Age-related degeneration of lumbar intervertebral discs in rabbits revealed by deuterium oxide-assisted MRI

Immunization against nucleus pulposus antigens to accelerate degenerative disc disease in a rabbit model

Low back pain poses a significant societal burden, with progressive intervertebral disc degeneration (IDD) emerging as a pivotal contributor to chronic pain. Improved animal models of progressive IDD are needed to comprehensively investigate new diagnostic and therapeutic approaches to managing IDD. Recent studies underscore the immune system's involvement in IDD, particularly with regards to the role of immune privileged tissues such as the nucleus pulposus (NP) becoming an immune targeting following initial disc injury. We therefore hypothesized that generating an active immune response against NP antigens with an NP vaccine could significantly accelerate and refine an IDD animal model triggered by mechanical puncture of the disc. To address this question, rabbits were immunized against NP antigens following disc puncture, and the impact on development of progressive IDD was assessed radiographically, functionally, and histologically compared between vaccinated and non-vaccinated animals over a 12-week period. Immune responses to NP antigens were assessed by ELISA and Western blot. We found that the vaccine elicited strong immune responses against NP antigens, including a dominant ~37 kD antigen. Histologic evaluation revealed increases IDD in animals that received the NP vaccine plus disc puncture, compared to disc puncture and vaccine only animals. Imaging evaluation evidenced a decrease in disc height index and higher scores of disc degeneration in animals after disc punctures and in those animals that received the NP vaccine in addition to disc puncture. These findings therefore indicate that it is possible to elicit immune responses against NP antigens in adult animals, and that these immune responses may contribute to accelerated development of IDD in a novel immune-induced and accelerated IDD model.

Analysis of occurrence and risk factors associated with pet rabbits' tumors in Central Thailand

Rabbit oncology is gaining more attention as more pet rabbits are surviving beyond their normal lifespans. Due to the limited epidemiological information on pet rabbits' tumors in Thailand, this study aimed to report the prevalence and the potential risk factors associated with tumors in pet rabbits in Thailand. From 2018 to 2022, 93 tissue biopsies from tumor-suspected lesions on pet rabbits were gathered from animal hospitals in Bangkok and Chonburi provinces, Thailand. According to histopathology confirmation, tumors and tumor-like lesions were diagnosed. In this study, the overall tumors were 67.74% (n=63) out of the submitted cases (n=93). The most commonly affected organ systems were reproduction (65.08%) and integumentary (22.22%). Rabbits older than 5 years were 3.85 times more likely to have reproductive tumors than younger rabbits (95% confidence interval (CI): 1.45-10.27, P≤0.01), and the most frequently occurring tumor type was uterine adenocarcinoma. Furthermore, male rabbits had a 17.02 times higher probability of developing cutaneous tumors than female rabbits (95% CI: 4.19-69.11, P≤0.001), and the most frequently occurring tumor type was soft tissue sarcoma. The results of this study thus suggested that the age and sex of the rabbits were potential risk factors for tumor development in Thailand. The knowledge gained from our study also provided the recommendation for owners to monitor their rabbits' health annually, particularly after late middle age, and rendered guidance for tumor detection in practical clinics.

Preclinical in vivo animal models of intervertebral disc degeneration. Part 1: A systematic review

Intervertebral disc degeneration (IVDD), a widely recognized cause of lower back pain, is the leading cause of disability worldwide. A myriad of preclinical in vivo animal models of IVDD have been described in the literature. There is a need for critical evaluation of these models to better inform researchers and clinicians to optimize study design and ultimately, enhance experimental outcomes. The purpose of this study was to conduct an extensive systematic literature review to report the variability of animal species, IVDD induction method, and experimental timepoints and endpoints used in in vivo IVDD preclinical research. A systematic literature review of peer-reviewed manuscripts featured on PubMed and EMBASE databases was conducted in accordance with PRISMA guidelines. Studies were included if they reported an in vivo animal model of IVDD and included details of the species used, how disc degeneration was induced, and the experimental endpoints used for analysis. Two-hundred and fifty-nine (259) studies were reviewed. The most common species, IVDD induction method and experimental endpoint used was rodents(140/259, 54.05%), surgery (168/259, 64.86%) and histology (217/259, 83.78%), respectively. Experimental timepoint varied greatly between studies, ranging from 1 week (dog and rodent models), to >104 weeks in dog, horse, monkey, rabbit, and sheep models. The two most common timepoints used across all species were 4 weeks (49 manuscripts) and 12 weeks (44 manuscripts). A comprehensive discussion of the species, methods of IVDD induction and experimental endpoints is presented. There was great variability across all categories: animal species, method of IVDD induction, timepoints and experimental endpoints. While no animal model can replicate the human scenario, the most appropriate model should be selected in line with the study objectives to optimize experimental design, outcomes and improve comparisons between studies.

Neoepitope fragments as biomarkers for different phenotypes of intervertebral disc degeneration

Background

During the intervertebral disc (IVD) degeneration process, initial degenerative events occur at the extracellular matrix level, with the appearance of neoepitope peptides formed by the cleavage of aggrecan and collagen. This study aims to elucidate the spatial and temporal alterations of aggrecan and collagen neoepitope level during IVD degeneration.

Methods

Bovine caudal IVDs were cultured under four different conditions to mimic different degenerative situations. Samples cultured after 1- or 8-days were collected for analysis. Human IVD samples were obtained from patients diagnosed with lumbar disc herniation (LDH) or adolescent idiopathic scoliosis (AIS). After immunohistochemical (IHC) staining of Aggrecanase Cleaved C-terminus Aggrecan Neoepitope (NB100), MMP Cleaved C-terminus Aggrecan Neoepitope (MMPCC), Collagen Type 1α1 1/4 fragment (C1α1) and Collagenase Cleaved Type I and II Collagen Neoepitope (C1,2C), staining optical density (OD)/area in extracellular matrix (OECM) and pericellular zone (OPCZ) were analyzed. Conditioned media of the bovine IVD was collected to measure protein level of inflammatory cytokines and C1,2C.

Results

For the bovine IVD sections, the aggrecan MMPCC neoepitope was accumulated in nucleus pulposus (NP) and cartilage endplate (EP) regions following mechanical overload in the one strike model after long-term culture; as for the TNF-α induced degeneration, the OECM and OPCZ of collagen C1,2C neoepitope was significantly increased in the outer AF region after long-term culture; moreover, the C1,2C was only detected in conditioned medium from TNF-α injection + Degenerative loading group after 8 days of culture. LDH patients showed higher MMPCC OECM in NP and higher C1,2C OECM in AF region compared with AIS patients.

Conclusions

In summary, aggrecan and collagen neoepitope profiles showed degeneration induction trigger- and region-specific differences in the IVD organ culture models. Different IVD degeneration types are correlated with specific neoepitope expression profiles. These neoepitopes may be helpful as biomarkers of ECM degradation in early IVD degeneration and indicators of different degeneration phenotypes.

A comparative study to evaluate disc degeneration on magnetic resonance imaging in patients with chronic low back pain and asymptomatic individuals

Objectives

The present study aimed to investigate the association of disc degeneration with low back pain and the effect of ageing on disc degeneration in low back pain versus asymptomatic individuals.

Methodology

A total of 50 patients with chronic low back pain (Group A) were compared to 25 healthy controls (Group B). Both the groups were subjected to magnetic resonance imaging of the lumbar spine and the disc degeneration was measured by the Pfirrmann grading system. The study group (Group A) was further sub-grouped into A1 (lumbar spondylosis, n = 11), A2 (mechanical back pain, n = –13) and A3 (lumbar disc herniation, n = 26).

Results

There was a statistically significant difference in degeneration at the L4-L5 ( p = 0.001) and L5-S1 disc levels ( p = 0.001) between the two groups and contiguous disc involvement was more in low back pain patients. The subgroups of group A showed no statistically significant difference. Age showed a strong positive correlation ( r > 0.5) at all the lumbar levels (except at the L5-S1, r = 0.487) with Pfirrmann grading in Group A ( p = 0.001). There was a weak positive correlation ( r = 0.414) between age and Pfirrmann grade in the controls ( p = 0.04) at the L4-L5 level only.

Conclusions

Significantly higher Pfirrmann grading on magnetic resonance imaging was found at the L4-5 and L5-S1 levels in symptomatic patients suggesting higher involvement of these levels. Progressive disc degeneration is seen with ageing but in patients with low back pain, it is significantly accelerated.

Geriatric Care of Rabbits, Guinea Pigs, and Chinchillas

Specialized veterinary care needed for geriatric rabbits, guinea pigs, and chinchillas is described along with medical conditions common in this age group. Clinical signs of pain, safe analgesics, therapeutics, and alternative modalities are outlined along with guidelines for end-of-life care and decision-making. A handout containing advice for small mammal herbivore clients with geriatric pets is included.

Biological non-ablative repair of lumbar discs by transforaminal intradiscal laser irradiation: MRI quantitative analysis of the effects-preliminary report

Degenerative disc disease is a significant reason for low back pain. Low-level laser irradiation (LLLI) of cartilage results in its reshaping and combines with regenerative reaction. A certain pattern of lumbar disc irradiation induces healing reaction and formation of new cartilage. Quantitative MRI analysis of regenerative response of the cartilage is the subject of this investigation. Fifty-one lumbar discs of 28 patients with discogenic low back pain underwent irradiation with 1.56-μm Er fiber laser (1.2 W). Quantitative MRI analysis is performed in STIR regime within 0.93-14.80 months. Signal intensity is estimated from irradiated discs and control measured from adjacent non-irradiated discs and vertebral bones. T2 WI follow-up is performed within a long period (up to 5 years) in selected cases. The mean value of MRI signal intensity from the irradiated discs increased by 14% (p <<< 0.001). The control bone measurement revealed no difference in signal intensity (p = 0.83). The adjacent non-irradiated discs slightly increased their signal (p < 0.05). T2 WI follow-up within 5 years revealed a steady increase of the signal and the irradiated discs healing. LLLI of degenerated intervertebral discs by 1.56-μm Er fiber laser produces increase of MRI disc signal within the first year after treatment that confirms regenerative response of the disc and could lay in the basis of clinical improvement. Further assessment on the effect is mandatory.

Advanced trends in magnetic resonance imaging in assessment of lumbar intervertebral degenerative disk disease

Abstract

Background

T2 mapping and DWI are newly quantitated method for disk degeneration assessment; they were used in the determination of an early stage of intervertebral disk degeneration. T2 mapping was quantitatively sensitive for detecting the early stage and aging-related changes in intervertebral disk degeneration. Furthermore, T2 mapping and apparent diffusion coefficient values (ADC) in lumbar intervertebral disks indirectly correlated with the Pfirrmann grades in IVDD and age-related disk degeneration. The aim of this study is to evaluate the sensitivity of T2 mapping and apparent diffusion coefficient in the determination of an early stage of intervertebral disk degeneration.

Results

T2 relaxometry values were found to decrease with the increased disk degeneration except in grade V where it was found to be increased again. There was a negative correlation between T2 values and semi-quantitative grading (Pfirrmann Grading) of disk degeneration and T2 values were significantly different when comparing grade I to V. A T2 value of nucleus pulposus (NP) was more sensitive than annulus fibrosus (AF) and entire of the disk. ADC values were found to decrease with the increased degree of disk degeneration; there was a weakly significant negative correlation between age and T2 mapping values, ADC values of nucleus pulposus, and entire of disk.

Conclusion

T2 mapping was significantly different when comparing grade I to V while ADC value had a significant weak negative correlation with age, so T2 mapping and to a little extent ADC can be used for quantitative analysis of early disk generation seeking for early diagnosis and better management.

Matrix metalloproteinase 12 is an indicator of intervertebral disc degeneration co-expressed with fibrotic markers

OBJECTIVE

Recent evidence suggests a role of fibrogenesis in intervertebral disc (IVD) degeneration. We aim to explore if fibrotic genes may serve as IVD degeneration indicators, and if their expression is associated with myofibroblast activity.

DESIGN

Transcriptional expression of fibrosis markers (COL1A1, COL3A1, FN1, HSP47, MMP12, RASAL1) were analyzed in degenerated (D) and non-degenerated (ND) human nucleus pulposus (NP) and annulus fibrosus (AF) cells, along with traditional (SOX9, ACAN) and newly established degeneration markers (CDH2, KRT19, KRT18, FBLN1, MGP, and COMP). Protein expression was investigated by immunohistochemistry in human IVDs, and in rodent IVDs undergoing natural ageing or puncture-induced degeneration. Co-expression with myofibroblast markers was examined by double staining on human and rat specimens. Disc degeneration severity and extent of fibrosis were determined by histological scoring and picrosirius red staining respectively.

RESULTS

Human D-NP showed more intensive staining for picrosirius red than ND-NP. Among the genes examined, D-NP showed significantly higher MMP12 expression along with lower KRT19 expression. Protein expression analysis revealed increased MMP12(+) cells in human D-IVD. Histological scoring indicated mild degeneration in the punctured rat discs and discs of ageing mouse. Higher MMP12 positivity was found in peripheral NP and AF of the degenerative rat discs and in NP of the aged mice. In addition, human D-NP and D-AF showed increased α-SMA(+) cells, indicating enhanced myofibroblast activity. MMP12 was found co-expressed with α-SMA, FSP1 and FAP-α in human and rat degenerative IVDs.

CONCLUSIONS

Our study suggests that in addition to a reduced KRT19 expression, an increased expression of MMP12, a profibrotic mediator, is characteristic of disc degenerative changes. Co-expression study indicates an association of the increased MMP12 positivity with myofibroblast activity in degenerated IVDs. Overall, our findings implicate an impact of MMP12 in disc cell homeostasis. The precise role of MMP12 in IVD degeneration warrants further investigation.

Health survey of 167 pet rabbits (Oryctolagus cuniculus) in Finland

Only a limited amount of information is available about health status of pet rabbits. The aim of this study was to obtain data about the health status of pet rabbits considered healthy by the owners in Finland. Physical examination and lateral abdominal and lateral skull radiography were performed on 167 pet rabbits of which 118 (70.7 per cent) had abnormal findings in at least one examination. The most common findings were acquired dental disease (n=67, 40.1 per cent), vertebral column deformities and degenerative lesions (n=52, 31.1 per cent), skin disorders (n=28, 16.8 per cent) and eye disorders (n=12, 7.2 per cent). Vertebral column angulating deformities were significantly more common in dwarf lop rabbits (P≤0.001). The prevalence of health disorders was significantly higher in rabbits over three years of age of which 51 (82.3 per cent) had findings in at least one examination (P<0.05). Rabbits as prey animals hide their illness, which cause difficulties to owners to recognise health problems. Because of the high prevalence of clinical and radiological findings in apparently healthy pet rabbits, regular physical examinations are advised, especially for animals over three years old.

Delivering mesenchymal stem cells in collagen microsphere carriers to rabbit degenerative disc: reduced risk of osteophyte formation

Mesenchymal stem cells (MSCs) have the potential to treat early intervertebral disc (IVD) degeneration. However, during intradiscal injection, the vast majority of cells leaked out even in the presence of hydrogel carrier. Recent evidence suggests that annulus puncture is associated with cell leakage and contributes to osteophyte formation, an undesirable side effect. This suggests the significance of developing appropriate carriers for intradiscal delivery of MSCs. We previously developed a collagen microencapsulation platform, which entraps MSCs in a solid microsphere consisting of collagen nanofiber meshwork. These solid yet porous microspheres support MSC attachment, survival, proliferation, migration, differentiation, and matrix remodeling. Here we hypothesize that intradiscal injection of MSCs in collagen microspheres will outperform that of MSCs in saline in terms of better functional outcomes and reduced side effects. Specifically, we induced disc degeneration in rabbits and then intradiscally injected autologous MSCs, either packaged within collagen microspheres or directly suspended in saline, into different disc levels. Functional outcomes including hydration index and disc height were monitored regularly until 6 months. Upon sacrifice, the involved discs were harvested for histological, biochemical, and biomechanical evaluations. MSCs in collagen microspheres showed advantage over MSCs in saline in better maintaining the dynamic mechanical behavior but similar performance in hydration and disc height maintenance and matrix composition. More importantly, upon examination of gross appearance, radiograph, and histology of IVD, delivering MSCs in collagen microspheres significantly reduced the risk of osteophyte formation as compared to that in saline. This work demonstrates the significance of using cell carriers during intradiscal injection of MSCs in treating disc degeneration.

Age-related changes in the concentration of elastic fibers in different regions of the rabbit penis

PURPOSE

To investigate whether elastic fiber content in the corpus cavernosum (CC), corpus spongiosum (CS) and tunica albuginea (TA) of the rabbit penis undergoes modifications with age.

METHODS

Rabbits were sacrificed, in groups of ten animals each, at 30, 120, 240, and 730 days of age. Histological sections were obtained from the penile middle shaft and were stained with Weigert's resorsin fuchsin. The content of elastic fibers was determined using stereological methods, and was expressed as volume fraction.

RESULTS

At 730 days of age, elastic fiber content was increased by 54% (p<0.004), 78% (p<0.004), and 87% (p<0.004) in the TA, CC, and CS, respectively, compared with animals aged 30 days. After 30 days of age, the concentration gradually and significantly increased until 240 days of age. In 730-day old animals, the concentration, compared with the previous age group, was unchanged in the CC and decreased by 20% (p<0.004) in the TA.

CONCLUSIONS

Elastic fiber contents in the rabbit penis correlate with properties of penile tissues. Although after one month of age there is a gradual increase in these concentrations, in two-year old animals this trend is interrupted, which suggests that this could be an early alteration due to senescence.

Changes of number of cells expressing proliferation and progenitor cell markers with age in rabbit intervertebral discs

Basic knowledge about the normal regeneration process within the intervertebral disc (IVD) is important to the understanding of the underlying biology. The presence of progenitor and stem cells in IVD has been verified. However, changes of number of progenitor and stem cells with age are still unknown. In this study, changes of cell proliferation and progenitor cell markers with age in IVD cells from rabbits of two different ages were investigated using flow cytometry, immunohistochemistry, real-time polymerase chain reaction, and western blot analysis. Proliferating cell nuclear antigen (PCNA) was chosen as a marker for proliferation, and Notch1, Jagged1, C-KIT, CD166 were chosen as stem/progenitor cell markers. Cell cycle analysis showed that cell number in the G2/M phase of the young rabbits was significantly higher than that of mature rabbits. Immunohistochemical staining demonstrated the expression of PCNA, C-KIT, CD166, Notch1, and Jagged1 in both young and mature annulus fibrosus (AF). Protein expressions of these cell markers in the young rabbits were all significantly higher than those in the mature rabbits. The expression levels of PCNA, CD166, C-KIT, Jagged1 were significantly higher in the AF, and PCNA, C-KIT in the nucleus pulposus from young rabbits than those from the mature rabbits. These findings demonstrated that both proliferation and progenitor cells exist in rabbit IVDs and the number of cells expressing proliferation and progenitor cell markers decreases with age in the rabbit IVD cells. Methods that are designed to maintain the endogenous progenitor cells and stimulate their proliferation could be successful in preventing or inhibiting degenerative disc disease.

Apparent diffusion coefficient in normal and abnormal pattern of intervertebral lumbar discs: initial experience

The aim of the present study was to compare the relationship of morphologically defined non-bulging/herniated, bulging and herniated intervertebral lumbar discs with quantitative apparent diffusion coefficient (ADC). Thirty-two healthy volunteers and 28 patients with back pain or sciatica were examined by MRI. All intervertebral lumbar discs from L1 to S1 were classified according to morphological abnormality and degenerated grades. The ADC values of nucleus pulposus (NP) were measured and recorded. The significant differences about mean ADC values of NP were found between non-bulging/herniated discs and bulging discs as well as herniated discs (P < 0.05), whereas there were no significant differences in ADC values between bulging and herniated discs (P > 0.05). Moreover, statistically significant relationship was found in the mean ADC values of NP between "non-bulging/herniated and non-degenerated discs" and "non-bulging/herniated degenerated discs" as well as herniated discs (P < 0.05). Linear regression analysis between ADC value and disc level revealed an inverse correlation (r = -0.18). The ADC map of the NP is a potentially useful tool for the quantitative assessment of componential and molecular alterations accompanied with lumbar disc abnormalities.

Effects of nucleus pulposus cell-derived acellular matrix on the differentiation of mesenchymal stem cells

Recent attempts to treat disc degeneration with mesenchymal stem cells (MSCs) showed encouraging results. Differentiating MSCs towards nucleus pulposus cell (NPC)-like lineages represents a speculative mechanism. Niche factors including hypoxia, growth factors and cell-cell interactions have been suggested but the matrix niche factor has not been studied. Our collagen microencapsulation provides a 3D model to study matrix niche as it enables the encapsulated cells to remodel the template matrix. We previously demonstrated the chondro-inductive role of of chondrocytes-derived matrix in MSCs and showed that NPCs maintained their phenotype and remodeled the template matrix of collagen microspheres into a glycosaminoglycan (GAG)-rich one. Here we aim to study the effects of NPC-derived matrix on MSC differentiation towards NPC-like lineages by firstly producing an NPC-derived matrix in collagen microspheres, secondly optimizing a decellularization protocol to discard NPCs yet retaining the matrix, thirdly repopulating the acellular NPC-derived matrix with MSCs and fourthly evaluating their phenotype. Finally, we injected these microspheres in a pilot rabbit disc degeneration model. Results showed that NPCs survived, maintained their phenotypic markers and produced GAGs. A decellularization protocol with maximal removal of the NPCs, minimal loss in major matrix components and partial retention of NPC-specific markers was identified. The resulting acellular matrix supported MSC survival and matrix production, and up-regulated the gene expression of NPC markers including type II collagen and glypican 3. Finally, injection of MSC in these microspheres in rabbit degenerative disc better maintained hydration level with more pronounced staining of GAGs and type II collagen than controls.

Effect of ulinastatin on the expression of iNOS, MMP-2, and MMP-3 in degenerated nucleus pulposus cells of rabbits

We examined the effects of ulinastatin on the expression of inducible nitric oxide synthase (iNOS), matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-3 (MMP-3) in degenerated nucleus pulposus (NP) cells of rabbits induced by interleukin (IL)-1β in vitro. An in vitro NP cell culture model was set up with enzyme digestion. NP cells from adult white rabbits were divided into six groups: the normal control group, the ulinastatin control group (320 U/mL ulinastatin), the induced group (10 ng/mL IL-1β), and three inhibition groups (IL-1β followed by 160, 320, or 640 U/mL ulinastatin). After a 2-day culture, the NP cells were collected for immunohistochemical staining for MMP-2 and MMP-3 and spectrophotometric analysis of the amount of iNOS. Immunohistochemical staining showed that the expression of MMP-2 and MMP-3 proteins in NP cells decreased in the inhibition groups compared with the induced group, which was in inverse proportion to the ulinastatin concentration. Spectrophotometric results showed that, compared with the induced group, the iNOS content in each inhibition group decreased, most significantly in the 320 U/mL group. Ulinastatin effectively inhibited the increased expression of MMP-2, MMP-3, and iNOS in degenerated NP cells induced by IL-1β in vitro. It suggests that ulinastatin may potentially be useful for clinical therapy of intervertebral disc degeneration.

Age-related expression of MCP-1 and MMP-3 in mouse intervertebral disc in relation to TWEAK and TNF-α stimulation

This study was undertaken to investigate the age-related differences of monocyte chemotactic protein-1 (MCP-1) and matrix metalloproteinase-3 (MMP-3) expression in mouse intervertebral disc (IVD) and to determine whether MMP-3 plays a role in disc degeneration. Expression of MCP-1 and MMP-3 mRNA in mouse IVD was assessed by quantitative PCR. The ability of MCP-1 and MMP-3 expression in IVD to respond to TNF-α or TWEAK stimulation was examined by quantitative PCR, WB, ELISA, and immunohistochemistry. IVD derived from MMP-3-deficient and wild-type mice were compared using Safranin-O staining and immunohistochemistry. mRNA levels of MCP-1 and MMP-3 in IVD significantly diminished and the ability of MCP-1 or MMP-3 expression to respond to TNF-α or TWEAK stimulation was significantly reduced as age increased. IVD derived from 64-week-old wild-type mice showed clearly diffuse proteoglycan loss by Safranin-O staining and immunohistochemistry compared with younger mice. However, no loss of proteoglycan and typeII collagen were observed in IVD derived from 64-week-old MMP-3-deficient mice. MCP-1 and MMP-3 expression in mouse IVD showed age-related decreases. The response to inflammation in IVD also displayed age-related changes. Therefore, disc degeneration may vary with the patients' age and targeting MMP-3 may be a possible future therapeutic strategy for disc degeneration.

Growth factors and anticatabolic substances for prevention and management of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is frequent, appearing from the second decade of life and progressing with age. Conservative management often fails, and patients with IVD degeneration may need surgical intervention. Several treatment strategies have been proposed, although only surgical discectomy and arthrodesis have been proved to be predictably effective. Biological strategies aim to prevent and manage IVD degeneration, improving the function and anabolic and reparative capabilities of the nucleus pulposus and annulus fibrosus cells and inhibiting matrix degradation. At present, clinical applications are still in their infancy. Further studies are required to clarify the role of growth factors and anticatabolic substances for prevention and management of intervertebral disc degeneration.

Abundance of calpain and aggrecan-cleavage products of calpain in degenerated human intervertebral discs

OBJECTIVE

To assess the expression of calpains and calpain-induced aggrecan fragmentation in early and advanced stages of degeneration of human intervertebral discs (IVDs).

DESIGN

Disc tissue samples of 55 patients (mean age, 51.2 ± 22.3 years) who underwent intervertebral fusion were divided into groups with early and advanced degeneration based on the Thompson magnetic resonance imaging (MRI) scale. In advanced degeneration group, five patients (mean age, 35.5 ± 11.4 years) of lumbar disc herniation (LDH) were included. Protein levels of m- and μ-calpains and their inhibitor calpastatin were assayed, and immunohistochemical techniques were used to localize and quantify the production of the enzymes. To investigate calpain activity, we assayed purified aggrecan fragmentation in disc tissue by Western blotting and immunohistochemistry with VPGVA antibody, which recognizes the m-calpain generated neo-epitope GVA.

RESULTS

Discs at early stages of degeneration expressed low levels of m- and μ-calpains and calpastatin, and few cells expressed degenerative enzymes. At more advanced stages of degeneration, the expression and number of cells immunopositive for m-calpain, μ-calpain and calpastatin were significantly higher. Further finding showed that anti-GVA-reactive aggrecan fragments were significantly higher in discs at advanced compared with early stages of degeneration. Herniated disc samples showed stronger expression and more cells immunopositive for calpains, calpastatin and GVA in the nucleus pulposus than in the annulus fibrous.

CONCLUSIONS

The expression of calpains, together with m-calpain-induced degradation products of extracellular matrix, was correlated with the degree of disc degeneration in human IVD tissue. These findings suggest that calpains may be involved in IVD degeneration via proteoglycan (PG) cleavage.

Visualizing ocular lens fluid dynamics using MRI: manipulation of steady state water content and water fluxes

Studies using various MRI techniques have shown that a water-protein concentration gradient exists in the ocular lens. Because this concentration is higher in the core relative to the lens periphery, a gradient in refractive index is established in the lens. To investigate how the water-protein concentration profile is maintained, bovine lenses were incubated in different solutions, and changes in water-protein concentration ratio monitored using proton density weighted (PD-weighted) imaging in the absence and presence of heavy water (D2O). Lenses incubated in artificial aqueous humor (AAH) maintained the steady state water-protein concentration gradient, but incubating lenses in high extracellular potassium (KCl-AAH) or low temperature (Low T-AAH) caused a collapse of the gradient due to a rise in water content in the core of the lens. To visualize water fluxes, lenses were incubated in D2O, which acts as a contrast agent. Incubation in KCl-AAH and low T-AAH dramatically slowed the movement of D2O into the core but did not affect the movement of D2O into the outer cortex. D2O seemed to preferentially enter the lens cortex at the anterior and posterior poles before moving circumferentially toward the equatorial regions. This directionality of D2O influx into the lens cortex was abolished by incubating lenses in high KCl-AAH or low T-AAH, and resulted in homogenous influx of D2O into the outer cortex. Taken together, our results show that the water-protein concentration ratio is actively maintained in the core of the lens and that water fluxes preferentially enter the lens at the poles.

MR imaging assessment of lumbar intervertebral disk degeneration and age-related changes: apparent diffusion coefficient versus T2 quantitation

BACKGROUND AND PURPOSE

T2 and ADC mappings are 2 quantitative MR imaging tools for assessing IVDD. This study aimed to compare these 2 measures in detecting IVDD and its age-related changes.

MATERIALS AND METHODS

Thirty-seven asymptomatic volunteers and 28 patients with back pain or sciatica were examined, and their lumbar disk T2 and ADC maps were quantified via sagittal imaging protocols at 1.5T. For all participants, the Pfirrmann system was used by 2 radiologists for grading disks. T2 and ADC values in the inner portion of disks were measured, and their variances in different grades were analyzed by 1-way ANOVA testing. The ability of T2 and ADC measures to differentiate IVDD grades was compared on the basis of their ROC curves. For asymptomatic subjects, the correlations between age and the 2 MR imaging measures were assessed by the Pearson correlation test.

RESULTS

Both T2 and ADC values were found to decrease with the increasing Pfirrmann grades except T2 in grade V. Significant T2 differences were seen among grades I-IV, but not between grades IV and V. There were no significant ADC differences among grades I-III. Moreover, the areas under the ROC curves differed significantly (0.95 and 0.67 for T2 and ADC, respectively). Linear regression analysis revealed that T2 yielded more significant correlation with age (r = -0.77) than ADC did (r = -0.37).

CONCLUSIONS

T2 quantitation provides a more sensitive and robust approach for detecting and characterizing the early stage of IVDD and age-related disk changes.

Aquaporin-1: a potential membrane channel for facilitating the adaptability of rabbit nucleus pulposus cells to an extracellular matrix environment

BACKGROUND

During the process of degenerative aging of the intervertebral disc (IVD), the extracellular matrix (ECM) environment changes, with osmolarity and oxygen (O(2)) concentration important components of such changes. The IVD cells respond to maintain the homeostasis and function of the IVD by several mechanisms. Aquaporin-1 (AQP-1) is a transmembrane channel protein that is permeable to water and O(2), which prevents rapid volume deformation under osmotic stress and facilitates O(2) diffusion across the plasma membrane. One hypothesis is that AQP-1 has potential roles in aging degeneration of IVDs.

METHODS

In this study, AQP-1 expression levels were investigated in aging rabbit nucleus pulposus (NP) cells using immunohistochemistry and Western blotting in vivo, and different osmolarities and O(2) concentrations in vitro by quantitative real-time PCR.

RESULTS

The results showed that AQP-1 was expressed at different levels in aging rabbit's NPs and AQP-1 was regulated by the NP cells in different ECM environmental conditions. AQP-1 was downregulated under hypo-osmotic stress to prevent rapid swelling deformation and was upregulated under hypoxic stress to facilitate O(2) utilization.

CONCLUSION

It is suggested that AQP-1 may reflect the status of aged IVDs and have a potential role in reflecting the adaptability of NP cells under different adverse ECM environments in aging degenerated IVDs.

Identification of cell proliferation zones, progenitor cells and a potential stem cell niche in the intervertebral disc region: a study in four species

STUDY DESIGN

Descriptive experimental study in 4 different mammals.

OBJECTIVE

To investigate cell proliferation/regeneration and localize stem cells/progenitor cells within the intervertebral disc (IVD).

SUMMARY OF BACKGROUND DATA

Disc degeneration (DD) is believed to play a major role in patients with chronic lumbar pain. Lately, biologic treatment options for DD have gained increasing interest. Normal regeneration processes within the IVD and have previously been sparsely described and therefore it is of great interest to increase the knowledge about these processes. Methods. Detection of cell proliferations zones and label-retaining cells were done by in vivo 5-bromo-2-deoxyuridine (BrdU) labeling in 18 rabbits, killed after 4, 6, 10, 14, 28, or 56 days. Results were visualized with immunohistochemistry and fluorescence/confocal microscopy. Localization of progenitor cell were further investigated by immunohistochemistry using antibodies towards Notch1, Delta4, Jagged1, C-KIT, KI67, and Stro-1 in normal IVD from rabbits (n = 3), rats (n = 2), minipigs (n = 2), and in human degenerated IVD (n = 4). Further, flowcytometry analysis using progenitor markers were performed on additional human IVD cells (n = 3).

RESULTS

BrdU positive cells were found in comparable numbers at early and late time points in most regions of the anulus fibrosus (AF) and nucleus pulposus demonstrating slow ongoing cell proliferation. In the AF border to ligament zone (AFo) and the perichondrium region (P) a stem cell niche-like pattern was determined (a high number of BrdU positive cells at early time points vs. only a few label retaining cells at later time points). In normal and DD tissue from the 4 investigated species progenitor cell markers were detected. Conclusion. The IVD is a tissue with ongoing slow cell proliferation both in the AF and the nucleus pulposus. The stem cell niche pattern detected in AFo and P can be suggested to play a role for IVD morphology and function. These findings may be of importance for the development of biologic treatment strategies.