In vivo osteogenic capability of cultured allogeneic bone in porous hydroxyapatite: immunosuppressive and osteogenic potential of FK506 in vivo

Local FK506 delivery induces osteogenesis in in vivo rat bone defect and rabbit spine fusion models

Bone grafting procedures are commonly used for the repair, regeneration, and fusion of bones in in a wide range of orthopaedic surgeries, including large bone defects and spine fusion procedures. Autografts are the clinical gold standard, though recombinant human bone morphogenetic proteins (rhBMPs) are often used, particularly in difficult clinical situations. However, treatment with rhBMPs can have off-target effects and significantly increase surgical costs, adding to patients' already high economic and mental burden. Recent studies have identified that FDA-approved immunosuppressant drug, FK506 (Tacrolimus), can also activate the BMP pathway by binding to its inhibitors. This study tested the hypothesis that FK506, as a standalone treatment, could induce osteogenic differentiation of human mesenchymal stromal cells (hMSCs), as well as functional bone formation in a rat segmental bone defect model and rabbit spinal fusion model. FK506 potentiated the effect of low dose BMP-2 to enhance osteogenic differentiation and mineralization of hMSCs in vitro. Standalone treatment with FK506 delivered on a collagen sponge, produced consistent bone bridging of a rat critically-sized femoral defect with functional mechanical properties comparable to naïve bone. In a rabbit single level posterolateral spine fusion model, treatment with FK506 delivered on a collagen sponge successfully fused the L5-L6 vertebrae at rates comparable to rhBMP-2 treatment. These data demonstrate the ability of FK506 to induce bone formation in human cells and two challenging in vivo models, and indicate FK506 can be utilized either as a standalone treatment or in conjunction with rhBMP to treat a variety of spine disorders.

Efficacy of Nano Composite Porous 3D Scaffold of Crab Shell and Al-Kharit Histological and Radiological for Bone Repair in Vivo

The present study was conducted to evaluate the effect of scaffold fabricated from Nano crab shell and Al-kharit (Papyrus Vaccine) for enhancing the healing of the experimentally induced bone defect in dogs. For this purpose, twenty healthy adult mongrel dogs were used in this study which divided randomly into two equal groups, under general anesthesia, 1 cm bone gap was created in the distal part of the tibia, that fixed by bone plate and screws. Nano crab shell scaffold was implanted. All experimental animals showed normal situation without any infection at the site of operation, while the radiography showed a periosteal and endosteal reaction. Moreover, the gaps were bridged faster in the treated group as compared with the control group. Treated animals showed new bone formation which represented by obvious lamellar bone, haversian canal and osteocyte cells in 90 days. In conclusion, the Nano crab shell scaffold gave better acceleration in the bone healing process, also this scaffolds may provide insight into the clinical repair of large bone defects

In vivo evaluation of a novel nanocomposite porous 3D scaffold in a rabbit model: histological analysis

The healing of load-bearing segmental defects in long bones is a challenge due to the complex nature of the weight that affects the bone part and due to bending, shearing, axial, and torsional forces. An innovative porous 3D scaffolds implant of CaCO₃ aragonite nanocomposite derived from cockle shell was advanced for substitute bone solely for load-bearing cases. The biomechanical characteristics of such materials were designed to withstand cortical bone strength. In promoting bone growth to the implant material, an ideal surface permeability was formed by means of freeze drying and by adding copolymers to the materials. The properties of coating and copolymers supplement were also assessed for bone-implant connection resolutions. To examine the properties of the material in advanced biological system, an experimental trial in an animal model was carried out. Critical sized defect of bone was created in rabbit's radial bone to assess the material for a load-bearing application with a short and extended period assessment with histological evaluation of the incorporated implanted material to the bone of the host. Trials in animal models proved that the material has the capability of enduring load-bearing conditions for long-term use devoid of breaking or generating stress that affects the host bone. Histological examination further confirmed the improved integration of the implanted materials to the host bone with profound bone development into and also above the implanted scaffold, which was attained with negligible reaction of the tissues to a foreign implanted material.

MicroRNA expression analysis during FK506-induced osteogenic differentiation in rat bone marrow stromal cells

FK506 (also known as tacrolimus) is a potent immunosuppressive agent that is widely used in the treatment of graft-rejection and autoimmune diseases. FK506 has attracted additional attention owing to its potential role in osteogenic differentiation and bone formation. MicroRNAs (miRNAs) have been demonstrated to serve important roles in the regulation of osteogenic differentiation; however, identification of specific miRNAs and their roles in regulating FK506-induced osteogenic differentiation have been poorly examined. In the present study, osteodifferentiation of rat bone marrow stromal cells (BMSCs) was induced with varying concentrations of FK506 (5–5,000 nM) for 3, 7 and 14 days. Differentially expressed miRNAs were profiled using miRNA array, verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and subjected to gene ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Results from the present study identified a subset of miRNAs that were differentially expressed, of which five upregulated miRNAs (miR-106b-5p, miR-101b-3p, miR-193a-3p, miR-485-3p and miR-142-3p) and four downregulated miRNAs (miR-27a-3p, miR-207, miR-218a-2-3p and let-7a-5p) were confirmed by RT-qPCR. GO and KEGG analysis revealed that the predicted target genes of these miRNAs are involved in multiple biological processes and signaling pathways, including cell differentiation and the mitogen-activated protein kinase (MAPK) signaling pathway. Verification of the miRNA-target genes revealed that Smad5, Jagged 1 and MAPK9 were significantly upregulated, whereas Smad7, BMP and activin membrane-bound inhibitor, and dual-specificity phosphatase 2 were significantly downregulated during FK506-induced osteodifferentiation. The present study may provide an experimental basis for further research on miRNA functions during FK506-induced osteogenic differentiation in rat BMSCs.

Potential differentiation ability of gingiva originated human mesenchymal stem cell in the presence of tacrolimus

The aim of the present study is to evaluate the potential differentiation ability of gingiva originated human mesenchymal stem cell in the presence of tacrolimus. Tacrolimus-loaded poly(lactic-co-glycolic acid) microspheres were prepared using electrospraying technique. In vitro release study of tacrolimus-loaded poly(lactic-co-glycolic acid) microspheres was performed in phosphate-buffered saline (pH 7.4). Gingiva-derived stem cells were isolated and incubated with tacrolimus or tacrolimus-loaded microspheres. Release study of the microspheres revealed prolonged release profiles of tacrolimus without any significant initial burst release. The microsphere itself did not affect the morphology of the mesenchymal stem cells, and cell morphology was retained after incubation with microspheres loaded with tacrolimus at 1 μg/mL to 10 μg/mL. Cultures grown in the presence of microspheres loaded with tacrolimus at 1 μg/mL showed the highest mineralization. Alkaline phosphatase activity increased with an increase in incubation time. The highest expression of pSmad1/5 was achieved in the group receiving tacrolimus 0.1 μg/mL every third day, and the highest expression of osteocalcin was achieved in the group receiving 1 μg/mL every third day. Biodegradable poly(lactic-co-glycolic acid)-based microspheres loaded with tacrolimus promoted mineralization. Microspheres loaded with tacrolimus may be applied for increased osteoblastic differentiation.

Morphological effects of porous poly-d,l-lactic acid/hydroxyapatite scaffolds produced by supercritical CO2 foaming on their mechanical performance

A novel supercritical CO2 foaming technique was used to fabricate scaffolds of controllable morphology and mechanical properties, with the potential to tailor the scaffolds to specific tissue engineering applications. Biodegradable scaffolds are widely used as temporary supportive structures for bone regeneration. The scaffolds must provide a sufficient mechanical support while allowing cell attachment and growth as well as metabolic activities. In this study, supercritical CO2 foaming was used to prepare fully interconnected porous scaffolds of poly-d,l-lactic acid and poly-d,l-lactic acid/hydroxyapatite. The morphological, mechanical and cell behaviours of the scaffolds were measured to examine the effect of hydroxyapatite on these properties. These scaffolds showed an average porosity in the range of 86%–95%, an average pore diameter of 229–347 µm and an average pore interconnection of 103–207 µm. The measured porosity, pore diameter, and interconnection size are suitable for cancellous bone regeneration. Compressive strength and modulus of up to 36.03 ± 5.90 and 37.97 ± 6.84 MPa were measured for the produced porous scaffolds of various compositions. The mechanical properties presented an improvement with the addition of hydroxyapatite to the structure. The relationship between morphological and mechanical properties was investigated. The matrices with different compositions were seeded with bone cells, and all the matrices showed a high cell viability and biocompatibility. The number of cells attached on the matrices slightly increased with the addition of hydroxyapatite indicating that hydroxyapatite improves the biocompatibility and proliferation of the scaffolds. The produced poly-d,l-lactic acid/hydroxyapatite scaffolds in this study showed a potential to be used as bone graft substitutes.

Suppression of the immune system as a critical step for bone formation from allogeneic osteoprogenitors implanted in rats

The surface marker profile of mesenchymal stromal cells (MSCs) suggests that they can escape detection by the immune system of an allogeneic host. This could be an optimal strategy for bone regeneration applications, where off-the-shelf cells could be implanted to heal bone defects. However, it is unknown how pre-differentiation of MSCs to an osteogenic lineage, a means of improving bone formation, affects their immunogenicity. Using immunohistological techniques in a rat ectopic implantation model, we demonstrate that allogeneic osteoprogenitors mount a T cell- and B cell-mediated immune response resulting in an absence of in vivo bone formation. Suppression of the host immune response with daily administration of an immunosuppressant, FK506, is effective in preventing the immune attack on the allogeneic osteoprogenitors. In the immunosuppressed environment, the allogeneic osteoprogenitors are capable of generating bone in amounts similar to those of syngeneic cells. However, using osteoprogenitors from one of the allogeneic donors led to newly deposited bone that was attacked by the host immune system, despite the continued administration of the immunosuppressant. This suggests that, although using an immunosuppressant can potentially suppress the immune attack on the allogeneic cells, optimizing the dose of the immunosuppressant may be crucial to ensure bone formation within the allogeneic environment. Overall, allografts comprising osteoprogenitors derived from allogeneic MSCs have the potential to be used in bone regeneration applications.

The role of small molecules in musculoskeletal regeneration

The uses of bone morphogenetic proteins and parathyroid hormone therapeutics are fraught with several fundamental problems, such as cost, protein stability, immunogenicity, contamination and supraphysiological dosage. These downsides may effectively limit their more universal use. Therefore, there is a clear need for alternative forms of biofactors to obviate the drawbacks of protein-based inductive factors for bone repair and regeneration. Our group has studied small molecules with the capacity to regulate osteoblast differentiation and mineralization because their inherent physical properties minimize limitations observed in protein growth factors. For instance, in general, small molecule inducers are usually more stable, highly soluble, nonimmunogenic, more affordable and require lower dosages. Small molecules with the ability to induce osteoblastic differentiation may represent the next generation of bone regenerative medicine. This review describes efforts to develop small molecule-based biofactors for induction, paying specific attention to their novel roles in bone regeneration.

Studies of bone morphogenetic protein-based surgical repair

Over the past several decades, recombinant human bone morphogenetic proteins (rhBMPs) have been the most extensively studied and widely used osteoinductive agents for clinical bone repair. Since rhBMP-2 and rhBMP-7 were cleared by the U.S. Food and Drug Administration for certain clinical uses, millions of patients worldwide have been treated with rhBMPs for various musculoskeletal disorders. Current clinical applications include treatment of long bone fracture non-unions, spinal surgeries, and oral maxillofacial surgeries. Considering the growing number of recent publications related to clincal research of rhBMPs, there exists enormous promise for these proteins to be used in bone regenerative medicine. The authors take this opportunity to review the rhBMP literature paying specific attention to the current applications of rhBMPs in bone repair and spine surgery. The prospective future of rhBMPs delivered in combination with tissue engineered scaffolds is also reviewed.

Effects of immunosuppressants, FK506 and cyclosporin A, on the osteogenic differentiation of rat mesenchymal stem cells

Purpose

The purpose of this study was to investigate the effects of the immunosuppressants FK506 and cyclosporin A (CsA) on the osteogenic differentiation of rat mesenchymal stem cells (MSCs).

Methods

The effect of FK506 and CsA on rat MSCs was assessed in vitro. The MTT assay was used to determine the deleterious effect of immunosuppressants on stem cell proliferation at 1, 3, and 7 days. Alkaline phosphatase (ALP) activity was analyzed on days 3, 7, and 14. Alizarin red S staining was done on day 21 to check mineralization nodule formation. Real-time polymerase chain reaction (RT-PCR) was also performed to detect the expressions of bone tissue-specific genes on days 1 and 7.

Results

Cell proliferation was promoted more in the FK506 groups than the control or CsA groups on days 3 and 7. The FK506 groups showed increased ALP activity compared to the other groups during the experimental period. The ALP activity of the CsA groups did not differ from the control group in any of the assessments. Mineralization nodule formation was most prominent in the FK506 groups at 21 days. RT-PCR results of the FK506 groups showed that several bone-related genes-osteopontin, osteonectin, and type I collagen (Col-I)-were expressed more than the control in the beginning, but the intensity of expression decreased over time. Runx2 and Dlx5 gene expression were up-regulated on day 7. The effects of 50 nM CsA on osteonectin and Col-I were similar to those of the FK506 groups, but in the 500 nM CsA group, most of the genes were less expressed compared to the control.

Conclusions

These results suggest that FK506 enhances the osteoblastic differentiation of rat MSCs. Therefore, FK506 might have a beneficial effect on bone regeneration when immunosuppressants are needed in xenogenic or allogenic stem cell transplantation to treat bone defects.

In vitro and in vivo evaluation of a biphasic calcium phosphate scaffold coated with a native allogeneic extracellular matrix

This study evaluated the osteogenic properties of biphasic calcium phosphate (BCP) scaffolds coated with extracellular matrix (ECM) derived in vitro from allogeneic mesenchymal stem cells (MSCs). BCP/ECM and plain BCP scaffolds were seeded with MSCs from F344 rats and cultured in osteoinductive medium. At 1, 7, 14 and 21 days post-seeding, assessments were made of cellularity, alkaline phosphatase (ALP) activity and RNA expression of osteocalcin, bone sialoprotein and osteopontin. MSCs seeded on BCP/ECM scaffolds exhibited significantly higher cellularity, ALP activity and transcript levels for the three genes examined. For the in vivo study, BCP/ECM and BCP scaffolds with and without MSCs were implanted subcutaneously into F344 rats. After four weeks of implantation, the extent of new bone formation and tissue response were examined by histology and histomorphometry; histological evidence showed that the seeded cell scaffolds induced new bone formation at the ectopic site and a higher average ratio of bone in the cell-seeded BCP/ECM scaffold group. Results suggest that modification of the BCP scaffold with an in vitro generated allogeneic ECM can effectively enhance osteogenic properties in vitro and in vivo.

The effects of disease modifying anti-rheumatic drugs on osteoclastogenesis and bone destruction in rheumatoid arthritis

Finding the means to ameliorate and prevent bone destruction as well as control inflammation is an urgent issue in the treatment of rheumatoid arthritis (RA). Recently, it has been demonstrated that osteoclastogenesis plays an important role in the bone destruction and pathogenesis of RA. Here, we review the effects of disease modifying anti-rheumatic drugs (DMRAD) on the amelioration of bone destruction and osteoclastogenesis.

BONE INDUCTION BY BMP-2 EXPRESSING ADENOVIRAL VECTOR IN RATS UNDER TREATMENT WITH FK506

The purpose of this study was to investigate the effectiveness of human bone morphogenetic protein-2 (BMP-2) expressing adenoviral vector in vivo. The day before vector injection, immunosuppressant FK506 was given subcutaneously to each rat at doses of 12 mg/kg (Group I), 6 mg/kg (Group II) and 3 mg/kg (Group III). FK506 was not administered to the six rats of the control group. Twenty-five liters of AXCAOBMP-2 (3.93 × 109pfu/ml) were injected into the right calf muscle of all rats. On day 21 after vector injection, all groups were investigated radiologically, histologically, and biochemically. Osteoinduction was seen in the AxCAOBMP-2-injected groups with immunosuppression. However, no bone formation was observed in the control group. These findings suggest that AxCAOBMP-2 has the potential of osteoinduction under transient immunosuppression. AxCAOBMP-2 may be useful for future clinical application in bone reconstruction, if host immunity response can be regulated.

Disc regeneration therapy using marrow mesenchymal cell transplantation: a report of two case studies

STUDY DESIGN

Marrow mesenchymal cells (MSCs) contain stem cells and possess the ability to regenerate bone, cartilage, and fibrous tissues. Here, we applied this regenerative ability to intervertebral disc regeneration therapy in an attempt to develop a new spinal surgery technique.

OBJECTIVE

We analyzed the regenerative restoration ability of autologous MSCs in the markedly degenerated intervertebral discs.

SUMMARY OF BACKGROUND DATA

Fusion for lumbar intervertebral disc instability improves lumbago. However, fused intervertebral discs lack the natural and physiologic functions of intervertebral discs. If intervertebral discs can be regenerated and repaired, then damage to adjacent intervertebral discs can be avoided. We verified the regenerative ability of MSCs by animal studies, and for the first time, performed therapeutic intervertebral disc regeneration therapy in patients and obtained favorable findings.

METHODS

Subjects were 2 women aged 70 and 67 years; both patients had lumbago, leg pain, and numbness. Myelography and magnetic resonance imaging showed lumbar spinal canal stenosis, and radiograph confirmed the vacuum phenomenon with instability. From the ilium of each patient, marrow fluid was collected, and MSCs were cultured using the medium containing autogenous serum. In surgery, fenestration was performed on the stenosed spinal canal and then pieces of collagen sponge containing autologous MSCs were grafted percutaneously to degenerated intervertebral discs.

RESULTS

At 2 years after surgery, radiograph and computed tomography showed improvements in the vacuum phenomenon in both patients. On T2-weighted magnetic resonance imaging, signal intensity of intervertebral discs with cell grafts was high, thus indicating high moisture contents. Roentgenkymography showed that lumbar disc instability improved. Symptom was alleviated in both patients.

CONCLUSION

The intervertebral disc regeneration therapy using MSC brought about favorable results in these 2 cases. It seems to be a promising minimally invasive treatment.

Effects of long-term FK 506 therapy on the alveolar bone and cementum of rats

Cyclosporine (CsA) and tacrolimus (FK 506) exert complex, incompletely understood actions on bone. The objective of the study was to evaluate the effects of long-term tacrolimus therapy on the periodontium. Rats were treated for 60, 120, 180, and 240 days with daily subcutaneous injections of 1 mg/kg body weight of FK 506. After the experimental period, we obtained serum levels of calcium and alkaline phosphatase (ALP). After histological processing, the alveolar bone and cementum, as well as volume densities of bone (V(b)) and osteoclasts (V(o)), were assessed at the regions of the lower first molar. There was a tendency toward a statistically significant decrease in ALP levels with FK 506; however, serum calcium levels increased during the long periods. At 60, 180, and 240 days of treatment with FK 506, we did not observe V(b) and V(o) alterations. At 120 days of treatment, there was an evident decrease in V(b), but it did not show alveolar bone loss. We did not observe any alterations of cementum among rats treated with FK 506. It may be concluded that FK 506 administration did not induce side effects on the periodontium.

A clinically relevant model of osteoinduction: a process requiring calcium phosphate and BMP/Wnt signalling

In this study, we investigated a clinically relevant model of in vivo ectopic bone formation utilizing human periosteum derived cells (HPDCs) seeded in a Collagraft™ carrier and explored the mechanisms by which this process is driven. Bone formation occurred after eight weeks when a minimum of one million HPDCs was loaded on Collagraft™ carriers and implanted subcutaneously in NMRI nu/nu mice. De novo bone matrix, mainly secreted by the HPDCs, was found juxta-proximal of the calcium phosphate (CaP) granules suggesting that CaP may have triggered the ‘osteoinductive program’. Indeed, removal of the CaP granules by ethylenediaminetetraacetic acid decalcification prior to cell seeding and implantation resulted in loss of bone formation. In addition, inhibition of endogenous bone morphogenetic protein and Wnt signalling by overexpression of the secreted antagonists Noggin and Frzb, respectively, also abrogated osteoinduction. Proliferation of the engrafted HPDCs was strongly reduced in the decalcified scaffolds or when seeded with adenovirus-Noggin/Frzb transduced HPDCs indicating that cell division of the engrafted HPDCs is required for the direct bone formation cascade. These data suggest that this model of bone formation is similar to that observed during physiological intramembranous bone development and may be of importance when investigating tissue engineering strategies.

Stimulation of osteogenic activity in mesenchymal stem cells by FK506

The aim of this study was to investigate the osteogenic induction by tacrolimus hydrate (FK506) of rat bone marrow-derived mesenchymal stem cells (MSCs). MSCs were cultured in alpha-MEM containing either (1) L-ascorbic acid-2-phosphate (AsAP) and beta-glycerophosphate (beta-GP) as a control; (2) AsAP and beta-GP plus FK506; (3) AsAP and beta-GP plus Dex; or (4) AsAP and beta-GP plus FK506 and Dex. The concentration of FK506 was varied from 5 to 5000 nM to investigate the dose-effect relationship. Sixteen days later, cells were harvested for analysis. Examination of morphology, alkaline phosphatase (APase) activity, calcium deposition, bone nodule formation, osteocalcin mRNA expression, and mineralized extracellular matrix formation showed that the osteogenic differentiation of MSCs was greatly promoted, bone nodule formation was enhanced, APase activity and the expression of osteocalcin mRNA were increased. FK506 was much more effective when combined with Dex. The best results were achieved with alpha-MEM containing 0.25 mM AsAP, 10 mM beta-GP, 10 nM Dex, and 50 nM FK506. Formation of bone in vivo was also studied by transplanting MSCs-loaded ceramic cubes subcutaneously into the back of rats. Satisfactory results were achieved at 4 and 8 weeks. FK506 should be considered for use as an osteogenic agent.

Wound therapy by marrow mesenchymal cell transplantation

BACKGROUND

Marrow mesenchymal cells are useful in regenerative medicine because they contain stem cells, but there have been few reports of clinical applications. The authors developed a new wound treatment technique by improving marrow mesenchymal cell culture methods and placing cultured cells in an artificial skin material. This new treatment was useful for tissue regeneration in 20 patients with skin wounds.

METHODS

Marrow mesenchymal cells from a 46-year-old man were cultured and placed in artificial dermis made of collagen sponge. This composite graft was implanted subcutaneously into the back of a nude mouse and removed 10 days later; immunohistological analysis confirmed regeneration of subcutaneous tissue using human marrow mesenchymal cells. Next, in 20 patients (nine men and 11 women; average age, 64.8 years; range, 22 to 91 years) with intractable dermatopathies, 10 to 20 ml of bone marrow fluid was aspirated from the ilium and cultured in medium containing either fetal calf or autologous serum. The resulting cultured cells were placed in artificial dermis made of collagen sponge, and this composite graft was used to treat skin wounds.

RESULTS

The wound mostly healed in 18 of the 20 patients; the remaining two patients died of causes unrelated to transplantation. In all patients, autologous marrow mesenchymal cell transplantation was shown to be therapeutically effective.

CONCLUSIONS

In skin regeneration therapy using a marrow mesenchymal cell/artificial dermis composite graft, skin regeneration is possible with bone marrow aspiration, a minimally invasive procedure. Compared with existing skin grafting techniques, the present technique is practical and much less invasive.

Comparative in vitro study of the proliferation and growth of ovine osteoblast-like cells on various alloplastic biomaterials manufactured for augmentation and reconstruction of tissue or bone defects

In this in vitro study ovine osteoblast-like cells were cultured on seven different alloplastic biomaterials used for augmentation and for reconstruction of bone defects in dental and craniomaxillofacial surgery. The aim of this study was to examine the growth behaviour (viability, cell density and morphology) of ovine osteoblast-like cells on the investigated biomaterials to get knowledge which biomaterial is qualified to act as a cell carrier system in further in vivo experiments. The biomaterials were either synthetically manufactured or of natural origin. As synthetically manufactured biomaterials Ethisorb, MakroSorb, PalacosR, and PDS film were used. As biomaterials of natural origin BeriplastP, Bio-Oss and Titanmesh were investigated. The cell proliferation and cell colonization were analyzed by a proliferation assay and scanning electron microscopy. Osteoblast-like cells proliferated and attached on all biomaterials, except on Beriplast. On Ethisorb the highest cell proliferation rate was measured followed by PalacosR. Both biomaterials offer suitable growth and proliferation conditions for ovine osteoblast-like cells. The proliferation rates of Bio-Oss, MakroSorb, PDS-film and Titanmesh were low and SEM examinations of these materials showed less spread osteoblast-like cells. The results showed that ovine osteoblast-like cells appear to be sensitive to substrate composition and topography. This in vitro study provides the basis for further in vivo studies using the sheep model to examine the biocompatibility and the long-term interaction between the test material and tissue (bone regeneration).

Rapamycin as an inhibitor of osteogenic differentiation in bone marrow-derived mesenchymal stem cells

BACKGROUND

An autograft of cultured bone marrow-derived mesenchymal stem cells has already been used in clinical practice. In those patients whose bone marrow cannot be used, a cell allograft with the use of immunosuppressant drugs will be an option in the future. However, little is known about the effects of immunosuppressant drugs on mesenchymal stem cells. This study assessed the effects of immunosuppressant drugs on osteogenic differentiation of mesenchymal stem cells and analyzed the manner in which immunosuppressant drugs modulate the osteogenic effect of dexamethasone.

METHODS

Rat bone marrow cells were cultured with or without dexamethasone as an osteogenic supplement. In each experimental group, one of three immunosuppressants (rapamycin, cyclosporine A, or FK506) was added. As a control, cells were cultured without immunosuppressants. Histologically, mineralization was assessed by alizarin red S staining and phase-contrast microscopy. Biochemically, alkaline phosphatase activity, calcium content, and osteocalcin content were assessed.

RESULTS

On histological analysis, no mineralized nodules were seen on alizarin red S staining or phase-contrast microscopy in the groups not treated with dexamethasone, except in the group that was treated with FK506. Mineralized nodules were seen in the groups treated with dexamethasone, except in the group that was treated with rapamycin. On biochemical analysis, it was found that, compared to the control group, rapamycin reduced alkaline phosphatase activity and the calcium content of mesenchymal stem cells; FK506 increased alkaline phosphatase activity, calcium content, and osteocalcin content; and cyclosporine A had negligible effects. Dexamethasone increased alkaline phosphatase activity, calcium content, and osteocalcin content, but these effects were decreased by rapamycin.

CONCLUSIONS

Rapamycin did not have an osteogenic effect on mesenchymal stem cells, but inhibited the effect of osteogenic differentiation induced by dexamethasone. In contrast, FK506 had an osteogenic effect on mesenchymal stem cells. Therefore, FK506 might be more useful than rapamycin in allogeneic transplantation of mesenchymal stem cells.

Effects of tacrolimus, cyclosporin A and sirolimus on MG63 cells

The reduction in bone mineral density after organ transplantation results in increased morbidity (post-transplantation bone disease) and remains an unsolved problem. A connection with the long-term application of nonglucocorticoidal immunosuppressants is the subject of controversial discussion. We hypothesized that such substances have an influence on the skeletal system on the cellular level by modulating osteoblast differentiation. Therefore, we investigated the effects of tacrolimus, cyclosporin A and sirolimus as representative substances of nonglucocorticoidal immunosuppressants on cell proliferation and expression of bone tissue-specific genes of human osteoblasts (MG63). None of the examined substances affected cell proliferation, but all influenced the gene expression pattern towards change in cell differentiation. In detail, collagen III and XII, matrix metalloproteinase 2, SMAD2, epithelial growth factor receptor, annexin V and osteonectin expression were increased by all of the examined substances. Tacrolimus, cyclosporin A and sirolimus influence intracellular signalling pathways, transmembranous receptors and bone-specific matrix synthesis. They do not have antiproliferative or toxic effects. We postulate that the shown changes of osteoblast differentiation cause post-transplantation disease.

Posterolateral Lumbar Fusion by Tissue Engineered Bone

Posterolumbar fusion, which involves placing a bone graft in the posterolateral portion of the spine, has been applied to patients with lumbar instability due to structural defects or regressive degeneration. However, harvesting cancellous bone from the ilium is associated with severe postoperative pain, and patients experience more pain at the harvest site than at the graft site, thus resulting in poor patient satisfaction. If a tissue engineering approach was used to produce autogenous bone ex vivo with culture techniques, spinal fusion could be performed without damaging normal tissues. In all patients, 10 to 20 mL of bone marrow fluid was collected from the ilium and cultured in MEM containing autologous serum or fetal bovine serum and an antibiotic. After two weeks in primary culture, the marrow mesenchymal cells were seeded onto porous beta-TCP block, and tissue engineered bone were fabricated as we reported previously. Decompressive laminectomy and posterolateral lumbar fusion with use of the tissue engineered bone thus obtained were then done. In all patients, the implanted artificial bone survived and bone regeneration was detected radiographically, and the clinical symptoms were improved. Short term follow-up has shown that the bone implants were effective in all of the patients. There were no adverse reactions related to implantation. The use of this tissue engineered bone makes it possible to perform osteogenetic treatment without harvesting autogenous bone, thus avoiding pain and pelvic deformity at the site of bone collection and reducing the burden on the patient.

Osteogenic potential of cultured bone/ceramic construct: comparison with marrow mesenchymal cell/ceramic composite

Osteogenesis occurs in porous hydroxyapatite (HA) when porous HA blocks combined with marrow mesenchymal cells are grafted in vivo. In vitro bone formation occurs in HA pores when HA combined with marrow cells is cultured in osteogenic medium containing dexamethasone. This cultured bone/HA construct possesses higher osteogenic ability when it is grafted in vivo. In the present study, we compared the osteogenic potential of a cultured bone/HA construct with that of a marrow mesenchymal cell/HA composite. Marrow cells were obtained from the femoral bone shaft of 7-week-old, male Fischer 344 rats and were cultured in T-75 flasks. Cells were concentrated, then frozen and stored in liquid nitrogen for 6 months. The cryopreserved cells were then thawed and prepared for subculture in porous HA (5 x 5 x 5 mm, Interpore 500) and for implantation with porous HA. After 2 weeks of subculture, three cultured bone/HA constructs were separately implanted in the right side of the back of each syngeneic 7-week-old male Fischer rat, and three thawed cell/HA composites (without subculture) were separately implanted in the left side. These implants were harvested at 2 or 4 weeks postimplantation, and prepared for histological, biochemical, and genetic analysis. Alkaline phosphatase activity and osteocalcin content of cultured bone/HA constructs were much higher than those of the cell/HA composites at 2 and 4 weeks postimplantation. Histological examination and gene expression data agreed with these findings. The culture technique discussed herein should facilitate the development of biosynthetic bone implants with higher osteogenic capacity.

Comparaison des effets de la ciclosporine-A et du tacrolimus sur le métabolisme osseux des patients transplantés rénaux : une étude transversale chez 28 patients

BACKGROUND

Controversy exists about the effects of calcineurin inhibitors on bone metabolism. We decided to compare the effects of CyA vs FK506 on bone metabolism of kidney recipients.

PATIENTS AND METHODS

From 94 patients grafted at the University Hospital of Nice between 1996 and 1999 treated either by CyA (N=49) or by FK506 (N=45), we selected 14 pairs (18 M, 10F), matched for gender, BMI, time lapsed since transplantation and gonadal status in females. Patients with>1 transplantation or>1 rejection episode were excluded. Cumulative dose of steroids was recorded. Bone mineral density (BMD) was mesured at heel and forearm, as well as serum concentration of calcium, phosphate, parathyroid hormone (PTH), vitamin D metabolites, C-telopeptide (CTX), creatinine, estradiol as well as Bone Alkaline Phosphatase (BAP) activity.

RESULTS

Despite the matching, time on hemodialysis was longer in FK506 group. Cumulative dose of steroids was similar between groups. There was no difference between groups in BMD and biochemical parameters except for estradiol serum levels which were dramatically lower in FK506 than in CsA (P=0,02) and for a trend (p=0,08) for BAP and CTX to be higher in FK506 than in CsA.

CONCLUSIONS

BMD is not lower in FK506- than in CsA-treated patients although exposure to hyperparathyroidism was longer and estradiol levels were lower in the FK506 than in the CsA group. These data suggest that FK506 may have a favorable bone effect to compensate for these deleterious factors. This hypothesis remains to be tested in longitudinal studies.

Treatment of Pseudoarthrosis Using Tissue-Engineered Bone Graft

Subjects were graft patients with pseudoarthrosis (average age, 60.3 years; range, 17-85 years). Pseudoarthrosis affected the thoracolumbar spine, the femur, the clavicle, the humerus and the metatarsal. From the ilium (tibia in one patient), 10-20 ml of bone marrow fluid was collected, and then, it was immediately transferred to the culture room and incubated in a flask containing MEM with 15% autologous or fetal bovine serum, etc.. After 2 weeks in primary culture, cells were released by trypsin treatment and were subsequently incubated with porous beta-TCP in order to prepare tissue-engineered artificial bone, according to the previously reported modified culturing technique. Tissue-engineered artificial bone was grafted around the non-union site of each affected long bone, while tissue-engineered artificial bone was grafted via the pedicle of each affected vertebral body. In all patients, favorable bone formation was seen at three months after surgery. In the patients with pseudoarthrosis of the spine, CT and MRI confirmed favorable vertebral body formation. In the patients with pseudoarthrosis of a long bone, the artificial bone was remodeled and favorable bone union was confirmed. In 2 patients in whom bone biopsy was performed during pin removal, bone regeneration was confirmed histologically. With present type of tissue-engineered artificial bone, an artificial material with a high bone regeneration capacity can be prepared by aspiration, which is minimally invasive, and thus when compared to iliac bone grafts, it is possible to radically reduce postoperative pain without damage of autologous bone.

Effect of dexamethasone on moesin gene expression in rabbit bone marrow stromal cells

The influence of dexamethasone on rabbit bone marrow stromal cells differentiation was studied by screening the action of dexamethasone on gene expression. Using differential display, we observed some differential amplifications. The use of five of thirteen different primers combination allowed to identify one or more differential bands. One of them was identified as moesin gene. Real-time PCR confirmed a significant reduction of moesin gene expression following dexamethasone treatment. The decrease of expression for this protein, involved in cytoskeletal organization, could explain the effects of dexamethasone treatment on bone marrow stromal cells differentiation.

In Vitro Bone Formation Induced by Immunosuppressive Agent Tacrolimus Hydrate (FK506)

When rat bone marrow cells were cultured with an immunosuppressive agent, tacrolimus hydrate (FK506), as well as with beta-glycerophosphate and vitamin C, numerous cell clusters became positive for alkaline phosphatase activity. Scanning electron microscopy revealed mineralized bone matrix in the cell clusters, which was identical to that of living bone. High levels of alkaline phosphatase (ALP), indicating osteoblastic activity, and high levels of osteocalcin (Oc) and calcium were found in the mature bone matrix of the cultures. There was significantly increased expression of mRNAs for ALP and Oc. These results indicate that the cultures contained both bone matrix and high osteoblastic activity, suggesting that FK506 induces ossification.

Enhancement of bone volume in guided bone augmentation by cell transplants derived from periosteum: an experimental study in rabbit calvarium bone

Bone morphology is genetically encoded and it is usually difficult to change its structure without invasive surgery. We have tried to stimulate bone augmentation by a combination of guided bone regeneration techniques and cell transplants with collagen scaffolds for the suitable skeletal framework. In vitro-expanded tibia periosteum cells were used to promote osteogenesis with collagen scaffolds and titanium (Ti) or poly-L-lactic acid (PLLA) caps as barriers to create a space facing connective tissue under calvarium skin. This approach was assessed in the defective skull bone of a rabbit model. After a 12-week healing period, histomorphometric analyses were performed to determine the percentage of newly formed mineralized tissue in the cap. The mean percentage of newly formed mineralized tissue within the cap was 15.4%+/-3.99 for the Ti cap group, 15.5%+/-4 for the PLLA cap group, 6.19%+/-4.94 for the PLLA cap+collagen carrier group and 23.1%+/-23.1 for the PLLA+collagen carrier+cell transplants group. The cell transplant group showed a significantly higher value than other groups (P<0.05, Wilcoxon signed rank test, Mann-Whitney U-test). This approach of guided bone augmentation and cultured cell transplants with collagen carrier exhibited significantly greater morphogenesis of mineralized tissue than the control over a 12-week experimental period.

Bone Regeneration by Grafting of Cultured Human Bone

A 3-mL sample of bone marrow was collected from the iliac bones of 27 orthopedic patients (8 men and 19 women with a mean age of 56.1 years [range, 17 to 76 years]), followed by culture in standard culture medium (minimal essential medium containing 15% fetal bovine serum). In all 7 patients randomly selected from these 27 patients, significant in vitro osteogenic ability of marrow mesenchymal cells was demonstrated by scanning electron microscopy and biochemical analyses. In all 27 cases, to investigate the in vivo osteogenic potential of this human cultured bone, porous ceramics were impregnated with marrow cells and subcultured in osteogenic culture medium (standard medium supplemented with sodium beta-glycerophosphate, vitamin C phosphate, and dexamethasone). After 3 weeks of subculture, the cultured artificial bones of the cultured bone/porous ceramics were grafted into the abdominal cavity of nude mice. Histological and biochemical (alkaline phosphatase activity and human osteocalcin) examinations indicated that the cultured artificial bone possessed significant ability to regenerate bone. This result suggests that the bone-regenerating ability of human marrow cells may not depend on age, and that cultured artificial bone may be useful for bone regeneration treatment if appropriate cultured marrow cells can be successfully prepared.

Immunosuppressive and postoperative effects of orthotopic liver transplantation on bone metabolism

Bone loss occurs early after orthotopic liver transplantation (OLT) in all liver transplant recipients and leads to postoperative fractures, especially in cholestatic patients with the lowest bone mass. Little is known about the underlying changes in bone metabolism after OLT or about the etiology of these changes. Histomorphometric analysis of bone biopsies, a method that allows assessment of bone volume, resorption, and formation, has shown improved bone metabolism at 4 months after OLT. It has further suggested that accelerated posttransplant bone loss occurs in the first 1-2 months after OLT, probably by an additional insult to bone formation. This study attempts to correlate the histomorphometric bone changes in paired bone biopsies (OLT and 4 months after OLT) of 33 patients undergoing OLT for chronic cholestatic liver disease with the many clinical and biochemical changes in these patients over the same period. Cumulative steroid dosage early after OLT is shown to be important, presumably by decreasing bone formation rates. The actual effect of calcineurin inhibitors on this early phase of bone loss is less clear, although posttransplant histomorphometric findings suggest that tacrolimus-treated patients have an earlier recovery of bone metabolism and trabecular structure compared with cyclosporine patients. Other factors important in the recovery of bone metabolism after the early phase of bone loss are recovery of liver and gonadal function and better calcium balance.

Osteogenic Differentiation of Human Bone Marrow Stromal Cells on Partially Demineralized Bone Scaffoldsin Vitro

Tissue engineering has been used to enhance the utility of biomaterials for clinical bone repair by the incorporation of an osteogenic cell source into a scaffold followed by the in vitro promotion of osteogenic differentiation before host implantation. In this study, three-dimensional, partially demineralized bone scaffolds were investigated for their ability to support osteogenic differentiation of human bone marrow stromal cells (BMSCs) in vitro. Dynamic cell seeding resulted in homogeneous cell attachment and infiltration within the matrix and produced significantly higher seeding efficiencies when compared with a conventional static seeding method. Dynamically seeded scaffolds were cultured for 7 and 14 days in the presence of dexamethasone and evaluated on biochemical, molecular, and morphological levels for osteogenic differentiation. Significant elevation in alkaline phosphatase activity was observed versus controls over the 14-day culture, with a transient peak indicative of early mineralization on day 7. On the basis of RT-PCR, dexamethasone-treated samples showed elevations in alkaline phosphatase and osteocalcin expression levels at 7 and 14 days over nontreated controls, while bone sialoprotein was produced only in the presence of dexamethasone at 14 days. Scanning electron microscopy evaluation of dexamethasone-treated samples at 14 days revealed primarily cuboidal cells indicative of mature osteoblasts, in contrast to nontreated controls displaying a majority of cells with a fibroblastic cell morphology. These results demonstrate that partially demineralized bone can be successfully used with human BMSCs to support osteogenic differentiation in vitro. This osseous biomaterial may offer new potential benefits as a tool for clinical bone replacement.

Bone regeneration by grafting of an autogenous cultured bone/ceramic construct

The in vivo osteogenic potential of autogenous cultured bone/ceramic constructs in large animals or humans is unknown, and thus we performed a preliminary study of this issue prior to clinical application. All autogenous cultured-bone/ceramic constructs at 3 weeks after implantation in dogs showed obvious histological bone formation within the ceramic pores. In many pores, the HE staining of decalcified specimens revealed thick lamellar bone formation on the pore surface of ceramic. On the surface of bone tissue, numerous active cuboidal osteoblasts were evident. Biochemically, high alkaline phosphatase activity was detected in all dogs. Histological examination of the constructs at 8 weeks postimplantation showed lamellar bone formation with vascular system invasion into the pores, and regenerated hematopoietic bone marrow was often detected in association with the new bone in grafting of human cultured bone/ceramic constructs. Trilineage hematopoietic cells (i.e., granulocytic, erythroblastic, and megakaryocytic cells) were identified in the ceramic pores. Biochemically, high alkaline phosphatase activity and significant human osteocalcin content was detected in the constructs. Based on these findings, in the near future, this technique (grafting of patient-derived cultured bone/HA constructs) will be able to be applied to various bone reconstruction surgical treatments.

Engineered allogeneic mesenchymal stem cells repair femoral segmental defect in rats

Bone marrow derived mesenchymal stem cells (MSC) have been shown to be progenitor cells for mesenchymal tissues. These cells may also provide a potential therapy for bone repair. Our previous studies showed that MSC engineered with the gene for bone morphogenetic protein 2 (BMP-2), a growth factor for bone cells, were capable of differentiating into osteoblast lineage and inducing autologous bone formation in several animal models. Culturing individual MSC for autologous implantation, however, remains problematic. The number of human MSC with osteogenic potential decreases with age, and, in certain diseases, the patient's marrow may be damaged or the healthy cells reduced in number. In this study, we used rats with a femoral segmental defect to investigate whether allogeneic BMP-2 engineered MSC would facilitate bone healing. We show that BMP-2 engineered allogeneic MSC can repair critical bone defects to the same degree as rats treated with BMP-2 engineered autologous MSC, if the allogeneic group receives short-term treatment with immunosuppressant FK506. We also show that allogeneic gene transferred MSC are directly involved in bone repair, in addition to acting as gene deliverers.

Effect of FK506 on osteoinduction by recombinant human bone morphogenetic protein-2

FK506 is an immunosuppressant that is used widely in organ transplantation, and it has recently been recognized as effective for promoting the growth of bone grafts [J. Bone Miner. Res. 15 (2000) 1147]. In this study, we evaluated the influence of FK506 on osteoinduction by recombinant human bone morphogenetic protein-2 (rhBMP-2) using atelopeptide type I collagen as a carrier. We administered FK506 (1 mg/kg/day intramuscularly) on days -2 to 0, -2 to 7, and -2 to sacrifice. rhBMP-2 was implanted into the calf muscle of Wistar rats (thirty per group) and the implant was sampled on days 7, 14, and 21. Radiographic evaluation, histological examination, and biochemical analysis were performed. It was found that FK506 promoted the early stage of osteoinduction after short-term administration. However, long-term administration of this agent accelerated both bone formation and bone resorption. In order to use FK506 effectively for promoting bone growth, we must further examine the appropriate dose, method, and period of administration.

Preparation of macroporous calcium phosphate cement tissue engineering scaffold

Unlike sintered hydroxyapatite there is evidence to suggest that calcium phosphate cement (CPC) is actively remodelled in vivo and because CPC is formed by a low-temperature process, thermally unstable compounds such as proteins may be incorporated into the matrix of the cement which can then be released after implantation. The efficacy of a macroporous CPC as a bone tissue engineering scaffold has been reported; however, there have been few previous studies on the effect of macroporosity on the mechanical properties of the CPC. This study reports a novel method for the formation of macroporous CPC scaffolds, which has two main advantages over the previously reported manufacturing route: the cement matrix is considerably denser than CPC formed from slurry systems and the scaffold is formed at temperatures below room temperature. A mixture of frozen sodium phosphate solution particles and CPC powder were compacted at 106 MPa and the sodium phosphate was allowed to melt and simultaneously set the cement. The effect of the amount of porogen used during processing on the porosity, pore size distribution and compressive strength of the scaffold was investigated. It was found that macroporous CPC could reliably be fabricated using cement:ice ratios as low as 5:2.

In vitro behavior of albumin-loaded carbonate hydroxyapatite gel

Hydroxyapatite (HA) powder, porous HA, plasma-sprayed HA, apatite cements, and sintered HA have all been investigated as delivery systems for compounds such as human growth hormone and vancomycin. However, many previous studies showed that the period of release was limited to 2-3 weeks. The concept of using a nanoporous matrix as a means of immobilizing proteins is well known but has largely been confined to silica-based systems. Carbonate hydroxyapatite (CHA) is more soluble in vivo than HA, and when formed as an aqueous precipitate, it is often formed as nanocrystals. This study investigated the release profiles of ovine albumin (OVA) from CHA gel stored in phosphate-buffered saline (PBS) and double distilled water (DDW) for times of up to 1 year. It was found that 7.9% OVA could be loaded onto apatitic gels by means of a purely aqueous process. This process provided a simple low-temperature method of protein adsorption on a high surface area apatitic matrix at physiological pH. The rate of short-term release of OVA was lower from CHA gels than from microcrystalline HA powder. However, the period of release from the CHA gel was short term and may have been associated with recrystallization of the gel. OVA loaded into CHA gel was found to remain undegraded in vitro at 37 degrees C for periods of up to 1 year.

Recombinant human bone morphogenetic protein-2 promotes osteogenesis within atelopeptide type I collagen solution by combination with rat cultured marrow cells

We evaluated the combination effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) and cultured rat bone marrow mesenchymal stem cells (MSCs) in atelopeptide type I collagen (AC) solution on osteogenesis in a diffusion chamber (DC) to develop a bone substitute having consistent osteogenic capability for clinical applications. The cultured MSCs were obtained by 10-day primary culture of fresh bone marrow cells of Fischer rats. We prepared three groups of DCs: AC solution with rhBMP-2, AC solution with cultured MSCs, and AC solution with rhBMP-2 and cultured MSCs. The prepared combined solutions were injected into DCs, which were subcutaneously implanted into the backs of syngeneic rats. DCs were harvested after 2, 4, or 8 weeks and analyzed for bone-forming capability by determining histological and osteoblastic biochemical markers. De novo bone formation was observed both inside and outside of the membrane filter of DCs in the group of AC solution with rhBMP-2 and cultured MSCs. The alkaline phosphatase activity and osteocalcin content in the group of AC solution with rhBMP-2 and cultured MSCs were significantly higher than those in the group of AC solution with cultured MSCs at any time. These findings indicate that AC aqueous solution is a useful material not only as a carrier of rhBMP-2 but also as a cell-anchorage for differentiation and proliferation of MSCs. Therefore, this study suggests that clinical repairs of bone defects are feasible using injectable AC solution with rhBMP-2 and cultured MSCs as a bone substitute.

FK506 induces chondrogenic differentiation of clonal mouse embryonic carcinoma cells, ATDC5

FK506 (Tacrolimus) and cyclosporin A exert their immunosuppressive effects via a common mechanism, calcineurin inhibition, after binding to intracellular proteins termed immunophilins: FK506-binding protein (FKBP) and cyclophilin. In this study, FK506 was found to induce chondrogenic differentiation of ATDC5 cells (clonal mouse embryonal carcinoma cells) in a concentration-dependent manner (0.1-1000 ng/ml). Immunohistochemical staining showed that ATDC5 cells induced to differentiate by FK506 produced proteoglycan and type II collagen, main components of the extracellular matrix of cartilage. Rapamycin, an immunosuppressant that binds to FKBP, antagonized the effect of FK506. Cyclosporin A did not induce chondrogenesis at concentrations up to 1000 ng/ml. Taken together, these results suggest that FK506 induces chondrogenic differentiation of ATDC5 cells via a calcineurin-independent mechanism, after binding to FKBP.