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Osteogenic-differentiated mesenchymal stem cell-secreted extracellular matrix as a bone morphogenetic protein-2 delivery system for ectopic bone formation. Acta Biomater 2020; 116:186-200. [PMID: 32911108 DOI: 10.1016/j.actbio.2020.09.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 08/28/2020] [Accepted: 09/02/2020] [Indexed: 02/04/2023]
Abstract
While human bone morphogenetic protein-2 (BMP-2) is a promising growth factor for bone regeneration, a major challenge in biomedical applications is finding an optimal carrier for its delivery at the site of injury. Because of their natural affinities for growth factors (including BMP-2) as well as their role in instructing cell function, cultured cell-derived extracellular matrices (ECM) are of special interest. We hereby hypothesized that a "bony matrix" containing mineralized, osteogenic ECM is a potential efficacious carrier of BMP-2 for promoting bone formation and, therefore, compared the efficacy of the decellularized ECM derived from osteogenic-differentiated human mesenchymal stem cells (hMSCs) to the one obtained from ECM from undifferentiated hMSCs. Our results provided evidence that both ECMs can bind BMP-2 and promote bone formation when implanted ectopically in mice. The osteoinductive potential of BMP-2, however, was greater when loaded within an osteogenic MSC-derived ECM; this outcome was correlated with higher sequestration capacity of BMP-2 over time in vivo. Interestingly, although the BMP-2 mainly bound onto the mineral crystals contained within the osteogenic MSC derived-ECM, these mineral components were not involved in the observed higher osteoinductivity, suggesting that the organic components were the critical components for the matrix efficacy as BMP-2 carrier.
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Asadollahpour Nanaei H, Esmailizadeh A, Ayatollahi Mehrgardi A, Han J, Wu DD, Li Y, Zhang YP. Comparative population genomic analysis uncovers novel genomic footprints and genes associated with small body size in Chinese pony. BMC Genomics 2020; 21:496. [PMID: 32689947 PMCID: PMC7370493 DOI: 10.1186/s12864-020-06887-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 07/06/2020] [Indexed: 12/15/2022] Open
Abstract
Background Body size is considered as one of the most fundamental properties of an organism. Due to intensive breeding and artificial selection throughout the domestication history, horses exhibit striking variations for heights at withers and body sizes. Debao pony (DBP), a famous Chinese horse, is known for its small body size and lives in Guangxi mountains of southern China. In this study, we employed comparative population genomics to study the genetic basis underlying the small body size of DBP breed based on the whole genome sequencing data. To detect genomic signatures of positive selection, we applied three methods based on population comparison, fixation index (FST), cross population composite likelihood ratio (XP-CLR) and nucleotide diversity (θπ), and further analyzed the results to find genomic regions under selection for body size-related traits. Results A number of protein-coding genes in windows with the top 1% values of FST (367 genes), XP-CLR (681 genes), and log2 (θπ ratio) (332 genes) were identified. The most significant signal of positive selection was mapped to the NELL1 gene, probably underlies the body size and development traits, and may also have been selected for short stature in the DBP population. In addition, some other loci on different chromosomes were identified to be potentially involved in the development of body size. Conclusions Results of our study identified some positively selected genes across the horse genome, which are possibly involved in body size traits. These novel candidate genes may be useful targets for clarifying our understanding of the molecular basis of body size and as such they should be of great interest for future research into the genetic architecture of relevant traits in horse breeding program.
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Affiliation(s)
- Hojjat Asadollahpour Nanaei
- Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, PB, 76169-133, Iran
| | - Ali Esmailizadeh
- Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, PB, 76169-133, Iran. .,State Key Laboratory of Genetic Resources and Evolution and Yunnan Laboratory of Molecular Biology of Domestic Animals, Kunming Institute of Zoology, Chinese Academy of Sciences, No. 32 Jiaochang Donglu, Kunming, Yunnan, China.
| | - Ahmad Ayatollahi Mehrgardi
- Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, PB, 76169-133, Iran
| | - Jianlin Han
- CAAS-ILRI Joint Laboratory on Livestock and Forage Genetic Resources, Institute of Animal Science, Chinese Academy of Agricultural Sciences (CAAS), Beijing, China.,Livestock Genetics Program, International Livestock Research Institute (ILRI), Nairobi, Kenya
| | - Dong-Dong Wu
- State Key Laboratory of Genetic Resources and Evolution and Yunnan Laboratory of Molecular Biology of Domestic Animals, Kunming Institute of Zoology, Chinese Academy of Sciences, No. 32 Jiaochang Donglu, Kunming, Yunnan, China.,State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan and Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, China
| | - Yan Li
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan and Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, China.
| | - Ya-Ping Zhang
- State Key Laboratory of Genetic Resources and Evolution and Yunnan Laboratory of Molecular Biology of Domestic Animals, Kunming Institute of Zoology, Chinese Academy of Sciences, No. 32 Jiaochang Donglu, Kunming, Yunnan, China. .,State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan and Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, China.
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Ma J, Guo W, Gao M, Huang B, Qi Q, Ling Z, Chen Y, Hu H, Zhou H, Yu F, Chen K, Richards G, Lin J, Zhou Z, Xiao D, Zou X. Biomimetic matrix fabricated by LMP-1 gene-transduced MC3T3-E1 cells for bone regeneration. Biofabrication 2017; 9:045010. [PMID: 28930090 DOI: 10.1088/1758-5090/aa8dd1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Bone healing is regulated by multiple microenvironmental signals provided by the extracellular matrix (ECM). This study aimed to mimic the native osteoinductive microenvironment by developing an ECM using gene-transduced cells. The LIM mineralization protein-1 (LMP-1) gene was transferred to murine pre-osteoblast cells (MC3T3-E1) using lentiviral vectors. Western blotting assay indicated that the MC3T3-E1 cells expressed an increased level of bone morphologic protein-2, -4 and -7 (BMP-2, -4 and -7) after LMP-1 gene transduction. The transduced cells were then seeded into calcined bovine bone scaffolds and cultured for 7, 14, and 21 days to construct ECMs on the scaffolds. The ECM-scaffold composites were then decellularized using the freeze-drying method. Scaffolds without ECM deposition were used as controls. The composites and controls were implanted into critical-sized bone defects created in the distal femurs of New Zealand rabbits. Twelve weeks after the surgery, both microcomputed tomography and histologic results indicated that the 7-day-cell-modified ECM-scaffold composites induced bone regeneration with significantly larger volume, trabecular thickness and connectivity than the controls. However, the 14- and 21-day-cell-modified ECM-scaffold composites triggered sustained inflammation response even at 12 weeks after the surgery and showed less bone ingrowth and integration than their 7-day-cell-modified counterparts. In conclusion, these results highlight the viable gene transfer techniques for manipulating cells in a constructed microenvironment of ECM for bone regeneration. However, the unresolved inflammation relating to the duration of ECM modification needs to be considered.
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Affiliation(s)
- Junxuan Ma
- Department of Orthopedic, Peking University Shenzhen Hospital, Shenzhen, People's Republic of China. Guangdong Provincial Key Laboratory of Orthopedics and Traumatology, The First Affiliate Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China
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Synergistic effects of BMP-2, BMP-6 or BMP-7 with human plasma fibronectin onto hydroxyapatite coatings: A comparative study. Acta Biomater 2017; 55:481-492. [PMID: 28434979 DOI: 10.1016/j.actbio.2017.04.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 03/20/2017] [Accepted: 04/11/2017] [Indexed: 01/07/2023]
Abstract
Design of new osteoinductive biomaterials to reproduce an optimized physiological environment capable of recruiting stem cells and instructing their fate towards the osteoblastic lineage has become a priority in orthopaedic surgery. This work aims at evaluating the bioactivity of BMP combined with human plasma fibronectin (FN/BMP) delivered in solution or coated onto titanium-hydroxyapatite (TiHA) surfaces. Herein, we focus on the comparison of in vitro osteogenic efficacy in mouse C2C12 pre-osteoblasts of three BMP members, namely: BMP-2, BMP-6 and BMP-7. In parallel, we evaluated the molecular binding strength between each BMP with FN using the Surface Plasmon Resonance (SPR) technology. The affinity of BMPs for FN was found totally different and dependent on BMP type. Indeed, the combination of FN with BMP-2 on TiHA surfaces potentiates the burst of gene-mediated osteogenic induction, while it prolongs the osteogenic activity of BMP-6 and surprisingly annihilates the BMP-7 one. These results correlate with FN/BMP affinity for TiHA, since BMP-6>BMP-2>BMP-7. In addition, by analyzing the osteogenic activity in the peri-implant environment, we showed that osteoinductive paracrine effects were significantly decreased upon (FN/BMP-6), as opposed to (FN/BMP-2) coatings. Altogether, our results support the use of FN/BMP-6 to develop a biomimetic microenvironment capable to induce osteogenic activity under physiological conditions, with minimum paracrine signalization. STATEMENT OF SIGNIFICANCE The originality of our paper relies on the first direct comparison of the in vitro osteogenic potential of three osteogenic BMPs (BMP-2, -6 and -7) combined with native human plasma fibronectin delivered in solution or coated by laser transfer onto titanium hydroxyapatite surfaces. We confirm that BMP association with fibronectin enhances the osteogenic activity of BMP-2, -6 and -7, but with essential discrepancies, depending on the BMP member, and in agreement with the affinity of BMPs for fibronectin. Moreover, we bring elements to explain the origin of the BMP-2 medical life-threatening side-effects by analyzing in vitro paracrine effects. Finally, this work supports the alternative use of FN/BMP-6 to induce osteogenic activity under physiological conditions, with minimum side effects.
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Sánchez-Duffhues G, Hiepen C, Knaus P, Ten Dijke P. Bone morphogenetic protein signaling in bone homeostasis. Bone 2015; 80:43-59. [PMID: 26051467 DOI: 10.1016/j.bone.2015.05.025] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 04/11/2015] [Accepted: 05/20/2015] [Indexed: 01/06/2023]
Abstract
Bone morphogenetic proteins (BMPs) are cytokines belonging to the transforming growth factor-β (TGF-β) superfamily. They play multiple functions during development and tissue homeostasis, including regulation of the bone homeostasis. The BMP signaling pathway consists in a well-orchestrated manner of ligands, membrane receptors, co-receptors and intracellular mediators, that regulate the expression of genes controlling the normal functioning of the bone tissues. Interestingly, BMP signaling perturbation is associated to a variety of low and high bone mass diseases, including osteoporosis, bone fracture disorders and heterotopic ossification. Consistent with these findings, in vitro and in vivo studies have shown that BMPs have potent effects on the activity of cells regulating bone function, suggesting that manipulation of the BMP signaling pathway may be employed as a therapeutic approach to treat bone diseases. Here we review the recent advances on BMP signaling and bone homeostasis, and how this knowledge may be used towards improved diagnosis and development of novel treatment modalities. This article is part of a Special Issue entitled "Muscle Bone Interactions".
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Affiliation(s)
- Gonzalo Sánchez-Duffhues
- Department of Molecular Cell Biology and Cancer Genomics Centre Netherlands, Leiden University Medical Center, The Netherlands
| | - Christian Hiepen
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany; Berlin Brandenburg School of Regenerative Therapies (BSRT), Charité Universitätsmedizin, Berlin, Germany
| | - Petra Knaus
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany; Berlin Brandenburg School of Regenerative Therapies (BSRT), Charité Universitätsmedizin, Berlin, Germany.
| | - Peter Ten Dijke
- Department of Molecular Cell Biology and Cancer Genomics Centre Netherlands, Leiden University Medical Center, The Netherlands.
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Chatakun P, Núñez-Toldrà R, Díaz López EJ, Gil-Recio C, Martínez-Sarrà E, Hernández-Alfaro F, Ferrés-Padró E, Giner-Tarrida L, Atari M. The effect of five proteins on stem cells used for osteoblast differentiation and proliferation: a current review of the literature. Cell Mol Life Sci 2014; 71:113-42. [PMID: 23568025 PMCID: PMC11113514 DOI: 10.1007/s00018-013-1326-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 03/13/2013] [Accepted: 03/14/2013] [Indexed: 01/04/2023]
Abstract
Bone-tissue engineering is a therapeutic target in the field of dental implant and orthopedic surgery. It is therefore essential to find a microenvironment that enhances the growth and differentiation of osteoblasts both from mesenchymal stem cells (MSCs) and those derived from dental pulp. The aim of this review is to determine the relationship among the proteins fibronectin (FN), osteopontin (OPN), tenascin (TN), bone sialoprotein (BSP), and bone morphogenetic protein (BMP2) and their ability to coat different types of biomaterials and surfaces to enhance osteoblast differentiation. Pre-treatment of biomaterials with FN during the initial phase of osteogenic differentiation on all types of surfaces, including slotted titanium and polymers, provides an ideal microenvironment that enhances adhesion, morphology, and proliferation of pluripotent and multipotent cells. Likewise, in the second stage of differentiation, surface coating with BMP2 decreases the diameter and the pore size of the scaffold, causing better adhesion and reduced proliferation of BMP-MSCs. Coating oligomerization surfaces with OPN and BSP promotes cell adhesion, but it is clear that the polymeric coating material BSP alone is insufficient to induce priming of MSCs and functional osteoblastic differentiation in vivo. Finally, TN is involved in mineralization and can accelerate new bone formation in a multicellular environment but has no effect on the initial stage of osteogenesis.
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Affiliation(s)
- P. Chatakun
- Laboratory for Regenerative Medicine, College of Dentistry, Universitat Internacional de Catalunya, C/Josep Trueta s/n, Sant Cugat del Vallès, 08195 Barcelona, Spain
- Police General Hospital, Bangkok, Thailand
| | - R. Núñez-Toldrà
- Laboratory for Regenerative Medicine, College of Dentistry, Universitat Internacional de Catalunya, C/Josep Trueta s/n, Sant Cugat del Vallès, 08195 Barcelona, Spain
- Chair of Regenerative Implantology MIS-UIC, Universitat Internacional de Catalunya, Barcelona, Spain
| | - E. J. Díaz López
- Laboratory for Regenerative Medicine, College of Dentistry, Universitat Internacional de Catalunya, C/Josep Trueta s/n, Sant Cugat del Vallès, 08195 Barcelona, Spain
| | - C. Gil-Recio
- Laboratory for Regenerative Medicine, College of Dentistry, Universitat Internacional de Catalunya, C/Josep Trueta s/n, Sant Cugat del Vallès, 08195 Barcelona, Spain
- Chair of Regenerative Implantology MIS-UIC, Universitat Internacional de Catalunya, Barcelona, Spain
| | - E. Martínez-Sarrà
- Laboratory for Regenerative Medicine, College of Dentistry, Universitat Internacional de Catalunya, C/Josep Trueta s/n, Sant Cugat del Vallès, 08195 Barcelona, Spain
- Chair of Regenerative Implantology MIS-UIC, Universitat Internacional de Catalunya, Barcelona, Spain
| | - F. Hernández-Alfaro
- Surgery and Oral Implantology Department, College of Dentistry, Universitat Internacional de Catalunya, Barcelona, Spain
| | - E. Ferrés-Padró
- Surgery and Oral Implantology Department, College of Dentistry, Universitat Internacional de Catalunya, Barcelona, Spain
- Oral and Maxillofacial Surgery Department, Fundacio Hospital de Nens de Barcelona, Barcelona, Spain
| | - L. Giner-Tarrida
- Laboratory for Regenerative Medicine, College of Dentistry, Universitat Internacional de Catalunya, C/Josep Trueta s/n, Sant Cugat del Vallès, 08195 Barcelona, Spain
- Chair of Regenerative Implantology MIS-UIC, Universitat Internacional de Catalunya, Barcelona, Spain
| | - M. Atari
- Laboratory for Regenerative Medicine, College of Dentistry, Universitat Internacional de Catalunya, C/Josep Trueta s/n, Sant Cugat del Vallès, 08195 Barcelona, Spain
- Chair of Regenerative Implantology MIS-UIC, Universitat Internacional de Catalunya, Barcelona, Spain
- Surgery and Oral Implantology Department, College of Dentistry, Universitat Internacional de Catalunya, Barcelona, Spain
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Bukharova TB, Logovskaya LV, Volkov AV, Garas MN, Vikhrova EB, Logunov DY, Makhnach OV, Shmarov MM, Gol'dshtein DV. Adenoviral transduction of multipotent mesenchymal stromal cells from human adipose tissue with bone morphogenetic protein BMP-2 gene. Bull Exp Biol Med 2013; 156:122-6. [PMID: 24319708 DOI: 10.1007/s10517-013-2294-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We determined conditions for effective transduction of multipotent mesenchymal stromal cells from human adipose tissue with adenoviral constructs carrying the gene of human bone morphogenetic protein BMP-2. The peak of transgene transcription and BMP-2 protein secretion in the transduced cultures was observed on day 6 after infection. The maximum transcription of BMP-2 gene and genes of osteogenic markers (bone sialoprotein, osteopontin, and osteocalcin) was observed in the medium containing sodium β-glycerophosphate and ascorbic acid. Addition of D 3 vitamin did not enhance the expression of BMP-2 gene in transduced cells. The obtained cell cultures with high osteogenic potential can be used in bone tissue engineering.
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Affiliation(s)
- T B Bukharova
- Medical Genetic Research Center, Russian Academy of Medical Sciences; ReMeTeks Company; N. F. Gamaleya Research Institute of Epidemiology and Microbiology, Moscow, Russia.
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Nino-Fong R, McDuffee LA, Esparza Gonzalez BP, Kumar MR, Merschrod S. EF, Poduska KM. Scaffold Effects on Osteogenic Differentiation of Equine Mesenchymal Stem Cells: An In Vitro Comparative Study. Macromol Biosci 2013; 13:348-55. [DOI: 10.1002/mabi.201200355] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Revised: 11/14/2012] [Indexed: 11/10/2022]
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Kim J, Ma T. Bioreactor strategy in bone tissue engineering: pre-culture and osteogenic differentiation under two flow configurations. Tissue Eng Part A 2012; 18:2354-64. [PMID: 22690750 DOI: 10.1089/ten.tea.2011.0674] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Since robust osteogenic differentiation and mineralization are integral to the engineering of bone constructs, understanding the impact of the cellular microenvironments on human mesenchymal stem cell (hMSCs) osteogenic differentiation is crucial to optimize bioreactor strategy. Two perfusion flow conditions were utilized in order to understand the impact of the flow configuration on hMSC construct development during both pre-culture (PC) in growth media and its subsequent osteogenic induction (OI). The media in the in-house perfusion bioreactor was controlled to perfuse either around (termed parallel flow [PF]) the construct surfaces or penetrate through the construct (termed transverse flow [TF]) for 7 days of the PC followed by 7 days of the OI. The flow configuration during the PC not only changed growth kinetics but also influenced cell distribution and potency of osteogenic differentiation and mineralization during the subsequent OI. While shear stress resulted from the TF stimulated cell proliferation during PC, the convective removal of de novo extracellular matrix (ECM) proteins and growth factors (GFs) reduced cell proliferation on OI. In contrast, the effective retention of de novo ECM proteins and GFs in the PC constructs under the PF maintained cell proliferation under the OI but resulted in localized cell aggregations, which influenced their osteogenic differentiation. The results revealed the contrasting roles of the convective flow as a mechanical stimulus, the redistribution of the cells and macromolecules in 3D constructs, and their divergent impacts on cellular events, leading to bone construct formation. The results suggest that the modulation of the flow configuration in the perfusion bioreactor is an effective strategy that regulates the construct properties and maximizes the functional outcome.
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Affiliation(s)
- Junho Kim
- Department of Chemical and Biomedical Engineering, Florida State University, Tallahassee, Florida 32310, USA
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Ruschke K, Hiepen C, Becker J, Knaus P. BMPs are mediators in tissue crosstalk of the regenerating musculoskeletal system. Cell Tissue Res 2012; 347:521-44. [PMID: 22327483 DOI: 10.1007/s00441-011-1283-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 11/10/2011] [Indexed: 12/22/2022]
Abstract
The musculoskeletal system is a tight network of many tissues. Coordinated interplay at a biochemical level between tissues is essential for development and repair. Traumatic injury usually affects several tissues and represents a large challenge in clinical settings. The current demand for potent growth factors in such applications thus accompanies the keen interest in molecular mechanisms and orchestration of tissue formation. Of special interest are multitasking growth factors that act as signals in a variety of cell types, both in a paracrine and in an autocrine manner, thereby inducing cell differentiation and coordinating not only tissue assembly at specific sites but also maturation and homeostasis. We concentrate here on bone morphogenetic proteins (BMPs), which are important crosstalk mediators known for their irreplaceable roles in vertebrate development. The molecular crosstalk during embryonic musculoskeletal tissue formation is recapitulated in adult repair. BMPs act at different levels from the initiation to maturation of newly formed tissue. Interestingly, this is influenced by the spatiotemporal expression of different BMPs, their receptors and co-factors at the site of repair. Thus, the regenerative potential of BMPs needs to be evaluated in the context of highly connected tissues such as muscle and bone and might indeed be different in more poorly connected tissues such as cartilage. This highlights the need for an understanding of BMP signaling across tissues in order to eventually improve BMP regenerative potential in clinical applications. In this review, the distinct members of the BMP family and their individual contribution to musculoskeletal tissue repair are summarized by focusing on their paracrine and autocrine functions.
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Affiliation(s)
- Karen Ruschke
- Institute for Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
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Huang J, Rajagopal R, Liu Y, Dattilo LK, Shaham O, Ashery-Padan R, Beebe DC. The mechanism of lens placode formation: a case of matrix-mediated morphogenesis. Dev Biol 2011; 355:32-42. [PMID: 21540023 DOI: 10.1016/j.ydbio.2011.04.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 03/30/2011] [Accepted: 04/13/2011] [Indexed: 11/29/2022]
Abstract
Although placodes are ubiquitous precursors of tissue invagination, the mechanism of placode formation has not been established and the requirement of placode formation for subsequent invagination has not been tested. Earlier measurements in chicken embryos supported the view that lens placode formation occurs because the extracellular matrix (ECM) between the optic vesicle and the surface ectoderm prevents the prospective lens cells from spreading. Continued cell proliferation within this restricted area was proposed to cause cell crowding, leading to cell elongation (placode formation). This view suggested that continued cell proliferation and adhesion to the ECM between the optic vesicle and the surface ectoderm was sufficient to explain lens placode formation. To test the predictions of this "restricted expansion hypothesis," we first confirmed that the cellular events that accompany lens placode formation in chicken embryos also occur in mouse embryos. We then showed that the failure of lens placode formation when the transcription factor, Pax6 was conditionally deleted in the surface ectoderm was associated with greatly diminished accumulation of ECM between the optic vesicle and ectoderm and reduced levels of transcripts encoding components of the ECM. In accord with the "restricted expansion hypothesis," the Pax6-deleted ectoderm expanded, rather than being constrained to a constant area. As a further test, we disrupted the ECM by deleting Fn1, which is required for matrix assembly and cell-matrix adhesion. As in Pax6(CKO) embryos, the Fn1(CKO) lens ectoderm expanded, rather than being constrained to a fixed area and the lens placode did not form. Ectoderm cells in Fn1(CKO) embryos expressed markers of lens induction and reorganized their cytoskeleton as in wild type ectoderm, but did not invaginate, suggesting that placode formation establishes the minimal mechanical requirements for invagination.
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Affiliation(s)
- Jie Huang
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA
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