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

Abstract

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.

Degenerative changes of the canine cervical spine after discectomy procedures, an in vivo study

“…Compared to our study, it appears that smaller puncture defects with retained NP tissue induce less degenerative changes than incising the AF with complete NP removal. However, similar studies in rabbit and rat demonstrated that puncture defects lead to terminal degenerative changes over time [16, 39]. They have also shown that the AF has a very low intrinsic healing capability [40, 41] and that residual NP tissue can herniate through annular needle puncture defects [16] over time.…”

“…This study is a subgroup analysis of an in vivo study evaluating tissue engineered intervertebral discs implanted in the beagle cervical spine [16] after undergoing a discectomy procedure. In this report we only include the control group of the main study which simply underwent a discectomy procedure without disc implantation.…”

Does a small size needle puncture cause intervertebral disc changes?

“…Opposing, other authors, such as, Grunert et al 12 observed a good correlation between histological damage and injury suggested by the MRI.…”

Bioprinting: An Industrial Perspective

“…Using this approach, Reiffel et al used the scanned image of a child's ear to create a seven-part mold that was 3D-printed from acrylonitrile butadiene styrene using a Stratasys FDM 2000 3D printer [21]. Grunert and coworkers took a similar approach in the fabrication of 3D intervertebral discs, created with two cell types suspended in alginate or collagen hydrogels [22,23]. After 3-5 days in culture, the ears were implanted into immunocompromised rodents, where cell-comprising constructs demonstrated superiority over the acellular constructs with respect to shape retention, overall weight, and development of cartilage within 3 months of implantation [21].…”