Polycaprolactone-tricalcium Phosphate Research Articles

Alveolar Ridge Augmentation with a Novel Combination of 3D-Printed Scaffolds and Adipose-Derived Mesenchymal Stem Cells-A Pilot Study in Pigs.

Alveolar ridge augmentation is an important dental procedure to increase the volume of bone tissue in the alveolar ridge before the installation of a dental implant. To meet the high demand for bone grafts for alveolar ridge augmentation and to overcome the limitations of autogenous bone, allografts, and xenografts, researchers are developing bone grafts from synthetic materials using novel fabrication techniques such as 3D printing. To improve the clinical performance of synthetic bone grafts, stem cells with osteogenic differentiation capability can be loaded into the grafts. In this pilot study, we propose a novel bone graft which combines a 3D-printed polycaprolactone-tricalcium phosphate (PCL-TCP) scaffold with adipose-derived mesenchymal stem cells (AD-MSCs) that can be harvested, processed and implanted within the alveolar ridge augmentation surgery. We evaluated the novel bone graft in a porcine lateral alveolar defect model. Radiographic analysis revealed that the addition of AD-MSCs to the PCL-TCP scaffold improved the bone volume in the defect from 18.6% to 28.7% after 3 months of healing. Histological analysis showed the presence of AD-MSCs in the PCL-TCP scaffold led to better formation of new bone and less likelihood of fibrous encapsulation of the scaffold. Our pilot study demonstrated that the loading of AD-MSCs improved the bone regeneration capability of PCL-TCP scaffolds, and our novel bone graft is suitable for alveolar ridge augmentation.

Protocol for the BONE-RECON trial: a single-arm feasibility trial for critical sized lower limb BONE defect RECONstruction using the mPCL-TCP scaffold system with autologous vascularised corticoperiosteal tissue transfer

IntroductionReconstruction of critical bone defects is challenging. In a substantial subgroup of patients, conventional reconstructive techniques are insufficient. Biodegradable scaffolds have emerged as a novel tissue engineering strategy for critical-sized...

TREATMENT OF VERY LARGE TRAUMATIC BONE DEFECTS WITH A BIODEGRADABLE POLYCAPROLACTONE-TRICALCIUM PHOSPHATE 3D-PRINTED SCAFFOLD: A REVIEW OF THREE CLINICAL CASES

The need for an artificial scaffold in very large bone defects is clear, not only to limit the risk of graft harvesting, but also to improve clinical success. The use of custom osteoconductive scaffolds made from biodegradable polyester and ceramics can be a valuable patient friendly option, especially in case of a concomitant infection.Multiple types of scaffolds for the Masquelet procedure (MP) are available, however these frequently demonstrate central graft involution when defects exceed a certain size and the complication rates remains high. This paper describes three infected tibial defect nonunions with a segmental defect over ten centimeters long treated with a customized 3D printed polycaprolactone-tricalcium phosphate (PCL-TCP) cage in combination with biological adjuncts.Three male patients, between the age of 37 and 47, were treated for an infected tibial defect nonunion after sustaining Gustilo grade 3 open fractures. All had a segmental midshaft bone defect of more than ten centimeters (range 11–15cm). First stage MPs consisted of extensive debridement, external fixation and placement of anterior lateral thigh flaps (ALT). Positive cultures were obtained from all patients during this first stage, that were treated with specific systemic antibiotics during 12 weeks. The second stage MP was carried out at least two months after the first stage. CT scans were obtained after the first stage to manufacture defect-specific cages. In the final procedure a custom 3D printed PCL-TCP cage (Osteopore, Singapore) was placed in the defect in combination with biological adjuncts (BMAC, RIA derived autograft, iFactor and BioActive Glass). Bridging of the defect, assessed at six months by CT, was achieved in all cases. SPECT-scans 6 months post-operatively demonstrated active bone regeneration, also involving the central part of the scaffold. All three patients regained function and reported less pain with full weight-bearing.This case report shows that 3D printed PCL-TCP cages in combination with biological adjuncts is a novel addition to the surgical treatment of very large bone defects in (infected) posttraumatic nonunion of the tibia. This combination could overcome some of the current drawbacks in this challenging indication.

Clinical translation of a patient-specific scaffold-guided bone regeneration concept in four cases with large long bone defects.

BackgroundBone defects after trauma, infection, or tumour resection present a challenge for patients and clinicians. To date, autologous bone graft (ABG) is the gold standard for bone regeneration. To address the limitations of ABG such as limited harvest volume as well as overly fast remodelling and resorption, a new treatment strategy of scaffold-guided bone regeneration (SGBR) was developed. In a well-characterized sheep model of large to extra-large tibial segmental defects, three-dimensional (3D) printed composite scaffolds have shown clinically relevant biocompatibility and osteoconductive capacity in SGBR strategies. Here, we report four challenging clinical cases with large complex posttraumatic long bone defects using patient-specific SGBR as a successful treatment.MethodsAfter giving informed consent computed tomography (CT) images were used to design patient-specific biodegradable medical-grade polycaprolactone-tricalcium phosphate (mPCL-TCP, 80:20 ​wt%) scaffolds. The CT scans were segmented using Materialise Mimics to produce a defect model and the scaffold parts were designed with Autodesk Meshmixer. Scaffold prototypes were 3D-printed to validate robust clinical handling and bone defect fit. The final scaffold design was additively manufactured under Food and Drug Administration (FDA) guidelines for patient-specific and custom-made implants by Osteopore International Pte Ltd.ResultsFour patients (age: 23–42 years) with posttraumatic lower extremity large long bone defects (case 1: 4 ​cm distal femur, case 2: 10 ​cm tibia shaft, case 3: complex malunion femur, case 4: irregularly shaped defect distal tibia) are presented. After giving informed consent, the patients were treated surgically by implanting a custom-made mPCL-TCP scaffold loaded with ABG (case 2: additional application of recombinant human bone morphogenetic protein-2) harvested with the Reamer-Irrigator-Aspirator system (RIA, Synthes®). In all cases, the scaffolds matched the actual anatomical defect well and no perioperative adverse events were observed. Cases 1, 3 and 4 showed evidence of bony ingrowth into the large honeycomb pores (pores >2 ​mm) and fully interconnected scaffold architecture with indicative osseous bridges at the bony ends on the last radiographic follow-up (8–9 months after implantation). Comprehensive bone regeneration and full weight bearing were achieved in case 2 ​at follow-up 23 months after implantation.ConclusionThis study shows the bench to bedside translation of guided bone regeneration principles into scaffold-based bone tissue engineering. The scaffold design in SGBR should have a tissue-specific morphological signature which stimulates and directs the stages from the initial host response towards the full regeneration. Thereby, the scaffolds provide a physical niche with morphology and biomaterial properties that allow cell migration, proliferation, and formation of vascularized tissue in the first one to two months, followed by functional bone formation and the capacity for physiological bone remodelling. Great design flexibility of composite scaffolds to support the one to three-year bone regeneration was observed in four patients with complex long bone defects.The translational potential of this articleThis study reports on the clinical efficacy of SGBR in the treatment of long bone defects. Moreover, it presents a comprehensive narrative of the rationale of this technology, highlighting its potential for bone regeneration treatment regimens in patients with any type of large and complex osseous defects.

A Porcine Model Using Adipose Stem Cell-Loaded Scaffolds for Alveolar Ridge Augmentation.

Tooth loss greatly affects a person's quality of life and many turn to dental implants to replace lost teeth. The success of a dental implant depends on the amount of alveolar bone supporting the implant, and thus, bone augmentation is often necessary to preserve or build up bone volume in the alveolar ridge. Bone can be augmented with autogenous bone, allografts, or xenografts, but the limitations of such natural bone grafts prompt researchers to develop synthetic scaffolds supplemented with cells and/or bioactive agents as alternative bone grafts. The translation of these combination scaffolds from the laboratory to the clinic requires reliable experimental models that can simulate the clinical conditions in human patients. In this article, we describe the use of a porcine alveolar defect model as a platform to evaluate the efficacy of a novel combination of a three-dimensional-printed polycaprolactone-tricalcium phosphate (PCL-TCP) scaffold and adipose-derived mesenchymal stem cells (AD-MSCs) in lateral alveolar augmentation. The surgical protocol for the defect creation and regenerative surgery, as well as analytical methods to determine the extent of tissue regeneration, are described and discussed.

Tissue Engineering and Regenerative Medicine Cranioplasty Using Polycaprolactone-Tricalcium Phosphate: Management and Treatment Outcomes

ABSTRACTBACKGROUNDCranioplasty is a procedure commonly performed as the next step in management for patients with decompressive craniectomy. It is commonly associated with complications that might result in implant failure and reoperation. Tissue engineering and regenerative medicine (TERM) involve the development of biological substitutes that restore tissue function and regrow and replace damaged tissues. TERM is a potential solution that might allow for improved long-term outcomes in cranioplasty.OBJECTIVETo present a case series that describes the management and treatment outcomes of using TERM in cranioplasty, using polycaprolactone-tricalcium phosphate (PCL-TCP) implants in 2 patients.METHODSIn 2 young adults, large bone defects of the skull following decompressive craniectomy were reconstructed using patient-specific implants manufactured from PCL-TCP. Bone marrow aspirate was used as autologous biologic that incorporates stem cell and growth factors into the implant.RESULTSBoth patients recovered without any complications following surgery. Physical examination shows favorable healing outcomes with the defect area having a hard texture upon palpation. Postoperative imaging performed at 8 and 20 months for each patient, respectively, demonstrated ossification over the defect area.CONCLUSIONSatisfactory bone growth is seen with TERM cranioplasty. The PCL-TCP implant is a novel and recommendable alternative to currently available patient-specific implants used in cranioplasty. TERM cranioplasty is the potential solution to the quest of finding the ideal cranioplasty implant.

Synergistic Effect of PVDF-Coated PCL-TCP Scaffolds and Pulsed Electromagnetic Field on Osteogenesis.

Bone exhibits piezoelectric properties. Thus, electrical stimulations such as pulsed electromagnetic fields (PEMFs) and stimuli-responsive piezoelectric properties of scaffolds have been investigated separately to evaluate their efficacy in supporting osteogenesis. However, current understanding of cells responding under the combined influence of PEMF and piezoelectric properties in scaffolds is still lacking. Therefore, in this study, we fabricated piezoelectric scaffolds by functionalization of polycaprolactone-tricalcium phosphate (PCL-TCP) films with a polyvinylidene fluoride (PVDF) coating that is self-polarized by a modified breath-figure technique. The osteoinductive properties of these PVDF-coated PCL-TCP films on MC3T3-E1 cells were studied under the stimulation of PEMF. Piezoelectric and ferroelectric characterization demonstrated that scaffolds with piezoelectric coefficient d33 = −1.2 pC/N were obtained at a powder dissolution temperature of 100 °C and coating relative humidity (RH) of 56%. DNA quantification showed that cell proliferation was significantly enhanced by PEMF as low as 0.6 mT and 50 Hz. Hydroxyapatite staining showed that cell mineralization was significantly enhanced by incorporation of PVDF coating. Gene expression study showed that the combination of PEMF and PVDF coating promoted late osteogenic gene expression marker most significantly. Collectively, our results suggest that the synergistic effects of PEMF and piezoelectric scaffolds on osteogenesis provide a promising alternative strategy for electrically augmented osteoinduction. The piezoelectric response of PVDF by PEMF, which could provide mechanical strain, is particularly interesting as it could deliver local mechanical stimulation to osteogenic cells using PEMF.

Osteogenesis of 3D-Printed PCL/TCP/bdECM Scaffold Using Adipose-Derived Stem Cells Aggregates; An Experimental Study in the Canine Mandible.

Three-dimensional (3D) printing is perceived as an innovative tool for change in tissue engineering and regenerative medicine based on research outcomes on the development of artificial organs and tissues. With advances in such technology, research is underway into 3D-printed artificial scaffolds for tissue recovery and regeneration. In this study, we fabricated artificial scaffolds by coating bone demineralized and decellularized extracellular matrix (bdECM) onto existing 3D-printed polycaprolactone/tricalcium phosphate (PCL/TCP) to enhance osteoconductivity and osteoinductivity. After injecting adipose-derived stem cells (ADSCs) in an aggregate form found to be effective in previous studies, we examined the effects of the scaffold on ossification during mandibular reconstruction in beagle dogs. Ten beagles were divided into two groups: group A (PCL/TCP/bdECM + ADSC injection; n = 5) and group B (PCL/TCP/bdECM; n = 5). The results were analyzed four and eight weeks after intervention. Computed tomography (CT) findings showed that group A had more diffuse osteoblast tissue than group B. Evidence of infection or immune rejection was not detected following histological examination. Goldner trichrome (G/T) staining revealed rich ossification in scaffold pores. ColI, Osteocalcin, and Runx2 gene expressions were determined using real-time polymerase chain reaction. Group A showed greater expression of these genes. Through Western blotting, group A showed a greater expression of genes that encode ColI, Osteocalcin, and Runx2 proteins. In conclusion, intervention group A, in which the beagles received the additional ADSC injection together with the 3D-printed PCL/TCP coated with bdECM, showed improved mandibular ossification in and around the pores of the scaffold.

Comparative Craniofacial Bone Regeneration Capacities of Mesenchymal Stem Cells Derived from Human Neural Crest Stem Cells and Bone Marrow.

Most craniofacial bones are derived from the ectodermal germ layer via neural crest stem cells, which are distinct from mesoderm-derived long bones. However, current craniofacial bone tissue engineering approaches do not account for this difference and utilize mesoderm-derived bone marrow mesenchymal stem cells (BM-MSCs) as a paradigm cell source. The effect of the embryonic origin (ontogeny) of an MSC population on its osteogenic differentiation potential and regenerative ability still remains unresolved. To clarify the effects of MSC ontogeny on bone regenerative ability, we directly compared the craniofacial bone regenerative abilities of an ecto-mesenchymal stem cell (eMSC) population, which is derived from human embryonic stem cells via a neural crest intermediate, with mesodermal adult BM-MSCs. eMSCs showed comparable osteogenic and chondrogenic ability to BM-MSCs in 2-D in vitro culture, but lower adipogenic ability. They exhibited greater proliferation than BM-MSCs and comparable construct mineralization in a well-established 3-D polycaprolactone-tricalcium phosphate (PCL-TCP) scaffold system in vitro. eMSC-derived 3D osteogenic constructs were maintained for longer in a proliferative osteoblast state and exhibited differential levels of genes related to fibroblast growth factor (FGF) signaling compared to BM-MSCs. Although both eMSC and BM-MSC-seeded scaffold constructs could promote bone regeneration in a rat calvarial defect model, eMSC-derived osseous constructs had significantly higher cellularity due to increased number of proliferative (Ki67+) cells than those seeded with BM-MSCs, and exhibited enhanced new bone formation in the defect area as compared to untreated controls. Overall, our study demonstrates the potential of human eMSCs for future clinical use in craniofacial regeneration applications and indicates the importance of considering MSC origin when selecting an MSC source for regenerative applications.

Comparative studies on thin polycaprolactone-tricalcium phosphate composite scaffolds and its interaction with mesenchymal stem cells

BackgroundHybrid scaffolds combining biodegradable polymers and ceramic particles for control of cell adhesion and proliferation are interesting materials for tissue engineering applications. Combinations of biodegradable polymers and ceramics are to provide higher beneficial functionalities to tissue engineering scaffolds with addition of different cell specific bio-factors. Many such hybrid combinations have been reported by several researchers around the world by using various methods and solvents as well as bioactive matrix polymers to fabricate such biomaterials. However, thin hybrid scaffolds with high porosity, cell adhesion factors and biodegradability, as well as the ability to support stem cells often require tedious processes like electrospinning, freeze drying, etc. A simple method to develop porous biodegradable hybrid scaffolds with proper cell adhesion factors is still the need of the hour in tissue engineering and regenerative medicine.MethodThin biodegradable poly(ε-caprolactone) (PCL) based hybrid scaffolds were developed in combination with α-tricalcium phosphate (TCP) particles, gelatin and fibronectin separately and the fabricated scaffolds were evaluated systematically using human mesenchymal stem cells (hMSCs) for tissue engineering applications. A simple modified solvent casting method combined with gas foaming process was used to develop porous thin hybrid structures and compared their properties with those of corresponding non-porous hybrid scaffolds. The TCP particles distribution, morphology, biodegradability and functional groups of the different hybrid scaffolds were analyzed using energy-dispersive X-ray spectroscopy (EDX), light microscopy/scanning electron microscopy (SEM), buffer solutions and Fourier-transform infrared spectroscopy (FTIR), respectively The cellular and tissue regeneration behaviors such as in vitro cell attachment (live/dead assay), cell proliferation (CCK-8 assay) and histological studies were performed using hMSCs.ResultsThin PCL-based hybrid scaffolds were fabricated using modified solvent casting method. Homogeneous distribution of TCP particles in the scaffolds were confirmed by EDX. Cellular interactions of the hybrid scaffolds demonstrated overall higher cell adhesion, proliferation and tissue regeneration on the non-porous thin films of PCL-TCP, PCL-TCP-gelatin and PCL-TCP-fibronectin. Coating of fibronectin was remarkable in induction of cell adhesion and proliferation.ConclusionsThe experimental results revealed that diversely designed PCL-TCP thin hybrid films showed high cell interaction and proliferation with hMSCs. From the results of the cell viability, attachment, proliferation and histological analyses as well as their biodegradation and coating effects, we conclude that these thin PCL-TCP hybrid films are suitable for tissue engineering applications.

Collagen and mPCL-TCP scaffolds induced differential bone regeneration in ovary-intact and ovariectomized rats.

The data on biomaterial-mediated bone regeneration directly comparing commercially available scaffolds in aging and osteoporotic conditions remain sparse. To investigate the effects of an absorbable collagen sponge (ACS) and a medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) scaffold on calvarial defect healing in ovary-intact and ovariectomized rats. Forty-two, 5-month old female Sprague-Dawley rats were divided into sham (OVI) or ovariectomy (OVX) groups (n=21). When rats reached 6 months old, 7mm diameter calvarial defects were created and treated, further dividing each group into blood clot control, mPCL-TCP, or ACS subgroups (n=7). After four weeks, the calvarial specimens were evaluated using micro-computed tomography for bone volume fraction (BVF), and histopathology. The effects of ovariectomy were confirmed by changes in body, uterine, and vaginal weight, and osteopenia in the femur. A significant increase in BVF was observed in ACS-subgroups compared with their respective control groups (p<0.05). Histopathological analysis revealed no cellular inflammatory infiltrate in any group. Fibrous tissue encapsulated the mPCL-TCP, while the ACS was well-integrated with the bone matrix. The OVX groups presented more osteoid and enlarged marrow cavities compared with the OVI groups. ACS scaffold enhanced calvarial bone regeneration in OVI and OVX rats after four weeks.

Effect of expanded bone marrow-derived osteoprogenitor cells seeded into polycaprolactone/tricalcium phosphate scaffolds in new bone regeneration of rabbit mandibular defects.

The purpose of this study was to assess and evaluate new bone formation in rabbit marginal mandibular defects using expanded bone marrow-derived osteoprogenitor cells seeded in three-dimensional scaffolds of polycaprolactone/tricalcium phosphate (PCL/TCP). Bone marrow was harvested from the rabbit ilium and rabbit bone marrow-derived osteoprogenitor cells were isolated and expanded in standard culture medium and osteogenic medium supplement. The cells were then seeded into the PCL/TCP scaffolds and the cell/scaffold constructions were implanted into prepared defects in rabbit mandibles. PCL/TCP scaffold alone and autogenous bone graft from the mandible were also implanted into the other prepared defects. The specimens were evaluated at 4 and 8 weeks after the implantation using clinical, radiographic, and histological techniques. The results of the experimental group demonstrated more newly formed bone on the surface and in the pores of the PCL/TCP scaffolds. In addition, the osteoblasts, osteocytes, and new bone trabeculae were identified throughout the defects that were implanted with the cell/scaffold constructions. The PCL/TCP alone group was filled mostly with fibrous cells particularly in the middle region with less bone formation. These results would suggest that the derived osteotoprogenitor cells have the potential to form bone tissue when seeded onto PCL/TCP scaffolds.

A pilot study: Clinical efficacy of novel polycaprolactone-tricalcium phosphate membrane for guided bone regeneration in rabbit calvarial defect model

In this pilot study, we aim to investigate the clinical efficacy of a novel polycaprolactone-tricalcium phosphate (PCL-TCP) membrane for guided bone regeneration (GBR) in an in vivo model. Eight rabbits, each with two surgically created calvarial defects were reconstructed using a bovine particulate bone substitute, then covered with a mechanical barrier using a PCL-TCP or collagen membrane, or left uncovered without any membrane. The rabbits were sacrificed at 1 and 2 months and the reconstructed defects were harvested for histology and histomorphometry evaluations. Results showed no statistical significance in percentage bone area fraction (BAF%) between the PCL-TCP and collagen membranes at 1 and 2 months. The BAF% of the PCL-TCP membrane group was statistically higher at 2 months compared to 1 month (p<.05); the BAF% in the collagen membrane group did not increase significantly from the first to second months (p>.05). We postulate that this is attributed to the greater stiffness and slower degradation of PCL-TCP. We conclude that the novel PCL-TCP membrane is as effective as the commercially available collagen membrane as a mechanical barrier for GBR, with good handling characteristics. Future work should explore variations in PCL-TCP composition to further improve its usability and rate of desired degradation.

A humanised tissue-engineered bone model allows species-specific breast cancer-related bone metastasis in vivo.

Bone metastases frequently occur in the advanced stages of breast cancer. At this stage, the disease is deemed incurable. To date, the mechanisms of breast cancer-related metastasis to bone are poorly understood. This may be attributed to the lack of appropriate animal models to investigate the complex cancer cell-bone interactions. In this study, two established tissue-engineered bone constructs (TEBCs) were applied to a breast cancer-related metastasis model. A cylindrical medical-grade polycaprolactone-tricalcium phosphate scaffold produced by fused deposition modelling (scaffold 1) was compared with a tubular calcium phosphate-coated polycaprolactone scaffold fabricated by solution electrospinning (scaffold 2) for their potential to generate ectopic humanised bone in NOD/SCID mice. While scaffold 1 was found not suitable to generate a sufficient amount of ectopic bone tissue due to poor ectopic integration, scaffold 2 showed excellent integration into the host tissue, leading to bone formation. To mimic breast cancer cell colonisation to the bone, MDA-MB-231, SUM1315, and MDA-MB-231BO breast cancer cells were cultured in polyethylene glycol-based hydrogels and implanted adjacent to the TEBCs. Histological analysis indicated that the breast cancer cells induced an osteoclastic reaction in the TEBCs, demonstrating analogies to breast cancer-related bone metastasis seen in patients.

Comparison of titanium mesh versus polycaprolactone-tricalcium phosphate implant in orbital fracture reconstruction

Background: Controversy exists regarding the choice of implant material for orbital floor reconstructions. This study aims to compare the effectiveness of titanium mesh and polycaprolactone-tricalcium phosphate (PCL/TCP) implant for repairing traumatic orbital fractures. Methods: A total of 19 patients with orbital floor reconstructions operated at the National University Health System, Singapore were included in this prospective study between November 2010 and June 2013. Titanium mesh was used in 10 patients, while PCL/TCP implant was used in the other nine patients. Patients were evaluated for the worsening of visual acuity, presence or absence of infraorbital nerve paraesthesia, extraocular muscle function, enophthalmos and diplopia. Postoperative complications such as infection, early resorption, extrusion and persistent pain were also recorded. Results: Restoration of orbital wall continuity was successful in all patients. Follow-up duration was at least one year. There was no statistically significant difference in worsening of visual acuity, presence or absence of infraorbital nerve paraesthesia, extraocular muscle function and enophthalmos. Even though there was no statistically significant difference in diplopia between the two treatment groups preoperatively, there were more patients who had diplopia following titanium mesh postoperatively (P < 0.05). One patient had persistent diplopia, enopthalmos and lateral rectus muscle dysfunction postoperatively, but declined further corrective surgery. There was no infection, early resorption, extrusion or persistent pain. Conclusions: Both groups showed satisfactory results. PCL/TCP composite can be used to fabricate biodegradable fixators for the reconstruction of orbital wall fractures.

Enhanced osteogenic gene expression in microcarrier-bound scalably expanded fetal bone marrow MSCS

Mesenchymal stem cell (MSC) therapy is a promising strategy to address the unmet clinical need for improved bone regeneration. However, challenges to the scalable stem cell production hinder the clinical translation of MSC therapy. Furthermore, the effects of scalable microcarrier-based culture and enzymatic cell harvest on the phenotype and molecular identity of MSCs upon directed osteogenic differentiation are not well understood. In order to address these issues, we expanded fetal bone marrow MSCs on either commercially-available microcarriers in spinner flask culture or on control tissue culture plastic (TCP) monolayer surfaces. At the end of this expansion, we characterized the phenotype of microcarrier- or TCP monolayer-expanded MSCs in terms of cytokine, gene and surface marker expression. We then differentiated microcarrier-bound, microcarrier-harvested or plastic-harvested MSCs which were seeded onto collagen-coated plates or polycaprolactone-tricalcium phosphate scaffolds. In both cases, microcarrier-bound MSCs displayed increased expression of osteogenic genes such as RUNX2 and ALPL compared to microcarrier-harvested and plastic-harvested cells upon osteogenic induction. These results indicate that microcarrier-bound MSCs undergo enhanced osteogenic differentiation. Our findings also suggest that compared to conventional methods of delivering MSC cell suspensions that were harvested either from microcarriers cultured in agitated bioreactors or from TCP surfaces, in vivo delivery of MSC-bound microcarriers may present a promising method for bone regeneration.

A polycaprolactone-tricalcium phosphate composite scaffold as an autograft-free spinal fusion cage in a sheep model

Titanium (Ti) based spinal fusion cages are frequently used in the clinics for the treatment of spinal degeneration and related diseases, however, their further clinical application is generally harassed by several drawbacks such as stress shielding, non-biodegradability and additional bone grafting procedure. Our earlier work has demonstrated the efficacy of a biodegradable macro-porous polycaprolactone-tricalcium phosphate (PCL-TCP) composite scaffold in promoting bony tissue ingrowth as well as its ability to sustain mechanical loads upon implantation into an orthotopic defect site. In this study, we investigated the use of PCL-TCP scaffold as an autograft-free spinal fusion cage in a preclinical sheep model over 12 months, and compared the fusion efficacy against Ti cages incorporated with autografts. Results showed that despite PCL-TCP scaffold as an autograft-free cage attaining a slower fusion rate at early stage (6 month), it achieved similar degree of spinal fusion efficacy as Ti cages aided with autograft at 12 month post-operation as evidenced by the radiographic and histological evaluation. PCL-TCP cages alone demonstrated better bone ingrowth with 2.6 fold higher bone/interspace ratio (B/I) and more homogeneous bone tissue distribution compared with that of the Ti cages (88.10 ± 3.63% vs. 33.74 ± 2.78%, p < 0.05) as seen from the histological and micro-CT analysis. Moreover, besides the bone tissue ingrowth, a quantitative approach was illustrated to accurately evaluate the osteointegration of fusion cage with surrounding bone tissue, and showed a 1.36 fold higher degree of osteointegration occurred in PCL-TCP cage group than Ti cage group (CS/PC: 79.31 ± 3.15% vs 58.44 ± 2.43%, p < 0.05). Furthermore, biomechanical analysis showed comparable mechanical strength of fused segments in both groups in terms of the range of motion and stiffness at 12 month (p > 0.05). The degradation profile of the PCL-TCP cages was noted to increase in tandem with new bone ingrowth into the pores, while maintaining good structural integrity necessary for supporting the spinal interbody segments. Therefore, with the better osteointegration, more bone tissue ingrowth as well as its favorable biodegradable and radiolucent properties, PCL-TCP cage has been demonstrated to be a promising candidate as an autograft-free fusion cage for clinical application.

Effects of scaffold architecture on cranial bone healing

In the present study, polycaprolactone–tricalcium phosphate (PCL/TCP) scaffolds with two different fibre laydown patterns, which were coated with hydroxyapatite and gelatine, were used as an approach for optimizing bone regeneration in a critical-sized calvarial defect. After 12 weeks, bone regeneration was quantified using microcomputed tomography (micro-CT) analysis, biomechanical testing, and histological evaluation. Notably, the experimental groups with coated scaffolds showed lower bone formation and lower biomechanical properties within the defect compared to the uncoated scaffolds. Surprisingly, the different laydown pattern of the fibres resulted in different bone formation and biomechanical properties: the 0°/60°/120° scaffolds revealed lower bone formation and biomechanical properties compared to the 0°/90° scaffolds in all the experimental groups. Therefore, future bone regeneration strategies utilizing scaffolds should consider scaffold architecture as an important factor during the scaffold optimization stages in order to move closer to a clinical application.

The use of a polycaprolactone–tricalcium phosphate scaffold for bone regeneration of tooth socket facial wall defects and simultaneous immediate dental implant placement in Macaca fascicularis

Bone regeneration and aesthetic outcomes may be compromised when immediate implants are placed at extraction sites with dehiscence defects. The aim of this study was to compare, in a monkey model, peri-implant bone regeneration and implant stability after immediate implant placement into tooth sockets with facial wall defects in two treatment groups. In eight control monkeys, the bony defect was reconstructed with autogenous particulate bone, whereas in 10 test monkeys a polycaprolactone-tricalcium phosphate (PCL-TCP) scaffold was used. The monkeys were sacrificed after 6 months and the specimens were analyzed by histology and histomorphometry. Better maintenance of facial bone contour was noted in the test group; however, bone regeneration was seen only at areas adjacent to a bony wall of the defect. The mean bone-to-implant contact was 27.6 ± 19.1% (control group) versus 6.8 ± 7.9% (test group). The mean bone area percentage was 11.8 ± 10.1% (control group) versus 6.8 ± 6.9% (test group). Implant survival was 100% at 6 months for both the groups. It was concluded that although the use of a PCL-TCP scaffold showed better maintenance of the alveolar contour as compared to autogenous particulate bone at 6 months, there was minimal bone regeneration within the defect.

The effect of PCL‐TCP scaffold loaded with mesenchymal stem cells on vertical bone augmentation in dog mandible: A preliminary report

Polycaprolactone-tricalcium phosphate (PCL-TCP), a new composite scaffold, has been shown to facilitate early revascularization and speed up bone regeneration process. The objective of this study was to evaluate the effect of PCL-TCP seeded with mesenchymal stem cells (MSCs) on healing of the vertical bone critical sized defect in dog's mandible. Bone marrow aspirate from dog humerous was cultured and the stemness of the cells was examined by differentiation staining methods and flow cytometric analysis. Third passage subculture cells (5 × 10⁵ cells) were loaded on 20 × 10 × 10 mm³ and incubated for 48 h. The presence of MSCs in the pores was evaluated by scanning electron microscope. Bilateral mandibular premolar teeth were extracted in four dogs and the buccal and lingual bone plates were reduced to make a vertical defect. Cell-loaded scaffolds were fixed in right side and left side received pure PCL-TCP scaffolds as a control side defects. Histomorphometric analysis after 8 weeks of the scaffold implantation showed higher amount of lamellar bone in the test side (48.63%) than control side (17.27%) (p < 0.05).The results suggest that PCL-TCP may be an appropriate scaffold for loading MSCs in bone regeneration.