Tae-Hong Lim

Axial compressive loads whose direction changes along the spinal curvature (so called compressive follower loads (CFLs)) was postulated as a normal physiological load in the lumbar spine in the literature. Computational analyses were conducted in this study using finite element and optimization models of the spinal system incorporating 244 fascicles of back muscles. It was feasible to find optimum solutions for spinal muscle forces generating CFLs in the lumbar spine in 3‐D postures of neutral standing, flexion 40°, extension 10°, axial rotation 10°, or lateral bending 30°. FE analyses demonstrated that the lumbar spine can be in a stable condition not under all CFL generating muscle forces but under those producing CFLs along a curve parallel to the spinal curvature located in the vicinity of the base spinal curve constructed by connecting the geometrical centers of the vertebral bodies. It was also possible to estimate the stable range of the relative location of such CFL curve to the base spinal curve. These results suggest that the lumbar spine in various 3‐D postures can be stabilized by spinal muscles that generate CFLs in the spine, which at least in part supports the hypothesis of CFLs as a physiological load in the lumbar spine. This article is protected by copyright. All rights reserved

We recently introduced a novel pluronic F127 and hyaluronic acid-based hydrogel (HG) designed to deliver a broad range of therapeutics. The reverse-thermal responsive HG exhibits physical properties that seem to be ideal for the local delivery of drug- and cell-based therapies to specific anatomic sites through percutaneous injection. However, questions related to the HG's safety and efficacy must first be addressed. To address these issues, we performed standard in vitro cytotoxicity and drug release tests and in vivo biocompatibility tests in a rat model. In addition, we determined whether the HG was an effective stem cell carrier in a rat cartilage defect model. We found that the HG showed viability and biocompatibility levels similar to those reported for F127 or hyaluronic acid alone. In vitro drug release studies with bupivacaine, a drug used clinically for local pain relief, revealed that after an initial burst bupivacaine was released continuously for 10 days. Stem cells loaded in the HG were retained in situ and stimulated cartilage regeneration in experimental defects. Taken as a whole, these findings support further efforts to develop the HG as a versatile system for the delivery of a wide range of therapeutic agents in humans. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 101B: 1508–1515, 2013.

Mechanical stress on the intervertebral disc (IVD) may contribute significantly to IVD degeneration, although its pathomechanism has not been fully understood. The purpose of this study was to test the hypothesis that sustained application of static shear force would result in IVD degeneration with minimum injury. We applied shear force on the rat lumbar spine (L5–L6) using a custom-designed loading device for 1 or 2 weeks. Degenerative changes such as nucleus pulposus cavity loss and border disruption were observed from the histology sections, indicating that the application of sustained dorsoventral shear force on the L6 vertebra induced degeneration of the IVDs in L5–L6 and adjacent levels of motion segment in 1 and 2 weeks. The findings of the present study could be useful for gaining a more relevant understanding of the biomechanical load factors of IVD degeneration not only for enabling better therapeutic interventions but also reducing the risk of low back injury.

The accuracy of quantitative real-time RT-PCR (qRT-PCR) is often influenced by experimental artifacts, resulting in erroneous expression profiles of target genes. The practice of employing normalization using a reference gene significantly improves reliability and its applicability to molecular biology. However, selection of an ideal reference gene(s) is of critical importance to discern meaningful results. The aim of this study was to evaluate the stability of seven potential reference genes (Actb, GAPDH, 18S rRNA, CycA, Hprt1, Ywhaz, and Pgk1) and identify most stable gene(s) for application in tissue culture research using the rat and rabbit intervertebral disc (IVD).

Possible solution to the long-term control of the low back pain (LBP) would be by using an injectable pain drug carrier that can be delivered locally. The drug can be released in a controlled manner. It is also allowed to inject repeatedly more drugs percutaneously with a minimal invasion. The main objective of this study was to develop such a drug delivery system (DDS) for long-term control of discogenic LBP. The DDS consists of in situ forming hydrogel matrix (Pluronic F127® plus sodium hyaluronate) containing microspheres (MS). The solid MS were used for long-term release of the drugs. Both hydrogel matrix and MS contained a model drug, bupivacaine base (BB). The phase transition (liquid at room temperature, gel at around body temperature) could be manipulated by changing the composition of the hydrogel. In vitro test showed that ∼3% (w/w) of the BB loaded to MS were released during 42 days, demonstrating a good potential for sustained release of bupivacaine. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010