Canine oral mucosal fibroblasts differentiate into osteoblastic cells in response to BMP-2

Transplantation of Olfactory Stem Cells with Biodegradable Hydrogel Accelerates Facial Nerve Regeneration After Crush Injury

Olfactory mucosa contains neural stem cells, called olfactory stem cells (OSCs), which produce trophic support required for promoting axonal regeneration after nerve injury. However, the local tissue environment can reduce the viability/function of transplanted cells when placed directly on the injury. Although gelatin hydrogels have been shown to aid cell survival during transplantation, such OSC‐hydrogel combinations have not been extensively tested, particularly during recovery from facial nerve palsy. In this study, OSCs were isolated from the olfactory mucosae of newborn mice and were shown to express neural stem cell markers before differentiation, as well as cell‐type specific markers after differentiation, confirming their multipotency. The OSCs also secrete growth factors and various cytokines that promote nerve regeneration. To test the effects of OSC transplantation in vivo, Medgel, a biodegradable hydrogel sponge, was applied to retain OSCs around the injury site and to lessen the detrimental effects of the local environment in an established facial nerve palsy mouse model. When OSCs were transplanted into the injury site, accelerated recovery was observed for 1 week. When OSCs were transplanted with Medgel, a higher level and duration of accelerated recovery was observed. OSCs in Medgel also increased peripheral nerve function and increased the number of regenerated nerve fibers. These results suggest that OSCs implanted with Medgel accelerate and enhance recovery from facial palsy in mice. Because human OSCs can be easily obtained from olfactory mucosa biopsies with limited risk, this OSC‐Medgel combination is a candidate treatment option for accelerating recovery after facial nerve injury. stem cells translational medicine2019;8:169&10

A Cell-Engineered Small Intestinal Submucosa-Based Bone Mimetic Construct for Bone Regeneration

Extracellular matrix (ECM)-ornamented biomaterials have attracted attention due to their high potential to improve the biofunctionality of original materials. It is thought that ECM with a bone mimetic microenvironment generated by the specific induction of osteoblasts would be more beneficial for bone regeneration than a regular ECM. In this study, we developed an osteogenic and mineralized ECM construct (Os/M-ECM-SIS) under the guidance of osteoblasts on a small intestinal submucosa (SIS) scaffold cotreated with icariin and calcium. The generated Os/M-ECM-SIS scaffolds exhibited similar morphology and inorganic components as natural bone and higher mechanical strength than ECM-SIS. Cell adhesion, proliferation, and differentiation of osteoblasts and fibroblasts were also enhanced in the cells cultured on the Os/M-ECM-SIS scaffolds. The Os/M-ECM-SIS scaffolds even promoted transdifferentiation of fibroblasts with an upregulation of osteogenic differentiation markers. In a calvarial defect model, new bone formation was greatly enhanced in defects implanted with the Os/M-ECM-SIS scaffolds compared with ECM-SIS scaffolds. Further study showed that the Os/M-ECM-SIS scaffolds promoted bone regeneration in vitro and in vivo via the Bmp/Smad-signaling pathway. Thus, this work proposes a valuable method for generating a mineralized bone mimetic scaffold with SIS as off-the-shelf bone graft substitute that provides an excellent osteogenic microenvironment, making it suitable for application in bone tissue engineering.

Bushen-Qiangdu-Zhilv decoction inhibits osteogenic differentiation of rat fibroblasts by regulating connexin 43

Bushen-Qiangdu-Zhilv (BQZ) decoction is a traditional Chinese medicinal compound widely used for treating ankylosing spondylitis (AS). However, the mechanisms underlying effects of BQZ remain largely unknown. Osteoblast differentiation of fibroblasts plays an important role in heterotopic ossification (HO) of AS, and connexin 43 (Cx43) is crucially involved in the osteoblast differentiation of fibroblasts. The aim of the present study was to evaluate the effects of BQZ on the osteogenic differentiation of fibroblasts by regulating Cx43. Rat fibroblasts were treated with freeze-dried powder of BQZ, in the presence or absence of recombinant human bone morphogenetic protein-2 (rhBMP-2). MTS assays were performed to examine the inhibitory effects of BQZ on fibroblast proliferation. Western blot assays were conducted to detect the protein expression of core-binding factor alpha 1 (Cbfα1), Cx43 and phosphorylated Cx43 (pCx43). BQZ appeared to inhibit fibroblast proliferation in a dose-dependent manner. Furthermore, the expression of Cbfα1 and Cx43/pCx43 was significantly suppressed by BQZ, with or without rhBMP-2 stimulation. Therefore, the present results indicate that BQZ may exert an anti-AS effect by suppressing the osteogenic differentiation of fibroblasts via Cx43 regulation.

Sphere-Derived Multipotent Progenitor Cells Obtained From Human Oral Mucosa Are Enriched in Neural Crest Cells

: Although isolation of oral mucosal stromal stem cells has been previously reported, complex isolation methods are not suitable for clinical application. The neurosphere culture technique is a convenient method for the isolation of neural stem cells and neural crest stem cells (NCSCs); neurosphere generation is a phenotype of NCSCs. However, the molecular details underlying the isolation and characterization of human oral mucosa stromal cells (OMSCs) by neurosphere culture are not understood. The purpose of the present study was to isolate NCSCs from oral mucosa using the neurosphere technique and to establish effective in vivo bone tissue regeneration methods. Human OMSCs were isolated from excised human oral mucosa; these cells formed spheres in neurosphere culture conditions. Oral mucosa sphere-forming cells (OMSFCs) were characterized by biological analyses of stem cells. Additionally, composites of OMSFCs and multiporous polylactic acid scaffolds were implanted subcutaneously into immunocompromised mice. OMSFCs had the capacity for self-renewal and expressed neural crest-related markers (e.g., nestin, CD44, slug, snail, and MSX1). Furthermore, upregulated expression of neural crest-related genes (EDNRA, Hes1, and Sox9) was observed in OMSFCs, which are thought to contain an enriched population of neural crest-derived cells. The expression pattern of α2-integrin (CD49b) in OMSFCs also differed from that in OMSCs. Finally, OMSFCs were capable of differentiating into neural crest lineages in vitro and generating ectopic bone tissues even in the subcutaneous region. The results of the present study suggest that OMSFCs are an ideal source of cells for the neural crest lineage and hard tissue regeneration.

SIGNIFICANCE

The sphere culture technique is a convenient method for isolating stem cells. However, the isolation and characterization of human oral mucosa stromal cells (OMSCs) using the sphere culture system are not fully understood. The present study describes the isolation of neural crest progenitor cells from oral mucosa using this system. Human OMSCs form spheres that exhibit self-renewal capabilities and multipotency, and are enriched with neural crest-derived cells. These oral mucosa sphere-forming cells can generate ectopic bone tissue in vivo. Therefore, the results of the present study show that the sphere culture system can be applied, without the need for complex isolation techniques, to produce multipotent spheres with the properties of neural crest stem cells. Furthermore, a convenient strategy is demonstrated for the isolation and culture of human OMSCs that could have clinical applications.

Strategies to engineer tendon/ligament-to-bone interface: Biomaterials, cells and growth factors

Integration between tendon/ligament and bone occurs through a specialized tissue interface called enthesis. The complex and heterogeneous structure of the enthesis is essential to ensure smooth mechanical stress transfer between bone and soft tissues. Following injury, the interface is not regenerated, resulting in high rupture recurrence rates. Tissue engineering is a promising strategy for the regeneration of a functional enthesis. However, the complex structural and cellular composition of the native interface makes enthesis tissue engineering particularly challenging. Thus, it is likely that a combination of biomaterials and cells stimulated with appropriate biochemical and mechanical cues will be needed. The objective of this review is to describe the current state-of-the-art, challenges and future directions in the field of enthesis tissue engineering focusing on four key parameters: (1) scaffold and biomaterials, (2) cells, (3) growth factors and (4) mechanical stimuli.

Bone morphogenetic protein-7 enhances bone-tendon integration in a murine in vitro co-culture model

PURPOSE

Bone-tendon healing following anterior cruciate ligament reconstruction is reportedly enhanced by bone morphogenetic protein (BMP)-7. To improve our understanding of the underlying biologic processes, we examined the effects of BMP-7 on region-specific gene expression in vitro.

METHODS

A murine in vitro co-culture model simulating the osteoblast, interface and fibroblast regions was established. The dose- and time-dependent region-specific effects of BMP-7 exposure on gene expression of Alpl, Bglap, Col1a1, Runx2 and Spp1 were analysed by quantitative PCR.

RESULTS

At the osteoblast region, BMP-7 significantly increased Alp, Bglap, Col1a1, and Runx2 expression, while Spp1 expression was suppressed. At the interface region, BMP-7 exposure resulted in a trend towards increased expression rates of Alpl and Col1a1, whereas Bglap (P < 0.001) and Runx2 (P < 0.01) were significantly upregulated without any detectable effect on Spp1 expression. At the fibroblast region, BMP-7 increased Alpl (P < 0.001), Bglap (P < 0.001) and Runx2 (P < 0.001) expression, but no significant effects were seen on Col1a1 or Spp1. Exposure to BMP-7 (100 ng/ml) had its most pronounced biologic impact on day ten.

CONCLUSION

BMP-7 stimulation showed beneficial region-specific effects on bone-tendon healing in vitro, such as enhanced expression of parameters for ossification and fibroblast transdifferentiation, both key processes during successful graft integration.

Bone morphogenetic protein 7 (BMP-7) influences tendon-bone integration in vitro

Introduction

Successful graft ingrowth following reconstruction of the anterior cruciate ligament is governed by complex biological processes at the tendon-bone interface. The aim of this study was to investigate in an in vitro study the effects of bone morphogenetic protein 7 (BMP-7) on tendon-bone integration.

Materials and Methods

To study the biological effects of BMP-7 on the process of tendon-bone-integration, two independent in vitro models were used. The first model involved the mono- and coculture of bovine tendon specimens and primary bovine osteoblasts with and without BMP-7 exposure. The second model comprised the mono- and coculture of primary bovine osteoblasts and fibroblasts. Alkaline phosphatase (ALP), lactate dehydrogenase (LDH), lactate and osteocalcin (OCN) were analyzed by ELISA. Histological analysis and electron microscopy of the tendon specimens were performed.

Results

In both models, positive effects of BMP-7 on ALP enzyme activity were observed (p<0.001). Additionally, similar results were noted for LDH activity and lactate concentration. BMP-7 stimulation led to a significant increase in OCN expression. Whereas the effects of BMP-7 on tendon monoculture peaked during an early phase of the experiment (p<0.001), the cocultures showed a maximal increase during the later stages (p<0.001). The histological analysis showed a stimulating effect of BMP-7 on extracellular matrix formation. Organized ossification zones and calcium carbonate-like structures were only observed in the BMP-stimulated cell cultures.

Discussion

This study showed the positive effects of BMP-7 on the biological process of tendon-bone integration in vitro. Histological signs of improved mineralization were paralleled by increased rates of osteoblast-specific protein levels in primary bovine osteoblasts and fibroblasts.

Conclusion

Our findings indicated a role for BMP-7 as an adjuvant therapeutic agent in the treatment of ligamentous injuries, and they emphasized the importance of the transdifferentiation process of tendinous fibroblasts at the tendon-bone interface.

Evaluation of the cellular origins of heterotopic ossification

Heterotopic ossification (HO), acquired or hereditary, is featured by the formation of bone outside of the normal skeleton. Typical acquired HO is a common, debilitating condition associated with traumatic events. Cardiovascular calcification, an atypical form of acquired HO, is prevalent and associated with high rates of cardiovascular mortality. Hereditary HO syndromes, such as fibrodysplasia ossificans progressiva and progressive osseous heteroplasia, are rare, progressive, life-threatening disorders. The cellular origins of HO remain elusive. Some bona fide contributing cell populations have been found through genetic lineage tracing and other experiments in vivo, and various other candidate populations have been proposed. Nevertheless, because of the difficulties in establishing cellular phenotypes in vivo and other confounding factors, the true identities of these populations are still uncertain. This review critically evaluates the accumulating data in the field. The major focus is on the candidate populations that may give rise to osteochondrogenic lineage cells directly, not the populations that may contribute to HO indirectly. This issue is important not solely because of the clinical implications, but also because it highlights the basic biological processes that govern bone formation.