Eric Aronowitz

Tissue-engineered intervertebral discs: MRI results and histology in the rodent spine.

OBJECT Tissue-engineered intervertebral discs (TE-IVDs) represent a new experimental approach for the treatment of degenerative disc disease. Compared with mechanical implants, TE-IVDs may better mimic the properties of native discs. The authors conducted a study to evaluate the outcome of TE-IVDs implanted into the rat-tail spine using radiological parameters and histology. METHODS Tissue-engineered intervertebral discs consist of a distinct nucleus pulposus (NP) and anulus fibrosus (AF) that are engineered in vitro from sheep IVD chondrocytes. In 10 athymic rats a discectomy in the caudal spine was performed. The discs were replaced with TE-IVDs. Animals were kept alive for 8 months and were killed for histological evaluation. At 1, 5, and 8 months, MR images were obtained; T1-weighted sequences were used for disc height measurements, and T2-weighted sequences were used for morphological analysis. Quantitative T2 relaxation time analysis was used to assess the water content and T1ρ-relaxation time to assess the proteoglycan content of TE-IVDs. RESULTS Disc height of the transplanted segments remained constant between 68% and 74% of healthy discs. Examination of TE-IVDs on MR images revealed morphology similar to that of native discs. T2-relaxation time did not differ between implanted and healthy discs, indicating similar water content of the NP tissue. The size of the NP decreased in TE-IVDs. Proteoglycan content in the NP was lower than it was in control discs. Ossification of the implanted segment was not observed. Histological examination revealed an AF consisting of an organized parallel-aligned fiber structure. The NP matrix appeared amorphous and contained cells that resembled chondrocytes. CONCLUSIONS The TE-IVDs remained viable over 8 months in vivo and maintained a structure similar to that of native discs. Tissue-engineered intervertebral discs should be explored further as an option for the potential treatment of degenerative disc disease.

Assessment of intervertebral disc degeneration based on quantitative magnetic resonance imaging analysis: an in vivo study.

Study Design. Animal experimental study. Objective. To evaluate a novel quantitative imaging technique for assessing disc degeneration. Summary of Background Data. T2-relaxation time (T2-RT) measurements have been used to assess disc degeneration quanti-tatively. T2 values correlate with the water content of intervertebral disc tissue and thereby allow for the indirect measurement of nucleus pulposus (NP) hydration. Methods. We developed an algorithm to subtract out magnetic resonance imaging (MRI) voxels not representing NP tissue on the basis of T2-RT values. Filtered NP voxels were used to measure nuclear size by their amount and nuclear hydration by their mean T2-RT. This technique was applied to 24 rat-tail intervertebral discs (IVDs), which had been punctured with an 18-gauge needle according to different techniques to induce varying degrees of degeneration. NP voxel count and average T2-RT were used as parameters to assess the degeneration process at 1 and 3 months postpuncture. NP voxel counts were evaluated against radiograph disc height measurements and qualitative MRI studies on the basis of the Pfirrmann grading system. Tails were collected for histology to correlate NP voxel counts to histological disc degeneration grades and to NP cross-sectional area measurements. Results. NP voxel count measurements showed strong correlations to qualitative MRI analyses (R2 = 0.79, P < 0.0001), histological degeneration grades (R2 = 0.902, P < 0.0001), and histological NP cross-sectional area measurements (R2 = 0.887, P < 0.0001). In contrast to NP voxel counts, the mean T2-RT for each punctured group remained constant between months 1 and 3. The mean T2-RTs for the punctured groups did not show a statistically significant difference from those of healthy IVDs (63.55 ms ± 5.88 ms mo 1 and 62.61 ms ± 5.02 ms) at either time point. Conclusion. The NP voxel count proved to be a valid parameter to assess disc degeneration quantitatively in a needle puncture model. The mean NP T2-RT does not change significantly in needle-puncture–induced degenerated IVDs. IVDs can be segmented into different tissue components according to their innate T2-RT. Level of Evidence: N/A

Genetic modification of neurons to express bevacizumab for local anti-angiogenesis treatment of glioblastoma

The median survival of glioblastoma multiforme (GBM) is approximately 1 year. Following surgical removal, systemic therapies are limited by the blood–brain barrier. To circumvent this, we developed a method to modify neurons with the genetic sequence for therapeutic monoclonal antibodies using adeno-associated virus (AAV) gene transfer vectors, directing persistent, local expression in the tumor milieu. The human U87MG GBM cell line or patient-derived early passage GBM cells were administered to the striatum of NOD/SCID immunodeficient mice. AAVrh.10BevMab, an AAVrh.10-based vector coding for bevacizumab (Avastin), an anti-human vascular endothelial growth factor (VEGF) monoclonal antibody, was delivered to the area of the GBM xenograft. Localized expression of bevacizumab was demonstrated by quantitative PCR, ELISA and western blotting. Immunohistochemistry showed that bevacizumab was expressed in neurons. Concurrent administration of AAVrh.10BevMab with the U87MG tumor reduced tumor blood vessel density and tumor volume, and increased survival. Administration of AAVrh.10BevMab 1 week after U87MG xenograft reduced growth and increased survival. Studies with patient-derived early passage GBM primary cells showed a reduction in primary tumor burden with an increased survival. These data support the strategy of AAV-mediated central nervous system gene therapy to treat GBM, overcoming the blood–brain barrier through local, persistent delivery of an anti-angiogenesis monoclonal antibody.

The Potential of High Resolution Magnetic Resonance Microscopy in the Pathologic Analysis of Resected Breast and Lymph Tissue.

Pathologic evaluation of breast specimens requires a fixation and staining procedure of at least 12 hours duration, delaying diagnosis and post-operative planning. Here we introduce an MRI technique with a custom-designed radiofrequency resonator for imaging breast and lymph tissue with sufficient spatial resolution and speed to guide pathologic interpretation and offer value in clinical decision making. In this study, we demonstrate the ability to image breast and lymphatic tissue using 7.0 Tesla MRI, achieving a spatial resolution of 59 × 59 × 94 μm3 with a signal-to-noise ratio of 15–20, in an imaging time of 56 to 70 minutes. These are the first MR images to reveal characteristic pathologic features of both benign and malignant breast and lymph tissue, some of which were discernible by blinded pathologists who had no prior training in high resolution MRI interpretation.

Magnetic Resonance Microscopy May Enable Distinction Between Normal Histomorphological Features and Prostate Cancer in the Resected Prostate Gland.

To determine imaging protocol parameters for characterization of prostate tissue at histological length scales.