Tissue-engineered bone formation in vivo for artificial laminae of the vertebral arch using β-tricalcium phosphate bioceramics seeded with mesenchymal stem cells

Physiologic Osseous Remodeling of the Anterior Wall of the Spinal Canal after Anterior Cervical Corpectomy and Fusion: A Retrospective Observational Study

BACKGROUND

 Anterior cervical corpectomy and fusion (ACCF) has been widely used in the treatment of cervical spondylotic myelopathy (CSM), ossification of posterior longitudinal ligament (OPLL), cervical trauma, and other cervical diseases, but few studies have reported the osseous and physiologic remodeling of the anterior wall of the spinal canal following ACCF. In this study, we analyze that remodeling process and its influence on titanium mesh cage (TMC) subsidence.

METHODS

 We performed a clinical and radiologic analysis of consecutive patients treated with ACCF. Growth rates (GRs) reflecting the extent of remodeling of the remnants of the resected vertebral bodies were measured. We compared the computed tomography (CT) scans taken immediately and at least 1 year after surgery, and a literature review was conducted.

RESULTS

 In all, 48 patients underwent ACCF at a mean age of 61.5 ± 12.0 years. The median follow-up was 36 months, and 159 CT images were analyzed. The GR values of the remnants of the vertebral bodies on CT images immediately and 1 year after surgery were 0.505 ± 0.077 and 0.650 ± 0.022 (p < 0.001), respectively, and the GR value at ≥4 years was 1. Axial CT scans showed that remodeling starts from the lateral remnants of the resected vertebral bodies, finally reaching the center. When fusion of the vertebral bodies and the titanium cage was complete during the first year after ACCF, osteogenesis and remodeling were initiated in the osseous anterior wall of the spinal canal. The remodeling of the osseous anterior wall of the spinal canal was completed at the fourth year after surgery, without recompressing the spinal cord, as seen on both axial and lateral CT scans. According to the literature review, there was no TMC subsidence at more than 4 years after surgery.

CONCLUSION

 The anterior wall of the spinal canal undergoes osseous remodeling after ACCF. The process is complete in the fourth year after surgery and prevents TMC subsidence.

Artificial lamina after laminectomy: Progress, applications, and future perspectives

In clinical practice, laminectomy is a commonly used procedure for spinal decompression in patients suffering from spinal disorders such as ossification of ligamentum flavum, lumbar stenosis, severe spinal fracture, and intraspinal tumors. However, the loss of posterior column bony support, the extensive proliferation of fibroblasts and scar formation after laminectomy, and other complications (such as postoperative epidural fibrosis and iatrogenic instability) may cause new symptoms requiring revision surgery. Implantation of an artificial lamina prosthesis is one of the most important methods to avoid post-laminectomy complications. Artificial lamina is a type of synthetic lamina tissue made of various materials and shapes designed to replace the resected autologous lamina. Artificial laminae can provide a barrier between the dural sac and posterior soft tissues to prevent postoperative epidural fibrosis and paravertebral muscle compression and provide mechanical support to maintain spinal alignment. In this paper, we briefly review the complications of laminectomy and the necessity of artificial lamina, then we review various artificial laminae from clinical practice and laboratory research perspectives. Based on a combination of additive manufacturing technology and finite element analysis for spine surgery, we propose a new designing perspective of artificial lamina for potential use in clinical practice.

Wnt/β-Catenin Pathway Balances Scaffold Degradation and Bone Formation in Tissue-Engineered Laminae

Tissue engineering provides a promising way for the regeneration of artificial vertebral laminae. Previous studies have confirmed the feasibility of reconstructing vertebral laminae via hydroxyapatite-collagen I scaffolds and mesenchymal stromal cells. However, there were no studies exploring the degradation of hydroxyapatite-collagen I scaffolds and the function of Wnt/β-catenin pathway in the process. In this study, tissue-engineered laminae (TEL) were constructed by nanohydroxyapatite/collagen I scaffolds and umbilical cord Wharton's Jelly mesenchymal stromal cells (WJ-MSCs). Cell attachment was observed by scanning electron microscopy, and cell viability was confirmed by Live/Dead staining. The rat models were randomly divided into control and β-catenin inhibition groups. Vertebral lamina defect rat models were made on the fifth lumbar vertebrate, and TEL was implanted into the defect site. After 14 weeks, the newborn laminae were harvested for microcomputed tomography, histology, or transcriptional profile analysis. We found that, for the control group, the newborn lamina formation matched with the scaffold degradation and complete newborn laminae formed at the 14th week; for the β-catenin inhibition group, the scaffold degradation rate overrated the lamina formation and no complete artificial laminae were formed at the 14th week. In addition, the osteoclastic genes, such as Cathepsin K or RANKL, in the control groups were significantly lower than the β-catenin inhibition group, and the antiosteoclastic gene, OPG, in the control group was significantly higher than the β-catenin inhibition group. In conclusion, inhibition of Wnt/β-catenin pathway led to speedy scaffold degradation and deferred artificial lamina formation. Wnt/β-catenin pathway played a critical role in maintaining the balance between scaffold degradation and bone formation in the process of vertebral lamina reconstruction.

Cerebrospinal Fluid Pulsation Stress Promotes the Angiogenesis of Tissue-Engineered Laminae

Background

Angiogenesis is a prerequisite step to achieve the success of bone regeneration by tissue engineering technology. Previous studies have shown the role of cerebrospinal fluid pulsation (CSFP) stress in the reconstruction of tissue-engineered laminae. In this study, we investigated the role of CSFP stress in the angiogenesis of tissue-engineered laminae.

Methods

For the in vitro study, a CSFP bioreactor was used to investigate the impact of CSFP stress on the osteogenic mesenchymal stem cells (MSCs). For the in vivo study, forty-eight New Zealand rabbits were randomly divided into the CSFP group and the Non-CSFP group. Tissue-engineered laminae (TEL) was made by hydroxyapatite-collagen I scaffold and osteogenic MSCs and then implanted into the lamina defect in the two groups. The angiogenic and osteogenic abilities of newborn laminae were examined with histological staining, qRT-PCR, and radiological analysis.

Results

The in vitro study showed that CSFP stress could promote the vascular endothelial growth factor A (VEGF-A) expression levels of osteogenic MSCs. In the animal study, the expression levels of angiogenic markers in the CSFP group were higher than those in the Non-CSFP group; moreover, in the CSFP group, their expression levels on the dura mater surface, which are closer to the CSFP stress stimulation, were also higher than those on the paraspinal muscle surface. The expression levels of osteogenic markers in the CSFP group were also higher than those in the Non-CSFP group.

Conclusion

CSFP stress could promote the angiogenic ability of osteogenic MSCs and thus promote the angiogenesis of tissue-engineered laminae. The pretreatment of osteogenic MSC with a CSFP bioreactor may have important implications for vertebral lamina reconstruction with a tissue engineering technique.

Green propolis extract promotes in vitro proliferation, differentiation, and migration of bone marrow stromal cells

BACKGROUND

Propolis is a resinous material extracted from bee glue with a complex chemical composition. The unique biological properties of propolis have led to its use in alternative medicine and as a nutritional supplement. Recent research shows that propolis could affect the immune system by decreasing the production of inflammatory cytokines and potentiating an effect on resident stem cells. The exact mechanism, however, is unknown. The goal of this study was to demonstrate whether green propolis extract affects any characteristic properties of mesenchymal stromal cells (MSCs)in vitro.

METHODS

The cytocompatibility of propolis extract and the proliferation of bone marrow mesenchymal stromal cells (BMMSCs) in the presence of propolis was evaluated by live/dead cell staining and MTS viability assay over a period of 3 days. Also, we evaluated the effect of propolis extract on trilineage differentiation and migration capacity of undifferentiated and differentiated BMMSCs.

RESULTS

Relative to the control, propolis extract resulted in a significant and linear increase in the proliferation of MSCs and inhibited the osteogenic differentiation of BMMSCs, while there was a potentiation of chondrogenesis and adipogenesis. Finally, in relevance to wound healing, an in vitro scratch assay demonstrated that the migratory potential of differentiated BMMSCs was enhanced in the presence of propolis.

CONCLUSION

We have demonstrated that propolis extract was not toxic to BMMSCs (<400 μg/ml), supported their proliferation, potentiated chondrogenic and adipogenic differentiation processes, and supported cell migrationin vitro. Most interestingly, there was a down-regulation of osteogenesis. These data support the use of propolis extract for enhanced cell proliferation and tissue regeneration; however, it warrants further investigation.

Stem Cell and Advanced Nano Bioceramic Interactions

Bioceramics are type of biomaterials generally used for orthopaedic applications due to their similar structure with bone. Especially regarding to their osteoinductivity and osteoconductivity, they are used as biodegradable scaffolds for bone regeneration along with mesenchymal stem cells. Since chemical properties of bioceramics are important for regeneration of tissue, physical properties are also important for cell proliferation. In this respect, several different manufacturing methods are used for manufacturing nano scale bioceramics. These nano scale bioceramics are used for regeneration of bone and cartilage both alone or with other types of biomaterials. They can also act as carrier for the delivery of drugs in musculoskeletal infections without causing any systemic toxicity.

Ultrastructural characteristics of ovine bone marrow-derived mesenchymal stromal cells cultured with a silicon stabilized tricalcium phosphate bioceramic

Bioceramics are being used in experimental bone engineering application in association with bone marrow derived mesenchymal stem cells (BM-MSCs) as a new therapeutic tool, but their effects on the ultrastructure of BM-MSCs are yet unknown. In this study we report the morphological features of ovine (o)BM-MSCs cultured with Skelite, a resorbable bioceramic based on silicon stabilized tricalcium phosphate (SiTCP), able to promote the repair of induced bone defect in sheep model. oBM-MSCs were isolated from the iliac crest, cultured until they reached near-confluence and incubated with SiTCP. After 48 hr the monolayers were highly damaged and only few cells adhered to the plastic. Thus, SiTCP was removed, and after washing the cells were cultured until they became confluent. Then, they were trypsinizated and processed for transmission electron microscopy (TEM) and RT-PCR analysis. RT-PCR displayed that oBM-MSCs express typical surface marker for MSCs. TEM revealed the presence of electron-lucent cells and electron-dense cells, both expressing the CD90 surface antigen. The prominent feature of electron-lucent cells was the concentration of cytoplasmic organelles around the nucleus as well as large surface blebs containing glycogen or profiles of endoplasmic reticulum. The dark cells had a multilocular appearance by the presence of peripheral vacuoles. Some dark cells contained endocytic vesicles, lysosomes, and glycogen aggregates. oBM-MSCs showed different types of specialized interconnections. The comparison with ultrastructural features of untreated oBM-MSCs suggests the light and dark cells are two distinct cell types which were differently affected by SiTCP bioceramic. Skelite cultured ovine BM-MSCs display electron-dense and electron-lucent cells which are differently affected by this bioceramic. This suggests that they could play a different role in bioceramic based therapy.

Fabrication of dicalcium phosphate dihydrate-coated β-TCP granules and evaluation of their osteoconductivity using experimental rats

β-Tricalcium phosphate (β-TCP) has attracted much attention as an artificial bone substitute owing to its biocompatibility and osteoconductivity. In this study, osteoconductivity of β-TCP bone substitute was enhanced without using growth factors or cells. Dicalcium phosphate dihydrate (DCPD), which is known to possess the highest solubility among calcium phosphates, was coated on β-TCP granules by exposing their surface with acidic calcium phosphate solution. The amount of coated DCPD was regulated by changing the reaction time between β-TCP granules and acidic calcium phosphate solution. Histomorphometry analysis obtained from histological results revealed that the approximately 10mol% DCPD-coated β-TCP granules showed the largest new bone formation compared to DCPD-free β-TCP granules, approximately 2.5mol% DCPD-coated β-TCP granules, or approximately 27mol% DCPD-coated β-TCP granules after 2 and 4weeks of implantation. Based on this finding, we demonstrate that the osteoconductivity of β-TCP granules could be improved by coating their surface with an appropriate amount of DCPD.

Bone regeneration strategies with bone marrow stromal cells in orthopaedic surgery

Bone is the most transplanted tissue human with 1 million procedures every year in Europe. Surgical interventions for bone repair are required for varied reasons such as trauma resulting non-union fractures, or diseases including osteoporosis or osteonecrosis. Autologous bone grafting is the gold standard in bone regeneration but it requires a second surgery with associated pain and complications, and is also limited by harvested bone quantity. Synthetic bone substitutes lack the osteoinductive properties to heal large bone defects. Cell therapies based on bone marrow or ex vivo expanded mesenchymal stromal stem cells (MSCs) in association with synthetic calcium phosphate (CaP) bone substitutes may be alternatives to autologous bone grafting. This manuscript reviews the different conventional biological and synthetic bone grafting procedures as well as the more recently introduced cell therapy approaches used in orthopaedic surgery for bone regeneration. Some clinical studies have demonstrated safety and efficacy of these approaches but regeneration of large bone defects remain challenging due to the absence of rapid and adequate vascularisation. Future directions in the field of bone regeneration are presented, such as testing alternative cell sources or in situ fabrication of vascularized bone grafts in patients.

A Comparative Evaluation of the Mechanical Properties of Two Calcium Phosphate/Collagen Composite Materials and Their Osteogenic Effects on Adipose-Derived Stem Cells

Adipose-derived stem cells (ADSCs) are ideal seed cells for use in bone tissue engineering and they have many advantages over other stem cells. In this study, two kinds of calcium phosphate/collagen composite scaffolds were prepared and their effects on the proliferation and osteogenic differentiation of ADSCs were investigated. The hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) composite scaffolds (HTPSs), which have an additional β-tricalcium phosphate, resulted in better proliferation of ADSCs and showed osteogenesis-promoting effects. Therefore, such composite scaffolds, in combination with ADSCs or on their own, would be promising for use in bone regeneration and potential clinical therapy for bone defects.

Ectopic osteogenesis and scaffold biodegradation of nano-hydroxyapatite-chitosan in a rat model

The bone-formation and scaffold-biodegradation processes have not been fully characterized. This study aimed to determine the osteogenic ability of nHA-CS osteo-induced bone marrow mesenchymal stem cell (BMSC) composites and to explore the relationship between bone formation and scaffold biodegradation. The nHA-CS osteo-induced BMSC composites (nHA-CS+cells group) and the nHA-CS scaffolds (nHA-CS group) were implanted into the femoral spatium intermusculare of SD rats. At 2, 4, 6, 8, and 12 weeks post-implantation, the rat femurs were scanned using computerized tomography (CT), and the CT values of the implants were measured and comparatively analyzed. The implants were then harvested and subjected to hematoxylin and eosin (HE) and Masson's trichrome staining, and the percentages of bone area, scaffold area and collagen area were compared between the two groups. The CT values of the implants were higher in the nHA-CS+cells group than the nHA-CS group at the same time points (P < 0.05). Histological analysis revealed that de novo bone and collagen formation in the pores of the scaffolds gradually increased from 2 weeks post-implantation in both groups and that the scaffold gradually degraded as bone formation proceeded. However, more de novo bone and collagen formation and scaffold degradation occurred in the nHA-CS+cells group than in the nHA-CS group at the same time points (P < 0.05). In conclusion, nHA-CS osteo-induced BMSC composites are promising bone tissue engineering substitutes, and osteo-induced BMSCs can significantly enhance the osteogenic ability and play an active role in the degradation of nHA-CS scaffolds on par with bone formation.

Mesenchymal stem cells in regenerative medicine for musculoskeletal diseases: bench, bedside, and industry

Human bone marrow-derived mesenchymal stem cells (MSCs) can self-renew and differentiate into osteoblasts, chondrocytes, and adipocytes. MSCs have effectively emerged as a promising tool for clinical applications, specifically in musculoskeletal diseases. This article reviews the status of preclinical animal studies, clinical trials, and the efforts of the industry in using MSCs to treat musculoskeletal diseases such as bone fractures, bone defects, focal chondral lesions, osteoarthritis, spinal diseases, and tendon injuries. We also discuss the current problems encountered and potential of using MSCs in future clinical studies.