Effect of the Bone Morphogenetic Protein-2 Doses on the Osteogenic Potential of Human Multipotent Stromal Cells- Containing Tissue Engineered Constructs

A Sequential Micro-Immunotherapy Medicine Increases Collagen Deposition in Human Gingival Fibroblasts and in an Engineered 3D Gingival Model under Inflammatory Conditions

Periodontal therapies use immune mediators, but their side effects can increase with dosage. Micro-immunotherapy (MI) is a promising alternative that employs immune regulators at low and ultralow doses to minimize adverse effects. In this study, the effects of 5 capsules and the entire 10-capsule sequence of the sequential MI medicine (MIM-seq) were tested in two in vitro models of periodontitis. Firstly, human gingival fibroblasts (hGFs) exposed to interleukin (IL)-1β to induce inflammation were treated with five different capsules of MIM-seq for 3 days or with MIM-seq for 24 days. Subsequently, MIM-seq was analyzed in a 3D model of human tissue equivalent of gingiva (GTE) under the same inflammatory stimulus. Simultaneously, a non-IL-1β-treated control and a vehicle were included. The effects of the treatments on cytotoxicity, collagen deposition, and the secreted levels of IL-1α, IL-6, prostaglandin E2 (PGE2), matrix metalloproteinase-1 (MMP-1), and tissue inhibitor of metalloproteinases-1 (TIMP-1) were evaluated. None of the tested items were cytotoxic. The complete sequence of MIM-seq decreased PGE2 release and restored collagen deposition levels induced by IL-1β treatment in hGFs exposed to IL-1β. MIM-seq treatment restored collagen production levels in both models. These promising preclinical findings suggest that MIM-seq should be further investigated for periodontitis treatment.

Bone Tissue Engineering in Rat Calvarial Defects Using Induced Bone-like Tissue by rhBMPs from Immature Muscular Tissues In Vitro

This study aimed to induce bone-like tissue from immature muscular tissue (IMT) in vitro using commercially available recombinant human bone morphogenetic protein (rhBMP)-2, rhBMP-4, and rhBMP-7, and then implanting this tissue into a calvarial defect in rats to assess healing. IMTs were extracted from 20-day-old Sprague-Dawley (SD) fetal rats, placed on expanded polytetrafluoroethylene (ePTFE) with 10 ng/μL each of rhBMP-2, BMP-4, and BMP-7, and cultured for two weeks. The specimens were implanted into calvarial defects in 3-week-old SD rats for up to three weeks. Relatively strong radiopacity was observed on micro-CT two weeks after culture, and bone-like tissue, comprising osteoblastic cells and osteoids, was partially observed by H&E staining. Calcium, phosphorus, and oxygen were detected in the extracellular matrix using an electron probe micro analyzer, and X-ray diffraction patterns and Fourier transform infrared spectroscopy spectra of the specimen were found to have typical apatite crystal peaks and spectra, respectively. Furthermore, partial strong radiopacity and ossification were confirmed one week after implantation, and a dominant novel bone was observed after two weeks in the defect site. Thus, rhBMP-2, BMP-4, and BMP-7 differentiated IMT into bone-like tissue in vitro, and this induced bone-like tissue has ossification potential and promotes the healing of calvarial defects. Our results suggest that IMT is an effective tissue source for bone tissue engineering.

Effects of Coculture Fibroblasts and Vascular Endothelial Cells on Proliferation and Osteogenesis of Adipose Stem Cells

Background

The development of tissue engineering provides a new method for the clinical treatment of bone defects, but the problems of slow formation and slow vascularization of tissue engineered bone have always existed. Studies have shown that the combined culture system of vascular endothelial cells and adipose stem cells is superior to single cell in repairing bone defects. With the excellent proliferation ability, secretion of synthetic collagen and a variety of regulatory factors and fibroblasts can differentiate into osteoblasts and have the potential to be excellent seed cells involved in tissue engineering bone construction.

Objective

To investigate the effects of combined culture of fibroblasts, vascular endothelial cells, and adipose stem cells on proliferation and osteogenic differentiation of adipose stem cells.

Methods

The cells were divided into 4 groups: adipose stem cell group, adipose stem cell+vascular endothelial cell coculture group, adipose stem cell+fibroblast coculture group, and adipose stem cell+vascular endothelial cell+fibroblast coculture group. The morphological changes of the cells were observed under an inverted microscope. After 1, 3, 5, 7, and 9 days of coculture, the proliferation of adipose stem cells in each group was detected by a CCK-8 method and the growth curve was plotted. Adipose stem cells in each group were stained with alizarin red and alkaline phosphatase at days 7, 14, 21, and 28. At the third week of coculture, Western blot was used to detect the expression level of bone morphogenetic protein 2 of adipose stem cells in each group. Results and Conclusions. (1) After 14 days of culture, some cells in the adipose stem cell+vascular endothelial cell+fibroblast coculture group fused into clumps and distributed in nests, while the adipose stem cells in the adipose stem cell group had a single cell morphology and no cell clusters were observed. (2) The cell growth curves were basically the same in each group, and the absorbance value increased gradually. The absorbance value of the adipocyte+vascular endothelial cell+fibroblast coculture group was the highest, followed by the adipocyte+fibroblast coculture group and then the adipocyte+fibroblast coculture group. (3) Alizarin red staining showed negative reaction in each group on the 7th day, and a small number of red positive cells gradually appeared in each group as time went on. On the 28th day, red positive cells were found in all groups, and most of them were in the coculture group of adipose stem cells+vascular endothelial cells+fibroblasts, showing red focal. The coculture group of adipose stem cells+vascular endothelial cells and adipose stem cells+fibroblasts was less, and the adipose stem cell group was the least. On day 28 of alkaline phosphatase staining, cells in each group had red positive particles, and the adipose stem cell+vascular endothelial cell+fibroblast coculture group and adipose stem cell+fibroblast coculture group had the most, followed by the adipose stem cell+vascular endothelial cell coculture group and then the adipose stem cell group. (4) Bone morphogenetic protein 2 was expressed in all groups, especially in adipose stem cell+fibroblast coculture group and adipose stem cell+vascular endothelial cell+ fibroblast coculture group. (5) Fibroblast could promote adipose stem cell osteogenic differentiation better than vascular endothelial cells, but the proliferation effect was not as good as vascular endothelial cells. The coculture system of fibroblast combined with vascular endothelial cells and adipose stem cells promoted the proliferation of adipose stem cells and the rapid and efficient differentiation of adipose stem cells into osteoblasts.

Bone marrow mesenchymal stem cells with low dose bone morphogenetic protein 2 enhances scaffold-based spinal fusion in a porcine model

High doses bone morphogenetic protein 2 (BMP-2) have resulted in a series of complications in spinal fusion. We previously established a polyelectrolyte complex (PEC) carrier system that reduces the therapeutic dose of BMP-2 in both rodent and porcine spinal fusion models. This study aimed to evaluate the safety and efficacy of the combination of bone marrow mesenchymal stem cells (BMSCs) and low dose BMP-2 delivered by PEC for bone regeneration in a porcine model of anterior lumbar interbody spinal fusion (ALIF) application. Six Yorkshire pigs underwent a tri-segmental (L2/L3; L3/L4; L4/L5) ALIF in four groups, namely: (a) BMSCs + 25 μg BMP-2/PEC (n = 9), (b) 25 μg BMP-2/PEC (n = 3), (c) BMSCs (n = 3), and (d) 50 μg BMP-2/absorbable collagen sponge (n = 3). Fusion outcomes were evaluated by radiography, biomechanical testing, and histological analysis after 12 weeks. Mean radiographic scores at 12 weeks were 2.7, 2.0, 1.0, and 1.0 for Groups 1 to 4, respectively. μ-CT scanning, biomechanical evaluation, and histological analysis demonstrated solid fusion and successful bone regeneration in Group 1. In contrast, Group 2 showed inferior quality and slow rate of fusion, and Groups 3 and 4 failed to fuse any of the interbody spaces. There was no obvious evidence of seroma formation, implant rejection, or any other complications in all groups. The results suggest that the combination of BMSCs and low dose BMP-2/PEC could further lower down the effective dose of the BMP-2 and be used as a bone graft substitute in the large animal ALIF model.

Osteogenesis and degradation behavior of magnesium alloy plate in vivo

Introduction: The magnesium alloy was fabricated into orthopedic plates, and used to repair tibial fractures of New Zealand white rabbits. The osteogenesis and degradation behavior of magnesium alloy plates were investigated in vivo. Methods: 38 rabbits were randomly divided into an experimental group using the magnesium alloy plate and control group using a titanium alloy plate. Tibial fractures in the experimental group and control group were fixed with magnesium alloy plates and titanium alloy plates, respectively. An X-ray of the fracture site was taken at 1, 2, 4, 8, and 16 weeks after surgery. The formation of callus and expression of bone morphogenetic protein (BMP-2) in each group were examined at 4, 8, and 16 weeks postoperatively. The degradation behavior of the magnesium alloy plate was observed using a scanning electron microscope with an energy dispersive spectroscopy system. Results: The results of X-ray showed that the fracture healed gradually and there was significant callus around the plate in the magnesium alloy plate group than that in the titanium alloy plate groups. The formation of callus and the expression of BMP-2 in the magnesium alloy plate group were more significant than that in the titanium plate group. The degradation behavior of the magnesium alloy plates deepened in vivo with the implantation time. Conclusion: The results demonstrated that the magnesium alloy plate implanted into the rabbit tibia could promote the formation of callus and result in osteogenesis in vivo. Meanwhile, the magnesium alloy plate was absorbed gradually in vivo.

BMP4 micro-immunotherapy increases collagen deposition and reduces PGE2 release in human gingival fibroblasts and increases tissue viability of engineered 3D gingiva under inflammatory conditions

Background

We aimed to evaluate the effect of low doses (LD) bone morphogenetic protein‐2 (BMP2) and BMP4 micro‐immunotherapy (MI) in two in vitro models of periodontal wound healing/regeneration.

Methods

We first evaluated the effect of LD of BMP2 and BMP4 MI on a 2D cell culture using human gingival fibroblasts (hGF) under inflammatory conditions induced by IL1β. Biocompatibility, inflammatory response (Prostaglandin E2 (PGE2) release), collagen deposition and release of extracellular matrix (ECM) organization‐related enzymes (matrix metalloproteinase‐1 (MMP1) and metalloproteinase inhibitor 1 (TIMP1)) were evaluated after short (3 days) and long‐term (24 days) treatment with BMP2 or BMP4 MI. Then, given the results obtained in the 2D cell culture, LD BMP4 MI treatment was evaluated in a 3D cell culture model of human tissue equivalent of gingiva (GTE) under the same inflammatory stimulus, evaluating the biocompatibility, inflammatory response and effect on MMP1 and TIMP1 release.

Results

LD BMP4 was able to decrease the release of the inflammatory mediator PGE2 and completely re‐establish the impaired collagen metabolism induced by IL1β treatment. In the 3D model, LD BMP4 treatment improved tissue viability compared with the vehicle, with similar levels to 3D tissues without inflammation. No significant effects were observed on PGE2 levels nor MMP1/TIMP1 ratio after LD BMP4 treatment, although a tendency to decrease PGE2 levels was observed after 3 days.

Conclusions

LD BMP4 MI treatment shows anti‐inflammatory and regenerative properties on hGF, and improved viability of 3D gingiva under inflammatory conditions. LD BMP4 MI treatment could be used on primary prevention or maintenance care of periodontitis.

Morphogen Delivery by Osteoconductive Nanoparticles Instructs Stromal Cell Spheroid Phenotype

Mesenchymal stem/stromal cells (MSCs) exhibit a rapid loss in osteogenic phenotype upon removal of osteoinductive cues, as commonly occurs during transplantation. Osteogenic differentiation can be more effectively but not fully maintained by aggregating MSCs into spheroids. Therefore, the development of effective strategies that prolong the efficacy of inductive growth factors would be advantageous for advancing cell-based therapies. To address this challenge, osteoinductive bone morphogenetic protein-2 (BMP-2) was adsorbed to osteoconductive hydroxyapatite (HA) nanoparticles for incorporation into MSC spheroids. MSC induction was evaluated in osteogenic conditions and retention of the osteogenic phenotype in the absence of other osteogenic cues. HA was more uniformly incorporated into spheroids at lower concentrations, while BMP-2 dosage was dependent upon initial morphogen concentration. MSC spheroids containing BMP-2-loaded HA nanoparticles exhibited greater alkaline phosphatase (ALP) activity and more uniform spatial expression of osteocalcin compared to spheroids with uncoated HA nanoparticles. Spheroids cultured in media containing soluble BMP-2 demonstrated differentiation only at the spheroid periphery. Furthermore, the osteogenic phenotype of MSC spheroids was better retained with BMP-2-laden HA upon the removal of soluble osteogenic cues. These findings represent a promising strategy for simultaneous delivery of osteoconductive and osteoinductive signals for enhancing MSC participation in bone formation.

Mesenchymal Stem Cells for Regenerative Medicine

In recent decades, the biomedical applications of mesenchymal stem cells (MSCs) have attracted increasing attention. MSCs are easily extracted from the bone marrow, fat, and synovium, and differentiate into various cell lineages according to the requirements of specific biomedical applications. As MSCs do not express significant histocompatibility complexes and immune stimulating molecules, they are not detected by immune surveillance and do not lead to graft rejection after transplantation. These properties make them competent biomedical candidates, especially in tissue engineering. We present a brief overview of MSC extraction methods and subsequent potential for differentiation, and a comprehensive overview of their preclinical and clinical applications in regenerative medicine, and discuss future challenges.