Effects of rhBMP-2 on Bone Formation Capacity of Rat Dental Stem/Progenitor Cells from Dental Follicle and Alveolar Bone Marrow

Effect of Insulin on Bone Formation Ability of Rat Alveolar Bone Marrow Mesenchymal Stem Cells

The alveolar bone marrow mesenchymal stem cells (ABM-MSCs) play an important role in oral bone healing and regeneration. Insulin is considered to improve impaired oral bones due to local factors, systemic factors and pathological conditions. However, the effect of insulin on bone formation ability of ABM-MSCs still needs to be elucidated. The aim of this study was to determine the responsiveness of rat ABM-MSCs to insulin and to explore the underlying mechanism. We found that insulin promoted ABM-MSCs proliferation in a concentration-dependent manner, in which 10-6 M insulin exerted the most significant effect. 10-6 M insulin significantly promoted the type I collagen (COL-1) synthesis, alkaline phosphatase (ALP) activity, osteocalcin (OCN) expression, and mineralized matrix formation in ABM-MSCs, significantly enhanced the gene and protein expressions of intracellular COL-1, ALP, and OCN. Acute insulin stimulation significantly promoted insulin receptor (IR) phosphorylation, IR substrate-1 (IRS-1) protein expression, and mammalian target of rapamycin (mTOR) phosphorylation, but chronic insulin stimulation decreased these values, while inhibitor NT219 could attenuate these responses. When seeded on β-tricalcium phosphate (β-TCP), ABM-MSCs adhered and grew well, during the 28-day culture period, ABM-MSCs+β-TCP +10-6 M insulin group showed significantly higher extracellular total COL-1 amino-terminus prolongation peptide content, ALP activity, OCN secretion, and Ca and P concentration. When implanted subcutaneously in severe combined immunodeficient mice for 1 month, the ABM-MSCs+β-TCP +10-6 M insulin group obtained the most bone formation and blood vessels. These results showed that insulin promoted the proliferation and osteogenic differentiation of ABM-MSCs in vitro, and enhance osteogenesis and angiogenesis of ABM-MSCs in vivo. Inhibition studies demonstrated that the insulin-induced osteogenic differentiation of ABM-MSCs was dependent of insulin/mTOR signaling. It suggests that insulin has a direct anabolic effect on ABM-MSCs.

A pilot study: Nano-hydroxyapatite-PEG/PLA containing low dose rhBMP2 stimulates proliferation and osteogenic differentiation of human bone marrow derived mesenchymal stem cells

Background

Bone morphogenetic protein 2 (BMP2) can enhance posterolateral spinal fusion (PLSF). The minimum effective dose that may stimulate mesenchymal stem cells however remains unknown. Nano-hydroxyapatite (nHAp) polyethylene glycol (PEG)/polylactic acid (PLA) was combined with recombinant human BMP2 (rhBMP2). We in vitro evaluated proliferation, differentiation, and osteogenic genes of human bone marrow mesenchymal stem cells with 0.5, 1.0, and 3.0 μg/mL rhBMP2 doses in this study.

Methods

In vitro experimental study was designed to proliferation by a real-time quantitative cell analysis system and the osteogenic differentiation by alkaline phosphatase (ALP) activity and osteogenic marker (Runx2, OPN, and OCN) gene expressions of human derived bone marrow mesenchymal stem cells (hBMMSCs). nHAp was produced by wet chemical process and characterized by Fourier transform infrared spectrophotometer, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. PEG/PLA polymer was produced at a 51:49 molar ratio. 0.5, 1.0, and 3.0 μg/mL rhBMP2 and nHAp was combined with the polymers. hBMMSCs were characterized by multipotency assays and surface markers were assessed by flow cytometer. The hBMMSC-rhBMP2 containing nHAp-PEG/PLA composite interaction was evaluated by transmission electron microscopy. Proliferative effect was evaluated by real-time proliferation analysis, and osteogenic capacity was evaluated by ALP activity assay and qPCR.

Results

hBMMSC proliferation in the 0.5 μg/mL rhBMP2 + nHAp-PEG/PLA and the 1.0 μg/mL rhBMP2 + nHAp-PEG/PLA groups were higher compared to control. 1.0 μg/mL rhBMP2 + nHAp-PEG/PLA and 3.0 μg/mL rhBMP2 + nHAp-PEG/PLA containing composites induced ALP activity on days 3 and 10. 0.5 μg/mL rhBMP2 + nHAp-PEG/PLA application stimulated Runx2 and OPN gene expressions.

Conclusion

rhBMP2 + nHAp-PEG/PLA composites stimulate hBMMSC proliferation and differentiation. The nHAp-PEG/PLA composite with low dose of rhBMP2 may enhance bone formation in future clinical PLSF applications.

Spontaneous spheroids from alveolar bone-derived mesenchymal stromal cells maintain pluripotency of stem cells by regulating hypoxia-inducible factors

BACKGROUND

Spontaneous spheroid culture is a novel three-dimensional (3D) culture strategy for the rapid and efficient selection of progenitor cells. The objectives of this study are to investigate the pluripotency and differentiation capability of spontaneous spheroids from alveolar bone-derived mesenchymal stromal cells (AB-MSCs); compare the advantages of spontaneous spheroids to those of mechanical spheroids; and explore the mechanisms of stemness enhancement during spheroid formation from two-dimensional (2D) cultured cells.

METHODS

AB-MSCs were isolated from the alveolar bones of C57BL/6 J mice. Spontaneous spheroids formed in low-adherence specific culture plates. The stemness, proliferation, and multi-differentiation capacities of spheroids and monolayer cultures were investigated by reverse transcription quantitative polymerase chain reaction (RT-qPCR), immunofluorescence, alkaline phosphatase (ALP) activity, and oil-red O staining. The pluripotency difference between the spontaneous and mechanical spheroids was analyzed using RT-qPCR. Hypoxia-inducible factor (HIFs) inhibition experiments were performed to explore the mechanisms of stemness maintenance in AB-MSC spheroids.

RESULTS

AB-MSCs successfully formed spontaneous spheroids after 24 h. AB-MSC spheroids were positive for MSC markers and pluripotency markers (Oct4, KLF4, Sox2, and cMyc). Spheroids showed higher Ki67 expression and lower Caspase3 expression at 24 h. Under the corresponding conditions, the spheroids were successfully differentiated into osteogenic and adipogenic lineages. AB-MSC spheroids can induce neural-like cells after neurogenic differentiation. Higher expression of osteogenic markers, adipogenic markers, and neurogenic markers (NF-M, NeuN, and GFAP) was found in spheroids than in the monolayer. Spontaneous spheroids exhibited higher stemness than mechanical spheroids did. HIF-1α and HIF-2α were remarkably upregulated in spheroids. After HIF-1/2α-specific inhibition, spheroid formation was significantly reduced. Moreover, the expression of the pluripotency genes was suppressed.

CONCLUSIONS

Spontaneous spheroids from AB-MSCs enhance stemness and pluripotency. HIF-1/2α plays an important role in the stemness regulation of spheroids. AB-MSC spheroids exhibit excellent multi-differentiation capability, which may be a potent therapy for craniomaxillofacial tissue regeneration.

Nano-Hydroxyapatite Composite Scaffolds Loaded with Bioactive Factors and Drugs for Bone Tissue Engineering

Nano-hydroxyapatite (n-HAp) is similar to human bone mineral in structure and biochemistry and is, therefore, widely used as bone biomaterial and a drug carrier. Further, n-HAp composite scaffolds have a great potential role in bone regeneration. Loading bioactive factors and drugs onto n-HAp composites has emerged as a promising strategy for bone defect repair in bone tissue engineering. With local delivery of bioactive agents and drugs, biological materials may be provided with the biological activity they lack to improve bone regeneration. This review summarizes classification of n-HAp composites, application of n-HAp composite scaffolds loaded with bioactive factors and drugs in bone tissue engineering and the drug loading methods of n-HAp composite scaffolds, and the research direction of n-HAp composite scaffolds in the future is prospected.

A Molecular View on Biomaterials and Dental Stem Cells Interactions: Literature Review

Biomaterials and stem cells are essential components in the field of regenerative medicine. Various biomaterials have been designed that have appropriate biochemical and biophysical characteristics to mimic the microenvironment of an extracellular matrix. Dental stem cells (DT-MSCs) represent a novel source for the development of autologous therapies due to their easy availability. Although research on biomaterials and DT-MSCs has progressed, there are still challenges in the characteristics of biomaterials and the molecular mechanisms involved in regulating the behavior of DT-MSCs. In this review, the characteristics of biomaterials are summarized, and their classification according to their source, bioactivity, and different biological effects on the expansion and differentiation of DT-MSCs is summarized. Finally, advances in research on the interaction of biomaterials and the molecular components involved (mechanosensors and mechanotransduction) in DT-MSCs during their proliferation and differentiation are analyzed. Understanding the molecular dynamics of DT-MSCs and biomaterials can contribute to research in regenerative medicine and the development of autologous stem cell therapies.

Modification of implant surfaces to stimulate mesenchymal cell activation

BACKGROUND

The process of osteointegration, as key point has the activation of mesenchymal cells at implant-bone interspace, their differentiation into osteoblasts and connection between the implant surface and the surrounding bone.

MAIN TEXT

Implant surfaces composed by biocompatible, organism-friendly materials require changes in content and surface morphology; changes that may further stimulate mesenchymal cell activation. The way the implant surfaces are affected with advantages and disadvantages, that typically bring each methodology, is also the purpose of this study. The study is of review type, based on finding articles about implant surface modification, with the aim of promoting the mesenchymal cell activation, utilizing keyword combination.

CONCLUSIONS

Implant success beyond the human element of the practicioner and the protocol element of implant treatment, also relies on the application of the right type of implant, at the right implant site, in accordance with oral and individual health status of the patient. Implant success does not depend on type of "coating" material of the implants. Based at this physiological process, the success or implant failure is not a process depending on the type of selected implant, because types of synthetic or natural materials that promote osteointegration are relatively in large number.

Elements of 3D Bioprinting in Periodontal Regeneration: Frontiers and Prospects

Periodontitis is a chronic infectious disease worldwide, caused by the accumulation of bacterial plaque, which can lead to the destruction of periodontal supporting tissue and eventually tooth loss. The goal of periodontal treatment is to remove pathogenic factors and control the periodontal inflammation. However, the complete regeneration of periodontal supporting tissue is still a major challenge according to current technology. Tissue engineering recovers the injured tissue through seed cells, bio-capable scaffold and bioactive factors. Three-D-bioprinting is an emerging technology in regeneration medicine/tissue engineering, because of its high accuracy and high efficiency, providing a new strategy for periodontal regeneration. This article represents the materials of 3D bioprinting in periodontal regeneration from three aspects: oral seed cell, bio-scaffold and bio-active factors.

Microenvironment Influences on Human Umbilical Cord Mesenchymal Stem Cell-Based Bone Regeneration

The microenvironment, or niche, regulates stem cell fate and improves differentiation efficiency. Human umbilical cord mesenchymal stem cells (hUC-MSCs) are ideal cell source for bone tissue engineering. However, the role of the microenvironments in hUC-MSC-based bone regeneration is not yet fully understood. This study is aimed at investigating the effects of the in vitro culture microenvironment (hUC-MSCs, nano-hydroxyapatite/collagen/poly (L-lactide) (nHAC/PLA), osteogenic media (OMD), and recombinant human bone morphogenetic protein-7 (rhBMP-7)) and the in vivo transplanted microenvironment (ectopic and orthotopic) on bone regeneration ability of hUC-MSCs. The isolated hUC-MSCs showed self-renewal potential and MSCs' characteristics. In the in vitro two-dimensional culture microenvironment, OMD or OMD with rhBMP-7 significantly enhanced hUC-MSCs' osteocalcin immunofluorescence staining, alkaline phosphatase, and Alizarin red staining; OMD with rhBMP-7 exhibited the highest ALP secretion and mineralized matrix formation. In the in vitro three-dimensional culture microenvironment, nHAC/PLA supported hUC-MSCs' adhesion, proliferation, and differentiation; the microenvironment containing OMD or OMD and rhBMP-7 shortened cell proliferation progression and made osteogenic differentiation progression advance; rhBMP-7 significantly attenuated the inhibiting effect of OMD on hUC-MSCs' proliferation and significantly enhanced the promoting effect of OMD on gene expression and protein secretion of osteogenic differentiation markers, calcium and phosphorous concentration, and mineralized matrix formation. The in vitro three-dimensional culture microenvironment containing OMD and rhBMP-7 induced hUC-MSCs to form the most new bones in ectopic or orthotopic microenvironment as proved by microcomputed tomography and hematoxylin and eosin staining, but bone formation in orthotopic microenvironment was significantly higher than that in ectopic microenvironment. The results indicated that the combination of in vitro hUC-MSCs+nHAC/PLA+OMD+rhBMP-7 microenvironment and in vivo orthotopic microenvironment provided a more optimized niche for bone regeneration of hUC-MSCs. This study elucidates that hUC-MSCs and their local microenvironment, or niche, play an important role in hUC-MSC-based bone regeneration. The endogenously produced BMP may serve an important regulatory role in the process.