Demographic factors that influence human disc cell proliferation in vitro

Regenerative and immunogenic characteristics of cultured nucleus pulposus cells from human cervical intervertebral discs

Cell-based regenerative approaches have been suggested as primary or adjuvant procedures for the treatment of degenerated intervertebral disc (IVD) diseases. Our aim was to evaluate the regenerative and immunogenic properties of mildly and severely degenerated cervical nucleus pulposus (NP) cells with regard to cell isolation, proliferation and differentiation, as well as to cell surface markers and co-cultures with autologous or allogeneic peripheral blood mononuclear cells (PBMC) including changes in their immunogenic properties after 3-dimensional (3D)-culture. Tissue from the NP compartment of 10 patients with mild or severe grades of IVD degeneration was collected. Cells were isolated, expanded with and without basic fibroblast growth factor and cultured in 3D fibrin/poly (lactic-co-glycolic) acid transplants for 21 days. Real-time reverse-transcription polymerase chain reaction (RT-PCR) showed the expression of characteristic NP markers ACAN, COL1A1 and COL2A1 in 2D- and 3D-culture with degeneration- and culture-dependent differences. In a 5,6-carboxyfluorescein diacetate N-succinimidyl ester-based proliferation assay, NP cells in monolayer, regardless of their grade of degeneration, did not provoke a significant proliferation response in T cells, natural killer (NK) cells or B cells, not only with donor PBMC, but also with allogeneic PBMC. In conjunction with low inflammatory cytokine expression, analyzed by Cytometric Bead Array and fluorescence-activated cell sorting (FACS), a low immunogenicity can be assumed, facilitating possible therapeutic approaches. In 3D-culture, however, we found elevated immune cell proliferation levels, and there was a general trend to higher responses for NP cells from severely degenerated IVD tissue. This emphasizes the importance of considering the specific immunological alterations when including biomaterials in a therapeutic concept. The overall expression of Fas receptor, found on cultured NP cells, could have disadvantageous implications on their potential therapeutic applications because they could be the targets of cytotoxic T-cell activity acting by Fas ligand-induced apoptosis.

Stemming the Degeneration: IVD Stem Cells and Stem Cell Regenerative Therapy for Degenerative Disc Disease

The intervertebral disc (IVD) is immensely important for the integrity of vertebral column function. The highly specialized IVD functions to confer flexibility and tensile strength to the spine and endures various types of biomechanical force. Degenerative disc disease (DDD) is a prevalent musculoskeletal disorder and is the major cause of low back pain and includes the more severe degenerative lumbar scoliosis, disc herniation and spinal stenosis. DDD is a multifactorial disorder whereby an imbalance of anabolic and catabolic factors, or alterations to cellular composition, or biophysical stimuli and genetic background can all play a role in its genesis. However, our comprehension of IVD formation and theetiology of disc degeneration (DD) are far from being complete, hampering efforts to formulate appropriate therapies to tackle DD. Knowledge of the stem cells and various techniques to manipulate and direct them to particular fates have been promising in adopting a stem-cell based regenerative approach to DD. Moreover, new evidence on the residence of stem/progenitor cells within particular IVD niches has emerged holding promise for future therapeutic applications. Existing issues pertaining to current therapeutic approaches are also covered in this review.

The effects of age, sex, ethnicity, and spinal level on the rate of intervertebral disc degeneration: a review of 1712 intervertebral discs

STUDY DESIGN

A gross anatomic and magnetic resonance imaging study of intervertebral disc (IVD) degeneration in fresh cadaveric lumbar spines.

OBJECTIVE

The purpose of this study was to find the rate of IVD degeneration.

SUMMARY OF BACKGROUND DATA

Age, sex, race, and lumbar level are among some of the factors that play a role in IVD degeneration. The rate at which IVDs degenerate is unknown.

METHODS

Complete lumbar spine segments (T11/T12 to S1) were received within 24 hours of death. The nucleus pulposus, anulus fibrosus, cartilaginous and bony endplate, and the peripheral vertebral body were assessed with magnetic resonance imaging and IVD degeneration was graded by two observers from grade 1 (nondegenerated) to grade 5 (severely degenerated) on the basis of a scale developed by Tanaka et al. The specimens were then sectioned and gross anatomic evaluation was performed according to Thompson et al. RESULTS.: A total of 433 donors and 1712 IVDs were analyzed. There were 366 whites, 47 Africans, 16 Hispanics, 4 Asian. There were 306 male and 127 female donors. The age range was 14 to 81 years, (average: 60.5 ± 11.3). For donors greater than age 40, the L5/S1 IVD degenerated at a significantly faster rate of 0.043 per year compared to 0.031, 0.034, 0.033, 0.027 for L1/L2, L2/L3, L3/L4, L4/L5, respectively. For donors younger than 40, L5/S1 IVD degenerated at a significantly faster rate of 0.141/y compared to 0.033, 0.021, 0.031, 0.050 for L1/L2, L2/L3, L3/L4, L4/L5, respectively. Multiple regression analysis revealed that sex had no significant effect on IVD degeneration whereas African ethnicity was associated with lower Thompson score at L1/L2, L2/L3, L3/L4, L4/L5 when compared with whites.

CONCLUSION

The relatively early degeneration at L5-S1 in all races and lower Thompson grade in donors of African ethnicity needs further investigation. Factors such as sagittal alignment, facet joint arthritis, and genetics potentially play a role in IVD degeneration.

Annulus cells from more degenerated human discs show modified gene expression in 3D culture compared with expression in cells from healthier discs

BACKGROUND CONTEXT

Understanding gene expression patterns of disc cells in culture is important as we develop biologic therapies for disc degeneration. The objective of the present study was to determine if cells from more degenerated discs expressed different genes, or differed in their expression patterns, compared with patterns of cells from healthier discs.

PURPOSE

To determine if annulus cells from more degenerated discs expressed different gene expression patterns compared with patterns of cells from healthier discs using genome-wide analysis.

STUDY DESIGN

Cells from human annulus tissue were grown in three-dimensional (3D) culture and their gene expression patterns analyzed with Affymetrix microarray analysis. Gene expression patterns of cells from more degenerated discs (Thompson Grades IV and V) were compared with patterns from cells from healthier discs (Thompson Grades I, II, and III).

METHODS

After approval by our human subjects institutional review board, annulus cells were obtained from lumbar discs of seven subjects with Thompson Grades I, II, or III and from five subjects with discs of Thompson Grades IV and V. Cells were grown in 3D culture for 2 weeks; 3D cultures were used because this microenvironment more closely mimics the in vivo condition. mRNA was harvested, processed for Affymetrix genome-wide gene analysis, and data analyzed with p values adjusted so as to compensate for false discovery rates.

RESULTS

GeneSifter analyses showed that cells from more degenerated discs had 320 genes significantly upregulated, and 104 genes significantly downregulated compared with cells from healthier discs. Important genes included those related to: 1) the extracellular matrix (ECM) (keratin-associated protein 1-1, hyaluronan synthase 2, and nexin were upregulated; biglycan, collagen type VI alpha 2, thrombospondin 3, laminen alpha 1, fibronectin type III domain-containing protein 1, elastin microfibril interfacer 2, fibulin 2, and nidogen 1 and 2 were downregulated); 2) ECM proteolysis (ADAMTS6 was upregulated); 3) cell proliferation (never in mitosis gene 1-related kinase 3, cell division cycle 2-like 5 [cholinesterase-related cell division controller], RAB42 [member of RAS oncogene family], and cyclin-dependent kinase 6 were upregulated; RAS-like GTP-binding 1 was downregulated); 4) apoptosis (BCL2-like 11 and p53-inducible nuclear protein 1 were upregulated; caspase recruitment domain family, member 10, caspase-1 dominant-negative inhibitor pseudo-ICE, and caspase 9 and FADD-like apoptosis regulator were downregulated); and 5) growth factors, inflammatory mediators, and other genes (fibroblast growth factor 1, pregnancy-associated plasma protein-A, interleukin 1 alpha, and interleukin 7 were upregulated; TGF-beta-induced transcript 1, interleukin 26 and interleukin 1 receptor-like 1, tumor necrosis factor, alpha-induced protein 2, and chemokine (C-X3-C motif) ligand 1 were downregulated).

CONCLUSIONS

Data presented here show that annulus cells from more degenerated discs show modified gene expression in 3D culture. Important gene variations involved expression of interleukins, cytokines, ECM components, and apoptosis regulators. Results presented here have potential application in future cell-based biologic therapies for disc degeneration.

Does the sagittal alignment of the cervical spine have an impact on disk degeneration? Minimum 10-year follow-up of asymptomatic volunteers

There have been few studies that investigated and clarified the relationships between progression of degenerative changes and sagittal alignment of the cervical spine. The objective of the study was to longitudinally evaluate the relationships among progression of degenerative changes of the cervical spine with age, the development of clinical symptoms and sagittal alignment of the cervical spine in healthy subjects. Out of 497 symptom-free volunteers who underwent MRI and plain radiography of the cervical spine between 1994 and 1996, 113 subjects (45 males and 68 females) who responded to our contacts were enrolled. All subjects underwent another MRI at an average of 11.3 years after the initial study. Their mean age at the time of the initial imaging was 36.6 +/- 14.5 years (11-65 years). The items evaluated on MRI were (1) decrease in signal intensity of the intervertebral disks, (2) posterior disk protrusion, and (3) disk space narrowing. Each item was evaluated using a numerical grading system. The subjects were divided into four groups according to the age and sagittal alignment of the cervical spine, i.e., subjects under or over the age of 40 years, and subjects with the lordosis or non-lordosis type of sagittal alignment of the cervical spine. During the 10-year period, progression of decrease in signal intensity of the disk, posterior disk protrusion, and disk space narrowing were recognized in 64.6, 65.5, and 28.3% of the subjects, respectively. Progression of posterior disk protrusion was significantly more frequent in subjects over 40 years of age with non-lordosis type of sagittal alignment. Logistic regression analysis revealed that stiff shoulder was closely correlated with females (P = 0.001), and that numbness of the upper extremity was closely correlated with age (P = 0.030) and male (P = 0.038). However, no significant correlation between the sagittal alignment of the cervical spine and clinical symptoms was detected. Sagittal alignment of the cervical spine had some impact on the progression of degenerative changes of the cervical spine with aging; however, it had no correlation with the occurrence of future clinical symptoms.

The cell biology of intervertebral disc aging and degeneration

Intervertebral disc degeneration, which mimics disc aging but occurs at an accelerated rate, is considered to be related to neck or low back pain and disc herniation. Degenerated discs show breakdown of the extracellular matrix and thus fail to bear the daily loadings exerted on the spine. Rather than a passive process of wear and tear, disc degeneration is an aberrant, cell-mediated response to progressive structural failure due to aging and other environmental factors such as abnormal mechanical stress. With aging and degeneration, disc cells undergo substantially biologic changes, including alternation of cell type in the nucleus pulposus, increased cell density but decreased number of viable cells as a result of increased cell death and increased cell proliferation, increased cell senescence, and altered cell phenotype which is characterized by compromised capability of synthesizing correct matrix components and by enhanced catabolic metabolism. These changes are involved in the process of disc degeneration through the complicated interactions among them. To retard or reverse disc degeneration, the abnormal conditions of the decreased viable cell population and the altered cell phenotype should be corrected. As potential therapies for disc degeneration, intradiscal protein injection, gene transfer and cell implantation are being understudied in vivo. Suppression of excessive apoptosis and accelerated senescence of disc cells may be other choices for treating disc degeneration. When performing a biologic therapy in order to repair or regenerate the degenerated disc, nutrient and biomechanical factors should also be incorporated, because they are the major causes of the biologic changes experienced by disc cells. Moreover, a very early intervention is indicated by the finding that the onset of human disc degeneration occurs as early as by adolescence.

Do We Need Biomarkers for Disc Degeneration?

Disc degeneration plays a major role in this country's medical, social and economic structure. The life-time prevalence of low back pain, which has disc degeneration as its cause, is about 80% in the general population. It is a primary cause of disability and estimated costs related to low back disorders exceed $100 billion per year in the U.S. alone. Biomarkers are becoming increasingly important as indicators of the presence of disease, and in evaluating outcomes during clinical treatment. Cell-based biologic therapies which are currently being developed to treat disc degeneration are going to be most efficacious when applied to the early stages of disc disease. In this article we ask: 1) Whether there are existing biomarkers which could play a role in detecting early stages of disc degeneration, and 2) Highlight exciting potentials in future biomarker screening for disc degeneration.