E. Loboa - Academia.edu (original) (raw)

Papers by E. Loboa

Tribasic copper chloride (TBCC) has been shown to have better bioavailability than copper sulfate... more Tribasic copper chloride (TBCC) has been shown to have better bioavailability than copper sulfate pentahydrate (CS) when fed at levels in excess of the requirement. Our objective was to determine if this relationship holds at levels below the Cu requirement. After depleting Cu levels for 7 d, 3 pens of 4 chicks/pen were fed a purified diet or a sorghumsoy diet supplemented with either 0, 1, 3, 4.5 or 6 ppm Cu. LPS was injected in order to initiate an acute phase response and bioavailability was calculated by common-intercept multiple linear regression. Prior to LPS, TBCC resulted in greater (P < 0.05) bioavailability as indicated by weight gain and tendon Cu levels with both diet types. Following LPS injection, TBCC resulted in greater bioavailability based on the plasma acute phase protein, ceruloplasmin (P = 0.01; slope ratio = 1.26). Bioavailabilities of the Cu sources did not differ for hematocrit or liver Cu. In general, these results indicate higher bioavailability of TBCC ...

Tissue Engineering Part B: Reviews, 2012

Mesenchymal stem cells (MSCs) hold great potential for regenerative medicine and tissue-engineeri... more Mesenchymal stem cells (MSCs) hold great potential for regenerative medicine and tissue-engineering applications. They have multipotent differentiation capabilities and have been shown to differentiate down various lineages, including osteoblasts, adipocytes, chondrocytes, myocytes, and possibly neurons. The majority of approaches to control the MSC fate have been via the use of chemical factors in the form of growth factors within the culture medium. More recently, it has been understood that mechanical forces play a significant role in regulating MSC fate. We and others have shown that mechanical stimuli can control MSC lineage specification. The cytoskeleton is known to play a large role in mechanotransduction, and a growing number of studies are showing that it can also contribute to MSC differentiation. This review analyzes the significant contribution of actin and integrin distribution, and the smaller role of microtubules, in regulating MSC fate. Osteogenic differentiation is more prevalent in MSCs with a stiff, spread actin cytoskeleton and greater numbers of focal adhesions. Both adipogenic differentiation and chondrogenic differentiation are encouraged when MSCs have a spherical morphology associated with a dispersed actin cytoskeleton with few focal adhesions. Different mechanical stimuli can be implemented to alter these cytoskeletal patterns and encourage MSC differentiation to the desired lineage.

AJP: Cell Physiology, 2007

Cell morphology may be an important stimulus during differentiation of human adipose-derived adul... more Cell morphology may be an important stimulus during differentiation of human adipose-derived adult stem (hADAS) cells, but there are limited studies that have investigated the role of the cytoskeleton or associated proteins in hADAS cells undergoing differentiation. Palladin is an actin-associated protein that plays an integral role in focal adhesion and cytoskeleton organization. In this study we show that palladin was expressed by hADAS cells and was modulated during osteogenic differentiation and in response to cyclic tensile strain. Human ADAS cells expressed the 90- and 140-kDa palladin isoforms and upregulated expression of both isoforms after culture in conditions that promoted osteogenesis. Palladin mRNA expression levels were also increased in hADAS cells subjected to cyclic tensile strain. Knockdown of the palladin gene during osteogenesis resulted in decreased actin stress fibers and decreased protein levels of Eps8, an epidermal growth factor receptor tyrosine kinase tha...

Advanced Science, Engineering and Medicine

Stem Cells Translational Medicine, 2016

Human adipose stem cells (hASCs) are an attractive cell source for bone tissue engineering applic... more Human adipose stem cells (hASCs) are an attractive cell source for bone tissue engineering applications. However, a critical issue to be addressed before widespread hASC clinical translation is the dramatic variability in proliferative capacity and osteogenic potential among hASCs isolated from different donors. The goal of this study was to test our hypothesis that electrical cell-substrate impedance spectroscopy (ECIS) could track complex bioimpedance patterns of hASCs throughout proliferation and osteogenic differentiation to better understand and predict variability among hASC populations. Superlots composed of hASCs from young (aged 24-36 years), middle-aged (aged 48-55 years), and elderly (aged 60-81 years) donors were seeded on gold electrode arrays. Complex impedance measurements were taken throughout proliferation and osteogenic differentiation. During osteogenic differentiation, four impedance phases were identified: increase, primary stabilization, drop phase, and secondary stabilization. Matrix deposition was first observed 48-96 hours after the impedance maximum, indicating, for the first time, that ECIS can identify morphological changes that correspond to late-stage osteogenic differentiation. The impedance maximum was observed at day 10.0 in young, day 6.1 in middle-aged, and day 1.3 in elderly hASCs, suggesting that hASCs from younger donors require a longer time to differentiate than do hASCs from older donors, but young hASCs proliferated more and accreted more calcium long-term. This is the first study to use ECIS to predict osteogenic potential of multiple hASC populations and to show that donor age may temporally control onset of osteogenesis. These findings could be critical for development of patient-specific bone tissue engineering and regenerative medicine therapies. STEM CELLS TRANSLATIONAL MEDICINE 2016;5:1-10 SIGNIFICANCE Human adipose stem cells (hASCs) are an appealing cell source for bone tissue engineering and regenerative medicine applications because they can be obtained in high quantities via liposuction procedures and can differentiate down musculoskeletal lineages. However, a major barrier to clinical translation of hASCs is that cells from different donors have varying capacities to proliferate and differentiate. This study used electrical impedance spectroscopy to noninvasively track osteogenic differentiation of age-grouped donors in real time, showing that age-grouped hASCs have distinct complex impedance patterns. This method could be used to improve understanding of the biology that causes variability among hASC populations and to provide quantitative quality control standards for hASC populations in stem cell manufacturing and bone tissue engineering applications.

Biomedical Materials, 2016

Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2015

Stem Cells Translational Medicine, 2015

SummaryHuman adipose stem cells (hASCs) have the potential to treat patients with a variety of cl... more SummaryHuman adipose stem cells (hASCs) have the potential to treat patients with a variety of clinical conditions. Recent advancements in translational research, regulatory policy, and industry have positioned hASCs on the threshold of clinical translation. We discuss the progress and challenges of bringing adipose stem cell therapy into mainstream clinical use. This article details the advances made in recent years that have helped move human adipose stem cell therapy toward mainstream clinical use from a translational research, regulatory policy, and industrial standpoint. Four recurrent themes in translational technology as they pertain to human adipose stem cells are discussed: automated closed-system operations, biosensors and real-time monitoring, biomimetics, and rapid manufacturing. In light of recent FDA guidance documents, regulatory concerns about adipose stem cell therapy are discussed. Finally, an update is provided on the current state of clinical trials and the emerging industry that uses human adipose stem cells. This article is expected to stimulate future studies in translational adipose stem cell research.

2007 IEEE Ultrasonics Symposium Proceedings, 2007

Journal of Nutrition, 2011

The effects of dietary calcium (Ca) deficiency on skeletal integrity are well characterized in gr... more The effects of dietary calcium (Ca) deficiency on skeletal integrity are well characterized in growing and mature mammals; however, less is known about Ca nutrition during the neonatal period. In this study, we examined the effects of neonatal Ca nutrition on bone integrity, endocrine hormones, and mesenchymal stem cell (MSC) activity. Neonatal pigs (24 ± 6 h of age) received either a Ca-adequate (1.2 g/100 g) or an ~40% Ca-deficient diet for 18 d. Ca deficiency reduced (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) bone flexural strength and bone mineral density without major differences in plasma indicators of Ca status. There were no meaningful differences in plasma Ca, phosphate (PO(4)), parathyroid hormone, or 1,25-dihydroxycholecalciferol due to Ca nutrition throughout the study. Calcium deficiency also reduced (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) the in vivo proliferation of MSC by ~50%. In vitro studies utilizing homologous sera demonstrated that MSC activity was affected (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) by both the Ca status of the pig and the sera as well as by their interaction. The results indicate that neonatal Ca nutrition is crucial for bone integrity and suggest that early-life Ca restriction may have long-term effects on bone integrity via programming of MSC.

Osteoarthritis and Cartilage, 2007

$Research paper thumbnail of Mechanobiology of initial pseudarthrosis formation with oblique fractures$

Journal of Orthopaedic Research, 2001

Mechanical stresses play an important role in regulating tissue differentiation in a variety of c... more Mechanical stresses play an important role in regulating tissue differentiation in a variety of contexts during skeletal development and regeneration. It has been shown that some intermittent loading at a fracture site can accelerate secondary fracture healing. However, it has not been shown how the stress and strain histories resulting from mechanical loading of a fracture might, in some cases, inhibit normal fracture healing and induce pseudarthrosis formation. In this study, finite element analysis is used to calculate hydrostatic stress and maximum principal tensile strain patterns in regenerating tissue around the site of an oblique fracture. Using a mechanobiologic view on tissue differentiation, we compared calculated stress and strain patterns within the fracture callus to the histomorphology of a typical oblique pseudarthrosis. Tissue differentiation predictions were consistent with the characteristic histomorphology of oblique pseudarthrosis: in the interfragmentary gap. tensile strains led to &amp;quot;cleavage&amp;quot; of the callus; at the ends of both fracture fragments, hydrostatic pressure and tensile strain caused fibrocartilage formation, and, at discrete locations of the periosteum at the oblique fracture ends, mild hydrostatic tension caused bone formation. We also found that discrete regions of high hydrostatic pressure correlated with locations of periosteal bone resorption. When previous findings with distraction osteogenesis are considered with these observations, it appears that low levels of hydrostatic pressure may be conducive to periosteal cartilage formation but high hydrostatic pressure may induce periosteal bone resorption during bone healing. We concluded that tissue differentiation in pseudarthrosis formation is consistent with concepts previously presented for understanding fracture healing, distraction osteogenesis, and joint formation.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

Acoustic radiation force imaging methods distinguish tissue structure and composition by monitori... more Acoustic radiation force imaging methods distinguish tissue structure and composition by monitoring tissue responses to applied radiation force excitations. Although these responses are a complex, multidimensional function of the geometric and viscoelastic nature of tissue, simplified discrete biomechanical models offer meaningful insight to the physical phenomena that govern induced tissue motion. Applying Voigt and standard linear viscoelastic tissue models, we present a new radiation force technique - monitored steady-state excitation and recovery (MSSER) imaging - that tracks both steady-state displacement during prolonged force application and transient response following force cessation to estimate tissue mechanical properties such as elasticity and viscosity. In concert with shear wave elasticity imaging (SWEI) estimates for Young&amp;#39;s modulus, MSSER methods are useful for estimating tissue mechanical properties independent of the applied force magnitude. We test our methods in gelatin phantoms and excised pig muscle, with confirmation through mechanical property measurement. Our results measured 10.6 kPa, 14.7 kPa, and 17.1 kPa (gelatin) and 122.4 kPa (pig muscle) with less than 10% error. This work demonstrates the feasibility of MSSER imaging and merits further efforts to incorporate relevant mechanical tissue models into the development of novel radiation force imaging techniques.

Computer Methods and Programs in Biomedicine, 2007

The objective of this work was to develop and test a semi-automated finite element mesh generatio... more The objective of this work was to develop and test a semi-automated finite element mesh generation method using computed tomography (CT) image data of a canine radius. The present study employs a direct conversion from CT Hounsfield units to elastic moduli. Our method attempts to minimize user interaction and eliminate the need for mesh smoothing to produce a model suitable for finite element analysis. Validation of the computational model was conducted by loading the CT-imaged canine radius in four-point bending and using strain gages to record resultant strains that were then compared to strains calculated with the computational model. Geometry-based and uniform modulus voxel-based models were also constructed from the same imaging data set and compared. The nonuniform voxel-based model most accurately predicted the axial strain response of the sample bone (R 2 = 0.9764).