Biomedical subjects

Carol Muehleman

Publications and source records attributed to Carol Muehleman.

At least 19 recordsLinked to original sources

PubMed2006

Effects of growth differentiation factor-5 on the intervertebral disc--in vitro bovine study and in vivo rabbit disc degeneration model study.

STUDY DESIGN: In vitro studies on the effects of recombinant human growth and differentiation factor-5 (rhGDF-5) on matrix metabolism of bovine intervertebral disc cells and an in vivo study on the effect of rhGDF-5 in the rabbit anular puncture model. OBJECTIVE: To determine the reparative capacity of rhGDF-5 on the intervertebral disc. SUMMARY OF BACKGROUND DATA: The in vitro and in vivo effects of rhGDF-5, a crucial protein in the developing musculoskeletal system, on repair of the degenerated intervertebral disc remain unidentified. METHODS: In vitro, bovine nucleus pulposus and anulus fibrosus cells were cultured with or without rhGDF-5 (100 or 200 ng/mL). On days 7, 14, and 21, the contents of deoxyribonucleic acid and proteoglycan, and the synthesis of proteoglycan and collagen were assessed. In vivo, 16 adolescent New Zealand white rabbits received anular punctures in 2 lumbar discs. Four weeks later, phosphate buffered saline or rhGDF-5 (10 ng, 1 and 100 mug) was injected into the nucleus pulposus. The rabbits were followed up for 16 weeks for disc height, magnetic resonance imaging, and histologic grading. RESULTS: In vitro, rhGDF-5 increased the deoxyribonucleic acid and proteoglycan contents of both cell types significantly after day 14. rhGDF-5 at 200 ng/mL significantly stimulated proteoglycan synthesis (nucleus pulposus: +138%, anulus fibrosus: +24%) and collagen synthesis (nucleus pulposus: +95%, anulus fibrosus: +23%) at day 21. In vivo, the injection of rhGDF-5 resulted in a restoration of disc height, improvement of magnetic resonance imaging scores, and histologic grading scores with statistical significance (P < 0.05-0.001). CONCLUSION: A single injection of rhGDF-5 has a reparative capacity on intervertebral discs, presumably based on its effects to enhance extracellular matrix production in vitro.

Animals↗

PubMed2006

Nerve fiber ingrowth into scar tissue formed following nucleus pulposus extrusion in the rabbit anular-puncture disc degeneration model: effects of depth of puncture.

STUDY DESIGN: In vivo histologic study of nerve ingrowth in the rabbit anular-puncture disc degeneration model. OBJECTIVE: To examine innervation of intervertebral discs and surrounding tissues in the rabbit anular-puncture model with various magnitudes of injury. SUMMARY OF BACKGROUND DATA: A rabbit anular-puncture model of disc degeneration was recently established. However, to our knowledge, the neuropathologic changes in the degenerated disc and surrounding tissues in this model have not been examined. METHODS: Anular punctures with an 18-gauge needle at depths of 1 and 5 mm were randomly performed at the L2-L3 or L4-L5 discs in New Zealand white rabbits (n = 16; 3.0-3.5 kg). The degree of disc degeneration was followed radiographically, and was further evaluated by magnetic resonance imaging and histology at sacrifice 4 or 12 weeks after the puncture. To identify nerve ingrowth into the discs, the L2-L3 to L4-L5 discs were immunostained with an antibody against protein gene product 9.5, a general marker for nerve fibers. RESULTS: Significant decreases in disc height and signal intensity in magnetic resonance imaging were observed only in the 5 mm punctured discs (P < 0.05). In all the discs, including nonpunctured control discs, protein gene product 9.5-immunoreactive fibers were only occasionally observed in the outermost part of the anulus fibrosus. In the 5 mm punctured discs, nucleus pulposus tissues were extruded, and scar tissues formed outside the discs. No nerve ingrowth into the needle track lesion at the anular puncture site was observed. However, protein gene product 9.5-immunoreactive fibers were observed in scar tissues on the surface of the puncture site. This finding was more evident in the 5 mm than in the 1 mm punctured discs (P < 0.05). CONCLUSIONS: This study indicates that in the rabbit anular-puncture disc degeneration model, disc degeneration associated with a higher nerve growth into the scar tissue was more evident when induced by a 5 mm than a 1 mm puncture. Although nerve ingrowth was observed in the extruded disc tissue, nerve ingrowth into the outer anulus, which has been reported in patients with discogenic pain, was not observed during the short observation period in this disc degeneration model. The limitation in assessing pain by behavior analysis or histologic evaluation of nerve ingrowth should be considered. Further studies to identify a surrogate marker of pain should be encouraged.

Animals↗

PubMed2006

Comparison of cellular response in bovine intervertebral disc cells and articular chondrocytes: effects .of lipopolysaccharide on proteoglycan metabolism.

Lipopolysaccharide (LPS) induces matrix degradation and markedly stimulates the production of several cytokines, i.e., interleukin-1beta, -6, and -10, by disc cells and chondrocytes. We performed a series of experiments to compare cellular responses of cells from the bovine intervertebral disc (nucleus pulposus and annulus fibrosus) and from bovine articular cartilage to LPS. Alginate beads containing cells isolated from bovine intervertebral discs and articular cartilage were cultured with or without LPS in the presence of 10% fetal bovine serum. The DNA content and the rate of proteoglycan synthesis and degradation were determined. In articular chondrocytes, LPS strongly suppressed cell proliferation and proteoglycan synthesis in a dose-dependent manner and stimulated proteoglycan degradation. Compared with articular chondrocytes, nucleus pulposus cells responded in a similar, although less pronounced manner. However, treatment of annulus fibrosus cells with LPS showed no significant effects on proteoglycan synthesis or degradation. A slight, but statistically significant, inhibition of cell proliferation was observed at high concentrations of LPS in annulus fibrosus cells. Thus, LPS suppressed proteoglycan synthesis and stimulated proteoglycan degradation by articular chondrocytes and nucleus pulposus cells. The effects of LPS on annulus fibrosus cells were minor compared with those on the other two cell types. The dissimilar effects of LPS on the various cell types suggest metabolic differences between these cells and may further indicate a divergence in pathways of LPS signaling and a differential sensitivity to exogenous stimuli such as LPS.

Animals↗

PubMed2006

Osteogenic protein-1 injection into a degenerated disc induces the restoration of disc height and structural changes in the rabbit anular puncture model.

STUDY DESIGN: In vivo study of the effect of injection of osteogenic protein-1 (OP-1) on a rabbit anular needle puncture model of intervertebral disc (IVD) degeneration. OBJECTIVE: To study radiographic, magnetic resonance imaging (MRI), biochemical, and histologic changes in the rabbit IVD after injection of OP-1 into the nucleus pulposus in a needle puncture disc degeneration model. SUMMARY OF THE BACKGROUND DATA: Growth factors, such as OP-1, have the ability to stimulate synthesis of proteoglycans and collagen in vitro. The in vivo injection of OP-1 into the normal rabbit IVD has increased disc height and proteoglycan content in the anulus fibrosus and nucleus pulposus. However, to our knowledge, no attempts have yet been made to determine the effects of these growth factors in an in vivo model of disc degeneration. METHODS: New Zealand adolescent white rabbits (n = 90, 8 for baseline evaluation, 82 at 8 times) received an anular puncture in 2 noncontiguous discs with an 18-gauge needle to induce disc degeneration. Four weeks later, either 5% lactose (10 microL) or OP-1 (100 microg in 10 microL 5% lactose) was injected into the center of the nucleus pulposus. The disc height was followed radiographically for up to 24 weeks after the injections. At the 2, 4, 8, 12, and 24-week times after the injection, rabbits were euthanized, and MRI of the harvested spinal columns was obtained to grade the degeneration. The discs injected with OP-1 or lactose and noninjected discs were subjected to biochemical and histologic analysis. The specimens at the 24-week time were limited to histologic evaluation. RESULTS: The anular puncture with a needle induced a consistent disc narrowing within 4 weeks. The injection of OP-1 induced a restoration of disc height at 6 weeks, which was sustained for the entire experimental period, up to 24 weeks after the injection. The injection of lactose alone did not change the course of disc narrowing over the same time. MRI grading score showed significant differences between the OP-1 and lactose groups at the 8, 12, and 24-week times, suggesting an increase in water content in the nucleus pulposus of the OP-1 group. The proteoglycan content of the nucleus pulposus and anulus fibrosus was significantly higher in the OP-1 group than in the control group. The degeneration grades of the punctured discs in the OP-1 group were significantly lower than those in the lactose group. CONCLUSION: The results of this study show the feasibility of restoring degenerative rabbit discs by a single injection of OP-1 into the nucleus pulposus. Importantly, the effects of the OP-1 injection on disc height were sustained for up to 24 weeks. The metabolic changes in the cells, following a single injection, might be sustained and, thus, induce long-term changes in disc structure. An efficacy study in large animals is required to show further that the intradiscal injection of OP-1, or bone morphogenetic proteins or growth factors with similar properties would be useful for the structural restoration of the IVD in humans.

Animals↗

PubMed2006

Anti-adhesion properties of a thrombin-based hemostatic gelatin in a canine laminectomy model: a biomechanical, biochemical, and histologic study.

STUDY DESIGN: An in vivo study on the effects of an agent for scar prevention in a dog laminectomy model. OBJECTIVE: To examine the anti-adhesion properties of a thrombin-based hemostatic gelatin (FLOSEAL; Baxter International Inc., Deerfield, IL). SUMMARY OF BACKGROUND DATA: Postlaminectomy dural adhesion sometimes causes symptomatic problems. Although a new type of hemostatic agent, a thrombin-based hemostatic gelatin, has been developed, its effect on postlaminectomy scar prevention is unknown. METHODS: A 4-level lumbar laminectomy was performed on 11 adult mongrel dogs. There were 2 levels randomly chosen to receive the thrombin-based hemostatic gelatin treatment, while the remaining levels were untreated (control). Dogs were euthanized 8 weeks after surgery. To assess the tenacity of adhesion between the dura and scar, peel-off testing was performed. Gross, biochemical, and histologic analyses were then used to examine the samples. RESULTS: Peel-off stiffness was significantly decreased in the treatment group (64.8% of the control, P = 0.032; 2-tailed unpaired t test). Histologically, there was significantly less scar tissue formation in the treatment group (P = 0.04). The gross analyses showed a trend toward a smaller amount of scar tissue and tenacity of adhesion between the dura and scar in the treatment group. Biochemically, there was a trend toward a lower collagen cross-links content in the treatment group (P = 0.07). CONCLUSIONS: The thrombin-based hemostatic gelatin decreases the tenacity of adhesion between the dura and scar at laminectomy sites.

Animals↗

PubMed2006

Multiple-image radiography for human soft tissue.

Conventional radiography only provides a measure of the X-ray attenuation caused by an object; thus, it is insensitive to other inherent informative effects, such as refraction. Furthermore, conventional radiographs are degraded by X-ray scatter that can obscure important details of the object being imaged. The novel X-ray technology diffraction-enhanced imaging (DEI) has recently allowed the visualization of nearly scatter-free images displaying both attenuation and refraction properties. A new method termed multiple-image radiography (MIR) is a significant improvement over DEI, corrects errors in DEI, is more robust to noise and produces an additional image that is entirely new to medical imaging. This new image, which portrays ultra-small-angle X-ray scattering (USAXS) conveys the presence of microstructure in the object, thus differentiating homogeneous tissues from tissues that are irregular on a scale of micrometres. The aim of this study was to examine the use of MIR for evaluation of soft tissue, and in particular to conduct a preliminary investigation of the USAXS image, which has not previously been used in tissue imaging.

Arthrography↗

PubMed2006

A computed tomography implementation of multiple-image radiography.

Conventional x-ray computed tomography (CT) produces a single volumetric image that represents the spatially variant linear x-ray attenuation coefficient of an object. However, in many situations, differences in the x-ray attenuation properties of soft tissues are very small and difficult to measure in conventional x-ray imaging. In this work, we investigate an analyzer-based imaging method, called computed tomography multiple-image radiography (CT-MIR), which is a tomographic implementation of the recently proposed multiple-image radiography method. The CT-MIR method reconstructs concurrently three physical properties of the object. In addition to x-ray attenuation, CT-MIR produces volumetric images that represent the refraction and ultrasmall-angle scattering properties of the object. These three images can provide a rich description of the object's physical properties that are revealed by the probing x-ray beam. An imaging model for CT-MIR that is based on the x-ray transform of the object properties is established. The CT-MIR method is demonstrated by use of experimental data acquired at a synchroton radiation imaging beamline, and is compared to the pre-existing diffraction-enhanced imaging CT method. We also investigate the merit of an iterative reconstruction method for use with future clinical implementations of CT-MIR, which we anticipate would be photon limited.

Humans↗

PubMed2006

Characterization of lesions of the talus and description of tram-track lesions.

BACKGROUND: The ankle joint, although not prone to primary osteoarthritis (OA), is known to be susceptible to secondary OA as a result of sports injuries and other trauma. Unlike the knee joint, a thorough investigation of talar cartilage lesions has not been previously reported. METHODS: One hundred and five human tali from 67 donors were used to determine the type and location of the most common lesions through gross examination, radiography, diffraction enhanced imaging, and histology. "tram-track lesions" also are described. RESULTS: The most anterior and posterior regions of the talar dome, along with the medial and lateral borders of the dome were most affected by cartilage degeneration. These are regions that appear to be most subjected to frictional forces from their articulating counterparts during high stress activities that move articulating surfaces slightly out of congruence with each other. One particularly striking cartilage degeneration pattern that, to our knowledge, has not been described histologically, is the tram-track lesion. These lesions displayed a longitudinally oriented groove in the cartilage, running from anterior to posterior, in which the deepest portion of the groove was located in the middle of the anterior-posterior axis of the talus. Several of these cartilage grooves had a bony ridge beneath, mirroring the cartilage groove whereas others did not. This suggests that the cartilage groove develops before the interruption of the tidemark (border between the calcified and uncalcified cartilage). In specimens for which the articulating tibial articular surface was available, (17) it was found that the tibia displayed small osteophytes on the anterior articular margin that exactly corresponded to their articulation with the talar cartilage grooves as the ankle articulated through plantar flexion and dorsiflexion. CONCLUSION: This study provides an in-depth histologic and gross anatomic look at the most common lesions of the talus of the ankle joint. In particular, the "tram-track" lesion was shown to be a consequence of its tibial articulation and to include both subchondral bone and articular cartilage changes.

Adult↗

PubMed2005

A novel rabbit model of mild, reproducible disc degeneration by an anulus needle puncture: correlation between the degree of disc injury and radiological and histological appearances of disc degeneration.

STUDY DESIGN: An in vivo study to radiographically and histologically assess a new method of induction of disc degeneration. OBJECTIVE.: To establish a reproducible rabbit model of disc degeneration by puncturing the anulus with needles of defined gauges and to compare it to the classic stab model. SUMMARY OF BACKGROUND DATA: New treatment approaches to disc degeneration are of great interest. Although animal models for disc degenerative disease exist, the quantitative measurement of disease progression remains difficult. A reproducible, progressive disc degeneration model, which can be induced in a reasonable time frame, is essential for development of new therapeutic interventions. METHODS: The classic anular stab model and the new needle puncture model were used in the rabbit. For the needle puncture model, 3 different gauges of needle (16G, 18G, and 21G) were used to induce an injury to the disc to a depth of 5 mm. Radiographic and histologic analyses were performed; magnetic resonance images were also assessed in the needle puncture model. RESULTS: Significant disc space narrowing was observed as early as 2 weeks after stabbing in the classic stab model; there was no further narrowing of the disc space. In the needle puncture model, all needle sizes tested induced a slower and more progressive decrease in disc height than in the classic stab model. The magnetic resonance imaging supported the results of disc height data. CONCLUSIONS: The needle puncture approach, using 16G to 21G needles, resulted in a reproducible decrease of disc height and magnetic resonance imaging grade. The ease of the procedure and transfer of the methodology will benefit researchers studying disc degeneration.

Animals↗

PubMed2005

Reliability of diffraction enhanced imaging for assessment of cartilage lesions, ex vivo.

OBJECTIVE: The assessment of articular cartilage integrity is of value for the detection of early degenerative joint disease in both the clinical and the research settings. It was the purpose of this study to determine the accuracy and reliability of identifying articular cartilage defects through Diffraction Enhanced Imaging (DEI), a high contrast radiographic imaging technique. DEI provides two new sources of image contrast to radiography: refraction and scatter rejection, besides the absorption of conventional radiography. DESIGN: Cadaveric tali were DEI imaged in the anterior-posterior position at the National Synchrotron Light Source. Two independent observers provided gross score evaluations (on a five point scale) of the trochlear surfaces. The DEI image of each trochlear surface was then graded (on a five point scale) by two additional independent observers who were blinded with regard to the gross evaluation of the articular surfaces. Inter-observer agreement for DEI grades was assessed with the weighted kappa statistic. Correlation of diffraction enhanced image score to the gross score was assessed with Spearman correlation coefficient. RESULTS: The defects of articular cartilage of talar trochleae could be visualized through DEI. The Spearman correlation of gross grades with DEI grades on the 165 talar regions for observers 1 and 2 were 0.91 and 0.91, respectively. The overall weighted kappa value for inter-observer agreement was 0.93, thus considered high agreement. CONCLUSIONS: DEI is accurate and reliable for detection of articular cartilage defects ex vivo. Even early stages of degeneration of cartilage can be visualized with this high contrast technique. Future studies will focus on the application of DEI to the identification of such lesions in vivo.

Aged↗

PubMed2004

X-ray detection of structural orientation in human articular cartilage.

OBJECTIVE: To determine the feasibility of detecting the structural orientation in cartilage with Diffraction Enhanced X-Ray Imaging. DESIGN: Human tali and femoral head specimens were Diffraction Enhanced X-Ray Imaged (DEI) at the SYRMEP beamline at Elettra at various energy levels to detect the architectural arrangement of collagen within cartilage. DEI utilizes a monochromatic and highly collimated beam, with an analyzer crystal that selectively weights out photons according to the angle they have been deviated with respect to the original direction. This provides images of very high contrast, and with the rejection of X-ray scatter. RESULTS: DEI allowed the visualization of articular cartilage and a structural orientation, resembling arcades, within. CONCLUSION: Our diffraction enhanced images represent the first radiographic detection of the structural orientation in cartilage. Our data are in line with previous studies on the structural organization of joint cartilage. They confirm the model of a vaulting system of collagen fiber bundles interrupted by proteoglycan aggregates.

Cartilage, Articular↗

PubMed2003

Multiple-image radiography.

Conventional radiography produces a single image of an object by measuring the attenuation of an x-ray beam passing through it. When imaging weakly absorbing tissues, x-ray attenuation may be a suboptimal signature of disease-related information. In this paper we describe a new phase-sensitive imaging method, called multiple-image radiography (MIR), which is an improvement on a prior technique called diffraction-enhanced imaging (DEI). This paper elaborates on our initial presentation of the idea in Wernick et al (2002 Proc. Int. Symp. Biomed. Imaging pp 129-32). MIR simultaneously produces several images from a set of measurements made with a single x-ray beam. Specifically, MIR yields three images depicting separately the effects of refraction, ultra-small-angle scatter and attenuation by the object. All three images have good contrast, in part because they are virtually immune from degradation due to scatter at higher angles. MIR also yields a very comprehensive object description, consisting of the angular intensity spectrum of a transmitted x-ray beam at every image pixel, within a narrow angular range. Our experiments are based on data acquired using a synchrotron light source; however, in preparation for more practical implementations using conventional x-ray sources, we develop and evaluate algorithms designed for Poisson noise, which is characteristic of photon-limited imaging. The results suggest that MIR is capable of operating at low photon count levels, therefore the method shows promise for use with conventional x-ray sources. The results also show that, in addition to producing new types of object descriptions, MIR produces substantially more accurate images than its predecessor, DEI. MIR results are shown in the form of planar images of a phantom and a biological specimen. A preliminary demonstration of the use of MIR for computed tomography is also presented.

Absorptiometry, Photon↗

PubMed2003

Radiography of rabbit articular cartilage with diffraction-enhanced imaging.

Articular cartilage of synovial joints is not visible with conventional X-ray imaging. Hence, the gradual degeneration and destruction of articular cartilage, which is characteristic of degenerative joint diseases, is only detected at a late stage when the cartilage is lost and the joint space that it once occupied narrows. The development of an X-ray imaging technique that could detect both the degenerative cartilage and bone features of joint diseases is of special interest. Here we show, for the first time, that a high-contrast imaging technique, diffraction-enhanced X-ray imaging (DEI), allows the visualization of articular cartilage of both disarticulated and articulated rabbit knee joints. Furthermore, a single cartilage lesion can be visualized within an intact joint. The results suggest that DEI has the potential to be of use in the study of cartilage degeneration.

Animals↗

PubMed2003

Radiography of soft tissue of the foot and ankle with diffraction enhanced imaging.

Non-calcified tissues, including tendons, ligaments, adipose tissue and cartilage, are not visible, for any practical purposes, with conventional X-ray imaging. Therefore, any pathological changes in these tissues generally necessitate detection through magnetic resonance imaging or ultrasound technology. Until recently the development of an X-ray imaging technique that could detect both bone and soft tissues seemed unrealistic. However, the introduction of diffraction enhanced X-ray imaging (DEI) which is capable of rendering images with absorption, refraction and scatter rejection qualities has allowed detection of specific soft tissues based on small differences in tissue densities. Here we show for the first time that DEI allows high contrast imaging of soft tissues, including ligaments, tendons and adipose tissue, of the human foot and ankle.

Adipose Tissue↗

PubMed2003

X-ray diffraction of the molecular substructure of human articular cartilage.

The molecular substructure of human articular cartilage has been difficult to study because of its complex composition and high degree of hydration. Using newly available small-angle X-ray diffraction (SAX) instrumentation that allows very short exposure times (0.1 to 10 sec), we have obtained spatially resolved information concerning the disposition of collagen fibers in the matrix of cartilage from the normal and osteoarthritic ankle and knee joints of human cadavers. Surprisingly, in zones of cartilage damage, such as in preosteoarthritic lesions or in the severely degenerated cartilage of osteoarthritic joints, collagen fibers of the deeper layers tended to be reoriented from the vertical. The SAX technique represents a nondestructive method of analyzing the collagen network in cartilage. Taken together, the data suggest a rigid control mechanism for the fiber network and an extensive passive reorganization of the collagen fiber orientation in diseased joint cartilage.

Ankle Joint↗

PubMed2002

Immunohistochemical localization of osteogenetic protein (OP-1) and its receptors in rabbit articular cartilage.

We assessed the distribution and relative immunohistochemical staining intensity of the bone morphogenetic protein-7, osteogenic protein-1 (OP-1), in its pro- and mature forms, and four of its receptors, type I (ALK-2, ALK-3, and ALK-6) and type II in normal adolescent New Zealand White rabbit articular cartilage. Expression of the protein and its receptors was also examined in cartilage from joints that had been previously subjected to cartilage matrix degradation. Pro-OP-1 was moderately expressed in chondrocytes of the superficial, middle, and deep cartilage zones and in the osteocytes. The expression of mature OP-1 was similar, with the exception of less staining in the superficial zone of cartilage. Expression of these two forms of OP-1 was enhanced in the middle and deep cartilage zones after catabolic challenge. The type I receptor, ALK-6, displayed the strongest staining of the receptors in both cartilage and bone, whereas ALK-2 displayed the weakest staining. No differences were observed in the receptor staining levels after catabolic challenge. This study shows that OP-1 and its receptors have been identified in rabbit articular cartilage and bone, suggesting a possible role for this pathway in cartilage and bone homeostasis.

Activin Receptors, Type I↗

PubMedDate not supplied

Radiography of soft tissue of the foot and ankle with diffraction enhanced imaging.

Ankle↗

PubMedDate not supplied

Refraction effects of diffraction-enhanced radiographic imaging: a new look at bone.

The objective of this study was to demonstrate the ability of a novel radiographic technology-diffraction-enhanced imaging-to detect contrast in bone tissue through absorption, refraction, and scatter rejection. Diffraction-enhanced imaging uses a synchrotron x-ray beam to produce images of high contrast by measuring the object's refraction and ultra-small angle scattering of x-rays in addition to the attenuation measured by conventional radiography. We present evidence that diffraction-enhanced imaging provides contrast enhancement at the edges of cortical and cancellous bone and a three-dimensional appearance of trabeculae.

Animals↗