The relative importance of vertebral bone density and disc degeneration in spinal flexibility and interbody implant performance. An in vitro study

An in vitro biomechanical investigation in the human lumbar spine focuses on the functional significance of vertebral bone density and intervertebral disc degenerations.

Little-known Swiss contributions to the description, diagnosis, and surgery of lumbar disc disease before the Mixter and Barr era

The understanding of lumbar spine pathologies made substantial progress at the turn of the twentieth century. The authors review the original publication of Otto Veraguth in 1929 reporting on the successful resection of a herniated lumbar disc, published exclusively in the German language. His early report is put into the historical context, and its impact on the understanding of pathologies of the intervertebral disc (IVD) is estimated. The Swiss surgeon and Nobel Prize laureate Emil Theodor Kocher was among the first physicians to describe the traumatic rupture of the IVD in 1896. As early as 1909 Oppenheim and Krause published 2 case reports on surgery for a herniated lumbar disc. Goldthwait was the first physician to delineate the etiopathogenes is between annulus rupture, symptoms of sciatica, and neurological signs in his publication of 1911. Further publications by Middleton and Teacher in 1911 and Schmorl in 1929 added to the understanding of lumbar spinal pathologies. In 1929, the Swiss neurologist Veraguth (surgery performed by Hans Brun) and the American neurosurgeon Walter Edward Dandy both published their early experiences with the surgical therapy of a herniated lumbar disc. Veraguth's contribution, however, has not been appreciated internationally to date. The causal relationship between lumbar disc pathology and sciatica remained uncertain for some years to come. The causal relationship was not confirmed until Mixter and Barr's landmark paper in 1934 describing the association of sciatica and lumbar disc herniation, after which the surgical treatment became increasingly popular. Veraguth was among the first physicians to report on the clinical course of a patient with successful resection of a herniated lumbar disc. His observations should be acknowledged in view of the limited experience and literature on this ailment at that time.

Correlations between severity of clinical signs and histopathological changes in 60 dogs with spinal cord injury associated with acute thoracolumbar intervertebral disc disease

The outcome of spinal surgery in dogs with absent voluntary motor function and nociception following intervertebral disc (IVD) herniation is highly variable, which likely attests to differences in the severity of spinal cord damage. This retrospective study evaluated the extent to which neurological signs correlated with histologically detected spinal cord damage in 60 dogs that were euthanased because of thoracolumbar IVD herniation. Clinical neurological grades correlated significantly with the extent of white matter damage (P<0.001). However, loss of nociception also occurred in 6/31 (19%) dogs with relatively mild histological changes. The duration of clinical signs, Schiff-Sherrington posture, loss of reflexes and pain on spinal palpation were not significantly associated with the severity of spinal cord damage. Although clinical-pathological correlation was generally good, some clinical signs frequently thought to indicate severe cord injury did not always correlate with the degree of cord damage, suggesting functional rather than structural impairment in some cases.

Far lateral lumbar disc extrusion: MRI findings and surgical treatment

This case report describes the magnetic resonance imaging (MRI) findings and the treatment of a far lateral extrusion of disc material at the sixth and seventh lumbar vertebrae (L6-L7) in a five-year-old male Alpine Dachsbracke dog referred to our hospital for investigation of the complaint of a one week progressive lameness in the left pelvic limb and poorly localized back pain. An extra-foraminal left lateral disc herniation impinging on the sixth lumbar nerve root was diagnosed by MRI examinations. Due to the far lateral position of the extruded disc material on MRI, surgical opening of the spinal canal was not necessary. Removal of the herniated soft disc material impinging on the L6 nerve root, and fenestration of the L6-L7 disc was performed laterally. To the author's knowledge 'far-lateral' disc herniation beyond the neuroforamen without any spinal canal contact has not been described in dogs until now. A complete recovery with no evidence of pain was achieved only after a couple of weeks after surgery. We acknowledge that it is possible that other pathological mechanisms may have contributed to clinical signs and to a delayed recovery.

Nonviral Gene Delivery of Growth and Differentiation Factor 5 to Human Mesenchymal Stem Cells Injected into a 3D Bovine Intervertebral Disc Organ Culture System

Intervertebral disc (IVD) cell therapy with unconditioned 2D expanded mesenchymal stem cells (MSC) is a promising concept yet challenging to realize. Differentiation of MSCs by nonviral gene delivery of growth and differentiation factor 5 (GDF5) by electroporation mediated gene transfer could be an excellent source for cell transplantation. Human MSCs were harvested from bone marrow aspirate and GDF5 gene transfer was achieved by in vitro electroporation. Transfected cells were cultured as monolayers and as 3D cultures in 1.2% alginate bead culture. MSC expressed GDF5 efficiently for up to 21 days. The combination of GDF5 gene transfer and 3D culture in alginate showed an upregulation of aggrecan and SOX9, two markers for chondrogenesis, and KRT19 as a marker for discogenesis compared to untransfected cells. The cells encapsulated in alginate produced more proteoglycans expressed in GAG/DNA ratio. Furthermore, GDF5 transfected MCS injected into an IVD papain degeneration organ culture model showed a partial recovery of the GAG/DNA ratio after 7 days. In this study we demonstrate the potential of GDF5 transfected MSC as a promising approach for clinical translation for disc regeneration.

Papain-induced in vitro disc degeneration model for the study of injectable nucleus pulposus therapy

BACKGROUND CONTEXT Proteolytic enzyme digestion of the intervertebral disc (IVD) offers a method to simulate a condition of disc degeneration for the study of cell-scaffold constructs in the degenerated disc. PURPOSE To characterize an in vitro disc degeneration model (DDM) of different severities of glycosaminoglycans (GAG) and water loss by using papain, and to determine the initial response of the human mesenchymal stem cells (MSCs) introduced into this DDM. STUDY DESIGN Disc degeneration model of a bovine disc explant with an end plate was induced by the injection of papain at various concentrations. Labeled MSCs were later introduced in this model. METHODS Phosphate-buffered saline (PBS control) or papain in various concentrations (3, 15, 30, 60, and 150 U/mL) were injected into the bovine caudal IVD explants. Ten days after the injection, GAG content of the discs was evaluated by dimethylmethylene blue assay and cell viability was determined by live/dead staining together with confocal microscopy. Overall matrix composition was evaluated by histology, and water content was visualized by magnetic resonance imaging. Compressive and torsional stiffness of the DDM were also recorded. In the second part, MSCs were labeled with a fluorescence cell membrane tracker and injected into the nucleus of the DDM or a PBS control. Mesenchymal stem cell viability and distribution were evaluated by confocal microscopy. RESULTS A large drop of GAG and water content of the bovine disc were obtained by injecting >30 U/mL papain. Magnetic resonance imaging showed Grade II, III, and IV disc degeneration by injecting 30, 60, and 150 U/mL papain. A cavity in the center of the disc could facilitate later injection of the nucleus pulposus tissue engineering construct while retaining an intact annulus fibrosus. The remaining disc cell viability was not affected. Mesenchymal stem cells injected into the protease-treated DDM disc showed significantly higher cell viability than when injected into the PBS-injected control disc. CONCLUSIONS By varying the concentration of papain for injection, an increasing amount of GAG and water loss could be induced to simulate the different severities of disc degeneration. MSC suspension introduced into the disc has a very low short-term survival. However, it should be clear that this bovine IVD DDM does not reflect a clinical situation but offers exciting possibilities to test novel tissue engineering protocols.

Thermoreversible hyaluronan-based hydrogel supports in vitro and ex vivo disc-like differentiation of human mesenchymal stem cells

BACKGROUND CONTEXT The fate of human mesenchymal stem cells (hMSCs) supplied to the degenerating intervertebral disc (IVD) is still not fully understood and can be negatively affected by low oxygen, pH, and glucose concentration of the IVD environment. The hMSC survival and yield upon injection of compromised IVD could be improved by the use of an appropriate carrier and/or by predifferentiation of hMSCs before injection. PURPOSE To optimize hMSC culture conditions in thermoreversible hyaluronan-based hydrogel, hyaluronan-poly(N-isopropylacrylamide) (HA-pNIPAM), to achieve differentiation toward the disc phenotype in vitro, and evaluate whether preconditioning contributes to a better hMSC response ex vivo. STUDY DESIGN In vitro and ex vivo whole-organ culture of hMSCs. METHODS In vitro cultures of hMSCs were conducted in HA-pNIPAM and alginate for 1 week under hypoxia in chondropermissive medium alone and with the supplementation of transforming growth factor β1 or growth and differentiation factor 5 (GDF-5). Ex vivo, hMSCs were either suspended in HA-pNIPAM and directly supplied to the IVDs or predifferentiated with GDF-5 for 1 week in HA-pNIPAM and then supplied to the IVDs. Cell viability was evaluated by Live-Dead assay, and DNA, glycosaminoglycan (GAG), and gene expression profiles were used to assess hMSC differentiation toward the disc phenotype. RESULTS The HA-pNIPAM induced hMSC differentiation toward the disc phenotype more effectively than alginate: in vitro, higher GAG/DNA ratio and higher collagen type II, SOX9, cytokeratin-19, cluster of differentiation 24, and forkhead box protein F1 expressions were found for hMSCs cultured in HA-pNIPAM compared with those cultured in alginate, regardless of the addition of growth factors. Ex vivo, direct combination of HA-pNIPAM with the disc environment induced a stronger disc-like differentiation of hMSCs than predifferentiation of hMSCs followed by their delivery to the discs. CONCLUSIONS Hyaluronan-based thermoreversible hydrogel supports hMSC differentiation toward the disc phenotype without the need for growth factor supplementation in vitro and ex vivo. Further in vivo studies are required to confirm the suitability of this hydrogel as an effective stem cell carrier for the treatment of IVD degeneration.

The transpedicular approach as an alternative route for intervertebral disc regeneration

STUDY DESIGN Descriptive anatomical study on ovine and human cadaveric lumbar spinal segments. OBJECTIVE To describe the alternative transpedicular approach to deliver therapeutic agents into intervertebral disc (IVD). SUMMARY OF BACKGROUND DATA The present delivery approach of therapeutic agents (growth factors/cells/hydrogels) within the IVD is through injection, via the annulus fibrosus (AF). However, it has recently been demonstrated that small needle puncture of the AF leads to further degeneration and disc herniation. In addition, the injected material has a high chance to be extruded through the AF injury. METHODS Lumbar ovine and human spinal segments were used. Under fluoroscopy, a 2-mm Kirschner wire was introduced in the caudal vertebra through the pedicle and the inferior endplate to the nucleus pulposus. Gross anatomy analysis and high-resolution peripheral quantitative computed tomography (HR-pQCT) were performed to assess the right position of the wire in pedicles. Discography and nucleotomy were performed using a 14G cannula insertion or a 2-mm arthroscopic shaver blade, respectively. Nucleoplasty was also performed with agarose gel/contrast agent and imaged with HR-pQCT. RESULTS Gross anatomy, fluoroscopy, and HR-pQCT images showed that the nucleus pulposus could be approached through the endplate via the pedicle without affecting the spinal canal and the neural foramina. The contrast agent was delivered into the IVD and nucleus pulposus was removed from the disc and filled with agarose gel. CONCLUSION This study describes how a transpedicular approach can be used as an alternative route to deliver therapeutic agents to the disc without disruption of the AF showing the potential use of this technique in preclinical research and highlighting its clinical relevance for IVD regeneration.