BMP-9 dependent pathways required for the chondrogenic differentiation of pluripotent stem cells

GDF15 deficiency hinders human trophoblast invasion to mediate pregnancy loss through downregulating Smad1/5 phosphorylation

Growth differentiation factor 15 (GDF15) belongs to the Transforming growth factor β(TGF-β) superfamily. The decrease of GDF15 in the serum of pregnant women was associated with miscarriage. Both IHC and ELISA assays showed that GDF15 in trophoblast tissue and serum of pregnant women who miscarried was significantly lower than in those who had a live birth. GDF15 deficiency was associated with embryo resorption in GDF15 knockout mice through CRIPSR editing. In addition, the migration and invasion ability of HTR-8/SVneo and JEG-3 cells were promoted by GDF15. Mechanistically, GDF15 increased Smad1/5 phosphorylation, resulting in upregulating SNAI1/2, VIMENTIN and downregulating E-CADHERIN. A dual-luciferase reporter assay confirmed that Smad-binding elements (SBE) and/or GC-rich motifs were activated and target genes such as SNAI1/2, SERPINE1, and TIMP3 were transcriptionally regulated by GDF15/Smad5 signaling. Therefore, our data revealed a crucial role of GDF15 on invasion of trophoblast by upregulating the activity of TGF-β/Smad1/5 pathway.

Hyaline cartilage differentiation of fibroblasts in regeneration and regenerative medicine

Amputation injuries in mammals are typically non-regenerative; however, joint regeneration is stimulated by BMP9 treatment, indicating the presence of latent articular chondrocyte progenitor cells. BMP9 induces a battery of chondrogenic genes in vivo, and a similar response is observed in cultures of amputation wound cells. Extended cultures of BMP9-treated cells results in differentiation of hyaline cartilage, and single cell RNAseq analysis identified wound fibroblasts as BMP9 responsive. This culture model was used to identify a BMP9-responsive adult fibroblast cell line and a culture strategy was developed to engineer hyaline cartilage for engraftment into an acutely damaged joint. Transplanted hyaline cartilage survived engraftment and maintained a hyaline cartilage phenotype, but did not form mature articular cartilage. In addition, individual hypertrophic chondrocytes were identified in some samples, indicating that the acute joint injury site can promote osteogenic progression of engrafted hyaline cartilage. The findings identify fibroblasts as a cell source for engineering articular cartilage and establish a novel experimental strategy that bridges the gap between regeneration biology and regenerative medicine.

Summary:In vivo articular cartilage regeneration serves as a model to develop novel approaches for engineering cartilage to repair damaged joints and identifies fibroblasts as a BMP9-inducible chondroprogenitor.

MicroRNAs as Important Regulators Mediate the Multiple Differentiation of Mesenchymal Stromal Cells

MicroRNAs (miRNAs) are endogenous short non-encoding RNAs which play a critical role on the output of the proteins, and influence multiple biological characteristics of the cells and physiological processes in the body. Mesenchymal stem/stromal cells (MSCs) are adult multipotent stem cells and characterized by self-renewal and multidifferentiation and have been widely used for disease treatment and regenerative medicine. Meanwhile, MSCs play a critical role in maintaining homeostasis in the body, and dysfunction of MSC differentiation leads to many diseases. The differentiation of MSCs is a complex physiological process and is the result of programmed expression of a series of genes. It has been extensively proven that the differentiation process or programmed gene expression is also regulated accurately by miRNAs. The differentiation of MSCs regulated by miRNAs is also a complex, interdependent, and dynamic process, and a full understanding of the role of miRNAs will provide clues on the appropriate upregulation or downregulation of corresponding miRNAs to mediate the differentiation efficiency. This review summarizes the roles and associated signaling pathways of miRNAs in adipogenesis, chondrogenesis, and osteogenesis of MSCs, which may provide new hints on MSCs or miRNAs as therapeutic strategies for regenerative medicine and biotherapy for related diseases.

Effects of exogenous nerve growth factor on the expression of BMP-9 and VEGF in the healing of rabbit mandible fracture with local nerve injury

BACKGROUND

Mandibular fracture healing is a complex process involving nerves and growth factors. Nerve growth factor (NGF) not only facilitates the maintenance of sympathetic neurite growth but also stimulates other growth factors that can promote the essential osteogenesis and angiogenesis for fracture healing. Therefore, it is necessary to analyze the combined effects of NGF, bone morphogenic protein-9 (BMP-9), and vascular endothelial growth factor (VEGF) to accelerate the healing of mandible fractures.

METHODS

The models of mandible fracture with local nerve injury established in 48 rabbits were randomly divided into nerve growth factor group (NGF group), gelatin sponge group (GS group), blank group, and intact group. The recovery of nerve reflex was assessed by observing the number of rabbits with lower lip responses to acupuncture. The fracture healing was observed with visual and CBCT, and then callus tissues from the mandibular fracture area were collected for hematoxylin and eosin (HE) staining observation, and the expression of BMP-9 and VEGF in callus at different stages was detected by quantitative real-time PCR (qRT-PCR).

RESULTS

Needling reaction in the lower lip showed the number of animals with nerve reflex recovery was significantly higher in the NGF group than that in the GS and blank groups at the 2nd and 4th weeks after the operation. The combined results of macroscopic observation, CBCT examination, and histological analysis showed that a large number of osteoblasts and some vascular endothelial cells were found around the trabecular bone in the NGF group and the amount of callus formation and reconstruction was better than that in the GS group at the 2nd week after the operation. The qRT-PCR results indicated that the expression levels of BMP-9 and VEGF in the four groups reached the highest values at the 2nd week, while the expression levels of both in the NGF group were significantly higher than that in the GS group.

CONCLUSION

The exogenous NGF could accelerate the healing of mandible fractures. This work will provide a new foundation and theoretical basis for clarifying the mechanism of fracture healing, thereby promoting fracture healing and reducing the disability rate of patients.

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.

Prospects of circadian clock in joint cartilage development

Altering the food intake, exercise, and sleep patterns have a great influence on the homeostasis of the biological clock. This leads to accelerated aging of the articular cartilage, susceptibility to arthropathy and other aspects. Deficiency or overexpression of certain circadian clock-related genes accelerates the cartilage deterioration and leads to phenotypic variation in different joints. The process of joint cartilage development includes the formation of joint site, interzone, joint cavitation, epiphyseal ossification center, and cartilage maturation. The mechanism by which, biological clock regulates the cell-cycle, growth, metabolism, and other biological processes of chondrocytes is poorly understood. Here, we summarized the interaction between biological clock proteins and developmental pathways in chondrogenesis and provided the evidence from other tissues that further predicts the molecular patterns of these protein-protein networks in activation, proliferation, and differentiation. The purpose of this review is to gain deeper understanding of the evolution of cartilage and its irreversibility seen in damage and aging.

TGFβ as a gatekeeper of BMP action in the developing growth plate

The ligands that comprise the Transforming Growth Factor β superfamily highly govern the development of the embryonic growth plate. Members of this superfamily activate canonical TGFβ and/or BMP (Bone Morphogenetic Protein) signaling pathways. How these pathways interact with one another is an area of active investigation. These two signaling pathways have been described to negatively regulate one another through crosstalk involving Smad proteins, the primary intracellular effectors of canonical signaling. More recently, a mechanism for regulation of the BMP pathway through TGFβ and BMP receptor interactions has been described. Here in this review, we demonstrate examples of how TGFβ is a gatekeeper of BMP action in the developing growth plate at both the receptor and transcriptional levels.

BMP9 is a potential therapeutic agent for use in oral and maxillofacial bone tissue engineering

Oral and maxillofacial surgery is often challenging due to defective bone healing owing to the microbial environment of the oral cavity, the additional involvement of teeth and esthetic concerns. Insufficient bone volume as a consequence of aging and some oral and maxillofacial surgical procedures, such as tumor resection of the jaw, may further impact facial esthetics and cause the failure of certain procedures, such as oral and maxillofacial implantation. Bone morphogenetic protein (BMP) 9 (BMP9) is one of the most effective BMPs to induce the osteogenic differentiation of different stem cells. A large cross-talk network that includes the BMP9, Wnt/β, Hedgehog, EGF, TGF-β and Notch signaling pathways finely regulates osteogenesis induced by BMP9. Epigenetic control during BMP9-induced osteogenesis is mainly dependent on histone deacetylases (HDACs), microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), which adds another layer of complexity. As a result, all these factors work together to orchestrate the molecular and cellular events underlying BMP9-related tissue engineering. In this review, we summarize our current understanding of the SMAD-dependent and SMAD-independent BMP9 pathways, with a particular focus on cross-talk and cross-regulation between BMP9 and other major signaling pathways in BMP9-induced osteogenesis. Furthermore, recently discovered epigenetic regulation of BMP9 pathways and the molecular and cellular basis of the application of BMP9 in tissue engineering in current oral and maxillofacial surgery and other orthopedic-related clinical settings are also discussed.

Activated platelet-rich plasma improves cartilage regeneration using adipose stem cells encapsulated in a 3D alginate scaffold

In the current study, the effect of superimposing platelet-rich plasma (PRP) on different culture mediums in a three-dimensional alginate scaffold encapsulated with adipose-derived mesenchymal stem cells for cartilage tissue repair is reported. The three-dimensional alginate scaffolds with co-administration of PRP and/or chondrogenic supplements had a significant effect on the differentiation of adipose mesenchymal stem cells into mature cartilage, as assessed by an evaluation of the expression of cartilage-related markers of Sox9, collagen II, aggrecan and collagen, and glycosaminoglycan assays. For in vivo studies, following induction of osteochondral lesion in a rabbit model, a high degree of tissue regeneration in the alginate plus cell group (treated with PRP plus chondrogenic medium) compared with other groups of cell-free alginate and untreated groups (control) were observed. After 8 weeks, in the alginate plus cell group, functional chondrocytes were observed, which produced immature matrix, and by 16 weeks, the matrix and hyaline-like cartilage became completely homogeneous and integrated with the natural surrounding cartilage in the defect site. Similar effect was also observed in the subchondral bone. The cell-free scaffolds formed fibrocartilage tissue, and the untreated group did not form a continuous cartilage over the defect by 16 weeks.

BMP9 stimulates joint regeneration at digit amputation wounds in mice

A major goal of regenerative medicine is to stimulate tissue regeneration after traumatic injury. We previously discovered that treating digit amputation wounds with BMP2 in neonatal mice stimulates endochondral ossification to regenerate the stump bone. Here we show that treating the amputation wound with BMP9 stimulates regeneration of a synovial joint that forms an articulation with the stump bone. Regenerated structures include a skeletal element lined with articular cartilage and a synovial cavity, and we demonstrate that this response requires the Prg4 gene. Combining BMP2 and BMP9 treatments in sequence stimulates the regeneration of bone and joint. These studies provide evidence that treatment of growth factors can be used to engineer a regeneration response from a non-regenerating amputation wound.

Mammalian joints have poor regenerative capacity following amputation. Here, the authors show that in mice, stimulation of the amputation wound with BMP2 and BMP9 stimulates regeneration of a synovial joint that includes bone, cartilage and a synovial cavity.