Intervertebral disc cell death in the porcine and human injured cervical spine after trauma: a histological and ultrastructural study

The Relationship Between Physical Activity and Mental Health Among Individuals With Spinal Cord Injury: Protocol for a Scoping Review

BACKGROUND

Spinal cord injury (SCI) is a devastating condition that often leads to significant impairments in physical function, leading to disability and mental health disorders. Hence, understanding the prevalence of SCI and the relationship between physical activity and mental health in individuals with SCI is crucial for informing rehabilitation strategies and optimizing outcomes.

OBJECTIVE

This study aims to comprehensively analyze existing research on the link between physical activity and mental health and identify the level of physical activity and mental health status, the barriers to physical activity, and SCI's impacts on psychological well-being in individuals with SCI.

METHODS

An electronic search strategy will be used to identify prevalence studies published since 1993 in health-related databases such as PubMed, MEDLINE, COCHRANE Library, and Wiley Library using the following query: "Spinal Cord Injury" OR "Paraplegia" OR "Tetraplegia" AND "Physical Activity" OR "Exercise" AND "Mental Health" OR "Mental Illness" OR "Mental Disorder." Bibliographies of primary studies and review articles meeting the inclusion criteria will be searched manually to identify further eligible studies. The risk of bias in the included studies will be appraised using the Joanna Briggs Institute checklist for prevalence studies by 2 review authors. Any disagreement will be resolved by reaching a consensus.

RESULTS

Funding was received in October 2023, data collection will commence in July 2024, and the results are expected by 2025. We will summarize the selection of the eligible studies using a flowchart. The data from the studies will be extracted and tabulated. This scoping review will be published in a peer-reviewed journal in accordance with PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) guidelines.

CONCLUSIONS

This scoping review underscores the complex relationship between physical activity and mental health among individuals with SCI, highlighting the level of physical activity and mental health status, barriers to physical activity engagement, and psychological implications. Understanding these dynamics is crucial in devising tailored interventions aimed at enhancing mental well-being. This synthesis of evidence emphasizes the need for personalized strategies to promote physical activity, addressing unique challenges faced by this population to foster improved mental health outcomes and overall quality of life.

TRIAL REGISTRATION

Open Science Framework osf.io/ugx7d; https://osf.io/ugx7d/.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/56081.

Repetitive strikes loading organ culture model to investigate the biological and biomechanical responses of the intervertebral disc

Background

Disc degeneration is associated with repetitive violent injuries. This study aims to explore the impact of repetitive strikes loading on the biology and biomechanics of intervertebral discs (IVDs) using an organ culture model.

Methods

IVDs from the bovine tail were isolated and cultured in a bioreactor, with exposure to various loading conditions. The control group was subjected to physiological loading, while the model group was exposed to either one strike loading (compression at 38% of IVD height) or repetitive one strike loading (compression at 38% of IVD height). Disc height and dynamic compressive stiffness were measured after overnight swelling and loading. Furthermore, histological morphology, cell viability, and gene expression were analyzed on Day 32. Glycosaminoglycan (GAG) and nitric oxide (NO) release in conditioned medium were also analyzed.

Results

The repetitive one strike group exhibited early disc degeneration, characterized by decreased dynamic compression stiffness, the presence of annulus fibrosus clefts, and degradation of the extracellular matrix. Additionally, this group demonstrated significantly higher levels of cell death (p < 0.05) and glycosaminoglycan (GAG) release (p < 0.05) compared to the control group. Furthermore, upregulation of MMP1, MMP13, and ADAMTS5 was observed in both nucleus pulposus (NP) and annulus fibrosus (AF) tissues of the repetitive one strike group (p < 0.05). The one strike group exhibited annulus fibrosus clefts but showed no gene expression changes compared to the control group.

Conclusions

This study shows that repetitive violent injuries lead to the degeneration of a healthy bovine IVDs, thereby providing new insights into early-stage disc degeneration.

Neonatal Enthesis Healing Involves Noninflammatory Acellular Scar Formation through Extracellular Matrix Secretion by Resident Cells

Wound healing typically recruits the immune and vascular systems to restore tissue structure and function. However, injuries to the enthesis, a hypocellular and avascular tissue, often result in fibrotic scar formation and loss of mechanical properties, severely affecting musculoskeletal function and life quality. This raises questions about the healing capabilities of the enthesis. Herein, this study established an injury model to the Achilles entheses of neonatal mice to study the effectiveness of early-age enthesis healing. Histology and immunohistochemistry analyses revealed an atypical process that did not involve inflammation or angiogenesis. Instead, healing was mediated by secretion of collagen types I and II by resident cells, which formed a permanent hypocellular and avascular scar. Transmission electron microscopy showed that the cellular response to injury, including endoplasmic reticulum stress, autophagy, and cell death, varied between the tendon and cartilage ends of the enthesis. Single-molecule in situ hybridization, immunostaining, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assays verified these differences. Finally, gait analysis showed that these processes effectively restored function of the injured leg. These findings reveal a novel healing mechanism in neonatal entheses, whereby local extracellular matrix secretion by resident cells forms an acellular extracellular matrix deposit without inflammation, allowing gait restoration. These insights into the healing mechanism of a complex transitional tissue may lead to new therapeutic strategies for adult enthesis injuries.

Intervertebral disc cell chondroptosis elicits neutrophil response in Staphylococcus aureus spondylodiscitis

To understand the pathophysiology of spondylodiscitis due to Staphylococcus aureus, an emerging infectious disease of the intervertebral disc (IVD) and vertebral body with a high complication rate, we combined clinical insights and experimental approaches. Clinical data and histological material of nine patients suffering from S. aureus spondylodiscitis were retrospectively collected at a single center. To mirror the clinical findings experimentally, we developed a novel porcine ex vivo model mimicking acute S. aureus spondylodiscitis and assessed the interaction between S. aureus and IVD cells within their native environment. In addition, the inflammatory features underlying this interaction were assessed in primary human IVD cells. Finally, mirroring the clinical findings, we assessed primary human neutrophils for their ability to respond to secreted inflammatory modulators of IVD cells upon the S. aureus challenge. Acute S. aureus spondylodiscitis in patients was characterized by tissue necrosis and neutrophil infiltration. Additionally, the presence of empty IVD cells’ lacunae was observed. This was mirrored in the ex vivo porcine model, where S. aureus induced extensive IVD cell death, leading to empty lacunae. Concomitant engagement of the apoptotic and pyroptotic cell death pathways was observed in primary human IVD cells, resulting in cytokine release. Among the released cytokines, functionally intact neutrophil-priming as well as broad pro- and anti-inflammatory cytokines which are known for their involvement in IVD degeneration were found. In patients as well as ex vivo in a novel porcine model, S. aureus IVD infection caused IVD cell death, resulting in empty lacunae, which was accompanied by the release of inflammatory markers and recruitment of neutrophils. These findings offer valuable insights into the important role of inflammatory IVD cell death during spondylodiscitis and potential future therapeutic approaches.

Fate of the intervertebral disc and analysis of its risk factors following high-energy traumatic thoracic and lumbar fractures: MRI results of minimum five years after injury

OBJECTIVE

Disc degenerative disease is regarded as the primary cause of low back pain. The purpose of this study was to clarify the fate of Intervertebral disc (IVD) following the traumatic event through long-term follow-up and to identify the risk factors for irrevocable degeneration.

METHODS

78 non-operative patients who had traumatic fracture of the thoracic or lumbar at minimum 5 years before were enrolled. Disc degeneration was assessed by modified Pfirrmann grading system. The Acceleration of disc degeneration (ADD) was defined as the difference of grade between IVD adjacent to fractured vertebra and their neighbors with increasing grade from 0 to 7. A novel classification of Endplate injury (EPI) with increasing severity from type I to III was proposed based on the injured morphology. The long-term fate of IVD adjacent to fractured vertebra and risk factors for ADD were analyzed.

RESULTS

The mean time of last follow-up was 15.4 ± 10.8 years (range 5-49 years) after injury. 138 (68.66%) IVDs were graded 0 of ADD, 44 (21.89%) were 1-3 and 19 (9.45%) were 4-7. Multivariate binary logistic regression analyses showed that injured posterior ligamentous complex (PLC) and EPI type III were independent risk factors for ADD.

CONCLUSIONS

Injured PLC and EPI type III were independent risk factors for ADD in patients with traumatic thoracic or lumbar fracture. For such patients without risk factors for ADD, the non-intervertebral fusion should be given a priority if surgery is necessary.

Chondrocyte death involvement in osteoarthritis

Chondrocyte apoptosis is known to contribute to articular cartilage damage in osteoarthritis and is correlated to a number of cartilage disorders. Micromass cultures represent a convenient means for studying chondrocyte biology, and, in particular, their death. In this review, we focused the different kinds of chondrocyte death through a comparison between data reported in the literature. Chondrocytes show necrotic features and, occasionally, also apoptotic features, but usually undergo a new form of cell death called Chondroptosis, which occurs in a non-classical manner. Chondroptosis has some features in common with classical apoptosis, such as cell shrinkage, chromatin condensation, and involvement, not always, of caspases. The most crucial peculiarity of chondroptosis relates to the ultimate elimination of cellular remnants. Independent of phagocytosis, chondroptosis may serve to eliminate cells without inflammation in situations in which phagocytosis would be difficult. This particular death mechanism is probably due to the unusual condition chondrocytes both in vivo and in micromass culture. This review highlights on the morpho-fuctional alterations of articular cartilage and focus attention on various types of chondrocyte death involved in this degeneration. The death features have been detailed and discussed through in vitro studies based on tridimensional chondrocyte culture (micromasses culture). The study of this particular mechanism of cartilage death and the characterization of different biological and biochemical underlying mechanisms can lead to the identification of new potentially therapeutic targets in various joint diseases.

Traumatic vertebra and endplate fractures promote adjacent disc degeneration: evidence from a clinical MR follow-up study

OBJECTIVES

The integrity of endplate is important for maintaining the health of adjacent disc and trabeculae. Yet, pathological impacts of traumatic vertebra and endplate fractures were less studied using clinical approaches. This study aims to investigate their effects on the development of adjacent disc degeneration, segmental kyphosis, Modic changes (MCs), and high-intensity zones (HIZs).

MATERIALS AND METHODS

Magnetic resonance (MR) images of patients with acute traumatic vertebral compression fractures (T11-L5) were studied. On MR images, endplate fractures were evaluated as present or absent. Disc signal, height, bulging area, sagittal Cobb angle, MCs, and HIZs were measured on baseline and follow-up MR images to study the changes of the disc in relation to vertebra fractures and endplate fractures.

RESULTS

Ninety-seven patients were followed up for 15.4 ± 14.0 months. There were 123 fractured vertebrae, including 79 (64.2%) with endplate fractures and 44 (35.8%) without. Both the adjacent and control discs decreased in signal and height over time (p < 0.001), and the disc adjacent to vertebral fractures had greater signal and height loss than the control disc (p < 0.05). In the presence of endplate fractures, the adjacent discs had greater signal decrease in follow-up (p < 0.05), as compared to those without endplate fractures. Sagittal Cobb angle significantly increased in segments with endplate fractures (p < 0.05). Vertebra fractures were associated with new occurrence of MCs in the fractured vertebra (p < 0.001) but not HIZs in the adjacent disc.

CONCLUSIONS

Traumatic vertebral fractures were associated with accelerated adjacent disc degeneration, which appears to be further promoted by concomitant endplate fractures. Endplate fractures were associated with progression of segmental kyphosis.

Programmed NP Cell Death Induced by Mitochondrial ROS in a One-Strike Loading Disc Degeneration Organ Culture Model

Increasing evidence has indicated that mitochondrial reactive oxygen species (ROS) play critical roles in mechanical stress-induced lumbar degenerative disc disease (DDD). However, the detailed underlying pathological mechanism needs further investigation. In this study, we utilized a one-strike loading disc degeneration organ culture model to explore the responses of intervertebral discs (IVDs) to mechanical stress. IVDs were subjected to a strain of 40% of the disc height for one second and then cultured under physiological loading. Mitoquinone mesylate (MitoQ) or other inhibitors were injected into the IVDs. IVDs subjected to only physiological loading culture were used as controls. Mitochondrial membrane potential was significantly depressed immediately after mechanical stress (P < 0.01). The percentage of ROS-positive cells significantly increased in the first 12 hours after mechanical stress and then declined to a low level by 48 hours. Pretreatment with MitoQ or rotenone significantly decreased the proportion of ROS-positive cells (P < 0.01). Nucleus pulposus (NP) cell viability was sharply reduced at 12 hours after mechanical stress and reached a stable status by 48 hours. While the levels of necroptosis- and apoptosis-related markers were significantly increased at 12 hours after mechanical stress, no significant changes were observed at day 7. Pretreatment with MitoQ increased NP cell viability and alleviated the marker changes by 12 hours after mechanical stress. Elevated mitochondrial ROS levels were also related to extracellular matrix (ECM) degeneration signs, including catabolic marker upregulation, anabolic marker downregulation, increased glycosaminoglycan (GAG) loss, IVD dynamic compressive stiffness reduction, and morphological degradation changes at the early time points after mechanical stress. Pretreatment with MitoQ alleviated some of these degenerative changes by 12 hours after mechanical stress. These changes were eliminated by day 7. Taken together, our findings demonstrate that mitochondrial ROS act as important regulators of programmed NP cell death and ECM degeneration in IVDs at early time points after mechanical stress.

One strike loading organ culture model to investigate the post-traumatic disc degenerative condition

Background

Acute trauma on intervertebral discs (IVDs) is thought to be one of the risk factors for IVD degeneration. The pathophysiology of IVD degeneration induced by single high impact mechanical injury is not very well understood. The aim of this study was using a post-traumatic IVD model in a whole organ culture system to analyze the biological and biomechanical consequences of the single high-impact loading event on the cultured IVDs.

Methods

Isolated healthy bovine IVDs were loaded with a physiological loading protocol in the control group or with injurious loading (compression at 50% of IVD height) in the one strike loading (OSL) group. After another 1 day (short term) or 8 days (long term) of whole organ culture within a bioreactor, the samples were collected to analyze the cell viability, histological morphology and gene expression. The conditioned medium was collected daily to analyze the release of glycosaminoglycan (GAG) and nitric oxide (NO).

Results

The OSL IVD injury group showed signs of early degeneration including reduction of dynamic compressive stiffness, annulus fibrosus (AF) fissures and extracellular matrix degradation. Compared to the control group, the OSL model group showed more severe cell death (P ​< ​0.01) and higher GAG release in the culture medium (P ​< ​0.05). The MMP and ADAMTS families were up-regulated in both nucleus pulposus (NP) and AF tissues from the OSL model group (P ​< ​0.05). The OSL injury model induced a traumatic degenerative cascade in the whole organ cultured IVD.

Conclusions

The present study shows a single hyperphysiological mechanical compression applied to healthy bovine IVDs caused significant drop of cell viability, altered the mRNA expression in the IVD, and increased ECM degradation. The OSL IVD model could provide new insights into the mechanism of mechanical injury induced early IVD degeneration.

The translational potential of this article

This model has a high potential for investigation of the degeneration mechanism in post-traumatic IVD disease, identification of novel biomarkers and therapeutic targets, as well as screening of treatment therapies.

An ultrastructural study of chondroptosis: programmed cell death in degenerative intervertebral discs in vivo

Apoptosis has been regarded to mediate intervertebral disc degeneration (IDD); however, the basic question of how the apoptotic bodies are cleared in the avascular intervertebral disc without phagocytes, which are essential to apoptosis, remains to be elucidated. Our goals were to investigate the ultrastructure of nucleus pulposus (NP) cells undergoing chondroptosis, a variant of apoptotic cell death, in a rabbit annular needle-puncture model of IDD. Experimental IDD was induced by puncturing discs with a 16-G needle in New Zealand rabbits. At 4 and 12 weeks after puncture, progressive degeneration was demonstrated by X-ray, magnetic resonance imaging and histological staining. TUNEL staining suggested a significant increase in the apoptosis index in the degenerated NP. However, the percentage of apoptotic cells with the classic ultrastructure morphology was much less than that with chondroptotic ultrastructure morphology under transmission electron microscopy (TEM). The chondroptotic cells from the early to late stage were visualized under TEM. In addition, the percentage of chondroptotic cells was significantly enhanced in the degenerated NP. Furthermore, 'paralyzed' cells were found in the herniated tissue. Western blotting revealed an increase in caspase3 expression in the degenerated NP. The expression of the Golgi protein (58K) was increased by the fourth week after puncture but decreased later. These findings indicate that chondroptosis is a major type of programmed cell death in the degenerated rabbit NP that may be related to the progressive development of IDD.

Insights on Molecular Mechanisms of Chondrocytes Death in Osteoarthritis

Osteoarthritis (OA) is a joint pathology characterized by progressive cartilage degradation. Medical care is mainly based on alleviating pain symptoms. Compelling studies report the presence of empty lacunae and hypocellularity in cartilage with aging and OA progression, suggesting that chondrocyte cell death occurs and participates to OA development. However, the relative contribution of apoptosis per se in OA pathogenesis appears complex to evaluate. Indeed, depending on technical approaches, OA stages, cartilage layers, animal models, as well as in vivo or in vitro experiments, the percentage of apoptosis and cell death types can vary. Apoptosis, chondroptosis, necrosis, and autophagic cell death are described in this review. The question of cell death causality in OA progression is also addressed, as well as the molecular pathways leading to cell death in response to the following inducers: Fas, Interleukin-1β (IL-1β), Tumor Necrosis factor-α (TNF-α), leptin, nitric oxide (NO) donors, and mechanical stresses. Furthermore, the protective role of autophagy in chondrocytes is highlighted, as well as its decline during OA progression, enhancing chondrocyte cell death; the transition being mainly controlled by HIF-1α/HIF-2α imbalance. Finally, we have considered whether interfering in chondrocyte apoptosis or promoting autophagy could constitute therapeutic strategies to impede OA progression.

Temporal Analyses of the Response of Intervertebral Disc Cells and Mesenchymal Stem Cells to Nutrient Deprivation

Much emphasis has been placed recently on the repair of degenerate discs using implanted cells, such as disc cells or bone marrow derived mesenchymal stem cells (MSCs). This study examines the temporal response of bovine and human nucleus pulposus (NP) cells and MSCs cultured in monolayer following exposure to altered levels of glucose (0, 3.15, and 4.5 g/L) and foetal bovine serum (0, 10, and 20%) using an automated time-lapse imaging system. NP cells were also exposed to the cell death inducers, hydrogen peroxide and staurosporine, in comparison to serum starvation. We have demonstrated that human NP cells show an initial “shock” response to reduced nutrition (glucose). However, as time progresses, NP cells supplemented with serum recover with minimal evidence of cell death. Human NP cells show no evidence of proliferation in response to nutrient supplementation, whereas MSCs showed greater response to increased nutrition. When specifically inducing NP cell death with hydrogen peroxide and staurosporine, as expected, the cell number declined. These results support the concept that implanted NP cells or MSCs may be capable of survival in the nutrient-poor environment of the degenerate human disc, which has important clinical implications for the development of IVD cell therapies.

Morphological changes in the human cervical intervertebral disc post trauma: response to fracture-type and degeneration grade over time

PURPOSE

In the first 24 h post-intervertebral disc (IVD) trauma, up to 75 % cell death has been reported. In addition, burst fractures cause post-traumatic disc degeneration by elevated pro-apoptotic and pro-inflammatory gene transcription. Moreover, some patients have pre-trauma degenerative disc disease. The aim of the study was to assess histological changes and cell-death over a time period of up to 1 year caused by mechanical and structural factors.

METHODS

116 anterior portions of IVDs of the cervical spine were studied histologically by light microscopy and ultrastructurally by transmission electron microscopy (TEM). The group was investigated with regard to three main parameters: fracture mechanism (compressive vs. tensile/shear loads), degeneration grade (low vs. high) and endplate fracture (with vs. without). Disc architecture (e.g. ruptures) was studied histologically. Cell morphology was examined ultrastructurally to quantify cell-death, healthy and balloon cells. According to ultrastructural observations, two time-groups (up to 6 days vs. later) were established. Statistical analyses were carried out within and between time-groups.

RESULTS

Histological changes were obvious in the annulus fibrosus where ruptures with haematoma were replaced by granulation tissue. Significant differences in cell-death were seen in the first few days due to different loads. In contrast to the more degenerated segments, low degenerated ones revealed significantly less cell death with time post-trauma. Interestingly, no difference was found between groups after the sixth day. Cell-death (mean 44 % for all investigated groups) remained high after day 6 post-trauma.

CONCLUSION

IVDs retrieved from low grade degenerated segments revealed a significant recovery, with less cell-death and a partially restored disc matrix, although cell-death remained high. Long-term clinical studies of stabilized segments arising from different fracture mechanisms are required.

Chondroptosis in alkaptonuric cartilage

Alkaptonuria (AKU) is a rare genetic disease that affects the entire joint. Current standard of treatment is palliative and little is known about AKU physiopathology. Chondroptosis, a peculiar type of cell death in cartilage, has been so far reported to occur in osteoarthritis, a rheumatic disease that shares some features with AKU. In the present work, we wanted to assess if chondroptosis might also occur in AKU. Electron microscopy was used to detect the morphological changes of chondrocytes in damaged cartilage distinguishing apoptosis from its variant termed chondroptosis. We adopted histological observation together with Scanning Electron Microscopy and Transmission Electron Microscopy to evaluate morphological cell changes in AKU chondrocytes. Lipid peroxidation in AKU cartilage was detected by fluorescence microscopy. Using the above-mentioned techniques, we performed a morphological analysis and assessed that AKU chondrocytes undergo phenotypic changes and lipid oxidation, resulting in a progressive loss of articular cartilage structure and function, showing typical features of chondroptosis. To the best of our knowledge, AKU is the second chronic pathology, following osteoarthritis, where chondroptosis has been documented. Our results indicate that Golgi complex plays an important role in the apoptotic process of AKU chondrocytes and suggest a contribution of chondroptosis in AKU pathogenesis. These findings also confirm a similarity between osteoarthritis and AKU.

Morphological similarities after compression trauma of bovine and human intervertebral discs: Do disc cells have a chance of surviving?

To study the behavior of bovine disc cells and changes in disc matrix following in vitro compression tests; to compare the findings to investigations on human intervertebral discs (IVD) after burst fracture of the cervical spine. Healthy IVDs (n = 21) from three bovine tails were studied at 6 and 12 h post-mortem, with 16 IVDs subjected to impact loading and five as unloaded controls. IVDs (n = 8) from patients with burst fractures were compared to the bovine compression group. Specimens were studied macroscopically, histologically, and ultrastructurally for healthy cells, balloon cells, and disc cell death (DCD). Annulus ruptures were seen in both post-trauma groups, with radial ruptures being present histologically in all loaded bovine discs. Balloon cells were found in some human IVDs and were induced in vitro in bovine loaded discs within a distinct range of absorbed energy. There was a positive correlation between DCD and absorbed energy in all compartments of bovine discs. Both species showed similar patterns of DCD in the different compartments. This study was able to show similarities between both species in cell morphologies and matrix damage. The survival of the disc after substantial compression trauma thus seems to remain highly questionable.

Viability, growth kinetics and stem cell markers of single and clustered cells in human intervertebral discs: implications for regenerative therapies

PURPOSE

There is much interest in the development of a cellular therapy for the repair or regeneration of degenerate intervertebral discs (IVDs) utilising autologous cells, with some trials already underway. Clusters of cells are commonly found in degenerate IVDs and are formed via cell proliferation, possibly as a repair response. We investigated whether these clusters may be more suitable as a source of cells for biological repair than the single cells in the IVD.

METHODS

Discs were obtained at surgery from 95 patients and used to assess the cell viability, growth kinetics and stem or progenitor cell markers in both the single and clustered cell populations.

RESULTS

Sixty-nine percent (±15) of cells in disc tissue were viable. The clustered cell population consistently proliferated more slowly in monolayer than single cells, although this difference was only significant at P0-1 and P3-4. Both populations exhibited progenitor or notochordal cell markers [chondroitin sulphate epitopes (3B3(-), 7D4, 4C3 and 6C3), Notch-1, cytokeratin 8 and 19] via immunohistochemical examination; stem cell markers assessed with flow cytometry (CD73, 90 and 105 positivity) were similar to those seen on bone marrow-derived mesenchymal stem cells.

CONCLUSIONS

These results confirm those of previous studies indicating that progenitor or stem cells reside in adult human intervertebral discs. However, although the cell clusters have arisen via proliferation, there appear to be no greater incidence of these progenitor cells within clusters compared to single cells. Rather, since they proliferate more slowly in vitro than the single cell population, it may be beneficial to avoid the use of clustered cells when sourcing autologous cells for regenerative therapies.

Morphological differences in adolescent idiopathic scoliosis: a histological and ultrastructural investigation

STUDY DESIGN

Histological and ultrastructural evaluation of cell morphologies at the concave and convex side of apical intervertebral discs (IVD) of adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To determine changes in cell morphology, viability, and cell death after asymmetric disc loading in AIS and to compare the findings with the tilt angles.

SUMMARY OF BACKGROUND DATA

The reaction of cells to loading stimuli in the IVD seems to be specific. Although dynamic loads are more beneficial to the disc cells and maintain the matrix biosynthesis, static compressive loads suppress gene expression.

METHODS

Apical IVDs (Th8-Th9 to L1-L2) from 10 patients with AIS were studied histologically (including TUNEL [TdT-mediated dUTP-biotin nick end labeling] staining to identify disc cell death by apoptosis) and ultrastructurally for matrix evaluations and to quantify healthy, balloon, chondroptotic, apoptotic, and necrotic cells on the concave and convex sides. Patients' spines were classified according to the Lenke classification. Degeneration was assessed according to the Pfirrmann grading system. Two groups were established; group 1 (G1) with a tilt of 5° to 9° and group 2 (G2) with a tilt of 10° to 19°.

RESULTS

Balloon cells were found in significantly higher numbers at the concave side (G1-annulus fibrosus [AF]: mean 16%), with almost none found at the convex side. Mean numbers of healthy cells did not show differences comparing both sides. Significantly higher numbers of healthy cells were found with increasing tilt angle at the concave side. Necrosis (mean, 47%) increased toward the center of the disc but did not differ between the sides of the IVDs. The fibrils found in the outer AF on the convex side were 30% thinner.

CONCLUSION

This study was able to show significant differences in cell morphologies in the AF on both sides and in correlation to the different tilt angles. The type and magnitude of load seem to influence disc cells. Further studies are required to provide more information on disc and cell changes in scoliosis.

Morphological changes in disc herniation in the lower cervical spine: an ultrastructural study

INTRODUCTION

The basis of disc degeneration is still unknown, but is believed to be a cell-mediated process. Apoptosis might play a major role in degenerative disc disease (DDD). The aim of this study was to correlate the viability of disc cells with the radiological degeneration grades (rDG) in disc herniation.

MATERIALS AND METHODS

Forty anterior IVD's (C4-C7) from 39 patients with DDD were studied histologically and ultrastructurally to quantify healthy, "balloon", chondroptotic, apoptotic and necrotic cells. Patients were classified to their rDG, as having either prolapse (P: DGII + III) and/or osteochondrosis (O: DGIV + V). Similar studies were undertaken on eight control discs.

RESULTS

Cell death by necrosis (mean 35%) was common but differed not significantly in both groups. All patients with a disc prolapse DGII + III revealed balloon cells (iAF: mean 32%). All appeared alive and sometimes were hypertrophic. However, significantly less balloon cells were found in the O-Group. Control samples revealed no evidence of "balloon" cells in DGII and only a minor rate in DGIII.

CONCLUSION

According to the different rDG, quantitative changes were obvious in healthy and "balloon" cells, but not for cell death. At the moment it can only be hypothesized if "balloon" cells are part of a repair strategy and/or cause of disc herniation.

Degenerative disc disease of herniated intervertebral discs is associated with extracellular matrix remodeling, vimentin-positive cells and cell death

We studied patients with degenerative disc disease (DDD) to demonstrate that i) remodeling of the extracellular matrix (ECM) in the intervertebral disc (IVD), particularly the elastic fiber system, of subjects with herniated discs is dysregulated and that ii) it is accompanied by accelerated elastin degradation due to increased expression of matrix metalloprotease-9 (MMP-9). Moreover we wanted to obtain a deeper insight into the pathogenesis of DDD through the study of ECM calcification, DNA fragmentation using TUNEL analysis, BAX, bcl-2 and vimentin immunopositive cells. We studied herniated discs from patients of three age groups (group 1=30-40 years; group 2=40-50 years; and group 3=50-65 years) to evaluate the oxytalan fiber systemMMP-9, apoptosis and vimentin immunopositive cells. The results demonstrated the presence of oxytalan fibers in the annulus fibrosus (AF) and the nucleus pulposus (NP) of herniated discs. In the AF oxytalan fibers replaced disrupted mature elastic fibers in calcified areas, while in the NP they were mostly found in nests at the periphery of chondrocytes. MMP-9 was prevalently observed in NP nests above all in group 1 and group 3 discs while group 2 exhibited a lower MMP-9 immunostaining. Activation of the apoptotic process was demonstrated by upregulated BAX expression in group 3. BAX immunopositivity was inversely mirrored by a significant decrease in bcl-2 expression. Intermediate filament protein vimentin was strongly expressed only in group 1 samples. A large number of apoptotic TUNEL+ cells was observed in group 3 specimens. The presence of oxytalan fibers may be the result of a process of incomplete elastogenesis, or a response to mechanical stress trying to functionally replace the lack of elastic fibers. MMP-9 expression seems to relate to disc damage, while chondrocyte BAX upregulation and TUNEL+ cell staining revealed apoptosis activation regardless of patient age. Vimentin immunopositivity was clearly detected in group 1 annulus fibrosus and nucleus pulposus cells. In conclusion, as demonstrated by the vimentin-positive cells, the injured IVD has endogenous resources that can stem the DDD damage, including substitution of damaged elastic fibers by oxytalan fibers. In addition, induction of apoptosis suggests an increased cell turnover in response to repair needs.