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  1. Total disc replacement using tissue‐engineered intervertebral discs (TE‐IVDs) may offer a biological alternative to treat radiculopathy caused by disc degeneration. A composite TE‐IVD was previously developed and evaluated in rat tail and beagle cervical spine models in vivo. Although cell viability and tissue integration into host tissue were promising, significant implant displacement occurred at multiple spinal levels. The goal of the present study was to assess the effects of a resorbable plating system on the stiffness of motion segments and stability of tissue‐engineered implants subjected to axial compression. Canine motion segments from levels C2/C3 to C5/C6 were assessed as intact (CTRL), after discectomy (Dx), with an implanted TE‐IVD only (PLATE−), and with a TE‐IVD combined with an attached resorbable plate (PLATE+). Segments under PLATE+ conditions fully restored separation between endplates and showed significantly higher compressive stiffness than segments under PLATE− conditions. Plated segments partially restored more than 25% of the CTRL motion segment stiffness. Plate attachment also prevented implant extrusion from the disc space at 50% compressive strain, and this effect was more significant in segments from levels C3/C4 when compared to segments from level C5/C6. These results suggest that stabilization of motion segments via resorbable plating assists TE‐IVD retention in the disc space while allowing the opportunity for implants to fully integrate into the host tissue and achieve optimal restoration of spine biomechanics.

     
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  2. Abstract Background

    In vitro studies using nucleus pulposus (NP) cells are commonly used to investigate disc cell biology and pathogenesis, or to aid in the development of new therapies. However, lab‐to‐lab variability jeopardizes the much‐needed progress in the field. Here, an international group of spine scientists collaborated to standardize extraction and expansion techniques for NP cells to reduce variability, improve comparability between labs and improve utilization of funding and resources.

    Methods

    The most commonly applied methods for NP cell extraction, expansion, and re‐differentiation were identified using a questionnaire to research groups worldwide. NP cell extraction methods from rat, rabbit, pig, dog, cow, and human NP tissue were experimentally assessed. Expansion and re‐differentiation media and techniques were also investigated.

    Results

    Recommended protocols are provided for extraction, expansion, and re‐differentiation of NP cells from common species utilized for NP cell culture.

    Conclusions

    This international, multilab and multispecies study identified cell extraction methods for greater cell yield and fewer gene expression changes by applying species‐specific pronase usage, 60–100 U/ml collagenase for shorter durations. Recommendations for NP cell expansion, passage number, and many factors driving successful cell culture in different species are also addressed to support harmonization, rigor, and cross‐lab comparisons on NP cells worldwide.

     
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