Effects of lactic acid and glycolic acid on human osteoblasts: a way to understand PLGA involvement in PLGA/calcium phosphate composite failure

Electrosprayed Particles Loaded with Kartogenin as a Potential Osteochondral Repair Implant

The restoration of cartilage damage is a slow and not always successful process. Kartogenin (KGN) has significant potential in this space-it is able to induce the chondrogenic differentiation of stem cells and protect articular chondrocytes. In this work, a series of poly(lactic-co-glycolic acid) (PLGA)-based particles loaded with KGN were successfully electrosprayed. In this family of materials, PLGA was blended with a hydrophilic polymer (either polyethyleneglycol (PEG) or polyvinylpyrrolidone (PVP)) to control the release rate. Spherical particles with sizes in the range of 2.4-4.1 µm were fabricated. They were found to comprise amorphous solid dispersions, with high entrapment efficiencies of >93%. The various blends of polymers had a range of release profiles. The PLGA-KGN particles displayed the slowest release rate, and blending with PVP or PEG led to faster release profiles, with most systems giving a high burst release in the first 24 h. The range of release profiles observed offers the potential to provide a precisely tailored profile via preparing physical mixtures of the materials. The formulations are highly cytocompatible with primary human osteoblasts.

Novel therapy using a fish scale collagen scaffold for rotator cuff healing in rat models

BACKGROUND

Large and massive rotator cuff tears are challenging for surgeons because of postoperative complications such as repaired site retears. Recently, collagen extracted from fish scales has gained more attention because fish byproducts are considered a safer collagen source than other animal-derived scaffolds. This study aimed to evaluate the biological efficacy of tilapia scale-derived collagen scaffolds for rotator cuff repair in rat models.

METHODS

The infraspinatus tendon was resected from the greater tuberosity of Sprague-Dawley rats. In the control group, the tendon edge was sutured directly to the humeral head. In the augmentation group, the repaired site was augmented with a tilapia scale-derived collagen scaffold. Histologic examinations were performed at 2 and 4 weeks postoperatively via safranin O and immunofluorescence staining (isolectin B4 and type II collagen) in the bone-tendon junction. For mechanical analysis, the ultimate failure load of the tendon-humeral head complex was evaluated at 6 weeks postoperatively.

RESULTS

During safranin O staining, the repaired enthesis demonstrated greater proteoglycan staining in the augmentation group than in the control group at 4 weeks postoperatively. Compared to controls, the augmentation group had significantly higher vascular staining with isolectin B4 at 2 and 4 weeks postoperatively, type II collagen expression at 4 weeks postoperatively, and ultimate failure load at 6 weeks postoperatively.

CONCLUSION

Augmentation therapy using tilapia scale-derived type I collagen scaffolds promoted angiogenesis and fibrocartilage regeneration at the enthesis and provided higher mechanical strength than controls.

A collagen/PLA hybrid scaffold supports tendon-derived cell growth for tendon repair and regeneration

A rotator cuff tendon tear is a common shoulder injury with a relatively high rate of recurrence after surgical repair. In order to reinforce the repair and reduce the risk of clinical complications, a patch scaffold is typically sutured over the tendon tear to provide post-surgical mechanical support. However, despite considerable research effort in this area, a patch scaffold that provides both superior initial mechanical properties and supports cell proliferation at the same time has not yet been achieved. In this study, we engineered a collagen/poly(lactic acid) (COL/PLA) hybrid yarn to leverage mechanical strength of PLA yarn and the bioactivity of collagen. The COL/PLA yarns were used to fabricate a tissue engineering scaffold using textile weaving technology. This hybrid scaffold had a tensile strength of 354.0 ± 36.0 N under dry conditions and 267.2 ± 15.9 N under wet conditions, which was satisfactory to maintain normal tendon function. By introducing COL yarns into the hybrid scaffold, the proliferation of tendon-derived cells was significantly improved on the scaffold. Cell coverage after 28-days of in vitro cell culture was noticeably higher on the COL yarns compared to the PLA yarns as a result of a larger number of cells and more spread cell morphology on collagen. Cells spread in multiple directions on COL yarns, which resembled a more natural cell attachment on extracellular matrix. On the contrary, the cells attached to the PLA filaments presented an elongated morphology along the fiber's axial direction. Combining the mechanical robustness of PLA and the biological activity of collagen, the woven COL/PLA hybrid scaffold has shown its potential to be a promising candidate for tendon repair applications.

Evaluation of patches for rotator cuff repair: A systematic review and meta-analysis based on animal studies

Based on the published animal studies, we systematically evaluated the outcomes of various materials for rotator cuff repair in animal models and the potentials of their clinical translation. 74 animal studies were finally included, of which naturally derived biomaterials were applied the most widely (50.0%), rats were the most commonly used animal model (47.0%), and autologous tissue demonstrated the best outcomes in all animal models. The biomechanical properties of naturally derived biomaterials (maximum failure load: WMD 18.68 [95%CI 7.71–29.66]; P = 0.001, and stiffness: WMD 1.30 [95%CI 0.01–2.60]; P = 0.048) was statistically significant in the rabbit model. The rabbit model showed better outcomes even though the injury was severer compared with the rat model.

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The first systematic review & meta-analysis on rotator cuff patch materials.

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The quality of evidence for repair of rotator cuff injury with patch materials is very low.

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Evidence-based research is an effective way to study patch materials.

Amniotic Epithelial Stem Cells Counteract Acidic Degradation By-Products of Electrospun PLGA Scaffold by Improving Their Immunomodulatory Profile In Vitro

Electrospun poly(lactic-co-glycolic acid) (PLGA) scaffolds with highly aligned fibers (ha-PLGA) represent promising materials in the field of tendon tissue engineering (TE) due to their characteristics in mimicking fibrous extracellular matrix (ECM) of tendon native tissue. Among these properties, scaffold biodegradability must be controlled allowing its replacement by a neo-formed native tendon tissue in a controlled manner. In this study, ha-PLGA were subjected to hydrolytic degradation up to 20 weeks, under di-H₂O and PBS conditions according to ISO 10993-13:2010. These were then characterized for their physical, morphological, and mechanical features. In vitro cytotoxicity tests were conducted on ovine amniotic epithelial stem cells (oAECs), up to 7 days, to assess the effect of non-buffered and buffered PLGA by-products at different concentrations on cell viability and their stimuli on oAECs’ immunomodulatory properties. The ha-PLGA scaffolds degraded slowly as evidenced by a slight decrease in mass loss (14%) and average molecular weight (35%), with estimated degradation half-time of about 40 weeks under di-H₂O. The ultrastructure morphology of the scaffolds showed no significant fiber degradation even after 20 weeks, but alteration of fiber alignment was already evident at week 1. Moreover, mechanical properties decreased throughout the degradation times under wet as well as dry PBS conditions. The influence of acid degradation media on oAECs was dose-dependent, with a considerable effect at 7 days’ culture point. This effect was notably reduced by using buffered media. To a certain level, cells were able to compensate the generated inflammation-like microenvironment by upregulating IL-10 gene expression and favoring an anti-inflammatory rather than pro-inflammatory response. These in vitro results are essential to better understand the degradation behavior of ha-PLGA in vivo and the effect of their degradation by-products on affecting cell performance. Indeed, buffering the degradation milieu could represent a promising strategy to balance scaffold degradation. These findings give good hope with reference to the in vivo condition characterized by physiological buffering systems.

Human osteoblasts obtained from distinct periarticular sites demonstrate differences in biological function in vitro

AIMS

Accumulated evidence indicates that local cell origins may ingrain differences in the phenotypic activity of human osteoblasts. We hypothesized that these differences may also exist in osteoblasts harvested from the same bone type at periarticular sites, including those adjacent to the fixation sites for total joint implant components.

METHODS

Human osteoblasts were obtained from the acetabulum and femoral neck of seven patients undergoing total hip arthroplasty (THA) and from the femoral and tibial cuts of six patients undergoing total knee arthroplasty (TKA). Osteoblasts were extracted from the usually discarded bone via enzyme digestion, characterized by flow cytometry, and cultured to passage three before measurement of metabolic activity, collagen production, alkaline phosphatase (ALP) expression, and mineralization.

RESULTS

Osteoblasts from the acetabulum showed lower proliferation (p = 0.034), cumulative collagen release (p < 0.001), and ALP expression (p = 0.009), and produced less mineral (p = 0.006) than those from the femoral neck. Osteoblasts from the tibia produced significantly less collagen (p = 0.021) and showed lower ALP expression than those from the distal femur.

CONCLUSION

We have demonstrated for the first time an anatomical regional variation in the biological behaviours of osteoblasts on either side of the hip and knee joint. The lower osteoblast proliferation, matrix production, and mineralization from the acetabulum compared to those from the proximal femur may be reflected in differences in bone formation and implant fixation at these sites. Cite this article: Bone Joint Res 2021;10(9):611-618.

Does PRGF Work? A Prospective Clinical Study in Dogs with A Novel Polylactic Acid Scaffold Injected with PRGF Using the Modified Maquet Technique

Simple Summary

PRGF is a concentration of autologous platelets in a small volume of plasma, which is performed in a specific way and is an accessible resource in veterinary medicine. The PRGF has multiple demonstrated properties as antimicrobial, analgesic and anti-inflammatory but their osteoinductivity potential is controversial. We decided to use PRGF in combination with a PLA bioresorbable scaffold (a specific type of implant with osteoconduction properties) performed by 3D printing, and personalized for each patient, to determinate if the PRGF can produce osteoinduction and as a result, a faster bone healing and a faster patient recovery. Furthermore, in this study PLA scaffolds are proposed as an alternative for metallic implants to avoid the problems that those can cause. The MMT was the technique selected for solving the RCrCL as it is a variant of TTA that follows the same principle for the correction of the patellar tendon angle to neutralize distractive forces; however, this technique needs a lower amount of metallic implants for the scaffold fixation.

Abstract

Tibial tuberosity advancement is a surgical technique to restore the dynamical stability in the knee by advancing the insertion of the patellar ligament, for which it is necessary to advance the tibial crest, being maintained in the desired position usually by a cage and metallic implants. The purpose of this study was to replace the cage with a polylactic acid biodegradable scaffold designed for each patient by 3D printing, inserting platelet-rich in growth factors (PRGF) to demonstrate its osteoinductive properties. To this end, we used the modified Maquet technique to reduce the amount of metal to a minimum. Fifty-three dogs finished the study. The control and PRGF groups did not present any statistically significant differences in terms of ossification degree (p > 0.001) but they demonstrated satisfactory ossification compared to previous publications, although in the PRGF group three of the scaffolds suffered complete reabsorption. The PRGF and control groups did not show any statistically significant differences in terms of lameness degree (p > 0.001). However, the PRGF group showed at the first control some analgesic and anti-inflammatory properties but they were not enough for reducing the functional recovery time in a significant way. The PRGF group did not show any complications or negative results associated with their use.

3D Printing of Micro- and Nanoscale Bone Substitutes: A Review on Technical and Translational Perspectives

Recent developments in three-dimensional (3D) printing technology offer immense potential in fabricating scaffolds and implants for various biomedical applications, especially for bone repair and regeneration. As the availability of autologous bone sources and commercial products is limited and surgical methods do not help in complete regeneration, it is necessary to develop alternative approaches for repairing large segmental bone defects. The 3D printing technology can effectively integrate different types of living cells within a 3D construct made up of conventional micro- or nanoscale biomaterials to create an artificial bone graft capable of regenerating the damaged tissues. This article reviews the developments and applications of 3D printing in bone tissue engineering and highlights the numerous conventional biomaterials and nanomaterials that have been used in the production of 3D-printed scaffolds. A comprehensive overview of the 3D printing methods such as stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), and ink-jet 3D printing, and their technical and clinical applications in bone repair and regeneration has been provided. The review is expected to be useful for readers to gain an insight into the state-of-the-art of 3D printing of bone substitutes and their translational perspectives.

Preliminary Clinical and Radiographic Evaluation of a Novel Resorbable Implant of Polylactic Acid (PLA) for Tibial Tuberosity Advancement (TTA) by Modified Maquet Technique (MMT)

Our objectives were to determine whether PLA implants can be used in TTA with successful results; secondly, to observe whether they provide a faster bone healing; finally, to determine whether weight or age influences bone healing scores. PLA cages were created with a 3D printer. TTA by MMT with PLA implants was performed in 24 patients. Follow-ups were carried out pre-surgical, at 1, 2, and 5 months and consisted of a radiographic study and a lameness assessment. A comparison was performed in terms of weight and age. Patients data, time between follow-up examinations, healing score, and lameness score were compared between patients using commercial software for statistically significant differences p < 0.05. Eighteen dogs finished the study. The ossification degrees presented statistically significant differences between each other. PLA implants maintained the advancement in 100% of cases. Comparing weight and age did not present any statistically significant differences between groups. Lameness presented statistically significant differences between follow-up examinations. Complications were observed in 20.8%. PLA implants for TTA provide good functional results, presenting an acceptable rate of complications. They provide a faster bone healing of the osteotomy gap, which was not affected by age or body weight, and have a clinical recovery time similar to metallic implants.

Electrospun nanofibers promote wound healing: theories, techniques, and perspectives

At present, the clinical strategies for treating chronic wounds are limited, especially when it comes to pain relief and rapid wound healing. Therefore, there is an urgent need to develop alternative treatment methods. This paper provides a systematic review on recent researches on how electrospun nanofiber scaffolds promote wound healing and how the electrospinning technology has been used for fabricating multi-dimensional, multi-pore and multi-functional nanofiber scaffolds that have greatly promoted the development of wound healing dressings. First, we provide a review on the four stages of wound healing, which is followed by a discussion on the evolvement of the electrospinning technology, what is involved in electrospinning devices, and factors affecting the electrospinning process. Finally, we present the possible mechanisms of electrospun nanofibers to promote wound healing, the classification of electrospun polymers, cell infiltration favoring fiber scaffolds, antibacterial fiber scaffolds, and future multi-functional scaffolds. Although nanofiber scaffolds have made great progress as a type of multi-functional biomaterial, major challenges still remain for commercializing them in a way that fully meets the needs of patients.

A Polymer for Application as a Matrix Phase in a Concept of In Situ Curable Bioresorbable Bioactive Load-Bearing Continuous Fiber Reinforced Composite Fracture Fixation Plates

The use of bioresorbable fracture fixation plates made of aliphatic polyesters have good potential due to good biocompatibility, reduced risk of stress-shielding, and eliminated need for plate removal. However, polyesters are ductile, and their handling properties are limited. We suggested an alternative, PLAMA (PolyLActide functionalized with diMethAcrylate), for the use as the matrix phase for the novel concept of the in situ curable bioresorbable load-bearing composite plate to reduce the limitations of conventional polyesters. The purpose was to obtain a preliminary understanding of the chemical and physical properties and the biological safety of PLAMA from the prospective of the novel concept. Modifications with different molecular masses (PLAMA-500 and PLAMA-1000) were synthesized. The efficiency of curing was assessed by the degree of convergence (DC). The mechanical properties were obtained by tensile test and thermomechanical analysis. The bioresorbability was investigated by immersion in simulated body fluid. The biocompatibility was studied in cell morphology and viability tests. PLAMA-500 showed better DC and mechanical properties, and slower bioresorbability than PLAMA-1000. Both did not prevent proliferation and normal morphological development of cells. We concluded that PLAMA-500 has potential for the use as the matrix material for bioresorbable load-bearing composite fracture fixation plates.

PLGA/chitosan-heparin composite microparticles prepared with microfluidics for the construction of hMSC aggregates

Incorporating poly(lactic-co-glycolic) acid (PLGA) microparticles into human mesenchymal stem cells (hMSC) aggregates has shown promising application prospects. However, the acidic degradation products and burst release of PLGA microparticles still need to be ameliorated. In this study, the PLGA/chitosan-heparin (P/C-h) composite microparticles were successfully fabricated by integrating the double emulsion and microfluidic technology through the precise manipulation of the emulsion composition and flow rate of the two-phase in a flow-focusing chip. The P/C-h microparticles were highly monodispersed with a diameter of 23.45 ± 0.25 μm and shell-core structure of the PLGA encapsulated C-h complex, which were suitable for the fabrication of hMSC aggregates. When the mass ratio of PLGA to the C-h complex was optimized to 2 : 1, the pH of the leach liquor of P/C-h microparticles remained neutral. Compared with those of PLGA microparticles, the cytotoxicity and the initial burst release (loaded FGF-2 and VEGF) were both significantly reduced in P/C-h microparticles. Furthermore, the survival, stemness, as well as secretion and migration abilities of cells in hMSC aggregates incorporating P/C-h microparticles were also enhanced. In summary, the P/C-h composite microparticles prepared by the droplet microfluidic technique support the optimal biological and functional profile of the hMSC aggregates, which may facilitate the clinical applications of MSC-based therapy.

Preclinical biological and physicochemical evaluation of two-photon engineered 3D biomimetic copolymer scaffolds for bone healing

A major challenge in orthopedics is the repair of large non-union bone fractures. A promising therapy for this indication is the use of biodegradable bioinspired biomaterials that stabilize the fracture site, relieve pain and initiate bone formation and healing. This study uses a multidisciplinary evaluation strategy to assess immunogenicity, allergenicity, bone responses and physicochemical properties of a novel biomaterial scaffold. Two-photon stereolithography generated personalized custom-built scaffolds with a repeating 3D structure of Schwarz Primitive minimal surface unit cell with a specific pore size of ∼400 μm from three different methacrylated poly(d,l-lactide-co-ε-caprolactone) copolymers with lactide to caprolactone monomer ratios of 16 : 4, 18 : 2 and 9 : 1. Using in vitro and in vivo assays for bone responses, immunological reactions and degradation dynamics, we found that copolymer composition influenced the scaffold physicochemical and biological properties. The scaffolds with the fastest degradation rate correlated with adverse cellular effects and mechanical stiffness correlated with in vitro osteoblast mineralization. The physicochemical properties also correlated with in vivo bone healing and immune responses. Overall these observations provide compelling support for these scaffolds for bone repair and illustrate the effectiveness of a promising multidisciplinary strategy with great potential for the preclinical evaluation of biomaterials.

Osteogenic inducer sustained-release system promotes the adhesion, proliferation, and differentiation of osteoblasts on titanium surface

OBJECTIVE

Biomaterial can be locally applied to promote the osseointegration of dental implants. This study aimed to fabricate an osteogenic inducer (OI) sustained-release system and to evaluate its effects on the adhesion, proliferation, and differentiation of osteoblasts on titanium surfaces.

METHODS

First of all, different contents of OI solution were added to the poly (lactic-co-glycolic acid) (PLGA) gel individually to investigate the best physical properties and drug-release rate. Moreover, osteoblasts were isolated from the calvaria of two-month-old New Zealand rabbits through sequential enzymatic digestion. Osteoblasts were seeded onto the surface of Ti disks (control group), Ti coated with PLGA gel (PLGA group), and Ti coated with the OI sustained-release system (PLGA+OI group). Cell adhesion was observed by scanning electron microscopy. Cell proliferation was analyzed by cell counting kit-8. Cell differentiation was tested by alizarin red staining, alkaline phosphatase (ALP) activity and osteogenic-related gene expression.

RESULTS

The OI sustained-release system contained 15% OI solution had appropriate physical properties and drug-release rate. The osteoblasts in the PLGA+OI group were in a typical spindle shape with a considerable number indicating the promotion of adhesion and proliferation. The expression of early and late stage osteoblast differentiation genes in the PLGA+OI group were significantly higher than that of the control group and PLGA group at each time point. The PLGA group showed accelerated adhesion and differentiation but reduced proliferation compared with the control.

CONCLUSION

The OI sustained-release system promotes the adhesion, proliferation, and differentiation of osteoblasts on titanium surfaces. This system is a cost-effective osteoconductive biomaterial that might be promising for use in dental implantation.

Long-term study on the osteogenetic capability and mechanical behavior of a new resorbable biocomposite anchor in a canine model

Background

Biodegradable suture anchors are commonly used for repairing torn rotator cuffs, but these biodegradable materials still suffer from low mechanical strength, poor osteointegration, and the generation of acidic degradation byproducts.

Method

The purpose of this study was to evaluate the long-term mechanical behavior and osteogenetic capabilities of a biocomposite anchor injection molded with 30% β-tricalcium phosphate microparticles blended with 70% poly (L-lactide-co-glycolide) (85/15). This study investigated in vitro degradation and in vivo bone formation in a canine model. The initial mechanical behavior, mechanical strength retention with degradation time, and degradation features were investigated.

Results

The results showed that the biocomposite anchor had sufficient initial mechanical stability confirmed by comparing the initial shear load on the anchor with the minimum shear load borne by an ankle fracture fixation screw, which is considered a worst-case implantation site for mechanical loading. The maximum shear load retention of the biocomposite anchor was 83% at 12 weeks, which is desirable, as it aligns with the rate of bone healing. The β-tricalcium phosphate fillers were evenly dispersed in the polymeric matrix and acted to slow the degradation rate and improve the mechanical strength of the anchor. The interface characteristics between the β-tricalcium phosphate particles and the polymeric matrix changed the degradation behavior of the biocomposite. Phosphate buffer saline was shown to diffuse through the interface into the biocomposite to inhibit the core accelerated degradation rate. In vivo, the addition of β-tricalcium phosphate induced new bone formation. The biocomposite material developed in this study demonstrated improved osteogenesis in comparison to a plain poly (L-lactide-co-glycolide) material. Neither anchor produced adverse tissue reactions, indicating that the biocomposite had favorable biocompatibility following long-term implantation.

Conclusion

In summary, the new biocomposite anchor presented in this study had favorable osteogenetic capability, mechanical property, and controlled degradation rate for bone fixation.

Translational potential of this article

The new biocomposite anchor had sufficient initial and long-term fixation stability and bone formation capability in the canine model. It is indicated that the new biocomposite anchor has a ​potential for orthopedic application.

Biological response to an experimental implant for tibial tuberosity advancement in dogs: A pre-clinical study

In this study, we propose a novel bioresorbable bioactive implant for tibial tuberosity advancement (TTA). The implant consists of a gradually resorbing load-bearing shell which encompasses rapidly resorbing small casings loaded with silica-based bioactive glass (BG) particulates which promote bone formation and reduce the risk of infection. The shell and the casings are manufactured by 3D printing from two medical grade bioresorbable polymers (a polyglycolide/lactide based and a polydioxanone based) that have different degradation rates. The casings are expected to resorb within days after surgery to expose the BG particulates while the shell would retain the load-bearing properties of the implant for the time required by bone healing. Unlike the currently used metallic devices, the novel implant is resorbed and excreted from the body once its purpose is fulfilled. This study presents a logical progression from the in vitro characterisation of the materials and implants to the in vivo investigation of the experimental implants. This included mechanical testing of the materials, finite element analysis of a preliminary design of the novel TTA implant, assessment of the degradation behaviour of the polymers and the ion exchange of BG in simulated body fluid, and investigation of the biological response to the novel implants after implantation in rabbits. The osteointegration of the novel implants was comparable to the osteointegration of Ti6Al4V implants in the control group; the biological efficacy and safety were confirmed. The biological response was in line with the expectations. The proof of concept for the novel TTA implants was demonstrated.

Augmenting endogenous repair of soft tissues with nanofibre scaffolds

As our ability to engineer nanoscale materials has developed we can now influence endogenous cellular processes with increasing precision. Consequently, the use of biomaterials to induce and guide the repair and regeneration of tissues is a rapidly developing area. This review focuses on soft tissue engineering, it will discuss the types of biomaterial scaffolds available before exploring physical, chemical and biological modifications to synthetic scaffolds. We will consider how these properties, in combination, can provide a precise design process, with the potential to meet the requirements of the injured and diseased soft tissue niche. Finally, we frame our discussions within clinical trial design and the regulatory framework, the consideration of which is fundamental to the successful translation of new biomaterials.

Enhanced release of calcium phosphate additives from bioresorbable orthopaedic devices using irradiation technology is non-beneficial in a rabbit model: An animal study

Objectives

Bioresorbable orthopaedic devices with calcium phosphate (CaP) fillers are commercially available on the assumption that increased calcium (Ca) locally drives new bone formation, but the clinical benefits are unknown. Electron beam (EB) irradiation of polymer devices has been shown to enhance the release of Ca. The aims of this study were to: 1) establish the biological safety of EB surface-modified bioresorbable devices; 2) test the release kinetics of CaP from a polymer device; and 3) establish any subsequent beneficial effects on bone repair in vivo.

Methods

ActivaScrew Interference (Bioretec Ltd, Tampere, Finland) and poly(L-lactide-co-glycolide) (PLGA) orthopaedic screws containing 10 wt% β-tricalcium phosphate (β-TCP) underwent EB treatment. In vitro degradation over 36 weeks was investigated by recording mass loss, pH change, and Ca release. Implant performance was investigated in vivo over 36 weeks using a lapine femoral condyle model. Bone growth and osteoclast activity were assessed by histology and enzyme histochemistry.

Results

Calcium release doubled in the EB-treated group before returning to a level seen in untreated samples at 28 weeks. Extensive bone growth was observed around the perimeter of all implant types, along with limited osteoclastic activity. No statistically significant differences between comparative groups was identified.

Conclusion

The higher than normal dose of EB used for surface modification did not adversely affect tissue response around implants in vivo. Surprisingly, incorporation of β-TCP and the subsequent accelerated release of Ca had no significant effect on in vivo implant performance, calling into question the clinical evidence base for these commercially available devices.

Cite this article: I. Palmer, S. A. Clarke, F. J Buchanan. Enhanced release of calcium phosphate additives from bioresorbable orthopaedic devices using irradiation technology is non-beneficial in a rabbit model: An animal study. Bone Joint Res 2019;8:266–274. DOI: 10.1302/2046-3758.86.BJR-2018-0224.R2.

Manufacturing and characterization of plates for fracture fixation of bone with biocomposites of poly (lactic acid-co-glycolic acid) (PLGA) with calcium phosphates bioceramics

Commercially, there are several plates and screws for bone fracture fixation made with PLA, however, its long degradation time and lack of integration with bone structure, provides interest in research using polymers with faster degradation, such as PLGA, and together with bioceramics, in order to improve bioactivity in bone regeneration. Based on this, in this study, bone fracture fixation plates composed of PLGA polymer matrix and combinations of 5 and 10%wt. of bioceramics were processed by microinjection. The bioceramics used comprehend nanostructured hydroxyapatite (n-HA), β-tricalcium phosphate (β-TCP) and calcium phosphate with ion substitution of magnesium (Mg-Ca/P) and strontium (Sr-Ca/P). The introduction of bioceramics modified thermal and mechanical properties of the polymer. The TGA analysis showed that there was a variation on the ceramic's mass inserted in relation to the expected values (5% and 10%wt.) in all groups of biocomposites. In general, Tg values obtained by DMA were slightly increased in almost all the biocomposites. The storage modulus (E') of biocomposites was higher for almost all groups of inserted ceramics, with exception of 5%n-HA. In the flexural tests, the biocomposites obtained a great dispersion in average values of fracture loading, presented lower values in relation to pure PLGA. There were difficulties in the processing of biocomposites with Mg-Ca/P and Sr-Ca/P, a factor that can be attributed to lack of homogeneity in the material mixing process. The results suggest modifications in thermal and mechanical properties of the PLGA plates with the bioceramics insertion and provide improvement understanding about of manufactured composites with PLGA and bioceramics.

PLGA: From a classic drug carrier to a novel therapeutic activity contributor

Poly(lactic-co-glycolic acid) (PLGA) is well known for its biocompatibility and minimal toxicity. It is one of the most promising biodegradable polymeric drug delivery systems able to get endorsement from regulatory bodies to enter market. For many decades, PLGA has been functioning as an excipient, which by definition is pharmaceutically inert at a given dose of formulation. Lactate (one of the hydrolysis products of PLGA) has a key role in biochemical pathways and could improve physiological activities in certain illnesses by exerting therapeutic effects such as angiogenesis and promotion of healing. These activities, however, depend on the released amounts and metabolic clearance of lactate and route of formulation delivery. In the current commentary, along with several key notes on the lactate interactions, we would like to inform the PLGA research community that lactate (resulting from local delivery of physiologically significant amount of PLGA) may positively or negatively affect therapeutic efficacy of certain drugs. Hence, the excipient role of PLGA may be investigated for its potential pharmacological contributions in some biomedical applications.

Bridging Repair of Large Rotator Cuff Tears Using a Multilayer Decellularized Tendon Slices Graft in a Rabbit Model

PURPOSE

The purpose of this study was to evaluate the efficacy of an extracellular matrix scaffold with multilayer decellularized tendon slices (MDTSs) for reconstructing large rotator cuff tears in a rabbit model.

METHODS

Large defects in the infraspinatus tendons were created bilaterally in 36 rabbits. The graft group underwent bridging repair of the defects with the MDTSs grafts from Achilles tendons of adult beagle dogs, and the control group underwent repair with the autologous excised tendon. Specimens underwent histologic observation, biomechanical testing, and microcomputed tomography analysis at 2, 4, and 8 weeks after surgery.

RESULTS

Histologic analysis confirmed that the MDTSs graft promoted cell ingrowth and tissue integration, and fibrocartilage and Sharpey fibers formed at the enthesis at 8 weeks. Accordingly, the MDTSs graft generated a histologic appearance similar to that of the autogenous tendon graft. Mechanical testing revealed a significant increase of the regenerated tendons in ultimate load and stiffness from 4 to 8 weeks postoperatively, which was similar to autologous tendon repair. Microcomputed tomography analysis demonstrated that the MDTSs graft promoted bone formation at the tendon-bone insertion, thus improving the mechanical properties of the repair tendon.

CONCLUSIONS

The MDTSs graft used to bridge large rotator cuff defects in a rabbit model promoted host cell ingrowth, enhanced the remodeling of regenerated tendon, and promoted fibrocartilage formation, thus improving the biomechanical properties of the repaired tendon. This study thereby provides fundamental information for rotator cuff regeneration with the MDTSs graft.

CLINICAL RELEVANCE

Rotator cuff regeneration using MDTSs grafts is a promising procedure for large rotator cuff tears.

An overview of development and status of fiber-reinforced composites as dental and medical biomaterials

Fibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and particulate filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on particulate filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problems related to traditional isotropic dental and medical materials. This overview reviews the rationale and status of using biostable glass FRC in applications from restorative and prosthetic dentistry to cranial surgery. The overview highlights also the critical material based factors and clinical requirement for the succesfull use of FRCs in dental reconstructions.

Lactic acid of PLGA coating promotes angiogenesis on the interface between porous titanium and diabetic bone

The diabetes-related high failure risk for endosseous implants needs efficacious methods to improve osteointegration on the bone-implant interface (BII). Poly(lactic-co-glycolic) acid (PLGA) is widely used in tissue engineering but its effects on the BII in diabetes remain unclear. To clarify this issue, 3D-printed porous titanium implants (TI) with and without PLGA coating were fixed in the bone defects of sheep in vivo, and vascular endothelial cells (VEC) and osteoblasts were incubated on the implant surface under normal conditions (NC) and diabetic conditions (DC) in vitro. The results showed that the PLGA coating promoted angiogenesis on the BII and the osteointegration of TI in diabetic sheep. The PLGA coating attenuated the DC-induced dysfunctions of VEC but not of osteoblasts. When VEC and osteoblasts were co-cultured in DC, the PLGA coating showed protective effects on the osteoblasts. Lactic acid (LA) but not glycolic acid (GA), both of which are degradation products of PLGA, induced similar effects to those of PLGA. These results suggest that PLGA coating on TI could promote angiogenesis in diabetes by its degradation production of LA, thus indirectly improving the bone formation on BII. Furthermore, PLGA exerted its effects, at least partially, through inhibiting the pathological effects of advanced glycation end products (AGEs) on the BII. This is the first study of the effects of PLGA on angiogenesis on the BII and the first findings on the inhibitory effects of PLGA on AGEs. Our findings demonstrate that PLGA is a promising interface-modification component for fabricating implants with better angiogenesis and osteointegration on the BII under diabetic conditions. This strategy might be applicable for reducing implant failure in diabetic patients.

Renewable poly(δ-decalactone) based block copolymer micelles as drug delivery vehicle: in vitro and in vivo evaluation

Polymers from natural resources are attracting much attention in various fields including drug delivery as green alternatives to fossil fuel based polymers. In this quest, novel block copolymers based on renewable poly(δ-decalactone) (PDL) were evaluated for their drug delivery capabilities and compared with a fossil fuel based polymer i.e. methoxy-poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL). Using curcumin as a hydrophobic drug model, micelles of PDL block copolymers with different orientation i.e. AB (mPEG-b-PDL), ABA (PDL-b-PEG-b-PDL), ABC (mPEG-b-PDL-b-poly(pentadecalactone) and (mPEG-b-PCL) were prepared by nanoprecipitation method. The size, drug loading and curcumin stability studies results indicated that mPEG-b-PDL micelles was comparable to its counterpart mPEG-b-PCL micelles towards improved delivery of curcumin. Therefore, mixed micelles using these two copolymers were also evaluated to see any change in size, loading and drug release. Drug release studies proposed that sustained release can be obtained using poly(pentadecalactone) as crystalline core whereas rapid release can be achieved using amorphous PDL core. Further, mPEG-b-PDL micelles were found to be non-haemolytic, up to the concentration of 40 mg/mL. In vivo toxicity studies on rats advised low-toxic behaviour of these micelles up to 400 mg/kg dose, as evident by histopathological and biochemical analysis. In summary, it is anticipated that mPEG-b-PDL block copolymer micelles could serve as a renewable alternative for mPEG-b-PCL copolymers in drug delivery applications.

Tissue-engineered tendon constructs for rotator cuff repair in sheep

Current rotator cuff repair commonly involves the use of single or double row suture techniques, and despite successful outcomes, failure rates continue to range from 20 to 95%. Failure to regenerate native biomechanical properties at the enthesis is thought to contribute to failure rates. Thus, the need for technologies that improve structural healing of the enthesis after rotator cuff repair is imperative. To address this issue, our lab has previously demonstrated enthesis regeneration using a tissue-engineered graft approach in a sheep anterior cruciate ligament (ACL) repair model. We hypothesized that our tissue-engineered graft designed for ACL repair also will be effective in rotator cuff repair. The goal of this study was to test the efficacy of our Engineered Tissue Graft for Rotator Cuff (ETG-RC) in a rotator cuff tear model in sheep and compare this novel graft technology to the commonly used double row suture repair technique. Following a 6-month recovery, the grafted and contralateral shoulders were removed, imaged using X-ray, and tested biomechanically. Additionally, the infraspinatus muscle, myotendinous junction, enthesis, and humeral head were preserved for histological analysis of muscle, tendon, and enthesis structure. Our results showed that our ETC-RCs reached 31% of the native tendon tangent modulus, which was a modest, non-significant, 11% increase over that of the suture-only repairs. However, the histological analysis showed the regeneration of a native-like enthesis in the ETG-RC-repaired animals. This advanced structural healing may improve over longer times and may diminish recurrence rates of rotator cuff tears and lead to better clinical outcomes. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:289-299, 2018.

Mimicking oxygen delivery and waste removal functions of blood

In addition to immunological and wound healing cell and platelet delivery, ion stasis and nutrient supply, blood delivers oxygen to cells and tissues and removes metabolic wastes. For decades researchers have been trying to develop approaches that mimic these two immediately vital functions of blood. Oxygen is crucial for the long-term survival of tissues and cells in vertebrates. Hypoxia (oxygen deficiency) and even at times anoxia (absence of oxygen) can occur during organ preservation, organ and cell transplantation, wound healing, in tumors and engineering of tissues. Different approaches have been developed to deliver oxygen to tissues and cells, including hyperbaric oxygen therapy (HBOT), normobaric hyperoxia therapy (NBOT), using biochemical reactions and electrolysis, employing liquids with high oxygen solubility, administering hemoglobin, myoglobin and red blood cells (RBCs), introducing oxygen-generating agents, using oxygen-carrying microparticles, persufflation, and peritoneal oxygenation. Metabolic waste accumulation is another issue in biological systems when blood flow is insufficient. Metabolic wastes change the microenvironment of cells and tissues, influence the metabolic activities of cells, and ultimately cause cell death. This review examines advances in blood mimicking systems in the field of biomedical engineering in terms of oxygen delivery and metabolic waste removal.

Bioinspired Collagen Scaffolds in Cranial Bone Regeneration: From Bedside to Bench

Calvarial defects are common reconstructive dilemmas secondary to a variety of etiologies including traumatic brain injury, cerebrovascular disease, oncologic resection, and congenital anomalies. Reconstruction of the calvarium is generally undertaken for the purposes of cerebral protection, contour restoration for psychosocial well-being, and normalization of neurological dysfunction frequently found in patients with massive cranial defects. Current methods for reconstruction using autologous grafts, allogeneic grafts, or alloplastic materials have significant drawbacks that are unique to each material. The combination of wide medical relevance and the need for a better clinical solution render defects of the cranial skeleton an ideal target for development of regenerative strategies focused on calvarial bone. With the improved understanding of the instructive properties of tissue-specific extracellular matrices and the advent of precise nanoscale modulation in materials science, strategies in regenerative medicine have shifted in paradigm. Previously considered to be simple carriers of stem cells and growth factors, increasing evidence exists for differential materials directing lineage specific differentiation of progenitor cells and tissue regeneration. In this work, we review the clinical challenges for calvarial reconstruction, the anatomy and physiology of bone, and extracellular matrix-inspired, collagen-based materials that have been tested for in vivo cranial defect healing.

A Fully Functional Drug-Eluting Joint Implant

Despite advances in orthopedic materials, the development of drug-eluting bone and joint implants that can sustain the delivery of the drug and maintain the necessary mechanical strength in order to withstand loading has remained elusive. Here, we demonstrate that modifying the eccentricity of drug clusters and the percolation threshold in ultrahigh molecular weight polyethylene (UHMWPE) results in maximized drug elution and in the retention of mechanical strength. The optimized UHMWPE eluted antibiotic at a higher concentration for longer than the clinical gold standard antibiotic-eluting bone cement while retaining the mechanical and wear properties of clinically used UHMWPE joint prostheses. Treatment of lapine knees infected with Staphylococcus aureus with the antibiotic-eluting UHMWPE led to complete bacterial eradication and to the absence of detectable systemic effects. We argue that the antibiotic-eluting UHMWPE joint implant is a promising candidate for clinical trials.

Micro- and Macrostructured PLGA/Gelatin Scaffolds Promote Early Cardiogenic Commitment of Human Mesenchymal Stem Cells In Vitro

The biomaterial scaffold plays a key role in most tissue engineering strategies. Its surface properties, micropatterning, degradation, and mechanical features affect not only the generation of the tissue construct in vitro, but also its in vivo functionality. The area of myocardial tissue engineering still faces significant difficulties and challenges in the design of bioactive scaffolds, which allow composition variation to accommodate divergence in the evolving myocardial structure. Here we aimed at verifying if a microstructured bioartificial scaffold alone can provoke an effect on stem cell behavior. To this purpose, we fabricated microstructured bioartificial polymeric constructs made of PLGA/gelatin mimicking anisotropic structure and mechanical properties of the myocardium. We found that PLGA/gelatin scaffolds promoted adhesion, elongation, ordered disposition, and early myocardial commitment of human mesenchymal stem cells suggesting that these constructs are able to crosstalk with stem cells in a precise and controlled manner. At the same time, the biomaterial degradation kinetics renders the PLGA/gelatin constructs very attractive for myocardial regeneration approaches.

A comparative evaluation of the effect of polymer chemistry and fiber orientation on mesenchymal stem cell differentiation

Bioengineered tissue scaffolds in combination with cells hold great promise for tissue regeneration. The aim of this study was to determine how the chemistry and fiber orientation of engineered scaffolds affect the differentiation of mesenchymal stem cells (MSCs). Adipogenic, chondrogenic, and osteogenic differentiation on aligned and randomly orientated electrospun scaffolds of Poly (lactic‐co‐glycolic) acid (PLGA) and Polydioxanone (PDO) were compared. MSCs were seeded onto scaffolds and cultured for 14 days under adipogenic‐, chondrogenic‐, or osteogenic‐inducing conditions. Cell viability was assessed by alamarBlue metabolic activity assays and gene expression was determined by qRT‐PCR. Cell‐scaffold interactions were visualized using fluorescence and scanning electron microscopy. Cells grew in response to scaffold fiber orientation and cell viability, cell coverage, and gene expression analysis showed that PDO supports greater multilineage differentiation of MSCs. An aligned PDO scaffold supports highest adipogenic and osteogenic differentiation whereas fiber orientation did not have a consistent effect on chondrogenesis. Electrospun scaffolds, selected on the basis of fiber chemistry and alignment parameters could provide great therapeutic potential for restoration of fat, cartilage, and bone tissue. This study supports the continued investigation of an electrospun PDO scaffold for tissue repair and regeneration and highlights the potential of optimizing fiber orientation for improved utility. © 2016 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2843–2853, 2016.

Long-Term Degradation of Self-Reinforced Poly-Levo (96%)/Dextro (4%)-Lactide/β-Tricalcium Phosphate Biocomposite Interference Screws

PURPOSE

To evaluate the long-term in vivo degradation of biocomposite interference screws made with self-reinforced poly-levo (96%)/dextro (4%)-lactide/β-tricalcium phosphate [SR-PL(96)/D(4)LA/β-TCP].

METHODS

A study of the in vivo biologic behavior of an SR-PL(96)/D(4)LA/β-TCP biocomposite interference screw was initiated in 2011 using an anterior cruciate ligament (ACL) reconstruction model. Eight patients undergoing a bone-patellar tendon-bone ACL reconstruction fixed at both the femur and tibia with an SR-PL(96)/D(4)LA/β-TCP screw at least 36 months earlier were evaluated by physical, radiographic, and computed tomography (CT) evaluations. Lysholm, Tegner, Cincinnati, and International Knee Documentation Committee scores were obtained. After incomplete degradation was observed in these 8 patients, a subsequent series of 17 patients were evaluated at a minimum of 48 months after surgery. By use of CT scans, Hounsfield unit (HU) data were obtained at the femoral and tibial screw and other bone sites. An ossification quality score (range, 1 to 4) was used to determine osteoconductivity at the screw sites.

RESULTS

Eleven male and 6 female patients evaluated by CT scan and radiographs at a mean of 50 months (range, 48 to 61 months) after surgery showed bone plug healing to the tunnel wall and the SR-PL(96)/D(4)LA/β-TCP screws were replaced with material that was calcified and non-trabecular. Osteoconductivity was present in 24 of 34 tunnels (70.58%) and nearly complete or complete (type 3 or 4 ossification) in 11 of 34 (32.35%). Mean screw site densities (femoral, 242 HU; tibial, 240 HU) were consistent with cancellous bone density. One positive pivot-shift test was found. Lysholm, Cincinnati, Tegner, and International Knee Documentation Committee activity scores improved from 44.5, 40.7, 2.3, and 1.4, respectively, preoperatively to 92, 92.4, 5.7, and 3.3, respectively, at follow-up (P < .0001). The average postoperative Single Assessment Numeric Evaluation score was 92. The mean KT arthrometer (MEDmetric, San Diego, CA) difference was 1.25 mm.

CONCLUSIONS

The SR-PL(96)/D(4)LA/β-TCP interference screw was replaced with calcified, non-trabecular material 4 years after implantation in a bone-patellar tendon-bone ACL reconstruction model. Osteoconductivity was confirmed in 24 of 34 screw sites (71%), with nearly complete or complete filling in 11 of 34 (33%). The SR-PL(96)/D(4)LA/β-TCP biocomposite interference screw is osteoconductive.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Biologic Treatments for Sports Injuries II Think Tank-Current Concepts, Future Research, and Barriers to Advancement, Part 2: Rotator Cuff

Rotator cuff tears are common and result in considerable morbidity. Tears within the tendon substance or at its insertion into the humeral head represent a considerable clinical challenge because of the hostile local environment that precludes healing. Tears often progress without intervention, and current surgical treatments are inadequate. Although surgical implants, instrumentation, and techniques have improved, healing rates have not improved, and a high failure rate remains for large and massive rotator cuff tears. The use of biologic adjuvants that contribute to a regenerative microenvironment have great potential for improving healing rates and function after surgery. This article presents a review of current and emerging biologic approaches to augment rotator cuff tendon and muscle regeneration focusing on the scientific rationale, preclinical, and clinical evidence for efficacy, areas for future research, and current barriers to advancement and implementation.

Safety of bioabsorbable implants in vitro

Background

The aim of the present study was to investigate the safety of bioabsorbable plates and screws in humans.

Methods

For this purpose, an implant system based on [poly(lactic-co-glycolic acids)(85:15)] was designed. The system was tested for pH, temperature, and swelling and then its surface morphology was analyzed for surface porosity using environmental electron microscopy. Then, the effects of this bioabsorbable system on the viability and profileration of osteocytes were examined on a molecular level via in vitro experiments. A [poly(lactic-co-glycolic acids)(90:10)] bioabsorbable implant, which is commercially available and used in orthopedic surgery, was used as control group. For the statistical evaluation of the data obtained in the present study, the groups were compared by Tukey HSD test following ANOVA. The significance level was set as p < 0.05.

Results

It was observed that the osteocytes cultivated on the PLGA system designed in the present study included more live cells and allowed more proliferation compared to the control.

Conclusion

One of the criteria in the selection of implants for orthopedic surgery is that a good implant should not need removal and thus a second surgery. In the present study, a bioabsorbable implant was designed considering this criterion. The present study is the first step to prove the safety of this new design by in vitro toxicity and viability experiments.

Augmentation of Rotator Cuff Repair With Soft Tissue Scaffolds

Background

Tears of the rotator cuff are one of the most common tendon disorders. Treatment often includes surgical repair, but the rate of failure to gain or maintain healing has been reported to be as high as 94%. This has been substantially attributed to the inadequate capacity of tendon to heal once damaged, particularly to bone at the enthesis. A number of strategies have been developed to improve tendon-bone healing, tendon-tendon healing, and tendon regeneration. Scaffolds have received considerable attention for replacement, reconstruction, or reinforcement of tendon defects but may not possess situation-specific or durable mechanical and biological characteristics.

Purpose

To provide an overview of the biology of tendon-bone healing and the current scaffolds used to augment rotator cuff repairs.

Study Design

Systematic review; Level of evidence, 4.

Methods

A preliminary literature search of MEDLINE and Embase databases was performed using the terms rotator cuff scaffolds, rotator cuff augmentation, allografts for rotator cuff repair, xenografts for rotator cuff repair, and synthetic grafts for rotator cuff repair.

Results

The search identified 438 unique articles. Of these, 214 articles were irrelevant to the topic and were therefore excluded. This left a total of 224 studies that were suitable for analysis.

Conclusion

A number of novel biomaterials have been developed into biologically and mechanically favorable scaffolds. Few clinical trials have examined their effect on tendon-bone healing in well-designed, long-term follow-up studies with appropriate control groups. While there is still considerable work to be done before scaffolds are introduced into routine clinical practice, there does appear to be a clear indication for their use as an interpositional graft for large and massive retracted rotator cuff tears and when repairing a poor-quality degenerative tendon.

Wound dressings composed of copper-doped borate bioactive glass microfibers stimulate angiogenesis and heal full-thickness skin defects in a rodent model

There is a need for better wound dressings that possess the requisite angiogenic capacity for rapid in situ healing of full-thickness skin wounds. Borate bioactive glass microfibers are showing a remarkable ability to heal soft tissue wounds but little is known about the process and mechanisms of healing. In the present study, wound dressings composed of borate bioactive glass microfibers (diameter = 0.4-1.2 μm; composition 6Na2O, 8K2O, 8MgO, 22CaO, 54B2O3, 2P2O5; mol%) doped with 0-3.0 wt.% CuO were created and evaluated in vitro and in vivo. When immersed in simulated body fluid, the fibers degraded and converted to hydroxyapatite within ∼7 days, releasing ions such as Ca, B and Cu into the medium. In vitro cell culture showed that the ionic dissolution product of the fibers was not toxic to human umbilical vein endothelial cells (HUVECs) and fibroblasts, promoted HUVEC migration, tubule formation and secretion of vascular endothelial growth factor (VEGF), and stimulated the expression of angiogenic-related genes of the fibroblasts. When used to treat full-thickness skin defects in rodents, the Cu-doped fibers (3.0 wt.% CuO) showed a significantly better capacity to stimulate angiogenesis than the undoped fibers and the untreated defects (control) at 7 and 14 days post-surgery. The defects treated with the Cu-doped and undoped fibers showed improved collagen deposition, maturity and orientation when compared to the untreated defects, the improvement shown by the Cu-doped fibers was not markedly better than the undoped fibers at 14 days post-surgery. These results indicate that the Cu-doped borate glass microfibers have a promising capacity to stimulate angiogenesis and heal full-thickness skin defects. They also provide valuable data for understanding the role of the microfibers in healing soft tissue wounds.

Gene expression profiling of peri-implant healing of PLGA-Li+ implants suggests an activated Wnt signaling pathway in vivo

Bone development and regeneration is associated with the Wnt signaling pathway that, according to literature, can be modulated by lithium ions (Li+). The aim of this study was to evaluate the gene expression profile during peri-implant healing of poly(lactic-co-glycolic acid) (PLGA) implants with incorporated Li+, while PLGA without Li+ was used as control, and a special attention was then paid to the Wnt signaling pathway. The implants were inserted in rat tibia for 7 or 28 days and the gene expression profile was investigated using a genome-wide microarray analysis. The results were verified by qPCR and immunohistochemistry. Histomorphometry was used to evaluate the possible effect of Li+ on bone regeneration. The microarray analysis revealed a large number of significantly differentially regulated genes over time within the two implant groups. The Wnt signaling pathway was significantly affected by Li+, with approximately 34% of all Wnt-related markers regulated over time, compared to 22% for non-Li+ containing (control; Ctrl) implants. Functional cluster analysis indicated skeletal system morphogenesis, cartilage development and condensation as related to Li+. The downstream Wnt target gene, FOSL1, and the extracellular protein-encoding gene, ASPN, were significantly upregulated by Li+ compared with Ctrl. The presence of β-catenin, FOSL1 and ASPN positive cells was confirmed around implants of both groups. Interestingly, a significantly reduced bone area was observed over time around both implant groups. The presence of periostin and calcitonin receptor-positive cells was observed at both time points. This study is to the best of the authors' knowledge the first report evaluating the effect of a local release of Li+ from PLGA at the fracture site. The present study shows that during the current time frame and with the present dose of Li+ in PLGA implants, Li+ is not an enhancer of early bone growth, although it affects the Wnt signaling pathway.

Tuning the degradation rate of calcium phosphate cements by incorporating mixtures of polylactic-co-glycolic acid microspheres and glucono-delta-lactone microparticles

Calcium phosphate cements (CPCs) are frequently used as synthetic bone graft materials in view of their excellent osteocompatibility and clinical handling behavior. Hydroxyapatite-forming CPCs, however, degrade at very low rates, thereby limiting complete bone regeneration. The current study has investigated whether degradation of apatite-forming cements can be tuned by incorporating acid-producing slow-resorbing poly(D,L-lactic-co-glycolic) acid (PLGA) porogens, fast-resorbing glucono-delta-lactone (GDL) porogens, or mixtures thereof. The physicochemical, mechanical, and degradation characteristics of these CPC formulations were systematically analyzed upon soaking in phosphate-buffered saline (PBS). In parallel, various CPC formulations were implanted intramuscularly and orthotopically on top of the transverse process of goats followed by analysis of the soft tissue response and bone ingrowth after 12 weeks. In vitro degradation of GDL was almost completed after 2 weeks, as evidenced by characterization of the release of gluconic acid, while PLGA-containing CPCs released glycolic acid throughout the entire study (12 weeks), resulting in a decrease in compression strength of CPC. Extensive in vitro degradation of the CPC matrix was observed upon simultaneous incorporation of 30% PLGA-10% GDL. Histomorphometrical evaluation of the intramuscularly implanted samples revealed that all CPCs exhibited degradation, accompanied by an increase in capsule thickness. In the in vivo goat transverse process model, incorporation of 43% PLGA, 30% PLGA-5% GDL, and 30% PLGA-10% GDL in CPC significantly increased bone formation and resulted in higher bone height compared with both 10% GDL and 20% GDL-containing CPC samples.

The dominant role of IL-8 as an angiogenic driver in a three-dimensional physiological tumor construct for drug testing

The induction of angiogenesis and the promotion of tumor growth and invasiveness are processes critical to metastasis, and are dependent on reciprocal interactions between tumor cells and their microenvironment. The formation of a clinically relevant tumor requires support from the surrounding stroma, and it is hypothesized that three-dimensional (3D) tumor coculture models offer a microenvironment that more closely resembles the physiological tumor microenvironment. In this study, we investigated the effects of tissue-engineered 3D architecture and tumor-stroma interaction on the angiogenic factor secretion profiles of U2OS osteosarcoma cells by coculturing the tumor cells with immortalized fibroblasts or human umbilical vein endothelial cells (HUVECs). We also carried out Transwell migration assays for U2OS cells grown in monoculture or fibroblast coculture systems to study the physiological effect of upregulated angiogenic factors on endothelial cell migration. Anti-IL-8 and anti-vascular endothelial growth factor (VEGF)-A therapies were tested out on these models to investigate the role of 3D culture and the coculture of tumor cells with immortalized fibroblasts on the efficacy of antiangiogenic treatments. The coculture of U2OS cells with immortalized fibroblasts led to the upregulation of IL-8 and VEGF-A, especially in 3D culture. Conversely, coculture with endothelial cells resulted in the downregulation of VEGF-A for cells seeded in 3D scaffolds. The migration of HUVECs through the Transwell polycarbonate inserts increased for the 3D and immortalized fibroblast coculture models, and the targeted inhibition of IL-8 greatly reduced HUVEC migration despite the presence of VEGF-A. A similar effect was not observed when anti-VEGF-A neutralizing antibody was used instead, suggesting that IL-8 plays a more critical role in endothelial cell migration than VEGF-A, with significant implications on the clinical utility of antiangiogenic therapy targeting VEGF-A.

Use of ginsenoside Rg3-loaded electrospun PLGA fibrous membranes as wound cover induces healing and inhibits hypertrophic scar formation of the skin

Prevention of hypertrophic scar formation of the skin requires a complex treatment process, which mainly includes promoting skin regeneration in an early stage while inhibiting hypertrophic formation in a later stage. Electrospinning PLGA with the three-dimensional micro/nano-fibrous structure and as drugs carrier, could be used as an excellent skin repair scaffold. However, it is difficult to combine the advantage of nanofibrous membranes and drug carriers to achieve early and late treatment. In this study, Ginsenoside-Rg3 (Rg3) loaded hydrophilic poly(D,L-lactide-co-glycolide) (PLGA) electrospun fibrous membranes coated with chitosan (CS) were fabricated by combining electrospinning and pressure-driven permeation (PDP) technology. The PDP method was able to significantly improve the hydrophilicity of electrospun fibrous membranes through surface coating of the hydrophilic fibers with CS, while maintaining the Rg3 releasing rate of PLGA electrospun fibrous membranes. Experimental wounds of animal covered with PDP treated fibrous membranes completely re-epithelialized and healed 3-4 days earlier than the wounds in control groups. Scar elevation index (SEI) measurements and histologic characteristics revealed that Rg3 significantly inhibited scar formation 28 days post-surgery. Moreover, RT-PCR assays and western blot analysis revealed that at day 28 after wound induction the expression of VEGF, mRNA and Collagen Type I in the scars treated with Rg3 was decreased compared to control groups. Taken together PLGA-Rg3/CS electrospun fibrous membranes induced repair of tissue damage in the early stage and inhibited scar formation in the late stage of wound healing. These dual-functional membranes present a combined therapeutic approach for inhibiting hypertrophic scars of the skin.