Multipotent adult progenitor cells on an allograft scaffold facilitate the bone repair process

Calcitonin gene-related peptide-modulated macrophage phenotypic alteration regulates angiogenesis in early bone healing

OBJECTIVES

This study aimed to investigate the effect of calcitonin gene-related peptide (CGRP) on the temporal alteration of macrophage phenotypes and macrophage-regulated angiogenesis duringearlybonehealing and preliminarily elucidate the mechanism.

METHODS

In vivo, the rat mandibular defect models were established with inferior alveolar nerve transection (IANT) or CGRP receptor antagonist injection. Radiographicandhistologic assessments for osteogenesis, angiogenesis, and macrophage phenotypic alteration within bone defects were performed. In vitro, the effect and mechanism of CGRP on macrophage polarization and phenotypic alteration were analyzed. Then the conditioned medium (CM) from CGRP-treated M1 or M2 macrophages was used to culture human umbilical vein endothelial cells (HUVECs), and the CGRP's effect on macrophage-regulated angiogenesis was detected.

RESULTS

Comparable changes following IANT and CGRP blockade within bone defects were observed, including the suppression of early osteogenesis and angiogenesis, the prolonged M1 macrophage infiltration and the prohibited transition toward M2 macrophages around vascular endothelium. In vitro experiments showed that CGRP promoted M2 macrophage polarization while upregulating the expression of interleukin 6 (IL-6), a major cytokine that facilitates the transition from M1 to M2-dominant stage, in M1 macrophages via the activation of Yes-associated protein 1. Moreover, CGRP-treated macrophage-CM showed an anabolic effect on HUVECs angiogenesis compared with macrophage-CM and might prevail over the direct effect of CGRP on HUVECs.

CONCLUSIONS

Collectively, our results reveal the effect of CGRP on M1 to M2 macrophage phenotypic alteration possibly via upregulating IL-6 in M1 macrophages, and demonstrate the macrophage-regulated pro-angiogenic potential of CGRP in early bone healing.

Lateral lumbar interbody fusion using a cellular allogeneic bone matrix in the treatment of symptomatic degenerative lumbar disc disease and lumbar spinal instability

Background

Cellular allogeneic bone grafts are used as a biologic adjuvant in lumbar spinal fusions. The clinical use of a minimally invasive extreme lateral approach to the lumbar spine has been widely adopted; however, there are few clinical studies that have documented the clinical and radiographic outcomes associated with the use of cellular allografts as an adjunct to fusion in this advanced surgical approach.

Methods

A consecutive series of 67 patients (34 males and 33 females) with a mean age of 66.8 years (26-85 years) who underwent single- or multilevel lateral lumbar interbody fusion (LLIF) with supplemental posterior segmental spinal fixation using a cellular allogeneic bone matrix as the only bone graft material was retrospectively reviewed by a single surgeon. Patients' preoperative and 3- and 12-month postoperative data were studied. All patients were followed for a minimum of 12 months. Standardized clinical outcome measures-36-Item Short Form Surgery (SF-36), Oswestry Disability Index (ODI), and visual analog scale (VAS) back and leg pain scores-were used to evaluate the clinical outcomes. An average of 2.25 levels was treated per patient (151 total levels). Fusion status was assessed by dynamic radiographs and computed tomography (CT) scans. The statistical method used to identify the significance of the observed changes in clinical outcomes was the paired 2-sided t-tests. Significance was ascribed to P values <0.05.

Results

Fusion was achieved at 142 levels (142/151; 94%). Eight levels (8/151; 5.3%) showed partial fusions and one patient (single level) had no fusion. In the group of patients with fusions, the mean back and leg pain scores showed improvement from preoperative scores at both 3 and 12 months (P<0.001). Functional outcomes showed similar clinical success in both in SF-36 and ODI scores.

Conclusions

The use of a cellular allogeneic bone matrix provided osteoconductive and osteoinductive components for successful spine fusions and was associated with statistically significant improvement in SF-36, VAS, and ODI scores.

A novel gelatin/chitooligosaccharide/demineralized bone matrix composite scaffold and periosteum-derived mesenchymal stem cells for bone tissue engineering

Background

A novel biodegradable scaffold including gelatin (G), chitooligosaccharide (COS), and demineralized bone matrix (DBM) could play a significant part in bone tissue engineering. The present study aimed to investigate the biological characteristics of composite scaffolds in combination of G, COS, and DBM for in vitro cell culture and in vivo animal bioassays.

Methods

Three-dimensional scaffolds from the mixture of G, COS, and DBM were fabricated into 3 groups, namely, G, GC, and GCD using a lyophilization technique. The scaffolds were cultured with mesenchymal stem cells (MSCs) for 4 weeks to determine biological responses such as cell attachment and cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition, cell morphology, and cell surface elemental composition. For the in vivo bioassay, G, GC, and GCD, acellular scaffolds were implanted subcutaneously in 8-week-old male Wistar rats for 4 weeks and 8 weeks. The explants were assessed for new bone formation using hematoxylin and eosin (H&E) staining and von Kossa staining.

Results

The MSCs could attach and proliferate on all three groups of scaffolds. Interestingly, the ALP activity of MSCs reached the greatest value on day 7 after cultured on the scaffolds, whereas the calcium assay displayed the highest level of calcium in MSCs on day 28. Furthermore, weight percentages of calcium and phosphorus on the surface of MSCs after cultivation on the GCD scaffolds increased when compared to those on other scaffolds. The scanning electron microscopy images showed that MSCs attached and proliferated on the scaffold surface thoroughly over the cultivation time. Mineral crystal aggregation was evident in GC and greatly in GCD scaffolds. H&E staining illustrated that G, GC, and GCD scaffolds displayed osteoid after 4 weeks of implantation and von Kossa staining confirmed the mineralization at 8 weeks in G, GC, and GCD scaffolds.

Conclusion

The MSCs cultured in GCD scaffolds revealed greater osteogenic differentiation than those cultured in G and GC scaffolds. Additionally, the G, GC, and GCD scaffolds could promote in vivo ectopic bone formation in rat model. The GCD scaffolds exhibited maximum osteoinductive capability compared with others and may be potentially used for bone regeneration.

Existing clinical evidence on the use of cellular bone matrix grafts in spinal fusion: updated systematic review of the literature

OBJECTIVE

Spinal fusion surgery is increasingly common; however, pseudarthrosis remains a common complication affecting as much as 15% of some patient populations. Currently, no clear consensus on the best bone graft materials to use exists. Recent advances have led to the development of cell-infused cellular bone matrices (CBMs), which contain living components such as mesenchymal stem cells (MSCs). Relatively few clinical outcome studies on the use of these grafts exist, although the number of such studies has increased in the last 5 years. In this study, the authors aimed to summarize and critically evaluate the existing clinical evidence on commercially available CBMs in spinal fusion and reported clinical outcomes.

METHODS

The authors performed a systematic search of the MEDLINE and PubMed electronic databases for peer-reviewed, English-language original articles (1970-2020) in which the articles' authors studied the clinical outcomes of CBMs in spinal fusion. The US National Library of Medicine electronic clinical trials database (www.ClinicalTrials.gov) was also searched for relevant ongoing clinical trials.

RESULTS

Twelve published studies of 6 different CBM products met inclusion criteria: 5 studies of Osteocel Plus/Osteocel (n = 354 unique patients), 3 of Trinity Evolution (n = 114), 2 of ViviGen (n = 171), 1 of map3 (n = 41), and 1 of VIA Graft (n = 75). All studies reported high radiographic fusion success rates (range 87%-100%) using these CBMs. However, this literature was overwhelmingly limited to single-center, noncomparative studies. Seven studies disclosed industry funding or conflicts of interest (COIs). There are 4 known trials of ViviGen (3 trials) and Bio4 (1 trial) that are ongoing.

CONCLUSIONS

CBMs are a promising technology with the potential of improving outcome after spinal fusion. However, while the number of studies conducted in humans has tripled since 2014, there is still insufficient evidence in the literature to recommend for or against CBMs relative to cheaper alternative materials. Comparative, multicenter trials and outcome registries free from industry COIs are indicated.

Bone Cells Differentiation: How CFTR Mutations May Rule the Game of Stem Cells Commitment?

Cystic fibrosis (CF)-related bone disease has emerged as a significant comorbidity of CF and is characterized by decreased bone formation and increased bone resorption. Both osteoblast and osteoclast differentiations are impacted by cystic fibrosis transmembrane conductance regulator (CFTR) mutations. The defect of CFTR chloride channel or the loss of CFTRs ability to interact with other proteins affect several signaling pathways involved in stem cell differentiation and the commitment of these cells toward bone lineages. Specifically, TGF-, nuclear factor-kappa B (NF-B), PI3K/AKT, and MAPK/ERK signaling are disturbed by CFTR mutations, thus perturbing stem cell differentiation. High inflammation in patients changes myeloid lineage secretion, affecting both myeloid and mesenchymal differentiation. In osteoblast, Wnt signaling is impacted, resulting in consequences for both bone formation and resorption. Finally, CFTR could also have a direct role in osteoclasts resorptive function. In this review, we summarize the existing literature on the role of CFTR mutations on the commitment of induced pluripotent stem cells to bone cells.

Multipotent adult progenitor cells grown under xenobiotic-free conditions support vascularization during wound healing

Background

Cell therapy has been evaluated pre-clinically and clinically as a means to improve wound vascularization and healing. While translation of this approach to clinical practice ideally requires the availability of clinical grade xenobiotic-free cell preparations, studies proving the pre-clinical efficacy of the latter are mostly lacking. Here, the potential of xenobiotic-free human multipotent adult progenitor cell (XF-hMAPC®) preparations to promote vascularization was evaluated.

Methods

The potential of XF-hMAPC cells to support blood vessel formation was first scored in an in vivo Matrigel assay in mice. Next, a dose-response study was performed with XF-hMAPC cells in which they were tested for their ability to support vascularization and (epi) dermal healing in a physiologically relevant splinted wound mouse model.

Results

XF-hMAPC cells supported blood vessel formation in Matrigel by promoting the formation of mature (smooth muscle cell-coated) vessels. Furthermore, XF-hMAPC cells dose-dependently improved wound vascularization associated with increasing wound closure and re-epithelialization, granulation tissue formation, and dermal collagen organization.

Conclusions

Here, we demonstrated that the administration of clinical-grade XF-hMAPC cells in mice represents an effective approach for improving wound vascularization and healing that is readily applicable for translation in humans.

A Comparison of Phenotypic and Functional Properties of Mesenchymal Stromal Cells and Multipotent Adult Progenitor Cells

Both Multipotent Adult Progenitor Cells and Mesenchymal Stromal Cells are bone-marrow derived, non-haematopoietic adherent cells, that are well-known for having immunomodulatory and pro-angiogenic properties, whilst being relatively non-immunogenic. However, they are phenotypically and functionally distinct cell types, which has implications for their efficacy in different settings. In this review we compare the phenotypic and functional properties of these two cell types, to help in determining which would be the superior cell type for different applications.

Effect of different-sizes of hydroxyapatite on the water resistance of magnesium oxychloride cement for bone repair

Magnesium oxychloride cement (MOC) has recently attracted significant attention due to its excellent mechanical properties and biological behavior.

Alginate encapsulated multipotent adult progenitor cells promote corneal stromal cell activation via release of soluble factors

To reduce the increasing need for corneal transplantation, attempts are currently aiming to restore corneal clarity, one potent source of cells are multipotent adult progenitor cells (MAPC^®). These cells release a powerful cocktail of paracrine factors that can guide wound healing and tissue regeneration. However, their role in corneal regeneration has been overlooked. Thus, we sought to explore the potential of combining the cytoprotective storage feature of alginate, with MAPC to generate a storable cell-laden gel for corneal wound healing. 72 hours following hypothermic storage, alginate encapsulation was shown to maintain MAPC viability at either 4 or 15°C. Encapsulated MAPC (2 x10⁶ cells/mL) stored at 15°C presented the optimum temperature that allowed for cell recovery. These cells had the ability to reattach to tissue culture plastic whilst exhibiting normal phenotype and this was maintained in serum-free and xenobiotic-free medium. Furthermore, corneal stromal cells presented a significant decrease in scratch-wounds in the presence of alginate encapsulated MAPC compared to a no-cell control (p = 0.018). This study shows that immobilization of MAPC within an alginate hydrogel does not hinder their ability to affect a secondary cell population via soluble factors and that these effects are successfully retained following hypothermic storage.

Multi-functional nano-adhesive releasing therapeutic ions for MMP-deactivation and remineralization

Restoration of hard tissue in conjunction with adhesive is a globally challenging issue in medicine and dentistry. Common clinical therapies involving application of adhesive and substitute material for functional or anatomical recovery are still suboptimal. Biomaterials with bioactivity and inhibitory effects of enzyme-mediated adhesive degradation can render a solution to this. Here, we designed a novel copper-doped bioactive glass nanoparticles (CuBGn) to offer multifunction: metalloproteinases (MMP) deactivation and remineralization and incorporated the CuBGn in resin-dentin adhesive systems, which showed most common failure of MMP mediated adhesive degradation among hard tissue adhesives, to evaluate proposed therapeutic effects. A sol-gel derived bioactive glass nanoparticles doping 10 wt% of Cu (Cu-BGn) for releasing Cu ions, which were well-known MMP deactivator, were successfully created and included in light-curing dental adhesive (DA), a filler-free co-monomer resin blend, at different concentrations (up to 2 wt%). These therapeutic adhesives (CuBGn-DA) showed enhanced (a)cellular bioactivity, cytocompatibility, microtensile bond strength and MMP deactivation-ability. In conclusion, the incorporation of Cu ions releasing nano-bioactive glass demonstrated multifunctional properties at the resin-dentin interface; MMP deactivation and remineralization, representing a suitable strategy to extend the longevity of adhesive-hard tissue (i.e. resin-dentin) interfaces.

GLP2 Promotes Directed Differentiation from Osteosarcoma Cells to Osteoblasts and Inhibits Growth of Osteosarcoma Cells

Glucagon-like peptide 2 (GLP2) is a proglucagon-derived peptide that is involved in the regulation of energy absorption and exerts beneficial effects on glucose metabolism. However, the exact mechanisms underlying the GLP2 during osteogenic differentiation has not been illustrated. Herein, we indicated that GLP2 was demonstrated to result in positive action during the osteogenic differentiation of human osteosarcoma cells. Our findings demonstrate that GLP2 inhibis the growth of osteosarcoma cells in vivo and in vitro. Mechanistic investigations reveal GLP2 inhibits the expression and activity of nuclear factor κB (NF-κB), triggering the decrease of c-Myc, PKM2, and CyclinD1 in osteosarcoma cells. In particular, rescued NF-κB abrogates the functions of GLP2 in osteosarcoma cells. Strikingly, GLP2 overexpression significantly increased the expression of osteogenesis-associated genes (e.g., Ocn and PICP) dependent on c-Fos-BMP signaling, which promotes directed differentiation from osteosarcoma cells to osteoblasts with higher alkaline phosphatase activity. Taken together, our results suggested that GLP2 could be a valuable drug to promote directed differentiation from osteosarcoma cells to osteoblasts, which may provide potential therapeutic targets for the treatment of osteosarcoma.

A comparison of radiographic and clinical outcomes of anterior lumbar interbody fusion performed with either a cellular bone allograft containing multipotent adult progenitor cells or recombinant human bone morphogenetic protein-2

Background

Both the map3 Cellular Allogeneic Bone Graft® and recombinant human bone morphogenetic protein 2 (rhBMP-2, Infuse®) were developed to provide an alternative to iliac crest autograft, thus eliminating the morbidity associated with its harvest. The recent literature concerning adverse events associated with the use of rhBMP-2, however, highlights the need for a safe and effective alternative. The multipotent adult progenitor cells (MAPC) found in map3 allograft may provide this alternative. The purpose of this study is to report 1-year outcomes of patients treated via anterior lumbar interbody fusion (ALIF) using either map3 Cellular Allogeneic Bone Graft or rhBMP-2 for bony fusion.

Methods

This was a retrospective evaluation of 41 patients treated via ALIF with either map3 or rhBMP-2 in a polyetheretherketone cage with posterior stabilization at 1, 2, or 3 consecutive levels (L3-S1). Patients were equally divided between treatment groups. The Oswestry Disability Index (ODI) and visual analog scores (VAS) for pain were documented as part of the standard of care. An independent radiologist assessed bridging of bone, disc height, and lordosis. Primary outcome measures included radiographic analysis of fusion by plain film and CTs. Secondary clinical outcomes included visual analogue scale for neck and arm pain and low back disability index scores.

Results

The overall fusion rate was 91%, with no significant difference between groups. Improvements in ODI and VAS were observed among all patients (p < 0.001), with no significant difference between groups for ODI (p = 0.966) or VAS (p = 0.251). There was no significant difference in terms of changes to disc height and lordosis between groups (p < 0.05). The rhBMP-2 group had increased post-operative complications when compared to the map3 group, but the low numbers precluded statistical analysis.

Conclusion

Improvements in radiographic and clinical findings were observed in both treatment groups one-year postoperatively. Map3 allograft demonstrated equivalent fusion rates to rhBMP-2. A review of surgical supply costs at the treatment facility favored map3 allograft for the treatment of patients with DDD undergoing an ALIF in 1–3 levels compared to rhBMP-2. Further studies to evaluate long-term outcomes and post-operative complications are required.

Preferential Lineage-Specific Differentiation of Osteoblast-Derived Induced Pluripotent Stem Cells into Osteoprogenitors

While induced pluripotent stem cells (iPSCs) hold great clinical promise, one hurdle that remains is the existence of a parental germ-layer memory in reprogrammed cells leading to preferential differentiation fates. While it is problematic for generating cells vastly different from the reprogrammed cells' origins, it could be advantageous for the reliable generation of germ-layer specific cell types for future therapeutic use. Here we use human osteoblast-derived iPSCs (hOB-iPSCs) to generate induced osteoprogenitors (iOPs). Osteoblasts were successfully reprogrammed and demonstrated by endogenous upregulation of Oct4, Sox2, Nanog, TRA-1-81, TRA-16-1, SSEA3, and confirmatory hPSC Scorecard Algorithmic Assessment. The hOB-iPSCs formed embryoid bodies with cells of ectoderm and mesoderm but have low capacity to form endodermal cells. Differentiation into osteoprogenitors occurred within only 2-6 days, with a population doubling rate of less than 24 hrs; however, hOB-iPSC derived osteoprogenitors were only able to form osteogenic and chondrogenic cells but not adipogenic cells. Consistent with this, hOB-iOPs were found to have higher methylation of PPARγ but similar levels of methylation on the RUNX2 promoter. These data demonstrate that iPSCs can be generated from human osteoblasts, but variant methylation patterns affect their differentiation capacities. Therefore, epigenetic memory can be exploited for efficient generation of clinically relevant quantities of osteoprogenitor cells.

Evaluation of the osteoconductive potential of poly(propylene carbonate)/nano-hydroxyapatite composites mimicking the osteogenic niche for bone augmentation

Nano-hydroxyapatite (n-HA) reinforced poly(propylene carbonate) (PPC) composites were prepared for bone repair and reconstruction. The effects of reinforcement on the morphology, mechanical properties and biological performance of n-HA/PPC composites were investigated. The surface morphology and mechanical properties of the composites were characterized by scanning electron microscopy (SEM) and universal material testing machine. The analytical data showed that good incorporation and dispersion of n-HA crystals could be obtained in the PPC matrix at a 30:70 weight ratio. With the increase of n-HA content, the tensile strength increased and the fracture elongation rate decreased. In vitro cell culture revealed that the composite was favorable template for cell attachment and growth. In vivo implantation in femoral condyle defects of rabbits confirmed that the n-HA/PPC composite had good biocompatibility and gradual biodegradability, exhibiting good performance in guided bone regeneration. The results demonstrates that the incorporation of n-HA crystals into PPC matrix provides a practical way to produce biodegradable and cost-competitive composites mimicking the osteogenic niche for bone augmentation.