Nose to back: compatibility of nasal chondrocytes with environmental conditions mimicking a degenerated intervertebral disc

Abstract

Nasal chondrocytes (NCs) have gained increased recognition for cartilage tissue regeneration. To assess NCs as a source for cell therapy treatment of intervertebral disc (IVD) degeneration, tissue-forming properties of NCs under physiological conditions mimicking the degenerated IVD were compared to those of mesenchymal stromal cells (MSCs) and articular chondrocytes (ACs), two cell sources presently used in clinical trials. Cells were cultured in a combination of low glucose, hypoxia, acidity and inflammation for 28 d. Depending on the conditions, cells were either cultured in the absence of instructive growth factors or underwent chondrogenic instructional priming by addition of transforming growth factor β1 (TGFβ1) for the first 7 d. Histology, immunohistochemistry, biochemistry, enzyme-linked immunosorbent assay (ELISA) and quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) analyses demonstrated limited cell maintenance and accumulation of cartilaginous extracellular matrix for MSCs in IVD conditions. ACs maintained a steady accumulation of glycosaminoglycans (GAGs) throughout all non-acidic conditions, with and without priming, but could not synthesise type II collagen (Col2). NCs accumulated both GAGs and Col2 in all non-acidic conditions, independent of priming, whereas MSCs strongly diminished their GAG and Col2 accumulation in an inflamed environment. Supplementation with inflammatory cytokines or an acidic environment affected NCs to a lower extent than ACs or MSCs. The data, overall indicating that in an inflamed IVD environment NCs were superior to ACs and MSCs, encourage further assessment of NCs for treatment of degenerative disc disease.

Cell sources proposed for nucleus pulposus regeneration

“…180,181 As chondrocytes also exhibit favorable properties for cartilage repair, there are systematic reviews that have collated information on the culture and expansion capability of chondrocytes; highlighting that chondrogenic phenotype can be maintained using low glucose and hypoxic conditions. 182 63,176 In vivo chondrocytes demonstrated the potential for long-term survival of transplanted cells; transplanted autologous auricular chondrocytes were shown to survive for at least 6 months in a rabbit model, 178 and porcine articular cartilage remained viable at 12 months post injection into a porcine model. 184 ‡ ‡ ‡ ‡ Throughout the studies using chondrocytes for cell therapy for IVD regeneration, the cells were shown to be tolerant to the IVD environment, most probably due to its similarities to the condition of cartilage the chondrocytes are derived, and remain viable post-transplantation in small animal models.…”

“…176 However, when acidic and inflammatory cytokines were introduced to represent a degenerative IVD environment, neither articular chondrocytes nor nasal chondrocytes deposited GAGs. 63 In vivo transplantation of auricular and articular chondrocytes within the degenerative NP resulted in the production of proteoglycans for up to 12 months in a porcine model 184 and tissue formation which resembled hyaline-like cartilage was apparent in a rabbit model. 178 Despite the chondrocytes' ability to express extracellular matrix components, it was duly noted that the values were not in the same range of magnitude as native tissue, with native healthy NP tissue having a unique biochemical composition with a GAG to collagen ratio of 27:1.…”

HOX Gene Expressions in Cultured Articular and Nasal Equine Chondrocytes

“…Despite the high degree of evolutionary conservation of HOX genes [ 22 ], HOX D8 of nasal chondrocytes exhibited species-specific expression in humans and goats [ 19 ]. Furthermore, NCs produce a functional cartilagous matrix [ 23 ] and seem to be more robust than MSCs and ACs with respect to the effect of inflammatory factors [ 24 ].…”

Involvement of the G-Protein-Coupled Receptor 4 in the Increased Expression of RANK/RANKL/OPG System and Neurotrophins by Nucleus Pulposus Cells under the Degenerated Intervertebral Disc-Like Acidic Microenvironment

“…In a previous study, acid-sensing ion channels (ASICs), a sort of voltageinsensitive Na + channels, were reported to play critical roles in physiological and pathological conditions of the disc [18,19]. And acidic microenvironment has been reported to be associated with the local inflammation [20] and upregulation of neurotrophins [21], which leads to the progression of IVD degeneration. However, the underlying molecular mechanism is not fully understood.…”