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Full-Text Articles in Polymer Science
Characterization Of The Cellular Origin Of A Tissue-Engineered Human Phalanx Model By In Situ Hybridization, William Landis
Characterization Of The Cellular Origin Of A Tissue-Engineered Human Phalanx Model By In Situ Hybridization, William Landis
William J. Landis
Tissue-engineered models of human phalanges have previously been fabricated from a combination of bovine periosteum, cartilage, tendon, and biodegradable polyglycolic acid and poly-L-lactic acid scaffolds. Resulting constructs implanted in athymic mice for more than 40 weeks developed new bone, cartilage, and tendon and became vascularized, but cell types comprising the constructs were unidentified. The origin of cells in middle phalanx models implanted for 20 weeks in nude mice has been studied by in situ hybridization analyzing species-specific gene expression. Oligonucleotide probes homologous to species-specific gene sequences of bovine type II and X collagen, aggrecan, bone sialoprotein, biglycan, and osteopontin, and …
Tissue-Engineered Meniscal Constructs, William Landis
Tissue-Engineered Meniscal Constructs, William Landis
William J. Landis
The medial and lateral menisci play important roles in knee biomechanics, kinematics, and stability. Unfortunately, these structures are prone to damage and, because of a tenuous blood supply, have great difficulty healing. Many interventions have been proposed for treatment of damaged meniscal tissue, but most surgical options are fraught with difficulties, from continued osteoarthritic degeneration to potential for disease transmission. The field of tissue engineering has made wide inroads into constructing meniscal tissue. Investigations involving collagenous tissue, meniscal fibrochondrocytes, chondrocytes, synthetic scaffolds, and gene therapy have all been reported in the literature. Despite these advances, however, more work needs to …
The Fine Structure Of The Developing Pelvic Fin Dermal Skeleton In The Trout Salmo Gairdneri, William Landis
The Fine Structure Of The Developing Pelvic Fin Dermal Skeleton In The Trout Salmo Gairdneri, William Landis
William J. Landis
The morphogenetic and ultrastructural features of the dermal skeleton in the pelvic fin bud of a teleost, the rainbow trout Salmo gairdneri, have been examined by light and electron microscopy. The principal structural components observed are lepidotrichia and actinotrichia. Lepidotrichia consist of two parallel and symmetrical bony demirays that form jointed segments within the fin. The demirays calcify in a proximodistal direction within the extracellular collagen network of the basal lamella belonging to the epidermal-dermal interface of the fin. Needle- and plate-like particles of a solid mineral phase appear to be associated with the collagen fibrils and with a fine, …
Comparison Of Different Chondrocytes For Use In Tissue Engineering Of Cartilage Model Structures, William Landis
Comparison Of Different Chondrocytes For Use In Tissue Engineering Of Cartilage Model Structures, William Landis
William J. Landis
This study compares bovine chondrocytes harvested from four different animal locations--nasoseptal, articular, costal, and auricular--for tissue-engineered cartilage modeling. While the work serves as a preliminary investigation for fabricating a human ear model, the results are important to tissue- engineered cartilage in general. Chondrocytes were cultured and examined to determine relative cell proliferation rates, type II collagen and aggrecan gene expression, and extracellular matrix production. Respective chondrocytes were then seeded onto biodegradable poly(L-lactide-epsilon-caprolactone) disc-shaped scaffolds. Cell-copolymer constructs were cultured and subsequently implanted in the subcutaneous space of athymic mice for up to 20 weeks. Neocartilage development in harvested constructs was assessed …
Viscoelasticity, Energy Storage, And Transmission And Dissipation By Extracellular Matrices In Vertebrates, William Landis
Viscoelasticity, Energy Storage, And Transmission And Dissipation By Extracellular Matrices In Vertebrates, William Landis
William J. Landis
The extracellular matrix (ECM) of vertebrates is an important biological mechanotransducer that prevents premature mechanical failure of tissues and stores and transmits energy created by muscular deformation. It also transfers large amounts of excess energy to muscles for dissipation as heat, and in some cases, the ECM itself dissipates energy locally. Beyond these functions, ECMs regulate their size and shape as a result of the changing external loads. Changes in tissue metabolism are transduced into increases or decreases in synthesis and catabolism of the components of ECMs. Viscoelasticity is an important feature of the mechanical behavior of ECMs. This parameter, …
Development Of Bone And Cartilage In Tissue-Engineered Human Middle Phalanx Models, William Landis
Development Of Bone And Cartilage In Tissue-Engineered Human Middle Phalanx Models, William Landis
William J. Landis
Human middle phalanges were tissue-engineered with midshaft scaffolds of poly(L-lactide-epsilon-caprolactone) [P(LA-CL)], hydroxyapatite-P(LA-CL), or beta-tricalcium phosphate-P(LA-CL) and end plate scaffolds of bovine chondrocyte-seeded polyglycolic acid. Midshafts were either wrapped with bovine periosteum or left uncovered. Constructs implanted in nude mice for up to 20 weeks were examined for cartilage and bone development as well as gene expression and protein secretion, which are important in extracellular matrix (ECM) formation and mineralization. Harvested 10- and 20-week constructs without periosteum maintained end plate cartilage but no growth plate formation. They also consisted of chondrocytes secreting type II collagen and proteoglycan, and they were composed …
Gene Expression In Slipped Capital Femoral Epiphysisevaluation With Laser Capture Microdissection And Quantitative Reverse Transcription-Polymerase Chain Reaction, William Landis
William J. Landis
BACKGROUND: Slipped capital femoral epiphysis is a poorly understood condition affecting adolescents. Prior studies have suggested that the etiology may be related to abnormal collagen in the growth plate cartilage, but we are not aware of any investigations analyzing collagen or other structural proteins on a molecular level in the affected tissue. This study was performed to evaluate expression of mRNA for key structural molecules in growth plate chondrocytes of patients with slipped capital femoral epiphysis. METHODS: A core biopsy of the proximal femoral physis was performed in nine patients with slipped capital femoral epiphysis, and the specimens were compared …
Mineral Deposition In The Extracellular Matrices Of Vertebrate Tissues: Identification Of Possible Apatite Nucleation Sites On Type I Collagen, William Landis
Mineral Deposition In The Extracellular Matrices Of Vertebrate Tissues: Identification Of Possible Apatite Nucleation Sites On Type I Collagen, William Landis
William J. Landis
The possible means by which type I collagen may mediate mineralization in normal vertebrate bone, tendon, dentin and cementum as well as in pathological mineral formation are not fully understood. One consideration in this regard is that the structure of the protein is somehow important in binding calcium and phosphate ions in a stereochemical configuration conducive to nucleation of apatite crystals. In the present study, type I collagen, packed in a quarter-staggered arrangement in two dimensions and a quasi-hexagonal model of microfibrillar assembly in three dimensions, has been examined in terms of several of its charged amino acid residues. These …
Histochemical Analyses Of Tissue-Engineered Human Menisci, William Landis
Histochemical Analyses Of Tissue-Engineered Human Menisci, William Landis
William J. Landis
The field of tissue engineering remains one of the least explored areas of current meniscal research but holds great promise. In this investigation, meniscal fibrochondrocytes were isolated from fresh human meniscal tissue and seeded onto synthetic polyglycolic acid (PGA) scaffolds. Constructs were implanted into the dorsal subcutaneous space of athymic nude mice. Control scaffolds, devoid of meniscal cells, were simultaneously implanted in additional mice. Constructs were harvested over 12 weeks and treated with a variety of histochemical stains to analyze general specimen morphology, cellular viability and proliferation, and collagen secretion. Results indicate that meniscal fibrochondrocyte proliferation increased over the time …
A Contribution With Review To The Description Of Mineralization Of Bone And Other Calcified Tissues In Vivo, William Landis
A Contribution With Review To The Description Of Mineralization Of Bone And Other Calcified Tissues In Vivo, William Landis
William J. Landis
This manuscript considers certain aspects of mineral deposition in bone and other vertebrate calcifying tissues in order to examine physical, chemical, and biological factors important in the mineralization process. The paper in a discussion format principally presents a new data and the formulation of concepts based on such data as well as a summary of background material as necessary review. Mineralization is found to occur at spatially independent sites throughout the organic extracellular tissue matrices. Matrix vesicles and collagen fibrils each may serve as independent nucleation centers for mineral with vesicle mineralization being local and collagen mineralization dominating the tissues …
Analysis Of Human Osteoarthritic Connective Tissue By Laser Capture Microdissection And Qrt-Pcr, William Landis
Analysis Of Human Osteoarthritic Connective Tissue By Laser Capture Microdissection And Qrt-Pcr, William Landis
William J. Landis
Gene expression levels for type II collagen and aggrecan have been determined as potential measures and disease markers of human osteoarthritis in patients undergoing total knee arthroplasty. In this regard, specimens of affected articular cartilage obtained intraoperatively at the time of surgery were placed in RNAlater(TM) to maintain RNA integrity and subsequently frozen-sectioned. Individual or small numbers of chondrocytes were isolated by laser capture microdissection and their total RNA was extracted and analyzed by quantitative reverse transcription-polymerase chain reaction. Results indicate that type II collagen and aggrecan mRNA expression from specific cells in osteoarthritic tissues are detectable and reproducible using …
A Study In Vivo Of The Effects Of A Static Compressive Load On The Proximal Tibial Physis In Rabbits, William Landis
A Study In Vivo Of The Effects Of A Static Compressive Load On The Proximal Tibial Physis In Rabbits, William Landis
William J. Landis
BACKGROUND: The effect of compression on the physis is generally defined by the Hueter-Volkmann principle, in which decreased linear growth of the physis results from increased compression. This investigation examined whether mechanically induced compression of rabbit physes causes changes in gene expression, cells, and extracellular components that promote physeal resilience and strength (type-II collagen and aggrecan) and cartilage hypertrophy (type-X collagen and matrix metalloprotease-13). METHODS: Static compressive loads (10 N or 30 N) were applied for two or six weeks across one hind limb proximal tibial physis of thirteen-week-old female New Zealand White rabbits (n = 18). The contralateral hind …
Non-Destructive Studies Of Tissue-Engineered Phalanges By Magnetic Resonance Microscopy And X-Ray Microtomography, William Landis
Non-Destructive Studies Of Tissue-Engineered Phalanges By Magnetic Resonance Microscopy And X-Ray Microtomography, William Landis
William J. Landis
One of the intents of tissue engineering is to fabricate biological materials for the augmentation or replacement of impaired, damaged, or diseased human tissue. In this context, novel models of the human phalanges have been developed recently through suturing of polymer scaffolds supporting osteoblasts, chondrocytes, and tenocytes to mimic bone, cartilage, and tendon, respectively. Characterization of the model constructs has been accomplished previously through histological and biochemical means, both of which are necessarily destructive to the constructs. This report describes the application of two complementary, non-destructive, non-invasive techniques, magnetic resonance microscopy (MRM) and X-ray microtomography (XMT or quantitative computed tomography), …
Organization And Development Of The Mineral Phase During Early Ontogenesis Of The Bony Fin Rays Of The Trout Oncorhynchus Mykiss, William Landis
Organization And Development Of The Mineral Phase During Early Ontogenesis Of The Bony Fin Rays Of The Trout Oncorhynchus Mykiss, William Landis
William J. Landis
Characterization of mineral deposition has been studied by electron optical methods during early ontogenesis of lepidotrichia, the bony fin rays, of the trout Oncorhynchus mykiss (the former Salmo gairdneri). The fin rays consist of an extracellular granular ground substance containing in part a network of collagen fibrils within the basal lamella of the fin dermoepidermal interface. Growth of individual rays proceeds in a proximodistal direction. The mineral phase appears as electron-dense needle or plate-like particles and is associated with the collagenous matrix. On analysis of progressively maturing tissue, the mineral was characterized as a poorly crystalline hydroxyapatite with Ca/P molar …
An Overview Of Vertebrate Mineralization With Emphasis On Collagen-Mineral Interaction, William Landis
An Overview Of Vertebrate Mineralization With Emphasis On Collagen-Mineral Interaction, William Landis
William J. Landis
The nucleation, growth, and development of mineral crystals through their interaction principally with collagen in normal bone and calcifying tendon have been elaborated by applying a number of different techniques for analysis of the inorganic and organic constituents of these tissues. The methods have included conventional and high voltage electron microscopy, electron diffraction, microscopic tomography and 3D image reconstruction, and atomic force microscopy. This summary presents results of these studies that have now characterized the size, shape, and aspects of the chemical nature of the crystals as well as their orientation, alignment, location, and distribution with respect to collagen. These …
Collagen As A Scaffold For Biomimetic Mineralization Of Vertebrate Tissues, William Landis
Collagen As A Scaffold For Biomimetic Mineralization Of Vertebrate Tissues, William Landis
William J. Landis
Collagen is a well known protein component that has the capacity to mineralize in a variety of vertebrate tissues. In its mineralized form, collagen potentially can be utilized as a biomimetic material for a variety of applications, including, for example, the augmentation and repair of damaged, congenitally defective, diseased or otherwise impaired calcified tissues such as bone and cartilage. In order to effect an optimal response in this regard, the manner in which collagen becomes mineralized is critically important to understand. This paper provides details concerning collagen–mineral interaction and its implications with respect to designing biomimetic mineralizing collagen that will …
Expression And Ultrastructural Immunolocalization Of A Major 66 Kda Phosphoprotein Synthesized By Chicken Osteoblasts During Mineralization In Vitro, William Landis
William J. Landis
Embryonic chicken osteoblasts cultured over a 30 day period were used as a model system for studying the expression of bone phosphoproteins during cellular differentiation and the possible role of these proteins in extracellular matrix mineralization. Accumulation of total phosphoprotein in the cultures, as determined by O-phosphoserine (Ser-P) and O-phosphothreonine (Thr-P) amino acid analysis, revealed a greater than 10-fold increase over the 30 day period. Total phosphoprotein synthesis, as assessed by (32P)-, (3H)-Ser-P, and (14C)-Thr-P protein labeling, showed the highest levels concurrent with initial mineral deposition within the matrix. The major phosphoprotein present in chicken bones and synthesized by the …
Evaluation Of Bioreactor-Cultivated Bone By Magnetic Resonance Microscopy And Ftir Microspectroscopy, William Landis
Evaluation Of Bioreactor-Cultivated Bone By Magnetic Resonance Microscopy And Ftir Microspectroscopy, William Landis
William J. Landis
We present a three-dimensional mineralizing model based on a hollow fiber bioreactor (HFBR) inoculated with primary osteoblasts isolated from embryonic chick calvaria. Using non-invasive magnetic resonance microscopy (MRM), the growth and development of the mineralized tissue around the individual fibers were monitored over a period of 9 weeks. Spatial maps of the water proton MRM properties of the intact tissue, with 78 microm resolution, were used to determine changes in tissue composition with development. Unique changes in the mineral and collagen content of the tissue were detected with high specificity by proton density (PD) and magnetization transfer ratio (MTR) maps, …
Experiments With Osteoblasts Cultured Under Hypergravity Conditions, William Landis
Experiments With Osteoblasts Cultured Under Hypergravity Conditions, William Landis
William J. Landis
To understand further the role of gravity in osteoblast attachment, osteoblasts were subjected to hypergravity conditions in vitro. Scanning electron microscopy of all confluent coverslips from FPA units show that the number of attached osteoblasts was similar among gravitational levels and growth durations (~90 cells/microscopic field). Specifically, confluent 1.0 G control cultures contained an average of 91 +/- 8 cells/field, 3.3 G samples had 88 +/- 8 cells/field, and 4.0 G cultures averaged 90 +/- 7 cells/field. The sparsely plated cultures assessed by immunohistochemistry also had similar numbers of cells at each time point (l.0 G was similar to 3.3 …
The Potential Of Tissue Engineering In Orthopedics, William Landis
The Potential Of Tissue Engineering In Orthopedics, William Landis
William J. Landis
This article presents models of human phalanges and small joints developed by tissue engineering. Biodegradable polymer scaffolds support growth of osteoblasts, chondrocytes, and tenocytes after implantation of the models in athymic mice. The cell-polymer constructs are vascularized by the host mice, form new bone, cartilage, and tendon with characteristic gene expression and protein synthesis and secretion, and maintain the shape of human phalanges with joints. The study demonstrates critical progress in the design and fabrication of bone, cartilage, and tendon by tissue engineering and the potential of this field for human clinical orthopedic applications.
Tissue Engineering Models Of Human Digits: Effect Of Periosteum On Growth Plate Cartilage Development, William Landis
Tissue Engineering Models Of Human Digits: Effect Of Periosteum On Growth Plate Cartilage Development, William Landis
William J. Landis
Tissue-engineered middle phalanx constructs of human digits were investigated to determine whether periosteum wrapped partly about model midshafts mediated cartilage growth plate formation. Models were fabricated by suturing ends of polymer midshafts in a human middle phalanx shape with polymer sheets seeded with heterogeneous chondrocyte populations from bovine articular cartilage. Half of each midshaft length was wrapped with bovine periosteum. Constructs were cultured, implanted in nude mice for up to 20 weeks, harvested and treated histologically to assess morphology and cartilage proteoglycans. After 20 weeks of implantation, chondrocyte-seeded sheets adjacent to periosteum-wrapped midshaft halves established cartilage growth plates resembling normal …
Design And Assessment Of A Tissue-Engineered Model Of Human Phalanges And A Small Joint, William Landis
Design And Assessment Of A Tissue-Engineered Model Of Human Phalanges And A Small Joint, William Landis
William J. Landis
OBJECTIVES: To develop models of human phalanges and small joints by suturing different cell-polymer constructs that are then implanted in athymic (nude) mice. DESIGN: Models consisted of bovine periosteum, cartilage, and/or tendon cells seeded onto biodegradable polymer scaffolds of either polyglycolic acid (PGA) or copolymers of PGA and poly-L-lactic acid (PLLA) or poly-epsilon-caprolactone (PCL) and PLLA. Constructs were fabricated to produce a distal phalanx, middle phalanx, or distal interphalangeal joint. SETTING AND SAMPLE POPULATION: Studies of more than 250 harvested implants were conducted at the Northeastern Ohio Universities College of Medicine. EXPERIMENTAL VARIABLE: Polymer scaffold, cell type, and implantation time …
Tissue Engineering A Model For The Human Ear: Assessment Of Size, Shape, Morphology, And Gene Expression Following Seeding Of Different Chondrocytes, William Landis
William J. Landis
This study examines the tissue engineering of a human ear model through use of bovine chondrocytes isolated from four different cartilaginous sites (nasoseptal, articular, costal, and auricular) and seeded onto biodegradable poly(l-lactic acid) and poly(L-lactide-epsilon-caprolactone) (50 : 50) polymer ear-shaped scaffolds. After implantation in athymic mice for up to 40 weeks, cell/scaffold constructs were harvested and analyzed in terms of size, shape, histology, and gene expression. Gross morphology revealed that all the tissue-engineered cartilages retained the initial human auricular shape through 40 weeks of implantation. Scaffolds alone lost significant size and shape over the same period. Quantitative reverse transcription-polymerase chain …
Analysis Of Connective Tissues By Laser Capture Microdissection And Reverse Transcriptase-Polymerase Chain Reaction, William Landis
Analysis Of Connective Tissues By Laser Capture Microdissection And Reverse Transcriptase-Polymerase Chain Reaction, William Landis
William J. Landis
Studies of gene expression from bone, cartilage, and other tissues are complicated by the fact that their RNA, collected and pooled for analysis, often represents a wide variety of composite cells distinct in individual phenotype, age, and state of maturation. Laser capture microdissection (LCM) is a technique that allows specific cells to be isolated according to their phenotype, condition, or other marker from within such heterogeneity. As a result, this approach can yield RNA that is particular to a subset of cells comprising the total cell population of the tissue. This study reports the application of LCM to the gene …
Paper 048: Evaluation Of Gene Expression In Slipped Capital Femoral Epiphysis Utilizing Laser Capture Microdissection And Rt-Pcr, William Landis
Paper 048: Evaluation Of Gene Expression In Slipped Capital Femoral Epiphysis Utilizing Laser Capture Microdissection And Rt-Pcr, William Landis
William J. Landis
Purpose: Slipped capital femoral epiphysis (SCFE) is a poorly understood condition impacting adolescents. Its consequences can be severe, even where there is early recognition and treatment is implemented. Prior studies have suggested that the etiology may be related to abnormal collagen comprising the growth plate cartilage, but no investigations have analyzed collagen or other structural proteins on a molecular level in the affected tissue. This study evaluates expression of mRNA for key structural proteins obtained from growth plate chondrocytes of patients suffering SCFE. Method: The work utilizes laser capture microdissection (LCM) techniques followed by reverse transcription polymerase chain reaction (RT-PCR) …