WNT3A and the induction of the osteogenic differentiation in adipose tissue derived mesenchymal stem cells

Functionalized 3D-Printed ST2/Gelatin Methacryloyl/Polcaprolactone Scaffolds for Enhancing Bone Regeneration with Vascularization

Growth factors were often used to improve the bioactivity of biomaterials in order to fabricate biofunctionalized bone grafts for bone defect repair. However, supraphysiological concentrations of growth factors for improving bioactivity could lead to serious side effects, such as ectopic bone formation, radiculitis, swelling of soft tissue in the neck, etc. Therefore, safely and effectively applying growth factors in bone repair biomaterials comes to be an urgent problem that needs to be addressed. In this study, an appropriate concentration (50 ng/mL) of Wnt3a was used to pretreat the 3D-bioprinting gelatin methacryloyl(GelMA)/polycaprolactone(PCL) scaffold loaded with bone marrow stromal cell line ST2 for 24 h. This pretreatment promoted the cell proliferation, osteogenic differentiation, and mineralization of ST2 in the scaffold in vitro, and enhanced angiogenesis and osteogenesis after being implanted in critical-sized mouse calvarial defects. On the contrary, the inhibition of Wnt/β-catenin signaling in ST2 cells reduced the bone repair effect of this scaffold. These results suggested that ST2/GelMA/PCL scaffolds pretreated with an appropriate concentration of Wnt3a in culture medium could effectively enhance the osteogenic and angiogenic activity of bone repair biomaterials both in vitro and in vivo. Moreover, it would avoid the side effects caused by the supraphysiological concentrations of growth factors. This functionalized scaffold with osteogenic and angiogenic activity might be used as an outstanding bone substitute for bone regeneration and repair.

GSK3β rephosphorylation rescues ALPL deficiency-induced impairment of odontoblastic differentiation of DPSCs

Background

Premature exfoliation of the deciduous teeth is a common manifestation in childhood patients with hypophosphatasia (HPP), which is an autosomal inherited disease caused by ALPL mutations. Dysplasia of the cementum, dentin, and alveolar bone has been proposed to be the main reasons for the exfoliation of teeth, while the extraordinarily complex intracellular mechanisms remain elusive. Dental pulp stem cells (DPSCs) have been demonstrated to successfully regenerate functional pulp-dentin-like tissue. Dental pulp cells derived from HPP patients impaired mineralization; however, insight into the deeper mechanism is still unclear.

Methods

The effects of ALPL on odontoblastic differentiation of DPSCs from HPP patient were assessed by Alizarin Red staining, immunofluorescent staining, Western blot and RT-PCR, and micro-CT assays.

Result

Here, we found DPSCs from HPP patient exhibited low ALP activity and impaired odontoblastic differentiation. Meanwhile, we found that loss of function of ALPL reduced phosphorylation of GSK3β in DPSCs. While GSK3β rephosphorylation improved odontoblastic differentiation of HPP DPSCs with LiCl treatment. Finally, we demonstrated systemic LiCl injection ameliorated tooth-associated defects in ALPL^+/− mice by enhanced phosphorylation of GSK3β in the teeth.

Conclusions

Our study indicates that ALPL regulates odontoblastic differentiation of DPSCs and provides useful information for understanding how ALPL deficiency led to tooth dysplasia and, ultimately, may inform efforts at improvement tooth defects in HPP patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02235-7.

Influence of the TGF-β Superfamily on Osteoclasts/Osteoblasts Balance in Physiological and Pathological Bone Conditions

The balance between bone forming cells (osteoblasts/osteocytes) and bone resorbing cells (osteoclasts) plays a crucial role in tissue homeostasis and bone repair. Several hormones, cytokines, and growth factors-in particular the members of the TGF-β superfamily such as the bone morphogenetic proteins-not only regulate the proliferation, differentiation, and functioning of these cells, but also coordinate the communication between them to ensure an appropriate response. Therefore, this review focuses on TGF-β superfamily and its influence on bone formation and repair, through the regulation of osteoclastogenesis, osteogenic differentiation of stem cells, and osteoblasts/osteoclasts balance. After introducing the main types of bone cells, their differentiation and cooperation during bone remodeling and fracture healing processes are discussed. Then, the TGF-β superfamily, its signaling via canonical and non-canonical pathways, as well as its regulation by Wnt/Notch or microRNAs are described and discussed. Its important role in bone homeostasis, repair, or disease is also highlighted. Finally, the clinical therapeutic uses of members of the TGF-β superfamily and their associated complications are debated.

Polydatin improves osteogenic differentiation of human bone mesenchymal stem cells by stimulating TAZ expression via BMP2-Wnt/β-catenin signaling pathway

OBJECTIVES

Polydatin (PD), extracted from Polygonum cuspidatum, has shown potential therapeutic applications due to its antiosteoporotic and anti-inflammatory activities. Our previous study suggested that PD promotes the osteogenesis of human bone marrow stromal cells (hBMSCs) via the BMP2-Wnt/β-catenin pathway. The aim of our present study was to further explore the role of PD-mediated regulation of Tafazzin (TAZ), a transcriptional coactivator with a PDZ-binding motif, in osteogenesis.

MATERIALS AND METHODS

hBMSCs were isolated and treated with PD at various concentrations. Alizarin red staining and RT-qPCR were performed to identify calcium complex deposition in hBMSCs as well as the expression of specific osteoblast-related markers, respectively, in each group. Next, TAZ-silenced hBMSCs were generated by lentivirus-produced TAZ shRNA. After treatment with PD, the osteogenic abilities of the TAZ-silenced and control hBMSCs were estimated by ALP activity assay, and expression of the TAZ protein was detected by Western blot analysis and immunofluorescence staining. In vitro, an ovariectomized (OVX) mouse model was established and used to evaluate the effect of PD on bone destruction by micro-CT, immunohistochemistry, and ELISA.

RESULTS

In vitro, 30 μM PD significantly improved the proliferation and calcium deposition of hBMSCs and markedly stimulated the expression of the mRNAs RUNX2, Osteopontin, DLX5, β-catenin, TAZ, and Osteocalcin (OCN). Osteogenic differentiation induced by PD was blocked by lentivirus-mediated TAZ shRNA. Furthermore, Noggin (a regulator of bone morphogenic protein 2 (BMP2)) and DKK1 (an inhibitor of the Wnt/β-catenin pathway) were found to inhibit the increase in TAZ expression induced by PD. In vivo, PD prevented estrogen deficiency-induced bone loss in the OVX mouse model.

CONCLUSION

Taken together, our findings suggest that PD improved the osteogenic differentiation of hBMSCs and maintained the bone matrix in the OVX mouse model through the activation of TAZ, a potential target gene of the BMP2-Wnt/β-catenin pathway.

p53 inhibits the osteogenic differentiation but does not induce senescence in human dental follicle cells

Replicative senescence causes a reduced osteogenic differentiation potential of senescent dental follicle cells (DFCs). The transcription factor p53 is often involved in the induction of cellular senescence, but little is known about its role in DFCs. This study examined for the first time the role of p53 compared to its pro-proliferative antagonist E2F-1 in terms of osteogenic differentiation potential and induction of senescence. Protein expression of E2F-1 decreased during cell aging, while p53 was expressed constitutively. Gene silencing of E2F1 (E2F-1) inhibited the proliferation rate of DFCs and increased the induction of cellular senescence. The induction of cellular senescence is regulated independently of the gene expression of TP53 (p53), since its gene expression depends on the expression of E2F1. Moreover, gene silencing of TP53 induced E2F1 gene expression and increased cell proliferation, but did not affect the rate of induction of cellular senescence. TP53 knockdown further induced the alkaline phosphatase and mineralization in DFCs. However, the simultaneous silencing of TP53 and E2F1 did not inhibit the inductive effect of TP53 knockdown on osteogenic differentiation, indicating that this effect is independent of E2F-1. In summary, our results suggest that p53 inhibits osteogenic differentiation and cell proliferation in senescent DFCs, but is not significantly involved in senescence induction.

Osteogenic Differentiation of Adipose-Derived Stromal Cells: From Bench to Clinics

In addition to mesenchymal stem cells, adipose-derived stem/stromal cells (ASCs) are an attractive source for a large variety of cell-based therapies. One of their most important potential applications is related to the regeneration of bone tissue thanks to their capacity to differentiate in bone cells. However, this requires a proper control of their osteogenic differentiation, which depends not only on the initial characteristics of harvested cells but also on the conditions used for their culture. In this review, we first briefly describe the preclinical and clinical trials using ASCs for bone regeneration and present the quantitative parameters used to characterize the osteogenic differentiation of ASCs. We then focus on the soluble factors influencing the osteogenic differentiation of ACS, including the steroid hormones and various growth factors, notably the most osteoinductive ones, the bone morphogenetic proteins (BMPs). Impact statement Adipose-derived stromal/stem cells are reviewed for their use in bone regeneration.

Wnt11 promotes BMP9-induced osteogenic differentiation through BMPs/Smads and p38 MAPK in mesenchymal stem cells

Bone morphogenetic protein 9 (BMP9), as one of the most potent osteogenic factors, is a promising cytokine for bone tissue engineering. Wnt11 can regulate the development of the skeletal system and is related to high bone mass syndrome. However, the effect of Wnt11 on BMP9-induced osteogenic differentiation remains unknown. In this study, we investigated the relationship between Wnt11- and BMP9-induced osteogenic differentiation in mesenchymal stem cells (MSCs). We recapitulated the osteogenic potential of BMP9 in C3H10T1/2 cells. The messenger RNA expression of Wnt11 is detectable in the available progenitor cells, and BMP9 can obviously increase the protein level of Wnt11 in these cells. Exogenous Wnt11 potentiates the effect of BMP9 on increasing alkaline phosphatase (ALP) activities, the expression of osteopontin (OPN), and Runt-related transcription factor 2 (Runx2), so does matrix mineralization in C3H10T1/2 cells. Although Wnt11 cannot increase the BMP9-induced ectopic bone formation, it can increase the bone density induced by BMP9 apparently. Wnt11 increases the level of p-Smad1/5/8, as well as p-p38. Meanwhile, Wnt11 promotes the effect of BMP9 on increasing the levels of p-Smad1/5/8 and p-p38. Inhibition of p38 decreases the BMP9-induced ALP activities, the expression of OPN, and the mineralization in C3H10T1/2 cells. However, all of these effects of the p38 inhibitor on BMP9-induced osteogenic markers can be almost reversed by the overexpression of Wnt11. Our findings suggested that Wnt11 can enhance the osteogenic potential of BMP9 in MSCs, and this effect may be partly mediated through enhancing BMPs/Smads and the p38 MAPK signal, which was induced by BMP9.