Table 3.
An overview of the in vivo studies for individual small molecules
| Molecule | |
|---|---|
| Naringin | |
| Study | Zhang et al. 2018 63 |
| Aim | To assess the potential therapeutic effect of Naringin on IVD regeneration |
| Animal/Patient-model | Sprague-Dawley Rat (G: NI, n=36), puncture-induced rat IDD model |
| Intervention | Intraperitoneal injection of Naringin (80mg/kg/day) |
| Analysis | Histopathology and MRI at 4 and 12 weeks after surgery |
| Results/Conclusion |
Histology: protection of CEP, no significant difference between saline (vehicle) and Naringin treated groups regarding the damage to NP cells after 12 weeks; MRI: There is a significant difference between (vehicle) and Naringin treated groups in terms of Pfirrmann MRI grade scores. Conclusion: Naringin may exert a protective effect on IVD after an initial injury. |
| Cannabidiol (CBD) | |
| Study | Silveria et al. 2014 127 |
| Aim | To assess the protective effect of CBD on lesion-induced IDD |
| Animal/Patient-model | Wistar Rat (G: male, n=19), puncture-induced rat IDD model |
| Intervention | Intradiscal injection of CBD (60-80-120nm) |
| Analysis | Histopathology (15 days after surgery), MRI (2 and 15 days after surgery) |
| Results/Conclusion |
Histology: CBD (120 nmol) prevented the typical histological changes in the AF, no significant protective effect seen on NP. MRI: Injection of CBD (120 nmol) immediately after lesion significantly improved MRI pixel intensity. Conclusion: Considering that CBD presents an extremely safe profile, only high dose of CBD (120 nmol) could halt the IDD progression. |
| Epigallocatechin 3-gallate (EGCG) | |
| Study | Krupkova et al. 2014 50 |
| Aim | To analyze the effect of EGCG on discogenic pain |
| Animal/Patient-model | Sprague-Dawley Rat (G: female, n=60), Autologous NP was harvested from the tail and applied to the dorsal root ganglion (DRG, L5-L6) |
| Intervention | Local injection of 0.1ml EGCG (10 and 100μM) into the underlayer of epineurium |
| Analysis | Hind paw withdrawal response to von Frey Filament test (2, 7, 14, 21 and 28 d post-surgery) |
| Results/Conclusion |
von Frey Filament test: During 28 days, NP+EGCG treatment significantly increased mechanical withdrawal thresholds in comparison to the NP+vehicle group, and reached levels measured in the sham group. Conclusion: EGCG (10 and 100μM) inhibits pain behaviour in vivo. |
| Urolithin A (UA) | |
| Study | Liu et al. 2018 54 |
| Aim | To assess the beneficial effect of UA on IDD |
| Animal/Patient-model | Sprague-Dawley Rat (G: male, n=30), puncture-induced rat IDD model |
| Intervention | Oral delivery of UA (0.25 g per kg of diet or 25 mg/kg/day) |
| Analysis | X-ray, MRI and histopathology (4 weeks post-surgery) |
| Results/Conclusion |
X-ray: UA treatment group showed no significant disc space. MRI: Pfirrmann grade scores were lower in the UA treatment group than the IDD control Histopathology: UA treatment group considerably alleviated IVD destruction in comparison to the IDD control Conclusion: UA may be a useful small molecule for the treatment of IDD. |
| Estradiol (E2) | |
| Study | Jin et al. 2018 121 |
| Aim | To analyze the effect of E2 on IDD in the model of menopause rats |
| Animal/Patient-model | Sprague-Dawley Rat (G: female, n=30), oophorectomy (OVX) to induce menopausal in rats |
| Intervention | 10 µg/kg/day E2 supplementation for 12 weeks |
| Analysis | MRI, histopathology, IHC (LC3 for autophagy) (12 weeks post-surgery) |
| Results/Conclusion |
MRI: T2 mapping showed a marked increase in results in OVX + E2 and sham when compared to OVX + vehicle Histopathology: The OVX + E2 treatment group showed the NP tissues were similar to those observed in the sham group IHC: There are no significant differences between OVX + E2 treatment and sham group in terms of autophagy Conclusion: E2 via regulating the redox balance (autophagy) of IVD could be a potential therapeutic agent for IDD in the postmenopausal women. |
| Study | Liu et al. 2018 132 |
| Aim | To further explore whether estradiol (E2) had protective effects on IDD in OVX rats |
| Animal/Patient-model | Sprague-Dawley Rat (G: male, n=40), puncture-induced OVX-rat IDD model |
| Intervention | Subcutaneous injection of 20 µg/kg/day E2 for 28 d |
| Analysis | X-ray (disc height index-DHI), histopathology, IHC, western blot (WB) (30 d post-surgery) |
| Results/Conclusion |
X-ray: In OVX + E2 treated animals, X-ray showed a markedly higher DHI in comparison to the OVX+ vehicle group. Histopathology: Mean histological scores in Sham and OVX + E2 group were significantly lower than OVX+ vehicle group IHC: E2 downregulated caspase-3, MMP-3 and MMP-13 proteins level but upregulated collagen Type II WB: Confirmed IHC results Conclusion: E2 shows protective effects against IDD by down-regulating catabolic proteins and up-regulating anabolic ones in OVX- animal models. |
| Icariin | |
| Study | Hua et al. 2020 146 |
| Aim | To explore the effect of icariin on IDD |
| Animal/Patient-model | Sprague-Dawley Rat (G: male, n=24), needle puncture model |
| Intervention | Intraperitoneal administration of icariin (30 mg/kg) for 8 w post-surgery |
| Analysis | MRI and histopathology (8 weeks post-surgery) |
| Results/Conclusion |
MRI: Pfirrmann grade scores were significantly lower in the icariin treatment group than the saline treatment Histopathology: Icariin treatment reduced histopathological changes (disruption of AF), although some degeneration was still observed Conclusion: Icariin could be utilized as a protective agent to inhibit further degeneration after injury. |
| Resveratrol | |
| Study | Kwon 2013 91 |
| Aim | To evaluate whether resveratrol had anabolic effects on IDD in a rabbit model |
| Animal/Patient-model | New Zealand white rabbit (G: male, n=24), needle puncture model |
| Intervention | Two times intradiscal injections of 15 µL of 100 µM resveratrol in DMSO, repeat dose administrated 2 weeks after the first injection |
| Analysis | MRI (4, 8, 16 weeks after the initial injection), histopathology (16 weeks after the initial injection) |
| Results/Conclusion |
MRI: MRI scores significantly lower in the resveratrol group than the DMSO (vehicle) group Histopathology: Significant higher histological grades are noted in the DMSO group when compared with the resveratrol group Conclusion: icariin may be a promising candidate for the treatment of IDD. |
| Study | Lin et al. 2016 117 |
| Aim | To assess the effect of resveratrol of on NP-mediated (discogenic) pain |
| Animal/Patient-model | Sprague-Dawley Rat (G: female, n=36), NP-mediated radiculopathy (model) |
| Intervention | Local injection of 0.1ml resveratrol (50 µM) into the underlayer of epineurium |
| Analysis | von Frey filaments test (0, 3, 7, 14, 21 d post-surgery), histopathology and IHC (7 and 14 d post-surgery). |
| Results/Conclusion |
von Frey filaments test: significant pain reduction by resveratrol treatment Histopathology and IHC: resveratrol treatment showed improved cell structure, with decreased edema and focal hyperemia compared with the negative control group. The expression level of IL-1 and TNF-α proteins decreased by resveratrol treatment. Conclusion: The results indicate the potential of resveratrol for attenuating discogenic pain. |
| Celecoxib (CXB) | |
| Study | Willems et al. 2015 141 |
| Aim | To assess the effect of controlled delivery of CXB on IVD regeneration |
| Animal/Patient-model | Dog (G: female, n=18), canine model of spontaneous mild IDD |
| Intervention | a bolus intradiscal injection of CXB (7.7 μM), intradiscal injection CXB loaded hydrogel (77 μM and 770 μM) |
| Analysis | Histopathology and IHC, Q-PCR (4 weeks after the initial injection) |
| Results/Conclusion |
Histology and IHC: No significant differences were found between the injected treatments Q-PCR: Only relative gene expression levels of BCL2 and PGE2 were significantly downregulated in the CXB-loaded hydrogel in comparison to the sham Conclusion: The controlled delivery of CXB resulted in limited inhibition of PGE2 production in dogs with spontaneous IDD Limitations: Due to technical limitations, it was impossible to determine the CXB tissue levels, and hence in vivo release profile of CXB. |
| Study | Tellegen et al. 2018 61 |
| Aim | The effect of control release of CXB on IVD regeneration |
| Animal/Patient-model | Dog (G: male, n=6), canine IDD model |
| Intervention | One month after surgery, Intradiscal delivery of 40 µl CXB loaded microsphere (CXB-M), low (8.4 µg CXB) and high dose (280 µg CXB) |
| Analysis | MRI (0 d, 4 and 12 weeks after injection), histopathology and IHC (12 weeks after the initial injection) |
| Results/Conclusion |
MRI: DHI was maintained in the disc treated with either low or high dose CXB-M, Pfirrmann score was lower in CXB-M treated groups compared to the negative control Histopathology and IHC: Controlled release of CXB inhibited progression of IDD, the development of osteophyte formation, and decreased the immunopositivity of nerve growth factor Conclusion: Intradiscal controlled release of CXB inhibited progression of IDD in vivo. |
| Study | Tellegen et al. 2018 115 |
| Aim | To assess the impact of sustain delivery of CXB on discogenic pain |
| Animal/Patient-model | Dog (G: female, n=10), canine patients with low back pain |
| Intervention | Intradiscal injection loaded hydrogel containing 2.93 μg/mL CXB |
| Analysis | MRI (0 d and 12 weeks after injection), clinical examination of low back pain (12 weeks after the initial injection) |
| Results/Conclusion |
MRI: No evident of CXB regenerative effects on MRI Clinical examination: The reduction of back pain achieved in 9 of 10 dogs. In 3 of 10 dogs, back pain recurred after 12 weeks Conclusion: the majority of the treated canine patients, quality of life improved without evident regenerative effects Limitations: small group size, absence of a placebo group. |
| Berberine | |
| Study | Luo et al. 2019 86 |
| Aim | The effects of berberine on IDD were investigated |
| Animal/Patient-model | Sprague-Dawley Rat (G: female, n=24), needle puncture model |
| Intervention | Intraperitoneal administration of berberine (150 mg/kg/day) for 8 weeks post-surgery |
| Analysis | MRI and histopathology (8 weeks post-surgery) |
| Results/Conclusion |
MRI: Pfirrmann scores were significantly lower in the berberine treated animals than the saline treatment Histopathology: The histological scores in the berberine treatment group significantly lower than IDD control group (saline). Conclusion: Berberine could attenuate puncture-induced IDD in animal model. |
| Metformin | |
| Study | Chen et al. 2016 92 |
| Aim | To assess the effects of Metformin on IDD |
| Animal/Patient-model | Rat (G: NI, n=NI), puncture-induced IDD model |
| Intervention | Intraperitoneal administration of metformin (50 mg/kg/day) for 16 weeks post-surgery |
| Analysis | MRI and histopathology (8-16 weeks post-surgery) |
| Results/Conclusion |
MRI: Metformin treated group showed lower Pfirrmann scores compared to the vehicle-treated animals Histopathology: The histologic score of the metformin group was significantly lower than those of negative control both at 8- and 16-weeks post-surgery Conclusion: Metformin showed a protective effect against progression of IDD. |
| SM04690 | |
| Study | Barroga et al. 2017 109 |
| Aim | To investigate the effects of SM04690 on IDD |
| Animal/Patient-model | Rat (G: NI, n=NI), puncture-induced IDD model |
| Intervention | Single intradiscal of SM04690 (0.066 mg/disc) |
| Analysis | X-ray and histopathology (6 weeks post-surgery) |
| Results/Conclusion |
X-ray: % DHI in SM04690 treated animals significantly increased compared to vehicle control Histopathology: Treatment by SM04690 increased number of NP cells and increased ECM vs. vehicle control Conclusion: SM04690 has potential as a modifying therapy for IDD. |
| Gefitinib | |
| Study | Pan et al. 2018 20 |
| Aim | to investigate the therapeutic potential of gefitinib in ameliorating IDD |
| Animal/Patient-model | Sprague-Dawley Rat (G: female, n=18), puncture-induced IDD model |
| Intervention | Three µl aliquots intradiscal injection of gefitinib (30 mM) |
| Analysis | MRI and histopathology (4 weeks post-surgery) |
| Results/Conclusion |
MRI: DHI% values of the gefitinib-treated group were significantly higher than those of the IDD control. The Pfirrmann scores also showed that the degree of disc degeneration was markedly lower in the gefitinib-treated group as well. Histopathology: The gefitinib treatment considerably decreased the histological scores in comparison to IDD control group. Conclusion: The results suggest the potential application of gefitinib for treating IDD. |
| Statin | |
| Study | Than et al. 2014 142 |
| Aim | To find a new conservative treatment for IDD and related discogenic pain |
| Animal/Patient-model | Sprague-Dawley Rat (G: NI, n=272), puncture-induced IDD model |
| Intervention | Six weeks post-surgery, intradiscal injection of 2μL simvastatin (SIM) at 3 different doses (5, 10, or 15 mg/mL) in either a saline or hydrogel carrier |
| Analysis | MRI and histopathology and IHC (2, 4, 8, 12 and 24 weeks after the initial injection) |
| Results/Conclusion |
MRI: MRI analysis showed a higher index (better results) for treatment with 5 mg/ml SIM administered in comparison to the higher doses (15 mg/ml), MRI index: 5 mg/ml hydrogel>5 mg/ml saline>10 mg/ml saline>15 mg/ml saline>15 mg/ml hydrogel Histopathology and IHC: histological grades confirmed the MRI results Conclusion: Intradiscal injection of simvastatin into IDD may result in retardation of degeneration process (5 mg/ml simvastatin in a hydrogel carrier) Limitation: unbalanced time point analysis for all groups, Control group was assessed only histologically. |
| Luteoloside | |
| Study | Lin et al. 2019 57 |
| Aim | To investigate the protective potential of luteoloside in IDD |
| Animal/Patient-model | Sprague-Dawley Rat (G: NI, n=36), puncture-induced IDD model |
| Intervention | Intraperitoneal injection of 10mg/kg/day luteoloside for 4 and 8 weeks post-surgery |
| Analysis | MRI, X-ray and histopathology (4, and 8 weeks post-surgery) |
| Results/Conclusion |
MRI: Pfirrmann MRI grade scores were significantly lower in the luteoloside group than in the IDD group X-ray: DHI was significantly lower in the IDD group than in the luteoloside treatment group Histopathology: Both ECM and NP tissues were better preserved in the luteoloside-treated group when compared to the IDD group Conclusion: Luteoloside only ameliorate IDD progression during long-term follow-up (8 weeks). |
| Curcumin | |
| Study | Ma et al. 2015 145 |
| Aim | To observe the effect of curcumin on IDD |
| Animal/Patient-model | Sprague-Dawley Rat (G: male, n=60), Surgically induced IDD model in the lumbar area (removal of the spinous processes, the articular processes, the supraspinous ligaments and the interspinous ligaments). |
| Intervention | Intraperitoneal injection of 50mg/kg and 100mg/kg curcumin (single dose) |
| Analysis | MRI, Electron microscopy (EM), RT-PCR, and western blot (WB) (6 weeks post-surgery) |
| Results/Conclusion |
MRI: The IVD signals of curcumin-treated animals (L1-6) were slightly lower than those in the normal group but were considerably higher than those of IDD models. EM: The degree of degeneration related to NP, AF and ECM structure of IVD samples was better in curcumin-treated animals in comparison to the IDD models RT-PCR: The expression levels of NF-κB-p65 and TNF-α were significantly lower in curcumin-treated animals than the other groups. WB: curcumin-treated animals had significantly lower NF-κB-p65 and TNF-α expression levels than IDD animal models. Conclusion: curcumin can decelerate the IDD process by blocking the NF-κB-p65 pathway and reducing inflammatory factors Limitation: 1. No statistical analysis was performed on the differences between each group regarding the MRI test. 2. Lack of further verification of the type of lumbar IDD and related IDD categorization. |
G: gender, NI: no information.