Modeling Inter-Lamellar Interactions in Angle-Ply Nanofibrous Biologic Laminates for Annulus Fibrosus Tissue Engineering

Function of the annulus fibrosus (AF) of the intervertebral disc is predicated on a high degree of structural organization over multiple length scales. Recently, we have employed aligned electrospun scaffolds to engineer nanofibrous biologic laminates that replicate the form and function of the AF [1]. Further, we determined that interlamellar shearing — a direct consequence of the +/−30° angle-ply architecture — plays an important role in reinforcing the tensile response of these materials (Fig. 1). Although we have utilized fiber-reinforced continuum models to characterize the evolving mechanics of single-lamellar AF constructs with in vitro culture [2, 3], these models are not capable of capturing the interlamellar interactions observed in bi-lamellar constructs. Indeed, continuum models of the native AF typically do not account for the organization of fiber populations into discrete, alternating planes of alignment, and so these models, too, do not account for inter-lamellar shearing interactions [4–6]. Therefore, in the present work we propose a novel constitutive model for the reinforcing role of interlamellar shearing during uniaxial extension of angle-ply biologic laminates and employ this model to evaluate the functional evolution of bilayers for AF tissue engineering.

Mesenchymal Stem Cell Seeded Nanofibrous Laminates Mimic the Multi-Scale Form and Function of the Annulus Fibrosus

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206812 ◽

2009 ◽

Author(s):

Nandan K. Nerurkar ◽

Sounok Sen ◽

Emily E. Wible ◽

Jeffrey B. Stambough ◽

Dawn M. Elliott ◽

...

Keyword(s):

Annulus Fibrosus ◽

Form And Function ◽

Multi Scale ◽

Aligned Arrays ◽

Tensile Response ◽

Nanofibrous Scaffolds ◽

Multiple Length Scales ◽

Spine Function ◽

And Function ◽

The annulus fibrosus (AF) of the intervertebral disc is a multi-lamellar fibrocartilage that, together with the nucleus pulposus, confers mechanical support and flexibility to the spine. Function of the AF is predicated on a high degree of structural organization over multiple length scales: aligned collagen fibers reside within each lamella, and the direction of alignment alternates between adjacent lamellae from +30° to −30° with respect to the transverse axis of the spine. Electrospinning permits fabrication of scaffolds consisting of aligned arrays of nanofibers, and has proven effective for directing the alignment of both cells and extracellular matrix (ECM) deposition [1–3]. We recently employed electrospinning to engineer the primary functional unit of the AF, a single lamella [4]. However, it remains a challenge to engineer a multi-lamellar tissue that replicates the cross-ply fiber architecture of the native AF. Moreover, relatively few studies have considered functional properties of engineered AF, and, when measured, tensile properties of these constructs have been inferior to native AF [4]. In this study, mesenchymal stem cells (MSCs) were seeded onto aligned nanofibrous scaffolds organized into bi-lamellar constructs with opposing or parallel fiber orientations, and their functional maturation was evaluated with time. Additionally, we determined a novel role for inter-lamellar ECM in reinforcing the tensile response of bilayers, and confirmed this mechanism by testing acellular bilayers with controllable interface properties.

Herbaceous monocot plant form and function along a tropical rain-forest light gradient: a reversal of dicot strategy

Journal of Tropical Ecology ◽

10.1017/s0266467408005567 ◽

2009 ◽

Vol 25 (1) ◽

pp. 103-106 ◽

Cited By ~ 4

Author(s):

Nathan G. Swenson

Keyword(s):

Tropical Forests ◽

Environmental Gradients ◽

Plant Performance ◽

Seed Plants ◽

Form And Function ◽

Light Gradient ◽

Whole Plant ◽

Plant Form ◽

And Function ◽

Whole plant form and function vary spectacularly across the seed plants. In recent years, plant evolutionary ecologists have begun to document this diversity on large geographic scales by analysing ‘functional traits’ that are indicative of whole plant performance across environmental gradients (Swenson & Enquist 2007, Wright et al. 2004). Despite the high degree of functional diversity in tropical forests, convergence in function does occur locally along successional or light gradients (Bazzaz & Pickett 1980, Swaine & Whitmore 1988).

The NKCC1 antagonist bumetanide mitigates interneuronopathy associated with ethanol exposure in utero

eLife ◽

10.7554/elife.48648 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 1

Author(s):

Alexander GJ Skorput ◽

Stephanie M Lee ◽

Pamela WL Yeh ◽

Hermes H Yeh

Keyword(s):

Prefrontal Cortex ◽

Cortical Neurons ◽

Fetal Alcohol Spectrum Disorders ◽

Behavioral Flexibility ◽

Ethanol Exposure ◽

Embryonic Mouse ◽

Form And Function ◽

Tangential Migration ◽

Prenatal exposure to ethanol induces aberrant tangential migration of corticopetal GABAergic interneurons, and long-term alterations in the form and function of the prefrontal cortex. We have hypothesized that interneuronopathy contributes significantly to the pathoetiology of fetal alcohol spectrum disorders (FASD). Activity-dependent tangential migration of GABAergic cortical neurons is driven by depolarizing responses to ambient GABA present in the cortical enclave. We found that ethanol exposure potentiates the depolarizing action of GABA in GABAergic cortical interneurons of the embryonic mouse brain. Pharmacological antagonism of the cotransporter NKCC1 mitigated ethanol-induced potentiation of GABA depolarization and prevented aberrant patterns of tangential migration induced by ethanol in vitro. In a model of FASD, maternal bumetanide treatment prevented interneuronopathy in the prefrontal cortex of ethanol exposed offspring, including deficits in behavioral flexibility. These findings position interneuronopathy as a mechanism of FASD symptomatology, and posit NKCC1 as a pharmacological target for the management of FASD.

The cardiac nanoenvironment: form and function at the nanoscale

Biophysical Reviews ◽

10.1007/s12551-021-00834-5 ◽

2021 ◽

Author(s):

Jashan P. Singh ◽

Jennifer L. Young

Keyword(s):

Large Scale ◽

New Materials ◽

Length Scales ◽

Form And Function ◽

Molecular Features ◽

Wide Range ◽

Physiological Homeostasis ◽

Organ Level ◽

AbstractMechanical forces in the cardiovascular system occur over a wide range of length scales. At the whole organ level, large scale forces drive the beating heart as a synergistic unit. On the microscale, individual cells and their surrounding extracellular matrix (ECM) exhibit dynamic reciprocity, with mechanical feedback moving bidirectionally. Finally, in the nanometer regime, molecular features of cells and the ECM show remarkable sensitivity to mechanical cues. While small, these nanoscale properties are in many cases directly responsible for the mechanosensitive signaling processes that elicit cellular outcomes. Given the inherent challenges in observing, quantifying, and reconstituting this nanoscale environment, it is not surprising that this landscape has been understudied compared to larger length scales. Here, we aim to shine light upon the cardiac nanoenvironment, which plays a crucial role in maintaining physiological homeostasis while also underlying pathological processes. Thus, we will highlight strategies aimed at (1) elucidating the nanoscale components of the cardiac matrix, and (2) designing new materials and biosystems capable of mimicking these features in vitro.

The influence of radiomimetic substances on deoxyribonucleic acid synthesis and function studied in Escherichia coli / phage systems - III. Mutation of T 2 bacteriophage as a consequence of alkylation in vitro : the uniqueness of ethylation

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1959.0038 ◽

1959 ◽

Vol 150 (941) ◽

pp. 497-508 ◽

Cited By ~ 46

Keyword(s):

Escherichia Coli ◽

Burst Size ◽

Alkylating Agents ◽

Direct Consequence ◽

Acid Synthesis ◽

Deoxyribonucleic Acid Synthesis ◽

Methane Sulphonate ◽

Average Burst Size ◽

Of a comprehensive set of alkylating agents tested, only two, namely, ethyl methane sulphonate and diethyl sulphate, have been found so to interact with T 2 bacteriophage that cells of Escherichia coli , infected with phage treated extracellularly, manifest a considerably increased likelihood of yielding mutated phage. Since this increase can occur where the infective titre of the phage and the latent period and average burst size of the infected bacteria remain unchanged, it is considered that the increased mutation rate is a direct consequence of the chemical treatment, although the alkylation itself does not constitute the mutation. A study of the manner of inactivation of the phage by these agents has not revealed any characteristic difference between ethylation and other alkylations which could be held to account for its apparent uniqueness.

Metabolic endotoxemia promotes adipose dysfunction and inflammation in human obesity

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00277.2018 ◽

2019 ◽

Vol 316 (2) ◽

pp. E319-E332 ◽

Cited By ~ 13

Author(s):

Mercedes Clemente-Postigo ◽

Wilfredo Oliva-Olivera ◽

Leticia Coin-Aragüez ◽

Bruno Ramos-Molina ◽

Rosa María Giraldez-Perez ◽

...

Keyword(s):

Metabolic Diseases ◽

In Vitro Assays ◽

Low Grade ◽

Human Obesity ◽

Gene And Protein Expression ◽

And Function ◽

Adipose Dysfunction ◽

High Degree ◽

Metabolic Endotoxemia

Impaired adipose tissue (AT) lipid handling and inflammation is associated with obesity-related metabolic diseases. Circulating lipopolysaccharides (LPSs) from gut microbiota (metabolic endotoxemia), proposed as a triggering factor for the low-grade inflammation in obesity, might also be responsible for AT dysfunction. Nevertheless, this hypothesis has not been explored in human obesity. To analyze the relationship between metabolic endotoxemia and AT markers for lipogenesis, lipid handling, and inflammation in human obesity, 33 patients with obesity scheduled for surgery were recruited and classified according to their LPS levels. Visceral and subcutaneous AT gene and protein expression were analyzed and adipocyte and AT in vitro assays performed. Subjects with obesity with a high degree of metabolic endotoxemia had lower expression of key genes for AT function and lipogenesis ( SREBP1, FABP4, FASN, and LEP) but higher expression of inflammatory genes in visceral and subcutaneous AT than subjects with low LPS levels. In vitro experiments corroborated that LPS are responsible for adipocyte and AT inflammation and downregulation of PPARG, SCD, FABP4, and LEP expression and LEP secretion. Thus, metabolic endotoxemia influences AT physiology in human obesity by decreasing the expression of factors involved in AT lipid handling and function as well as by increasing inflammation.

Tissue engineering in urology

Canadian Urological Association Journal ◽

10.5489/cuaj.1155 ◽

2013 ◽

Vol 3 (5) ◽

pp. 403 ◽

Cited By ~ 11

Author(s):

Derek J. Matoka ◽

Earl Y. Cheng

Keyword(s):

Tissue Engineering ◽

Multidisciplinary Approach ◽

Normal Function ◽

Healthy Tissue ◽

Clinical Applicability ◽

Basic Technology ◽

Tissue engineering encompasses a multidisciplinary approach gearedtoward the development of biological substitutes designed to restoreand maintain normal function in diseased or injured tissues. Thisarticle reviews the basic technology that is used to generateimplantable tissue-engineered grafts in vitro that will exhibit characteristicsin vivo consistent with the physiology and function ofthe equivalent healthy tissue. We also examine the current trendsin tissue engineering designed to tailor scaffold construction, promoteangiogenesis and identify an optimal seeded cell source.Finally, we describe several currently applied therapeutic modalitiesthat use a tissue-engineered construct. While notable progresshas clearly been demonstrated in this emerging field, these effortshave not yet translated into widespread clinical applicability. Withcontinued development and innovation, there is optimism that thetremendous potential of this field will be realized.L’ingénierie tissulaire englobe une approche multidisciplinaireaxée sur le développement de substituts biologiques en vue derétablir et de maintenir la fonction normale de tissus lésés. L’articlequi suit passe en revue la technologie fondamentale utilisée pourgénérer des greffons implantables produits par ingénierie in vitroet possédant des caractéristiques in vivo correspondant aux tissussains équivalents sur les plans physiologique et fonctionnel.Nous examinons également les tendances actuelles en ingénierietissulaire visant à adapter des échafaudages tissulaires, à promouvoirl’angiogenèse et à dégager une source optimale de cellulesimplantables. Enfin, nous décrivons plusieurs modalités thérapeutiquesactuellement mises en application utilisant un échafaudagecréé par ingénierie tissulaire. En dépit de progrès remarquablesdans ce domaine en effervescence, les efforts déployés ne se sontpas encore traduits par une applicabilité clinique étendue. Desdéveloppements et des percées continus permettent d’être optimisteface au potentiel prodigieux de ce domaine.

Contribution of intermediate filaments to cell stiffness, stiffening, and growth

AJP Cell Physiology ◽

10.1152/ajpcell.2000.279.1.c188 ◽

2000 ◽

Vol 279 (1) ◽

pp. C188-C194 ◽

Cited By ~ 195

Author(s):

Ning Wang ◽

Dimitrije Stamenović

Keyword(s):

Mechanical Properties ◽

Applied Stress ◽

Extended Period ◽

Direct Consequence ◽

Cell Stiffness ◽

Cell Integrity ◽

Wild Type ◽

The Difference ◽

It has been shown previously that intermediate filament (IF) gels in vitro exhibit stiffening at high-applied stress, and it was suggested that this stiffening property of IFs might be important for maintaining cell integrity at large deformations (Janmey PA, Evtenever V, Traub P, and Schliwa M, J Cell Biol 113: 155–160, 1991). In this study, the contribution of IFs to cell mechanical behavior was investigated by measuring cell stiffness in response to applied stress in adherent wild-type and vimentin-deficient fibroblasts using magnetic twisting cytometry. It was found that vimentin-deficient cells were less stiff and exhibited less stiffening than wild-type cells, except at the lowest applied stress (10 dyn/cm2) where the difference in the stiffness was not significant. Similar results were obtained from measurements on wild-type fibroblasts and endothelial cells after vimentin IFs were disrupted by acrylamide. If, however, cells were plated over an extended period of time (16 h), they exhibited a significantly greater stiffness before than after acrylamide, even at the lowest applied stress. A possible reason could be that the initially slack IFs became fully extended due to a high degree of cell spreading and thus contributed to the transmission of mechanical stress across the cell. Taken together, these findings were consistent with the notion that IFs play important roles in the mechanical properties of the cell during large deformation. The experimental data also showed that depleting or disrupting IFs reduced, but did not entirely abolish, cell stiffening. This residual stiffening might be attributed to the effect of geometrical realignment of cytoskeletal filaments in the direction of applied load. It was also found that vimentin-deficient cells exhibited a slower rate of proliferation and DNA synthesis than wild-type cells. This could be a direct consequence of the absence of the intracellular IFs that may be necessary for efficient mediation of mechanical signals within the cell. Taken together, results of this study suggest that IFs play important roles in the mechanical properties of cells and in cell growth.