Biomedical subjects

Karen M Haberstroh

Publications and source records attributed to Karen M Haberstroh.

17 recordsLinked to original sources

PubMed2007

PLGA nanometer surface features manipulate fibronectin interactions for improved vascular cell adhesion.

The largest cause of mortality in the Western world is atherosclerotic vascular disease. Many of these diseases require synthetic vascular grafts; however, their patency rate is only 30% in small (<6 mm) diameter vascular grafts after 5 years of implantation. In an effort to increase small diameter vascular graft success, researchers have been designing random nanostructured surface features which enhance vascular cell functions. However, for the present study, highly-controllable, nanostructured features on poly(lactic-co-glycolic acid) (PLGA) surfaces were formulated. To create ordered nanostructured roughness on PLGA surfaces, either 500, 200, or 100 nm polystyrene nanospheres were separately placed onto mica. These were then used as a template for creating an inverse poly(dimethylsiloxane) mold which was utilized to cast PLGA. Compared to all other PLGA films formulated, AFM results demonstrated greater initial fibronectin spreading on PLGA which possessed spherical 200 nm features. Compared to smooth PLGA, PLGA with 500 or 100 nm surface features, results further showed that PLGA with 200 nm spherical features promoted vascular cell (specifically, endothelial, and smooth muscle cell) adhesion. In this manner, the present study demonstrated a specific nanometer surface feature size that promoted fibronectin spreading and subsequent vascular cell adhesion; criteria critical to vascular graft success.

Animals↗

PubMed2006

Select bladder smooth muscle cell functions were enhanced on three-dimensional, nano-structured poly(ether urethane) scaffolds.

Bladder wall resection is often required as a treatment for invasive bladder cancer. When this happens, a suitable replacement material is needed. The present study, therefore, created three-dimensional, porous, nano-structured poly(ether urethane) (PU) matrices for use as bladder tissue-engineering scaffolds. Select cytocompatibility experiments (specifically adhesion and long-term growth studies) were performed on these scaffolds using human bladder smooth muscle cells (BdSMCs). In addition, the amount of total collagen and elastin present in each cell-seeded scaffold was determined since the production of these extracellular matrix (ECM) proteins is essential for the health and survival of cells and for the functionality of the replaced organ. Finally, to better understand how these scaffolds and resident cells would perform in the complex mechanical environment of the bladder wall, scaffolds and cells were subjected to 10 cmH2O pressure using a computer-controlled pressure chamber. Results provided evidence that compared to conventionally used, micro-dimensional PU scaffolds, the novel, nanodimensional scaffolds created in this research increased cell adhesion, growth, and ECM protein production. Additionally, scaffolds and resident cells were not affected by exposure to 10 cmH2O pressure (compared to controls maintained under atmospheric conditions). These results are promising and provide evidence that the nano-dimensional PU scaffolds created in this research are suitable bladder replacement materials that may outperform materials currently used for such purposes.

Animals↗

PubMed2005

Mechanism(s) of increased vascular cell adhesion on nanostructured poly(lactic-co-glycolic acid) films.

Studies have shown that poly(lactic-co-glycolic acid) (PLGA) films with nanometer surface features promote vascular endothelial and smooth muscle cell adhesion. The objective of this in vitro research was to begin to understand the mechanisms behind this observed increase in vascular cell adhesion. Results provided evidence that nanostructured PLGA adsorbed significantly more vitronectin and fibronectin from serum compared to conventional (or those not possessing nanometer surface features) PLGA. When separately preadsorbing both vitronectin and fibronectin, increased vascular smooth muscle and endothelial cell density was observed on nanostructured (compared to conventional) PLGA. Additionally, blocking of cell-binding epitopes of fibronectin and vitronectin significantly decreased vascular cell adhesion on nanostructured (compared to conventional) PLGA. For this reason, results of the present in vitro study demonstrated that cell adhesive proteins adsorbed in different quantities and altered bioactivity on nanostructured compared to conventional PLGA topographies, which (at least in part) may account for the documented increased vascular cell adhesion on nanostructured PLGA. In this manner, this study continues to provide evidence for the promise of nanostructured PLGA in vascular tissue engineering applications.

Absorbable Implants↗

PubMed2005

Non-uniform flow behavior in a parallel plate flow chamber : alters endothelial cell responses.

Arterial flow characteristics determine vessel health by modulating vascular endothelial cells. One system used to study these interactions is the parallel plate flow chamber. The present in vitro study quantified the uniformity of fluid flow across a parallel plate flow chamber and characterized plate-location dependent endothelial cell gene expression. More specifically, shear stress varied by as much as 11% across the chamber area, which caused non-uniform ecNOS (p < 0.05) and COX-2 (p < 0.05) mRNA expression across the plate area. Results herein suggest that chamber variations may result during construction or assembly, which ultimately affect flow-sensitive cell responses (including mRNA expression). Therefore, these limitations should be considered when reporting endothelial cell responses to fluid flow using parallel plate flow chambers.

Animals↗

PubMed2005

Three-dimensional, nano-structured PLGA scaffolds for bladder tissue replacement applications.

In total, approximately 400 million people worldwide suffer from urinary bladder cancer (Nat Biotechnol 17 (1999) 149). When radical cysectomy is required as treatment, a replacement material is clearly necessitated. For this purpose, three-dimensional poly(lactic-co-glycolic acid) (PLGA) scaffolds were constructed using solvent casting and salt leaching processes. These scaffolds were manipulated to possess nano-dimensional surface features by soaking in sodium hydroxide at select concentrations and for various periods of time. Human bladder smooth muscle cells were then seeded onto these nano-dimensional scaffolds; adhesion and longer-term cell growth experiments were performed for either 4 h, or 1, 3, and 5 days, respectively. Additionally, collagen and elastin production was quantified following each experiment. In all cases, control cells were placed in an incubator and subjected to normal atmospheric pressure, while experimental cells were placed in a pressure chamber and subjected to a sustained pressure of 10 cm H(2)O. Results of this study provided evidence that porous, nano-dimensional polymeric scaffolds enhanced cell adhesion and growth, while also promoting increased elastin and collagen production. Moreover, in general, exposure to pressure did not alter cellular adhesion, growth, or extracellular matrix protein production, which suggests that the scaffolds and their resident cells will fair well in the complex mechanical environment of the bladder wall. In combination, these results provide evidence that the nano-dimensional PLGA scaffolds created in this research are promising as the next generation of bladder wall replacement materials.

Biocompatible Materials↗

PubMed2005

Microfilaments are involved in renal cell responses to sustained hydrostatic pressure.

PURPOSE: Increased pressures within renal interstitial fluid, as associated with a number of renal pathologies, could affect cell function and gene expression. The long-term objective of this research is to elucidate kidney cell responses to pathological hydrostatic pressures. MATERIALS AND METHODS: In vitro studies were performed in 2 kidney cell lines (cortical tubular and medullary) to determine changes in cell numbers and cytoskeletal (specifically microfilament, microtubule and intermediate filament) arrangement following exposure to pathological (60 cm H2O) pressures. A novel pressure system was used to apply pressure to renal cells for up to 7 days. Cell counts and fluorescent staining were performed to determine alterations in response to pressure. RESULTS: Exposure to pressures of 60 cm H2O resulted in increased renal cell numbers and rearrangement in individual microfilament structures after 7 days. CONCLUSIONS: These results prove that hydrostatic pressure alters the function of renal cells. In the future such knowledge of renal cell responses to pressure along with an understanding of the mechanisms involved will aid in the design of novel, targeted drug therapies for treating kidney pathologies.

Actin Cytoskeleton↗

PubMed2004

Nanometer surface roughness increases select osteoblast adhesion on carbon nanofiber compacts.

Carbon nanofibers have exceptional theoretical mechanical properties (such as low weight-to-strength ratios) that, along with possessing nanoscale fiber dimensions similar to crystalline hydroxyapatite found in bone, suggest strong possibilities for use as an orthopedic/dental implant material. To determine, for the first time, cytocompatibility properties pertinent for bone prosthetic applications, osteoblast (bone-forming cells), fibroblast (cells contributing to callus formation and fibrous encapsulation events that result in implant loosening), chondrocyte (cartilage-forming cells), and smooth muscle cell (for comparison purposes) adhesion were determined on carbon nanofibers in the present in vitro study. Results provided evidence that, compared to conventional carbon fibers, nanometer dimension carbon fibers promoted select osteoblast adhesion. Moreover, adhesion of other cells was not influenced by carbon fiber dimensions. In fact, smooth muscle cell, fibroblast, and chondrocyte adhesion decreased with an increase in either carbon nanofiber surface energy or simultaneous change in carbon nanofiber chemistry. To determine properties that selectively enhanced osteoblast adhesion, similar cell adhesion assays were performed on polymer (specifically, poly-lactic-co-glycolic; PLGA) casts of carbon fiber compacts previously tested. Compared to PLGA casts of conventional carbon fibers, results provided the first evidence of enhanced select osteoblast adhesion on PLGA casts of nanophase carbon fibers. The summation of these results demonstrate that due to a high degree of nanometer surface roughness, carbon fibers with nanometer dimensions may be optimal materials to selectively increase osteoblast adhesion necessary for successful orthopedic/dental implant applications.

Alloys↗

PubMed2004

Decreased fibroblast cell density on chemically degraded poly-lactic-co-glycolic acid, polyurethane, and polycaprolactone.

Select prolonged functions of fibroblasts leading to extensive fibrous tissue encapsulation can be detrimental to numerous implant applications, including materials designed for the bladder, vasculature, and bone. Specifically, overextended functions of fibroblasts at the tissue-implant interface for orthopedic applications lead to callus formation, fibrous encapsulation events, and ultimately soft (not desirable hard-bony) tissue juxtaposition. Such events result in insufficient regeneration of bone and compromise the overall success of the implant. The objective of the present in vitro study was to determine, for the first time, fibroblast densities on NaOH-treated poly-lactic-co-glycolic acid co-polymers (PLGA), HNO(3)-treated polyurethane (PU), and NaOH-treated polycaprolactone (PCL). Previous studies have demonstrated increased bladder, vascular, and bone cell densities on chemically treated compared to unaltered PLGA, PU, and PCL films. Results of this study provided evidence of decreased fibroblast numbers on chemically treated PLGA, PU, and PCL after time periods of up to 5 days. Examination of these substrates revealed that all chemically modified polymers possessed a high degree of nanometer surface roughness compared to their respective unaltered polymers. In contrast, other material properties (such as chemistry and wettability) were different when comparing chemically treated PLGA, PU, and PCL films. Since fibroblasts are anchorage-dependent cells whose adhesion is a critical prerequisite to the prolonged, extensive formation of a fibrous-tissue containing extracellular matrix, the present in vitro results of decreased fibroblast densities on chemically degraded PLGA, PU, and PCL suggest that these materials may be suitable materials for numerous tissue-engineering applications and, thus, deserve further investigation.

Absorbable Implants↗

PubMed2004

Endothelial and vascular smooth muscle cell function on poly(lactic-co-glycolic acid) with nano-structured surface features.

Biomaterials that successfully integrate into surrounding tissue should match not only the tissue's mechanical properties, but also its topography. The cellular response to a biomaterial may be enhanced in synthetic polymer formulations by mimicking the surface roughness created by the associated nano-structured extra-cellular matrix components of natural tissue. As a first step towards this endeavor, the goal of the present in vitro study was to use these design parameters to develop a synthetic, nano-structured, polymeric biomaterial that promotes cell adhesion and growth for vascular applications. In a novel manner, poly(lactic-co-glycolic acid) (PLGA) (50/50wt% mix) was synthesized to possess a range (from micron to nanometer) of surface features. Reduction of surface features was accomplished by treating conventional PLGA with various concentrations of NaOH for select periods of time. Results from cell experiments indicated that, compared to conventional PLGA, NaOH treated PLGA enhanced vascular smooth muscle cell adhesion and proliferation. However, PLGA prepared by soaking in NaOH decreased endothelial cell adhesion and proliferation compared to conventional PLGA. After further investigation, this finding was determined to be a result of chemical (and not topographical) changes during polymer synthesis. Surface chemistry effects were removed while retaining nano-structured topography by using polymer/elastomer casting methods. Results demonstrated that endothelial and smooth muscle cell densities increased on nano-structured cast PLGA. For these reasons, the present in vitro study provided the first evidence that nano-structured surface features can significantly improve vascular cell densities; such design criteria can be used in the synthesis of the next-generation of more successful tissue-engineered vascular grafts.

Animals↗

PubMed2004

Technological advances in nanoscale biomaterials: the future of synthetic vascular graft design.

Currently, autologous veins are the first choice for patients in need of bypass grafting materials. However, due to either pre-existing conditions or previous bypass surgery, some patients lack the necessary amount of host tissue for such procedures. Unfortunately, current synthetic vascular grafts of less than 6 mm in diameter have been plagued by a variety of problems. For this reason, there has been significant research aimed at finding more suitable small-diameter vascular graft materials. In order to improve vascular cell functions on such synthetic materials, several techniques are currently under development that attempt to mimic the natural nanometer architecture of the vascular basement membrane. This review presents several processes including colloidal lithography, chemical etching, electrospinning and solid free-form fabrication that could play a role in the future of vascular nanostructured biomaterial development.

Biocompatible Materials↗

PubMed2003

Polymers with nano-dimensional surface features enhance bladder smooth muscle cell adhesion.

Previous studies investigating the design of synthetic bladder wall substitutes have involved polymers with micro dimensional structures. Since the body is made up of nano-structured components (e.g., extracellular matrix proteins), the focus of the present in vitro study was to design nano-structured polymers for use as synthetic bladder constructs that mimic the topography of natural bladder tissue. In order to complete this task, novel nano-structured biodegradable polymeric films of poly-lactic-co-glycolic-acid (PLGA), poly-ether-urethane (PU), and poly-caprolactone (PCL) were fabricated and separately treated with various concentrations of NaOH (for PLGA and PCL) and HNO(3) (for PU) for select time periods. These treatments reduced the polymer surface feature dimensions from conventional micron dimensions to biologically inspired nanometer dimensions. Select cytocompatibility properties of these biomaterials were tested in vitro. Results provide the first evidence that adhesion of bladder smooth muscle cells is enhanced as polymer surface feature dimensions are reduced into the nanometer range. In addition, surface analysis results reveal that the polymer nanometer surface roughness is the primary design parameter that increases bladder smooth muscle cell adhesion. For this reason, the "next generation" of tissue-engineered bladder constructs with increased efficacy should contain surfaces with nanometer (as opposed to micron) surface features.

Animals↗

PubMed2003

Selective bone cell adhesion on formulations containing carbon nanofibers.

Bone cell adhesion on novel carbon nanofibers and polycarbonate urethane/carbon nanofiber (PCU/CNF) composites is investigated in the present in vitro study. Carbon nanofibers have exceptional theoretical mechanical properties (such as high strength to weight ratios) that, along with possessing nanoscale fiber dimensions similar to crystalline hydroxyapatite found in physiological bone, suggest strong possibilities for use as an orthopedic/dental implant material. The effects of select properties of carbon fibers (specifically, dimension, surface energy, and chemistry) on osteoblast, fibroblast, chondrocyte, and smooth muscle cell adhesion were determined in the present in vitro study. Results provided evidence that smaller-scale (i.e., nanometer dimension) carbon fibers promoted osteoblast adhesion. Adhesion of other cells was not influenced by carbon fiber dimensions. Also, smooth muscle cell, fibroblast, and chondrocyte adhesion decreased with an increase in either carbon nanofiber surface energy or simultaneous change in carbon nanofiber chemistry. Moreover, greater weight percentages of high surface energy carbon nanofibers in the PCU/CNF composite increased osteoblast adhesion while at the same time decreased fibroblast adhesion.

3T3 Cells↗

PubMed2003

Nano-structured polymers enhance bladder smooth muscle cell function.

It is the hypothesis of the present study that a biocompatible material which mimics the nanometer topography of native bladder tissue will enhance cellular responses and lead to better tissue integration in vivo. Previous in vitro studies have verified the ability to successfully reduce the surface feature dimensions of poly(lactic-co-glycolic acid) (PLGA) and poly(ether urethane) (PU) films into the nanometer regime via chemical etching procedures. Results from these studies also provided the first evidence that bladder smooth muscle cell adhesion was enhanced on chemically treated nano-structured polymeric surfaces compared to their conventional counterparts. Although cell adhesion is necessary for a biomaterial's success, subsequent cell functions (such as long-term cell growth and proliferation) are also critical for tissue ingrowth and long-term implant survival. The present in vitro study, therefore, investigated the function of bladder smooth muscle cells on these novel, nano-structured polymers over the expanded periods of 1, 3 and 5 days. Results indicated that cell number was influenced by both surface roughness and surface chemistry changes; the important contributor, however, was increased nanometer surface roughness. This claim is supported by the fact that cell number was enhanced on nano-structured compared to conventional PLGA and PU once chemistry changes were eliminated using casting techniques.

Animals↗

PubMed2002

Alterations in the molecular determinants of bladder compliance at hydrostatic pressures less than 40 cm. H2O.

PURPOSE: Bladder outlet obstruction with intravesical pressures exceeding 40 cm. H2O often results in irreversible renal damage. Bladder outlet obstruction also results in alterations in bladder physiology, including wall thickening, reduced compliance and decreased capacity. If unchecked these changes may lead to the subsequent need for bladder augmentation. From a biomechanical standpoint, compliance is primarily related to extracellular matrix deposition, which in turn is dependent on the balanced activity of proteolytic enzymes (that is matrix metalloproteinases [MMPs]) and their endogenous inhibitors (that is tissue inhibitors of metalloproteinases [TIMPs]). To date, the threshold pressure above which alterations in these key determinants of bladder compliance occur has not been determined. Therefore, using a novel device of our own design, we applied hydrostatic pressures in the physiological range to human bladder smooth muscle cells to determine the effect on MMPs, TIMP-1 and transcription of the major structural collagens (types I and III). MATERIALS AND METHODS: Human bladder smooth muscle cells (staining positive for alpha-smooth muscle actin) were plated at a density of 100,000 cells per 10 cm.2 and cultured for 2 days in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum. Cells were subsequently exposed to pressures of 0.3, 20 and 40 cm. H2O for 1, 3, 7 and 24 hours in serum-free DMEM. A computer interface maintained pressure levels for the duration of the experiments and collected pressure data. MMP-1 and 3, and TIMP-1 immunoassay and zymography for MMP-2 and 9 were performed. Polymerase chain reaction for human collagen types I and III was performed following reverse transcription of total purified mRNA. All experiments were repeated 3 times and statistical analysis was performed using a 2-tailed Student t test. RESULTS: Exposure of bladder smooth muscle cells to a sustained hydrostatic pressure of 20 cm. H2O for 7 hours in serum-free DMEM resulted in a time dependent decrease in MMP-1, 2 and 9 activity (15%, 37% and 25%) compared to controls maintained at atmospheric pressure (p <0.01). TIMP-1 levels increased an average of 10% after exposure to 20 cm. H2O. These changes became statistically significant when the cells were exposed to 40 cm. H2O pressure for 3, 7 and 24 hours (+14%, +21% and +50%, respectively). No statistically significant differences in MMP-3 and collagen type I or III mRNA levels were observed. CONCLUSIONS: Our results reveal that MMP-1, 2 and 9 are significantly down-regulated in a time and pressure dependent fashion following exposure of bladder smooth muscle cells to 20 cm. H2O for as little as 7 hours. TIMP-1 levels increased under similar conditions. These alterations in MMPs and TIMP-1 favor accumulation of extracellular matrix, structural components associated with bladder wall thickness and decreased compliance. These results are consistent with previous data from animal models of complete outlet obstruction. Our results support the concept that pressures 40 cm. H2O or less contribute to molecular changes consistent with decreased compliance associated with bladder dysfunction.

Collagen Type I↗

PubMed2002

Nanostructured polymer/nanophase ceramic composites enhance osteoblast and chondrocyte adhesion.

Osteoblast (bone-forming cell) and chondrocyte (cartilage-synthesizing cell) adhesion on novel nanostructured polylactic/glycolic acid (PLGA) and titania composites were investigated in the present in vitro study. Nanostructured polymers were created by chemically treating micron-structured PLGA with select concentrations of NaOH for various periods of time. Dimensions of ceramics were controlled by utilizing either micron or nanometer grain size titania. Compared with surfaces with conventional or micron surface roughness dimensions, results provided the first evidence of increased osteoblast and chondrocyte adhesion on 100 wt% PLGA films with nanometer polymer surface roughness dimensions. Results also confirmed other literature reports of enhanced osteoblast adhesion on 100 wt% nanometer compared with conventional grain size titania compacts; however, the present study provided the first evidence that decreasing titania grain size into the nanometer range did not influence chondrocyte adhesion. Finally, osteoblast and chondrocyte adhesion increased on 70/30 wt% PLGA/titania composites formulated to possess nanosurface rather than conventional surface feature dimensions. The present study, thus, provided evidence that these nanostructured PLGA/titania composites may possess the ability to simulate surface and/or chemical properties of bone and cartilage, respectively, to allow for exciting alternatives in the design of prostheses with greater efficacy.

Cell Adhesion↗

PubMed2002

Enhanced functions of vascular and bladder cells on poly-lactic-co-glycolic acid polymers with nanostructured surfaces.

Polymers currently utilized for tissue engineering applications do not possess surfaces with nanostructured features. However, the tissue that the polymers will replace is composed of proteins that have nanometer dimensions. Undoubtedly, in situ, cells are accustomed to interacting with surface roughness values in the nanometer regime due to the presence of such proteins in natural tissue. Therefore, the objective of this paper was to design, synthesize and evaluate (using in vitro cellular models) poly-lactic-co-glycolic acid (PLGA) with nanostructured surface features to serve as the next generation of more efficient tissue engineered materials. For this purpose, nanostructured PLGA was created by treating conventional PLGA with various concentrations of NaOH for select periods of time. To eliminate surface chemistry changes created though the etching process, PLGA was cast from silastic molds of NaOH-treated nanostructured PLGA. Results provided the first evidence of increased numbers of vascular cells (specifically, endothelial and aortic smooth muscle cells) and bladder smooth muscle cells on nanostructured compared with conventional PLGA substrates. For this reason, the present results suggest, for the first time, that PLGA should incorporate a high degree of nanostructured surface roughness to enhance tissue regeneration for vascular and bladder applications.

Animals↗

PubMed2002

A novel in-vitro system for the simultaneous exposure of bladder smooth muscle cells to mechanical strain and sustained hydrostatic pressure.

The novel hydrostrain system was designed in an effort to establish and maintain conditions that simulate the in-vivo mechanical environment of the bladder. In this laboratory system, ovine bladder smooth muscle cells on flexible, 10-cm-dia silastic membranes were exposed simultaneously to hydrostatic pressure (40 cm H2O, a pressure level currently associated with bladder pathologies) and mechanical strains (up to 25 percent) under standard cell culture conditions for 7 h. Under these conditions, Heparin Binding-Epidermal Growth Factor and Collagen Type III mRNA expression were significantly increased (p<0.01 and 0.1, respectively); however, no changes were observed in Collagen Type I mRNA expression. Decreases in the Collagen Type I:Type III ratio following simultaneous exposure of bladder smooth muscle cells to pathological levels of hydrostatic pressure and mechanical strain in vitro are in agreement with clinically observed increases in Collagen Type III with concomitant decreased human bladder compliance. The results of the present study, therefore, provide cellular/molecular level information relevant to bladder pathology that could have significant implications in the field of clinical urology.

Animals↗