1
|
Moore RP, Fogerson SM, Tulu US, Yu JW, Cox AH, Sican MA, Li D, Legant WR, Weigel AV, Crawford JM, Betzig E, Kiehart DP. Super-resolution microscopy reveals actomyosin dynamics in medioapical arrays. Mol Biol Cell 2022; 33:ar94. [PMID: 35544300 DOI: 10.1091/mbc.e21-11-0537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Arrays of actin filaments (F-actin) near the apical surface of epithelial cells (medioapical arrays) contribute to apical constriction and morphogenesis throughout phylogeny. Here, super-resolution approaches (grazing incidence structured illumination, GI-SIM and lattice light sheet, LLSM) microscopy resolve individual, fluorescently labeled F-actin and bipolar myosin filaments that drive amnioserosa cell shape changes during dorsal closure in Drosophila. In expanded cells, F-actin and myosin form loose, apically domed meshworks at the plasma membrane. The arrays condense as cells contract, drawing the domes into the plane of the junctional belts. As condensation continues, individual filaments are no longer uniformly apparent. As cells expand, arrays of actomyosin are again resolved - some F-actin turnover likely occurs, but a large fraction of existing filaments rearrange. In morphologically isotropic cells, actin filaments are randomly oriented and during contraction, are drawn together but remain essentially randomly oriented. In anisotropic cells, largely parallel actin filaments are drawn closer to one another. Our images offer unparalleled resolution of F-actin in embryonic tissue show that medioapical arrays are tightly apposed to the plasma membrane, are continuous with meshworks of lamellar F-actin and thereby constitute modified cell cortex. In concert with other tagged array components, super-resolution imaging of live specimens will offer new understanding of cortical architecture and function. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].
Collapse
Affiliation(s)
- Regan P Moore
- Biology Department, Duke University, Durham, NC, 27708, USA.,Department of Pharmacology, University of North Carolina, Chapel Hill, NC, 27599, USA.,Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill, 27599, USA and North Carolina State University, Raleigh, NC, 27695, USA
| | | | - U Serdar Tulu
- Biology Department, Duke University, Durham, NC, 27708, USA
| | - Jason W Yu
- Biology Department, Duke University, Durham, NC, 27708, USA
| | - Amanda H Cox
- Biology Department, Duke University, Durham, NC, 27708, USA
| | | | - Dong Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wesley R Legant
- Department of Pharmacology, University of North Carolina, Chapel Hill, NC, 27599, USA.,Joint Department of Biomedical Engineering, University of North Carolina, Chapel Hill, 27599, USA and North Carolina State University, Raleigh, NC, 27695, USA
| | - Aubrey V Weigel
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, 20147, USA
| | | | - Eric Betzig
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, 20147, USA.,Departments of Physics and Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA
| | | |
Collapse
|
2
|
Pilawski I, Tulu US, Ticha P, Schüpbach P, Traxler H, Xu Q, Pan J, Coyac BR, Yuan X, Tian Y, Liu Y, Chen J, Erdogan Y, Arioka M, Armaro M, Wu M, Brunski JB, Helms JA. Interspecies Comparison of Alveolar Bone Biology, Part I: Morphology and Physiology of Pristine Bone. JDR Clin Trans Res 2020; 6:352-360. [PMID: 32660303 DOI: 10.1177/2380084420936979] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
INTRODUCTION Few interspecies comparisons of alveolar bone have been documented, and this knowledge gap raises questions about which animal models most accurately represent human dental conditions or responses to surgical interventions. OBJECTIVES The objective of this study was to employ state-of-the-art quantitative metrics to directly assess and compare the structural and functional characteristics of alveolar bone among humans, mini pigs, rats, and mice. METHODS The same anatomic location (i.e., the posterior maxillae) was analyzed in all species via micro-computed tomographic imaging, followed by quantitative analyses, coupled with histology and immunohistochemistry. Bone remodeling was evaluated with alkaline phosphatase activity and tartrate-resistant acid phosphatase staining to identify osteoblast and osteoclast activities. In vivo fluorochrome labeling was used as a means to assess mineral apposition rates. RESULTS Collectively, these analyses demonstrated that bone volume differed among the species, while bone mineral density was equal. All species showed a similar density of alveolar osteocytes, with a highly conserved pattern of collagen organization. Collagen maturation was equal among mouse, rat, and mini pig. Bone remodeling was a shared feature among the species, with morphologically indistinguishable hemiosteonal appearances, osteocytic perilacunar remodeling, and similar mineral apposition rates in alveolar bone. CONCLUSIONS Our analyses demonstrated equivalencies among the 4 species in a plurality of the biological features of alveolar bone. Despite contradictory results from older studies, we found no evidence for the superiority of pig models over rodent models in representing human bone biology. KNOWLEDGE TRANSFER STATEMENT Animal models are extensively used to evaluate bone tissue engineering strategies, yet there are few state-of-the-art studies that rigorously compare and quantify the factors influencing selection of a given animal model. Consequently, there is an urgent need to assess preclinical animal models for their predictive value to dental research. Our article addresses this knowledge gap and, in doing so, provides a foundation for more effective standardization among animal models commonly used in dentistry.
Collapse
Affiliation(s)
- I Pilawski
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - U S Tulu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - P Ticha
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - P Schüpbach
- Schupbach Ltd, Service and Research Laboratory, Thalwil, Switzerland
| | - H Traxler
- Center of Anatomy and Cell Biology, Division of Anatomy, Medical University of Vienna, Vienna, Austria
| | - Q Xu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - J Pan
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - B R Coyac
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - X Yuan
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - Y Tian
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - Y Liu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - J Chen
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - Y Erdogan
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - M Arioka
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA.,Department of Clinical Pharmacology, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - M Armaro
- Nobel Biocare Services AG, Zürich-Flughafen, Switzerland
| | - M Wu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - J B Brunski
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - J A Helms
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| |
Collapse
|
3
|
Kaizawa Y, Leyden J, Behn AW, Tulu US, Franklin A, Wang Z, Abrams G, Chang J, Fox PM. Human Tendon-Derived Collagen Hydrogel Significantly Improves Biomechanical Properties of the Tendon-Bone Interface in a Chronic Rotator Cuff Injury Model. J Hand Surg Am 2019; 44:899.e1-899.e11. [PMID: 30685142 DOI: 10.1016/j.jhsa.2018.11.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 09/10/2018] [Accepted: 11/28/2018] [Indexed: 02/02/2023]
Abstract
PURPOSE Poor healing of the tendon-bone interface (TBI) after rotator cuff (RTC) tears leads to high rates of recurrent tear following repair. Previously, we demonstrated that an injectable, thermoresponsive, type I collagen-rich, decellularized human tendon-derived hydrogel (tHG) improved healing in an acute rat Achilles tendon injury model. The purpose of this study was to investigate whether tHG enhances the biomechanical properties of the regenerated TBI in a rat model of chronic RTC injury and repair. METHODS Tendon hydrogel was prepared from chemically decellularized human cadaveric flexor tendons. Eight weeks after bilateral resection of supraspinatus tendons, repair of both shoulders was performed. One shoulder was treated with a transosseous suture (control group) and the other was treated with a transosseous suture plus tHG injection at the repair site (tHG group). Eight weeks after repair, the TBIs were evaluated biomechanically, histologically, and via micro-computed tomography (CT). RESULTS Biomechanical testing revealed a larger load to failure, higher stiffness, higher energy to failure, larger strain at failure, and higher toughness in the tHG group versus control. The area of new cartilage formation was significantly larger in the tHG group. Micro-CT revealed no significant difference between groups in bone morphometry at the supraspinatus tendon insertion, although the tHG group was superior to the control. CONCLUSIONS Injection of tHG at the RTC repair site enhanced biomechanical properties and increased fibrocartilage formation at the TBI in a chronic injury model. CLINICAL RELEVANCE Treatment of chronic RTC injuries with tHG at the time of surgical treatment may improve outcomes after surgical repair.
Collapse
Affiliation(s)
- Yukitoshi Kaizawa
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Palo Alto, CA; Division of Plastic and Reconstructive Surgery, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA
| | - Jacinta Leyden
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Palo Alto, CA; Division of Plastic and Reconstructive Surgery, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA
| | - Anthony W Behn
- Department of Orthopaedic Surgery, Stanford University School of Medicine, Palo Alto, CA
| | - U Serdar Tulu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Palo Alto, CA
| | - Austin Franklin
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Palo Alto, CA; Division of Plastic and Reconstructive Surgery, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA
| | - Zhen Wang
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Palo Alto, CA; Division of Plastic and Reconstructive Surgery, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA
| | - Geoffrey Abrams
- Department of Orthopaedic Surgery, Stanford University School of Medicine, Palo Alto, CA
| | - James Chang
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Palo Alto, CA; Division of Plastic and Reconstructive Surgery, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA
| | - Paige M Fox
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Palo Alto, CA; Division of Plastic and Reconstructive Surgery, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA.
| |
Collapse
|
4
|
Aghvami M, Brunski JB, Serdar Tulu U, Chen CH, Helms JA. A Thermal and Biological Analysis of Bone Drilling. J Biomech Eng 2019; 140:2682437. [PMID: 30029243 DOI: 10.1115/1.4040312] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Indexed: 11/08/2022]
Abstract
With the introduction of high-speed cutting tools, clinicians have recognized the potential for thermal damage to the material being cut. Here, we developed a mathematical model of heat transfer caused by drilling bones of different densities and validated it with respect to experimentally measured temperatures in bone. We then coupled these computational results with a biological assessment of cell death following osteotomy site preparation. Parameters under clinical control, e.g., drill diameter, rotational speed, and irrigation, along with patient-specific variables such as bone density were evaluated in order to understand their contributions to thermal damage. Predictions from our models provide insights into temperatures and thresholds that cause osteocyte death and that can ultimately compromise stability of an implant.
Collapse
Affiliation(s)
- Maziar Aghvami
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA 94304
| | - John B Brunski
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA 94304
| | - U Serdar Tulu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA 94304
| | - Chih-Hao Chen
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA 94304.,Craniofacial Research Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung University School of Medicine, Taoyuan 33305, Taiwan
| | - Jill A Helms
- Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA 94304 e-mail:
| |
Collapse
|
5
|
Chen CH, Coyac BR, Arioka M, Leahy B, Tulu US, Aghvami M, Holst S, Hoffmann W, Quarry A, Bahat O, Salmon B, Brunski JB, Helms JA. A Novel Osteotomy Preparation Technique to Preserve Implant Site Viability and Enhance Osteogenesis. J Clin Med 2019; 8:jcm8020170. [PMID: 30717291 PMCID: PMC6406409 DOI: 10.3390/jcm8020170] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 01/26/2019] [Accepted: 01/27/2019] [Indexed: 12/27/2022] Open
Abstract
The preservation of bone viability at an osteotomy site is a critical variable for subsequent implant osseointegration. Recent biomechanical studies evaluating the consequences of site preparation led us to rethink the design of bone-cutting drills, especially those intended for implant site preparation. We present here a novel drill design that is designed to efficiently cut bone at a very low rotational velocity, obviating the need for irrigation as a coolant. The low-speed cutting produces little heat and, consequently, osteocyte viability is maintained. The lack of irrigation, coupled with the unique design of the cutting flutes, channels into the osteotomy autologous bone chips and osseous coagulum that have inherent osteogenic potential. Collectively, these features result in robust, new bone formation at rates significantly faster than those observed with conventional drilling protocols. These preclinical data have practical implications for the clinical preparation of osteotomies and alveolar bone reconstructive surgeries.
Collapse
Affiliation(s)
- Chih-Hao Chen
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
- Craniofacial Research Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung University School of Medicine, Taoyuan 33305, Taiwan.
| | - Benjamin R Coyac
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Masaki Arioka
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
- Department of Clinical Pharmacology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
| | - Brian Leahy
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - U Serdar Tulu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Maziar Aghvami
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Stefan Holst
- Nobel Biocare Services AG P.O. Box, CH-8058 Zürich-Flughafen, Switzerland.
- Department of Prosthodontics, School of Dentistry, Johann-Wolfgang Goethe University, Frankfurt, Germany.
| | - Waldemar Hoffmann
- Nobel Biocare Services AG P.O. Box, CH-8058 Zürich-Flughafen, Switzerland.
| | - Antony Quarry
- Nobel Biocare Services AG P.O. Box, CH-8058 Zürich-Flughafen, Switzerland.
| | - Oded Bahat
- Private Practice, Beverly Hills, CA 90210, USA.
| | - Benjamin Salmon
- Paris Descartes-Sorbonne Paris Cité University, EA2496, Montrouge, France.
- Dental Medicine Department, Bretonneau Hospital, HUPNVS, AP-HP, Paris 75018, France.
| | - John B Brunski
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Jill A Helms
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| |
Collapse
|
6
|
Abstract
Osteoporosis is associated with decreased bone density and increased bone fragility, but how this disease affects alveolar bone healing is not clear. The objective of this study was to determine the extent to which osteoporosis affects the jaw skeleton and then to evaluate possible mechanisms whereby an osteoporotic phenotype might affect the rate of alveolar bone healing following tooth extraction. Using an ovariectomized mouse model coupled with micro-computed tomographic imaging, histologic, molecular, and cellular assays, we first demonstrated that the appendicular and jaw skeletons both develop osteoporotic phenotypes. Next, we demonstrated that osteoporotic mice exhibit atrophy of the periodontal ligament (PDL) and that this atrophy was accompanied by a reduction in the pool of osteoprogenitor cells in the PDL. The paucity of PDL-derived osteoprogenitor cells in osteoporotic mice was associated with significantly slower extraction socket healing. Collectively, these analyses demonstrate that the jaw skeleton is susceptible to the untoward effects of osteoporosis that manifest as thinner, more porous alveolar bone, PDL thinning, and slower bone repair. These findings have potential clinical significance for older osteopenic patients undergoing reconstructive procedures.
Collapse
Affiliation(s)
- M Arioka
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA.,2 Department of Clinical Pharmacology, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - X Zhang
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA.,3 State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Z Li
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA.,4 Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | - U S Tulu
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - Y Liu
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA.,3 State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - L Wang
- 3 State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - X Yuan
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| | - J A Helms
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, CA, USA
| |
Collapse
|
7
|
Guo Y, Li D, Zhang S, Yang Y, Liu JJ, Wang X, Liu C, Milkie DE, Moore RP, Tulu US, Kiehart DP, Hu J, Lippincott-Schwartz J, Betzig E, Li D. Visualizing Intracellular Organelle and Cytoskeletal Interactions at Nanoscale Resolution on Millisecond Timescales. Cell 2018; 175:1430-1442.e17. [DOI: 10.1016/j.cell.2018.09.057] [Citation(s) in RCA: 290] [Impact Index Per Article: 48.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 07/21/2018] [Accepted: 09/26/2018] [Indexed: 11/26/2022]
|
8
|
Chen CH, Wang L, Serdar Tulu U, Arioka M, Moghim MM, Salmon B, Chen CT, Hoffmann W, Gilgenbach J, Brunski JB, Helms JA. An osteopenic/osteoporotic phenotype delays alveolar bone repair. Bone 2018; 112:212-219. [PMID: 29704698 DOI: 10.1016/j.bone.2018.04.019] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/10/2018] [Accepted: 04/21/2018] [Indexed: 12/27/2022]
Abstract
Aging is associated with a function decline in tissue homeostasis and tissue repair. Aging is also associated with an increased incidence in osteopenia and osteoporosis, but whether these low bone mass diseases are a risk factor for delayed bone healing still remains controversial. Addressing this question is of direct clinical relevance for dental patients, since most implants are performed in older patients who are at risk of developing low bone mass conditions. The objective of this study was to assess how an osteopenic/osteoporotic phenotype affected the rate of new alveolar bone formation. Using an ovariectomized (OVX) rat model, the rates of tooth extraction socket and osteotomy healing were compared with age-matched controls. Imaging, along with molecular, cellular, and histologic analyses, demonstrated that OVX produced an overt osteoporotic phenotype in long bones, but only a subtle phenotype in alveolar bone. Nonetheless, the OVX group demonstrated significantly slower alveolar bone healing in both the extraction socket, and in the osteotomy produced in a healed extraction site. Most notably, osteotomy site preparation created a dramatically wider zone of dying and dead osteocytes in the OVX group, which was coupled with more extensive bone remodeling and a delay in the differentiation of osteoblasts. Collectively, these analyses demonstrate that the emergence of an osteoporotic phenotype delays new alveolar bone formation.
Collapse
Affiliation(s)
- Chih-Hao Chen
- Craniofacial Research Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung University School of Medicine, Taoyuan 33305, Taiwan; Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Liao Wang
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China
| | - U Serdar Tulu
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Masaki Arioka
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Clinical Pharmacology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Melika Maghazeh Moghim
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; University College London Medical School, University College London, London WC1E 6BT, UK
| | - Benjamin Salmon
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Paris Descartes University - Sorbonne Paris Cité, EA 2496 - Orofacial Pathologies, Imaging and Biotherapies Lab and Dental Medicine Department, Bretonneau Hospital, HUPNVS, AP-HP, Paris, France
| | - Chien-Tzung Chen
- Craniofacial Research Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung University School of Medicine, Taoyuan 33305, Taiwan; Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital at Keelung, Keelung 20401, Taiwan
| | - Waldemar Hoffmann
- Nobel Biocare Services AG P.O. Box, CH-8058 Zürich-Flughafen, Switzerland
| | - Jessica Gilgenbach
- Nobel Biocare Services AG P.O. Box, CH-8058 Zürich-Flughafen, Switzerland
| | - John B Brunski
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jill A Helms
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| |
Collapse
|
9
|
Yuan X, Pei X, Zhao Y, Li Z, Chen CH, Tulu US, Liu B, Van Brunt LA, Brunski JB, Helms JA. Biomechanics of Immediate Postextraction Implant Osseointegration. J Dent Res 2018; 97:987-994. [PMID: 29608868 DOI: 10.1177/0022034518765757] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The aim of this study was to gain insights into the biology and mechanics of immediate postextraction implant osseointegration. To mimic clinical practice, murine first molar extraction was followed by osteotomy site preparation, specifically in the palatal root socket. The osteotomy was positioned such that it removed periodontal ligament (PDL) only on the palatal aspect of the socket, leaving the buccal aspect undisturbed. This strategy created 2 distinct peri-implant environments: on the palatal aspect, the implant was in direct contact with bone, while on the buccal aspect, a PDL-filled gap existed between the implant and bone. Finite element modeling showed high strains on the palatal aspect, where bone was compressed by the implant. Osteocyte death and bone resorption predominated on the palatal aspect, leading to the loss of peri-implant bone. On the buccal aspect, where finite element modeling revealed low strains, there was minimal osteocyte death and robust peri-implant bone formation. Initially, the buccal aspect was filled with PDL remnants, which we found directly provided Wnt-responsive cells that were responsible for new bone formation and osseointegration. On the palatal aspect, which was devoid of PDL and Wnt-responsive cells, adding exogenous liposomal WNT3A created an osteogenic environment for rapid peri-implant bone formation. Thus, we conclude that low strain and high Wnt signaling favor osseointegration of immediate postextraction implants. The PDL harbors Wnt-responsive cells that are inherently osteogenic, and if the PDL tissue is healthy, it is reasonable to preserve this tissue during immediate implant placement.
Collapse
Affiliation(s)
- X Yuan
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA
| | - X Pei
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA.,2 State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, Mainland China
| | - Y Zhao
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA.,3 Department of Oral Basic Science, School of Dentistry, Lanzhou University, Lanzhou, Mainland China
| | - Z Li
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA.,4 Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, Mainland China
| | - C H Chen
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA.,5 Craniofacial Research Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - U S Tulu
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA
| | - B Liu
- 6 Ankasa Regenerative Therapeutics, South San Francisco, CA, USA
| | - L A Van Brunt
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA
| | - J B Brunski
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA
| | - J A Helms
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA.,6 Ankasa Regenerative Therapeutics, South San Francisco, CA, USA
| |
Collapse
|
10
|
Abstract
The objective of our experiments was to identify new therapeutic strategies to stimulate dentin formation in an adult tooth. To address this objective, we evaluated dentin production in 2 acute trauma models: one involving a pulp exposure and the other involving a superficial dentin injury. Molecular, cellular, and histologic analyses revealed that in response to a severe injury, where the pulp is exposed to the oral cavity, cell death is rampant and the repair response initiates from surviving pulp cells and, to a lesser extent, surviving odontoblasts. When an injury is superficial, as in the case of a dentin injury model, then disturbances are largely confined to pulp tissue immediately underneath the damaged dentin tubules. We found that the pulp remained vital and innervated; primary odontoblasts upregulated HIF1α; and the rate of mineralization was significantly increased. A tamoxifen-inducible Axin2CreERT2/+; R26R mTmG/+ reporter strain was then used to demonstrate that a population of long-lived Wnt-responsive odontoblasts, which secreted dentin throughout the life of the animal, were responsible for depositing new dentin in response to a superficial injury. Amplifying Wnt signaling in the pulp stimulates dentin secretion, and in the dentin injury model, we show that a liposomal formulation of human WNT3A protein passes through dentinal tubules and is capable of upregulating Wnt signaling in the pulp. These data provide strong proof of concept for a therapeutic pulp-capping material to stimulate Wnt signaling in odontoblasts and thus improve the pulp repair response.
Collapse
Affiliation(s)
- Y Zhao
- 1 Department of Oral Basic Science, School of Dentistry, Lanzhou University, Lanzhou, China.,2 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA
| | - X Yuan
- 2 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA
| | - B Liu
- 3 Ankasa Regenerative Therapeutics, Inc., South San Francisco, CA, USA
| | - U S Tulu
- 2 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA
| | - J A Helms
- 2 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford, CA, USA.,3 Ankasa Regenerative Therapeutics, Inc., South San Francisco, CA, USA
| |
Collapse
|
11
|
Abstract
Stem cells residing in the periodontal ligament (PDL) support the homeostasis of the periodontium, but their in vivo identity, source(s), and function(s) remain poorly understood. Here, using a lineage-tracing mouse strain, we identified a quiescent Wnt-responsive population in the PDL that became activated in response to tooth extraction. The Wnt-responsive population expanded by proliferation, then migrated from the PDL remnants that remained attached to bundle bone, into the socket. Once there, the Wnt-responsive progeny upregulated osteogenic protein expression, differentiated into osteoblasts, and generated the new bone that healed the socket. Using a liposomal WNT3A protein therapeutic, we showed that a single application at the time of extraction was sufficient to accelerate extraction socket healing 2-fold. Collectively, these data identify a new stem cell population in the intact periodontium that is directly responsible for alveolar bone healing after tooth removal.
Collapse
Affiliation(s)
- X Yuan
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford University, Stanford, CA, USA
| | - X Pei
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford University, Stanford, CA, USA.,2 State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Y Zhao
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford University, Stanford, CA, USA.,3 Department of Oral Basic Science, School of Dentistry, Lanzhou University, Lanzhou, China
| | - U S Tulu
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford University, Stanford, CA, USA
| | - B Liu
- 4 Ankasa Regenerative Therapeutics, South San Francisco, CA, USA
| | - J A Helms
- 1 Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford School of Medicine, Stanford University, Stanford, CA, USA
| |
Collapse
|
12
|
Chen BC, Legant WR, Wang K, Shao L, Milkie DE, Davidson MW, Janetopoulos C, Wu XS, Hammer JA, Liu Z, English BP, Mimori-Kiyosue Y, Romero DP, Ritter AT, Lippincott-Schwartz J, Fritz-Laylin L, Mullins RD, Mitchell DM, Bembenek JN, Reymann AC, Böhme R, Grill SW, Wang JT, Seydoux G, Tulu US, Kiehart DP, Betzig E. Lattice light-sheet microscopy: imaging molecules to embryos at high spatiotemporal resolution. Science 2014; 346:1257998. [PMID: 25342811 DOI: 10.1126/science.1257998] [Citation(s) in RCA: 1094] [Impact Index Per Article: 109.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Although fluorescence microscopy provides a crucial window into the physiology of living specimens, many biological processes are too fragile, are too small, or occur too rapidly to see clearly with existing tools. We crafted ultrathin light sheets from two-dimensional optical lattices that allowed us to image three-dimensional (3D) dynamics for hundreds of volumes, often at subsecond intervals, at the diffraction limit and beyond. We applied this to systems spanning four orders of magnitude in space and time, including the diffusion of single transcription factor molecules in stem cell spheroids, the dynamic instability of mitotic microtubules, the immunological synapse, neutrophil motility in a 3D matrix, and embryogenesis in Caenorhabditis elegans and Drosophila melanogaster. The results provide a visceral reminder of the beauty and the complexity of living systems.
Collapse
Affiliation(s)
- Bi-Chang Chen
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Wesley R Legant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Kai Wang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Lin Shao
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Daniel E Milkie
- Coleman Technologies, Incorporated, Newtown Square, PA 19073, USA
| | - Michael W Davidson
- National High Magnetic Field Laboratory and Department of Biological Science, Florida State University, Tallahassee, FL 32310, USA
| | - Chris Janetopoulos
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA 19104, USA
| | - Xufeng S Wu
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - John A Hammer
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zhe Liu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Brian P English
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Yuko Mimori-Kiyosue
- Optical Image Analysis Unit, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan
| | - Daniel P Romero
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alex T Ritter
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA. Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge CB2 0XY, England, UK
| | - Jennifer Lippincott-Schwartz
- Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lillian Fritz-Laylin
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - R Dyche Mullins
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Diana M Mitchell
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Joshua N Bembenek
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Anne-Cecile Reymann
- Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany. Max Planck Institute for the Physics of Complex Systems, 01307 Dresden, Germany
| | - Ralph Böhme
- Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany. Max Planck Institute for the Physics of Complex Systems, 01307 Dresden, Germany
| | - Stephan W Grill
- Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany. Max Planck Institute for the Physics of Complex Systems, 01307 Dresden, Germany
| | - Jennifer T Wang
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Geraldine Seydoux
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - U Serdar Tulu
- Department of Biology, Duke University, Durham, NC 27708, USA
| | | | - Eric Betzig
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
| |
Collapse
|
13
|
Wells AR, Zou RS, Tulu US, Sokolow AC, Crawford JM, Edwards GS, Kiehart DP. Complete canthi removal reveals that forces from the amnioserosa alone are sufficient to drive dorsal closure in Drosophila. Mol Biol Cell 2014; 25:3552-68. [PMID: 25253724 PMCID: PMC4230616 DOI: 10.1091/mbc.e14-07-1190] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Drosophila's dorsal closure provides an excellent model system with which to analyze biomechanical processes during morphogenesis. During native closure, the amnioserosa, flanked by two lateral epidermal sheets, forms an eye-shaped opening with canthi at each corner. The dynamics of amnioserosa cells and actomyosin purse strings in the leading edges of epidermal cells promote closure, whereas the bulk of the lateral epidermis opposes closure. Canthi maintain purse string curvature (necessary for their dorsalward forces), and zipping at the canthi shortens leading edges, ensuring a continuous epithelium at closure completion. We investigated the requirement for intact canthi during closure with laser dissection approaches. Dissection of one or both canthi resulted in tissue recoil and flattening of each purse string. After recoil and a temporary pause, closure resumed at approximately native rates until slowing near the completion of closure. Thus the amnioserosa alone can drive closure after dissection of one or both canthi, requiring neither substantial purse string curvature nor zipping during the bulk of closure. How the embryo coordinates multiple, large forces (each of which is orders of magnitude greater than the net force) during native closure and is also resilient to multiple perturbations are key extant questions.
Collapse
Affiliation(s)
| | - Roger S Zou
- Department of Biology, Duke University, Durham, NC 27708
| | - U Serdar Tulu
- Department of Biology, Duke University, Durham, NC 27708
| | - Adam C Sokolow
- Department of Physics, Duke University, Durham, NC 27708
| | | | | | | |
Collapse
|
14
|
Roh-Johnson M, Shemer G, Higgins CD, McClellan JH, Werts AD, Tulu US, Gao L, Betzig E, Kiehart DP, Goldstein B. Triggering a cell shape change by exploiting preexisting actomyosin contractions. Science 2012; 335:1232-5. [PMID: 22323741 DOI: 10.1126/science.1217869] [Citation(s) in RCA: 195] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Apical constriction changes cell shapes, driving critical morphogenetic events, including gastrulation in diverse organisms and neural tube closure in vertebrates. Apical constriction is thought to be triggered by contraction of apical actomyosin networks. We found that apical actomyosin contractions began before cell shape changes in both Caenorhabitis elegans and Drosophila. In C. elegans, actomyosin networks were initially dynamic, contracting and generating cortical tension without substantial shrinking of apical surfaces. Apical cell-cell contact zones and actomyosin only later moved increasingly in concert, with no detectable change in actomyosin dynamics or cortical tension. Thus, apical constriction appears to be triggered not by a change in cortical tension, but by dynamic linking of apical cell-cell contact zones to an already contractile apical cortex.
Collapse
Affiliation(s)
- Minna Roh-Johnson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Ma N, Tulu US, Ferenz NP, Fagerstrom C, Wilde A, Wadsworth P. Poleward transport of TPX2 in the mammalian mitotic spindle requires dynein, Eg5, and microtubule flux. Mol Biol Cell 2010; 21:979-88. [PMID: 20110350 PMCID: PMC2836978 DOI: 10.1091/mbc.e09-07-0601] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
TPX2 is a spindle assembly factor that is required for MT assembly near chromosomes. Using photoactivation of fluorescence, we report that TPX2 is transported poleward in the half-spindle. Poleward transport of TPX2 is sensitive to inhibition of dynein or Eg5, and to suppression of MT flux. TPX2 is a Ran-regulated spindle assembly factor that is required for kinetochore fiber formation and activation of the mitotic kinase Aurora A. TPX2 is enriched near spindle poles and is required near kinetochores, suggesting that it undergoes dynamic relocalization throughout mitosis. Using photoactivation, we measured the movement of PA-GFP-TPX2 in the mitotic spindle. TPX2 moves poleward in the half-spindle and is static in the interzone and near spindle poles. Poleward transport of TPX2 is sensitive to inhibition of dynein or Eg5 and to suppression of microtubule flux with nocodazole or antibodies to Kif2a. Poleward transport requires the C terminus of TPX2, a domain that interacts with Eg5. Overexpression of TPX2 lacking this domain induced excessive microtubule formation near kinetochores, defects in spindle assembly and blocked mitotic progression. Our data support a model in which poleward transport of TPX2 down-regulates its microtubule nucleating activity near kinetochores and links microtubules generated at kinetochores to dynein for incorporation into the spindle.
Collapse
Affiliation(s)
- Nan Ma
- University of Massachusetts, Amherst, MA 01003, USA
| | | | | | | | | | | |
Collapse
|
16
|
Rodriguez-Diaz A, Toyama Y, Abravanel DL, Wiemann JM, Wells AR, Tulu US, Edwards GS, Kiehart DP. Actomyosin purse strings: renewable resources that make morphogenesis robust and resilient. HFSP J 2008; 2:220-37. [PMID: 19404432 DOI: 10.2976/1.2955565] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Accepted: 06/16/2008] [Indexed: 01/11/2023]
Abstract
Dorsal closure in Drosophila is a model system for cell sheet morphogenesis and wound healing. During closure two sheets of lateral epidermis move dorsally to close over the amnioserosa and form a continuous epidermis. Forces from the amnioserosa and actomyosin-rich, supracellular purse strings at the leading edges of these lateral epidermal sheets drive closure. Purse strings generate the largest force for closure and occur during development and wound healing throughout phylogeny. We use laser microsurgery to remove some or all of the purse strings from developing embryos. Free edges produced by surgery undergo characteristic responses as follows. Intact cells in the free edges, which previously had no purse string, recoil away from the incision and rapidly assemble new, secondary purse strings. Next, recoil slows, then pauses at a turning point. Following a brief delay, closure resumes and is powered to completion by the secondary purse strings. We confirm that the assembly of the secondary purse strings requires RhoA. We show that alpha-actinin alternates with nonmuscle myosin II along purse strings and requires nonmuscle myosin II for its localization. Together our data demonstrate that purse strings are renewable resources that contribute to the robust and resilient nature of closure.
Collapse
|
17
|
Yang Z, Tulu US, Wadsworth P, Rieder CL. Kinetochore dynein is required for chromosome motion and congression independent of the spindle checkpoint. Curr Biol 2007; 17:973-80. [PMID: 17509882 PMCID: PMC2570756 DOI: 10.1016/j.cub.2007.04.056] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2007] [Revised: 04/26/2007] [Accepted: 04/27/2007] [Indexed: 12/31/2022]
Abstract
During mitosis, the motor molecule cytoplasmic dynein plays key direct and indirect roles in organizing microtubules (MTs) into a functional spindle. At this time, dynein is also recruited to kinetochores, but its role or roles at these organelles remain vague, partly because inhibiting dynein globally disrupts spindle assembly [1-4]. However, dynein can be selectively depleted from kinetochores by disruption of ZW10 [5], and recent studies with this approach conclude that kinetochore-associated dynein (KD) functions to silence the spindle-assembly checkpoint (SAC) [6]. Here we use dynein-antibody microinjection and the RNAi of ZW10 to explore the role of KD in chromosome behavior during mitosis in mammals. We find that depleting or inhibiting KD prevents the rapid poleward motion of attaching kinetochores but not kinetochore fiber (K fiber) formation. However, after kinetochores attach to the spindle, KD is required for stabilizing kinetochore MTs, which it probably does by generating tension on the kinetochore, and in its absence, chromosome congression is defective. Finally, depleting KD reduces the velocity of anaphase chromosome motion by approximately 40%, without affecting the rate of poleward MT flux. Thus, in addition to its role in silencing the SAC, KD is important for forming and stabilizing K fibers and in powering chromosome motion.
Collapse
Affiliation(s)
- Zhenye Yang
- Lab of Cell Growth and Division, Division of Molecular Medicine, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA
| | | | | | | |
Collapse
|
18
|
Tulu US, Fagerstrom C, Ferenz NP, Wadsworth P. Molecular requirements for kinetochore-associated microtubule formation in mammalian cells. Curr Biol 2006; 16:536-41. [PMID: 16527751 PMCID: PMC1500889 DOI: 10.1016/j.cub.2006.01.060] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 01/17/2006] [Accepted: 01/20/2006] [Indexed: 11/30/2022]
Abstract
In centrosome-containing cells, microtubules nucleated at centrosomes are thought to play a major role in spindle assembly. In addition, microtubule formation at kinetochores has also been observed, most recently under physiological conditions in live cells. The relative contributions of microtubule formation at kinetochores and centrosomes to spindle assembly, and their molecular requirements, remain incompletely understood. Using mammalian cells released from nocodazole-induced disassembly, we observed microtubule formation at centrosomes and at Bub1-positive sites on chromosomes. Kinetochore-associated microtubules rapidly coalesced into pole-like structures in a dynein-dependent manner. Microinjection of excess importin-beta or depletion of the Ran-dependent spindle assembly factor, TPX2, blocked kinetochore-associated microtubule formation, enhanced centrosome-associated microtubule formation, but did not prevent chromosome capture by centrosomal microtubules. Depletion of the chromosome passenger protein, survivin, reduced microtubule formation at kinetochores in an MCAK-dependent manner. Microtubule formation in cells depleted of Bub1 or Nuf2 was indistinguishable from that in controls. Our data demonstrate that microtubule assembly at centrosomes and kinetochores is kinetically distinct and differentially regulated. The presence of microtubules at kinetochores provides a mechanism to reconcile the time required for spindle assembly in vivo with that observed in computer simulations of search and capture.
Collapse
Affiliation(s)
- U Serdar Tulu
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Amherst, Massachusetts 01003, USA
| | | | | | | |
Collapse
|
19
|
|
20
|
Salaycik KJ, Fagerstrom CJ, Murthy K, Tulu US, Wadsworth P. Quantification of microtubule nucleation, growth and dynamics in wound-edge cells. J Cell Sci 2005; 118:4113-22. [PMID: 16118246 DOI: 10.1242/jcs.02531] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mammalian cells develop a polarized morphology and migrate directionally into a wound in a monolayer culture. To understand how microtubules contribute to these processes, we used GFP-tubulin to measure dynamic instability and GFP-EB1, a protein that marks microtubule plus-ends, to measure microtubule growth events at the centrosome and cell periphery. Growth events at the centrosome, or nucleation, do not show directional bias, but are equivalent toward and away from the wound. Cells with two centrosomes nucleated approximately twice as many microtubules/minute as cells with one centrosome. The average number of growing microtubules per microm2 at the cell periphery is similar for leading and trailing edges and for cells containing one or two centrosomes. In contrast to microtubule growth, measurement of the parameters of microtubule dynamic instability demonstrate that microtubules in the trailing edge are more dynamic than those in the leading edge. Inhibition of Rho with C3 transferase had no detectable effect on microtubule dynamics in the leading edge, but stimulated microtubule turnover in the trailing edge. Our data demonstrate that in wound-edge cells, microtubule nucleation is non-polarized, in contrast to microtubule dynamic instability, which is highly polarized, and that factors in addition to Rho contribute to microtubule stabilization.
Collapse
Affiliation(s)
- Kimberly J Salaycik
- Department of Biology, Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003, USA
| | | | | | | | | |
Collapse
|
21
|
Piehl M, Tulu US, Wadsworth P, Cassimeris L. Centrosome maturation: measurement of microtubule nucleation throughout the cell cycle by using GFP-tagged EB1. Proc Natl Acad Sci U S A 2004; 101:1584-8. [PMID: 14747658 PMCID: PMC341778 DOI: 10.1073/pnas.0308205100] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding how cells regulate microtubule nucleation during the cell cycle has been limited by the inability to directly observe nucleation from the centrosome. To view nucleation in living cells, we imaged GFP-tagged EB1, a microtubule tip-binding protein, and determined rates of nucleation by counting the number of EB1-GFP comets emerging from the centrosome over time. Nucleation rate increased 4-fold between G(2) and prophase and continued to rise through anaphase and telophase, reaching a maximum of 7 times interphase rates. We tested several models for centrosome maturation, including gamma-tubulin recruitment and increased centrosome size. The centrosomal concentration of gamma-tubulin reached a maximum at metaphase, and centrosome size increased through anaphase, whereas nucleation remained high through telophase, implying the presence of additional regulatory processes. Injection of anti-gamma-tubulin antibodies significantly blocked nucleation during metaphase but was less effective during anaphase, suggesting that a nucleation mechanism independent of gamma-tubulin contributes to centrosome function after metaphase.
Collapse
Affiliation(s)
- Michelle Piehl
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA 18015, USA.
| | | | | | | |
Collapse
|
22
|
Abstract
In centrosome-containing cells, microtubules utilized in spindle formation are thought to be nucleated at the centrosome. However, spindle formation can proceed following experimental destruction of centrosomes or in cells lacking centrosomes, suggesting that non-centrosome-associated microtubules may contribute to spindle formation, at least when centrosomes are absent. Direct observation of prometaphase cells expressing GFP-alpha-tubulin shows that peripheral, non-centrosome-associated microtubules are utilized in spindle formation, even in the presence of centrosomes. Clusters of peripheral microtubules moved into the centrosomal region, demonstrating that a centrosomal microtubule array can be composed of both centrosomally nucleated and peripheral microtubules. Peripheral bundles also moved laterally into the forming spindle between the spindle poles; 3D reconstructions of fixed cells reveal interactions between peripheral and centrosome-associated microtubules. The spindle pole component NuMA and gamma-tubulin were present at the foci of peripheral microtubule clusters, indicating that microtubules moved into the spindle with minus ends leading. Photobleach- and photoactivation-marking experiments of cells expressing GFP-tubulin or a photoactivatable variant of GFP-tubulin, respectively, demonstrate that microtubule motion into the forming spindle results from transport and sliding interactions, not treadmilling. Our results directly demonstrate that non-centrosome-associated microtubules contribute to spindle formation in centrosome-containing cells.
Collapse
Affiliation(s)
- U S Tulu
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst 01003, USA
| | | | | |
Collapse
|
23
|
Rusan NM, Tulu US, Fagerstrom C, Wadsworth P. Reorganization of the microtubule array in prophase/prometaphase requires cytoplasmic dynein-dependent microtubule transport. J Cell Biol 2002; 158:997-1003. [PMID: 12235119 PMCID: PMC2173209 DOI: 10.1083/jcb.200204109] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
When mammalian somatic cells enter mitosis, a fundamental reorganization of the Mt cytoskeleton occurs that is characterized by the loss of the extensive interphase Mt array and the formation of a bipolar mitotic spindle. Microtubules in cells stably expressing GFP-alpha-tubulin were directly observed from prophase to just after nuclear envelope breakdown (NEBD) in early prometaphase. Our results demonstrate a transient stimulation of individual Mt dynamic turnover and the formation and inward motion of microtubule bundles in these cells. Motion of microtubule bundles was inhibited after antibody-mediated inhibition of cytoplasmic dynein/dynactin, but was not inhibited after inhibition of the kinesin-related motor Eg5 or myosin II. In metaphase cells, assembly of small foci of Mts was detected at sites distant from the spindle; these Mts were also moved inward. We propose that cytoplasmic dynein-dependent inward motion of Mts functions to remove Mts from the cytoplasm at prophase and from the peripheral cytoplasm through metaphase. The data demonstrate that dynamic astral Mts search the cytoplasm for other Mts, as well as chromosomes, in mitotic cells.
Collapse
Affiliation(s)
- Nasser M Rusan
- Department of Biology, Program in Molecular and Cellular Biology, Morrill Science Center, University of Massachusetts, N. Pleasant Street, Amherst, MA 01003, USA
| | | | | | | |
Collapse
|