Intra-articular injection of an extended-release flavopiridol formulation represents a potential alternative to other intra-articular medications for treating equine joint disease.

Objective: To establish the pharmacokinetics of the cyclin-dependent kinase-9 inhibitor flavopiridol in equine middle carpal joints, using an extended-release poly lactic-co-glycolic acid (PLGA) microparticle formulation.

Animals: 4 healthy horses without evidence of forelimb lameness.

Methods: A 6-week longitudinal pharmacokinetic study was conducted in 2 phases (6 weeks each) in 4 healthy horses.

Current trends in the prevention of adhesions after zone 2 flexor tendon repair.

Treating flexor tendon injuries within the digital flexor sheath (commonly referred to as palmar hand zone 2) presents both technical and logistical challenges. Success hinges on striking a delicate balance between safeguarding the surgical repair for tendon healing and initiating early rehabilitation to mitigate the formation of tendon adhesions. Adhesions between tendon slips and between tendons and the flexor sheath impede tendon movement, leading to postoperative stiffness and functional impairment.

Biomimetic Bone-Like Composite Hydrogel Scaffolds Composed of Collagen Fibrils and Natural Hydroxyapatite for Promoting Bone Repair.

Bone is a complex organic-inorganic composite tissue composed of ∼30% organics and ∼70% hydroxyapatite (HAp). Inspired by this, we used 30% collagen and 70% HAp extracted from natural bone using the calcination method to generate a biomimetic bone composite hydrogel scaffold (BBCHS). In one respect, BBCHS, with a fixed proportion of inorganic and organic components similar to natural bone, exhibits good physical properties.

CircGNB1 drives osteoarthritis pathogenesis by inducing oxidative stress in chondrocytes.

Background: Circular RNAs (circRNAs) have risen to prominence as important regulators of biological processes. This study investigated whether circGNB1 functions as a competitive endogenous RNA to regulate the pathological process of oxidative stress in age-related osteoarthritis (OA).

Methods: The relationship between circGNB1 expression and oxidative stress/OA severity was determined in cartilages from OA patients at different ages.

Mechanical Cues for Triggering and Regulating Cellular Movement Selectively at the Single-Cell Level.

Cell motility plays important roles in many biophysical and physiological processes ranging from in vitro biomechanics, wound healing, to cancer metastasis. This work introduces a new means to trigger and regulate motility individually using transient mechanical stimulus applied to designated cells. Using BV2 microglial cells, our investigations indicate that motility can be reproducibly and reliably initiated using mechanical compression of the cells.

A two-stage digestion of whole murine knee joints for single-cell RNA sequencing.

Objective: Single-cell RNA sequencing (scRNA-seq) is a powerful technology that can be applied to the cells populating the whole knee in the study of joint pathology. The knee contains cells embedded in hard structural tissues, cells in softer tissues and membranes, and immune cells. This creates a technical challenge in preparing a viable and representative cell suspension suitable for use in scRNA-seq in minimal time, where under-digestion may exclude cells in hard tissues, over-digestion may damage soft tissue cells, and prolonged digestion may induce phenotypic drift.

Production of Inhalable Ultra-Small Particles for Delivery of Anti-Inflammation Medicine via a Table-Top Microdevice.

A table-top microdevice was introduced in this work to produce ultrasmall particles for drug delivery via inhalation. The design and operation are similar to that of spray-drying equipment used in industry, but the device itself is much smaller and more portable in size, simpler to operate and more economical. More importantly, the device enables more accurate control over particle size.

Intra-articular injection of flavopiridol-loaded microparticles for treatment of post-traumatic osteoarthritis.

Rapid joint clearance of small molecule drugs is the major limitation of current clinical approaches to osteoarthritis and its subtypes, including post-traumatic osteoarthritis (PTOA). Particulate systems such as nano/microtechnology could provide a potential avenue for improved joint retention of small molecule drugs. One drug of interest for PTOA treatment is flavopiridol, which inhibits cyclin-dependent kinase 9 (CDK9).

CircSLC7A2 protects against osteoarthritis through inhibition of the miR-4498/TIMP3 axis.

Objectives: Circular RNAs (circRNAs) are noncoding RNAs that compete against other endogenous RNA species, such as microRNAs, and have been implicated in many diseases. In this study, we investigated the role of a new circRNA (circSLC7A2) in osteoarthritis (OA).

Materials And Methods: The relative expression of circSLC7A2 was significantly lower in OA tissues than it was in matched controls, as shown by real-time quantitative polymerase chain reaction (RT-qPCR).

New Means to Control Molecular Assembly.

While self-assembly of molecules is relatively well-known and frequently utilized in chemical synthesis and material science, controlled assembly of molecules represents a new concept and approach. The present work demonstrates the concept of controlled molecular assembly using a non-spherical biomolecule, heparosan tetrasaccharide (MW = 1.099 kD).

Direct Observations of Silver Nanowire-Induced Frustrated Phagocytosis among NR8383 Lung Alveolar Macrophages.

The interaction of long nanowires and living cells is directly related to nanowires' nanotoxicity and health impacts. Interactions of silver nanowires (AgNWs) and macrophage cell lines (NR8383) were investigated using laser scanning confocal microscopy and single cell compression (SCC). With high-resolution imaging and mechanics measurement of individual cells, AgNW-induced frustrated phagocytosis was clearly captured in conjunction with structural and property changes of cells.

Direct Visualization of the Binding of Transforming Growth Factor Beta 1 with Cartilage Oligomeric Matrix Protein via High-Resolution Atomic Force Microscopy.

This work reports the first direct observations of binding and complex formation between transforming growth factor beta 1 (TGF-β1) and cartilage oligomeric matrix protein (COMP) using high-resolution atomic force microscopy (AFM). Each COMP molecule consists of pentamers whose five identical monomeric units bundle at N-termini. From this central point, the five monomers' flexible arms extend outward with C-terminal domains at the distal ends, forming a bouquet-like structure.

Cyclin-Dependent Kinase 9 (CDK9) Inhibitor Atuveciclib Suppresses Intervertebral Disk Degeneration via the Inhibition of the NF-κB Signaling Pathway.

Intervertebral disk degeneration (IVDD) is a spinal disk condition caused by an inflammatory response induced by various proinflammatory cytokines, such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α. cyclin-dependent kinase 9 (CDK9) is a transcriptional regulator and potential therapeutic target for many diseases, especially in regulating the activation of primary inflammatory response genes. Our study investigated a highly selective CDK9 inhibitor, atuveciclib, which protects nucleus pulposus (NP) cells from proinflammatory stimuli-induced catabolism.

Aggrecan and COMP Improve Periosteal Chondrogenesis by Delaying Chondrocyte Hypertrophic Maturation.

The generation of cartilage from progenitor cells for the purpose of cartilage repair is often hampered by hypertrophic differentiation of the engineered cartilaginous tissue caused by endochondral ossification. Since a healthy cartilage matrix contains high amounts of Aggrecan and COMP, we hypothesized that their supplementation in the biogel used in the generation of subperiosteal cartilage mimics the composition of the cartilage extracellular matrix environment, with beneficial properties for the engineered cartilage. Supplementation of COMP or Aggrecan was studied during chondrogenic differentiation of rabbit periosteum cells and periosteum-derived chondrocytes.

NADPH oxidases in bone and cartilage homeostasis and disease: A promising therapeutic target.

Reactive oxygen species (ROS) generated by the NADPH oxidase (Nox) enzymes are important short-range signaling molecules. They have been extensively studied in the physiology and pathophysiology of the cardiovascular system, where they have important roles in vascular inflammation, angiogenesis, hypertension, cardiac injury, stroke, and aging. Increasing evidence demonstrates that ROS and Nox enzymes also affect bone homeostasis and osteoporosis, and more recent studies implicate ROS and Nox enzymes in both inflammatory arthritis and osteoarthritis.

Acute Changes in NADPH Oxidase 4 in Early Post-Traumatic Osteoarthritis.

Knee injuries cause structural damage and acute inflammation that initiates the development of post-traumatic osteoarthritis (PTOA). NADPH oxidase 4 (Nox4), a member of a family of enzymes that generates reactive oxygen species (ROS), plays a pivotal role in normal development of the musculoskeletal system, but may increase ROS production to harmful levels after joint injury. The role of ROS in both normal joint homeostasis and injury is poorly understood, but inhibition of excessive ROS production by Nox4 after joint injury could be protective to the joint, decreasing oxidative stress, and initiation of PTOA.

Label-Free and Direct Visualization of Multivalent Binding of Bone Morphogenetic Protein-2 with Cartilage Oligomeric Matrix Protein.

This work presents the first direct evidence of multivalent binding between bone morphogenetic protein-2 (BMP-2) and cartilage oligomeric matrix protein (COMP) using high-resolution atomic force microscopy (AFM) imaging. AFM topographic images reveal the molecular morphology of COMP, a pentameric protein whose five identical monomer units bundle together at N-termini, extending out with flexible chains to C-termini. Upon addition of BMP-2, COMP molecules undergo conformational changes at the C-termini to enable binding with BMP-2 molecules.

Effects of Micronized Cartilage Matrix on Cartilage Repair in Osteochondral Lesions of the Talus.

Background: The repair of osteochondral lesions remains a challenge due to its poor vascularity and limited healing potential. Micronized cartilage matrix (MCM) is dehydrated, decellularized, micronized allogeneic cartilage matrix that contains the components of native articular tissue and is hypothesized to serve as a scaffold for the formation of hyaline-like tissue. Our objective was to demonstrate that the use of MCM combined with mesenchymal stem cells (MSCs) can lead to the formation of hyaline-like cartilage tissue in a single-stage treatment model.

Flavopiridol Protects Bone Tissue by Attenuating RANKL Induced Osteoclast Formation.

Bone resorption and homeostasis is carried out by osteoclasts, whose differentiation and activity are regulated by the RANK/RANKL axis. Our previous studies using a mouse model of joint injury show that joint trauma induces local inflammation followed by bone remodeling. The transcription factor cyclin-dependent kinase 9 (CDK9) is the major regulator of inflammation, as CDK9 inhibitor flavopiridol effectively suppress injury-induced inflammatory response.

Ca-Dependent Regulation of NFATc1 via KCa3.1 in Inflammatory Osteoclastogenesis.

In inflammatory arthritis, the dysregulation of osteoclast activity by proinflammatory cytokines, including TNF, interferes with bone remodeling during inflammation through Ca-dependent mechanisms causing pathological bone loss. Ca-dependent CREB/c-fos activation via Ca-calmodulin kinase IV (CaMKIV) induces transcriptional regulation of osteoclast-specific genes via NFATc1, which facilitate bone resorption. In leukocytes, Ca regulation of NFAT-dependent gene expression oftentimes involves the activity of the Ca-activated K channel KCa3.

Stem Cells in Spinal Fusion.

Study Design: Review of literature.

Objectives: This review of literature investigates the application of mesenchymal stem cells (MSCs) in spinal fusion, highlights potential uses in the development of bone grafts, and discusses limitations based on both preclinical and clinical models.

Methods: A review of literature was conducted looking at current studies using stem cells for augmentation of spinal fusion in both animal and human models.

Binding to COMP Reduces the BMP2 Dose for Spinal Fusion in a Rat Model.

Study Design: The aim of this study is to test the effect of cartilage oligomeric matrix protein (COMP) on enhancing rhBMP-2 induced spinal fusion in a prospective 8-week interventional trial of spinal fusion in rats.

Objective: To determine whether the amount of bone morphogenetic protein-2 (BMP-2) required to achieve spinal fusion in a pre-clinical model can be reduced by the addition of COMP.

Summary Of Background Data: BMPs are applied clinically at supraphysiological doses to promote spinal fusion by inducing osseous growth, but dose-related limitations include ectopic bone formation and local inflammatory reactions.

Articular Cartilage Injury and Potential Remedies.

Osteoarthritis affects millions of people worldwide, is associated with joint stiffness and pain, and often causes significant disability and loss of productivity. Osteoarthritis is believed to occur as a result of ordinary "wear and tear" on joints during the course of normal activities of daily living. Posttraumatic osteoarthritis is a particular subset of osteoarthritis that occurs after a joint injury.

Effect of alendronate on post-traumatic osteoarthritis induced by anterior cruciate ligament rupture in mice.

Introduction: Previous studies in animal models of osteoarthritis suggest that alendronate (ALN) has antiresorptive and chondroprotective effects, and can reduce osteophyte formation. However, these studies used non-physiologic injury methods, and did not investigate early time points during which bone is rapidly remodeled prior to cartilage degeneration. The current study utilized a non-invasive model of knee injury in mice to investigate the effect of ALN treatment on subchondral bone changes, articular cartilage degeneration, and osteophyte formation following injury.