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. 2023 Dec;18(1):2212481.
doi: 10.1080/19932820.2023.2212481.

Original animal model of lumbar disc degeneration

Najah Elmounedi  1 , Walid Bahloul  1   2 , Mourad Aoui  1   2 , Nizar Sahnoun  1   2 , Zoubaier Ellouz  1   2 , Hassib Keskes  1   2
Affiliations

Original animal model of lumbar disc degeneration

Najah Elmounedi et al. Libyan J Med. 2023 Dec.

Abstract

Purpose: Disc degeneration (DD) is a common cause of low back pain, which represents one of the most widespread public health problems in the world. Therefore, the establishment of a reproducible animal model is indispensable to understand the pathogenic mechanisms of DD and to test new therapeutic strategies. From this perspective, the fundamental objective of this study was to elucidate the effect of ovariectomy in establishing a new animal model of DD in rats.

Methods: 36 female Sprague-Dawley rats were divided into four groups of 9 rats: Group 1: Negative control (Sham): Only an abdominal skin incision and sutures were performed. Group 2: Ovariectomy (OVX): Removal of two ovaries through a transverse incision in the middle of the abdomen. Group 3: Puncture (Punct): Puncture of lumbar intervertebral discs (L3/4, L4/5, and L5/6) by a 21 G needle. Group 4: Puncture+ovariectomy (Punct+OVX): Removal of two ovaries and puncture of L3/4, L4/5, and L5/6 discs. The rats were euthanized 1, 3, and 6 weeks post-surgery, and the discs were harvested. Validity was assessed by radiography, histology, and biochemistry (water content).

Results: Disc height, water content, and histologic score decreased significantly in the last 3 groups and at all three-time points (P < 0.05). DD progressed over time in the Punct and Punct+OVX groups (P < 0.05). The changes were more severe in the Punct+OVX group compared to the Punct group and the OVX group.

Conclusion: The combination of puncture and ovariectomy induced rapid and progressive DD in the lumbar discs of rats without spontaneous recovery.

Keywords: Disc degeneration; animal model; intervertebral disc; ovariectomy; puncture.

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Conflict of interest statement

Each author certifies that he or she, or a member of his or her immediate family, has no commercial association (i.e. consultancies, stock ownership, equity interest, patent/licensing arrangement, etc.) that might pose a conflict of interest in connection with the submitted manuscript.

Figures

Figure 1.
Figure 1.
Establishment of the animal model of lumbar DD (Ovariectomy + disc punction) via the transabdominal approach. The shaved region (a) and skin incision (b). Induction of ovariectomy by ablation of the ovaries (c). Exposure of the lumbar disc L4/5 and induction of DD by inserting the needle vertically (d). Identification of the two other lumbar discs (e). Closure of the abdominal cavity (f).
Figure 2.
Figure 2.
Gross sample of a disc. A complete rat lumbar region (a). Transverse horizontal sections and microscopic (Hematoxylin and eosin (HE)) appearance of the intact disc (b,c) and the disc of the Punct+OVX group 6 weeks post punction depicting the extent of the well-defined experimental anterolateral lesion (star) (d, e).
Figure 3.
Figure 3.
Body weight changes of rats in the four groups. the body weight increases significantly over time in ovariectomized (OVX) rats compared to the Sham group. Data are expressed as mean ± SD. *p < 0.05, **p < 0.01 vs Sham group.
Figure 4.
Figure 4.
a) Radiographic assessment of the lumbar-discs (L3/4, L4/5, and L5/6) of the four groups at week 6. b) schematic representation of measurement of disc height index (DHI). The DHI is expressed as the disc height index (DHI) based on the method of Masuda et al (9). c) Changes in disc height index (DHI). The %DHI of the Punct and Punct+OVX groups differed significantly from that of the Sham group at weeks 3 and 6. The decrease in the %DHI of the Punct+OVX group was more severe than that of the Punct group at weeks 3 and 6 (P < 0.01).
Figure 5.
Figure 5.
(a) Gross anatomical change observations. Macroscopic observations revealed a decrease in disc height and disappearance of NP structure in groups OVX, Punct, and, Punct+OVX at 6 weeks. Disc height was maintained in the four groups at the first week, and the NP structure was similar to that of the Sham group. (b) Thompson grading score at different groups and time points. *p < 0.05, **p < 0.01 comparing OVX, Punct or, Punct+OVX groups to Sham group.
Figure 6.
Figure 6.
Hematoxylin/Eosin staining of Midsagittal section of a coccygean disc in the four groups at 1, 3, and 6 weeks (scale bar equates 500 µm).
Figure 7.
Figure 7.
Changes in the HE scores of the four groups at 1, 3, and 6 weeks. Compared to the Sham, significantly higher histologic scores were recorded for the Punct+OVX group at weeks 1, 3, and, 6 (all P < 0.01), for the Punct group at week 3 and 6(P < 0.01) and for the group OVX at week 3 (P < 0.05) and 6 (P < 0.01). There were significant differences between Punct and Punct+OVX groups, between Punct and OVX groups and between OVX and Punct+OVX groups. *p < 0.05, **p < 0.01.
Figure 8.
Figure 8.
Collagen I (blue fibers) analysis by Masson’s trichrome staining in the AF only of the four groups at weeks 1, 3, and 6 (scale bar equates 50 µm).
Figure 9.
Figure 9.
Changes in disc water content (H2O%) in the four groups at 1, 3 and 6 weeks. The disc water content of the Punct and Punct+OVX groups decreased significantly at weeks 3 (P < 0.01, P < 0.01) and 6 (P < 0.01, P < 0.01). The Punct+OVX group had a significantly lower disc water content he Punct group at weeks 3 (P < 0.01) and 6 (P < 0.05). The Punct+OVX group had a significantly lower disc water content than the OVX group at week 6 (P < 0.01).
None
Abbreviations: AF, annulus fibrosus; NP, nucleus pulposus.
None
Abbreviations: AF, annulus fibrosus; NP, nucleus pulposus.
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