Acupoint nanocomposite hydrogel for simulation of acupuncture and targeted delivery of triptolide against rheumatoid arthritis

Abstract

Background: Attenuating inflammatory response and relieving pain are two therapeutic therapeutical goals for rheumatoid arthritis (RA). Anti-inflammatory and analgesic drugs are often associated with many adverse effects due to nonspecific distribution. New drug delivery systems with practical targeting ability and other complementary strategies urgently need to be explored. To achieve this goal, an acupoint drug delivery system that can target deliver anti-inflammatory drugs and simulate acupuncture in relieving pain was constructed, which can co-deliver triptolide (TP) and 2-chloro-N (6)-cyclopentyl adenosine (CCPA).

Results: We have successfully demonstrated that acupoint nanocomposite hydrogel composed of TP-Human serum album nanoparticles (TP@HSA NPs) and CCPA could effectively treat RA. The result shows that CCPA-Gel can enhance analgesic effects specifically at the acupoint, while the mechanical and thermal pain threshold was 4.9 and 1.6 times compared with non-acupoint, respectively, and the nanocomposite gel further enhanced. Otherwise, the combination of acupoint and nanocomposite hydrogel exerted synergetic improvement of inflammation, bone erosion, and reduction of systemic toxicity. Furthermore, it could regulate inflammatory factors and restore the balance of Th17/Treg cells, which provided a novel and effective treatment strategy for RA. Interestingly, acupoint administration could improve the accumulation of the designed nanomedicine in arthritic paws (13.5% higher than those in non-acupoint at 48 h), which may explain the better therapeutic efficiency and low toxicity.

Conclusion: This novel therapeutic approach-acupoint nanocomposite hydrogel, builds a bridge between acupuncture and drugs which sheds light on the combination of traditional and modern medicine.

Keywords: Acupuncture; Controlled release; Rheumatoid arthritis; Triptolide.

Fig. 1

Therapeutic mechanism of nanocomposite hydrogel against RA. Acupoint nanocomposite hydrogel consists of CCPA and TP@HSA NPs not only simulate acupuncture in relieving pain by stimulating A₁R, but also targeted deliver TP to suppress inflammation through regulating inflammatory factors and restoring immune balance

Fig. 2

Fabrication and characterization of nanocomposite hydrogel. a Schematic representation of construction of nanocomposite hydrogel. b TEM of gel in different concentration (1% and 2%, w/v) c The size distribution and TEM image of TP@HSA NPs. d Macroscopic images,SEM and images of injection through needle showing of blank gel and nanocomposite hydrogel. e Strain-dependent oscillatory shear rheology of blank gel and nanocomposite hydrogel. f Step-shear measurements of blank gel and nanocomposite hydrogel over two cycles with alternating high shear (100 s⁻¹) and low shear (0.05 s⁻¹) rates. g Release profile of CCPA from nanocomposite hydrogel. h Release profile of TP from TP@HSA NPs in different pH and nanocomposite hydrogel

Fig. 3

Biodistribution of TP@HSA NPs and TP@HSA NPs-Gel administrated in ST36 and non-acupoint. a Imaging of AIA mice treated with different preparations at different point-in-times (the fluorescence scale bar of hind paw in each side corresponds to the white arrow). b Imaging of organs in different groups. c Quantitative analysis of fluorescence in different organs at different time. d Pharmacokinetics of TP in different groups (the insert is local magnification of 0–4 h). e AUC of TP in different groups. T0: ST36 TP solution; T1: non-acupoint TP@HSA NPs; T2: ST36 TP@HSA NPs; T3: ST36 TP@HSA NPs-Gel

Fig. 4

Analgesic and anti-inflammatory effects of ST36 nanocomposite hydrogel. a The schematic diagram of experiment procedure. b Mechanical allodynia (paw withdrawal latency in grams) among the different groups. c Thermal hyperalgesia (paw withdrawal threshold in seconds) among four groups. d Photographs of representative mice hand paws among the six groups. (Normal: healthy mice treated with saline, Model: AIA mice treated with saline, G1: ST36 TP-CCPA-solution, G2: ST36 TP-CCPA-Gel, G3: ST36 TP@HSA NPs-CCPA-Gel, G4: Non-acupoint TP@HSA NPs-CCPA-Gel) e–g Hind paw thickness, volume, and arthritis scores changes of the mice. Data (means ± SD) shown are pooled from two independent experiments with similar results. (n = 6, *p < 0.05, **p < 0.01, and ***p < 0.001)

Fig. 5

In vivo anti-arthritis efficacy of acupoint nanocomposite hydrogel. a Histological sections with H&E, Masson, SO-FG and T&B staining of joints in different groups. G1: ST36 TP-CCPA-solution, G2: ST36 TP-CCPA-Gel, G3: ST36 TP@HSA NPs-CCPA-Gel, G4: Non-acupoint TP@HSA NPs-CCPA-Gel). Asterisks: formation of pannus. Red arrows: invasion of inflammation. Green arrows: destruction of cartilage. Blue line: narrow joint space. Yellow arrows: destruction of cartilage. Black triangle: loss of proteoglycan. Scale bar: 200 μm. b Histopathologic scores of synovial inflammation, bone erosion, and cartilage degradation. *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 6

Immunohistochemistry analysis of articular tissues. a immunohistochemical image of cartilage and synovium in different groups. Black arrows: positive staining. Scale bar:100 μm. b Quantification of the IL-1β, IL-6 and TNF-α production in the tissues treated with different samples based on the immunohistochemical results. G1: ST36 TP-CCPA-solution, G2: ST36 TP-CCPA-Gel, G3: ST36 TP@HSA NPs-CCPA-Gel, G4: Non-acupoint TP@HSA NPs-CCPA-Gel. Data are reported as mean ± SD (n = 3), *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 7

Evaluation of regulating the expression of inflammatory factors and immune cells. a Serum concentration of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-17A) and anti-inflammatory cytokines (IL-10 and TGF-β1). b–e FACS data is shown on the left panel. The right panel shows the summarized data. G1: ST36 TP-CCPA-solution, G2: ST36 TP-CCPA-Gel, G3: ST36 TP@HSA NPs-CCPA-Gel, G4: Non-acupoint TP@HSA NPs-CCPA-Gel. Data are reported as the mean ± SD (n = 6, *p < 0.05, **p < 0.01, and ***p < 0.001)

Fig. 8

H&E-stained images of major organs (heart, liver, spleen, lungs, and kidneys), Blue arrow represents myocardial cell swelling and green arrow represents inflammatory cells infiltration. G1: ST36 TP-CCPA-solution, G2: ST36 TP-CCPA-Gel, G3: ST36 TP@HSA NPs-CCPA-Gel, G4: Non-acupoint TP@HSA NPs-CCPA-Gel. Scale bar:100 μm