The wonders of BMP9:From mesenchymal stem cell differentiation,angiogenesis,neurogenesis,tumorigenesis,and metabolism to regenerative medicine

Although bone morphogenetic proteins(BMPs)initially showed effective induction of ectopic bone growth in muscle,it has since been determined that these proteins,as members of the TGF-b superfamily,play a diverse and critical array of biological roles.These roles include regulating skeletal and bone formation,angiogenesis,and development and homeostasis of multiple organ systems.Disruptions of the members of the TGF-b/BMP superfamily result in severe skeletal and extra-skeletal irregularities,suggesting high therapeutic potential from understanding this family of BMP proteins.Although it was once one of the least characterized BMPs,BMP9 has revealed itself to have the highest osteogenic potential across numerous experiments both in vitro and in vivo,with recent studies suggesting that the exceptional potency of BMP9 may result from unique signaling pathways that differentiate it from other BMPs.The effectiveness of BMP9 in inducing bone formation was recently revealed in promising experiments that demonstrated efficacy in the repair of critical sized cranial defects as well as compatibility with bone-inducing bio-implants,revealing the great translational promise of BMP9.Furthermore,emerging evidence indicates that,besides its osteogenic activity,BMP9 exerts a broad range of biological functions,including stem cell differentiation,angiogenesis,neurogenesis,tumorigenesis,and metabolism.This review aims to summarize our current understanding of BMP9 across biology and the body.

Highly expressed BMP9/GDF2 in postnatal mouse liver and lungs may account for its pleiotropic effects on stem cell differentiation,angiogenesis,tumor growth and metabolism

Bone morphogenetic protein 9(BMP9)(or GDF2)was originally identified from fetal mouse liver cDNA libraries.Emerging evidence indicates BMP9 exerts diverse and pleiotropic functions during postnatal development and in maintaining tissue homeostasis.However,the expression landscape of BMP9 signaling during development and/or in adult tissues remains to be analyzed.Here,we conducted a comprehensive analysis of the expression landscape of BMP9 and its signaling mediators in postnatal mice.By analyzing mouse ENCODE transcriptome datasets we found Bmp9 was highly expressed in the liver and detectable in embryonic brain,adult lungs and adult placenta.We next conducted a comprehensive qPCR analysis of RNAs isolated from major mouse tissues/organs at various ages.We found that Bmp9 was highly expressed in the liver and lung tissues of young adult mice,but decreased in older mice.Interestingly,Bmp9 was only expressed at low to modest levels in developing bones.BMP9-associated TGFβ/BMPR type I receptor Alk1 was highly expressed in the adult lungs.Furthermore,the feedback inhibitor Smads Smad6 and Smad7 were widely expressed in mouse postnatal tissues.However,the BMP signaling antagonist noggin was highly expressed in fat and heart in the older age groups,as well as in kidney,liver and lungs in a biphasic fashion.Thus,our findings indicate that the circulating BMP9 produced in liver and lungs may account for its pleiotropic effects on postnatal tissues/organs although possible roles of BMP9 signaling in liver and lungs remain to be fully understood.

Neural EGF-like protein 1(NELL-1):Signaling crosstalk in mesenchymal stem cells and applications in regenerative medicine

Bone tissue regeneration holds the potential to solve both osteoporosis and large skeletal defects,two problems associated with significant morbidity.The differentiation of mesenchymal stem cells into the osteogenic lineage requires a specific microenvironment and certain osteogenic growth factors.Neural EGF Like-Like molecule 1(NELL-1)is a secreted glycoprotein that has proven,both in vitro and in vivo,to be a potent osteo-inductive factor.Furthermore,it has been shown to repress adipogenic differentiation and inflammation.NELL-1 can work synergistically with other osteogenic factors such as Bone Morphogenic Protein(BMP)
2 and
9,and has shown promise for use in tissue engineering and as a systemically administered drug for the treatment of osteoporosis.Here we provide a comprehensive up-to-date review on the molecular signaling cascade of NELL-1 in mesenchymal stem cells and potential applications in bone regenerative engineering.

3-D bioprinting technologies in tissue engineering and regenerative medicine:Current and future trends

Advances in three-dimensional(3D)printing have increased feasibility towards the synthesis of living tissues.Known as 3D bioprinting,this technology involves the precise layering of cells,biologic scaffolds,and growth factors with the goal of creating bioidentical tissue for a variety of uses.Early successes have demonstrated distinct advantages over conventional tissue engineering strategies.Not surprisingly,there are current challenges to address before 3D bioprinting becomes clinically relevant.Here we provide an overview of 3D bioprinting technology and discuss key advances,clinical applications,and current limitations.While 3D bioprinting is a relatively novel tissue engineering strategy,it holds great potential to play a key role in personalized medicine.

Notch signaling:Its essential roles in bone and craniofacial development

Notch is a cellecell signaling pathway that is involved in a host of activities including development,oncogenesis,skeletal homeostasis,and much more.More specifically,recent research has demonstrated the importance of Notch signaling in osteogenic differentiation,bone healing,and in the development of the skeleton.The craniofacial skeleton is complex and understanding its development has remained an important focus in biology.In this review we briefly summarize what recent research has revealed about Notch signaling and the current understanding of how the skeleton,skull,and face develop.We then discuss the crucial role that Notch plays in both craniofacial development and the skeletal system,and what importance it may play in the future.

Argonaute(AGO)proteins play an essential role in mediating BMP9-induced osteogenic signaling in mesenchymal stem cells(MSCs)

As multipotent progenitor cells,mesenchymal stem cells(MSCs)can renew themselves and give rise to multiple lineages including osteoblastic,chondrogenic and adipogenic lineages.It’s previously shown that BMP9 is the most potent BMP and induces osteogenic and adipogenic differentiation of MSCs.However,the molecular mechanism through which BMP9 regulates MSC differentiation remains poorly understood.Emerging evidence indicates that noncoding RNAs,especially microRNAs,may play important roles in regulating MSC differentiation and bone formation.As highly conserved RNA binding proteins,Argonaute(AGO)proteins are essential components of the multi-protein RNA-induced silencing complexes(RISCs),which are critical for small RNA biogenesis.Here,we investigate possible roles of AGO proteins in BMP9-induced lineage-specific differentiation of MSCs.We first found that BMP9 upregulated the expression of Ago1,Ago2 and Ago3 in MSCs.By engineering multiplex siRNA vectors that express multiple siRNAs targeting individual Ago genes or all four Ago genes,we found that silencing individual Ago expression led to a decrease in BMP9-induced early osteogenic marker alkaline phosphatase(ALP)activity in MSCs.Furthermore,we demonstrated that simultaneously silencing all four Ago genes significantly diminished BMP9-induced osteogenic and adipogenic differentiation of MSCs and matrix mineralization,and ectopic bone formation.Collectively,our findings strongly indicate that AGO proteins and associated small RNA biogenesis pathway play an essential role in mediating BMP9-induced osteogenic differentiation of MSCs.

SATB2:A versatile transcriptional regulator of craniofacial and skeleton development,neurogenesis and tumorigenesis,and its applications in regenerative medicine

SATB2(special AT-rich sequence-binding protein 2)is a member of the special AT-rich binding protein family.As a transcription regulator,SATB2 mainly integrates higher-order chromatin organization.SATB2 expression appears to be tissue-and stage-specific,and is governed by several cellular signaling molecules and mediators.Expressed in branchial arches and osteoblast-lineage cells,SATB2 plays a significant role in craniofacial pattern and skeleton development.In addition to regulating osteogenic differentiation,SATB2 also displays versatile functions in neural development and cancer progression.As an osteoinductive factor,SATB2 holds great promise in improving bone regeneration toward bone defect repair.In this review,we have summarized our current understanding of the physiological and pathological functions of SATB2 in craniofacial and skeleton development,neurogenesis,tumorigenesis and regenerative medicine.

Development of a simplified and inexpensive RNA depletion method for plasmid DNA purification using size selection magnetic beads(SSMBs)

Plasmid DNA(pDNA)isolation from bacterial cells is one of the most common and critical steps in molecular cloning and biomedical research.Almost all pDNA purification in-volves disruption of bacteria,removal of membrane lipids,proteins and genomic DNA,purifi-cation of pDNA from bulk lysate,and concentration of pDNA for downstream applications.While many liquid-phase and solid-phase pDNA purification methods are used,the final pDNA preparations are usually contaminated with varied degrees of host RNA,which cannot be completely digested by RNase A.To develop a simple,cost-effective,and yet effective method for RNA depletion,we investigated whether commercially available size selection magnetic beads(SSMBs),such as Mag-Bind®TotalPure NGS Kit(or Mag-Bind),can completely deplete bacterial RNA in pDNA preparations.In this proof-of-principle study,we demonstrated that,compared with RNase A digestion and two commercial plasmid affinity purification kits,the SSMB method was highly efficient in depleting contaminating RNA from pDNA minipreps.Gene transfection and bacterial colony formation assays revealed that pDNA purified from SSMB method had superior quality and integrity to pDNA samples cleaned up by RNase A digestion and/or commercial plasmid purification kits.We further demonstrated that the SSMB method completely depleted contaminating RNA in large-scale pDNA samples.Furthermore,the Mag-bind-based SSMB method costs only 5-10%of most commercial plasmid purification kits on a per sample basis.Thus,the reported SSMB method can be a valuable and inexpensive tool for the removal of bacterial RNA for routine pDNA preparations.