regeneration.

Microfluidic cell unroofing for the in situ molecular analysis of organelles without membrane permeabilization

Molecular networks of organelle membranes are involved in many cell processes. However, the nature of plasma membrane as a barrier to various analytical tools, including antibodies, makes it challenging to examine intact organelle membranes without affecting their structure and functions via membrane permeabilization. Therefore, in this study, we aimed to develop a microfluidic method to unroof cells and observe the intrinsic membrane molecules in organelles. In our method, single cells were precisely arrayed on the bottom surface of microchannels in a light-guided manner using a photoactivatable cell-anchoring material. At sufficiently short cell intervals, horizontal stresses generated by the laminar flow instantly fractured the upper cell membranes, without significantly affecting some organelles inside the fractured cells. Subsequently, nucleus and other organelles in unroofed cells were observed via confocal fluorescence and scanning electron microscopy. Furthermore, distribution of the mitochondrial membrane protein, translocase of outer mitochondrial membrane 20, on the mitochondrial membrane was successfully observed via immunostaining without permeabilization. Overall, the established cell unroofing method shows great potential to examine the localization, functions, and affinities of proteins on intact organelle membranes.

Enhanced Immune Modulation and Bone Tissue Regeneration through an Intelligent Magnetic Scaffold Targeting Macrophage Mitochondria

During the bone tissue repair process, the highly dynamic interactions between the host and materials hinder precise, stable, and sustained immune modulation. Regulating the immune response based on potential mechanisms of macrophage phenotypic changes may represent an effective strategy for promoting bone healing. This study successfully constructs a co-dispersed pFe₃O₄-MXene nanosystem by loading positively charged magnetite (pFe₃O₄) nanoparticles onto MXene nanosheets using electrostatic self-assembly. Subsequently, this work fabricates a biomimetic porous bone scaffold (PFM) via selective laser sintering, which exhibit superior magnetic properties, mechanical performance, hydrophilicity, and biocompatibility. Further investigations demonstrate that the PFM scaffold could precisely and remotely modulate macrophage polarization toward the M2 phenotype under a static magnetic field, significantly enhancing osteogenesis and angiogenesis. Proteomic analysis reveal that the scaffold upregulates Arg2 expression, enhancing mitochondrial function and accelerating oxidative phosphorylation, thereby inducing the M2 transition. In vivo experiments validated the scaffold's immune regulatory capacity in subcutaneous and cranial defect repairs in rats, effectively promoting new bone formation. Overall, this strategy of immune modulation targeting macrophage metabolism and mitochondrial function offers novel insights for material design in tissue engineering and regenerative medicine.

Microneedles Loaded with Nitric-Oxide Driven Nanomotors Improve Force-Induced Efferocytosis Impairment and Sterile Inflammation by Revitalizing Macrophage Energy Metabolism

Mechanical force initiates sterile inflammation, a process implicated in diverse physiological and pathological processes. The timely clearance of apoptotic cells by macrophages via efferocytosis is crucial for the proper resolution of sterile inflammation and for averting excessive tissue damage. Despite this, the specific role and underlying mechanisms of mechanical force on macrophage efferocytosis remain obscure. By integrating bioinformatics and metabolomics analyses, we uncovered how mechanical force disrupts the "arginine metabolism─TCA cycle─mitochondrial function" metabolic cascade, thereby impairing macrophage efferocytosis and intensifying sterile inflammation. Notably, we discovered that elevating l-arginine levels can ameliorate these crises by restoring energy metabolism. Leveraging this insight, we engineered a microneedle drug delivery system loaded with nitric-oxide driven nanomotors (MSN-LA@MNs) for targeted delivery of l-arginine. The active component, MSN-LA, exploits the heightened expression of inducible nitric oxide synthase (iNOS) in force-loaded tissues as a chemoattractant, harnessing NO generated from iNOS-catalyzed l-arginine for autonomous propulsion. In a force-induced rat orthodontic tooth movement (OTM) model, we confirmed that MSN-LA@MNs enhance macrophage efferocytosis and, under iNOS guidance, dynamically modulate sterile inflammation levels in OTM, thus facilitating the OTM process. Collectively, our findings elucidate previously unclear mechanistic links between force, macrophage efferocytosis, and sterile inflammation from a metabolic vantage point, offering a promising targeted strategy for modulating force-related biological processes such as OTM.

Chirality-Induced Hydroxyapatite Manipulates Enantioselective Bone-Implant Interactions Toward Ameliorative Osteoporotic Osseointegration

Inspired by the fundamental attribute of chirality in nature, chiral-engineered biomaterials now represent a groundbreaking frontier in biomedical fields. However, the integration of chirality within inorganic materials remains a critical challenge and developments of chirality-induced bionic bone implants are still in infancy. In this view, novel chiral hydroxyapatite (CHA) coated Ti alloys are successfully synthesized by a sophisticated chiral molecule-induced self-assembly method for the first time. The obtained samples are characterized by stereospecific L-/D-/Rac-chiral hierarchical morphology, nanotopography rough surfaces, improved hydrophilicity, and bioactivity. Following implantation into rat femoral condyle defects, the distinct stereospecific chiral hierarchical structures exhibit highly enantioselective bone-implants interactions, wherein the left-handed chirality of L-CHA strongly promotes osteoporotic osseointegration and vice versa for right-handed chirality of D-CHA. Consistently, in vitro assays further validate the superior enantiomer-dependent osteoporotic osseointegration ability of L-CHA, mainly by manipulating desired immunomodulation coupled with enhanced neurogenesis, angiogenesis, and osteogenesis. Moreover, as analyzed by transcriptomic RNA-seq, a new discovery of down-regulated IL-17 signaling pathway is considered predominately responsible for the desired immunomodulation ability of L-CHA. These results provide new insights into biological multifunctionality and mechanism underlying L-chirality's roles for bone healing, thus may inspiring developments of new generation of chiral biomaterials.

Nanomaterial-Based Repurposing of Macrophage Metabolism and Its Applications

Macrophage immunotherapy represents an emerging therapeutic approach aimed at modulating the immune response to alleviate disease symptoms. Nanomaterials (NMs) have been engineered to monitor macrophage metabolism, enabling the evaluation of disease progression and the replication of intricate physiological signal patterns. They achieve this either directly or by delivering regulatory signals, thereby mapping phenotype to effector functions through metabolic repurposing to customize macrophage fate for therapy. However, a comprehensive summary regarding NM-mediated macrophage visualization and coordinated metabolic rewiring to maintain phenotypic equilibrium is currently lacking. This review aims to address this gap by outlining recent advancements in NM-based metabolic immunotherapy. We initially explore the relationship between metabolism, polarization, and disease, before delving into recent NM innovations that visualize macrophage activity to elucidate disease onset and fine-tune its fate through metabolic remodeling for macrophage-centered immunotherapy. Finally, we discuss the prospects and challenges of NM-mediated metabolic immunotherapy, aiming to accelerate clinical translation. We anticipate that this review will serve as a valuable reference for researchers seeking to leverage novel metabolic intervention-matched immunomodulators in macrophages or other fields of immune engineering.

Research progresses on mitochondrial-targeted biomaterials for bone defect repair

In recent years, the regulation of the cell microenvironment has opened up new avenues for bone defect repair. Researchers have developed novel biomaterials to influence the behavior of osteoblasts and immune cells by regulating the microenvironment, aiming to achieve efficient bone repair. Mitochondria, as crucial organelles involved in energy conversion, biosynthesis and signal transduction, play a vital role in maintaining bone integrity. Dysfunction of mitochondria can have detrimental effects on the transformation of the immune microenvironment and the differentiation of stem cells, thereby hindering bone tissue regeneration. Consequently, targeted therapy strategies focusing on mitochondria have emerged. This approach offers a wide range of applications and reliable therapeutic effects, thereby providing a new treatment option for complex and refractory bone defect diseases. In recent studies, more biomaterials have been used to restore mitochondrial function and promote positive cell differentiation. The main directions are mitochondrial energy metabolism, mitochondrial biogenesis and mitochondrial quality control. In this review, we investigated the biomaterials used for mitochondria-targeted treatment of bone defect repair in recent years from the perspective of progress and strategies. We also summarized the micro-molecular mechanisms affected by them. Through discussions on energy metabolism, oxidative stress regulation and autophagy regulation, we emphasized the opportunities and challenges faced by mitochondria-targeted biomaterials, providing vital clues for developing a new generation of bone repair materials.

SIRT3 regulates cardiolipin biosynthesis in pressure overload-induced cardiac remodeling by PPARγ-mediated mechanism

Cardiac remodeling is the primary pathological feature of chronic heart failure (HF). Exploring the characteristics of cardiac remodeling in the very early stages of HF and identifying targets for intervention are essential for discovering novel mechanisms and therapeutic strategies. Silent mating type information regulation 2 homolog 3 (SIRT3), as a major mitochondrial nicotinamide adenine dinucleotide (NAD)-dependent deacetylase, is required for mitochondrial metabolism. However, whether SIRT3 plays a role in cardiac remodeling by regulating the biosynthesis of mitochondrial cardiolipin (CL) is unknown. In this study, we induced pressure overload in wild-type (WT) and SIRT3 knockout (SIRT3-/-) mice via transverse aortic constriction (TAC). Compared with WT mouse hearts, the hearts of SIRT3-/- mice exhibited more-pronounced cardiac remodeling and fibrosis, greater reactive oxygen species (ROS) production, decreased mitochondrial-membrane potential (ΔΨm), and abnormal mitochondrial morphology after TAC. Furthermore, SIRT3 deletion aggravated TAC-induced decrease in total CL content, which might be associated with the downregulation of the CL synthesis related enzymes cardiolipin synthase 1 (CRLS1) and phospholipid-lysophospholipid transacylase (TAFAZZIN). In our in vitro experiments, SIRT3 overexpression prevented angiotensin II (AngII)- induced aberrant mitochondrial function, CL biosynthesis disorder, and peroxisome proliferator-activated receptor gamma (PPARγ) downregulation in cardiomyocytes; meanwhile, SIRT3 knockdown exacerbated these effects. Moreover, the addition of GW9662, a PPARγ antagonist, partially counteracted the beneficial effects of SIRT3 overexpression. In conclusion, SIRT3 regulated PPARγ-mediated CL biosynthesis, maintained the structure and function of mitochondria, and thereby protected the myocardium against cardiac remodeling.