Cell-based therapy by implanted human bone marrow-derived mononuclear cells improved bone healing of large bone defects in rats

Effect of bone marrow aspiration concentrate and platelet-rich plasma combination in anterior cruciate ligament reconstruction: a randomized, prospective, double-blinded study

BACKGROUND

The effect of bone marrow aspirate concentrate (BMAC) and platelet-rich plasma (PRP) combination in enhancing graft maturation and tendon-bone tunnel interfacial healing after anterior cruciate ligament (ACL) reconstruction remains unclear. We hypothesised that BMAC and PRP combination could lead to better clinical results and better graft maturation/interface healing than PRP alone or conventional ACL reconstruction without any other biologic augmentation.

METHODS

In this randomised double-blind prospective study, patients undergoing ACL reconstruction surgery were randomly assigned into three groups: (1) control group (without any biologic augmentation), (2) PRP treatment group, and (3) combined BMAC and PRP (BMAC + PRP) group. Moreover, they were evaluated using the clinical functional score, laxity examination, and magnetic resonance imaging (MRI) analysis.

RESULTS

No significant difference was observed in the improvement of functional scores among groups. However, laxity improvement at 24 weeks showed a significant difference with the BMAC + PRP group having the lowest laxity. MRI analysis showed no significant change in whole graft maturation among groups. In particular, the BMAC + PRP group showed delayed signal peak and higher graft signal at 24 weeks compared with the other two groups; however, the difference was not significant. With regard to tendon-bone interfacial healing, the BMAC + PRP group showed significantly wider tendon-bone interface in the femoral bone tunnel at 24 weeks compared with the other two groups. Moreover, the BMAC + PRP group showed significantly higher peri-tunnel edema signal in the femoral bone tunnel at 12 weeks compared with the other two groups.

CONCLUSION

PRP alone and BMAC and PRP combination showed limited enhancing effect in clinical function, graft maturation and tendon-bone interfacial healing compared with control (no additional treatment). When BMAC is used in ACL reconstruction, the possibility of greater inflammation in the early stage to graft maturation and bone tunnel healing should be considered.

Pretreatment of Mesenchymal Stem Cells with Electrical Stimulation as a Strategy to Improve Bone Tissue Engineering Outcomes

Electrical stimulation (EStim), whether used alone or in combination with bone tissue engineering (BTE) approaches, has been shown to promote bone healing. In our previous in vitro studies, mesenchymal stem cells (MSCs) were exposed to EStim and a sustained, long-lasting increase in osteogenic activity was observed. Based on these findings, we hypothesized that pretreating MSC with EStim, in 2D or 3D cultures, before using them to treat large bone defects would improve BTE treatments. Critical size femur defects were created in 120 Sprague-Dawley rats and treated with scaffold granules seeded with MSCs that were pre-exposed or not (control group) to EStim 1 h/day for 7 days in 2D (MSCs alone) or 3D culture (MSCs + scaffolds). Bone healing was assessed at 1, 4, and 8 weeks post-surgery. In all groups, the percentage of new bone increased, while fibrous tissue and CD68+ cell count decreased over time. However, these and other healing features, like mineral density, bending stiffness, the amount of new bone and cartilage, and the gene expression of osteogenic markers, did not significantly differ between groups. Based on these findings, it appears that the bone healing environment could counteract the long-term, pro-osteogenic effects of EStim seen in our in vitro studies. Thus, EStim seems to be more effective when administered directly and continuously at the defect site during bone healing, as indicated by our previous studies.

One Stage Masquelets Technique: Evaluation of Different Forms of Membrane Filling with and without Bone Marrow Mononuclear Cells (BMC) in Large Femoral Bone Defects in Rats

The classic two-stage masquelet technique is an effective procedure for the treatment of large bone defects. Our group recently showed that one surgery could be saved by using a decellularized dermis membrane (DCD, Epiflex, DIZG). In addition, studies with bone substitute materials for defect filling show that it also appears possible to dispense with the removal of syngeneic cancellous bone (SCB), which is fraught with complications. The focus of this work was to clarify whether the SCB can be replaced by the granular demineralized bone matrix (g-DBM) or fibrous demineralized bone matrix (f-DBM) demineralized bone matrix and whether the colonization of the DCD and/or the DBM defect filling with bone marrow mononuclear cells (BMC) can lead to improved bone healing. In 100 Sprague Dawley rats, a critical femoral bone defect 5 mm in length was stabilized with a plate and then encased in DCD. Subsequently, the defect was filled with SCB (control), g-DBM, or f-DBM, with or without BMC. After 8 weeks, the femurs were harvested and subjected to histological, radiological, and biomechanical analysis. The analyses showed the incipient bony bridging of the defect zone in both groups for g-DBM and f-DBM. Stability and bone formation were not affected compared to the control group. The addition of BMCs showed no further improvement in bone healing. In conclusion, DBM offers a new perspective on defect filling; however, the addition of BMC did not lead to better results.

Single-cell spatiotemporal analysis reveals cell fates and functions of transplanted mesenchymal stromal cells during bone repair

Mesenchymal stromal cells (MSCs) transplantation could enhance bone repair. However, the cell fate of transplanted MSCs, in terms of their local distribution and spatial associations with other types of cells were poorly understood. Here, we developed a single-cell 3D spatial correlation (sc3DSC) method to track transplanted MSCs based on deep tissue microscopy of fluorescent nanoparticles (fNPs) and immunofluorescence of key proteins. Locally delivered fNP-labeled MSCs enhanced tibial defect repair, increased the number of stem cells and vascular maturity in mice. fNP-MSCs persisted in the defect throughout repair. But only a small portion of transplanted cells underwent osteogenic differentiation (OSX+); a significant portion has maintained their expression of mesenchymal stem cell and skeletal stem cell markers (SCA-1 and PRRX1). Our results contribute to the optimization of MSC-based therapies. The sc3DSC method may be useful in studying cell-based therapies for the regeneration of other tissue types or disease models.

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Transplanted marrow stromal cells associated with vessels during bone defect repair

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Small proportion of transplanted cells differentiated into osteogenic cells

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A proportion of transplanted cells maintained expressions of stem cell markers

The Induced Membrane Technique—The Filling Matters: Evaluation of Different Forms of Membrane Filling with and without Bone Marrow Mononuclear Cells (BMC) in Large Femoral Bone Defects in Rats

The Masquelet technique is used to treat large bone defects; it is a two-stage procedure based on an induced membrane. To improve the induced membrane process, demineralized bone matrix in granular (GDBM) and fibrous form (f-DBM) was tested with and without bone marrow mononuclear cells (BMC) as filling of the membrane against the gold standard filling with syngeneic cancellous bone (SCB). A total of 65 male Sprague–Dawley rats obtained a 5 mm femoral defect. These defects were treated with the induced membrane technique and filled with SCB, GDBM, or f-DBM, with or without BMC. After a healing period of eight weeks, the femurs were harvested and submitted for histological, radiological, and biomechanical analyses. The fracture load in the defect zone was lower compared to SCB in all groups. However, histological analysis showed comparable new bone formation, bone mineral density, and cartilage proportions and vascularization. The results suggest that f-DBM in combination with BMC and the induced membrane technique cannot reproduce the very good results of this material in large, non-membrane coated bone defects, nevertheless it supports the maturation of new bone tissue locally. It can be concluded that BMC should be applied in lower doses and inflammatory cells should be removed from the cell preparation before implantation.

Fibrous Demineralized Bone Matrix (DBM) Improves Bone Marrow Mononuclear Cell (BMC)-Supported Bone Healing in Large Femoral Bone Defects in Rats

Regeneration of large bone defects is a major objective in trauma surgery. Bone marrow mononuclear cell (BMC)-supported bone healing was shown to be efficient after immobilization on a scaffold. We hypothesized that fibrous demineralized bone matrix (DBM) in various forms with BMCs is superior to granular DBM. A total of 65 male SD rats were assigned to five treatment groups: syngenic cancellous bone (SCB), fibrous demineralized bone matrix (f-DBM), fibrous demineralized bone matrix densely packed (f-DBM 120%), DBM granules (GDBM) and DBM granules 5% calcium phosphate (GDBM5%Ca2+). BMCs from donor rats were combined with different scaffolds and placed into 5 mm femoral bone defects. After 8 weeks, bone mineral density (BMD), biomechanical stability and histology were assessed. Similar biomechanical properties of f-DBM and SCB defects were observed. Similar bone and cartilage formation was found in all groups, but a significantly bigger residual defect size was found in GDBM. High bone healing scores were found in f-DBM (25) and SCB (25). The application of DBM in fiber form combined with the application of BMCs shows promising results comparable to the gold standard, syngenic cancellous bone. Denser packing of fibers or higher amount of calcium phosphate has no positive effect.

Effect of Freshly Isolated Bone Marrow Mononuclear Cells and Cultured Bone Marrow Stromal Cells in Graft Cell Repopulation and Tendon-Bone Healing after Allograft Anterior Cruciate Ligament Reconstruction

Graft cell repopulation and tendon-bone tunnel healing are important after allograft anterior cruciate ligament reconstruction (ACLR). Freshly isolated bone marrow mononuclear cells (BMMNCs) have the advantage of short isolation time during surgery and may enhance tissue regeneration. Thus, we hypothesized that the effect of intra-articular BMMNCs in post-allograft ACLR treatment is comparable to that of cultured bone marrow stromal cells (BMSCs). A rabbit model of hamstring allograft ACLR was used in this study. Animals were randomly assigned to the BMMNC, BMSC, and control groups. Fresh BMMNCs isolated from the iliac crest during surgery and cultured BMSCs at passage four were used in this study. A total of 1 × 10⁷ BMMNCs or BMSCs in 100 µL phosphate-buffered saline were injected into the knee joint immediately after ACLR. The control group was not injected with cells. At two and six weeks post operation, we assessed graft cell repopulation with histological and cell tracking staining (PKH26), and tendon-bone healing with histological micro-computed tomography and immunohistochemical analyses for collagen I and monocyte chemoattractant protein-1 (MCP1). At two weeks post operation, there was no significant difference in the total cell population within the allograft among the three groups. However, the control group showed significantly higher cell population within the allograft than that of BM cell groups at six weeks. Histological examination of proximal tibia revealed that the intra-articular delivered cells infiltrated into the tendon-bone interface. Compared to the control group, the BM cell groups showed broader gaps with interfacial fibrocartilage healing, similar collagen I level, and higher MCP1 expression in the early stage. Micro-CT did not reveal any significant difference among the three groups. BMMNCs and BMSCs had comparable effects on cell repopulation and interfacial allograft-bone healing. Intra-articular BM cells delivery had limited benefits on graft cell repopulation and caused higher inflammation than that in the control group in the early stage, with fibrocartilage formation in the tendon-bone interface after allograft ACLR.

Endothelial progenitor cells promote osteogenic differentiation in co-cultured with mesenchymal stem cells via the MAPK-dependent pathway

BACKGROUND

The role of bone tissue engineering is to regenerate tissue using biomaterials and stem cell-based approaches. Combination of two or more cell types is one of the strategies to promote bone formation. Endothelial progenitor cells (EPCs) may enhance the osteogenic properties of mesenchymal stem cells (MSCs) and promote bone healing; this study aimed to investigate the possible mechanisms of EPCs on promoting osteogenic differentiation of MSCs.

METHODS

MSCs and EPCs were isolated and co-cultured in Transwell chambers, the effects of EPCs on the regulation of MSC biological properties were investigated. Real-time PCR array, and western blotting were performed to explore possible signaling pathways involved in osteogenesis. The expression of osteogenesis markers and calcium nodule formation was quantified by qRT-PCR, western blotting, and Alizarin Red staining.

RESULTS

Results showed that MSCs exhibited greater alkaline phosphatase (ALP) activity and increased calcium mineral deposition significantly when co-cultured with EPCs. The mitogen-activated protein kinase (MAPK) signaling pathway was involved in this process. p38 gene expression and p38 protein phosphorylation levels showed significant upregulation in co-cultured MSCs. Silencing expression of p38 in co-cultured MSCs reduced osteogenic gene expression, protein synthesis, ALP activity, and calcium nodule formation.

CONCLUSIONS

These data suggest paracrine signaling from EPCs influences the biological function and promotes MSCs osteogenic differentiation. Activation of the p38MAPK pathway may be the key to enhancing MSCs osteogenic differentiation via indirect interactions with EPCs.

Impact of scaffold granule size use in Masquelet technique on periosteal reaction: a study in rat femur critical size bone defect model

Purpose

The Masquelet technique for the treatment of large bone defects is a two-stage procedure based on an induced membrane. Compared to mature periosteum, the induced membrane differs significantly. However, both play a crucial role in bone regeneration. As part of a histological and radiological post-evaluation of an earlier project, we analyzed the influence of the granule size of the bone void filler Herafill^® on development of periosteum regrowth in a critical size defect.

Methods

We compared three different sizes of Herafill^® granules (Heraeus Medical GmbH, Wehrheim) in vivo in a rat femoral critical size defect (10 mm) treated with the induced membrane technique. After 8 weeks healing time, femurs were harvested and taken for histological and radiological analysis.

Results

A significantly increased regrowth of periosteum into the defect was found when small granules were used. Large granules showed significantly increased occurrence of bone capping. Small granules lead to significant increase in callus formation in the vicinity to the membrane.

Conclusion

The size of Herafill^® granules has significant impact on the development of periosteal-like structures around the defect using Masquelet’s induced membrane technique. Small granules show significantly increased regrowth of periosteum and improved bone formation adjacent to the induced membrane.

Modifying MSC Phenotype to Facilitate Bone Healing: Biological Approaches

Healing of fractures and bone defects normally follows an orderly series of events including formation of a hematoma and an initial stage of inflammation, development of soft callus, formation of hard callus, and finally the stage of bone remodeling. In cases of severe musculoskeletal injury due to trauma, infection, irradiation and other adverse stimuli, deficient healing may lead to delayed or non-union; this results in a residual bone defect with instability, pain and loss of function. Modern methods of mechanical stabilization and autologous bone grafting are often successful in achieving fracture union and healing of bone defects; however, in some cases, this treatment is unsuccessful because of inadequate biological factors. Specifically, the systemic and local microenvironment may not be conducive to bone healing because of a loss of the progenitor cell population for bone and vascular lineage cells. Autologous bone grafting can provide the necessary scaffold, progenitor and differentiated lineage cells, and biological cues for bone reconstruction, however, autologous bone graft may be limited in quantity or quality. These unfavorable circumstances are magnified in systemic conditions with chronic inflammation, including obesity, diabetes, chronic renal disease, aging and others. Recently, strategies have been devised to both mitigate the necessity for, and complications from, open procedures for harvesting of autologous bone by using minimally invasive aspiration techniques and concentration of iliac crest bone cells, followed by local injection into the defect site. More elaborate strategies (not yet approved by the U.S. Food and Drug Administration-FDA) include isolation and expansion of subpopulations of the harvested cells, preconditioning of these cells or inserting specific genes to modulate or facilitate bone healing. We review the literature pertinent to the subject of modifying autologous harvested cells including MSCs to facilitate bone healing. Although many of these techniques and technologies are still in the preclinical stage and not yet approved for use in humans by the FDA, novel approaches to accelerate bone healing by modifying cells has great potential to mitigate the physical, economic and social burden of non-healing fractures and bone defects.

Introduction of a New Surgical Method to Improve Bone Healing in a Large Bone Defect by Replacement of the Induced Membrane by a Human Decellularized Dermis Repopulated with Bone Marrow Mononuclear Cells in Rat

The Masquelet technique for the treatment of large bone defects is a two-stage procedure based on an induced membrane. We eliminate the first surgical step by using a decellularized dermal skin graft (Epiflex^®) populated with bone marrow mononuclear cells (BMC), as a replacement for the induced membrane. The aim of this study was to demonstrate the feasibility of this technology and provide evidence of equivalent bone healing in comparison to the induced membrane-technique. Therefore, 112 male Sprague–Dawley rats were allocated in six groups and received a 10 mm femoral defect. Defects were treated with either the induced membrane or decellularized dermis, with or without the addition of BMC. Defects were then filled with a scaffold (β-TCP), with or without BMC. After a healing time of eight weeks, femurs were taken for histological, radiological and biomechanical analysis. Defects treated with Epiflex^® showed increased mineralization and bone formation predominantly in the transplanted dermis surrounding the defect. No significant decrease of biomechanical properties was found. Vascularization of the defect could be enhanced by addition of BMC. Considering the dramatic reduction of a patient’s burden by the reduced surgical stress and shortened time of treatment, this technique could have a great impact on clinical practice.

Enhancement of bone marrow aspirate concentrate with local self-healing corticotomies

Bone marrow aspirate concentrate (BMAC) is a potentially useful biological product for bone regeneration. This study investigated whether BMAC can be enriched by local minor corticotomies. Five 4-month-old domestic pigs were used with each pig undergoing two minor corticotomies at one randomly-selected tibia. Two weeks after the operation, bone marrow was aspirated from both tibiae and processed into BMAC samples. The amount of mesenchymal stem cells (MSCs) and the concentration of several regenerative growth factors contained in BMAC, as well as the proliferative and osteogenic differentiation capacity of MSCs, were compared between the corticotomy and the control sides. Another four weeks later, healing of the corticotomies was evaluated by radiographic and histological methods. The results demonstrated that BMAC from the corticotomy side contained significantly more MSCs than the control side. MSCs from the corticotomy side also proliferated significantly faster and tended to have stronger osteogenic differentiation than those from the control side. In contrast, the protein concentration of TGF-β, BMP-2 and PDGF contained in BMAC was only minimally changed by the corticotomies. The corticotomies in all pigs healed uneventfully, showing complete obliteration of the corticotomy gaps on CT images. Comparison between the two sides showed that the corticotomy side had thicker and denser cortical bone and more abundant osteogenic cell differentiation than the control side. These findings suggest that the quantity and proliferative/osteogenic differentiation capacity of MSCs contained in local BMAC can be enhanced by minor corticotomies, and spontaneous healing of the corticotomy can be completed within 6 weeks of the operation.

Determination of the effective dose of bone marrow mononuclear cell therapy for bone healing in vivo

Introduction

Cell-based therapy by bone marrow mononuclear cells (BMC) in a large-sized bone defect has already shown improved vascularization and new bone formation. First clinical trials are already being conducted. BMC were isolated from bone marrow aspirate and given back to patients in combination with a scaffold within some hours. However, the optimal concentration of BMC has not yet been determined for bone healing. With this study, we want to determine the optimal dosage of the BMC in the bone defect to support bone healing.

Material and methods

Scaffolds with increasing BMC concentrations were inserted into a 5 mm femoral defect, cell concentrations of 2 × 10⁶ BMC/mL, 1 × 10⁷ BMC/mL and 2 × 10⁷ BMC/mL were used. Based on the initial cell number used to colonize the scaffolds, the groups are designated 1 × 10⁶, 5 × 10⁶ and 1 × 10⁷ group. Bone healing was assessed biomechanically, radiologically (µCT), and histologically after 8 weeks healing time.

Results

Improved bone healing parameters were noted in the 1 × 10⁶ and 5 × 10⁶ BMC groups. A significantly higher BMD was observed in the 1 × 10⁶ BMC group compared to the other groups. Histologically, a significantly increased bone growth in the defect area was observed in group 5 × 10⁶ BMC. This finding could be supported radiologically.

Conclusion

It was shown that the effective dose of BMC for bone defect healing ranges from 2 × 10⁶ BMC/mL to 1 × 10⁷ BMC/mL. This concentration range seems to be the therapeutic window for BMC-supported therapy of large bone defects. However, further studies are necessary to clarify the exact BMC-dose dependent mechanisms of bone defect healing and to determine the therapeutically effective range more precisely.

Fasudil enhanced differentiation of BMSCs in vivo and vitro, involvement of P38 signaling pathway

Bone mesenchymal stem cells (BMSCs) are a well-known donor graft source due to their potential for self-renewal and differentiation into multi-lineage cell types, including osteoblasts that are critical for fracture healing. Fasudil (FAS), a Rho kinase inhibitor, has been proven to induce the differentiation of bone marrow stem cells (BMSCs) into neuron-like cells. However, its role in the osteogenesis of BMSCs remain uncertain. Herein, we for the first time studied the effects of FAS on osteogenic differentiation in a mouse fracture model and further explored the involved mechanisms in mouse BMSCs. The results showed that FAS stimulated bone formation in the fracture mouse model. Additionally, at 30 μM, FAS significantly promotes alkaline phosphatase activity, mineralization, and the expression of osteogenic markers COL-1, RUNX2 and OCN in murine BMSCs. Blocking of P38 by SB202190 significantly reversed the effects of FAS, in vitro, suggesting that P38, but not ERK or JNK activation is required for FAS-induced osteogenesis. Collectively, our results indicate that FAS may be a promising agent for promoting fracture healing.

From two stages to one: acceleration of the induced membrane (Masquelet) technique using human acellular dermis for the treatment of non-infectious large bone defects

Introduction

The induced membrane technique for the treatment of large bone defects is a two-step procedure. In the first operation, a foreign body membrane is induced around a spacer, then, in the second step, several weeks or months later, the spacer is removed and the Membrane pocket is filled with autologous bone material. Induction of a functional biological membrane might be avoided by initially using a biological membrane. In this study, the effect of a human acellular dermis (hADM, Epiflex, DIZG gGmbH) was evaluated for the treatment of a large (5 mm), plate-stabilised femoral bone defect.

Material and Methods

In an established rat model, hADM was compared to the two-stage induced membrane technique and a bone defect without membrane cover. Syngeneous spongiosa from donor animals was used for defect filling in all groups. The group size in each case was n = 5, the induction time of the membrane was 3–4 weeks and the healing time after filling of the defect was 8 weeks.

Results

The ultimate loads were increased to levels comparable with native bone in both membrane groups (hADM: 63.2% ± 29.6% of the reference bone, p < 0.05 vs. no membrane, induced membrane: 52.1% ± 25.8% of the reference bone, p < 0.05 vs. no membrane) and were significantly higher than the control group without membrane (21.5%). The membrane groups were radiologically and histologically almost completely bridged by new bone formation, in contrast to the control Group where no closed osseous bridging could be observed.

Conclusion

The use of the human acellular dermis leads to equivalent healing results in comparison to the two-stage induced membrane technique. This could lead to a shortened therapy duration of large bone defects.

Role of Adult Tissue-Derived Pluripotent Stem Cells in Bone Regeneration

Background

Bone marrow-derived mononuclear cells (BM-MNC) consist of a heterogeneous mix of mesenchymal stem cells (MSC), hematopoietic progenitor cells (HPC), endothelial progenitor cells (EPC), monocytes, lymphocytes and pluripotent stem cells. Whereas the importance of MSC and EPC has been well documented in bone healing and regeneration studies, the role of pluripotent stem cells is still poorly understood. In the present study we evaluated if and how Very Small Embryonic Like cells (VSEL), isolated from rat BM-MNC, contribute to bone healing.

Methods

Large bone defects were made in the femurs of 38 Sprague Dawley female rats and treated with β-TCP scaffold granules seeded with male VSEL; BM-MNC, VSEL-depleted BM-MNC or scaffold alone, and bone healing was evaluated at 8 weeks post-surgery.

Results

Bone healing was significantly increased in defects treated with VSEL and BM-MNC, compared to defects treated with VSEL-depleted BM-MNC. Donor cells were detected in new bone tissue, in all the defects treated with cells, and in fibrous tissue only in defects treated with VSEL-depleted BM-MNC. The number of CD68+ cells was the highest in the VSEL-depleted group, whereas the number of TRAP positive cells was the lowest in this group.

Conclusions

Based on the results, we can conclude that VSEL play a role in BM-MNC induced bone formation. In our rat femur defect model, in defects treated with VSEL-depleted BM-MNC, osteoclastogenesis and bone formation were decreased, and foreign body reaction was increased.

Size matters: Effect of granule size of the bone graft substitute (Herafill®) on bone healing using Masquelet's induced membrane in a critical size defect model in the rat's femur

The Masquelet technique for the treatment of large bone defects is a two-stage procedure based on an induced membrane. The size of a scaffold is reported to be a critical factor for bone healing response. We therefore aimed to investigate the influence of the granule size of a bone graft substitute on bone marrow derived mononuclear cells (BMC) supported bone healing in combination with the induced membrane. We compared three different sizes of Herafill® granules (Heraeus Medical GmbH, Wehrheim) with or without BMC in vivo in a rat femoral critical size defect. A 10 mm defect was made in 126 rats and a membrane induced by a PMMA-spacer. After 3 weeks, the spacer was taken out and membrane filled with different granule sizes. After 8 weeks femurs were taken for radiological, biomechanical, histological, and immunohistochemical analysis. Further, whole blood of the rat was incubated with granules and expression of 29 peptide mediators was assessed. Smallest granules showed significantly improved bone healing compared to larger granules, which however did not lead to an increased biomechanical stability in the defect zone. Small granules lead to an increased accumulation of macrophages in situ which could be assigned to the inflammatory subtype M1 by majority. Increased release of chemotactic respectively proangiogenic active factors in vitro compared to syngenic bone and beta-TCP was observed. Granule size of the bone graft substitute Herafill® has significant impact on bone healing of a critical size defect in combination with Masquelet's technique in terms of bone formation and inflammatory potential.

Nonunions of the humerus - Treatment concepts and results of the last five years

PURPOSE

Fractures of the humerus account for 5%-8% of all fractures. Nonunion is found with an incidence of up to 15%, depending on the location of the fracture. In case of a manifest nonunion the surgeon faces a challenging problem and has to conceive a therapy based on the underlying pathology. The aim of this study was to describe our treatment concepts for this entity and present our results of the last five years.

METHODS

Twenty-six patients were treated for nonunion of the humerus between January 2013 and December 2017. Their charts were reviewed retrospectively and demographic data, pathology, surgical treatment and outcome were assessed.

RESULTS

The most frequent location for a nonunion was the humeral shaft, with the most common trauma mechanism being multiple falls. Most often atrophic nonunion (n = 14), followed by hypertrophic and infection-caused nonunion (each n = 4), were found. Our treatment concept could be applied in 19 patients, of which in 90% of those who were available for follow-up consolidation could be achieved.

CONCLUSION

Humeral nonunion is a heterogeneous entity that has to be analyzed precisely and be treated correspondingly. We therefore present a treatment concept based on the underlying pathology.

Effect of bone sialoprotein coating on progression of bone formation in a femoral defect model in rats

PURPOSE

In orthopedic and trauma surgery, calcium phosphate cement (CPC) scaffolds are widely used as substitute for autologous bone grafts. The purpose of this study was to evaluate bone formation in a femoral condyle defect model in rats after scaffold-coating with bioactive bone sialoprotein (BSP). Our hypothesis was that BSP-coating results in additional bone formation.

METHODS

In 20 Wistar rats, defects of 3.0 mm diameter were drilled into the lateral femoral condyles of both legs. BSP-coated scaffolds or uncoated control scaffolds were implanted into the defects. After 4 and 8 weeks, five rats of each group were euthanized, respectively. µCT scans and histological analyses were performed. The ratio of bone volume-total volume (BV/TV) was analyzed and histological sections were evaluated.

RESULTS

At week four, bone fraction reached 5.2 ± 1.7% in BSP-coated scaffolds and 4.5 ± 3.2% in the control (p = 0.06). While bone fraction of the BSP-group did not change much between week four and eight [week eight: 5.4 ± 3.8% (p = 0.53)], there was a tendency towards an increase in the control [week eight: 7.0 ± 2.2% (p = 0.08)]. No significant difference in bone fraction were observable between BSP-coated and uncoated scaffolds at week eight (p = 0.08).

CONCLUSIONS

A significant superiority of BSP-coated scaffolds over uncoated scaffolds could not be proven. However, BSP-coating showed a tendency towards improving bone ingrowth in the scaffolds 4 weeks after implantation. This effect was only short-lived: bone growth in the control scaffolds tended to outpace that of the BSP-group at week eight.

Recent Advances in Scaffold Design and Material for Vascularized Tissue-Engineered Bone Regeneration

Bone tissue is a highly vascularized tissue and concomitant development of the vascular system and mineralized matrix requires a synergistic interaction between osteogenesis and angioblasts. Several strategies have been applied to achieve vascularized tissue-engineered bone, including the addition of cytokines as well as pre-vascularization strategies and co-culture systems. However, the scaffold is another extremely important component to consider, and development of vascularized bone scaffolds remains one of the greatest challenges for engineering clinically relevant bone substitutes. Here, this review highlights the biomaterial selection, preparation of pre-vascularized scaffolds, composition modification of the scaffold, structural design, and the comprehensive use of the above synergistic modifications of scaffold materials for vascular scaffolds in bone tissue engineering. Moreover, a strategy is proposed for the design of future scaffold structures, in which promoting the regeneration of vascularized bone by regulating the microenvironment should be the main focus. This overview can help illuminate progress in this field and identify the most recently developed scaffolds that show the greatest potential for achieving clinically vascularized bone.

Osteogenic ability of rat bone marrow concentrate is at least as efficacious as mesenchymal stem cells in vitro

Cell therapy using bone marrow concentrate (BMC) or purified and expanded mesenchymal stem cells (MSCs) has been shown to have a promising osteogenic capacity. However, few studies have directly compared their relative osteogenic ability. The aim of this study was to compare the osteogenic ability of BMC isolated by density gradient centrifugation with bone marrow-derived MSCs in vitro using the cells of 3-month-old Sprague-Dawley rats. The isolated cells were seeded onto 24-well plates (1 × 10⁵  cells/well) and cultured in control growth media, osteogenic media with dexamethasone, or media without dexamethasone (which simulated the in vivo tissue environment). Alkaline phosphatase activity at week 2, osteocalcin using quantitative real-time polymerase chain reaction at week 4, and Alizarin red staining at week 4 were evaluated. In the osteogenic media with dexamethasone, BMC showed equivalent (osteocalcin) or even greater (Alizarin red staining) osteogenic ability compared to MSCs, suggesting that cross-talk among various cells in the BMC leads to greater osteogenesis. Furthermore, in the osteogenic media without dexamethasone, BMC showed equivalent (osteocalcin) or a trend for greater (Alizarin red staining) bone formation than MSCs alone. Our results suggest that BMC has at least comparable bone regeneration potential to MSCs. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2500-2506, 2019.

Histological Scoring Method to Assess Bone Healing in Critical Size Bone Defect Models

Large bone defects are a major problem in trauma and orthopedic surgery. Tissue engineering based treatments have emerged as promising alternatives to traditional bone grafting techniques. Critical size bone defect animal models have been developed and widely used to evaluate and compare therapeutic effectiveness in bone tissue engineering treatments. To measure healing in a given defect after treatment, histological assessment methods are commonly used. These histological methods are typically qualitative and only measure the amount of newly formed bone. In this study, we introduce a new histological scoring method that in addition to new bone formation also measures newly formed "cartilage," "fibrous tissue," and "remnant bone defect size." Using Kappa analysis and interclass correlation analysis, we verified the reliability of our new scoring method. These additional parameters make it possible to differentiate between the hard callus and soft callus phases of healing and, thus, derive more valuable information about the effect different tissue-engineering treatments have on the healing process.

Influence of concentration and preparation of platelet rich fibrin on human bone marrow mononuclear cells (in vitro)

Large bone defects have always been a big challenge. The use of bone marrow mononuclear cells (BMCs) combined with an osteoconductive scaffold has been proved a good alternative for the treatment of large bone defects. Another autologous source for tissue engineering is platelet rich fibrin (PRF). PRF is a blood concentrate system obtained through a one-step centrifugation. The generated 3D matrix of the PRF clot serves as a reservoir of growth factors. Those growth factors might support the regenerative response of BMC, and therefore the effect of PRF, centrifuged with either high medium (208 g) or low (60 g) relative centrifugation force (RCF) on BMCs was evaluated in vitro in the present study. The two PRF matrices obtained were initially characterized and compared to human serum. Significantly increased concentrations of insulin-like growth factor (IGF), soluble intercellular adhesion molecule-1 (sICAM1) and transforming growth factor (TGF)-β were found in PRF compared to human serum whereas VEGF concentration was not significantly altered. A dose-response study revealed no further activation of BMC's metabolic activity, if concentration of both PRF matrices exceeded 10% (v/v). Effect of both PRF preparations [10%] on BMC was analyzed after 2, 7, and 14 days in comparison to human serum [10%]. Metabolic activity of BMC increased significantly in all groups on day 14. Furthermore, gene expression of matrix metalloproteinases (MMP)-2, -7, and -9 was significantly stimulated in BMC cultivated with the respective PRF matrices compared to human serum. Apoptotic activity of BMC incubated with PRF was not altered compared to BMC cultivated with serum. In conclusion, PRF could be used as a growth factor delivery system of autologous or allogeneic source with the capability of stimulating cells such as BMC.

Influence of the induced membrane filled with syngeneic bone and regenerative cells on bone healing in a critical size defect model of the rat's femur

INTRODUCTION

The induced membrane technique for the treatment of large bone defects consists of a 2-stage procedure. In the first stage, a polymethylmethacrylate (PMMA) cement spacer is inserted into the bony defect of a rat's femur and over a period of 2-4 weeks a membrane forms that encapsulates the defect/spacer. In a second operation the membrane is opened, the PMMA spacer is removed and the resulting cavity is filled with autologous bone. Since little effort has been made to replace the need for autologous bone this study was performed to elucidate the influence of different stem cells and the membrane itself on bone healing in a critical size femur defect model in rats. Especially the question should be addressed whether the use of stem cells seeded on a β-TCP scaffold is equivalent to syngeneic bone as defect filling in combination with the induced membrane technique.

MATERIALS AND METHODS

A total of 96 male Sprague-Dawley (SD) rats received a 10 mm critical size defect of the femur, which was stabilized by a plate osteosynthesis and filled with PMMA cement. In a second step the spacer was extracted and the defects were filled with syngeneic bone, β-TCP with MSC + EPC or BM-MNC. In order to elucidate the influence of the induced membrane on bone defect healing the induced membrane was removed in half of the operated femurs. The defect area was analysed 8 weeks later for bone formation (osteocalcin staining), bone mineral density (BMD) and bone strength (3-point bending test).

RESULTS

New bone formation, bone mineral density and bone stiffness increased significantly, if the membrane was kept. The transplantation of biologically active material (syngeneic bone, stem cells on b-TCP) into the bone defect mostly led to a further increase of bone healing. Syngeneic bone had the greatest impact on bone healing however defects treated with stem cells were oftentimes comparable.

CONCLUSION

For the first time we demonstrated the effect of the induced membrane itself and different stem cells on critical size defect healing. This could be a promising approach to reduce the need for autologous bone transplantation with its' limited availability and donor site morbidity.

Autologous cell-based therapy for treatment of large bone defects: from bench to bedside

OBJECTIVES

Reconstruction of long segmental bone defects is demanding for patients and surgeons, and associated with long-term treatment periods and substantial complication rates in addition to high costs. While defects up to 4-5 cm length might be filled up with autologous bone graft, heterologous bone from cadavers, or artificial bone graft substitutes, current options to reconstruct bone defects greater than 5 cm consist of either vascularized free bone transfers, the Masquelet technique or the Ilizarov distraction osteogenesis. Alternatively, autologous cell transplantation is an encouraging treatment option for large bone defects as it eliminates problems such as limited autologous bone availability, allogenic bone immunogenicity, and donor-site morbidity, and might be used for stabilizing loose alloplastic implants.

METHODS

The authors show different cell therapies without expansion in culture, with ex vivo expansion and cell therapy in local bone defects, bone healing and osteonecrosis. Different kinds of cells and scaffolds investigated in our group as well as in vivo transfer studies and BMC used in clinical phase I and IIa clinical trials of our group are shown.

RESULTS

Our research history demonstrated the great potential of various stem cell species to support bone defect healing. It was clearly shown that the combination of different cell types is superior to approaches using single cell types. We further demonstrate that it is feasible to translate preclinically developed protocols from in vitro to in vivo experiments and follow positive convincing results into a clinical setting to use autologous stem cells to support bone healing.

Development of a centrally vascularized tissue engineering bone graft with the unique core-shell composite structure for large femoral bone defect treatment

Great effort has been spent to promote the vascularization of tissue engineering bone grafts (TEBG) for improved therapeutic outcome. However, the thorough vascularization especially in the central region still remained as a major challenge for the clinical translation of TEBG. Here, we developed a new strategy to construct a centrally vascularized TEBG (CV-TEBG) with unique core-shell composite structure, which is consisted of an angiogenic core and an osteogenic shell. The in vivo evaluation in rabbit critical sized femoral defect was conducted to meticulously compare CV-TEBG to other TEBG designs (TEBG with osteogenic shell alone, or angiogenic core alone or angiogenic core+shell). Microfil-enhanced micro-CT analysis has been shown that CV-TEBG could outperform TEBG with pure osteogenic or angiogenic component for neo-vascularization. CV-TEBG achieved a much higher and more homogenous vascularization throughout the whole scaffold (1.52-38.91 folds, p < 0.01), and generated a unique burrito-like vascular network structure to perfuse both the central and peripheral regions of TEBG, indicating a potential synergistic effect between the osteogenic shell and angiogenic core in CV-TEBG to enhance neo-vascularization. Moreover, CV-TEBG has generated more new bone tissue than other groups (1.99-83.50 folds, p < 0.01), achieved successful bridging defect with the formation of both cortical bone like tissue externally and cancellous bone like tissue internally, and restored approximately 80% of the stiffness of the defected femur (benchmarked to the intact femur). It has been further observed that different bone regeneration patterns occurred in different TEBG implants and closely related to their vascularization patterns, revealing the potential profound influence of vascularization patterns on the osteogenesis pattern during defect healing.

Intraoperative Construct Preparation: A Practical Route for Cell-Based Bone Regeneration

Stem cell-based bone tissue engineering based on the combination of a scaffold and expanded autologous mesenchymal stem cells (MSCs) represents the current state-of-the-art treatment for bone defects and fractures. However, the procedure of such construct preparation requires extensive ex vivo manipulation of patient's cells to achieve enough stem cells. Therefore, it is impractical and not cost-effective compared to other therapeutic interventions. For these reasons, a more practical strategy circumventing any ex vivo manipulation and an additional surgery for the patient would be advantageous. Intraoperative concept-based bone tissue engineering, where constructs are prepared with easily accessible autologous cells within the same surgical procedure, allows for such a simplification. In this study, we discuss the concept of intraoperative construct preparation for bone tissue engineering and summarize the available cellular options for intraoperative preparation. Furthermore, we propose methods to prepare intraoperative constructs, and review data of currently available preclinical and clinical studies using intraoperatively prepared constructs for bone regenerative applications. We identify several obstacles hampering the application of this emerging approach and highlight perspectives of technological innovations to advance the future developments of intraoperative construct preparation.

Combining electrical stimulation and tissue engineering to treat large bone defects in a rat model

Bone Tissue engineering (BTE) has recently been introduced as an alternative to conventional treatments for large non-healing bone defects. BTE approaches mimic autologous bone grafts, by combining cells, scaffold, and growth factors, and have the added benefit of being able to manipulate these constituents to optimize healing. Electrical stimulation (ES) has long been used to successfully treat non-healing fractures and has recently been shown to stimulate bone cells to migrate, proliferate, align, differentiate, and adhere to bio compatible scaffolds, all cell behaviors that could improve BTE treatment outcomes. With the above in mind we performed in vitro experiments and demonstrated that exposing Mesenchymal Stem Cells (MSC) + scaffold to ES for 3 weeks resulted in significant increases in osteogenic differentiation. Then in in vivo experiments, for the first time, we demonstrated that exposing BTE treated rat femur large defects to ES for 8 weeks, caused improved healing, as indicated by increased bone formation, strength, vessel density, and osteogenic gene expression. Our results demonstrate that ES significantly increases osteogenic differentiation in vitro and that this effect is translated into improved healing in vivo. These findings support the use of ES to help BTE treatments achieve their full therapeutic potential.

Transplantation of copper-doped calcium polyphosphate scaffolds combined with copper (II) preconditioned bone marrow mesenchymal stem cells for bone defect repair

Calcium polyphosphate is a bioactive ceramic that possesses similar mineral components to bone and possess good physicochemical properties. However, pure calcium polyphosphate scaffold is brittle, and it is insufficient in promoting vascularization and osteoinductivity. This study was conducted to assess whether copper (Cu) incorporated into calcium polyphosphate could improve the scaffolds' inherent shortcomings. In the experiments, Cu-calcium polyphosphate scaffolds' mechanical strength, biocompatibility, and biodegradability were researched primarily. And then, hypoxia-inducible factor 1-alpha expression along with angiogenesis and osteogenesis potential when the scaffolds treated with the bone marrow mesenchymal stem cells (BMMSCs) were analyzed in vitro. In in vivo studies, the Cu-calcium polyphosphate scaffolds combined with the liquid extract preconditioned BMMSCs were implanted into animal model to repair the bone defects. Meanwhile, we also evaluate the expression of angiogenic and osteogenic factors. For comparison, Cu-calcium polyphosphate, calcium polyphosphate, and blank control groups were designed. According to the results, proper content of Cu incorporated with calcium polyphosphate (0.1% Cu-calcium polyphosphate) did not significantly change the scaffold's degradation velocity, but it obtained higher compress mechanical strength and Cu-doped scaffolds were less brittle. Besides, these scaffolds incorporated with Cu showed better cytocompatibility and cell proliferation activity. Moreover, after Cu was doped, the hypoxia-inducible factor 1-alpha expression was up-regulated with the angiogenic and osteogenic factors levels increased both in in vitro and in vivo study. The bone defect healing capacity was accessed, using Cu-calcium polyphosphate combined with preconditioned BMMSCs further enhanced new bone formation and improved hypoxia-inducible factor 1-alpha, alkaline phosphatase, osteocalcin, and vascular endothelial growth factor expression. In conclusion, doped Cu into calcium polyphosphate was an alternative strategy for improving calcium polyphosphate's mechanical property and promoting the osteogenesis and angiogenesis potential. Using Cu-calcium polyphosphate scaffolds combined with Cu preconditioned BMMSCs to treat bone defect could enhance bone defect healing.

Comparison of three different types of scaffolds preseeded with human bone marrow mononuclear cells on the bone healing in a femoral critical size defect model of the athymic rat

Large bone defects often pose major difficulties in orthopaedic surgery. The application of long-term cultured stem cells combined with a scaffold lead to a significant improvement of bone healing in recent experiments but is strongly restricted by European Union law. Bone marrow mononuclear cells (BMC), however, can be isolated and transplanted within a few hours and have been proven effective in experimental models of bone healing. The effectivity of the BMC-supported therapy might be influenced by the type of scaffold. Hence, we compared three different scaffolds serving as a carrier for BMC in a rat femoral critical size defect with regard to the osteogenic activity in the defect zone. Human demineralized bone matrix (DBM), bovine cancellous bone hydroxyapatite ceramic (BS), or β-tricalcium phosphate (β-TCP) were seeded with human BMC and hereafter implanted into critically sized bone defects of male athymic nude rats. Autologous bone served as a control. Gene activity was measured after 1 week, and bone formation was analysed histologically and radiologically after 8 weeks. Generally, regenerative gene expression (BMP2, RUNX2, VEGF, SDF-1, and RANKL) as well as bony bridging and callus formation was observed to be most pronounced in defects filled with autologous bone, followed in descending order by DBM, β-TCP, and BS. Although DBM was superior in most aspects of bone regeneration analysed in comparison to β-TCP and BS, the level of autologous bone could not be attained.

Rescued Chondrogenesis of Mesenchymal Stem Cells under Interleukin 1 Challenge by Foamyviral Interleukin 1 Receptor Antagonist Gene Transfer

Background: Mesenchymal stem cells (MSCs) and their chondrogenic differentiation have been extensively investigated in vitro as MSCs provide an attractive source besides chondrocytes for cartilage repair therapies. Here we established prototype foamyviral vectors (FVV) that are derived from apathogenic parent viruses and are characterized by a broad host range and a favorable integration pattern into the cellular genome. As the inflammatory cytokine interleukin 1 beta (IL1β) is frequently present in diseased joints, the protective effects of FVV expressing the human interleukin 1 receptor antagonist protein (IL1RA) were studied in an established in vitro model (aggregate culture system) of chondrogenesis in the presence of IL1β.

Materials and Methods: We generated different recombinant FVVs encoding enhanced green fluorescent protein (EGFP) or IL1RA and examined their transduction efficiencies and transgene expression profiles using different cell lines and human primary MSCs derived from bone marrow-aspirates. Transgene expression was evaluated by fluorescence microscopy (EGFP), flow cytometry (EGFP), and ELISA (IL1RA). For evaluation of the functionality of the IL1RA transgene to block the inhibitory effects of IL1β on chondrogenesis of primary MSCs and an immortalized MSC cell line (TERT4 cells), the cells were maintained following transduction as aggregate cultures in standard chondrogenic media in the presence or absence of IL1β. After 3 weeks of culture, pellets were harvested and analyzed by histology and immunohistochemistry for chondrogenic phenotypes.

Results: The different FVV efficiently transduced cell lines as well as primary MSCs, thereby reaching high transgene expression levels in 6-well plates with levels of around 100 ng/ml IL1RA. MSC aggregate cultures which were maintained in chondrogenic media without IL1β supplementation revealed a chondrogenic phenotype by means of strong positive staining for collagen type II and matrix proteoglycan (Alcian blue). Addition of IL1β was inhibitory to chondrogenesis in untreated control pellets. In contrast, foamyviral mediated IL1RA expression rescued the chondrogenesis in pellets cultured in the presence of IL1β. Transduced MSC pellets reached thereby very high IL1RA transgene expression levels with a peak of 1087 ng/ml after day 7, followed by a decrease to 194 ng/ml after day 21, while IL1RA concentrations of controls were permanently below 200 pg/ml.

Conclusion: Our results indicate that FVV are capable of efficient gene transfer to MSCs, while reaching IL1RA transgene expression levels, that were able to efficiently block the impacts of IL1β in vitro. FVV merit further investigation as a means to study the potential as a gene transfer tool for MSC based therapies for cartilage repair.

Comparison between mandibular and femur derived bone marrow stromal cells: osteogenic and angiogenic potentials in vitro and bone repairing ability in vivo

M-BMSCs contains stronger osteogenic and angiogenic potentials, and better bone repairing ability.

Safety and feasibility of cell-based therapy of autologous bone marrow-derived mononuclear cells in plate-stabilized proximal humeral fractures in humans

Background

Local implantation of ex vivo concentrated, washed and filtrated human bone marrow-derived mononuclear cells (BMC) seeded onto β-tricalciumphosphate (TCP) significantly enhanced bone healing in a preclinical segmental defect model. Based on these results, we evaluated in a first clinical phase-I trial safety and feasibility of augmentation with preoperatively isolated autologous BMC seeded onto β-TCP in combination with angle stable plate fixation for the therapy of proximal humeral fractures as a potential alternative to autologous bone graft from the iliac crest.

Methods

10 patients were enrolled to assess whether cell therapy with 1.3 × 10⁶ autologous BMC/ml/ml β-TCP, collected on the day preceding the definitive surgery, is safe and feasible when seeded onto β-TCP in patients with a proximal humeral fracture. 5 follow-up visits for clinical and radiological controls up to 12 weeks were performed.

Results

β-tricalciumphosphate fortification with BMC was feasible and safe; specifically, neither morbidity at the harvest site nor at the surgical wound site were observed. Neither local nor systemic inflammation was noted. All fractures healed within the observation time without secondary dislocation. Three adverse events were reported: one case each of abdominal wall shingles, tendon loosening and initial screw perforation, none of which presumed related to the IND.

Conclusions

Cell therapy with autologous BMC for bone regeneration appeared to be safe and feasible with no drug-related adverse reactions being described to date. The impression of efficacy was given, although the study was not powered nor controlled to detect such. A clinical trial phase-II will be forthcoming in order to formally test the clinical benefit of BMC-laden β-TCP for PHF patients.

Trial registration The study was registered in the European Clinical Trial Register as EudraCT No. 2012-004037-17. Date of registration 30th of August 2012. Informed consent was signed from all patients enrolled.

Autologous bone grafts with MSCs or FGF-2 accelerate bone union in large bone defects

BACGROUND

Although the contribution of fibroblast growth factor (FGF)-2 and mesenchymal stromal cells (MSCs) to bone formation is well known, few studies have investigated the combination of an autologous bone graft with FGF-2 or MSCs for large bone defects.

METHODS

We studied an atrophic non-union model with a large bone defect, created by resecting a 10-mm section from the center of each femoral shaft of 12-week-old Sprague-Dawley rats. The periosteum of the proximal and distal ends of the femur was cauterized circumferentially, and excised portions were used in the contralateral femur as autologous bone grafts. The rats were randomized to three groups and given no further treatment (group A), administered FGF-2 at 20 μg/20 μL (group B), or 1.0 × 10⁶ MSCs (group C). Radiographs were taken every 2 weeks up to 12 weeks, with CT performed at 12 weeks. Harvested femurs were stained with toluidine blue and evaluated using radiographic and histology scores.

RESULTS

Radiographic and histological evaluation showed that bone union had been achieved at 12 weeks in group C, while group B showed callus formation and bridging callus but non-union, and in group A, callus formation alone was evident. Both radiographic and histological scores were significantly higher at 2, 4, 6, 8, 10, and 12 weeks in groups B and C than group A and also significantly higher in group C than group B at 12 weeks.

CONCLUSIONS

These data suggest that autologous bone grafts in combination with MSCs benefit difficult cases which cannot be treated with autologous bone grafts alone.

Periimplant bone regeneration in hydroxyapatite block grafts with mesenchymal stem cells and bone morphogenetic protein-2

Hydroxyapatite (HA) blocks as an alternative material for autogenous onlay bone grafts are regarded as an insufficient substitute for osseointegration of dental implant. In this study, we evaluated the effects of dog mesenchymal stromal cells (dMSCs) with or without bone morphogenetic protein-2 (BMP) on new peri-implant bone formation after HA block graft. In four mandibular bone defects (8×8×6 mm each) in five beagle dogs, dental implants were placed with HA block loaded with autogenous dMSCs with or without BMP-2. Animals were sacrificed at eight weeks, and bone healing was evaluated among four groups consisting of 1) HA alone as a control, 2) HA+dMSCs, 3) HA+BMP-2, and 4) HA+dMSCs+BMP-2. According to histomorphometric evaluation, the MSC+BMP-2 group and the BMP-2 group showed significantly higher bone-implant-contact (BIC) length than the MSC group, while there was no significant difference in new bone formation among the groups. According to micro-CT analysis, bone volume and bone mineral density were significantly higher in the MSC+BMP-2 group compared with the control group (p<0.01 and p<0.05, respectively). BIC was significantly higher in the MSC+BMP-2 group than both the control and MSC groups (p<0.01 and p<0.05, respectively). In conclusion, our results showed that bone regeneration at peri-implant bone defects grafted with HA blocks was significantly increased by dual delivery of MSCs and BMP-2. Conversely, HA blocks with MSC or BMP-2 alone did not allow for efficient peri-implant bone regeneration.

Treatment of Large Bone Defects with a Vascularized Periosteal Flap in Combination with Biodegradable Scaffold Seeded with Bone Marrow-Derived Mononuclear Cells: An Experimental Study in Rats

INTRODUCTION

The surgical treatment of large bone defects continues to pose a major challenge in modern trauma and orthopedic surgery. In this study we test the effectiveness of a tissue engineering approach, using three-dimensional (3D) β-tricalcium phosphate (β-TCP) scaffolding plus bone marrow-derived mononuclear cells (BM-MNCs), combined with a vascularized periosteal flap, in a rat femur critical size defect model.

METHODS

Eighty rats were randomly allocated into four equal groups. Under general anesthesia, critical size defects were created on their femurs and were treated with (1) Vascularized periosteal flap alone, (2) Vascularized periosteal flap+β-TCP scaffolding, (3) Vascularized periosteal flap+β-TCP scaffolding+ligated vascular pedicle, and (4) Vascularized periosteal flap+β-TCP scaffolding+BM-MNCs. After 4 and 8 weeks animals were euthanized and the bone defects were harvested for analysis of new bone formation, vascularization, and strength using histology, immunohistology, micro-CT, and biomechanical testing, respectively.

RESULTS

Group 1: (P. flap) Increase in new bone formation and vascularization. Group 2: (P. flap+scaffold) Increase in new bone formation and vascularization. Group 3: (P. flap+scaffold+ligated vascular pedicle) No new bone formation and no vascularization. Group 4: (P. flap+scaffold+BM-MNCs) A significant (p < 0.05) increase was seen in new bone formation, vascularization, and strength in bones treated with flaps, scaffold, and BM-MNCs, when compared with the other treatment groups.

CONCLUSION

Combining a vascularized periosteal flap with tissue engineering approach (β-TCP scaffolding and BM-MNC) results in significantly improved bone healing in our rat femur critical size bone defect model.