Modulation of the In Vivo Inflammatory Response by Pro- Versus Anti-Inflammatory Intervertebral Disc Treatments.

Carla Cunha,Mário A Barbosa,Cláudia Ribeiro-Machado,Maria Molinos,Graciosa Q Teixeira,Joana R Ferreira,Catarina L Pereira,Susana G Santos,Raquel M Goncalves

doi:10.3390/ijms21051730

Abstract

Inflammation is central in intervertebral disc (IVD) degeneration/regeneration mechanisms, and its balance is crucial to maintain tissue homeostasis. This work investigates the modulation of local and systemic inflammatory response associated with IVD degeneration/herniation by administration of PRO- versus ANTI-inflammatory treatments. Chitosan/poly-γ-glutamic acid nanocomplexes, known as pro-inflammatory (PRO), and soluble diclofenac, a non-steroidal anti-inflammatory drug (ANTI), were intradiscally administered in a rat IVD injury model, 24 h after lesion. Two weeks after administration, a reduction of disc height accompanied by hernia formation was observed. In the PRO-inflammatory treated group, IL-1β, IL-6 and COX-2 IVD gene expression were upregulated, and loss of nucleus pulposus (NP) structure and composition was observed. Systemically, lower T-cell frequency was observed in the lymph nodes (LN) and spleen (SP) of the PRO group, together with an increase in CD4+ T cells subset in the blood (BL) and LN. In contrast, the ANTI-group had higher proteoglycans/collagen ratio and collagen type 2 content in the NP, while an increase in the frequency of myeloid cells, M1 macrophages and activated macrophages (MHCII+) was observed at the systemic level. Overall, this study illustrates the dynamics of local and systemic inflammatory and immune cell responses associated with intradiscal therapies, which will contribute to designing more successful immunomodulatory treatments for IVD degeneration.

Highlights

Inflammation is often related with intervertebral disc (IVD) degeneration, since a wide number of inflammatory mediators, including prostaglandins (PG), interleukins (IL-1, -6, -8) and tumor necrosis factor (TNF)-α have been described in IVD catabolic processes [1]
The first effects of the intradiscal pro-/anti-inflammatory treatments were evaluated by disc height index (DHI) (Figure 2A)
Ch is known as non-biodegradable, being able to drive the inflammatory response from pro- to anti-inflammatory with time, as we have previously described when culturing monocytes in Ch ultra-thin films, with an increase in TNF-α and IL-1β secretion after 3 days, that switch to an increase in IL-10 and transforming growth factor (TGF)-β upon 10 days [48]

Summary

Introduction

Inflammation is often related with intervertebral disc (IVD) degeneration, since a wide number of inflammatory mediators, including prostaglandins (PG), interleukins (IL-1, -6, -8) and tumor necrosis factor (TNF)-α have been described in IVD catabolic processes [1]. Our group has previously established and validated an IVD herniation/degeneration model of rat caudal needle puncture, using a 21 G needle [10,11], in which IVD herniation and infiltration of macrophages were observed [10]. This model is relatively simple to manipulate and presents cost-effectiveness [12]. It allows the study of local and systemic immune response, crucial in human IVD degeneration and difficult to analyze in vitro or ex vivo [13]. It is important to consider the limitations of small animal models of IVD degeneration when compared to humans, such as differences in spine biomechanics, IVD size and cellular composition, which may be critical for clinical translation [5]

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Discussion

Conclusion