Osteogenic and Chondrogenic Potential of Periosteum-Derived Mesenchymal Stromal Cells: Do They Hold the Key to the Future?

The periosteum, with its outer fibrous and inner cambium layer, lies in a dynamic environment with a niche of pluripotent stem cells for their reparative needs. The inner cambium layer is rich in mesenchymal progenitors, osteogenic progenitors, osteoblasts, and fibroblasts in a scant collagen matrix environment. Their role in union and remodeling of fracture is well known. However, the periosteum as a source of mesenchymal stem cells has not been explored in detail. Moreover, with the continuous expansion of techniques, newer insights have been acquired into the roles and regulation of these periosteal cells. From a therapeutic standpoint, the periosteum as a source of tissue engineering has gained much attraction. Apart from its role in bone repair, analysis of the bone-forming potential of periosteum-derived stem cells is lacking. Hence, this article elucidates the role of the periosteum as a potential source of mesenchymal stem cells along with their capacity for osteogenic and chondrogenic differentiation for therapeutic application in the future.

Influence of Human Jaw Periosteal Cells Seeded β-Tricalcium Phosphate Scaffolds on Blood Coagulation

Tissue engineering offers auspicious opportunities in oral and maxillofacial surgery to heal bone defects. For this purpose, the combination of cells with stability-providing scaffolds is required. Jaw periosteal cells (JPCs) are well suited for regenerative therapies, as they are easily accessible and show strong osteogenic potential. In this study, we analyzed the influence of uncoated and polylactic-co-glycolic acid (PLGA)-coated β-tricalcium phosphate (β-TCP) scaffolds on JPC colonization and subsequent osteogenic differentiation. Furthermore, interaction with the human blood was investigated. This study demonstrated that PLGA-coated and uncoated β-TCP scaffolds can be colonized with JPCs and further differentiated into osteogenic cells. On day 15, after cell seeding, JPCs with and without osteogenic differentiation were incubated with fresh human whole blood under dynamic conditions. The activation of coagulation, complement system, inflammation, and blood cells were analyzed using ELISA and scanning electron microscopy (SEM). JPC-seeded scaffolds showed a dense cell layer and osteogenic differentiation capacity on both PLGA-coated and uncoated β-TCP scaffolds. SEM analyses showed no relevant blood cell attachment and ELISA results revealed no significant increase in most of the analyzed cell activation markers (β-thromboglobulin, Sc5B-9, polymorphonuclear (PMN)-elastase). However, a notable increase in thrombin-antithrombin III (TAT) complex levels, as well as fibrin fiber accumulation on JPC-seeded β-TCP scaffolds, was detected compared to the scaffolds without JPCs. Thus, this study demonstrated that besides the scaffold material the cells colonizing the scaffolds can also influence hemostasis, which can influence the regeneration of bone tissue.

Jaw Periosteum-Derived Mesenchymal Stem Cells Regulate THP-1-Derived Macrophage Polarization

Mesenchymal stem cells from bone marrow have powerful immunomodulatory capabilities. The interactions between jaw periosteal cells (JPCs) and macrophages are not only relevant for the application of JPCs in regenerative medicine, but this understanding could also help treating diseases like osteonecrosis of the jaw. In previous studies, we analyzed, for the first time, immunomodulatory features of 2D- and 3D-cultured JPCs. In the present work, the effects of JPCs on the polarization state of macrophages in contact coculture were analyzed. To improve the macrophage polarization study, different concentrations of PMA (5 nM, 25 nM, and 150 nM) or different medium supplementations (10% FBS, 10% hPL and 5% hPL) were compared. Further, in order to analyze the effects of JPCs on macrophage polarization, JPCs and PMA-stimulated THP-1 cells were cocultured under LPS/IFN-γ or IL-4/IL-13 stimulatory conditions. Surface marker expression of M1 and M2 macrophages were analyzed under the different culture supplementations in order to investigate the immunomodulatory properties of JPCs. Our results showed that 5 nM PMA can conduct an effective macrophage polarization. The analyses of morphological parameters and surface marker expression showed more distinct M1/M2 phenotypes over FBS supplementation when using 5% hPL during macrophage polarization. In the coculture, immunomodulatory properties of JPCs improved significantly under 5% hPL supplementation compared to other supplementations. We concluded that, under the culture condition with 5% hPL, JPCs were able to effectively induce THP-1-derived macrophage polarization.

Role of FBXW2 in explant culture of bovine periosteum-derived cells

Osteoporosis and bone fracture decrease quality of life. Bone regeneration is a notable technique for osteoporosis treatment. A previous study reported that F-box and WD-40 domain-containing protein 2 (FBXW2) and osteocalcin have the same shape in the periosteum after 5 weeks. However, the osteoblastic functions of FBXW2 are not clear. In this study, double fluorescent immunostaining revealed a small amount of osteocalcin in the area of FBXW2 aggregation at 1 week, periosteal cells, and osteocalcin pushed toward the edge of periosteum, and, apart from FBXW2 tubes at 2 weeks, multilayered periosteum-derived cells at 3 weeks and sticking of osteocalcin in the periosteum with cells at 4 weeks. At 5 weeks, FBXW2 disappeared at the root of periosteum-derived cells, while osteocalcin and cells remained. Based on these results, it is hypothesized that FBXW2 maintains tissue shapes and prevents escape of inner periosteal cells, and the disappearance of FBXW2 causes migration of periosteum-derived cells out of the periosteum along with osteocalcin. Furthermore, FBXW2 may play a role in dynamic tissue remodeling and bone formation.

Dual neutralisation of IL-17F and IL-17A with bimekizumab blocks inflammation-driven osteogenic differentiation of human periosteal cells

ObjectivesInterleukin (IL)-17 signalling has been shown to be a key regulator of disease in ankylosing spondylitis (AS) with several IL-17 blockers currently clinically approved. Despite this, the role of IL-17 in bone pathology is poorly understood. This study aimed to investigate IL-17 signalling in the context of pathological bone formation.MethodsA biomimetic human periosteum-derived cell (hPDC) model of osteogenic differentiation was used in combination with recombinant IL-17 cytokines, T-cell supernatants or serum from patients with AS. IL-17A, IL-17F and bimekizumab monoclonal antibodies were used to block IL-17 cytokine action.ResultsRecombinant IL-17A and IL-17F are pro-osteogenic with respect to hPDC differentiation. T helper 17 or γδ-T cell supernatants also potently stimulated in vitro bone formation, which was blocked deeper by dual inhibition of IL-17A and IL-17F than by neutralisation of IL-17A or IL-17F individually. Osteogenic blockade may be due to an increase in expression of the Wnt antagonist DKK1. Interestingly, osteocommitment was also induced by serum obtained from patients with AS, which was also abrogated by dual neutralisation of IL-17A and IL-17F.ConclusionsThese data show for the first time that IL-17A and IL-17F enhance in vitro osteogenic differentiation and bone formation from hPDCs, inhibition of which may offer an attractive therapeutic strategy to prevent pathological bone formation.

Heterogeneity of murine periosteum osteochondroprogenitors involved in fracture healing

The periosteum is the major source of cells involved in fracture healing. We sought to characterize differences in progenitor cell populations between periosteum and other bone compartments, and identify periosteal cells involved in fracture healing. The periosteum is highly enriched for progenitor cells, including Sca1+ cells, CFU-F and label-retaining cells. Lineage tracing with αSMACreER identifies periosteal cells that contribute to >80% of osteoblasts and ~40% of chondrocytes following fracture. A subset of αSMA+ cells are quiescent long-term injury-responsive progenitors. Ablation of αSMA+ cells impairs fracture callus formation. In addition, committed osteoblast-lineage cells contributed around 10% of osteoblasts, but no chondrocytes in fracture calluses. Most periosteal progenitors, particularly those that form osteoblasts, can be targeted by αSMACreER. We have demonstrated that the periosteum is highly enriched for skeletal stem and progenitor cells and there is heterogeneity in the populations of cells that contribute to mature lineages during periosteal fracture healing.