Persistent Mesodermal Differentiation Capability of Bone Marrow MSCs Isolated from Aging Patients with Low-Energy Traumatic Hip Fracture and Osteoporosis: A Clinical Evidence.

A low-energy hit, such as a slight fall from a bed, results in a bone fracture, especially in the hip, which is a life-threatening risk for the older adult and a heavy burden for the social economy. Patients with low-energy traumatic bone fractures usually suffer a higher level of bony catabolism accompanied by osteoporosis. Bone marrow-derived stem cells (BMSCs) are critical in osteogenesis, leading to metabolic homeostasis in the healthy bony microenvironment. However, whether the BMSCs derived from the patients who suffered osteoporosis and low-energy traumatic hip fractures preserve a sustained mesodermal differentiation capability, especially in osteogenesis, is yet to be explored in a clinical setting. Therefore, we aimed to collect BMSCs from clinical hip fracture patients with osteoporosis, followed by osteogenic differentiation comparison with BMSCs from healthy young donors. The CD markers identification, cytokines examination, and adipogenic differentiation were also evaluated. The data reveal that BMSCs collected from elderly osteoporotic patients secreted approximately 122.8 pg/mL interleukin 6 (IL-6) and 180.6 pg/mL vascular endothelial growth factor (VEGF), but no PDGF-BB, IL-1b, TGF-b1, IGF-1, or TNF-α secretion. The CD markers and osteogenic and adipogenic differentiation capability in BMSCs from these elderly osteoporotic patients and healthy young donors are equivalent and compliant with the standards defined by the International Society of Cell Therapy (ISCT). Collectively, our data suggest that the elderly osteoporotic patients-derived BMSCs hold equivalent differentiation and proliferation capability and intact surface markers identical to BMSCs collected from healthy youth and are available for clinical cell therapy.

Adipose-derived stem cell-based optimization strategies for musculoskeletal regeneration: recent advances and perspectives.

Musculoskeletal disorders are the leading causes of physical disabilities worldwide. The poor self-repair capacity of musculoskeletal tissues and the absence of effective therapies have driven the development of novel bioengineering-based therapeutic approaches. Adipose-derived stem cell (ADSC)-based therapies are being explored as new regenerative strategies for the repair and regeneration of bone, cartilage, and tendon owing to the accessibility, multipotency, and active paracrine activity of ADSCs. In this review, recent advances in ADSCs and their optimization strategies, including ADSC-derived exosomes (ADSC-Exos), biomaterials, and genetic modifications, are summarized. Furthermore, the preclinical and clinical applications of ADSCs and ADSC-Exos, either alone or in combination with growth factors or biomaterials or in genetically modified forms, for bone, cartilage, and tendon regeneration are reviewed. ADSC-based optimization strategies hold promise for the management of multiple types of musculoskeletal injuries. The timely summary and highlights provided here could offer guidance for further investigations to accelerate the development and clinical application of ADSC-based therapies in musculoskeletal regeneration.

Metformin-loaded PLGA microspheres combined with an in situ-formed injectable SA/BG hydrogel alleviate rotator cuff muscle degeneration.

Rotator cuff tears are a prevalent musculoskeletal problem that affect many individuals and may result in substantial social and health-related expenses. Moreover, the muscular fat infiltration and dystrophy associated with rotator cuff tears have been persistent challenges in rotator cuff surgical repair and postoperative rehabilitation. In this study, an in situ-formed injectable sodium alginate (SA) and bioglass (BG) hydrogel consisting of poly (lactic-co-glycolic acid) (PLGA) microspheres containing metformin (SA/BG-PLGA-Met) was developed for the prevention of muscular fat infiltration and dystrophy. Metformin and silicon ions were slowly released by the combined hydrogel, resulting in long-term biological effects. Moreover, the hydrogel displayed excellent degradability and biocompatibility. Extracts of SA/BG-PLGA-Met inhibited the adipogenesis of 3T3-L1 cells and stimulated the myogenic differentiation of C2C12 cells in vitro. In a mouse model of rotator cuff degeneration, the SA/BG-PLGA-Met hydrogel inhibited fat infiltration and dystrophy of the supraspinatus muscle. Overall, the SA/BG-PLGA-Met hydrogel, as a novel biomaterial, has great clinical potential for preventing rotator cuff muscle fat infiltration and atrophy.

Macroporous Granular Hydrogels Functionalized with Aligned Architecture and Small Extracellular Vesicles Stimulate Osteoporotic Tendon-To-Bone Healing.

Osteoporotic tendon-to-bone healing (TBH) after rotator cuff repair (RCR) is a significant orthopedic challenge. Considering the aligned architecture of the tendon, inflammatory microenvironment at the injury site, and the need for endogenous cell/tissue infiltration, there is an imminent need for an ideal scaffold to promote TBH that has aligned architecture, ability to modulate inflammation, and macroporous structure. Herein, a novel macroporous hydrogel comprising sodium alginate/hyaluronic acid/small extracellular vesicles from adipose-derived stem cells (sEVs) (MHA-sEVs) with aligned architecture and immunomodulatory ability is fabricated. When implanted subcutaneously, MHA-sEVs significantly improve cell infiltration and tissue integration through its macroporous structure. When applied to the osteoporotic RCR model, MHA-sEVs promote TBH by improving tendon repair through macroporous aligned architecture while enhancing bone regeneration by modulating inflammation. Notably, the biomechanical strength of MHA-sEVs is approximately two times higher than the control group, indicating great potential in reducing postoperative retear rates. Further cell-hydrogel interaction studies reveal that the alignment of microfiber gels in MHA-sEVs induces tenogenic differentiation of tendon-derived stem cells, while sEVs improve mitochondrial dysfunction in M1 macrophages (Mφ) and inhibit Mφ polarization toward M1 via nuclear factor-kappaB (NF-κb) signaling pathway. Taken together, MHA-sEVs provide a promising strategy for future clinical application in promoting osteoporotic TBH.

Potential of thermoresponsive hydrogel as an alternative therapy for rat knee osteoarthritis.

Osteoarthritis is a degenerative condition that is highly prevalent and primarily affects the joints. The knee is the most commonly affected site, impacting the lives of over 300 million individuals worldwide. This study presents a potential solution to address the unmet need for a minimally invasive technique in the treatment of osteoarthritis: a biocompatible, injectable, and thermoresponsive hydrogel. In comparison to commercially available products such as lyophilized platelets, dextrose, and triamcinolone, the thermoresponsive hydrogel exhibits significantly superior performance in dynamic behaviors, including print area, stability, and step cycle, when tested on rats with knee osteoarthritis. However, it demonstrates similar treatment efficacy to these products in static behaviors, as observed through histopathological and immunohistochemical analysis. Therefore, the thermoresponsive hydrogel holds promise as an effective alternative therapy for osteoarthritis. Moreover, by blending the hydrogel with drugs, controlled and sustained release can be achieved, thereby facilitating the long-term management of osteoarthritis symptoms.

Cryopreserved Adipose-Derived Stem Cell Sheets: An Off-the-Shelf Scaffold for Augmenting Tendon-to-Bone Healing in a Rabbit Model of Chronic Rotator Cuff Tear.

BACKGROUND: Adipose-derived stem cell (ADSC) sheets have been shown to promote tendon-to-bone healing. However, conventional laboratory preparation methods for ADSC sheets are time-consuming and risky, which precludes their diverse clinical applications. PURPOSE: To explore the utility of off-the-shelf cryopreserved ADSC sheets (c-ADSC sheets) for rotator cuff tendon-to-bone healing. STUDY DESIGN: Controlled laboratory study. METHODS: The ADSC sheets were cryopreserved and thawed for live/dead double staining, TdT-mediated dUTP Nick-End Labeling (TUNEL) staining, scanning electron microscopy observation, and biomechanical testing. Clone formation, proliferative capacity, and multilineage differentiation of ADSCs within the c-ADSC sheets were assayed to explore the effect of cryopreservation on stem cell properties. A total of 67 rabbits were randomly divided into 4 groups: normal group (without supraspinatus tendon tears; n = 7), control group (repair alone; n = 20), fresh ADSC (f-ADSC) sheet group (repair; n = 20), and c-ADSC sheet group (repair; n = 20). Rabbit bilateral supraspinatus tendon tears were induced to establish a chronic rotator cuff tear model. Gross observation, micro-computed tomography analysis, histological or immunohistochemical tests, and biomechanical tests were conducted at 6 and 12 weeks after repair. RESULTS: No significant impairment was seen in the cell viability, morphology, and mechanical properties of c-ADSC sheets when compared with f-ADSC sheets. The stem cell properties of ADSC sheets also were preserved by cryopreservation. At 6 and 12 weeks after the repair, the f-ADSC and c-ADSC sheet groups showed superior bone regeneration, higher histological scores, larger fibrocartilage areas, more mature collagen, and better biomechanical results compared with the control group. No obvious difference was seen between the f-ADSC and c-ADSC sheet groups in terms of bone regeneration, histological score, fibrocartilage formation, and biomechanical tests. CONCLUSION: c-ADSC sheets, an off-the-shelf scaffold with a high potential for clinical translational application, can effectively promote rotator cuff tendon-to-bone healing. CLINICAL RELEVANCE: Programmed cryopreservation of ADSC sheets is an efficient off-the-shelf scaffold for rotator cuff tendon-to-bone healing.

Arthroscopic Autologous Iliac Crest Grafting Results in Similar Outcomes and Low Recurrence Compared to Remplissage Plus Bankart Repair for Anterior Shoulder Instability With Bipolar Bone Defects.

PURPOSE: To compare the functional outcomes, range of motion (ROM), recurrence rates, and complication rates of arthroscopic autologous iliac crest grafting (AICG) and Remplissage plus Bankart repair (RB) for anterior shoulder instability with bipolar bone defects. METHODS: This study enrolled patients undergoing arthroscopic AICG or RB with 13.5-25% glenoid bone defect combined with Hill-Sachs lesion between January 2013 and April 2020, who had a minimum 2-year follow-up. Patient-reported outcomes were evaluated by Subjective Shoulder Value (SSV), Oxford Shoulder Instability Score (OSIS), Rowe score, Constant score, and visual analog scale (VAS) for pain. Active ROM, return to sports, recurrence, self-reported apprehension, and complications were recorded. RESULTS: This study included 60 patients, including 28 AICG (Group A) and 32 RB (Group R). Mean glenoid bone defect was similar (17.7% ± 3.1% vs 16.6% ± 2.4%; P = .122). Both groups showed significant postoperative improvement in Rowe score, SSV, OSIS, and Constant score. No significant difference was found in postoperative Rowe Score (87.7 vs 85.2; P = .198). A total of 20/28 (71.4%) patients in Group A versus 26/32 (81.3%) patients in Group R met the Patient Acceptable Symptomatic State determined by VAS pain score (P = .370). Both groups showed high return-to-sports rates (67.8% vs 71.8%; P = .735) and slightly decreased ROM. There were two cases of recurrence in Group A versus one in Group R (P = .594). Group R had insignificantly higher positive self-reported apprehension rate (40.6% vs 17.9%; P = .055). CONCLUSIONS: For anterior shoulder instability with bipolar bone defects, both arthroscopic AICG and RB can result in satisfactory clinical outcomes, good postoperative ROM, and low recurrence and complication rates. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

The recombinant human fibroblast growth factor-18 (sprifermin) improves tendon-to-bone healing by promoting chondrogenesis in a rat rotator cuff repair model.

BACKGROUND: Rotator cuff healing is improved by reconstructing the fibrocartilaginous structure of the tendon-to-bone enthesis. Fibroblast growth factor (FGF)-18 (sprifermin) is a well-known growth factor that improves articular cartilage repair via its anabolic effect. This study aimed to investigate the effect of recombinant human FGF-18 (rhFGF-18) on the chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) in vitro and tendon-to-bone healing in a rat model of rotator cuff repair. METHODS: Histological and reverse transcription-quantitative real-time polymerase chain reaction analyses of chondral pellets cultured with different concentrations of rhFGF-18 were performed. Bilateral detachment and repair of the supraspinatus tendon were performed on rats. The rats were administered 0.2 mL of sodium alginate (SA) hydrogel with (rhFGF-18/SA group, n = 12) or without (SA group, n = 12) 20 µg of rhFGF-18 into the repaired side. The simple repair group (n = 12) served as a control. At 4 and 8 weeks after surgery, histological analysis and biomechanical tests were performed. RESULTS: After chondrogenesis induction, compared with the control group, 10 ng/mL of rhFGF-18 increased pellet volume significantly (P = .002), with improved histological staining. It was noted that 10 ng/mL of rhFGF-18 upregulated the mRNA expression (relative ratio to control) of aggrecan (2.59 ± 0.29, P < .001), SRY-box transcription factor 9 (1.88 ± 0.05, P < .001), and type II collagen (1.46 ± 0.18, P = .009). At 4 and 8 weeks after surgery, more fibrocartilage and cartilaginous extracellular matrix was observed in rhFGF-18/SA-treated rats. The semiquantitative data from picrosirius red staining test were 31.1 ± 4.5 vs. 61.2 ± 4.1 at 4 weeks (P < .001) and 61.5 ± 2.8 vs. 80.5 ± 10.5 at 8 weeks (P = .002) (control vs. rhFGF-18/SA). Ultimate failure load (25.42 ± 3.61 N vs. 18.87 ± 2.71 N at 4 weeks and 28.63 ± 5.22 N vs. 22.15 ± 3.11 N at 8 weeks; P = .006 and P = .03, respectively) and stiffness (18.49 ± 1.38 N/mm vs. 14.48 ± 2.01 N/mm at 8 weeks, P = .01) were higher in the rhFGF-18/SA group than in the control group. CONCLUSION: rhFGF-18 promoted chondrogenesis in the hBMSCs in vitro. rhFGF-18/SA improved tendon-to-bone healing in the rats by promoting regeneration of the fibrocartilage enthesis. rhFGF-18 (sprifermin) may be beneficial in improving tendon-to-bone healing after rotator cuff repair.

Amorphous calcium phosphate nanoparticles using adenosine triphosphate as an organic phosphorus source for promoting tendon-bone healing.

BACKGROUND: Rotator cuff tear (RCT) is a common problem of the musculoskeletal system. With the advantage of promoting bone formation, calcium phosphate materials have been widely used to augment tendon-bone healing. However, only enhancing bone regeneration may be not enough for improving tendon-bone healing. Angiogenesis is another fundamental factor required for tendon-bone healing. Therefore, it's necessary to develop a convenient and reliable method to promote osteogenesis and angiogenesis simultaneously, thereby effectively promoting tendon-bone healing. METHODS: The amorphous calcium phosphate (ACP) nanoparticles with dual biological activities of osteogenesis and angiogenesis were prepared by a simple low-temperature aqueous solution method using adenosine triphosphate (ATP) as an organic phosphorus source. The activities of osteogenesis and angiogenesis and the effect on the tendon-bone healing of ACP nanoparticles were tested in vitro and in a rat model of acute RCT. RESULTS: The ACP nanoparticles with a diameter of tens of nanometers were rich in bioactive adenosine. In vitro, we confirmed that ACP nanoparticles could enhance osteogenesis and angiogenesis. In vivo, radiological and histological evaluations demonstrated that ACP nanoparticles could enhance bone and blood vessels formation at the tendon-bone junction. Biomechanical testing showed that ACP nanoparticles improved the biomechanical strength of the tendon-bone junction and ultimately promoted tendon-bone healing of rotator cuff. CONCLUSIONS: We successfully confirmed that ACP nanoparticles could promote tendon-bone healing. ACP nanoparticles are a promising biological nanomaterial in augmenting tendon-bone healing.

Adipose Stem Cell-Derived Exosomes Ameliorate Chronic Rotator Cuff Tendinopathy by Regulating Macrophage Polarization: From a Mouse Model to a Study in Human Tissue.

BACKGROUND: Chronic rotator cuff (RC) tendinopathy is one of the most prevalent causes of shoulder pain. Growing evidence suggests that macrophages play a significant role in the proinflammatory response, resolution of inflammation, and tissue healing of tendinopathy. In particular, enhancement of M2 macrophage (M2φ) activity contributes to the accelerated healing of tendinopathy. Therefore, a treatment that enhances M2φ polarization would be useful for patients with this common musculoskeletal disorder. PURPOSE: To investigate whether adipose stem cell-derived exosomes (ASC-Exos) enhance M2φ polarization and ameliorate chronic RC tendinopathy. STUDY DESIGN: Controlled laboratory study. METHODS: First, we compared the effects of ASC-Exos on polarization of mouse bone marrow-derived macrophages between a classically activated phenotype (M1φ) and an alternatively activated phenotype (M2φ) in vitro. In total, 72 C57BL/6 mice were assigned to normal cage activity (n = 24) or 5 weeks of treadmill overuse (n = 48). The supraspinatus tendon of each treadmill overuse mouse was treated with ASC-Exos (n = 24) or saline (n = 24). Histological and biomechanical outcomes were assessed 4 weeks after treatment. Finally, tissue samples from human patients with RC tendinopathy were obtained to assay the effect of ASC-Exos on the M1φ/M2φ balance in tissue-resident macrophages. RESULTS: ASC-Exos inhibited M1φ polarization and augmented M2φ polarization in vitro and in vivo. Mice in the ASC-Exos group showed less severe pathological changes than those in the saline group, including less cellular infiltration, disorganization of collagen, and ground substance deposition. The modified Bonar score of the ASC-Exos group (mean ± SD, 7.68 ± 1.03) was significantly lower than that of the saline group (9.81 ± 0.96; P < .05). Furthermore, the maximum failure load was significantly higher in the ASC-Exos group than in the saline group (4.23 ± 0.66 N vs 3.86 ± 0.65 N; P < .05), as was stiffness (3.38 ± 0.34 N/m vs 2.68 ± 0.49 N/m; P < .05). CONCLUSION: ASC-Exos-mediated polarization balance of M1φ/M2φ contributes to the amelioration of chronic RC tendinopathy. Regulation of the M1φ/M2φ balance could be a new target for the treatment of chronic RC tendinopathy. CLINICAL RELEVANCE: Administration of ASC-Exos is a cell-free approach that may become a novel treatment option for chronic RC tendinopathy and should be explored further.

Construction of a Novel Female Sterility System for Hybrid Rice.

The main constraints of current hybrid rice technology using male sterility (MS) are the low yield and high labor costs of hybrid rice seed (HRS) production. Therefore, there is an urgent need for innovative new hybrid rice technology. Fortunately, we discovered a unique spontaneous sporophytic female-sterile rice mutant controlled by a single recessive locus in the nucleus. Because female-sterile mutant lines cannot produce any selfed-seeds but their pollen has totally normal functions, female sterility (FS) lines may be considered ideal pollen donors to replace the female-fertile pollen donor parent lines currently used in the HRS production. In this study, a genetically engineered FS-based system was constructed to propagate a pure transgene-free FS line using a bentazon herbicide screening. Additionally, the ability of the FS + MS (FM)-line system, with mixed plantings of FS and MS lines, to produce HRS was tested. The pilot field experiment results showed that HRS of the FM-line system was more efficient compared with the conventional FS to MS strip planting control mode. Thus, this study provides new insights into genetic engineering technology and a promising strategy for the utilization of FS in hybrid rice.

Adipose Stem Cell-Derived Exosomes Decrease Fatty Infiltration and Enhance Rotator Cuff Healing in a Rabbit Model of Chronic Tears.

BACKGROUND: Fatty infiltration and poor tendon-bone healing in chronic rotator cuff tears (RCTs) are associated with unsatisfactory prognosis. Adipose stem cell-derived exosomes (ASC-Exos), having multiple biological effects, can prevent muscle degeneration in acute RCTs. However, the effects of ASC-Exos on fatty infiltration and tendon-bone healing in chronic RCTs remain unknown. PURPOSE: To study the effects of ASC-Exos on fatty infiltration and tendon-bone healing in a chronic RCT rabbit model. STUDY DESIGN: Controlled laboratory study. METHODS: At week 0, we randomly allocated 35 rabbits to receive sham surgery (14 rabbits) or establish a bilateral RCT model (21 rabbits, detachment of the supraspinatus tendon). At week 6, a total of 7 rabbits received sham surgery, and 7 rabbits with RCT were sacrificed for fatty infiltration assay. The remaining 14 rabbits with bilateral RCTs were randomly assigned to a saline group (7 rabbits that received local saline injection and rotator cuff repair) or an ASC-Exos group (7 rabbits that received local ASC-Exos injection and rotator cuff repair). At week 18, all rabbits were sacrificed for histological examination and biomechanical testing. RESULTS: At week 18, the ASC-Exos group showed significantly lower fatty infiltration (14.01% ± 2.85%) compared with the saline group (21.79% ± 3.07%) (P < .001), and no statistical difference compared with the time of repair (10.88% ± 2.64%) (P = .127). For tendon-bone healing, the ASC-Exos group showed a higher histological score and more newly regenerated fibrocartilage at the repair site than did the saline group. Regarding biomechanical testing, the ASC-Exos group showed significantly higher ultimate load to failure, stiffness, and stress than the saline group. CONCLUSION: Local injection of ASC-Exos in chronic RCTs at the time of repair could prevent the progress of fatty infiltration, promote tendon-bone healing, and improve biomechanical properties. CLINICAL RELEVANCE: ASC-Exos injection may be used as a cell-free adjunctive therapy to inhibit fatty infiltration and improve rotator cuff healing in the repair of chronic RCTs.

Updated Hourly Emissions Factors for Chinese Power Plants Showing the Impact of Widespread Ultralow Emissions Technology Deployment.

Nationwide severe air pollution has prompted China to mandate the adoption of ultralow emissions (ULE) control technologies at all of its coal-fired power plants by 2020. This process has accelerated greatly since 2014 and, combined with operational adjustments related to overcapacity, has reduced the emissions of nitrogen oxides (NO x), sulfur dioxide (SO2), and particulate matter (PM). Yet the quantitative understanding of ULE benefits is poor. Using detailed emissions data from 38 units at 17 power plants, corresponding to 10 combinations of ULE technologies representative of the Chinese power sector, we show that emissions factors for NO x, SO2, and PM are up to 1-2 orders of magnitude lower after ULE retrofitting. The effectiveness in cutting emissions shows a large spread across the various ULE technology combinations, providing an opportunity to choose the most efficient, economically viable technology (or a combination of technologies) in the future. The temporal variations in emissions at hourly resolution reveal the effects of power plant load on emissions, an increasingly important factor given that power plants are not operated at full capacity. These data will be useful in efforts to understand the evolving state of air quality in China and can also provide a basis for benchmarking state-of-the-art air pollution control equipment globally.

Porous Nanocomposite Comprising Ultralong Hydroxyapatite Nanowires Decorated with Zinc-Containing Nanoparticles and Chitosan: Synthesis and Application in Bone Defect Repair.

Hydroxyapatite nanowires exhibit a great potential in biomedical applications owing to their high specific surface area, high flexibility, excellent mechanical properties, and similarity to mineralized collagen fibrils of natural bone. In this work, zinc-containing nanoparticle-decorated ultralong hydroxyapatite nanowires (Zn-UHANWs) with a hierarchical nanostructure have been synthesized by a one-step solvothermal method. The highly flexible Zn-UHANWs exhibit a hierarchical rough surface and enhanced specific surface area as compared with ultralong hydroxyapatite nanowires (UHANWs). To evaluate the potential application of Zn-UHANWs in bone regeneration, the biomimetic Zn-UHANWs/chitosan (CS) (Zn-UHANWs/CS) composite porous scaffold with 80 wt % Zn-UHANWs was prepared by incorporating Zn-UHANWs into the chitosan matrix by the freeze-drying process. The as-prepared Zn-UHANWs/CS composite porous scaffold exhibits enhanced mechanical properties, highly porous structure, and excellent water retention capacity. In addition, the Zn-UHANWs/CS porous scaffold has a good biodegradability with the sustainable release of Zn, Ca, and P elements in aqueous solution. More importantly, the Zn-UHANWs/CS porous scaffold can promote the osteogenic differentiation of rat bone marrow derived mesenchymal stem cells and facilitate in vivo bone regeneration as compared with the pure CS porous scaffold or UHANWs/CS porous scaffold. Thus, both the Zn-UHANWs and Zn-UHANWs/CS porous scaffold developed in this work are promising for application in bone defect repair.

Hydroxyapatite Nanowire@Magnesium Silicate Core-Shell Hierarchical Nanocomposite: Synthesis and Application in Bone Regeneration.

Multifunctional biomaterials that simultaneously combine high biocompatibility, biodegradability, and bioactivity are promising for applications in various biomedical fields such as bone defect repair and drug delivery. Herein, the synthesis of hydroxyapatite nanowire@magnesium silicate nanosheets (HANW@MS) core-shell porous hierarchical nanocomposites (nanobrushes) is reported. The morphology of the magnesium silicate (MS) shell can be controlled by simply varying the solvothermal temperature and the amount of Mg2+ ions. Compared with hydroxyapatite nanowires (HANWs), the HANW@MS core-shell porous hierarchical nanobrushes exhibit remarkably increased specific surface area and pore volume, endowing the HANW@MS core-shell porous hierarchical nanobrushes with high-performance drug loading and sustained release. Moreover, the porous scaffold of HANW@MS/chitosan (HANW@MS/CS) is prepared by incorporating the HANW@MS core-shell porous hierarchical nanobrushes into the chitosan (CS) matrix. The HANW@MS/CS porous scaffold not only promotes the attachment and growth of rat bone marrow derived mesenchymal stem cells (rBMSCs), but also induces the expression of osteogenic differentiation related genes and the vascular endothelial growth factor (VEGF) gene of rBMSCs. Furthermore, the HANW@MS/CS porous scaffold can obviously stimulate in vivo bone regeneration, owing to its high bioactive performance on the osteogenic differentiation of rBMSCs and in vivo angiogenesis. Since Ca, Mg, Si, and P elements are essential in human bone tissue, HANW@MS core-shell porous hierarchical nanobrushes with multifunctional properties are expected to be promising for various biomedical applications such as bone defect repair and drug delivery.

Evaluation of zinc-doped mesoporous hydroxyapatite microspheres for the construction of a novel biomimetic scaffold optimized for bone augmentation.

Biomaterials with high osteogenic activity are desirable for sufficient healing of bone defects resulting from trauma, tumor, infection, and congenital abnormalities. Synthetic materials mimicking the structure and composition of human trabecular bone are of considerable potential in bone augmentation. In the present study, a zinc (Zn)-doped mesoporous hydroxyapatite microspheres (Zn-MHMs)/collagen scaffold (Zn-MHMs/Coll) was developed through a lyophilization fabrication process and designed to mimic the trabecular bone. The Zn-MHMs were synthesized through a microwave-hydrothermal method by using creatine phosphate as an organic phosphorus source. Zn-MHMs that consist of hydroxyapatite nanosheets showed relatively uniform spherical morphology, mesoporous hollow structure, high specific surface area, and homogeneous Zn distribution. They were additionally investigated as a drug nanocarrier, which was efficient in drug delivery and presented a pH-responsive drug release behavior. Furthermore, they were incorporated into the collagen matrix to construct a biomimetic scaffold optimized for bone tissue regeneration. The Zn-MHMs/Coll scaffolds showed an interconnected pore structure in the range of 100-300 µm and a sustained release of Zn ions. More importantly, the Zn-MHMs/Coll scaffolds could enhance the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells. Finally, the bone defect repair results of critical-sized femoral condyle defect rat model demonstrated that the Zn-MHMs/Coll scaffolds could enhance bone regeneration compared with the Coll or MHMs/Coll scaffolds. The results suggest that the biomimetic Zn-MHMs/Coll scaffolds may be of enormous potential in bone repair and regeneration.

Enhanced osteogenesis and angiogenesis by mesoporous hydroxyapatite microspheres-derived simvastatin sustained release system for superior bone regeneration.

Biomaterials with both excellent osteogenic and angiogenic activities are desirable to repair massive bone defects. In this study, simvastatin with both osteogenic and angiogenic activities was incorporated into the mesoporous hydroxyapatite microspheres (MHMs) synthesized through a microwave-assisted hydrothermal method using fructose 1,6-bisphosphate trisodium salt (FBP) as an organic phosphorous source. The effects of the simvastatin-loaded MHMs (S-MHMs) on the osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) and angiogenesis in EA.hy926 cells were investigated. The results showed that the S-MHMs not only enhanced the expression of osteogenic markers in rBMSCs but also promoted the migration and tube formation of EA.hy926 cells. Furthermore, the S-MHMs were incorporated into collagen matrix to construct a novel S-MHMs/collagen composite scaffold. With the aid of MHMs, the water-insoluble simvastatin was homogenously incorporated into the hydrophilic collagen matrix and presented a sustained release profile. In vivo experiments showed that the S-MHMs/collagen scaffolds enhanced the bone regeneration and neovascularization simultaneously. These results demonstrated that the water-insoluble simvastatin could be incorporated into the MHMs and maintained its biological activities, more importantly, the S-MHMs/collagen scaffolds fabricated in this study are of immense potential in bone defect repair by enhancing osteogenesis and angiogenesis simultaneously.

Strontium-Doped Amorphous Calcium Phosphate Porous Microspheres Synthesized through a Microwave-Hydrothermal Method Using Fructose 1,6-Bisphosphate as an Organic Phosphorus Source: Application in Drug Delivery and Enhanced Bone Regeneration.

Nanostructured calcium phosphate porous microspheres are of great potential in drug delivery and bone regeneration due to their large specific surface area, biocompatibility, and similarity to inorganic component of osseous tissue. In this work, strontium (Sr)-doped amorphous calcium phosphate porous microspheres (SrAPMs) were synthesized through a microwave-hydrothermal method using fructose 1,6-bisphosphate trisodium salt as the source of phosphate ions. The SrAPMs showed a mesoporous structure and a relatively high specific area. Compared with the hydroxyapatite nanorods prepared by using Na2HPO4·12H2O as the phosphorus source, the SrAPMs with a higher specific surface area were more effective in drug loading using vancomycin as the antiobiotics of choice and consequently having a higher antibacterial efficiency both on agar plates and in broths. Furthermore, to assess the potential application of SrAPMs in bone defect repair, a novel biomimetic bone tissue-engineering scaffold consisting of collagen (Coll) and SrAPMs was constructed using a freeze-drying fabrication process. Incorporation of the SrAPMs not only improved the mechanical properties, but also enhanced the osteogenesis of rat bone marrow mesenchymal stem cells. The in vivo experiments demonstrated that the SrAPMs/Coll scaffolds remarkably enhanced new bone formation compared with the Coll and APMs/Coll scaffolds in a rat critical-sized calvarial defect model at 8 weeks postimplantation. In summary, SrAPMs developed in this work are promising as antibiotic carriers and may encourage bone formation when combined with collagen.

Copper-doped mesoporous hydroxyapatite microspheres synthesized by a microwave-hydrothermal method using creatine phosphate as an organic phosphorus source: application in drug delivery and enhanced bone regeneration.

The development of multifunctional biomaterials with drug delivery ability, and pro-osteogenic and pro-angiogenic activities has garnered increasing interest in the field of regenerative medicine. In the present study, hypoxia-mimicking copper (Cu)-doped mesoporous hydroxyapatite (HAP) microspheres (Cu-MHMs) were successfully synthesized through a microwave-hydrothermal method by using creatine phosphate as an organic phosphorus source. The Cu-MHMs doped with 0.2, 0.5 and 1 mol% Cu were prepared. The Cu-MHMs consisting of HAP nanorods or nanosheets exhibited a hierarchically mesoporous hollow structure and a high specific surface area. Then the Cu-MHMs were investigated as a drug nanocarrier using doxorubicin hydrochloride (DOX) as a model drug. The Cu-MHMs showed a relatively high drug-loading capacity and a pH-responsive drug release behavior. Furthermore, the Cu-MHMs were incorporated into a chitosan (CS) matrix to construct a biomimetic scaffold optimized for bone regeneration. The Cu-MHM/CS composite scaffolds maintained high degrees of porosity and showed a sustained release of Cu ions. More importantly, the Cu-MHM/CS scaffolds not only enhanced the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) but also promoted the migration and tube formation of EA.hy926 cells. When implanted in rat critical-sized calvarial defects, the Cu-MHM/CS scaffolds significantly enhanced bone regeneration accompanied by more new blood vessel formation at 8 weeks post-operation compared with the MHM/CS scaffolds. These results suggest that the hypoxia-mimicking Cu-MHM/CS scaffolds could encourage bone regeneration by enhancing osteogenesis and angiogenesis simultaneously, which bodes well for the reconstruction of vascularized tissue-engineered bone.