Wei-Tao Jia

Comparative evaluation of MSCs from bone marrow and adipose tissue seeded in PRP-derived scaffold for cartilage regeneration

The aims of this study were to (1) determine whether platelet-rich plasma (PRP) could be prepared as a bioactive scaffold capable of endogenous growth factor release for cartilage repair; (2) compare the chondrogenic differentiation ability of mesenchymal stem cells (MSCs) from bone marrow (BMSC) and from adipose (ADSC) seeded within the PRP scaffold; and (3) test the efficacy of ADSC-PRP construct in cartilage regeneration in vivo. In vitro evaluation showed that a 3-dimensional scaffold with a mesh-like microstructure was formed from PRP, with the capability of endogenous growth factor release and ready cell incorporation. Upon seeding in the PRP scaffold, BMSC showed higher proliferation rate, and higher expression of cartilage-specific genes and proteins than ADSC. In an osteochondral defect model in rabbits, implanted BMSC seeded within PRP scaffold also exhibited better gross appearance and histological and immunohistochemical characteristics, higher cartilage-specific gene and protein expression as well as subchondral bone regeneration. ADSC seeded constructs developed into functional chondrocytes secreting cartilaginous matrix in rabbits at 9 weeks post-implantation. Our findings suggest that PRP is a candidate bioactive scaffold capable of releasing endogenous growth factors and that BMSC and ADSC seeded within the PRP scaffold differentiate into chondrocytes and may be suitable for cell-based cartilage repair.

Treatment of osteomyelitis and repair of bone defect by degradable bioactive borate glass releasing vancomycin.

The effectiveness of a degradable and bioactive borate glass has been compared with the clinically used calcium sulfate in the treatment of osteomyelitis of rabbits, as a carrier for vancomycin. The bone infections were induced in the tibias of 65 rabbits by injecting methicillin-resistant Staphylococcus aureus (MRSA). After 3 weeks, these rabbits were distributed into 4 groups and treated by debridement. Pure borate glass (BG), vancomycin-loaded calcium sulfate (VCS) and vancomycin-loaded borate glass (VBG) were implanted into the infection sites of groups 2 to 4 respectively. After 8 weeks, the effectiveness of treatment was assessed radiographically, bacteriologically, and histopathologically. The results showed that the negative rates of MRSA examination for rabbits were 36.36%, 18.18%, 73.33% and 81.25% respectively for groups 1 to 4. Significant differences were observed radiographically, bacteriologically, and histopathologically between groups 1 and 4, groups 2 and 3, and between groups 2 and 4. The best result of treatment was observed in group 4. Radiographically, VBG was found to be mostly reabsorbed and replaced by lots of new bones, whereas, VCS was completely reabsorbed and replaced by modest new bones. Histopathologically, there were lots of newly formed bones around VBG without any foreign body response, and only modest new bones around VCS with obvious foreign body response. VBG proved to have excellent biocompatibility and to be very effective in eradicating osteomyelitis and simultaneously stimulating bone regeneration, avoiding the disadvantages of VCS.

Teicoplanin-loaded borate bioactive glass implants for treating chronic bone infection in a rabbit tibia osteomyelitis model

The treatment of chronic osteomyelitis (bone infection) remains a clinical challenge. In this work, pellets composed of a chitosan-bonded mixture of borate bioactive glass particles (<50microm) and teicoplanin powder (antibiotic), were evaluated in vitro and in vivo for treating chronic osteomyelitis induced by methicillin-resistant Staphylococcus aureus (MRSA) in a rabbit model. When immersed in phosphate-buffered saline, the pellets showed sustained release of teicoplanin over 20-30 days, while the bioactive glass converted to hydroxyapatite (HA) within 7 days, eventually forming a porous HA structure. Implantation of the teicoplanin-loaded pellets in a rabbit tibia osteomyelitis model resulted in the detection of teicoplanin in the blood for about 9 days. The implants converted to a bone-like HA graft, and supported the ingrowth of new bone into the tibia defects within 12 weeks of implantation. Microbiological, histological and scanning electron microscopy techniques showed that the implants provided a cure for the bone infection. The results indicate that the teicoplanin-loaded borate bioactive glass implant, combining sustained drug release with the ability to support new bone ingrowth, could provide a method for treating chronic osteomyelitis.

In vitro evaluation of cytotoxicity of silver-containing borate bioactive glass

The cytotoxicity of silver-containing borate bioactive glass was evaluated in vitro from the response of osteoblastic and fibroblastic cells in media containing the dissolution products of the glass. Glass frits containing 0-2 weight percent (wt %) Ag were prepared by a conventional melting and quenching process. The amount of Ag dissolved from the glass into a simulated body fluid (SBF), measured using atomic emission spectroscopy, increased rapidly within the first 48 h, but slowed considerably at longer times. Structural and microchemical analysis showed that the formation of a hydroxyapatite-like layer on the glass surface within 14 days of immersion in the SBF. The response of MC3T3-E1 and L929 cells to the dissolution products of the glass was evaluated using SEM observation of cell morphology, and assays of MTT hydrolysis, lactate dehydrogenase release, and alkaline phosphatase activity after incubation for up to 48 h. Cytotoxic effects were found for the borate glass containing 2 wt % Ag, but not for 0.75 and 1 wt % Ag. This borate glass containing up to ∼1 wt % Ag could provide a coating material for bacterial inhibition and enhanced bioactivity of orthopaedic implant materials such as titanium.

A novel injectable borate bioactive glass cement as an antibiotic delivery vehicle for treating osteomyelitis.

Background A novel injectable cement composed of chitosan-bonded borate bioactive glass (BG) particles was evaluated as a carrier for local delivery of vancomycin in the treatment of osteomyelitis in a rabbit tibial model. Materials and Methods The setting time, injectability, and compressive strength of the borate BG cement, and the release profile of vancomycin from the cement were measured in vitro. The capacity of the vancomycin-loaded BG cement to eradicate methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis in rabbit tibiae in vivo was evaluated and compared with that for a vancomycin-loaded calcium sulfate (CS) cement and for intravenous injection of vancomycin. Results The BG cement had an injectability of >90% during the first 3 minutes after mixing, hardened within 30 minutes and, after hardening, had a compressive strength of 18±2 MPa. Vancomycin was released from the BG cement into phosphate-buffered saline for up to 36 days, and the cumulative amount of vancomycin released was 86% of the amount initially loaded into the cement. In comparison, vancomycin was released from the CS cement for up 28 days and the cumulative amount released was 89%. Two months post-surgery, radiography and microbiological tests showed that the BG and CS cements had a better ability to eradicate osteomyelitis when compared to intravenous injection of vancomycin, but there was no significant difference between the BG and CS cements in eradicating the infection. Histological examination showed that the BG cement was biocompatible and had a good capacity for regenerating bone in the tibial defects. Conclusions These results indicate that borate BG cement is a promising material both as an injectable carrier for vancomycin in the eradication of osteomyelitis and as an osteoconductive matrix to regenerate bone after the infection is cured.

Elution characteristics of teicoplanin-loaded biodegradable borate glass/chitosan composite

Local antibiotic delivery system has an advantage over systemic antibiotic for osteomyelitis treatment due to the delivery of high local antibiotic concentration while avoiding potential systemic toxicity. Composite biomaterials with multifunctional roles, consisting of a controlled antibiotic release, a mechanical (load-bearing) function, and the ability to promote bone regeneration, gradually become the most active area of investigation and development of local antibiotic delivery vehicles. In the present study, a composite of borate glass and chitosan (designated BG/C) was developed as teicoplanin delivery vehicle. The in vitro elution kinetics and antibacterial activity of teicoplanin released from BG/C composite as a function of immersion time were determined. Moreover, the pH changes of eluents and the bioactivity of the composite were characterized using scanning electron microscopy coupled with energy-dispersive spectroscopy and X-ray diffraction analysis.

Bioactive Glass for Large Bone Repair

There has been an ongoing quest for new biomedical materials for the repair and regeneration of large segmental bone defects caused by disease or trauma. Autologous bone graft (ABG) remains the gold standard for bone repair despite their limited supply and donor-site morbidity. The current tissue engineering approach with synthetically derived bone grafts requires a bioactive ceramic or polymeric scaffold loaded with growth factors for osteoinduction and angiogenesis, and bone marrow stromal cells (BMSCs) for osteogenic properties. Unfortunately, this approach has serious drawbacks: the low mechanical strength of scaffolds, the high cost of growth factors, and a lack of optimal strategies for growth-factor delivery. Here, it is shown that, for the first time, a synthetic material alone can repair large bone defects as efficiently as the gold standard ABG. Through the use of strong and resorbable bioactive glass scaffolds, complete bone healing, and defect bridging can be achieved in a rabbit femur segmental defect model without growth factors or BMSCs. New bone and blood vessel formation, in both inner and peripheral scaffolds, demonstrates the excellent osteoinductive and osteogenic properties of these scaffolds similar as ABG.

The prophylactic effects of platelet-leucocyte gel in osteomyelitis: AN EXPERIMENTAL STUDY IN A RABBIT MODEL

Platelet-leucocyte gel (PLG), a new biotechnological blood product, has hitherto been used primarily to treat chronic ulcers and to promote soft-tissue and bone regeneration in a wide range of medical fields. In this study, the antimicrobial efficacy of PLG against Staphylococcus aureus (ATCC 25923) was investigated in a rabbit model of osteomyelitis. Autologous PLG was injected into the tibial canal after inoculation with Staph. aureus. The prophylactic efficacy of PLG was evaluated by microbiological, radiological and histological examination. Animal groups included a treatment group that received systemic cefazolin and a control group that received no treatment. Treatment with PLG or cefazolin significantly reduced radiological and histological severity scores compared to the control group. This result was confirmed by a significant reduction in the infection rate and the number of viable bacteria. Although not comparable to cefazolin, PLG exhibited antimicrobial efficacy in vivo and therefore represents a novel strategy to prevent bone infection in humans.

In Vitro and In Vivo Efficacies of Teicoplanin-Loaded Calcium Sulfate for Treatment of Chronic Methicillin-Resistant Staphylococcus aureus Osteomyelitis

ABSTRACT The in vitro and in vivo therapeutic efficacies of teicoplanin-loaded calcium sulfate (TCS; 10% [wt] teicoplanin) were investigated in a rabbit model of chronic methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. The in vitro elution characteristics of teicoplanin from TCS pellets were realized by carrying out an evaluation of the release kinetics, recovery rate, and antibacterial activity of the released teicoplanin. Chronic osteomyelitis was induced by inoculating 107 CFU of a MRSA strain into the tibial cavity of rabbits. After 3 weeks, the animals were treated by debridement followed by implantation of TCS pellets in group 1, calcium sulfate (CS) pellets alone in group 2, and intravenous (i.v.) teicoplanin (6 mg/kg of body weight every 12 h for three doses and then every 24 h up to 4 weeks) in group 3. Animals in group 4 were left untreated. After 6 weeks, the efficacy of the osteomyelitis treatment was evaluated by hematological, radiological, microbiological, and histological examinations. In vitro elution studies showed sustained release of teicoplanin at a therapeutic level over a time period of 3 weeks. The released teicoplanin maintained its antibacterial activity. In vivo, the best therapeutic effect was observed in animals treated with TCS pellets, resulting in significantly lower radiological and histological scores, lower positive rates of MRSA culture and bacterial load, and excellent bone regeneration compared with those treated by CS alone or i.v. teicoplanin, without any local or systemic adverse effects. TCS pellets are an effective alternative to i.v. teicoplanin for the treatment of chronic MRSA osteomyelitis, particularly because teicoplanin is delivered locally while the TCS pellets simultaneously promote bone defect repair.

Three-dimensional visualization of bioactive glass-bone integration in a rabbit tibia model using synchrotron X-ray microcomputed tomography.

Synchrotron X-ray microcomputed tomography (SR microCT), with a micron resolution, was used to evaluate the osteoconduction and osteointegration by borate bioactive glass after implantation 12 weeks in a rabbit tibia model. The study focused on the biomaterial-bone interface. Results from SR microCT two-dimensional and three-dimensional (3D) reconstructions provided precise imaging of the biomaterial-bone integration and detailed microarchitecture of both the bone-like glass graft and the newly formed trabecular bone. Osteoconduction, the formation of new trabecular bone within a tibia defect, occurred only in the tibiae implanted with teicoplanin-loaded borate glass but not in those with teicoplanin-loaded CaSO(4) beads, indicating the excellent biocompatibility of the glass implants. 3D reconstruction of the tibiae also showed the infiltration of vascular tissue in both the bioactive glass graft and the new trabecular bone. This study indicates that SR microCT can serve as a valuable complementary technique for imaging bone repair when using bioactive glass implants.