Tissue-engineered polymer-based periosteal bone grafts for maxillary sinus augmentation: five-year clinical results

Does the use of platelet-rich plasma in sinus augmentation improve the survival of dental implants? A systematic review and meta-analysis

Background

Platelet-rich plasma is considered an effective modality to promote bone regeneration, improve hard and soft tissue healing in surgical procedures including sinus augmentation. However, the survival of dental implants in sinus augmented sites with platelet-rich plasma has shown equivocal results in recent studies.

Purpose

In this systematic review, data on dental implants' survival in sinus augmentation sites with platelet-rich plasma were examined.

Materials and methods

Randomized controlled trials on the topic with a minimum mean follow-up of 6 months with no language restriction were considered. Other study designs on the topic were excluded. Accordingly, relevant articles were searched in Clinicaltrials.gov, Cochrane databases, PubMed/Medline, and Scopus up to April 2021. Using the Cochrane risk of bias assessment tool, the listed studies' risk of bias was evaluated. From the included studies, the pertinent information was taken and pooled for qualitative and quantitative analysis using R software 4.1.1.

Results

Six randomized controlled trials involving 188 patients who underwent sinus augmentation with and without platelet-rich plasma, and 781 implants were included for qualitative and quantitative analysis. Four hundred and eleven implants were placed in the intervention group (with platelet-rich plasma) and 370 implants were placed in the control group (without platelet-rich plasma). The pooled estimate (OR 0.84, 95% CI 0.37 to 1.91; I2 = 0%) indicated that there was no statistically significant difference observed between the groups. The test for subgroup differences showed no statistically significant differences between the subgroups (p = 0.45) with no heterogeneity (I2 = 0%).

Conclusion

The bias associated with selective reporting of outcome data was considered as some concern for bias. This systematic review revealed that the effect of platelet-rich plasma is uncertain on the survival of dental implants.

Bone Tissue Engineering Using Osteogenic Cells: From the Bench to the Clinical Application

The use of tissue engineering to restore and to build new bone tissue is under active research at present. The following review summarizes the latest studies and clinical trials related to the use of osteogenic cells, biomaterials, and scaffolds to regenerate bone defects in the human jaws. Bone tissue engineering (BTE) combined with scaffolds have provided a range of advantages not only to transport the target cells to their desired destination but also to support the early phases of the mineralization process. The mechanical, chemical, and physical properties of scaffolds have been evaluated as they affect the quantity of bone regeneration, particularly in the oral cavity. This review also highlighted the mechanisms underlying bone homeostasis, including the key transcription factors and signaling pathways responsible for regulating the differentiation of osteoblast lineage. Furthering understanding of the mechanisms of cellular signaling in skeletal remodeling with the use of mesenchymal stem cells and the proper scaffold properties are key-factors to enable the incorporation of new and effective treatment methods into clinical practice for bone tissue regeneration using BTE. Impact Statement The use of mesenchymal stem cells able to differentiate in osteoblast lineage for bone tissue engineering (BTE) remains a major challenge. Viable cells and signaling pathways play an essential role in bone repair and regeneration of critical size defects. Recent advances in scaffolds and biological factors such as growth factors (e.g., cytokines and hormones) controlling the osteogenic signaling cascade are now becoming new players affecting the osteogenic potential of cells. Such techniques will significantly impact the maxillofacial bone tissue replacement, repair, and regeneration for patients without having to rely on donor banks or other surgical sites.

Comparison of the Translational Potential of Human Mesenchymal Progenitor Cells from Different Bone Entities for Autologous 3D Bioprinted Bone Grafts

Reconstruction of segmental bone defects by autologous bone grafting is still the standard of care but presents challenges including anatomical availability and potential donor site morbidity. The process of 3D bioprinting, the application of 3D printing for direct fabrication of living tissue, opens new possibilities for highly personalized tissue implants, making it an appealing alternative to autologous bone grafts. One of the most crucial hurdles for the clinical application of 3D bioprinting is the choice of a suitable cell source, which should be minimally invasive, with high osteogenic potential, with fast, easy expansion. In this study, mesenchymal progenitor cells were isolated from clinically relevant human bone biopsy sites (explant cultures from alveolar bone, iliac crest and fibula; bone marrow aspirates; and periosteal bone shaving from the mastoid) and 3D bioprinted using projection-based stereolithography. Printed constructs were cultivated for 28 days and analyzed regarding their osteogenic potential by assessing viability, mineralization, and gene expression. While viability levels of all cell sources were comparable over the course of the cultivation, cells obtained by periosteal bone shaving showed higher mineralization of the print matrix, with gene expression data suggesting advanced osteogenic differentiation. These results indicate that periosteum-derived cells represent a highly promising cell source for translational bioprinting of bone tissue given their superior osteogenic potential as well as their minimally invasive obtainability.

Cross-sectional analysis of spatial distribution and total amount of harvestable calvarian split bone

BACKGROUND

Bone resorption of the jaw leads to challenging implant placement. Frequently, augmentation of the jaw is necessary. Is calvarian split bone an alternative to other extraoral donor sites and what volume of bone is harvestable? The aim was to evaluate the spatial distribution and the total amount of harvestable calvarian split bone.

MATERIAL AND METHODS

Computerized tomographies of 600 patients were divided into four groups (male and female: ≤45 years and >45 years). The skull was segmented and cut into the harvestable compartments (Os frontale, Ossa parietalia). The volume and thickness of the harvestable bone were calculated.

RESULTS

The overall harvestable bone was 110.644 ± 25.429 cm³. The bone from the Os frontale was significantly less than harvestable bone from the Os parietale (p < 0.001). More bone could be harvested from the right Os parietale. In younger males, significantly more bone could be harvested than in females (females ≤45 years: p = 0.001; females >45 years: p = 0.003). A weak negative correlation existed between the participants' age and the harvestable bone volume of the left Os parietale (r = -0.087; p = 0.033). The thickness of the harvestable bone from the Ossa parietalia is greater in females than in males.

CONCLUSION

A great amount of calvarian bone can be harvested to augment the jaw. Surgeons must acknowledge that more bone is harvestable from males than females while the female bone is thicker. Calculating the volume leads to accurate results of the available bone.

The applications of regenerative medicine in sinus lift procedures: A systematic review

BACKGROUND

Findings in regenerative medicine applied to the sinus lift procedures.

PURPOSE

Evaluate the effectiveness of regenerative medicine in sinus lift.

MATERIALS AND METHODS

An extensive search for manuscripts were performed by using different combinations of keywords and MeSH terms (Pub-med; Embase; Scopus; Web of Science Core Collection; Medline; Current Contents Connect; Derwent Innovations Index; Scielo Citation Index; Cochrane library). The full text selected articles are written in English, Portuguese, Spanish, Italian, German, or French, and published until 28 of November 2016. Inclusion criteria were: implant osteointegration, radiographic, histologic, and/or histomorphometric analysis, clinical studies in humans using of regenerative medicine. This systematic review was performed by selecting only randomized controlled clinical trials and controlled clinical trials.

RESULTS

Eighteen published studies (11 CT and 7 RCT) were considered eligible for inclusion in the present systematic review. These studies demonstrated considerable variation of biomaterial and cell technics used, study design, sinus lift technic, outcomes, follow-up, and results.

CONCLUSION

Only few studies have demonstrated potential of regenerative medicine in sinus lift; further randomized clinical trials are needed to achieve more accurate results.

The Application of Fibrin/Hyaluronic Acid-Poly(l-Lactic-co-Glycolic Acid) Construct in Augmentation Rhinoplasty

Although many graft materials have been used for augmentation rhinoplasty, an ideal graft has not yet been developed. As the field of tissue engineering has been developing, it has been applied to the reconstruction of many organs, but its application in the rhinoplasty field is still limited. This study evaluated the utility of allogenic chondrocytes with fibrin/hyaluronic acid (HA)-poly(l-lactic-co-glycolic acid) (PLGA) constructs in augmentation rhinoplasty. Chondrocytes from rabbit auricular cartilage were isolated and cultured with fibrin/HA hydrogels and implanted into PLGA scaffolds. After 8 weeks of in vitro culture, the scaffolds were implanted in the nasal dorsum of six rabbits. Eight weeks postoperatively, the implanted sites were evaluated with gross, radiologic, and histologic analysis. In vitro, more than 90% of the seeded chondrocytes in the PLGA scaffolds survived for 2 weeks, and they produced a large amount of extracellular matrix and were well differentiated. The grafts maintained their initial shape for 8 weeks after implantation. Radiological and histological evaluations showed that the structure was well maintained with minimal inflammatory response and appropriate elevation levels. However, the formation of neo-chondrocytes was not observed. PLGA scaffolds seeded with fibrin/HA and allogenic chondrocytes can be a biocompatible augmentation material in rhinoplasty in the future.

A simple rocker-induced mechanical stimulus upregulates mineralization by human osteoprogenitor cells in fibrous scaffolds

Biodegradable electrospun polycaprolactone scaffolds can be used to support bone-forming cells and could fill a thin bony defect, such as in cleft palate. Oscillatory fluid flow has been shown to stimulate bone production in human progenitor cells in monolayer culture. The aim of this study was to examine whether bone matrix production by primary human mesenchymal stem cells from bone marrow or jaw periosteal tissue could be stimulated using oscillatory fluid flow supplied by a standard see-saw rocker. This was investigated for cells in two-dimensional culture and within electrospun polycaprolactone scaffolds. From day 4 of culture onwards, samples were rocked at 45 cycles/min for 1 h/day, 5 days/week (rocking group). Cell viability, calcium deposition, collagen production, alkaline phosphatase activity and vascular endothelial growth factor secretion were evaluated to assess the ability of the cells to undergo bone differentiation and induce vascularisation. Both cell types produced more mineralized tissue when subjected to rocking and supplemented with dexamethasone. Mesenchymal progenitors and primary human mesenchymal stem cells from bone marrow in three-dimensional scaffolds upregulated mineral deposition after rocking culture as assessed by micro-computed tomography and alizarin red staining. Interestingly, vascular endothelial growth factor secretion, which has previously been shown to be mechanically sensitive, was not altered by rocking in this system and was inhibited by dexamethasone. Rocker culture may be a cost effective, simple pretreatment for bone tissue engineering for small defects such as cleft palate.

Characterization of single cell derived cultures of periosteal progenitor cells to ensure the cell quality for clinical application

For clinical applications of cells and tissue engineering products it is of importance to characterize the quality of the used cells in detail. Progenitor cells from the periosteum are already routinely applied in the clinics for the regeneration of the maxillary bone. Periosteal cells have, in addition to their potential to differentiate into bone, the ability to develop into cartilage and fat. However, the question arises whether all cells isolated from periosteal biopsies are able to differentiate into all three tissue types, or whether there are subpopulations. For an efficient and approved application in bone or cartilage regeneration the clarification of this question is of interest. Therefore, 83 different clonal cultures of freshly isolated human periosteal cells derived from mastoid periosteum biopsies of 4 donors were generated and growth rates calculated. Differentiation capacities of 51 clonal cultures towards the osteogenic, the chondrogenic, and the adipogenic lineage were investigated. Histological and immunochemical stainings showed that 100% of the clonal cultures differentiated towards the osteogenic lineage, while 94.1% demonstrated chondrogenesis, and 52.9% could be stimulated to adipogenesis. For osteogenesis real-time polymerase chain reaction (PCR) of BGLAP and RUNX2 and for adipogenesis of FABP4 and PPARG confirmed the results. Overall, 49% of the cells exhibited a tripotent potential, 45.1% showed a bipotent potential (without adipogenic differentiation), 3.9% bipotent (without chondrogenic differentiation), and 2% possessed a unipotent osteogenic potential. In FACS analyses, no differences in the marker profile of undifferentiated clonal cultures with bi- and tripotent differentiation capacity were found. Genome-wide microarray analysis revealed 52 differentially expressed genes for clonal subpopulations with or without chondrogenic differentiation capacity, among them DCN, NEDD9, TGFBR3, and TSLP. For clinical applications of periosteal cells in bone regeneration all cells were inducible. For a chondrogenic application a fraction of 6% of the mixed population could not be induced.

Maxillary sinus lift surgery-with or without graft material? A systematic review

The purpose of this systematic review was to perform a comparative analysis of the use or not of graft material in maxillary sinus lift surgery. Relevant studies published in the last 10 years were identified through a search of the PubMed/MEDLINE, ScienceDirect, and Cochrane Library databases and were assessed against the study inclusion and exclusion criteria. The initial search resulted in 1037 articles. After applying the inclusion and exclusion criteria, 16 articles remained. Four hundred and thirty-six patients were followed up over a postoperative period ranging from 6 months to 11 years. In total, 868 implants were installed in 397 maxillary sinuses. The implant survival rate was 96.00% for surgeries performed without graft material and 99.60% for those in which biomaterial was used, within a follow-up period of 48 to 60 months. In conclusion, maxillary sinus lift surgery, with or without graft material, is a safe procedure with a low complication rate and predictable results.

Production and Characterization of a Novel, Electrospun, Tri-Layer Polycaprolactone Membrane for the Segregated Co-Culture of Bone and Soft Tissue

Composite tissue-engineered constructs combining bone and soft tissue have applications in regenerative medicine, particularly dentistry. This study generated a tri-layer, electrospun, poly-ε-caprolactone membrane, with two microfiber layers separated by a layer of nanofibers, for the spatially segregated culture of mesenchymal progenitor cells (MPCs) and fibroblasts. The two cell types were seeded on either side, and cell proliferation and spatial organization were investigated over several weeks. Calcium deposition by MPCs was detected using xylenol orange (XO) and the separation between fibroblasts and the calcified matrix was visualized by confocal laser scanning microscopy. SEM confirmed that the scaffold consisted of two layers of micron-diameter fibers with a thin layer of nano-diameter fibers in-between. Complete separation of cell types was maintained and calcified matrix was observed on only one side of the membrane. This novel tri-layer membrane is capable of supporting the formation of a bilayer of calcified and non-calcified connective tissue.

Axially vascularised mandibular constructs: Is it time for a clinical trial?

Applying regenerative therapies in the field of cranio-maxillofacial reconstruction has now become a daily practice. However, regeneration of challenging or irradiated bone defects following head and neck cancer is still far beyond clinical application. As the key factor for sound regeneration is the development of an adequate vascular supply for the construct, the current modalities using extrinsic vascularization are incapable of regenerating such complex defects. Our group has recently introduced the intrinsic axial vascularization technique to regenerate mandibular defects using the arteriovenous loop (AVL). The technique has shown promising results in terms of efficient vascularization and bone regeneration at the preclinical level. In this article, we have conducted a narrative literature review about using the AVL to vascularize tissue-engineering constructs at the preclinical level. We have also conducted a systematic literature review about applying the technique of axial vascularization in the field of craniofacial regeneration. The versatility of the technique and the possible challenges are discussed, and a suggested protocol for the first clinical trial applying the AVL technique for mandibular reconstruction is also presented.

Mesenchymal stem cells in maxillary sinus augmentation: A systematic review with meta-analysis

AIM: To investigate the effectiveness of mesenchymal stem cells (MSCs) in maxillary sinus augmentation (MSA), with various scaffold materials.

METHODS: MEDLINE, EMBASE and SCOPUS were searched using keywords such as sinus graft, MSA, maxillary sinus lift, sinus floor elevation, MSC and cell-based, in different combinations. The searches included full text articles written in English, published over a 10-year period (2004-2014). Inclusion criteria were clinical/radiographic and histologic/ histomorphometric studies in humans and animals, on the use of MSCs in MSA. Meta-analysis was performed only for experimental studies (randomized controlled trials and controlled trials) involving MSA, with an outcome measurement of histologic evaluation with histomorphometric analysis reported. Mean and standard deviation values of newly formed bone from each study were used, and weighted mean values were assessed to account for the difference in the number of subjects among the different studies. To compare the results between the test and the control groups, the differences of regenerated bone in mean and 95% confidence intervals were calculated.

RESULTS: Thirty-nine studies (18 animal studies and 21 human studies) published over a 10-year period (between 2004 and 2014) were considered to be eligible for inclusion in the present literature review. These studies demonstrated considerable variation with respect to study type, study design, follow-up, and results. Meta-analysis was performed on 9 studies (7 animal studies and 2 human studies). The weighted mean difference estimate from a random-effect model was 9.5% (95%CI: 3.6%-15.4%), suggesting a positive effect of stem cells on bone regeneration. Heterogeneity was measured by the I² index. The formal test confirmed the presence of substantial heterogeneity (I² = 83%, P < 0.0001). In attempt to explain the substantial heterogeneity observed, we considered a meta-regression model with publication year, support type (animal vs humans) and follow-up length (8 or 12 wk) as covariates. After adding publication year, support type and follow-up length to the meta-regression model, heterogeneity was no longer significant (I² = 33%, P = 0.25).

CONCLUSION: Several studies have demonstrated the potential for cell-based approaches in MSA; further clinical trials are needed to confirm these results.

Cultured chondrocyte and porcine cartilage-derived substance (PCS) construct as a possible dorsal augmentation material in rhinoplasty: A preliminary animal study

As there is no single ideal material for dorsal augmentation in rhinoplasty, there has been a continuing need for the development of improved materials. Therefore, we aimed to evaluate the outcome of using a novel tissue-engineered construct composed of autologous chondrocytes cultured with a porcine cartilage-derived substance (PCS) scaffold as an augmentation material in rhinoplasty. A scaffold derived from decellularized and powdered porcine articular cartilage was prepared. The rabbit articular cartilage was used as the source of homologous chondrocytes, which were expanded and cultured with the PCS scaffold for 7 weeks. The chondrocyte-PCS constructs were then surgically implanted on the nasal dorsum of six rabbits. Four and eight weeks after implantation, the gross morphology, radiologic images, and histologic features of the site of implant were analyzed. The rabbits showed no signs of postoperative inflammation and infection. The degree of dorsal augmentation was maintained during the 8-week postoperative observation period. Postoperative histologic examinations showed chondrocyte proliferation without an inflammatory response. However, neo-cartilage formation from the constructs was not confirmed. The biocompatibility and structural features of tissue-engineered chondrocyte-PCS constructs indicate their potential as candidate dorsal augmentation material for use in rhinoplasty.

Cellular behavior as a dynamic field for exploring bone bioengineering: a closer look at cell-biomaterial interface

Bone is a highly dynamic and specialized tissue, capable of regenerating itself spontaneously when afflicted by minor injuries. Nevertheless, when major lesions occur, it becomes necessary to use biomaterials, which are not only able to endure the cellular proliferation and migration, but also to substitute the original tissue or integrate itself to it. With the life expectancy growth, regenerative medicine has been gaining constant attention in the reconstructive field of dentistry and orthopedy. Focusing on broadening the therapeutic possibilities for the regeneration of injured organs, the development of biomaterials allied with the applicability of gene therapy and bone bioengineering has been receiving vast attention over the recent years. The progress of cellular and molecular biology techniques gave way to new-guided therapy possibilities. Supported by multidisciplinary activities, tissue engineering combines the interaction of physicists, chemists, biologists, engineers, biotechnologist, dentists and physicians with common goals: the search for materials that could promote and lead cell activity. A well-oriented combining of scaffolds, promoting factors, cells, together with gene therapy advances may open new avenues to bone healing in the near future. In this review, our target was to write a report bringing overall concepts on tissue bioengineering, with a special attention to decisive biological parameters for the development of biomaterials, as well as to discuss known intracellular signal transduction as a new manner to be explored within this field, aiming to predict in vitro the quality of the host cell/material and thus contributing with the development of regenerative medicine.

Autologous Ilium Grafts: Long-Term Results on Immediate or Staged Functional Rehabilitation of Mandibular Segmental Defects Using Dental Implants after Tumor Resection

BACKGROUND

It is a challenge for clinicians to restore oral function in patients with segmental defects of the mandible because of tumor extirpation. Dental implant therapy following vascularized autologous ilium grafts is an effective method to restore oral function in patients with mandibular segmental defects.

PURPOSE

The aim of this retrospective study was to investigate the long-term clinical outcomes of ilium grafts combined with immediate or staged mandibular dental implant therapy to restore craniofacial defects resulting from tumor resection.

MATERIALS AND METHODS

Over a 5-year period (2000-2004), 32 patients who underwent mandibular segmental resection for tumors were treated with vascularized ilium grafts to augment bone volume. Seventeen patients received phase I therapy (immediate placement of implants), and 15 patients underwent phase II therapy (delayed placement of implants). A total of 110 dental implants were placed in these patients for mandibular restoration of the defective areas. Information regarding implant success and survival rates, marginal bone loss, soft tissue inflammation, complications of prosthesis, and patient satisfaction for the 8 to 12 years following oral reconstruction was obtained from patient records.

RESULTS

Although there was mild evidence of bone graft resorption, the vascularized autogenous ilium bone grafts were successful in all patients. The cumulative patient survival and success rate of the implants were 96.4% and 91.8%, respectively. The mean peri-implant bone resorption ranged from 1.0 to 1.2 mm over the 8- to 12-year follow-up period. The annual mean number of complications/repairs was from 0.11 to 0.07 per patient during the 8- to 12-year follow-up. Over 80% of the patients were fully satisfied with their restoration of oral function.

CONCLUSIONS

This study demonstrates that reconstruction of mandibular segmental defects because of resection of mandibular tumors using dental implants therapy combined with vascularized autogenous ilium grafts is an effective method to restore oral function.

Make no bones about it: cells could soon be reprogrammed to grow replacement bones?

Recent developments in nuclear reprogramming allow the generation of patient-matched stem cells with broad potential for applications in cell therapies, disease modeling and drug discovery. An increasing body of work is reporting the derivation of lineage-specific progenitors from human-induced pluripotent stem cells (hiPSCs), which could in the near future be used to engineer personalized tissue substitutes, including those for reconstructive therapies of bone. Although the potential clinical impact of such technology is not arguable, significant challenges remain to be addressed before hiPSC-derived progenitors can be employed to engineer bone substitutes of clinical relevance. The most important challenge is indeed the construction of personalized multicellular bone substitutes for the treatment of complex skeletal defects that integrate fast, are immune tolerated and display biofunctionality and long-term safety. As recent studies suggest, the merging of iPSC technology with advanced biomaterials and bioreactor technologies offers a way to generate bone substitutes in a controllable, automated manner with potential to meet the needs for scale-up and requirements for translation into clinical practice. It is only via the use of state-of-the-art cell culture technologies, process automation under GMP-compliant conditions, application of appropriate engineering strategies and compliance with regulatory policies that personalized lab-made bone grafts can start being used to treat human patients.

Clinical applications of cell-based approaches in alveolar bone augmentation: a systematic review

BACKGROUND

Cell-based approaches, utilizing adult mesenchymal stem cells (MSCs), are reported to overcome the limitations of conventional bone augmentation procedures.

PURPOSE

The study aims to systematically review the available evidence on the characteristics and clinical effectiveness of cell-based ridge augmentation, socket preservation, and sinus-floor augmentation, compared to current evidence-based methods in human adult patients.

MATERIALS AND METHODS

MEDLINE, EMBASE, and CENTRAL databases were searched for related literature. Both observational and experimental studies reporting outcomes of "tissue engineered" or "cell-based" augmentation in ≥5 adult patients alone, or in comparison with non-cell-based (conventional) augmentation methods, were eligible for inclusion. Primary outcome was histomorphometric analysis of new bone formation. Effectiveness of cell-based augmentation was evaluated based on outcomes of controlled studies.

RESULTS

Twenty-seven eligible studies were identified. Of these, 15 included a control group (8 randomized controlled trials [RCTs]), and were judged to be at a moderate-to-high risk of bias. Most studies reported the combined use of cultured autologous MSCs with an osteoconductive bone substitute (BS) scaffold. Iliac bone marrow and mandibular periosteum were frequently reported sources of MSCs. In vitro culture of MSCs took between 12 days and 1.5 months. A range of autogenous, allogeneic, xenogeneic, and alloplastic scaffolds was identified. Bovine bone mineral scaffold was frequently reported with favorable outcomes, while polylactic-polyglycolic acid copolymer (PLGA) scaffold resulted in graft failure in three studies. The combination of MSCs and BS resulted in outcomes similar to autogenous bone (AB) and BS. Three RCTs and one controlled trial reported significantly greater bone formation in cell-based than conventionally grafted sites after 3 to 8 months.

CONCLUSIONS

Based on limited controlled evidence at a moderate-to-high risk of bias, cell-based approaches are comparable, if not superior, to current evidence-based bone grafting methods, with a significant advantage of avoiding AB harvesting. Future clinical trials should additionally evaluate patient-based outcomes and the time-/cost-effectiveness of these approaches.

Modeling vascularized bone regeneration within a porous biodegradable CaP scaffold loaded with growth factors

Osteogenetic microenvironment is a complex constitution in which extracellular matrix (ECM) molecules, stem cells and growth factors each interact to direct the coordinate regulation of bone tissue development. Importantly, angiogenesis improvement and revascularization are critical for osteogenesis during bone tissue regeneration processes. In this study, we developed a three-dimensional (3D) multi-scale system model to study cell response to growth factors released from a 3D biodegradable porous calcium phosphate (CaP) scaffold. Our model reconstructed the 3D bone regeneration system and examined the effects of pore size and porosity on bone formation and angiogenesis. The results suggested that scaffold porosity played a more dominant role in affecting bone formation and angiogenesis compared with pore size, while the pore size could be controlled to tailor the growth factor release rate and release fraction. Furthermore, a combination of gradient VEGF with BMP2 and Wnt released from the multi-layer scaffold promoted angiogenesis and bone formation more readily than single growth factors. These results demonstrated that the developed model can be potentially applied to predict vascularized bone regeneration with specific scaffold and growth factors.

Axially vascularized bone substitutes: a systematic review of literature and presentation of a novel model

INTRODUCTION

The creation of axially vascularized bone substitutes (AVBS) has been successfully demonstrated in several animal models. One prototypical indication is bone replacement in patients with previously irradiated defect sites, such as in the mandibular region. The downside of current clinical practice, when free fibular or scapular grafts are used, is the creation of significant donor site morbidity.

METHODS

Based on our previous experiments, we extended the creation of an arterio-venous loop to generate vascularized bone substitutes to a new defect model in the goat mandibula. In this report, we review the literature regarding different models for axially vascularized bone substitutes and present a novel model demonstrating the feasibility of combining this model with synthetic porous scaffold materials and biological tissue adhesives to grow cells and tissue.

RESULTS

We were able to show the principal possibility to generate axially vascularized bony substitutes in vivo in goat mandibular defects harnessing the regenerative capacity of the living organism and completely avoiding donor site morbidity.

CONCLUSION

From our findings, we conclude that this novel model may well offer new perspectives for orthopedic and traumatic bone defects that might benefit from the reduction of donor site morbidity.

Adhesive and mechanical regulation of mesenchymal stem cell differentiation in human bone marrow and periosteum-derived progenitor cells

It has previously been demonstrated that cell shape can influence commitment of human bone marrow-derived mesenchymal stem cells (hBMCs) to adipogenic, osteogenic, chondrogenic, and other lineages. Human periosteum-derived cells (hPDCs) exhibit multipotency similar to hBMCs, but hPDCs may offer enhanced potential for osteogenesis and chondrogenesis given their apparent endogenous role in bone and cartilage repair in vivo. Here, we examined whether hPDC differentiation is regulated by adhesive and mechanical cues comparable to that reported for hBMC differentiation. When cultured in the appropriate induction media, hPDCs at high cell seeding density demonstrated enhanced levels of adipogenic or chondrogenic markers as compared with hPDCs at low cell seeding density. Cell seeding density correlated inversely with projected area of cell spreading, and directly limiting cell spreading with micropatterned substrates promoted adipogenesis or chondrogenesis while substrates promoting cell spreading supported osteogenesis. Interestingly, cell seeding density influenced differentiation through both changes in cell shape and non-shape-mediated effects: density-dependent adipogenesis and chondrogenesis were regulated primarily by cell shape whereas non-shape effects strongly influenced osteogenic potential. Inhibition of cytoskeletal contractility by adding the Rho kinase inhibitor Y27632 further enhanced adipogenic differentiation and discouraged osteogenic differentiation of hPDCs. Together, our results suggest that multipotent lineage decisions of hPDCs are impacted by cell adhesive and mechanical cues, though to different extents than hBMCs. Thus, future studies of hPDCs and other primary stem cell populations with clinical potential should consider varying biophysical metrics for more thorough optimization of stem cell differentiation.