Mesenchymal stem cells and porous β-tricalcium phosphate composites prepared through stem cell screen-enrich-combine(-biomaterials) circulating system for the repair of critical size bone defects in goat tibia

Mechanisms and applications of the regenerative capacity of platelets-based therapy in knee osteoarthritis

Osteoarthritis (OA) is the most prevalent joint disease in the elderly population and its substantial morbidity and disability impose a heavy economic burden on patients and society. Knee osteoarthritis (KOA) is the most common subtype of OA, which is characterized by damage to progressive articular cartilage, synovitis, and subchondral bone sclerosis. Most current treatments for OA are palliative, primarily aim at symptom management, and do not prevent the progression of the disease or restore degraded cartilage. The activation of α-granules in platelets releases various growth factors that are involved in multiple stages of tissue repair, suggesting potential for disease modification. In recent years, platelet-based therapies, such as platelet-rich plasma, platelet-rich fibrin, and platelet lysates, have emerged as promising regenerative treatments for KOA, but their related effects and mechanisms are still unclear. Therefore, this review aims to summarize the biological characteristics and functions of platelets, classify the products of platelet-based therapy and related preparation methods. Moreover, we summarize the basic research of platelet-based regeneration strategies for KOA and discuss the cellular effects and molecular mechanisms. Further, we describe the general clinical application of platelet-based therapy in the treatment of KOA and the results of the meta-analysis of randomized controlled trials.

Improved new bone formation capacity of hyaluronic acid-bone substitute compound in rat calvarial critical size defect

BACKGROUND

Bone loss of residual alveolar ridges is a great challenge in the field of dental implantology. Deproteinized bovine bone mineral (DBBM) is commonly used for bone regeneration, however, it is loose and difficult to handle in clinical practice. Hyaluronic acid (HA) shows viscoelasticity, permeability and excellent biocompatibility. The aim of this study is to evaluate whether high-molecular-weight (MW) HA combined with DBBM could promote new bone formation in rat calvarial critical size defects (CSDs).

MATERIALS AND METHODS

Rat calvarial CSDs (5 mm in diameter) were created. Rats (n = 45) were randomly divided into 3 groups: HA-DBBM compound grafting group, DBBM particles only grafting group and no graft group. Defect healing was assessed by hematoxylin-eosin staining and histomorphometry 2, 4 and 8 weeks postop, followed by Micro-CT scanning 8 weeks postop. Statistical analyses were performed by ANOVA followed by Tukey's post hoc test with P < 0.05 indicating statistical significance.

RESULTS

All rats survived after surgery. Histomorphometric evaluation revealed that at 2, 4 and 8 weeks postop, the percentage of newly formed bone was significantly greater in HA-DBBM compound grafting group than in the other two groups. Consistently, Micro-CT assessment revealed significantly more trabecular bone (BV/TV and Tb.N) in HA-DBBM compound group than in the other two groups, respectively (P < 0.05). Moreover, the trabecular bone was significantly more continuous (Tb.Pf) in HA-DBBM compound group than in the other two groups, respectively (P < 0.05).

CONCLUSION

HA not only significantly promoted new bone formation in rats calvarial CSDs but also improved the handling ability of DBBM.

Research Progress on Cardiac Tissue Construction of Mesenchymal Stem Cells for Myocardial Infarction

Heart failure is still the main complication affecting the prognosis of acute myocardial infarction (AMI), and mesenchymal stem cells (MSCs) are an effective treatment to replace necrotic myocardium and improve cardiac functioning. However, the transplant survival rate of MSCs still presents challenges. In this review, the biological characteristics of MSCs, the progress of mechanism research in the treatment of myocardial infarction, and the advances in improving the transplant survival rate of MSCs in the replacement of necrotic myocardial infarction are systematically described. From a basic to advanced clinical research, MSC transplants have evolved from a pure injection, an exosome injection, the genetic modification of MSCs prior to injection to the cardiac tissue engineering of MSC patch grafting. This study shows that MSCs have wide clinical applications in the treatment of AMI, suggesting improved myocardial tissue creation. A broader clinical application prospect will be explored and developed to improve the survival rate of MSC transplants and myocardial vascularization.

Lignin-enriched tricalcium phosphate/sodium alginate 3D scaffolds for application in bone tissue regeneration

The bone is a connective, vascularized, and mineralized tissue that confers protection to organs, and participates in the support and locomotion of the human body, maintenance of homeostasis, as well as in hematopoiesis. However, throughout the lifetime, bone defects may arise due to traumas (mechanical fractures), diseases, and/or aging, which when too extensive compromise the ability of the bone to self-regenerate. To surpass such clinical situation, different therapeutic approaches have been pursued. Rapid prototyping techniques using composite materials (consisting of ceramics and polymers) have been used to produce customized 3D structures with osteoinductive and osteoconductive properties. In order to reinforce the mechanical and osteogenic properties of these 3D structures, herein, a new 3D scaffold was produced through the layer-by-layer deposition of a tricalcium phosphate (TCP), sodium alginate (SA), and lignin (LG) mixture using the Fab@Home 3D-Plotter. Three different TCP/LG/SA formulations, LG/SA ratio 1:3, 1:2, or 1:1, were produced and subsequently evaluated to determine their suitability for bone regeneration. The physicochemical assays demonstrated that the LG inclusion improved the mechanical resistance of the scaffolds, particularly in the 1:2 ratio, since a 15 % increase in the mechanical strength was observed. Moreover, all TCP/LG/SA formulations showed an enhanced wettability and maintained their capacity to promote the osteoblasts' adhesion and proliferation as well as their bioactivity (formation of hydroxyapatite crystals). Such results support the LG inclusion and application in the development of 3D scaffolds aimed for bone regeneration.

Intraoperative Creation of Tissue-Engineered Grafts with Minimally Manipulated Cells: New Concept of Bone Tissue Engineering In Situ

Transfer of regenerative approaches into clinical practice is limited by strict legal regulation of in vitro expanded cells and risks associated with substantial manipulations. Isolation of cells for the enrichment of bone grafts directly in the Operating Room appears to be a promising solution for the translation of biomedical technologies into clinical practice. These intraoperative approaches could be generally characterized as a joint concept of tissue engineering in situ. Our review covers techniques of intraoperative cell isolation and seeding for the creation of tissue-engineered grafts in situ, that is, directly in the Operating Room. Up-to-date, the clinical use of tissue-engineered grafts created in vitro remains a highly inaccessible option. Fortunately, intraoperative tissue engineering in situ is already available for patients who need advanced treatment modalities.

Mesenchymal Stem Cell Studies in the Goat Model for Biomedical Research—A Review of the Scientific Literature

Simple Summary

This review article aims to compile the works published in the scientific literature, over the last two decades, that use the goat as an animal model in preclinical studies using stem cells, alone or associated with biomaterials, for the treatment of injury or disease in divers organ systems. These preclinical studies are performed prior to human clinical trials for the implementation of new medical or surgical therapies in clinical practice. Thus, it appears that, in the area of tissue engineering and regenerative medicine, the caprine model is particularly used in studies using stem cells in the musculoskeletal system but, although in a more limited way, also in the field of dermatology, ophthalmology, dentistry, pneumology, cardiology, and urology. It appears that the goat represents a particularly useful animal model for studies related to the locomotor system because of its size, and also because they have a more active behavior than sheep, being more similar to the human species in this aspect. Additionally, the goat knee anatomy and the thickness of the cartilage that covers this joint are closer to that of humans than that of other large animal models commonly used in orthopedic research.

Abstract

Mesenchymal stem cells (MSCs) are multipotent cells, defined by their ability to self-renew, while maintaining the capacity to differentiate into different cellular lineages, presumably from their own germinal layer. MSCs therapy is based on its anti-inflammatory, immunomodulatory, and regenerative potential. Firstly, they can differentiate into the target cell type, allowing them to regenerate the damaged area. Secondly, they have a great immunomodulatory capacity through paracrine effects (by secreting several cytokines and growth factors to adjacent cells) and by cell-to-cell contact, leading to vascularization, cellular proliferation in wounded tissues, and reducing inflammation. Currently, MSCs are being widely investigated for numerous tissue engineering and regenerative medicine applications. Appropriate animal models are crucial for the development and evaluation of regenerative medicine-based treatments and eventual treatments for debilitating diseases with the hope of application in upcoming human clinical trials. Here, we summarize the latest research focused on studying the biological and therapeutic potential of MSCs in the goat model, namely in the fields of orthopedics, dermatology, ophthalmology, dentistry, pneumology, cardiology, and urology fields.

Bone Beads Enveloped with Vascular Endothelial Cells for Bone Regenerative Medicine

The transplantation of pre-vascularized bone grafts is a promising strategy to improve the efficacy of engraftment and bone regeneration. We propose a hydrogel microbead-based approach for preparing vascularized and high-density tissue grafts. Mesenchymal stem cell-encapsulated collagen microgels (2 µL), termed bone beads, were prepared through spontaneous constriction, which improved the density of the mesenchymal stem cells and collagen molecules by more than 15-fold from the initial day of culture. Constriction was attributed to cell-attractive forces and involved better osteogenic differentiation of mesenchymal stem cells than that of spheroids. This approach was scalable, and ∼2,000 bone beads were prepared semi-automatically using a liquid dispenser and spinner flask. The mechanical stimuli in the spinner flask further improved the osteogenic differentiation of the mesenchymal stem cells in the bone beads compared with that in static culture. Vascular endothelial cells readily attach to and cover the surface of bone beads. The in vitro assembly of the endothelial cell-enveloped bone beads resulted in microchannel formation in the interspaces between the bone beads. Significant effects of endothelialization on in vivo bone regeneration were shown in rats with cranial bone defects. The use of endothelialized bone beads may be a scalable and robust approach for treating large bone defects. STATEMENT OF SIGNIFICANCE: A unique aspect of this study is that the hMSC-encapsulated collagen microgels were prepared through spontaneous constriction, leading to the enrichment of collagen and cell density. This constriction resulted in favorable microenvironments for the osteogenic differentiation of hMSCs, which is superior to conventional spheroid culture. The microgel beads were then enveloped with vascular endothelial cells and assembled to fabricate a tissue graft with vasculature in the interspaces among the beads. The significant effects of endothelialization on in vivo bone regeneration were clearly demonstrated in rats with cranial bone defects. We believe that microgel beads covered with vascular endothelial cells provide a promising approach for engineering better tissue grafts for bone-regenerative medicine.

A review on bioceramics scaffolds for bone defect in different types of animal models: HA and β -TCP

Increased life expectancy has led to an increase in the use of bone substitutes in numerous nations, with over two million bone-grafting surgeries performed worldwide each year. A bone defect can be caused by trauma, infections, and tissue resections which can self-heal due to the osteoconductive nature of the native extracellular matrix components. However, natural self-healing is time-consuming, and new bone regeneration is slow, especially for large bone defects. It also remains a clinical challenge for surgeons to have a suitable bone substitute. To date, there are numerous potential treatments for bone grafting, including gold-standard autografts, allograft implantation, xenografts, or bone graft substitutes. Tricalcium phosphate (TCP) and hydroxyapatite (HA) are the most extensively used and studied bone substitutes due to their similar chemical composition to bone. The scaffolds should be testedin vivoandin vitrousing suitable animal models to ensure that the biomaterials work effectively as implants. Hence, this article aims to familiarize readers with the most frequently used animal models for biomaterials testing and highlight the available literature for in vivo studies using small and large animal models. This review summarizes the bio ceramic materials, particularly HA and β-TCP scaffolds, for bone defects in small and large animal models. Besides, the design considerations for the pre-clinical animal model selection for bone defect implants are emphasized and presented.

In vivo evaluation of bone regeneration behavior of novel β-tricalcium phosphate/layered double hydroxide nanocomposite granule as bone graft substitutes

This study was based on in vivo assessment of bone regeneration capacity of synthesized porous β-tricalcium phosphate (β-TCP) nanocomposite granules and aimed to explore the effects of fabricated β-TCP granules reinforced with layered double hydroxides (LDH) nanoclay compared to β-TCP granules, in terms of osteoconductivity and biodegradability. Granules with diameters of 2-3 mm were implanted into cavities drilled in rabbit distal femur and were left in situ for up to 3 months. The mechanical study demonstrated that the presence of LDH nanoparticles in β-TCP granules resulted in a significant increase in compressive modulus from 174.4 to 231.4 MPa, while the porosity was constant at 76%-80%. The results revealed that the obtained granules showed no cytotoxicity. In this study, x-ray radiographic, micro-computed tomography, and histological staining analysis were taken to evaluate the percentage of bone ingrowth and biodegradability of the porous granules. The results exhibited that both granules support bone regeneration and also the amount of new bone formation in the bone defect filled with both granules was almost six times higher than the empty defects. Although no significant difference in bone formation for two different granules was observed, a higher biodegradability was detected in β-TCP granules in comparison to β-TCP/LDH granules. Overall, the addition of LDH nanoclay (10%) enhanced the physicochemical and mechanical properties of β-TCP granules while it is biological and osteoconductity properties have been maintained and its biodegradation rate has been decreased.

Mesenchymal Stem Cells, Bioactive Factors, and Scaffolds in Bone Repair: From Research Perspectives to Clinical Practice

Mesenchymal stem cell-based therapies are promising tools for bone tissue regeneration. However, tracking cells and maintaining them in the site of injury is difficult. A potential solution is to seed the cells onto a biocompatible scaffold. Construct development in bone tissue engineering is a complex step-by-step process with many variables to be optimized, such as stem cell source, osteogenic molecular factors, scaffold design, and an appropriate in vivo animal model. In this review, an MSC-based tissue engineering approach for bone repair is reported. Firstly, MSC role in bone formation and regeneration is detailed. Secondly, MSC-based bone tissue biomaterial design is analyzed from a research perspective. Finally, examples of animal preclinical and human clinical trials involving MSCs and scaffolds in bone repair are presented.

The effectiveness of hydroxyapatite-beta tricalcium phosphate incorporated into stem cells from human exfoliated deciduous teeth for reconstruction of rat calvarial bone defects

OBJECTIVE

To investigate the effects of stem cells from the pulp of human exfoliated deciduous teeth (SHED) on biphasic calcium phosphate granules (BCP) to repair rat calvarial defects as compared to autogenous bone grafting.

MATERIALS AND METHODS

A defect with a 6-mm diameter was produced on the calvaria of 50 rats. BCP granules were incorporated into SHED cultures grown for 7 days in conventional (CM) or osteogenic (OM) culture media. The animals were allocated into 5 groups of 10, namely: clot, autogenous bone, BCP, BCP+SHED in CM (BCP-CM), and BCP+SHED in OM (BCP-OM). The presence of newly formed bone and residual biomaterial particles was assessed by histometric analysis after 4 and 8 weeks.

RESULTS

The autogenous group showed the largest newly formed bone area at week 8 and in the entire experimental period, with a significant difference in relation to the other groups (P < 0.05). At week 8, BCP-CM and BCP-OM groups showed homogeneous new bone formation (P = 0.13). When considering the entire experimental period, the BCP group had the highest percentage of residual particle area, with no significant difference from the BCP-CM group (P = 0.06) and with a significant difference from the BCP-OM group (P = 0.01). BCP-CM and BCP-OM groups were homogeneous throughout the experimental period (P = 0.59).

CONCLUSIONS

BCP incorporated into SHED cultures showed promising outcomes, albeit less pronounced than autogenous grafting, for the repair of rat calvarial defects.

CLINICAL RELEVANCE

BCP incorporated into SHED cultures showed to be an alternative in view of the disadvantages to obtain autogenous bone graft.

Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model

The objective of this study was to evaluate changes in peak reverse torque (PRT) of the locking head screws that occur over time. A locking plate construct, consisting of an 8-hole locking plate and 8 locking screws, was used to stabilize a tibia segmental bone defect in a goat model. PRT was measured after periods of 3, 6, 9, and 12 months of ambulation. PRT for each screw was determined during plate removal. Statistical analysis revealed that after 6 months of loading, locking screws placed in position no. 4 had significantly less PRT as compared with screws placed in position no. 5 (p < 0.05). There were no statistically significant differences in PRT between groups as a factor of time (p > 0.05). Intracortical fractures occurred during the placement of 151 out of 664 screws (22.7%) and were significantly more common in the screw positions closest to the osteotomy (positions 4 and 5, p < 0.05). Periosteal and endosteal bone reactions and locking screw backout occurred significantly more often in the proximal bone segments (p < 0.05). Screw backout significantly, negatively influenced the PRT of the screws placed in positions no. 3, 4, and 5 (p < 0.05). The locking plate-screw constructs provided stable fixation of 2.5-cm segmental tibia defects in a goat animal model for up to 12 months.

Experimental study on repair of large segmental bone defects of goat femur by nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer membrane tubes

OBJECTIVE

The purpose of this study was to observe feasibility of nano calcium-deficient hydroxyapatite-multi (amino acid) copolymer (n-CDHA-MAC) membrane tubes in repairing goat femurs' large defects.

METHODS

Twelve goats were divided into two groups, whose femurs were created 30 mm segmental bone defects and then implants were performed. In experimental group, the bone defect of right femur was reconstructed by n-CDHA-MAC membrane tube, while left side was reconstructed by allogenic bone tube in control group. Every three goats were sacrificed at 4, 8, 16, 24 weeks after operation respectively. General observation, X-ray analysis, histology, Scanning electron microscope (SEM) examination and protein level comparison of BMP-2 were conducted to evaluate the effects of repairing segmental bone defects.

RESULTS

All goats recovered well from anesthesia and surgical interventions. The radiographic evaluations showed that periosteal reaction outside of the membrane tubes and allogenic bone tubes were observed 4 weeks after surgery. At 16 weeks, callus was continuously increased in experimental group, which was more obvious than control group. At 24 weeks, callus outside of the membrane tubes connected together. Histologic evaluation showed fibro-cartilage callus was evolved into bony callus in experimental group, which was more obvious than control group at 8 and 16 weeks. The protein expression level of BMP-2 increased at 4, 8 weeks and peaked at 16 weeks in experimental groups. There were statistical differences at 8 and 16 weeks (P < 0.05). At each time point in 8, 16, 24 weeks after surgery, the bending stiffness, torsional stiffness and compressive strength of the two groups were similar, and there was no significant difference (P > 0.05).

CONCLUSIONS

This novel surface degradation n-CDHA-MAC membrane tube has good ability to maintain enough membrane space, which can provide long-term and stable biomechanical support for large bone defects and integrate well with the surrounding bone.

Use of a novel Screen-Enrich-Combine(-biomaterials) Circulating System to fill a 3D-printed open Ti6Al4V frame with mesenchymal stem cells/β-tricalcium phosphate to repair complex anatomical bone defects in load-bearing areas

Background

Repairing complex anatomical load-bearing bone defects is difficult because it requires the restoration of the load-bearing function, reconstructing the anatomical shape, and repair by regenerated bone. We previously developed a Screen–Enrich–Combine(-biomaterials) Circulating System (SECCS) for rapid intraoperative enrichment of autologous bone marrow mesenchymal stem cells (MSCs) to enhance the osteogenic ability of porous bone substitutes. In this study, we prepared a 3D-printed Ti6A14V macroporous frame matching the defect shape to provide early load-bearing support and evaluated the efficacy of filling the frame with SECCS-processed MSCs/beta tricalcium phosphate (β-TCP) for long-term bone growth.

Methods

Fifteen 2-year-old goats were involved in this study, and the lateral part of their distal femur was removed by an electric saw and was fitted by a matching electron beam melting technology-prepared (EBM) Ti6Al4V frame. Three types of frames, filled with nothing, pure porous β-TCP, or SECCS-processed MSCs/β-TCP, were fixed onto the defect site. Repair efficacy was evaluated by X-ray radiography, computed tomography (CT), histology, and histomorphometry.

Results

In the basic regular hexagon printing unit, the combined side width (w) and the inscribed circle diameter (d) determines the printing frame’s mechanical strength. The compressive load was significantly higher for w=1.9 mm, d=4.4 mm than for w=1.7 mm, d=4.0 mm or w=2.0 mm, d=5.0 mm (P<0.05). The EBM-prepared Ti6Al4V defect-matched frame was well maintained 9 months after implantation. The MSCs successfully adhered to the wall of the porous β-TCP in the SECCS-processed group and had spread fully in the test samples. Each goat in the MSCs/β-TCP–the filled group, had approximately 31,321.7±22,554.7 of MSCs and a larger area of new bone growth inside the frame than the control and blank areas groups.

Conclusions

Filling the 3D-printed Ti6Al4V large-aperture frame with osteogenic materials achieved biological reconstruction over a larger area of regenerated bone to repair complex anatomical weight-bearing bone defects under the condition of early frame-supported load bearing. MSCs/β-TCP prepared by SECCS can be used as a filling material for this type of bone defect to obtain more efficacious bone repair.

[Lentivirus-mediated silencing of P75 neurotrophin receptor combined with nerve growth factor overexpression and transfection of bone marrow mesenchymal stem cells combined with demineralized bone matrix for heterotopic osteogenesis]

Objective

To investigate the effects of silencing P75 neurotrophin receptor (P75NTR) and nerve growth factor (NGF) overexpression on the proliferative activity and ectopic osteogenesis ability of bone marrow mesenchymal stem cells (BMSCs) combined with demineralized bone matrix for heterotopic osteogenesis.

Methods

BMSCs of Sprague Dawley (SD) rats were cultured and passaged by adherent isolation method. The third generation BMSCs were transfected with lentivirus mediated P75NTR gene silencing (group B), NGF overexpression gene (group C), P75NTR silencing and NGF overexpression double genes (group D), respectively, and untransfected cells as control (group A). After 7 days of transfection, the expression of fluorescent protein of the target gene was observed by fluorescence microscope; cell counting kit 8 method was used to detect the cells activity for 8 days after transfection; the expressions of P75NTR and NGF proteins in each group were detected by Western blot. The adhesion of BMSCs to demineralized bone matrix (DBM) was observed by inverted phase contrast microscope and scanning electron microscope after transfection of p75NTR silencing and NGF overexpression double genes. After transfection, BMSCs and DBM were co-cultured to prepare 4 groups of tissue engineered bone, which were respectively placed in the dorsal subcutaneous tissue of 8-week-old SD rats to construct subcutaneous ectopic osteogenesis model ( n=6). HE staining was performed at 4 and 8 weeks after operation. ALP staining was used to observe the formation of calcium nodules at 8 weeks after operation. The expressions of Runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), and osteocalcin (OCN) were detected by real-time fluorescent quantitative PCR.

Results

At 7 days after transfection, there was no fluorescence expression in group A, red fluorescence expression was seen in group B, green fluorescence expression in group C, and red-green compound fluorescence expression in group D. The fluorescence expression rate of target gene was about 70%. Western blot detection showed that the relative expression of P75NTR protein in groups A and C was significantly higher than that in groups B and D, and the relative expression of NGF protein in groups C and D was significantly higher than that in groups A and B ( P<0.05). With the passage of time, the cell proliferation activity increased in all groups, especially in group D, which was significantly higher than that in group A at 3-8 days ( P<0.05). The results of inverted phase contrast microscope and scanning electron microscope showed that BMSCs could adhere well to DBM. In the subcutaneous ectopic osteogenesis experiment, HE staining showed that at 4 and 8 weeks after operation, the more bone tissue was formed in group D than in the other 3 groups. ALP staining showed that group D had the highest ALP activity and better osteogenic expression. Compared with group A, the relative expressions of Runx2, ALP, and OCN mRNAs in group D were significantly higher than those in group A ( P<0.05).

Conclusion

Silencing P75NTR and NGF overexpression double genes co-transfected BMSCs with DBM to construct tissue engineered bone has good ectopic osteogenic ability. By increasing NGF level and closing P75NTR apoptosis channel, it can not only improve cell activity, but also promote bone tissue regeneration.

Recent Advances in Biomaterials for the Treatment of Bone Defects

Bone defects or fractures generally heal in the absence of major interventions due to the high regenerative capacity of bone tissue. However, in situations of severe/large bone defects, these orchestrated regeneration mechanisms are impaired. With advances in modern medicine, natural and synthetic bio-scaffolds from bioceramics and polymers that support bone growth have emerged and gained intense research interest. In particular, scaffolds that recapitulate the molecular cues of extracellular signals, particularly growth factors, offer potential as therapeutic bone biomaterials. The current challenges for these therapies include the ability to engineer materials that mimic the biological and mechanical properties of the real bone tissue matrix, whilst simultaneously supporting bone vascularization. In this review, we discuss the very recent innovative strategies in bone biomaterial technology, including those of endogenous biomaterials and cell/drug delivery systems that promote bone regeneration. We present our understanding of their current value and efficacy, and the future perspectives for bone regenerative medicine.

Ceramic Scaffolds in a Vacuum Suction Handle for Intraoperative Stromal Cell Enrichment

During total joint replacement, high concentrations of mesenchymal stromal cells (MSCs) are released at the implantation site. They can be found in cell–tissue composites (CTC) that are regularly removed by surgical suction. A surgical vacuum suction handle was filled with bone substitute granules, acting as a filter allowing us to harvest CTC. The purpose of this study was to investigate the osteopromotive potential of CTC trapped in the bone substitute filter material during surgical suction. In the course of 10 elective total hip and knee replacement surgeries, β-tricalcium-phosphate (TCP) and cancellous allograft (Allo) were enriched with CTC by vacuum suction. Mononuclear cells (MNC) were isolated from the CTC and investigated towards cell proliferation and colony forming unit (CFU) formation. Furthermore, MSC surface markers, trilineage differentiation potential and the presence of defined cytokines were examined. Comparable amounts of MNC and CFUs were detected in both CTCs and characterized as MSC‰ of MNC with 9.8 ± 10.7‰ for the TCP and 12.8 ± 10.2‰ for the Allo (p = 0.550). CTCs in both filter materials contain cytokines for stimulation of cell proliferation and differentiation (EGF, PDGF-AA, angiogenin, osteopontin). CTC trapped in synthetic (TCP) and natural (Allo) bone substitute filters during surgical suction in the course of a joint replacement procedure include relevant numbers of MSCs and cytokines qualified for bone regeneration.

The effect of induced membranes combined with enhanced bone marrow and 3D PLA-HA on repairing long bone defects in vivo

The repair of large bone defects has always been a challenge, especially with respect to regeneration capacity and autogenous bone availability. To address this problem, we fabricated a 3D-printed polylactic acid (PLA) and hydroxyapatite (HA) scaffold (3D-printed PLA-HA, providing scaffold) loaded with enhanced bone marrow (eBM, providing seed cells) combined with induced membrane (IM, providing grow factors) to repair large radial defects in rabbits. in vitro assays, we demonstrated that 3D-printed PLA-HA had excellent biocompatibility, as shown by co-culturing with mesenchymal stem cells (MSCs); eBM-derived MSCs exhibited considerable differentiation potential, as shown in trilineage differentiation assays. To investigate bone formation efficacy in vivo, the rabbit radial long bone defect model was established. In the first stage, polymethylmethacrylate (PMMA) was inserted into the bone defect to stimulate the formation of IM; in the second stage, iliac crest bone graft (ICBG) with IM, PLA-HA alone with the removal of IM, PLA-HA with IM, and PLA-HA in conjunction with IM and eBM were sequentially applied to repair the long bone defect. At 8, 12, and 16 weeks, X-ray plain radiography, microcomputed tomography, and histological analysis were performed to evaluate the efficacy of bone repair and bone regeneration in each group. We found that IM combined with PLA-HA and eBM prominently enhanced bone repair and reconstruction, equivalent to that of IM/ICBG. Taken together, the data suggest that PLA-HA loaded with eBM combined with IM can be an alternative to IM with bone autografts for the treatment of large bone defects.

Influence of inflammatory conditions provided by macrophages on osteogenic ability of mesenchymal stem cells

BACKGROUND

The mechanisms by which macrophage phenotype contributes to mesenchymal stem cells (MSC)-mediated bone repair remain unclear. In this work, we investigated the influence of factors released by human macrophages polarized to a pro-inflammatory or an anti-inflammatory phenotype on the ability of human MSC to attach, migrate, and differentiate toward the osteoblastic lineage. We focused on the role of TNF-α and IL-10, key pro-inflammatory and anti-inflammatory cytokines, respectively, in regulating MSC functions.

METHODS

MSC were treated with media conditioned by pro-inflammatory or anti-inflammatory macrophages to study their influence in cell attachment, migration, and osteogenic differentiation. The involvement of TNF-α and IL-10 in the regulation of MSC functions was investigated using neutralizing antibodies and recombinant cytokines.

RESULTS

Treatment of MSC with media conditioned by pro-inflammatory or anti-inflammatory macrophages promoted cell elongation and enhanced MSC ability to attach and migrate. These effects were more noticeable when MSC were treated with media from pro-inflammatory macrophages. Interestingly, MSC osteogenic activity was enhanced by factors released by anti-inflammatory macrophages, but not by pro-inflammatory macrophages. Significant IL-10 levels originated from anti-inflammatory macrophages enhanced MSC osteogenesis by increasing ALP activity and mineralization in MSC layers cultured under osteogenic conditions. Moreover, macrophage-derived IL-10 regulated the expression of the osteogenic markers RUNX2, COL1A1, and ALPL. Notably, low TNF-α levels secreted by anti-inflammatory macrophages increased ALP activity in differentiating MSC whereas high TNF-α levels produced by pro-inflammatory macrophages had no effects on osteogenesis. Experiments in which MSC were treated with cytokines revealed that IL-10 was more effective in promoting matrix maturation and mineralization than TNF-α.

CONCLUSIONS

Factors secreted by pro-inflammatory macrophages substantially increased MSC attachment and migration whereas those released by anti-inflammatory macrophages enhanced MSC osteogenic activity as well as cell migration. IL-10 was identified as an important cytokine secreted by anti-inflammatory macrophages that potentiates MSC osteogenesis. Our findings provide novel insights into how environments provided by macrophages regulate MSC osteogenesis, which may be helpful to develop strategies to enhance bone regeneration.

The effect of combination therapy on critical-size bone defects using non-activated platelet-rich plasma and adipose-derived stem cells

PURPOSE

Non-activated platelet-rich plasma (nPRP) slowly releases growth factors that induce bone regeneration. Adipose tissue-derived stem cells (ASCs) are also known to induce osteoblast differentiation. In this study, we investigated the combined effect of nPRP and ASC treatment compared with single therapy on bone regeneration.

METHODS

Thirty New Zealand white rabbits with 15 × 15 mm² calvarial defects were randomly divided into four treatment groups: control, nPRP, ASC, or nPRP + ASC groups. For treatment, rabbits received a collagen sponge (Gelfoam®) saturated with 1 ml normal saline (controls), 1 ml non-activated PRP (nPRP group), 2 × 10⁶ ASCs (ASCs group), or 2 × 10⁶ ASCs plus l ml nPRP (nPRP + ASCs group). After 16 weeks, bone volume and new bone surface area were measured, using three-dimensional computed tomography and digital photography. Bone regeneration was also histologically analyzed.

RESULTS

Bone surface area in the nPRP group was significantly higher than both the control and ASC groups (p < 0.001 and p < 0.01, respectively). The percentage of regenerated bone surface area in the nPRP + ASC group was also significantly higher than the corresponding ratios in the control group (p < 0.001). The volume of new bone in the nPRP group was increased compared to the controls (p < 0.05).

CONCLUSION

Our results demonstrate that slow-releasing growth factors from nPRP did not influence ASC activation in this model of bone healing. PRP activation is important for the success of combination therapy using nPRP and ASCs.

Comparison and characterization of enriched mesenchymal stem cells obtained by the repeated filtration of autologous bone marrow through porous biomaterials

Background

When bone marrow is repeatedly filtered through porous material, the mesenchymal stem cells (MSCs) in the bone marrow can adhere to the outer and inner walls of the carrier material to become enriched locally, and this is a promising method for MSC enrichment. In this process, the enrichment efficiency of MSCs involved in the regulation of the cell ecology of postfiltration composites containing other bone marrow components is affected by many factors. This study compared the enrichment efficiency and characterized the phenotypes of enriched MSCs obtained by the filtration of autologous bone marrow through different porous bone substitutes.

Methods

Human bone marrow was filtered through representative porous materials, and different factors affecting MSC enrichment efficiency were evaluated. The soluble proteins and MSC phenotypes in the bone marrow before and after filtration were also compared.

Results

The enrichment efficiency of the MSCs found in gelatin sponges was 96.1% ± 3.4%, which was higher than that of MSCs found in allogeneic bone (72.5% ± 7.6%) and porous β-TCP particles (61.4% ± 5.4%). A filtration frequency of 5–6 and a bone marrow/material volume ratio of 2 achieved the best enrichment efficiency for MSCs. A high-throughput antibody microarray indicated that the soluble proteins were mostly filtered out and remained in the flow through fluid, whereas a small number of proteins were abundantly (> 50%) enriched in the biomaterial. In terms of the phenotypic characteristics of the MSCs, including the cell aspect ratio, osteogenetic fate, specific antigens, gene expression profile, cell cycle stage, and apoptosis rate, no significant changes were found before or after filtration.

Conclusion

When autologous bone marrow is rapidly filtered through porous bone substitutes, the optimal enrichment efficiency of MSCs can be attained by the rational selection of the type of carrier material, the bone marrow/carrier material volume ratio, and the filtration frequency. The enrichment of bone marrow MSCs occurs during filtration, during which the soluble proteins in the bone marrow are also absorbed to a certain extent. This filtration enrichment technique does not affect the phenotype of the MSCs and thus may provide a safe alternative method for MSC enrichment.

Screen-enrich-combine circulating system to prepare MSC/β-TCP for bone repair in fractures with depressed tibial plateau

Aim: To evaluate the clinical efficacy of mesenchymal stem cell/β-tricalcium phosphate composites (MSC/β-TCP) prepared with a screen-enrich-combine circulating system (SECCS) in patients with depressed tibial plateau fractures. Materials & methods: Bone defects in depressed tibial plateaus were filled with MSC/β-TCP (n = 16) or with β-TCP only (n = 23). Enrichment efficiency and effect of enrichment on cell viability were evaluated. Clinical results were assessed by imaging examination and Lysholm score. Results: SECCS effectively integrated MSCs with β-TCP. At 18 months postimplantation, new bone ratio was significantly higher in patients treated with MSC/β-TCP than in those treated with β-TCP only (p = 0.000). Patients with MSC/β-TCP implants had better functional recovery (p = 0.028). Conclusion: MSC/β-TCP prepared by SECCS were effective in the treatment of bone defects in patients with depressed tibial plateau fractures, promoted bone regeneration and improved joint function recovery.

Bone Mesenchymal Stem Cell-Enriched β-Tricalcium Phosphate Scaffold Processed by the Screen-Enrich-Combine Circulating System Promotes Regeneration of Diaphyseal Bone Non-Union

Bone non-union after fracture, considered a therapeutic challenge for orthopedics, always needs a reversion surgery, including autograft transplantation (AGT). However, adverse events related to autograft harvest cannot be ignored. Our group designed a novel system called the bone marrow stem cell Screen-Enrich-Combine Circulating System (SECCS) by seeding mesenchymal stem cells (MSCs) into β-tricalcium phosphate (β-TCP) during surgery to thereafter rapidly process bioactive bone implantation. In this retrospective case-control study, 30 non-union patients who accepted SECCS therapy and 20 non-union patients who accepted AGT were enrolled. By SECCS therapy, the MSC-enriched β-TCP particles were implanted into the non-union gap. During the enrichment procedure, a significant proportion of MSCs were screened and enriched from bone marrow into porous β-TCP particles, and the cells possessed the capacity for three-line differentiation and were CD90⁺/CD105⁺/CD34^-/CD45^-. Approximately 82.0±10.7% of MSCs were enriched from 60 mL bone marrow without damaging cell viability, and approximately 11,444.0±6,018 MSCs were transplanted per patient. No implant-related infections occurred in any case. After 9 months of follow-up, 27 patients (90%) in the SECCS group acquired clinical union, compared with 18 patients (90%) in the AGT group (clinical union time, P = 0.064), and postoperative radiographic union score at 9 months post-operation was similar between the two groups. In conclusion, the SECCS could concentrate a large proportion of MSCs from bone marrow to acquire enough effective cells for therapy without in vitro cell culture. Bone substitutes processed by SECCS demonstrated encouraging promotion of bone regeneration and showed a satisfactory clinical curative effect for diaphyseal bone non-union, which was non-inferior to AGT.

Preclinical Studies of the Biosafety and Efficacy of Human Bone Marrow Mesenchymal Stem Cells Pre-Seeded into β-TCP Scaffolds after Transplantation

Background: Cell-Based Therapies (CBT) constitute a valid procedure for increasing the quantity and quality of bone in areas with an inadequate bone volume. However, safety and efficacy should be investigated prior to clinical application. The objective of this study was to evaluate the biodistribution, safety and osteogenic capacity of bone marrow-derived human mesenchymal stem cells (hBMMSCs) pre-seeded into β-tricalcium phosphate (TCP) and implanted into NOD/SCID mice at subcutaneous and intramuscular sites. Methods: hBMMSCs were isolated, characterized and then cultured in vitro on a porous β-TCP scaffold. Cell viability and attachment were analyzed and then hBMMSCs seeded constructs were surgically placed at subcutaneous and intramuscular dorsal sites into NOD/SCID mice. Acute and subchronic toxicity, cell biodistribution and efficacy were investigated. Results: There were no deaths or adverse events in treated mice during the 48-hour observation period, and no toxic response was observed in mice. In the 12-week subchronic toxicity study, no mortalities, abnormal behavioral symptoms or clinical signs were observed in the saline control mice or the hBMMSCs/β-TCP groups. Finally, our results showed the bone-forming capacity of hBMMSCs/β-TCP since immunohistochemical expression of human osteocalcin was detected from week 7. Conclusions: These results show that transplantation of hBMMSCs/β-TCP in NOD/SCID mice are safe and effective, and might be applied to human bone diseases in future clinical trials.