Does cranial bone ossification differ in children with developmental dysplasia of the hip?

OBJECTIVES: This study aims to compare cranial bone ossification between patients with developmental dysplasia of the hip (DDH) and healthy individuals. PATIENTS AND METHODS: Between September 2021 and April 2022, a total of 60 healthy female individuals (median age: 24.5 months; range, 18 to 36 months) and 56 female DDH patients (median age: 23 months; range, 18 to 35 months) were included. Age, head circumference, weight, height, and patency of the anterior fontanel were measured in groups. Percentiles were classified as very low, low, normal, high and very high. All patients were female and those with abnormal thyroid function test, vitamin D, calcium, phosphate and alkaline phosphatase values were not included in the study. For those diagnosed with DDH, they were included in the group regardless of the type of treatment. RESULTS: No statistically significant difference was found between the groups in terms of age and weight (p>0.05). The very low and very high head circumferences were more frequent, and the normal head circumferences were less frequent in the DDH group (p<0.05). There was no significant difference between groups in terms of fontanel closure (p>0.05). In open fontanels, no significant difference was found in both groups in terms of age (p>0.05). CONCLUSION: Our study results showed no significant difference between the fontanel ossifications of children with and without DDH; however, we found that the ossification of the skull bones of children with DDH was different compared to healthy children.

Determination of mandibular distraction osteogenesis most suitable parameters. An experimental study.

BACKGROUND: Distraction osteogenesis is a process of induced bone generation. Various protocols have been described for the management of the latency period, distraction speed and consolidation period, with greater or lesser success. OBJECTIVE: To better understand the process of mandibular distraction and establish the determining factors and their optimal times. MATERIAL AND METHODS: Twenty-seven dogs were studied, which had 54 distractors placed and that underwent unidirectional, bilateral mandibular distraction osteogenesis. The distraction processes were applied using six variants, two for each factor: latency period, distraction period and distraction speed. The changes were examined by means of bone biopsies and X-rays of the area at 0, 7, 14, 21, 45 and 55 days of the process. RESULTS: The most efficient osteogenic distraction parameters were a latency period of five days, a consolidation period of six weeks, distraction speed of 1 mm/day for distances of less than 20 mm, and 3 mm/day for longer distances. CONCLUSIONS: The sequential histological study allowed to observe the appearance of cellular elements (osteocytes, osteoclasts, osteoid matrix, trabeculate, etc.) and their participation in granulation tissue, newly-formed bone and compact mature bone.

ANTECEDENTES: Respecto a la distracción osteogénica (generación ósea inducida), con mayor o menor éxito han sido descritos diversos protocolos para el manejo del período de latencia, velocidad de distracción y período de consolidación. ­. OBJETIVO: Entender mejor el proceso de la distracción mandibular y establecer los factores determinantes y sus tiempos óptimos. MATERIAL Y MÉTODOS: Se estudiaron 27 perros sometidos a distracción osteogénica unidireccional, bilateral de la mandíbula. Los procesos de distracción se aplicaron con seis variantes, dos por cada factor (período de latencia, período de distracción y velocidad de distracción). Se estudiaron los cambios mediante biopsias del hueso y radiografías de la zona a los 0, 7, 14, 21, 45 y 55 días del proceso. RESULTADOS: Los parámetros de distracción osteogénica más eficientes fueron período de latencia de cinco días, período de consolidación de seis semanas, 1 mm diario de velocidad de distracción para distancias menores a 20 mm y 3 mm diarios para distancias mayores. CONCLUSIONES: El estudio histológico secuencial permitió observar la aparición de los elementos celulares (osteocitos, osteoclastos, matriz osteoide, trabeculado, etcétera) y su participación en el tejido de granulación, el hueso neoformado y el hueso maduro compacto.

A 3D In-vitro model of the human dentine interface shows long-range osteoinduction from the dentine surface.

Emerging regenerative cell therapies for alveolar bone loss have begun to explore the use of cell laden hydrogels for minimally invasive surgery to treat small and spatially complex maxilla-oral defects. However, the oral cavity presents a unique and challenging environment for in vivo bone tissue engineering, exhibiting both hard and soft periodontal tissue as well as acting as key biocenosis for many distinct microbial communities that interact with both the external environment and internal body systems, which will impact on cell fate and subsequent treatment efficacy. Herein, we design and bioprint a facile 3D in vitro model of a human dentine interface to probe the effect of the dentine surface on human mesenchymal stem cells (hMSCs) encapsulated in a microporous hydrogel bioink. We demonstrate that the dentine substrate induces osteogenic differentiation of encapsulated hMSCs, and that both dentine and ß-tricalcium phosphate substrates stimulate extracellular matrix production and maturation at the gel-media interface, which is distal to the gel-substrate interface. Our findings demonstrate the potential for long-range effects on stem cells by mineralized surfaces during bone tissue engineering and provide a framework for the rapid development of 3D dentine-bone interface models.

Carboxypeptidase M modulates BMSCs osteogenesis-adipogenesis via the MAPK/ERK pathway: An integrated single-cell and bulk transcriptomic study.

The pathogenesis of osteoporosis (OP) is closely associated with the disrupted balance between osteogenesis and adipogenesis in bone marrow-derived mesenchymal stem cells (BMSCs). We analyzed published single-cell RNA sequencing (scRNA-seq) data to dissect the transcriptomic profiles of bone marrow-derived cells in OP, reviewing 56 377 cells across eight scRNA-seq datasets from femoral heads (osteoporosis or osteopenia n = 5, osteoarthritis n = 3). Seventeen genes, including carboxypeptidase M (CPM), were identified as key osteogenesis-adipogenesis regulators through comprehensive gene set enrichment, differential expression, regulon activity, and pseudotime analyses. In vitro, CPM knockdown reduced osteogenesis and promoted adipogenesis in BMSCs, while adenovirus-mediated CPM overexpression had the reverse effects. In vivo, intraosseous injection of CPM-overexpressing BMSCs mitigated bone loss in ovariectomized mice. Integrated scRNA-seq and bulk RNA sequencing analyses provided insight into the MAPK/ERK pathway's role in the CPM-mediated regulation of BMSC osteogenesis and adipogenesis; specifically, CPM overexpression enhanced MAPK/ERK signaling and osteogenesis. In contrast, the ERK1/2 inhibitor binimetinib negated the effects of CPM overexpression. Overall, our findings identify CPM as a pivotal regulator of BMSC differentiation, which provides new clues for the mechanistic study of OP.

Excess glucose alone depress young mesenchymal stromal/stem cell osteogenesis and mitochondria activity within hours/days via NAD+/SIRT1 axis.

BACKGROUND: The impact of global overconsumption of simple sugars on bone health, which peaks in adolescence/early adulthood and correlates with osteoporosis (OP) and fracture risk decades, is unclear. Mesenchymal stromal/stem cells (MSCs) are the progenitors of osteoblasts/bone-forming cells, and known to decrease their osteogenic differentiation capacity with age. Alarmingly, while there is correlative evidence that adolescents consuming greatest amounts of simple sugars have the lowest bone mass, there is no mechanistic understanding on the causality of this correlation. METHODS: Bioinformatics analyses for energetics pathways involved during MSC differentiation using human cell information was performed. In vitro dissection of normal versus high glucose (HG) conditions on osteo-/adipo-lineage commitment and mitochondrial function was assessed using multi-sources of non-senescent human and murine MSCs; for in vivo validation, young mice was fed normal or HG-added water with subsequent analyses of bone marrow CD45- MSCs. RESULTS: Bioinformatics analyses revealed mitochondrial and glucose-related metabolic pathways as integral to MSC osteo-/adipo-lineage commitment. Functionally, in vitro HG alone without differentiation induction decreased both MSC mitochondrial activity and osteogenesis while enhancing adipogenesis by 8 h' time due to depletion of nicotinamide adenine dinucleotide (NAD+), a vital mitochondrial co-enzyme and co-factor to Sirtuin (SIRT) 1, a longevity gene also involved in osteogenesis. In vivo, HG intake in young mice depleted MSC NAD+, with oral NAD+ precursor supplementation rapidly reversing both mitochondrial decline and osteo-/adipo-commitment in a SIRT1-dependent fashion within 1 ~ 5 days. CONCLUSIONS: We found a surprisingly rapid impact of excessive glucose, a single dietary factor, on MSC SIRT1 function and osteogenesis in youthful settings, and the crucial role of NAD+-a single molecule-on both MSC mitochondrial function and lineage commitment. These findings have strong implications on future global OP and disability risks in light of current worldwide overconsumption of simple sugars.

Inhibition of lipopolysaccharide-induced NF-κB maintains osteogenesis of dental pulp and periodontal ligament stem cells.

Dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) can differentiate into osteoblasts, indicating that both are potential candidates for bone tissue engineering. Osteogenesis is influenced by many environmental factors, one of which is lipopolysaccharide (LPS). LPS-induced NF-κB activity affects the osteogenic potencies of different types of MSCs differently. This study evaluated the effect of LPS-induced NF-κB activity and its inhibition in DPSCs and PDLSCs. DPSCs and PDLSCs were cultured in an osteogenic medium, pretreated with/without NF-κB inhibitor Bay 11-7082, and treated with/without LPS. Alizarin red staining was performed to assess bone nodule formation, which was observed under an inverted light microscope. NF-κB and alkaline phosphatase (ALP) activities were measured to examine the effect of Bay 11-7082 pretreatment and LPS supplementation on osteogenic differentiation of DPSCs and PDLSCs. LPS significantly induced NF-κB activity (p = 0.000) and reduced ALP activity (p = 0.000), which inhibited bone nodule formation in DPSCs and PDLSCs. Bay 11-7082 inhibited LPS-induced NF-κB activity, and partially maintained ALP activity and osteogenic potency of LPS-supplemented DPSCs and PDLSCs. Thus, inhibition of LPS-induced NF-κB activity can maintain the osteogenic potency of DPSCs and PDLSCs.

Buccal Mesenchymal Stromal Cells as a Source of Osseointegration of Titanium Implants.

We studied the interaction of human buccal mesenchymal stem cells (MSCs) and osteoblasts differentiated from them with the surface of titanium samples. MSCs were isolated by enzymatic method from buccal fat pads. The obtained cell culture was presented by MSCs, which was confirmed by flow cytometry and differentiation into adipocytes and osteoblasts. Culturing of buccal MSCs on titanium samples was accompanied by an increase in the number of cells for 15 days and the formation of a developed network of F-actin fibers in the cells. The viability of buccal MSCs decreased by 8 days, but was restored by 15 days. Culturing of osteoblasts obtained as a result of buccal MSC differentiation on the surface of titanium samples was accompanied by a decrease in their viability and proliferation. Thus, MSCs from buccal fat pads can be used to coat implants to improve osseointegration during bone reconstruction in craniofacial surgery and dentistry. To improve the integration of osteoblasts, modification of the surface of titanium samples is required.

Pannexins in the musculoskeletal system: new targets for development and disease progression.

During cell differentiation, growth, and development, cells can respond to extracellular stimuli through communication channels. Pannexin (Panx) family and connexin (Cx) family are two important types of channel-forming proteins. Panx family contains three members (Panx1-3) and is expressed widely in bone, cartilage and muscle. Although there is no sequence homology between Panx family and Cx family, they exhibit similar configurations and functions. Similar to Cxs, the key roles of Panxs in the maintenance of physiological functions of the musculoskeletal system and disease progression were gradually revealed later. Here, we seek to elucidate the structure of Panxs and their roles in regulating processes such as osteogenesis, chondrogenesis, and muscle growth. We also focus on the comparison between Cx and Panx. As a new key target, Panxs expression imbalance and dysfunction in muscle and the therapeutic potentials of Panxs in joint diseases are also discussed.

Conditional loss of CaMKK2 in Osterix-positive osteoprogenitors enhances osteoblast function in a sex-divergent manner.

Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is a multi-functional, serine/threonine protein kinase with predominant roles in inflammation, systemic energy metabolism, and bone remodeling. We previously reported that global ablation of CaMKK2 or its systemic pharmacological inhibition led to bone mass accrual in mice by stimulating osteoblasts and inhibiting osteoclasts. However, a direct, cell-intrinsic role for the kinase in the osteoblast lineage has not been established. Here we report that conditional deletion of CaMKK2 from osteoprogenitors, using the Osterix 1 (Osx1) - GFP::Cre (tetracycline-off) mouse line, resulted in increased trabecular bone mass due to an acute stimulation of osteoblast function in male and female mice. The acute simulation of osteoblasts and bone formation following conditional ablation of osteoprogenitor-derived CaMKK2 was sustained only in female mice. Periosteal bone formation at the cortical bone was enhanced only in male conditional knockout mice without altering cortical bone mass or strength. Prolonged deletion of CaMKK2 in early osteoblasts was accompanied by a stimulation of osteoclasts in both sexes, indicating a coupling effect. Notably, alterations in trabecular and cortical bone mass were absent in the doxycycline-removed "Cre-only" Osx1-GFP::Cre mice. Thus, the increase in osteoblast function at the trabecular and cortical bone surfaces following the conditional deletion of CaMKK2 in osteoprogenitors is indicative of a direct but sex-divergent role for the kinase in osteoblasts.

Multiomics profiling reveals VDR as a central regulator of mesenchymal stem cell senescence with a known association with osteoporosis after high-fat diet exposure.

The consumption of a high-fat diet (HFD) has been linked to osteoporosis and an increased risk of fragility fractures. However, the specific mechanisms of HFD-induced osteoporosis are not fully understood. Our study shows that exposure to an HFD induces premature senescence in bone marrow mesenchymal stem cells (BMSCs), diminishing their proliferation and osteogenic capability, and thereby contributes to osteoporosis. Transcriptomic and chromatin accessibility analyses revealed the decreased chromatin accessibility of vitamin D receptor (VDR)-binding sequences and decreased VDR signaling in BMSCs from HFD-fed mice, suggesting that VDR is a key regulator of BMSC senescence. Notably, the administration of a VDR activator to HFD-fed mice rescued BMSC senescence and significantly improved osteogenesis, bone mass, and other bone parameters. Mechanistically, VDR activation reduced BMSC senescence by decreasing intracellular reactive oxygen species (ROS) levels and preserving mitochondrial function. Our findings not only elucidate the mechanisms by which an HFD induces BMSC senescence and associated osteoporosis but also offer new insights into treating HFD-induced osteoporosis by targeting the VDR-superoxide dismutase 2 (SOD2)-ROS axis.

RNA Technology to Regenerate and Repair Alveolar Bone Defects.

microRNA-200a (miR-200a) targets multiple signaling pathways that are involved in osteogenic differentiation and bone development. However, its therapeutic function in osteogenesis and bone regeneration remains unknown. In this study, we use in vitro and in vivo models to investigate the molecular function of miR-200a overexpression and miR-200a inhibition using a plasmid-based miR inhibitor system (PMIS) on osteogenic differentiation and bone regeneration. Inhibition of miR-200a using PMIS-miR-200a significantly increased osteogenic biomarkers of human embryonic palatal mesenchyme cells and promoted bone regeneration in rat tooth socket defects. In rat maxillary M1 molar extractions, the supporting tooth structures were removed with an implant drill to yield a 3-mm defect in the alveolar bone. A collagen sponge was inserted into the open alveolar defect and PMIS-miR-200a plasmid DNA was added to the sponge and the wound sutured to protect the sponge and close the defect. It was important to remove the existing tooth supporting structure, which can influence alveolar bone regeneration. The alveolar bone was regenerated in 4 wk. The collagen sponge acts to stabilize and deliver the PMIS-miR-200a DNA to cells entering the sponge in the bone defect. We show that mesenchymal stem cells expressing CD90 and Stro-1 enter the sponges, take up the DNA, and express PMIS-miR-200a. PMIS-miR-200a initiates a bone regeneration program in transformed cells in vivo. In vitro inhibition of miR-200a was found to upregulate Wnt and BMP signaling activity as well as Runx2, OCN, Lef-1, Msx2, and Dlx5 associated with osteogenesis. Liver and blood toxicity testing of PMIS-miR-200a-treated rats showed no increase in several biomarkers of liver disease. These results demonstrate the therapeutic function of PMIS-miR-200a for rapid bone regeneration. Furthermore, the studies were designed to demonstrate the ease of use of PMIS-miR-200a in solution and applied using a syringe in the clinic through a simple one-time application.

Role of epigenetic regulatory mechanisms in age-related bone homeostasis imbalance.

Alterations to the human organism that are brought about by aging are comprehensive and detrimental. Of these, an imbalance in bone homeostasis is a major outward manifestation of aging. In older adults, the decreased osteogenic activity of bone marrow mesenchymal stem cells and the inhibition of bone marrow mesenchymal stem cell differentiation lead to decreased bone mass, increased risk of fracture, and impaired bone injury healing. In the past decades, numerous studies have reported the epigenetic alterations that occur during aging, such as decreased core histones, altered DNA methylation patterns, and abnormalities in noncoding RNAs, which ultimately lead to genomic abnormalities and affect the expression of downstream signaling osteoporosis treatment and promoter of fracture healing in older adults. The current review summarizes the impact of epigenetic regulation mechanisms on age-related bone homeostasis imbalance.

Alternated activation with relaxation of periosteum stimulates bone modeling and remodeling.

Gradual elevation of the periosteum from the original bone surface, based on the principle of distraction osteogenesis, induces endogenous hard and soft tissue formation. This study aimed to assess the impact of alternating protocols of activation with relaxation (periosteal pumping) on bone modeling and remodeling. One hundred and sixty-two adult male Wistar rats were used in this study. Four test groups with different pumping protocols were created based on the relaxation applied. Two control groups underwent an activation period without relaxation or only a single activation. One group was sham-operated. Periosteal pumping without period of activation induced gene expression in bone and bone remodeling, and following activation period enhanced bone modeling. Four test groups and control group with activation period equaled the values of bone modeling at the end-consolidation period, showing significant downregulation of Sost in the bone and periosteum compared to that in the sham group (p < 0.001 and p < 0.001, respectively). When all test groups were pooled together, plate elevation from the bony surface increased bone remodeling on day 45 of the observation period (p = 0.003). Furthermore, bone modeling was significantly affected by plate elevation on days 17 and 45 (p = 0.047 and p = 0.005, respectively) and by pumping protocol on day 31 (p = 0.042). Periosteal pumping was beneficial for increasing bone repair when the periosteum remained in contact with the underlaying bony surface during the manipulation period. Following periosteal elevation, periosteal pumping accelerated bone formation from the bony surface by the modeling process.

[Research Progress in the Regulatory Role of circRNA-miRNA Network in Bone Remodeling]. / circRNA-miRNAç½‘ç»œè°ƒæŽ§éª¨é‡å¡‘çš„ç ”ç©¶è¿›å±•.

The dynamic balance between bone formation and bone resorption is a critical process of bone remodeling. The imbalance of bone formation and bone resorption is closely associated with the occurrence and development of various bone-related diseases. Under both physiological and pathological conditions, non-coding RNAs (ncRNAs) play a crucial regulatory role in protein expression through either inhibiting mRNAs translation or promoting mRNAs degradation. Circular RNAs (circRNAs) are a type of non-linear ncRNAs that can resist the degradation of RNA exonucleases. There is accumulating evidence suggesting that circRNAs and microRNAs (miRNAs) serve as critical regulators of bone remodeling through their direct or indirect regulation of the expression of osteogenesis-related genes. Additionally, recent studies have revealed the involvement of the circRNAs-miRNAs regulatory network in the process by which mesenchymal stem cells (MSCs) differentiate towards the osteoblasts (OB) lineage and the process by which bone marrow-derived macrophages (BMDM) differentiate towards osteoclasts (OC). The circRNA-miRNA network plays an important regulatory role in the osteoblastic-osteoclastic balance of bone remodeling. Therefore, a thorough understanding of the circRNA-miRNA regulatory mechanisms will contribute to a better understanding of the regulatory mechanisms of the balance between osteoblastic and osteoclastic activities in the process of bone remodeling and the diagnosis and treatment of related diseases. Herein, we reviewed the functions of circRNA and microRNA. We also reviewed their roles in and the mechanisms of the circRNA-miRNA regulatory network in the process of bone remodeling. This review provides references and ideas for further research on the regulation of bone remodeling and the prevention and treatment of bone-related diseases.

The role of the Piezo1 channel in osteoblasts under cyclic stretching: A study on osteogenic and osteoclast factors.

OBJECTIVES: Orthodontic tooth movement is a mechanobiological reaction induced by appropriate forces, including bone remodeling. The mechanosensitive Piezo channels have been shown to contribute to bone remodeling. However, information about the pathways through which Piezo channels affects osteoblasts remains limited. Thus, we aimed to investigate the influence of Piezo1 on the osteogenic and osteoclast factors in osteoblasts under mechanical load. MATERIALS AND METHODS: Cyclic stretch (CS) experiments on MC3T3-E1 were conducted using a BioDynamic mechanical stretching device. The Piezo1 channel blocker GsMTx4 and the Piezo1 channel agonist Yoda1 were used 12 h before the application of CS. MC3T3-E1 cells were then subjected to 15% CS, and the expression of Piezo1, Piezo2, BMP-2, OCN, Runx2, RANKL, p-p65/p65, and ALP was measured using quantitative real-time polymerase chain reaction, western blot, alkaline phosphatase staining, and immunofluorescence staining. RESULTS: CS of 15% induced the highest expression of Piezo channel and osteoblast factors. Yoda1 significantly increased the CS-upregulated expression of Piezo1 and ALP activity but not Piezo2 and RANKL. GsMTx4 downregulated the CS-upregulated expression of Piezo1, Piezo2, Runx2, OCN, p-65/65, and ALP activity but could not completely reduce CS-upregulated BMP-2. CONCLUSIONS: The appropriate force is more suitable for promoting osteogenic differentiation in MC3T3-E1. The Piezo1 channel participates in osteogenic differentiation of osteoblasts through its influence on the expression of osteogenic factors like BMP-2, Runx2, and OCN and is involved in regulating osteoclasts by influencing phosphorylated p65. These results provide a foundation for further exploration of osteoblast function in orthodontic tooth movement.

Zinc finger protein 36 like 2-histone deacetylase 1 axis is involved in the bone responses to mechanical stress.

The molecular mechanism underlying the promotion of fracture healing by mechanical stimuli remains unclear. The present study aimed to investigate the role of zinc finger protein 36 like 2 (ZFP36L2)-histone deacetylase 1 (HDAC1) axis on the osteogenic responses to moderate mechanical stimulation. Appropriate stimulation of fluid shear stress (FSS) was performed on MC3T3-E1 cells transduced with ZFP36L2 and HDAC1 recombinant adenoviruses, aiming to validate the influence of mechanical stress on the expression of ZFP36L2-HDAC1 and the osteogenic differentiation and mineralization. The results showed that moderate FSS stimulation significantly upregulated the expression of ZFP36L2 in MC3T3-E1 cells (p < 0.01). The overexpression of ZFP36L1 markedly enhanced the levels of osteogenic differentiation markers, including bone morphogenetic protein 2 (BMP2), runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), Osterix, and collagen type I alpha 1 (COL1A1) (p < 0.01). ZFP36L2 accelerated the degradation of HDAC1 by specifically binding to its 3' UTR region, thereby fulfilling its function at the post-transcriptional regulatory gene level and promoting the osteogenic differentiation and mineralization fate of cells. Mechanical unloading notably diminished/elevated the expression of ZFP36L2/HDAC1, decreased bone mineral density and bone volume fraction, hindered the release of osteogenic-related factors and vascular endothelial growth factor in callus tissue (p < 0.01), and was detrimental to fracture healing. Collectively, proper stress stimulation plays a crucial role in facilitating osteogenesis through the promotion of ZFP36L2 and subsequent degradation of HDAC1. Targeting ZFP36L2-HDAC1 axis may provide promising insights to enhance bone defect healing.

Unraveling the influence of channel size and shape in 3D printed ceramic scaffolds on osteogenesis.

Bone has the capacity to regenerate itself for relatively small defects; however, this regenerative capacity is diminished in critical-size bone defects. The development of synthetic materials has risen as a distinct strategy to address this challenge. Effective synthetic materials to have emerged in recent years are bioceramic implants, which are biocompatible and highly bioactive. Yet nothing suitable for the repair of large bone defects has made the transition from laboratory to clinic. The clinical success of bioceramics has been shown to depend not only on the scaffold's intrinsic material properties but also on its internal porous geometry. This study aimed to systematically explore the implications of varying channel size, shape, and curvature in tissue scaffolds on in vivo bone regeneration outcomes. 3D printed bioceramic scaffolds with varying channel sizes (0.3 mm to 1.5 mm), shapes (circular vs rectangular), and curvatures (concave vs convex) were implanted in rabbit femoral defects for 8 weeks, followed by histological evaluation. We demonstrated that circular channel sizes of around 0.9 mm diameter significantly enhanced bone formation, compared to channel with diameters of 0.3 mm and 1.5 mm. Interestingly, varying channel shapes (rectangular vs circular) had no significant effect on the volume of newly formed bone. Furthermore, the present study systematically demonstrated the beneficial effect of concave surfaces on bone tissue growth in vivo, reinforcing previous in silico and in vitro findings. This study demonstrates that optimizing architectural configurations within ceramic scaffolds is crucial in enhancing bone regeneration outcomes. STATEMENT OF SIGNIFICANCE: Despite the explosion of work on developing synthetic scaffolds to repair bone defects, the amount of new bone formed by scaffolds in vivo remains suboptimal. Recent studies have illuminated the pivotal role of scaffolds' internal architecture in osteogenesis. However, these investigations have mostly remained confined to in silico and in vitro experiments. Among the in vivo studies conducted, there has been a lack of systematic analysis of individual architectural features. Herein, we utilized bioceramic 3D printing to conduct a systematic exploration of the effects of channel size, shape, and curvature on bone formation in vivo. Our results demonstrate the significant influence of channel size and curvature on in vivo outcomes. These findings provide invaluable insights into the design of more effective bone scaffolds.

Mechanosensitive protein polycystin-1 promotes periosteal stem/progenitor cells osteochondral differentiation in fracture healing.

Background: Mechanical forces are indispensable for bone healing, disruption of which is recognized as a contributing cause to nonunion or delayed union. However, the underlying mechanism of mechanical regulation of fracture healing is elusive. Methods: We used the lineage-tracing mouse model, conditional knockout depletion mouse model, hindlimb unloading model and single-cell RNA sequencing to analyze the crucial roles of mechanosensitive protein polycystin-1 (PC1, Pkd1) promotes periosteal stem/progenitor cells (PSPCs) osteochondral differentiation in fracture healing. Results: Our results showed that cathepsin (Ctsk)-positive PSPCs are fracture-responsive and mechanosensitive and can differentiate into osteoblasts and chondrocytes during fracture repair. We found that polycystin-1 declines markedly in PSPCs with mechanical unloading while increasing in response to mechanical stimulus. Mice with conditional depletion of Pkd1 in Ctsk+ PSPCs show impaired osteochondrogenesis, reduced cortical bone formation, delayed fracture healing, and diminished responsiveness to mechanical unloading. Mechanistically, PC1 facilitates nuclear translocation of transcriptional coactivator TAZ via PC1 C-terminal tail cleavage, enhancing osteochondral differentiation potential of PSPCs. Pharmacological intervention of the PC1-TAZ axis and promotion of TAZ nuclear translocation using Zinc01442821 enhances fracture healing and alleviates delayed union or nonunion induced by mechanical unloading. Conclusion: Our study reveals that Ctsk+ PSPCs within the callus can sense mechanical forces through the PC1-TAZ axis, targeting which represents great therapeutic potential for delayed fracture union or nonunion.

Strategies for Improving Impaired Osseointegration in Compromised Animal Models.

Implant osseointegration is reduced in patients with systemic conditions that compromise bone quality, such as osteoporosis, disuse syndrome, and type 2 diabetes. Studies using rodent models designed to mimic these compromised conditions demonstrated reduced bone-to-implant contact (BIC) or a decline in bone mineral density. These adverse effects are a consequence of disrupted intercellular communication. A variety of approaches have been developed to compensate for the altered microenvironment inherent in compromised conditions, including the use of biologics and implant surface modification. Chemical and physical modification of surface properties at the microscale, mesoscale, and nanoscale levels to closely resemble the surface topography of osteoclast resorption pits found in bone has proven to be a highly effective strategy for improving implant osseointegration. The addition of hydrophilicity to the surface further enhances osteoblast response at the bone-implant interface. These surface modifications, applied either alone or in combination, improve osseointegration by increasing proliferation and osteoblastic differentiation of osteoprogenitor cells and enhancing angiogenesis while modulating osteoclast activity to achieve net new bone formation, although the specific effects vary with surface treatment. In addition to direct effects on surface-attached cells, the communication between bone marrow stromal cells and immunomodulatory cells is sensitive to these surface properties. This article reports on the advances in titanium surface modifications, alone and in combination with novel therapeutics in animal models of human disease affecting bone quality. It offers clinically translatable perspectives for clinicians to consider when using different surface modification strategies to improve long-term implant performance in compromised patients. This review supports the use of surface modifications, bioactive coatings, and localized therapeutics as pragmatic approaches to improve BIC and enhance osteogenic activity from both structural and molecular standpoints.

p-Smad3 differentially regulates the cytological behavior of osteoclasts before and after osteoblasts maturation.

BACKGROUND: A series of previous investigations have revealed that p-Smad3 plays a facilitative role in the differentiation and maturation of osteoblasts, while also regulating the expression of certain intercellular communication factors. However, the effects of p-Smad3 in osteoblasts before and after maturation on the proliferation, migration, differentiation, apoptosis and other cellular behaviors of osteoclasts have not been reported. METHODS: MC3T3-E1 cells were cultured in osteogenic induction medium for varying durations, After that, the corresponding conditioned medium was collected and the osteoclast lineage cells were treated. To elucidate the regulatory role of p-Smad3 within osteoblasts, we applied the activator TGF-ß1 and inhibitor SIS3 to immature and mature osteoblasts and collected corresponding conditioned media for osteoclast intervention. RESULTS: We observed an elevation of p-Smad3 and Smad3 during the early stage of osteoblast differentiation, followed by a decline in the later stage. we discovered that as osteoblasts mature, their conditioned media inhibit osteoclasts differentiation and the osteoclast-coupled osteogenic effect. However, it promotes apoptosis in osteoclasts and the angiogenesis coupled with osteoclasts. p-Smad3 in immature osteoblasts, through paracrine effects, promotes the migration, differentiation, and osteoclast-coupled osteogenic effects of osteoclast lineage cells. For mature osteoblasts, p-Smad3 facilitates osteoclast apoptosis and the angiogenesis coupled with osteoclasts. CONCLUSIONS: As pre-osteoblasts undergo maturation, p-Smad3 mediated a paracrine effect that transitions osteoclast cellular behaviors from inducing differentiation and stimulating bone formation to promoting apoptosis and coupling angiogenesis.