VEGF couples hypertrophic cartilage remodeling, ossification and angiogenesis during endochondral bone formation

Proliferative and Osteogenic Supportive Effect of VEGF-Loaded Collagen-Chitosan Hydrogel System in Bone Marrow Derived Mesenchymal Stem Cells

The use of hydrogel (HG) in regenerative medicine is an emerging field and thus several approaches have been proposed recently to find an appropriate hydrogel system. In this sense, this study developed a novel HG system using collagen, chitosan, and VEGF composites for culturing mesenchymal stem cells (MSCs), and investigated their ability for osteogenic differentiation and mineral deposition. Our results showed that the HG loaded with 100 ng/mL VEGF (HG-100) significantly supported the proliferation of undifferentiated MSCs, the fibrillary filament structure (HE stain), mineralization (alizarin red S and von Kossa stain), alkaline phosphatase, and the osteogenesis of differentiated MSCs compared to other hydrogels (loaded with 25 and 50 ng/mL VEGF) and control (without hydrogel). HG-100 showed a higher VEGF releasing rate from day 3 to day 7 than other HGs, which substantially supports the proliferative and osteogenic properties of HG-100. However, the HGs did not increase the cell growth in differentiated MSCs on days 14 and 21 due to the confluence state (reach stationary phase) and cell loading ability, regardless of the VEGF content. Similarly, the HGs alone did not stimulate the osteogenesis of MSCs; however, they increased the osteogenic ability of MSCs in presence of osteogenic supplements. Accordingly, a fabricated HG with VEGF could be used as an appropriate system to culture stem cells for bone and dental regeneration.

New insights into the properties, functions, and aging of skeletal stem cells

Bone-related diseases pose a major health burden for modern society. Bone is one of the organs that rely on stem cell function to maintain tissue homeostasis. Stem cell therapy has emerged as an effective new strategy to repair and replace damaged tissue. Although research on bone marrow mesenchymal stem cells has been conducted over the last few decades, the identity and definition of the true skeletal stem cell population remains controversial. Due to technological advances, some progress has been made in the prospective separation and function research of purified skeletal stem cells. Here, we reviewed the recent progress of highly purified skeletal stem cells, their function in bone development and repair, and the impact of aging on skeletal stem cells. Various studies on animal and human models distinguished and isolated skeletal stem cells using different surface markers based on flow-cytometry-activated cell sorting. The roles of different types of skeletal stem cells in bone growth, remodeling, and repair are gradually becoming clear. Thanks to technological advances, SSCs can be specifically identified and purified for functional testing and molecular analysis. The basic features of SSCs and their roles in bone development and repair and the effects of aging on SSCs are gradually being elucidated. Future mechanistic studies can help to develop new therapeutic interventions to improve various types of skeletal diseases and enhance the regenerative potential of SSCs.

What is the Effect of Bevacizumab on Cartilage and Synovium in a Rabbit Model of Hemophilic Arthropathy?

BACKGROUND

Hemophilic arthropathy can cause recurrent hemarthroses and severe damage to the synovium and articular cartilage. Previous studies have shown that vascular endothelial growth factor (VEGF) plays an essential role in neoangiogenesis. Bevacizumab, a monoclonal VEGF inhibitor, is used clinically to prevent angiogenesis. However, its effects on hemophilic arthropathy are unknown.

QUESTIONS/PURPOSES

Using a hemophilic arthropathy rabbit model, we asked: Does an intra-articular injection of bevacizumab (1) inhibit VEGF, (2) decrease signal intensity in dynamic contrast-enhanced MRI (DCE-MRI) as an assessment of capillary permeability and neoangiogenesis, (3) reduce cartilage damage, (4) reduce synovial changes, and (5) affect macroscopic changes during the development of hemophilic arthropathy?

METHODS

Twenty-five male New Zealand rabbits were divided into four groups. Eight knees from four rabbits were used as the control group. We used an established animal model for hemophilic arthropathy in the remaining 21 rabbits. Animals were assigned randomly to three groups with seven rabbits in each group. One group was used to establish mild arthropathy, and the other two were used to establish severe arthropathy. Autologous blood from the rabbits' ears was injected into the right and left knees twice per week for 8 weeks to represent mild arthropathy and for 16 weeks to represent severe arthropathy. In the mild arthropathy group, bevacizumab was injected into the right knee once every 2 weeks. Bevacizumab was injected into the right knee of rabbits in one of the severe arthropathy groups once every 2 weeks for 16 weeks, and intra-articular bevacizumab injections were administered to the right knees of rabbits in the other severe arthropathy group once every 2 weeks after the eighth week. An equal volume of 0.9% saline was injected into the left knee of rabbits in all arthropathy groups. To explore the efficacy of bevacizumab, joint diameters were quantitatively measured, and cartilage and synovial changes were examined. Degeneration of articular cartilage was evaluated with the semiquantitative Osteoarthritis Research Society International grading system. Synovial damage was analyzed with a semiquantitative microscopic scoring system. In addition, we evaluated perfusion and angiogenesis using DCE-MRI (quantitative signal intensity changes). Immunohistochemical testing was used to measure VEGF levels (analyzed by Western blotting).

RESULTS

Intra-articular bevacizumab treatment inhibited VEGF in our rabbit model of hemophilic arthropathy. VEGF protein expression levels were lower in the mild arthropathy group that received intra-articular bevacizumab (0.89 ± 0.45) than the mild arthropathy control group (1.41 ± 0.61) (mean difference -0.52 [95% CI -0.898 to -0.143]; p = 0.02). VEGF levels were lower in the severe arthropathy group that received treatment for 16 weeks (0.94 ± 0.27) than in the control knees (1.49 ± 0.36) (mean difference -0.55 [95% CI -0.935 to -0.161]; p = 0.01). In the severe arthropathy group, the Osteoarthritis Research Society International score indicating cartilage damage was lower in the group that received intra-articular bevacizumab treatment from the beginning than in the control group (median 17 [range 13 to 18] versus 18 [range 17 to 20]; difference of medians 1; p = 0.02). Additionally, the scores indicated synovial damage was lower in the group that received intra-articular bevacizumab treatment from the beginning than the control group (median 5 [range 4 to 9] versus 9 [range 8 to 12]; difference of medians 4; p = 0.02). The mean of mean values for signal intensity changes was higher in the nontreated severe groups than in the group of healthy knees. The signal intensity changes were higher in the severe arthropathy control groups (Groups BC and CC) (median 311.6 [range 301.4 to 361.2] and 315.1 [range 269.7 to 460.4]) than in the mild arthropathy control group (Group AC) (median 234.1 [range 212.5 to 304.2]; difference of medians 77.5 and 81, respectively; p = 0.02 and p = 0.04, respectively). In the severe arthropathy group, discoloration caused by hemosiderin deposition in the cartilage and synovium was more pronounced than in the mild arthropathy group. In the severe arthropathy group treated with intra-articular bevacizumab, joint diameters were smaller than in the control group (Group BT median 12.7 mm [range 12.3 to 14.0] versus Group BC median 14.0 mm [range 13.1 to 14.5]; difference of medians 1.3 mm; p = 0.02).

CONCLUSION

Hemarthrosis damages the synovial tissues and cartilage in the knees of rabbits, regardless of whether they are treated with intra-articular bevacizumab. However, intra-articular injection of bevacizumab may reduce cartilage and synovial damage in rabbits when treatment is initiated early during the development of hemophilic arthropathy.

CLINICAL RELEVANCE

If the findings in this study are replicated in larger-animal models that consider the limitations of our work, then a trial in humans might be appropriate to ascertain whether intra-articular injection of bevacizumab could reduce cartilage damage and synovial changes in patients with hemophilia whose hemarthroses cannot otherwise be controlled.

Hypoxia-Inducible Factor-2α Signaling in the Skeletal System

Hypoxia-inducible factors (HIFs) are oxygen-dependent heterodimeric transcription factors that mediate molecular responses to reductions in cellular oxygen (hypoxia). HIF signaling involves stable HIF-β subunits and labile, oxygen-sensitive HIF-α subunits. Under hypoxic conditions, the HIF-α subunit is stabilized, complexes with nucleus-confined HIF-β subunit, and transcriptionally regulates hypoxia-adaptive genes. Transcriptional responses to hypoxia include altered energy metabolism, angiogenesis, erythropoiesis, and cell fate. Three isoforms of HIF-α-HIF-1α, HIF-2α, and HIF-3α-are found in diverse cell types. HIF-1α and HIF-2α serve as transcriptional activators, whereas HIF-3α restricts HIF-1α and HIF-2α. The structure and isoform-specific functions of HIF-1α in mediating molecular responses to hypoxia are well established across a wide range of cell and tissue types. The contributions of HIF-2α to hypoxic adaptation are often unconsidered if not outrightly attributed to HIF-1α. This review establishes what is currently known about the diverse roles of HIF-2α in mediating the hypoxic response in skeletal tissues, with specific focus on development and maintenance of skeletal fitness. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Bone tissue engineering for treating osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a devastating and complicated disease with an unclear etiology. Femoral head-preserving surgeries have been devoted to delaying and hindering the collapse of the femoral head since their introduction in the last century. However, the isolated femoral head-preserving surgeries cannot prevent the natural progression of ONFH, and the combination of autogenous or allogeneic bone grafting often leads to many undesired complications. To tackle this dilemma, bone tissue engineering has been widely developed to compensate for the deficiencies of these surgeries. During the last decades, great progress has been made in ingenious bone tissue engineering for ONFH treatment. Herein, we comprehensively summarize the state-of-the-art progress made in bone tissue engineering for ONFH treatment. The definition, classification, etiology, diagnosis, and current treatments of ONFH are first described. Then, the recent progress in the development of various bone-repairing biomaterials, including bioceramics, natural polymers, synthetic polymers, and metals, for treating ONFH is presented. Thereafter, regenerative therapies for ONFH treatment are also discussed. Finally, we give some personal insights on the current challenges of these therapeutic strategies in the clinic and the future development of bone tissue engineering for ONFH treatment.

An intelligent phase transformation system based on lyotropic liquid crystals for sequential biomolecule delivery to enhance bone regeneration

Endogenous repair of critical bone defects is typically hampered by inadequate vascularization in the early stages and insufficient bone regeneration later on. Therefore, drug delivery systems with the ability to couple angiogenesis and osteogenesis in a spatiotemporal manner are highly desirable for vascularized bone formation. Herein, we devoted to develop a liquid crystal formulation system (LCFS) attaining a controlled temporal release of angiogenic and osteoinductive bioactive molecules that could orchestrate the coupling of angiogenesis and osteogenesis in an optimal way. It has been demonstrated that the release kinetics of biomolecules depend on the hydrophobicity of the loaded molecules, making the delivery profile programmable and controllable. The hydrophilic deferoxamine (DFO) could be released rapidly within 5 days to activate angiogenic signaling, while the lipophilic simvastatin (SIM) showed a slow and sustained release for continuous osteogenic induction. Apart from its good biocompatibility with mesenchymal stem cells derived from rat bone marrow (rBMSCs), the DFO/SIM loaded LCFS could stimulate the formation of a vascular morphology in human umbilical vein endothelial cells (HUVECs) and the osteogenic differentiation of rBMSCs in vitro. The in vivo rat femoral defect models have witnessed the prominent angiogenic and osteogenic effects induced by the sequential presentation of DFO and SIM. This study suggests that the sequential release of DFO and SIM from the LCFS results in enhanced bone formation, offering a facile and viable treatment option for bone defects by mimicking the physiological process of bone regeneration.

Effects of temperature on metamorphosis and endochondral ossification in Rana chensinensis tadpoles

Temperature is one of the important factors affecting the growth, development, and metamorphosis of amphibians. Endochondral ossification during metamorphosis plays a crucial role in amphibian survival and adaptation on land. In this study, we explored the effects of different temperature treatments on the growth, development, and endochondral ossification of Rana chensinensis tadpoles during metamorphosis. The results showed that high temperature exposure may affect the skeletal development of tadpoles during metamorphosis, such as reduction of bone length and ossification of limbs, thyroid gland damage and change of ossification-related genes expression levels，and ultimately affect the movement and survival of tadpoles in the terrestrial environment. These results provide an experimental reference for further research on the effects of temperature on amphibian growth and development and provide an important theoretical basis for the decline of the amphibian population caused by temperature.

Histological Assessment of Endochondral Ossification and Bone Mineralization

Finely tuned cartilage mineralization, endochondral ossification, and normal bone formation are necessary for normal bone growth. Hypertrophic chondrocytes in the epiphyseal cartilage secrete matrix vesicles, which are small extracellular vesicles initiating mineralization, into the intercolumnar septa but not the transverse partitions of the cartilage columns. Bone-specific blood vessels invade the unmineralized transverse septum, exposing the mineralized cartilage cores. Many osteoblast precursors migrate to the cartilage cores, where they synthesize abundant bone matrices, and mineralize them in a process of matrix vesicle-mediated bone mineralization. Matrix vesicle-mediated mineralization concentrates calcium (Ca) and inorganic phosphates (Pi), which are converted into hydroxyapatite crystals. These crystals grow radially and are eventually get out of the vesicles to form spherical mineralized nodules, leading to collagen mineralization. The influx of Ca and Pi into the matrix vesicle is regulated by several enzymes and transporters such as TNAP, ENPP1, PiT1, PHOSPHO1, annexins, and others. Such matrix vesicle-mediated mineralization is regulated by osteoblastic activities, synchronizing the synthesis of organic bone material. However, osteocytes reportedly regulate peripheral mineralization, e.g., osteocytic osteolysis. The interplay between cartilage mineralization and vascular invasion during endochondral ossification, as well as that of osteoblasts and osteocytes for normal mineralization, appears to be crucial for normal bone growth.

Tongluo Shenggu capsule promotes angiogenesis to ameliorate glucocorticoid-induced femoral head necrosis via upregulating VEGF signaling pathway

BACKGROUND

Tongluo Shenggu Capsule (TLSGC) is a product of Traditional Chinese patent medicine that has been effective in glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) clinically for many years. It is made from water extracts of a well-used herbal and dietary supplement-pigeon pea leaves. Nevertheless, the material basis and pharmacological mechanisms of TLSGC ameliorating GIONFH needed to be better defined.

PURPOSE

To investigate the material basis and pharmacological mechanisms of TLSGC to ameliorate GIONFH.

METHODS

The chemical compositions in TLSGC were characterized using the LC-MS system. Based on integrating the relevant targets of TLSGC in MedChem Studio software and GIONFH-related genes in our previous work, a "drug targets-disease genes" interaction network was constructed. The candidate targets of TLSGC ameliorating GIONFH were filtrated by topological characteristic parameters and further experimental validated based on methylprednisolone-induced rat model and dexamethasone-inhibited human umbilical vein endothelial cells (HUVECs).

RESULTS

A total of 33 chemical compositions were characterized in TLSGC. Based on these compositions and GIONFH-related genes, 122 hub genes were selected according to topological parameters calculation. Biological functions were mainly enriched in four over-expressed modules of vascular damage, inflammation and apoptosis, bone metabolism and energy metabolism. The hub genes had the maximum enrichment degree in the VEGF-VEGFR2-PKC-Raf1-MEK-ERK signaling axis of the VEGF pathway. Experimentally, the therapeutic effects of TLSGC against GIONFH in rats were proved by micro-CT and pathological examination. Then, the protective effects of TLSGC on vascular damage were determined using angiography, CD31 immunohistochemistry, vascular function indicators in vivo, aortic ring test ex vivo, and the HUVECs activities in vitro including migration, invasion and tube formation. Mechanically, TLSGC effectively suppressed the downregulation of VEGF and VEGFR2 and their downstream targets, including Raf-1, PKC, p-MEK, and p-ERK proteins both in vivo and in vitro.

CONCLUSION

TLSGC could promote angiogenesis by upregulating the VEGF-VEGFR2-PKC-Raf-1-MEK-ERK signaling axis, thereby exerting an apparent curative effect on GIONFH.

Osteoclasts, Master Sculptors of Bone

Osteoclasts are multinucleated cells with the unique ability to resorb bone matrix. Excessive production or activation of osteoclasts leads to skeletal pathologies that affect a significant portion of the population. Although therapies that effectively target osteoclasts have been developed, they are associated with sometimes severe side effects, and a fuller understanding of osteoclast biology may lead to more specific treatments. Along those lines, a rich body of work has defined essential signaling pathways required for osteoclast formation, function, and survival. Nonetheless, recent studies have cast new light on long-held views regarding the origin of these cells during development and homeostasis, their life span, and the cellular sources of factors that drive their production and activity during homeostasis and disease. In this review, we discuss these new findings in the context of existing work and highlight areas of ongoing and future investigation.

Synergistic prevention and reparative effects of sesquiterpene farnesol in a rabbit model of surgical resection-induced osteoarthritis

Articular cartilage may regenerate poorly after injury or during aging. In vitro, farnesol can modulate extracellular matrix synthesis and restore chondrocyte phenotypes by increasing type II collagen (COL II) and glycosaminoglycan (GAG) production. Here, we evaluated farnesol's preventive and reparative effects against osteoarthritis (OA) in vivo. We induced OA in rabbits through resection of the lateral collateral ligament and meniscus. After 2 weeks, the affected limb was treated with 0.5 ml of 0.4 mM farnesol, hyaluronan (HA) nanoparticle-encapsulated 0.8 mM farnesol (Farn/HA), or HA nanoparticles intra-articularly. After 2 and 6 treatment weeks, synovial inflammatory cytokine levels were analyzed. We also removed the entire joint cartilage from lateral femoral condyles for histological investigation. The half-maximum inhibitory concentration of farnesol was 0.5 mM. Farn/HA had relatively low cytotoxicity showing cells remained viable after being treated with 1 mM a concentration Farn/HA. Untreated lateral condyle exhibited extensive wear. By contrast, 0.4 mM farnesol or 0.8 mM Farn/HA led to a relatively transparent and bright appearance. After 2 and 6 treatment weeks, farnesol, particularly 0.8 mM Farn/HA, reduced matrix metalloproteinase 1 and 13 levels considerably. Therefore, 0.8 mM Farn/HA, which enabled slow drug release, demonstrated the highest anti-inflammatory and OA preventive effects. After 6 treatment weeks, farnesol also promoted COL II and GAG synthesis and, thus, aided healing.

Air-breathing behavior underlies the cell death in limbs of Rana pirica tadpoles

Amphibians shape their limbs by differential outgrowth of digits and interdigital regions. In contrast, amniotes employ cell death, an additional developmental system, to determine the final shape of limbs. Previous work has shown that high oxygen availability is correlated with the induction of cell death in developing limbs. Given the diversity of life histories of amphibians, it is conceivable that some amphibians are exposed to a high-oxygen environment during the tadpole phase and exhibit cell death in their limbs. Here, we examined whether air-breathing behavior underlies the cell death in limbs of aquatic tadpoles of the frog species Rana pirica. Our experimental approach revealed that R. pirica tadpoles exhibit cell death in their limbs that is likely to be induced by oxidative stress associated with their frequent air-breathing behavior.

Endothelial SMAD1/5 signaling couples angiogenesis to osteogenesis during long bone growth

Skeletal development depends on coordinated angiogenesis and osteogenesis. Bone morphogenetic proteins direct bone development by activating SMAD1/5 signaling in osteoblasts. However, the role of SMAD1/5 in skeletal endothelium is unknown. Here, we found that endothelial cell-conditional SMAD1/5 depletion in juvenile mice caused metaphyseal and diaphyseal hypervascularity, resulting in altered cancellous and cortical bone formation. SMAD1/5 depletion induced excessive sprouting, disrupting the columnar structure of the metaphyseal vessels and impaired anastomotic loop morphogenesis at the chondro-osseous junction. Endothelial SMAD1/5 depletion impaired growth plate resorption and, upon long term depletion, abrogated osteoprogenitor recruitment to the primary spongiosa. Finally, in the diaphysis, endothelial SMAD1/5 activity was necessary to maintain the sinusoidal phenotype, with SMAD1/5 depletion inducing formation of large vascular loops, featuring elevated endomucin expression, ectopic tip cell formation, and hyperpermeability. Together, endothelial SMAD1/5 activity sustains skeletal vascular morphogenesis and function and coordinates growth plate remodeling and osteoprogenitor recruitment dynamics during bone growth.

Prognostic and therapeutic potential of microRNAs for fracture healing processes and non-union fractures: A systematic review

BACKGROUND

Approximately 10% of all bone fractures result in delayed fracture healing or non-union; thus, the identification of biomarkers and prognostic factors is of great clinical interest. MicroRNAs (miRNAs) are known to be involved in the regulation of the bone healing process and may serve as functional markers for fracture healing.

AIMS AND METHODS

This systematic review aimed to identify common miRNAs involved in fracture healing or non-union fractures using a qualitative approach. A systematic literature search was performed with the keywords 'miRNA and fracture healing' and 'miRNA and non-union fracture'. Any original article investigating miRNAs in fracture healing or non-union fractures was screened. Eventually, 82 studies were included in the qualitative analysis for 'miRNA and fracture healing', while 19 were selected for the 'miRNA and fracture non-union' category.

RESULTS AND CONCLUSIONS

Out of 151 miRNAs, miR-21, miR-140 and miR-214 were the most investigated miRNAs in fracture healing in general. miR-31-5p, miR-221 and miR-451-5p were identified to be regulated specifically in non-union fractures. Large heterogeneity was detected between studies investigating the role of miRNAs in fracture healing or non-union in terms of patient population, sample types and models used. Nonetheless, our approach identified some miRNAs with the potential to serve as biomarkers for non-union fractures, including miR-31-5p, miR-221 and miR-451-5p. We provide a discussion of involved pathways and suggest on alignment of future research in the field.

Intricate role of sleep deprivation in modulating depression: focusing on BDNF, VEGF, serotonin, cortisol, and TNF-α

In this review article, we aimed to discuss intricate roles of SD in modulating depression in preclinical and clinical studies. Decades of research have shown the inconsistent effects of SD on depression, focusing on SD duration. However, inconsistent role of SD seems to be more complicated, and SD duration cannot be the only one factor. Regarding this issue, we chose some important factors involved in the effects of SD on cognitive functions and mood including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), serotonin, cortisol, and tumor necrosis factor-alpha (TNF-α). It was concluded that SD has a wide-range of inconsistent effects on BDNF, VEGF, serotonin, and cortisol levels. It was noted that BDNF diurnal rhythm is significantly involved in the modulatory role of SD in depression. Furthermore, the important role of VEGF in blood-brain barrier permeability which is involved in modulating depression was discussed. It was also noted that there is a negative correlation between cortisol and BDNF that modulates depression. Eventually, it was concluded that TNF-α regulates sleep/wake cycle and is involved in the vulnerability to cognitive and behavioral impairments following SD. TNF-α also increases the permeability of the blood-brain barrier which is accompanied by depressive behavior. In sum, it was suggested that future studies should focus on these mechanisms/factors to better investigate the reasons behind intricate roles of SD in modulating depression.

Bone without borders – Monetite-based calcium phosphate guides bone formation beyond the skeletal envelope

Calcium phosphates (CaP) represent an important class of osteoconductive and osteoinductive biomaterials. As proof-of-concept, we show how a multi-component CaP formulation (monetite, beta-tricalcium phosphate, and calcium pyrophosphate) guides osteogenesis beyond the physiological envelope. In a sheep model, hollow dome-shaped constructs were placed directly over the occipital bone. At 12 months, large amounts of bone (∼75%) occupy the hollow space with strong evidence of ongoing remodelling. Features of both compact bone (osteonal/osteon-like arrangements) and spongy bone (trabeculae separated by marrow cavities) reveal insights into function/need-driven microstructural adaptation. Pores within the CaP also contain both woven bone and vascularised lamellar bone. Osteoclasts actively contribute to CaP degradation/removal. Of the constituent phases, only calcium pyrophosphate persists within osseous (cutting cones) and non-osseous (macrophages) sites. From a translational perspective, this multi-component CaP opens up exciting new avenues for osteotomy-free and minimally-invasive repair of large bone defects and augmentation of the dental alveolar ridge.

•

Dome-shaped hollow multi-component calcium phosphate (CaP) constructs were fabricated.

•

CaP is 85% monetite, 8% beta-tricalcium phosphate, and 7% calcium pyrophosphate.

•

CaP degrades in vivo and remodelled bone occupies the available extraskeletal space.

•

CaP loses monetite to form carbonated apatite; calcium pyrophosphate found in tissues.

•

Extraskeletal bone micro-/nanostructure and composition comparable to the native bone.

Deciphering postnatal limb development at single-cell resolution

The early postnatal limb developmental progression bridges embryonic and mature stages and mirrors the pathological remodeling of articular cartilage. However, compared with multitudinous research on embryonic limb development, the early postnatal stage seems relatively unnoticed. Here, a systematic work to portray the postnatal limb developmental landscape was carried out by characterization of 19,952 single cells from murine hindlimbs at 4 postnatal stages using single-cell RNA sequencing technique. By delineation of cell heterogeneity, the candidate progenitor sub-clusters marked by Cd34 and Ly6e were discovered in articular cartilage and enthesis, and three cellular developmental branches marked by Col10a1, Spp1, and Tnni2 were reflected in growth plate. The representative transcriptomes and developmental patterns were intensively explored, and the key regulation mechanisms as well as evolvement in osteoarthritis were discussed. Above all, these results expand horizons of postnatal limb developmental biology and reach the interconnections between limb development, remodeling, and regeneration.

Resveratrol: Its Path from Isolation to Therapeutic Action in Eye Diseases

Due to the confirmed therapeutic potential of resveratrol (Rv) for eye diseases, namely its powerful anti-angiogenic and antioxidant effects, this molecule must be studied more deeply. Nowadays, the pharmaceutic and pharmacokinetic available studies offer a troubling picture because of its low stability and bioavailability. To overcome this problem, researchers started to design and create different delivery systems that could improve the delivery amount of Rv. Therefore, this review aims to shed light on the proper and efficient techniques to isolate, purify and quantify the Rv molecule, and how this therapeutic molecule can be a part of a delivery system. The Rv great impact on aspects regarding its stability, bioavailability and absorption are also debated here, based on the existent literature on in vitro and in vivo human and animal studies. Moreover, after its absorption the Rv influence at the molecular level in ocular pathologies is described. In addition, the present review summarizes the available literature about Rv, hoping that Rv will gain more attention to investigate its unexplored side.

The role of hypertrophic chondrocytes in regulation of the cartilage-to-bone transition in fracture healing

Endochondral bone formation is an important pathway in fracture healing, involving the formation of a cartilaginous soft callus and the process of cartilage-to-bone transition. Failure or delay in the cartilage-to-bone transition causes an impaired bony union such as nonunion or delayed union. During the healing process, multiple types of cells including chondrocytes, osteoprogenitors, osteoblasts, and endothelial cells coexist in the callus, and inevitably crosstalk with each other. Hypertrophic chondrocytes located between soft cartilaginous callus and bony hard callus mediate the crosstalk regulating cell-matrix degradation, vascularization, osteoclast recruitment, and osteoblast differentiation in autocrine and paracrine manners. Furthermore, hypertrophic chondrocytes can become osteoprogenitors and osteoblasts, and directly contribute to woven bone formation. In this review, we focus on the roles of hypertrophic chondrocytes in fracture healing and dissect the intermingled crosstalk in fracture callus during the cartilage-to-bone transition.

Primary Periphyseal Stress Injuries of the Fingers in Adolescent Climbers: A Critical Review

ABSTRACT

The worldwide rise in popularity of climbing and development of climbing as a competitive sport is reflected by its debut at the 2021 Summer Olympic Games in Tokyo. Digital primary periphyseal stress injuries in adolescent climbers may pose a significant risk to long-term skeletal health. The aim of this article is to critically review research on the diagnosis and management of primary periphyseal stress injuries of the fingers in adolescent climbers. We adopted a systematic approach to searching for relevant literature. Articles were identified after searches of the following electronic databases: Discover, Academic Search Complete, PubMed, Embase, SPORTDiscus, and ScienceDirect. Conclusive evidence suggests digital primary periphyseal stress injuries are a consequence of repetitive microtrauma. Pain reported by adolescent climbers on the dorsal aspect of the proximal interphalangeal joint should be investigated promptly to avoid serious negative consequences. Clinicians should be aware of the efficacy of imaging techniques to inform a clinical diagnosis. A conservative management approach is preferred but in rare cases surgical intervention may be necessary. A diagnostic and therapeutic algorithm for digital primary periphyseal stress injuries is presented.

Horizon of exosome-mediated bone tissue regeneration: The all-rounder role in biomaterial engineering

Bone injury repair has always been a tricky problem in clinic, the recent emergence of bone tissue engineering provides a new direction for the repair of bone injury. However, some bone tissue processes fail to achieve satisfactory results mainly due to insufficient vascularization or cellular immune rejection. Exosomes with the ability of vesicle-mediated intercellular signal transmission have gained worldwide attention and can achieve cell-free therapy. Exosomes are small vesicles that are secreted by cells, which contain genetic material, lipids, proteins and other substances. It has been found to play the function of material exchange between cells. It is widely used in bone tissue engineering to achieve cell-free therapy because it not only does not produce some immune rejection like cells, but also can play a cell-like function. Exosomes from different sources can bind to scaffolds in various ways and affect osteoblast, angioblast, and macrophage polarization in vivo to promote bone regeneration. This article reviews the recent research progress of exosome-loaded tissue engineering, focusing on the mechanism of exosomes from different sources and the application of exosome-loaded scaffolds in promoting bone regeneration. Finally, the existing deficiencies and challenges, future development directions and prospects are summarized.

Neurovascular coupling in bone regeneration

The mammalian skeletal system is densely innervated by both neural and vascular networks. Peripheral nerves in the skeleton include sensory and sympathetic nerves. The crosstalk between skeletal and neural tissues is critical for skeletal development and regeneration. The cellular processes of osteogenesis and angiogenesis are coupled in both physiological and pathophysiological contexts. The cellular and molecular regulation of osteogenesis and angiogenesis have yet to be fully defined. This review will provide a detailed characterization of the regulatory role of nerves and blood vessels during bone regeneration. Furthermore, given the importance of the spatial relationship between nerves and blood vessels in bone, we discuss neurovascular coupling during physiological and pathological bone formation. A better understanding of the interactions between nerves and blood vessels will inform future novel therapeutic neural and vascular targeting for clinical bone repair and regeneration.

Ginsenoside Rg1 interferes with the progression of diabetic osteoporosis by promoting type H angiogenesis modulating vasculogenic and osteogenic coupling

Ginsenoside Rg1 (Rg1) has been demonstrated to have antidiabetic and antiosteoporotic activities. The aim of this study was to investigate the protective effect of Rg1 against diabetic osteoporosis and the underlying mechanism. In vitro, we found that Rg1 increased the number of osteoprogenitors and alleviated high glucose (HG) induced apoptosis of osteoprogenitors by MTT assays and flow cytometry. qRT‒PCR and western blot analysis suggested that Rg1 can also promote the secretion of vascular endothelial growth factor (VEGF) by osteoprogenitors and promote the coupling of osteogenesis and angiogenesis. Rg1 can also promote the proliferation of human umbilical vein endothelial cells (HUVECs) cultured in high glucose, enhance the angiogenic ability of endothelial cells, and activate the Notch pathway to promote endothelial cells to secrete the osteogenesis-related factor Noggin to regulate osteogenesis, providing further feedback coupling of angiogenesis and osteogenesis. Therefore, we speculated that Rg1 may have similar effects on type H vessels. We used the Goto-Kakizaki (GK) rat model to perform immunofluorescence staining analysis on two markers of type H vessels, Endomucin (Emcn) and CD31, and the osteoblast-specific transcription factor Osterix, and found that Rg1 stimulates type H angiogenesis and bone formation. In vivo experiments also demonstrated that Rg1 promotes VEGF secretion, activates the Noggin/Notch pathway, increases the level of coupling between type H vessels and osteogenesis, and improves the bone structure of GK rats. All of these data reveal that Rg1 is a promising candidate drug for treating diabetic osteoporosis as a potentially bioactive molecule that promotes angiogenesis and osteointegration coupling.

Close-to-native bone repair via tissue-engineered endochondral ossification approaches

In order to solve the clinical challenges related to bone grafting, several tissue engineering (TE) strategies have been proposed to repair critical-sized defects. Generally, the classical TE approaches are designed to promote bone repair via intramembranous ossification. Although promising, strategies that direct the osteogenic differentiation of mesenchymal stem/stromal cells are usually characterized by a lack of functional vascular supply, often resulting in necrotic cores. A less explored alternative is engineering bone constructs through a cartilage-mediated approach, resembling the embryological process of endochondral ossification. The remodeling of an intermediary hypertrophic cartilaginous template triggers vascular invasion and bone tissue deposition. Thus, employing this knowledge can be a promising direction for the next generation of bone TE constructs. This review highlights the most recent biomimetic strategies for applying endochondral ossification in bone TE while discussing the plethora of cell types, culture conditions, and biomaterials essential to promote a successful bone regeneration process.

Insights into skeletal stem cells

The tissue-resident skeletal stem cells (SSCs), which are self-renewal and multipotent, continuously provide cells (including chondrocytes, bone cells, marrow adipocytes, and stromal cells) for the development and homeostasis of the skeletal system. In recent decade, utilizing fluorescence-activated cell sorting, lineage tracing, and single-cell sequencing, studies have identified various types of SSCs, plotted the lineage commitment trajectory, and partially revealed their properties under physiological and pathological conditions. In this review, we retrospect to SSCs identification and functional studies. We discuss the principles and approaches to identify bona fide SSCs, highlighting pioneering findings that plot the lineage atlas of SSCs. The roles of SSCs and progenitors in long bone, craniofacial tissues, and periosteum are systematically discussed. We further focus on disputes and challenges in SSC research.

miR-210-3p protects against osteoarthritis through inhibiting subchondral angiogenesis by targeting the expression of TGFBR1 and ID4

Excessive subchondral angiogenesis is a key pathological feature of osteoarthritis (OA), as it alters the balance of subchondral bone remodeling and causes progressive cartilage degradation. We previously found that miR-210-3p correlates negatively with angiogenesis, though the specific mechanism of miR-210-3p-related angiogenesis in subchondral bone during OA progression remains unclear. This study was conducted to identify the miR-210-3p-modulating subchondral angiogenesis mechanism in OA and investigate its therapeutic effect. We found that miR-210-3p expression correlated negatively with subchondral endomucin positive (Emcn+) vasculature in the knee joints of OA mice. miR-210-3p overexpression regulated the angiogenic ability of endothelial cells (ECs) under hypoxic conditions in vitro. Mechanistically, miR-210-3p inhibited ECs angiogenesis by suppressing transforming growth factor beta receptor 1 (TGFBR1) mRNA translation and degrading DNA-binding inhibitor 4 (ID4) mRNA. In addition, TGFBR1 downregulated the expression of ID4. Reduced ID4 levels led to a negative feedback regulation of TGFBR1, enhancing the inhibitory effect of miR-210-3p on angiogenesis. In OA mice, miR-210-3p overexpression in ECs via adeno-associated virus (AAV) alleviated cartilage degradation, suppressed the type 17 immune response and relieved symptoms by attenuating subchondral Emcn+ vasculature and subchondral bone remodeling. In conclusion, we identified a miR-210-3p/TGFBR1/ID4 axis in subchondral ECs that modulates OA progression via subchondral angiogenesis, representing a potential OA therapy target.

The synovial microenvironment suppresses chondrocyte hypertrophy and promotes articular chondrocyte differentiation

During the development of the appendicular skeleton, the cartilaginous templates undergo hypertrophic differentiation and remodels into bone, except for the cartilage most adjacent to joint cavities where hypertrophic differentiation and endochondral bone formation are prevented, and chondrocytes instead form articular cartilage. The mechanisms that prevent hypertrophic differentiation and endochondral bone formation of the articular cartilage have not been elucidated. To explore the role of the synovial microenvironment in chondrocyte differentiation, osteochondral allografts consisting of articular cartilage, epiphyseal bone, and growth plate cartilage from distal femoral epiphyses of inbred Lewis rats expressing enhanced green fluorescent protein from a ubiquitous promoter were transplanted either in inverted or original (control) orientation to matching sites in wildtype littermates, thereby allowing for tracing of transplanted cells and their progenies. We found that no hypertrophic differentiation occurred in the growth plate cartilage ectopically placed at the joint surface. Instead, the transplanted growth plate cartilage, with time, remodeled into articular cartilage. This finding suggests that the microenvironment at the articular surface inhibits hypertrophic differentiation and supports articular cartilage formation. To explore this hypothesis, rat chondrocyte pellets were cultured with and without synoviocyte-conditioned media. Consistent with the hypothesis, hypertrophic differentiation was inhibited and expression of the articular surface marker lubricin (Prg4) was dramatically induced when chondrocyte pellets were exposed to synovium- or synoviocyte-conditioned media, but not to chondrocyte- or osteoblast-conditioned media. Taken together, we present evidence for a novel mechanism by which synoviocytes, through the secretion of a factor or factors, act directly on chondrocytes to inhibit hypertrophic differentiation and endochondral bone formation and promote articular cartilage formation. This mechanism may have important implications for articular cartilage development, maintenance, and regeneration.

Lipid nanoparticle-encapsulated VEGFa siRNA facilitates cartilage formation by suppressing angiogenesis

Cartilage is an important tissue that is widely found in joints, ears, nose and other organs. The limited capacity to regenerate makes cartilage reconstruction an urgent clinical demand. Due to the avascular nature of cartilage, we hypothesized that inhibition of vascularization contributes to cartilage formation. Here, we used VEGFa siRNA to inhibit the infiltration of the local vascular system. Optimized lipid nanoparticles were prepared by microfluidics for the delivery of siRNA. Then, we constructed a tissue engineering scaffold. Both seed cells and VEGFa siRNA-LNPs were loaded in a GELMA hydrogel. Subcutaneous implantation experiments in nude mice indicate that this is a promising strategy for cartilage reconstruction. The regenerated cartilage was superior, with significant upregulation of SOX9, COL-II and ACAN. This is attributed to an environment deficient in oxygen and nutrients, which facilitates cartilage formation by upregulating HIF-1α and FOXO transcription factors. In conclusion, a GelMA/Cells+VEGFa siRNA-LNPs scaffold was constructed to achieve superior cartilage regeneration.

Characterization of the sex-specific pattern of angiogenesis and lymphangiogenesis in aortic stenosis

Objective

We aim to analyze sex-related differences in angiogenesis and lymphangiogenesis in aortic valves (AVs) and valve interstitial cells (VICs) from aortic stenosis (AS) patients.

Approach and Results

Totally 230 patients (59% men) with severe AS undergoing surgical valve replacement were recruited. The density of total neovessels was higher in AVs from men as compared to women. Both small and medium neovessels were more abundant in men's AVs. Accordingly, male AVs exhibited higher CD31 and VE-cadherin expressions. The levels of the pro-angiogenic markers, such as vascular endothelial growth factor (VEGF)-A, VEGF receptor (VEGFR)1, VEGFR2, insulin-like growth factor-binding protein-2 (IGFBP-2), interleukin (IL)-8, chemerin, and fibroblast growth factor (FGF)-7, were increased in AVs from men. Transforming growth factor-β expression was higher in male AVs. The expression of antiangiogenic molecules thrombospondin (Tsp)-1, endostatin, and CD36 was upregulated in male AVs, although the levels of Tsp-2, IL-4, IL-12p70, and chondromodulin-1 were similar between both sexes. The number of lymphatic vessels and the expression of the lymphangiogenic markers Lyve-1 and D2-40 was higher in men's AV as well as VEGF-C, VEGF-D, and VEGFR3. Multivariate analyses adjusted for confounders further validated the sex-dependent expression of these targets. VICs isolated from men's AVs secreted higher amounts of the pro-angiogenic factors, VEGF-A, VEGFR1, IGFBP-2, and FGF-7, as well as the pro-lymphangiogenic factors, VEGF-C, VEGF-D, and VEGFR3, than women without changes in antiangiogenic markers.

Conclusion

Our data show that aberrant angiogenic and lymphangiogenic cues are over-represented in male AVs. Importantly, the VIC is a relevant source of multiple morphogens involved in angiogenesis and lymphangiogenesis likely endowing the AV of men with the predominant calcific AS phenotypes.

Could BMPs Therapy Be Improved if BMPs Were Used in Composition Acting during Bone Formation in Endochondral Ossification?

The discovery of bone morphogenetic proteins (BMPs) inspired hope for the successful treatment of bone disorders, but side effects worsening the clinical effects were eventually observed. BMPs exert a synergistic effect, stimulating osteogenesis; however, predicting the best composition of growth factors for use in humans is difficult. Chondrocytes present within the growth plate produce growth factors stored in calcified cartilage adhering to metaphysis. These factors stimulate initial bone formation in metaphysis. We have previously determined the growth factors present in bovine calcified cartilage and produced by rat epiphyseal chondrocytes. The results suggest that growth factors stimulating physiological ossification are species dependent. The collection of human calcified cartilage for growth factors determination does not appear feasible, but chondrocytes for mRNA determination could be obtained. Their collection from young recipients, in view of the Academy of Medical Royal Colleges Recommendation, would be ethical. The authors of this review do not have facilities to conduct such a study and can only appeal to competent institutions to undertake the task. The results could help to formulate a better recipe for the stimulation of bone formation and improve clinical results.

Single-cell RNA-sequencing analysis reveals the molecular mechanism of subchondral bone cell heterogeneity in the development of osteoarthritis

The cellular composition and underlying spatiotemporal transformation processes of subchondral bone in osteoarthritis (OA) remain unknown. Herein, various cell subsets from tibial plateau of patients with OA are identified, and the mechanism of subchondral microstructure alteration is elaborated using single-cell RNA sequencing technique. We identified two novel endothelial cell (EC) populations characterised by either exosome synthesis and inflammation response or vascular function and angiogenesis. Three osteoblast (OB) subtypes are introduced, separately related to vascularisation, matrix manufacturing and matrix mineralisation. The distinct roles and functions of these novel phenotypes in OA development are further discussed as well as interaction network between these subpopulations. The variation tendency of each population is testified in a destabilisation of the medial meniscus mouse model. The identification of cell types demonstrates a novel taxonomy and mechanism for ECs and OBs inside subchondral bone area provides new insights into the physiological and pathological behaviours of subchondral bone in OA pathogenesis.

Mineral Crystal Thickness in Calcified Cartilage and Subchondral Bone in Healthy and Osteoarthritic Human Knees

Osteoarthritis (OA) is the most common joint disease, where articular cartilage degradation is often accompanied with sclerosis of the subchondral bone. However, the association between OA and tissue mineralization at the nanostructural level is currently not understood. In particular, it is technically challenging to study calcified cartilage, where relevant but poorly understood pathological processes such as tidemark multiplication and advancement occur. Here, we used state-of-the-art microfocus small-angle X-ray scattering with a 5-μm spatial resolution to determine the size and organization of the mineral crystals at the nanostructural level in human subchondral bone and calcified cartilage. Specimens with a wide spectrum of OA severities were acquired from both medial and lateral compartments of medial compartment knee OA patients (n = 15) and cadaver knees (n = 10). Opposing the common notion, we found that calcified cartilage has thicker and more mutually aligned mineral crystals than adjoining bone. In addition, we, for the first time, identified a well-defined layer of calcified cartilage associated with pathological tidemark multiplication, containing 0.32 nm thicker crystals compared to the rest of calcified cartilage. Finally, we found 0.2 nm thicker mineral crystals in both tissues of the lateral compartment in OA compared with healthy knees, indicating a loading-related disease process because the lateral compartment is typically less loaded in medial compartment knee OA. In summary, we report novel changes in mineral crystal thickness during OA. Our data suggest that unloading in the knee might be involved with the growth of mineral crystals, which is especially evident in the calcified cartilage. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

A Novel Hypoxia Related Marker in Blood Link to Aid Diagnosis and Therapy in Osteoarthritis

Osteoarthritis (OA) is a common chronic degenerative arthritis. Its treatment options are very limited. At present, hypoxia is a prominent factor in OA. This study aimed to re-explore the mechanism between hypoxia and OA, which provides new insights into the diagnosis and therapy of OA. We acquired the OA-related expression profiles of GSE48556, GSE55235, and GSE55457 for our analysis. Using gene set variation analysis (GSVA), we found significant differences in hypoxia. These differences result from multiple pathways, such as the p53 signaling pathway, cell senescence, the NF-kappa B signaling pathway, Ubiquitin-mediated proteolysis, and apoptosis. Meanwhile, the single-sample gene set enrichment analysis (ssGSEA) showed that hypoxia was significantly associated with the level of immune cell infiltration in the immune microenvironment. Thus, we believe that hypoxia is useful for the diagnosis and treatment of OA. We successfully constructed a novel hypoxia-related index (HRI) based on seven hypoxia-related genes (ADM, CDKN3, ENO1, NDRG1, PGAM1, SLC2A1, VEGFA) by least absolute shrinkage and binary logistic regression of the generalized linear regression. HRI showed potential for improving OA diagnosis through receiver operation characteristic (ROC) analysis (AUC training cohort = 0.919, AUC testing cohort = 0.985). Moreover, we found that celastrol, droxinostat, torin-2, and narciclasine may be potential therapeutic compounds for OA based on the Connectivity Map (CMap). In conclusion, hypoxia is involved in the development and progression of OA. HRI can improve diagnosis and show great potential in clinical application. Celastrol, droxinostat, torin-2, and narciclasine may be potential compounds for the treatment of OA patients.

Chlorinated benzothiadiazines inhibit angiogenesis through suppression of VEGFR2 phosphorylation

Angiogenesis inhibitors are a critical pharmacological tool for the treatment of solid tumors. Suppressing vascular permeability leads to inhibition of tumor growth, invasion, and metastatic potential by blocking the supply of oxygen and nutrients. Disruption of the vascular endothelial growth factor (VEGF) signaling pathway is a validated target for the design of antiangiogenic agents. Several VEGFR2 inhibitors have been clinically approved over the past years. Structural analysis of these clinical VEGFR2 inhibitors highlighted key functional group overlap with the benzothiadiazine core contained in a library of in-house compounds. Herein we ascribe anti-angiogenic activity to a series of chlorinated benzothiadiazines. Selected compounds show significant activity to completely ameliorate VEGF-induced endothelial cell proliferation by suppression of VEGFR2 phosphorylation. The scaffold is devoid of activity to inhibit carbonic anhydrases and generally lacks cytotoxicity across a range of cancer and non-malignant cell lines. Assay of activity at 468 kinases shows remarkable selectivity with only four kinases inhibited > 65% at 10 µM concentration, and with significant activity to inhibit TNK2/ACK1 and PKRD2 by > 90%. All four identified kinase targets are known modulators of angiogenesis, thus highlighting compound 17b as a novel angiogenesis inhibitor for further development.

Microfluidic Droplet-SERS Platform for Single-Cell Cytokine Analysis via a Cell Surface Bioconjugation Strategy

A microfluidic-based surface-enhanced Raman scattering (SERS) platform for analyzing cytokines secreted by single cells is reported based on the elaborate bioconjugation of the immuno-sandwich complex on the probed cell surface. This platform integrates the dual functions of microfluidic droplet separation of single cells and SERS measurement. Two immune nanoprobes (capture probe and SERS probe) are introduced into a microfluidic droplet along with a single cell. They were anchored to the cell membrane protein surface by capturing secreted cytokines to form an immune sandwich structure, realizing the enrichment effect of cytokines above the cell membrane surface and the amplification effect of SERS detection probes. This single-cell analytical platform was applied to track specific cell-secreted vascular endothelial growth factor (VEGF) of different cell lines (MCF-7, SGC, and T24), and highly sensitive detection of VEGF was achieved. Chemometric methods (principal component analysis and t-distributed stochastic neighbor embedding) were adopted for the SERS data analysis, and the support vector machine (SVM) discriminant model was established to test the data. These chemometric methods successfully identify significant differences in the secreting ability of cytokines among three kinds of cancer cell lines, revealing cell heterogeneity. In addition, the behavior of single cells secreting VEGF was monitored time-dependently and was shown to increase with time. This work demonstrates the importance of tracking specific cells secreting cytokines based on the cell surface bioconjugation strategy. Our developed platform provides guidelines for using the single-cell exocytosis factors as biomarkers to assess the early diagnosis of cancer and provide physiological cues for learning single-cell secretions.

Vascular injury of immature epiphyses impair stem cell engraftment in cartilage defects

The purpose of our study was to investigate if vascular injury in immature epiphyses affects cartilage repair outcomes of matrix-associated stem cell implants (MASI). Porcine bone marrow mesenchymal stromal stem cells (BMSCs) suspended in a fibrin glue scaffold were implanted into 24 full-thickness cartilage defects (5 mm ø) of the bilateral distal femur of six Göttingen minipigs (n = 12 defects in 6 knee joints of 3 immature pigs; age 3.5-4 months; n = 12 defects in 6 knee joints of 3 mature control pigs; age, 21-28 months). All pigs underwent magnetic resonance imaging (MRI) at 2, 4, 12 (n = 24 defects), and 24 weeks (n = 12 defects). After the last imaging study, pigs were sacrificed, joints explanted and evaluated with VEGF, H&E, van Gieson, Mallory, and Safranin O stains. Results of mature and immature cartilage groups were compared using the Wilcoxon signed-rank test. Quantitative scores for subchondral edema at 2 weeks were correlated with quantitative scores for cartilage repair (MOCART score and ICRS score) at 12 weeks as well as Pineda scores at end of the study, using linear regression analysis. On serial MRIs, mature joints demonstrated progressive healing of cartilage defects while immature joints demonstrated incomplete healing and damage of the subchondral bone. The MOCART score at 12 weeks was significantly higher for mature joints (79.583 ± 7.216) compared to immature joints (30.416 ± 10.543, p = 0.002). Immature cartilage demonstrated abundant microvessels while mature cartilage did not contain microvessels. Accordingly, cartilage defects in immature joints showed a significantly higher number of disrupted microvessels, subchondral edema, and angiogenesis compared to mature cartilage. Quantitative scores for subchondral edema at 2 weeks were negatively correlated with MOCART scores (r =  - 0.861) and ICRS scores (r =  - 0.901) at 12 weeks and positively correlated with Pineda scores at the end of the study (r = 0.782). Injury of epiphyseal blood vessels in immature joints leads to subchondral bone defects and limits cartilage repair after MASI.

Oxygen generating scaffolds regenerate critical size bone defects

Recent innovations in bone tissue engineering have introduced biomaterials that generate oxygen to substitute vasculature. This strategy provides the immediate oxygen required for tissue viability and graft maturation. Here we demonstrate a novel oxygen-generating tissue scaffold with predictable oxygen release kinetics and modular material properties. These hydrogel scaffolds were reinforced with microparticles comprised of emulsified calcium peroxide (CaO₂) within polycaprolactone (PCL). The alterations of the assembled materials produced constructs within 5 ± 0.81 kPa to 34 ± 0.9 kPa in mechanical strength. The mass swelling ratios varied between 11% and 25%. Our in vitro and in vivo results revealed consistent tissue viability, metabolic activity, and osteogenic differentiation over two weeks. The optimized in vitro cell culture system remained stable at pH 8–9. The in vivo rodent models demonstrated that these scaffolds support a 70 mm³ bone volume that was comparable to the native bone and yielded over 90% regeneration in critical size cranial defects. Furthermore, the in vivo bone remodeling and vascularization results were validated by tartrate-resistant acid phosphatase (TRAP) and vascular endothelial growth factor (VEGF) staining. The promising results of this work are translatable to a repertoire of regenerative medicine applications including advancement and expansion of bone substitutes and disease models.

•

Hydrogels reinforced with oxygen generating particles provided sustained oxygen.

•

Tunable biological, chemical, and mechanical properties obtained by varying oxygen.

•

Implanted scaffolds supported bone remodeling and vascularization at defect site.

•

Oxygen generating biomaterials regenerated critical size bone defects.

Developmental principles informing human pluripotent stem cell differentiation to cartilage and bone

Human pluripotent stem cells can differentiate into any cell type given appropriate signals and hence have been used to research early human development of many tissues and diseases. Here, we review the major biological factors that regulate cartilage and bone development through the three main routes of neural crest, lateral plate mesoderm and paraxial mesoderm. We examine how these routes have been used in differentiation protocols that replicate skeletal development using human pluripotent stem cells and how these methods have been refined and improved over time. Finally, we discuss how pluripotent stem cells can be employed to understand human skeletal genetic diseases with a developmental origin and phenotype, and how developmental protocols have been applied to gain a better understanding of these conditions.

The Effect of Platelet-Rich Plasma on Type I Collagen Production, VEGF Expression, and Neovascularization after Femoral Bone Implants: A Study on Rat Models

Introduction

Platelet-rich plasma (PRP) contains many growth factors, such as FGF, which induces the production of type I collagen, and VEGF, which induces neovascularization, all of which are important in bone healing. This study aimed to evaluate the effect of PRP administration on type I collagen production, VEGF expression, and neovascularization in rat models following femoral bone implants using K-wire.

Methods

An experimental randomized control study was conducted on 24 white male rats (Rattus norvegicus) in the Wistar strain that underwent K-wire implantation, where PRP was administered to the treatment groups. The amount of type I collagen was measured by immunohistochemistry VEGF expression using sandwich ELISA, and neovascularization by histopathological examination.

Results

The amount of type I collagen in the treatment group (50–>150/field of view) was significantly higher than the control group (0–99/field of view; p=0.003). VEGF expression in the treatment groups was significantly higher than controls: 10.90±4.47 and 2.29±0.92, respectively (p=0.006). Mean number of new vessels formed on fibrotic capsules in the treatment groups was significantly (p=0.007) higher than the control groups (2.69±1.03 vs 0.67±0.52).

Conclusion

The use of PRP significantly increased type I collagen production, VEGF expression, and neovascularization in rat models, elucidating the potential of PRP to be used in clinical settings to enhance the bone-healing process.

In situ microenvironment remodeling using a dual-responsive system: photodegradable hydrogels and gene activation by visible light

A 3D microenvironment with dynamic cell-biomaterial interactions was developed using a dual-responsive system for in situ microenvironment remodeling and control of cellular function. A visible-light-responsive polymer was utilized to prepare a hydrogel with photodegradation properties, enabling in situ microenvironment remodeling. Additionally, a vascular endothelial growth factor (VEGF) gene activation unit that was responsive to the same wavelength of light was incorporated to support the potential application of the system in regenerative medicine. Following light exposure, the mechanical properties of the photodegradable hydrogel gradually deteriorated, and product analysis confirmed the degradation of the hydrogel, and thereby, 3D microenvironment remodeling. In situ microenvironment remodeling influenced stem cell proliferation and enlargement within the hydrogel. Furthermore, stem cells engineered to express light-activated VEGF and incorporated into the dual-responsive system were applied to wound healing and an ischemic hindlimb model, proving their potential application in regenerative medicine.

Mechanical forces couple bone matrix mineralization with inhibition of angiogenesis to limit adolescent bone growth

Bone growth requires a specialised, highly angiogenic blood vessel subtype, so-called type H vessels, which pave the way for osteoblasts surrounding these vessels. At the end of adolescence, type H vessels differentiate into quiescent type L endothelium lacking the capacity to promote bone growth. Until now, the signals that switch off type H vessel identity and thus limit adolescent bone growth have remained ill defined. Here we show that mechanical forces, associated with increased body weight at the end of adolescence, trigger the mechanoreceptor PIEZO1 and thereby mediate enhanced production of the kinase FAM20C in osteoblasts. FAM20C, the major kinase of the secreted phosphoproteome, phosphorylates dentin matrix protein 1, previously identified as a key factor in bone mineralization. Thereupon, dentin matrix protein 1 is secreted from osteoblasts in a burst-like manner. Extracellular dentin matrix protein 1 inhibits vascular endothelial growth factor signalling by preventing phosphorylation of vascular endothelial growth factor receptor 2. Hence, secreted dentin matrix protein 1 transforms type H vessels into type L to limit bone growth activity and enhance bone mineralization. The discovered mechanism may suggest new options for the treatment of diseases characterised by aberrant activity of bone and vessels such as osteoarthritis, osteoporosis and osteosarcoma.

Bevacizumab-Laden Nanofibers Simulating an Antiangiogenic Niche to Improve the Submuscular Stability of Stem Cell Engineered Cartilage

Bone marrow stem cells (BMSCs) engineered cartilage (BEC) is prone to endochondral ossification in a submuscular environment due to the process of vascular infiltration, which limits its application in repairing tracheal cartilage defects. Bevacizumab, an antitumor drug with pronounced antiangiogenic activity, is successfully laden into a poly(L-lactide-co-caprolactone) system to prepare bevacizumab-laden nanofiber (BevNF) characterized by 5% and 10% bevacizumab concentrations. The in vitro results reveal that a sustained release of bevacizumab can be realized from BevNF, exhibiting inhibitive cytotoxicity toward human umbilical vein endothelial cells whereas non-cytotoxicity toward BMSCs-induced chondrocytes. A model is also established by encapsulating BEC within BevNF, aiming to realize an antiangiogenic niche under conditions of sustained and localized release of bevacizumab to inhibit the process of vascular invasion, resulting in the eventual stabilization of the cartilaginous phenotype and promotion of the process of cartilage maturation in the submuscular environment. These results also confirm that the chondrogenesis stability of BEC increases with an increase in the bevacizumab concentration, and 10% BevNF is sufficient to protect BEC from vascularization. This demonstrates that the use of BevNF can potentially help develop an effective strategy for regulating the submuscular stability of BEC to repair the defects formed in tracheal cartilage.

Ablation of the miRNA cluster 24 in cartilage and osteoblasts impairs bone remodeling

MicroRNAs (miRNAs) post-transcriptionally regulate cartilage and bone development and function, however, only few miRNAs have been described to play a role for cartilage to bone transition in vivo. Previously, we showed that cartilage-specific deletion of the Mirc24 cluster in newborn male mice leads to impaired growth plate cartilage development due to increased RAF/MEK/ERK signaling and affects the stability of the cartilage extracellular matrix on account of decreased SOX6 and SOX9 and increased MMP13 levels. Here, we studied how Mirc24 cluster inactivation in cartilage and osteoblasts leads to an increased bone density associated with defects in collagen remodeling in trabecular bone. No changes in osteoblast distribution were observed, whereas the number of osteoclasts was reduced and TRAP activity in osteoclasts decreased. Surprisingly, an increased level of cluster-encoded miR-322 or miR-503 raises Rankl gene expression and inactivation of the cluster in chondrocytes reduces Rankl expression. These results suggest that the Mirc24 cluster regulates Rankl expression in chondrocytes at the chondro-osseous border, where the cluster is mainly expressed to modulate osteoclast formation, bone remodeling and bone integrity.

Ciliary IFT88 Protects Coordinated Adolescent Growth Plate Ossification From Disruptive Physiological Mechanical Forces

Compared with our understanding of endochondral ossification, much less is known about the coordinated arrest of growth defined by the narrowing and fusion of the cartilaginous growth plate. Throughout the musculoskeletal system, appropriate cell and tissue responses to mechanical force delineate morphogenesis and ensure lifelong health. It remains unclear how mechanical cues are integrated into many biological programs, including those coordinating the ossification of the adolescent growth plate at the cessation of growth. Primary cilia are microtubule-based organelles tuning a range of cell activities, including signaling cascades activated or modulated by extracellular biophysical cues. Cilia have been proposed to directly facilitate cell mechanotransduction. To explore the influence of primary cilia in the mouse adolescent limb, we conditionally targeted the ciliary gene Intraflagellar transport protein 88 (Ift88^fl/fl ) in the juvenile and adolescent skeleton using a cartilage-specific, inducible Cre (AggrecanCreER^T2 Ift88^fl/fl ). Deletion of IFT88 in cartilage, which reduced ciliation in the growth plate, disrupted chondrocyte differentiation, cartilage resorption, and mineralization. These effects were largely restricted to peripheral tibial regions beneath the load-bearing compartments of the knee. These regions were typified by an enlarged population of hypertrophic chondrocytes. Although normal patterns of hedgehog signaling were maintained, targeting IFT88 inhibited hypertrophic chondrocyte VEGF expression and downstream vascular recruitment, osteoclastic activity, and the replacement of cartilage with bone. In control mice, increases to physiological loading also impair ossification in the peripheral growth plate, mimicking the effects of IFT88 deletion. Limb immobilization inhibited changes to VEGF expression and epiphyseal morphology in Ift88cKO mice, indicating the effects of depletion of IFT88 in the adolescent growth plate are mechano-dependent. We propose that during this pivotal phase in adolescent skeletal maturation, ciliary IFT88 protects uniform, coordinated ossification of the growth plate from an otherwise disruptive heterogeneity of physiological mechanical forces. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Rhythm disturbance in osteoarthritis

Osteoarthritis (OA) is one of the main causes of disabilities among older people. To date, multiple disease-related molecular networks in OA have been identified, including abnormal mechanical loadings and local inflammation. These pathways have not, however, properly elucidated the mechanism of OA progression. Recently, sufficient evidence has suggested that rhythmic disturbances in the central nervous system (CNS) and local joint tissues affect the homeostasis of joint and can escalate pathological changes of OA. This is accompanied with an exacerbation of joint symptoms that interfere with the rhythm of CNS in reverse. Eventually, these processes aggravate OA progression. At present, the crosstalk between joint tissues and biological rhythm remains poorly understood. As such, the mechanisms of rhythm changes in joint tissues are worth study; in particular, research on the effect of rhythmic genes on metabolism and inflammation would facilitate the understanding of the natural rhythms of joint tissues and the OA pathology resulting from rhythm disturbance.

Anti-Angiogenic and Cytotoxicity Effects of Selachyl Alcohol Analogues

BACKGROUND

The active ingredients in the shark liver oil (SLO) mixture were found to be a group of etherlinked glycerol known as alkylglycerols (AKGs). During the last century, initial clinical use of the SLO mixture was for treating leukemias and later preventing radiation sickness from cancer x-ray therapy. Selachyl alcohol is one of the most abundant AKGs in the SLO mixture and it displayed strong activity in reducing lung metastasis number on a model of grafted tumor in mice (Lewis lung carcinoma cells).

OBJECTIVES

In this study, selachyl alcohol analogue containing methoxyl (7), gem-difluorinated (8), azide (9) and hydroxyl (10) group at the 12 position in the alkyl chain were synthesized and compared regarding their cytotoxicity and anti-migratory effects on Human Umbilical Vein Endothelial Cell line.

METHODS

AKGs 7-10 were synthesized according to the literature procedure. The cytotoxicity of the studied AKGs was evaluated by the MTT test and Human Umbilical Vein Endothelial Cell line (HUVEC) was used as an in vitro model to evaluate their anti-migratory effects.

RESULTS

The four AKGs have substantially the same toxicity threshold (≥ 12 μM), whereas they have an anti-migratory activity significantly different on endothelial cells. AKGs 9 and 10 significantly reduce the chemotactic migration induced by VEGF, but analogue (10) containing the hydroxyl group at the 12 position in the alkyl chain was the most potent anti-VEGF inhibitor.

CONCLUSION

We presented here a series of four synthetic selachyl alcohol analogues, among which AKGs 9 and 10 showed the ability to inhibit endothelial cell migration. The relationship structures and anti-VEGF effects of these analogues were also evaluated and discussed. Unnatural synthesized AKGs could be explored as one new source of anticancer agents.