Steven H Elder

Publications of Steven H Elder

• Structural and biomechanical characterizations of porcine myocardial extracellular matrix.

  Authors: Bo Wang, Mary E Tedder, Clara E Perez, Guangjun Wang, Amy L de Jongh Curry, Filip To, Steven H Elder, Lakiesha N Williams, Dan T Simionescu, Jun Liao

  Journal of materials science. Materials in medicine. 05/2012;

  Extracellular matrix (ECM) of myocardium plays an important role to maintain a multilayered helical architecture of cardiomyocytes. In this study, we have characterized the structural andExtracellular matrix (ECM) of myocardium plays an important role to maintain a multilayered helical architecture of cardiomyocytes. In this study, we have characterized the structural and biomechanical properties of porcine myocardial ECM. Fresh myocardium were decellularized in a rotating bioreactor using 0.1 % sodium dodecyl sulfate solution. Masson's trichrome staining and SEM demonstrated the removal of cells and preservation of the interconnected 3D cardiomyocyte lacunae. Movat's pentachrome staining showed the preservation of cardiac elastin ultrastructure and vascular elastin distribution/alignment. DNA assay result confirmed a 98.59 % reduction in DNA content; the acellular myocardial scaffolds were found completely lack of staining for the porcine α-Gal antigen; and the accelerating enzymatic degradation assessment showed a constant degradation rate. Tensile and shear properties of the acellular myocardial scaffolds were also evaluated. Our observations showed that the acellular myocardial ECM possessed important traits of biodegradable scaffolds, indicating the potentials in cardiac regeneration and whole heart tissue engineering.

• A comparative biomechanical analysis of term fetal membranes in human and domestic species.

  Authors: Ali Borazjani, Benjamin C Weed, Sourav S Patnaik, Jean M Feugang, David Christiansen, Steven H Elder, Peter L Ryan, Jun Liao

  American journal of obstetrics and gynecology. 02/2011; 204(4):365.e25-36.

  The purpose of this study was to biomechanically characterize and compare human, porcine, equine, and ovine fetal membranes. Noncontact metrology was used for topographic analyses. Uniaxial tensileThe purpose of this study was to biomechanically characterize and compare human, porcine, equine, and ovine fetal membranes. Noncontact metrology was used for topographic analyses. Uniaxial tensile testing was performed to resolve specific biomechanical values. Puncture force and radial stresses were determined with biaxial puncture testing. Microstructure and surface tortuosity were analyzed histologically. Equine and human membranes sustained larger magnitude loading, but ovine and porcine membranes exhibited stronger material properties. Biaxial puncture validated uniaxial results; human and equine groups accommodated the largest loads but lowest stresses. Equine membranes were mostly vascularized; tortuosity was highest in porcine membranes. Species' gestation length was correlated positively with membrane thickness. The anatomy of placentation and length of species gestation show distinct relationships to membrane biomechanics. Unlike other species, human fetal membranes do not compensate for structural weakness with a thicker membrane. This finding may explain the high incidence of preterm premature rupture of membranes in humans.

• Effect of a mechanical stimulation bioreactor on tissue engineered, scaffold-free cartilage.

  Authors: Scott C Tran, Avery J Cooley, Steven H Elder

  Biotechnology and bioengineering. 01/2011; 108(6):1421-9.

  Achieving sufficient functional properties prior to implantation remains a significant challenge for the development of tissue engineered cartilage. Many studies have shown chondrocytes respond wellAchieving sufficient functional properties prior to implantation remains a significant challenge for the development of tissue engineered cartilage. Many studies have shown chondrocytes respond well to various mechanical stimuli, resulting in the development of bioreactors capable of transmitting forces to articular cartilage in vitro. In this study, we describe the production of sizeable, tissue engineered cartilage using a novel scaffold-free approach, and determine the effect of perfusion and mechanical stimulation from a C9-x Cartigen bioreactor on the properties of the tissue engineered cartilage. We created sizable tissue engineered cartilage from porcine chondrocytes using a scaffold-free approach by centrifuging a high-density chondrocyte cell-suspension onto an agarose layer in a 50 mL tube. The gross and histological appearances, biochemical content, and mechanical properties of constructs cultured in the bioreactor for 4 weeks were compared to constructs cultured statically. Mechanical properties were determined from unconfined uniaxial compression tests. Constructs cultured in the bioreactor exhibited an increase in total GAG content, equilibrium compressive modulus, and dynamic modulus versus static constructs. Our study demonstrates the C9-x CartiGen bioreactor is able to enhance the biomechanical and biochemical properties of scaffold-free tissue engineered cartilage; however, no additional enhancement was seen between loaded and perfused groups.

• Vasoactive agents alter the biomechanical properties of aortic heart valve leaflets in a time-dependent manner.

  Authors: James N Warnock, Carol A Pregonero Gamez, Scott A Metzler, Joseph Chen, Steven H Elder, Jun Liao

  The Journal of heart valve disease. 01/2010; 19(1):86-95; discussion 96.

  Although the vasoactive agents, angiotensin II (Ang II) and 5-hydroxytryptamine (5-HT) are implicated in aortic heart valve disease, it is unclear how these compounds alter the biomechanicalAlthough the vasoactive agents, angiotensin II (Ang II) and 5-hydroxytryptamine (5-HT) are implicated in aortic heart valve disease, it is unclear how these compounds alter the biomechanical properties of valve leaflet tissue. The study aim was to characterize temporal changes in the elastic modulus of tissues incubated with these compounds. Valve leaflets were excised from fresh porcine aortic heart valves. Leaflet tissue was incubated with 10(-6) M 5-HT, or 10(-6) M Ang II. The stress and elongation of the tissue in the circumferential and radial directions was measured using a stepper motor-driven micromechanical testing machine at 0.5, 6, and 24 h, followed by calculations of strain and elastic modulus of each sample. Tissue samples incubated with Ang II showed a significant increase in stiffness with time in the radial direction, but not in the circumferential direction. Regression analysis showed a correlation between time and elastic modulus for the tissue (R2 = 0.84). Conversely, leaflets incubated in 5-HT did not show any significant change in elastic modulus over time in the radial direction; however, significant increases in stiffness were observed after 24 h in the circumferential direction. A strong correlation between the elastic modulus in the circumferential direction and time was also noted (R2 = 0.99). The study results showed that vasoactive agents are capable of increasing the elastic modulus of aortic valve tissue in a time-dependent manner. Furthermore, the biomechanical changes induced by vasoactive agents are direction-specific, indicating different modes of action.

• Biomechanical and molecular characteristics of hereditary equine regional dermal asthenia in Quarter Horses.

  Authors: Jesse G Grady, Steven H Elder, Peter L Ryan, Cyprianna E Swiderski, Ann M Rashmir-Raven

  Veterinary dermatology. 10/2009; 20(5-6):591-9.

  Hereditary equine regional dermal asthenia (HERDA) is an autosomal recessive skin disorder that has yet to be fully characterized. HERDA is predominately expressed in Quarter Horses, with theHereditary equine regional dermal asthenia (HERDA) is an autosomal recessive skin disorder that has yet to be fully characterized. HERDA is predominately expressed in Quarter Horses, with the majority of these disseminating from elite cutting horse bloodlines, leading to the increased incidence of HERDA in recent years. Affected horses have loose, hyper-extensible, fragile skin and are frequently euthanized due to poor wound healing and disfiguring scars. This study sought to better characterize HERDA by analysis of the biomechanical parameters of tensile strength, modulus of elasticity, energy to failure and thickness of skin from 10 affected and 6 unaffected horses using an Instron Universal Testing Instrument. In addition, total soluble collagen and glycosaminoglycan concentrations of skin were analysed from 13 affected and 12 unaffected horses using Sircol Soluble Collagen and Blyscan Sulfated Glycosaminoglycan assays respectively. Affected horses exhibited a two to threefold reduction in tensile strength versus unaffected horses with statistically significant differences at six of seven sample locations (P < or = 0.05). The modulus of elasticity proved to be significantly different at six of seven sample locations, energy to failure at six of seven sample locations, and skin thickness at one of seven sample locations (P < or = 0.05). Affected horses exhibited significantly higher amounts of total soluble collagen than unaffected horses (P < or = 0.05). No significant difference was demonstrated between groups for glycosaminoglycan concentration. Affected horses demonstrated uniformly weaker skin across sample locations, indicating the biomechanical properties of HERDA are not regionally confined to specific areas of the horses' skin.

• Effect of collagen hydrolysate on chondrocyte-seeded agarose constructs.

  Authors: Steven H Elder, Ali Borazjani

  Bio-medical materials and engineering. 01/2009; 19(6):409-14.

  The mechanical properties of engineered cartilage are strongly dependent on collagen content, but the collagen to glycosaminoglycan ratio in engineered cartilage is often much lower than that of theThe mechanical properties of engineered cartilage are strongly dependent on collagen content, but the collagen to glycosaminoglycan ratio in engineered cartilage is often much lower than that of the native tissue. Therefore culture medium supplements which increase collagen production by chondrocytes are of interest. It had previously been reported that collagen hydrolysate stimulated type II collagen biosynthesis in short-term, high density monolayer chondrocyte cultures. It was hypothesized that collagen hydrolysate added to the culture medium of three dimensional chondrocyte-agarose constructs would enhance their mechanical properties. Porcine articular chondrocytes were embedded in 2% agarose and cultured for up to 6 weeks with and without 1 mg/ml collagen hydrolysate. The instantaneous compressive modulus and equilibrium compressive modulus were significantly lower in the collagen hydrolysate-treated constructs, consistent with the finding of lower collagen and GAG content. Contrary to our hypothesis, our results indicate that 1 mg/ml collagen hydrolysate may actually inhibit macromolecule biosynthesis and be detrimental to the mechanical properties of long term chondrocyte-agarose constructs.

• Variation of diameter distribution, number density, and area fraction of fibrils within five areas of the rabbit patellar tendon.

  Authors: Lakiesha N Williams, Steven H Elder, Mark F Horstemeyer, David Harbarger

  Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft. 08/2008;

  The purpose of this investigation is to show microstructural information at various regions within the rabbit patellar tendon. The properties of the rabbit patellar tendon are well documentedThe purpose of this investigation is to show microstructural information at various regions within the rabbit patellar tendon. The properties of the rabbit patellar tendon are well documented mechanically, but detailed information at the microscopic level is not available. Increasing attention has been directed to soft tissue microscopy as the demand for development of biologically inspired materials increases. Microstructural examination of the tendon fibrils is performed to provide further insight into understanding of the structure to function relations within the rabbit patellar tendon. Limited studies on rabbit patellar tendon collagen fibrils at the microscopic level have been computed. Furthermore, evaluation of structure-function relations in multiple regions of any given specimen of a particular tissue type has not been conducted. In this study the number density, area fraction, and diameter distribution of collagen fibrils have been determined. Overall, this examination showed considerable variation within each section of the tendon. Correlating these structural results with mechanical tests of the tendon portions in the various regions could provide additional information on the mechanics of the rabbit tendon as well as insight into development of artificial tissue constructs.

• Influence of hydrostatic and distortional stress on chondroinduction.

  Authors: Steven H Elder, Joon Wan Shim, Ali Borazjani, Hess M Robertson, Kathryn E Smith, James N Warnock

  Biorheology. 02/2008; 45(3-4):479-86.

  Undifferentiated connective tissue that arises during embryonic development and some healing processes contains pluripotent mesenchymal stem cells. It is becoming increasingly evident that theUndifferentiated connective tissue that arises during embryonic development and some healing processes contains pluripotent mesenchymal stem cells. It is becoming increasingly evident that the mechanical environment is an important differentiation factor for these cells. In our laboratory, we have focused on the potential for mechanical signals to induce chondrogenic differentiation of mesenchymal stem cells. Using C3H10T1/2 cells as a model, we have investigated the influence of hydrostatic pressure, equibiaxial contraction, and centrifugal pressure on chondroinduction. Cells responded to cyclic hydrostatic compression (5 MPa at 1 Hz) and cyclic contractile strain (15% at 1 Hz) by upregulating aggrecan and collagen type II gene expression. In addition, a preliminary study of the effects of centrifugal pressure (4.1 MPa for 30 min) suggests that it may increase cell proliferation and stimulate proteoglycan and collagen type II production. We speculate that compression, whether it is distortional or hydrostatic in nature, applied to undifferentiated connective tissue triggers differentiation toward a chondrocyte-like phenotype and production of a less permeable extracellular matrix which is capable of sustaining increasingly higher hydrostatic fluid pressure for compressive load support.

• The anisotropic compressive mechanical properties of the rabbit patellar tendon.

  Authors: Lakiesha N Williams, Steven H Elder, J L Bouvard, M. F. Horstemeyer

  Biorheology. 02/2008; 45(5):577-86.

  In this study, we examine the transverse and longitudinal compressive mechanical behavior of the rabbit patellar tendon. The anisotropic compressive properties are of interest, because compressionIn this study, we examine the transverse and longitudinal compressive mechanical behavior of the rabbit patellar tendon. The anisotropic compressive properties are of interest, because compression occurs where the tendon attaches to bone and where the tendon wraps around bone leading to the development of fibro-cartilaginous matrices. We quantified the time dependent viscoelastic and anisotropic behavior of the tendon under compression. For both orientations, sections of patellar tendon were drawn from mature male white New Zealand rabbits in preparation for testing. The tendons were sequentially compressed to 40% strain at strain rates of 0.1, 1 and 10% strain(s) using a computer-controlled stepper motor driven device under physiological conditions. Following monotonic loading, the tendons were subjected to stress relaxation. The tendon equilibrium compressive modulus was quantified to be 19.49+/-11.46 kPa for the transverse direction and 1.11+/-0.57 kPa for the longitudinal direction. The compressive modulus at applied strain rates of 0.1, 1 and 10% strain(s) in the transverse orientation were 13.48+/-2.31, 18.24+/-4.58 and 20.90+/-8.60 kPa, respectively. The compressive modulus at applied strain rates of 0.1, 1 and 10% strain/s in the longitudinal orientation were 0.19+/-0.11, 1.27+/-1.38 and 3.26+/-3.49 kPa, respectively. The modulus values were almost significantly different for the examination of the effect of orientation on the equilibrium modulus (p=0.054). Monotonic loading of the tendon showed visual differences of the strain rate dependency; however, no significant difference was shown in the statistical analysis of the effect of strain rate on compressive modulus. The statistical analysis of the effect of orientation on compressive modulus showed a significant difference. The difference shown in the orientation analysis validated the anisotropic nature of the tendon.

• Effect of Cytoskeletal Disruption on Mechanotransduction of Hydrostatic Pressure by C3H10T1/2 Murine Fibroblasts.

  Authors: Joon W Shim, Dwayne A Wise, Steven H Elder

  The open orthopaedics journal. 01/2008; 2:155-62.

  Cyclic hydrostatic pressure of physiological magnitude (< 10 MPa) stimulates chondrogenic differentiation of mesenchymal stem cells, but mechanotransduction mechanisms are not well understood. It wasCyclic hydrostatic pressure of physiological magnitude (< 10 MPa) stimulates chondrogenic differentiation of mesenchymal stem cells, but mechanotransduction mechanisms are not well understood. It was hypothesized that an intact cytoskeleton would be required for uninhibited mechanotransduction of hydrostatic pressure. Therefore we examined the effects of drugs which selectively interfere with actin and tubulin polymerization on pressure-induced upregulation of aggrecan and col2a1 (type II collagen) mRNA expression. C3H10T1/2 cells were cultured as pellets in either 4microM cytochalasin D or 4microM nocodazole and subjected to 3 days of cyclic hydrostatic compression (1 Hz, 5 MPa, 2 h per day). Phalloidin staining and indirect immunostaining with anti alpha-tubulin antibody confirmed disruption of microfilament and microtubule assemblies, respectively. Real time RT-PCR revealed that both drugs substantially lowered the basal level of aggrecan and col2a1 mRNA, but that neither drug prevented a pressure-stimulated increase in gene expression relative to the altered basal state. Thus upregulation of macromolecular gene expression by cyclic hydrostatic pressure did not require a completely intact cytoskeleton.

• The integration of chitosan-coated titanium in bone: an in vivo study in rabbits.

  Authors: Joel D Bumgardner, Betsy M Chesnutt, Youling Yuan, Yunzhi Yang, Mark Appleford, Sunho Oh, Ronald McLaughlin, Steven H Elder, Joo L Ong

  Implant dentistry. 04/2007; 16(1):66-79.

  PROCEDURE: Much research is directed at surface modifications to enhance osseointegration of implants. A new potential coating is the biopolymer, chitosan, the deacetylated derivative of the naturalPROCEDURE: Much research is directed at surface modifications to enhance osseointegration of implants. A new potential coating is the biopolymer, chitosan, the deacetylated derivative of the natural polysaccharide, chitin. Chitosan is biocompatible, degradable, nontoxic, and exhibits osteogenic properties. The aim of this research was to investigate the hypothesis that chitosan-coated titanium supports bone formation and osseointegration. MATERIALS AND METHODS: Chitosan (1 wt% of 92.3% deacetylated chitosan in 1% acetic acid) was solution cast and bonded to rough ground titanium pins (2-mm diameterx4-mm long) via silane reactions. Calcium phosphate sputter-coated titanium and uncoated titanium pins were used as controls. Two chitosan-coated pins, and 1 each of calcium phosphate coated and uncoated pins were implanted unilaterally in the tibia of 16 adult male New Zealand white rabbits. At 2, 4, 8, and 12 weeks, undecalcified sections were histologically evaluated for healing and bone formation. RESULTS: Histological evaluations of tissues in contact with the chitosan-coated pins indicated minimal inflammatory response and a typical healing sequence of fibrous, woven bone formation, followed by development of lamellar bone. These observations were similar to those for tissues interfacing the control calcium phosphate-coated and uncoated titanium implants. Quantitative comparisons of the bone-implant interface were not possible since 31% of the implants migrated into the tibial marrow space after implantation due to insufficient cortical bone thickness to hold pins in place during healing. CONCLUSION: These data support the hypothesis that chitosan-coatings are able to develop a close bony apposition or the osseointegration of dental/craniofacial and orthopedic implants.

• Chondrocyte response to cyclic hydrostatic pressure in alginate versus pellet culture.

  Authors: Steven H Elder, Shawn W Sanders, William R McCulley, Misti L Marr, Joon W Shim, Karen A Hasty

  Journal of orthopaedic research : official publication of the Orthopaedic Research Society. 05/2006; 24(4):740-7.

  Cells are often cultured at high density (e.g., confluent monolayer and as pellets) to promote chondrogenic differentiation and to maintain the chondrocyte phenotype. They are also frequentlyCells are often cultured at high density (e.g., confluent monolayer and as pellets) to promote chondrogenic differentiation and to maintain the chondrocyte phenotype. They are also frequently suspended in hydrogels such as agarose or alginate for the same purposes. These culture techniques differ markedly with respect to frequency of direct contact between cells and overall intercellular spacing. Because these factors may significantly affect mechanotransduction, the purpose of this study was to determine if the response of articular chondrocytes to cyclic hydrostatic pressure would depend on the culture condition. Primary articular chondrocytes from young and mature pigs were cultured either as pellets or suspended in alginate beads. Both groups were exposed to dynamic hydrostatic pressure (4 MPa, 1 Hz, 5400 cycles per day) for 7 days. Cell proliferation was unaffected by pressure, but pressurized chondrocytes in pellet culture had significantly greater sGAG content and incorporated [3H]proline at a higher rate than nonpressurized controls. Electron microscopy revealed a fibrous extracellular matrix (ECM) surrounding pellets, but not cells in alginate. In addition, expression of Connexin 43 (Cx43) mRNA was slightly lower in alginate than in pellet cultures and was not significantly altered by loading. Thus, metabolic response of chondrocytes to dynamic hydrostatic pressure was affected by culture technique; chondrocytes cultured as pellets exhibited the classical anabolic response to dynamic hydrostatic pressure, but those in alginate did not. Although cell-ECM interaction could be important, the differential response is not likely attributable to differential expression of Cx43 mRNA.

• Role of the tendons of the biceps brachii and infraspinatus muscles and the medial glenohumeral ligament in the maintenance of passive shoulder joint stability in dogs.

  Authors: Brian K Sidaway, Ron M McLaughlin, Steven H Elder, Carolyn R Boyle, Edward B Silverman

  American journal of veterinary research. 10/2004; 65(9):1216-22.

  OBJECTIVE: To objectively evaluate the effect of transecting the tendon of the biceps brachii muscle (BBT), tendon of the infraspinatus muscle (IFS), or medial glenohumeral ligament (MGHL) onOBJECTIVE: To objectively evaluate the effect of transecting the tendon of the biceps brachii muscle (BBT), tendon of the infraspinatus muscle (IFS), or medial glenohumeral ligament (MGHL) on shoulder joint stability in canine cadavers. SAMPLE POPULATION: 81 forelimbs from mature dogs. PROCEDURE: Cadaver forelimbs were placed in a testing frame and axially preloaded with 4 kg of weight. Shoulder joint stability was tested in neutral joint position, flexion, and extension before and after transection of the BBT (n = 37), IFS (37), or MGHL (7). Humeral translation relative to the glenoid was induced by applying a 3-kg load in each of 3 directions (cranial, lateral, and medial) and quantitatively measured by use of an electromagnetic motion tracking system. Peak translational data were compared in each joint position before and after transection of the BBT, IFS, or MGHL. RESULTS: When tested in neutral position, the cranial, lateral, and medial translation of the humerus was significantly increased after BBT transection. In the flexed position, translation of the humerus in the cranial and lateral directions was significantly increased after BBT transection. In the extended position, the medial translation of the humerus was significantly increased after BBT transection. Complete medial luxation of all humeral heads occurred following transection of the MGHL. CONCLUSIONS AND CLINICAL RELEVANCE: The BBT contributes to passive shoulder joint stability in dogs, particularly in the neutral and flexed positions. It also provides medial stability during shoulder joint extension. Complete luxation of the joint occurs when the MGHL is transected.

• Synthesis and characterization of chitosan scaffolds for cartilage-tissue engineering.

  Authors: Steven H Elder, Dana L Nettles, Joel D Bumgardner

  Methods in molecular biology (Clifton, N.J.). 02/2004; 238:41-8.

• Effects of pico-tesla electromagnetic field treatment on wound healing in rats.

  Authors: C Todd Trostel, Ron M McLaughlin, John G Lamberth, Robert C Cooper, Steven H Elder, Roy R Pool, Cheng Gao, Joseph A Cromiak, Carolyn R Boyle

  American journal of veterinary research. 08/2003; 64(7):845-54.

  OBJECTIVE: To evaluate the effects of a pico-tesla electromagnetic field (PTEF) on healing of sutured and open skin wounds and clinicopathologic variables in rats. ANIMALS: 64 male Fischer-344 rats.OBJECTIVE: To evaluate the effects of a pico-tesla electromagnetic field (PTEF) on healing of sutured and open skin wounds and clinicopathologic variables in rats. ANIMALS: 64 male Fischer-344 rats. PROCEDURE: An incision made in the dorsal aspect of the neck was sutured (n = 32) or left open to heal (32). In each group, 16 rats were not PTEF-treated (controls). Wound treatment consisted of exposure to a PTEF once daily. Rats in each group were euthanatized at days 2, 4, 7, and 14. Wounds were evaluated via tensiometry (sutured wounds), digital planimetry (open wounds), laser Doppler perfusion imaging, bacteriologic culture, and histologic examination. Blood samples were collected from all rats for analysis. RESULTS: At day 14, sutured wounds in PTEF-treated rats were stronger (ultimate stress) and tougher (strain energy) than were sutured wounds in control rats. Open wounds in PTEF-treated rats contracted more quickly at days 2 and 4 than did those in control rats. Compared with control wounds, histologic changes (indicative of improved healing) in sutured and open wounds in PTEF-treated rats were detected as early as day 4. Laser Doppler perfusion measurements, results of CBCs, serum biochemical analyses, and bacteriologic cultures were not different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to the PTEF caused no adverse effects on clinicopathologic, histologic, or bacteriologic variables tested in this study. It appears that PTEF is a safe form of adjuvant treatment for wounds and improves strength of sutured wounds and speeds contraction of open wounds.

• Potential use of chitosan as a cell scaffold material for cartilage tissue engineering.

  Authors: Dana L Nettles, Steven H Elder, Jerome A Gilbert

  Tissue engineering. 01/2003; 8(6):1009-16.

  One of the most important factors in any tissue-engineering application is the cell substrate. The purpose of this study was the initial evaluation of chitosan, a derivative of the abundant,One of the most important factors in any tissue-engineering application is the cell substrate. The purpose of this study was the initial evaluation of chitosan, a derivative of the abundant, naturally occurring biopolymer chitin, as a cell scaffold for cartilage tissue engineering. Chitosan scaffolds having an interconnecting porous structure were easily fabricated by simple freezing and lyophilization of a chitosan solution. After rehydration of scaffolds, porcine chondrocytes were seeded onto scaffolds and cultured for up to 28 days in a rotating-wall bioreactor. Chitosan scaffolds supported cell attachment and maintenance of a rounded cell morphology. After 18 days, cells within the scaffolds had synthesized extracellular matrix in which proteoglycan and type II collagen were detected by toluidine blue staining and immunohistochemistry, respectively. Abundant extracellular matrix was found almost exclusively in the periphery of the scaffolds, as scaffold microstructure prevented cells from penetrating to interior regions. Nonetheless, the results suggest that chitosan scaffolds may be a useful alternative to synthetic cell scaffolds for cartilage tissue engineering.

• Conditioned medium of mechanically compressed chick limb bud cells promotes chondrocyte differentiation.

  Authors: Steven H Elder

  Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association. 02/2002; 7(5):538-43.

  Previous studies have demonstrated that chondrocyte differentiation can be stimulated by cyclic mechanical compression of chick limb bud cell-agarose constructs. This study reveals that mediumPrevious studies have demonstrated that chondrocyte differentiation can be stimulated by cyclic mechanical compression of chick limb bud cell-agarose constructs. This study reveals that medium collected from these compressed cultures promotes chondrocyte differentiation of non-compressed cells to approximately the same extent as compression alone. In micromass cultures of chick limb bud cells, incubation with medium from compressed cells significantly enhanced cell proliferation and the average rate of proteoglycan synthesis in a dose-dependent manner. These findings indicate that the response of undifferentiated chick limb bud cells to mechanical loading involves the secretion of one or more soluble differentiation factors. The chondrogenic activity of the conditioned medium was substantially inhibited by passage through a filter with a nominal molecular-weight cutoff (MWCO) of 10 kDa but not inhibited when using a MWCO of 30 kDa, suggesting that at least one of these factors has a molecular mass between 10 and 30 kDa.

• A new optical system for the determination of deformations and strains: Calibration characteristics and experimental results

  Authors: Kathleen A Derwin, Louis J Soslowsky, W. D. K. Green, Steven H. Elder

  Many types of optical strain measurement systems have been used for the determination of deformations and strains in soft biological tissues. The purpose of this investigation is to report a newMany types of optical strain measurement systems have been used for the determination of deformations and strains in soft biological tissues. The purpose of this investigation is to report a new optical strain measurement system developed in our laboratory which offers distinct advantages over systems developed in the past. Our optical strain system has demonstrated excellent performance in calibration and experimental tests. Calibration tests illustrate the system's accuracy to 0.05% strain at 3.52% strain and 0.18% strain at 11.74% strain. Further, this system can measure strains to within 2% measurement error for strains in a 0-11.74% range when 100 [mu]m increments of motion are used for calibration. The resolution of our system appears to be at least as good as the linear micrometer (2 [mu]m) used as a calibrating standard. Errors in strain measurement due to whole specimen rotation or translation are quantified. Rotations about an in-plane axis perpendicular to the direction of strain and translations in/out of the plane of focus result in the largest sources of error. Finally, in an in vitro biomechanical study of the rabbit Achilles tendon, experimental failure strains are 4.3 +/- 0.9% using this system. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/31312/1/0000221.pdf

• A device for imposing cyclic strain to cells growing on implant alloys.

  Authors: L Chad Winter, Jerome A Gilbert, Steven H Elder, Joel D Bumgardner

  Annals of biomedical engineering. 30(10):1242-50.

  The objective of this study was to develop a unique device for applying well-characterized cyclic, strain to cells growing on implant alloys. The device is based on the four-point bending principleThe objective of this study was to develop a unique device for applying well-characterized cyclic, strain to cells growing on implant alloys. The device is based on the four-point bending principle and utilizes an electric motor, belt, and cam system to cyclically deflect a commercially pure titanium plate with cell culture wells in the middle of the plate. Analyses demonstrated that 182 +/- 3, 366 +/- 9, and 984 +/- 7 microstrain may be cyclically generated in culture areas from 0.5 to 10 Hz for up to 72 h. UMR-106 osteoblast-like cells growing on the titanium plate were subjected to these strain magnitudes at 1.5 Hz for periods of 4 or 24 h. Cells were checked for viability, total protein as a general indicator of cell number, and alkaline phosphatase activity (ALP) as an indicator of bone cell func-tion. Cells strained at 984 +/- 7 microstrain exhibited 21%-24% more protein but 45%-49% less ALP activity than cells strained at 182 +/- 2 or 366 +/- 9 microstrain. Decreased ALP activity may indicate impaired mineralization. Results indicate the device is suitable for applying known, cyclic strain to cells growing on implant alloys and evaluating cellular responses to strain while growing on implant alloys.

• Postoperative integrity of veterinary surgical gloves.

  Authors: Ben J Character, Ron M McLaughlin, Cheryl S Hedlund, Carolyn R Boyle, Steven H Elder

  Journal of the American Animal Hospital Association. 39(3):311-20.

  A multicenter, prospective study was performed to document the incidence of defective gloves postoperatively in veterinary surgery and to correlate defects with a variety of influencing factors.A multicenter, prospective study was performed to document the incidence of defective gloves postoperatively in veterinary surgery and to correlate defects with a variety of influencing factors. Gloves were collected after surgical procedures performed by the small animal clinical services at two veterinary teaching hospitals and one institution's student surgery laboratories. Gloves were evaluated for defects using electrical resistance testing. The overall incidence of glove defects was 23.3%. Significantly more defects occurred in gloves used for nonsoft-tissue procedures and in gloves worn on the nondominant hand. Eighty-four percent of all defects occurred in procedures lasting >60 minutes. No differences were detected in the brands of gloves used nor among surgeons of different experience levels. The individuals performing the surgery were not able to accurately predict the presence of a defect in their gloves. Surgeons should remain alert for possible glove defects and consider measures such as changing gloves every 60 minutes or double-gloving to minimize potential complications.