Sodium Hyaluronate-PDGF Repairs Cartilage and Subchondral Bone Microenvironment via HIF-1α-VEGF-Notch and SDF-1-CXCR4 Inhibition in Osteoarthritis

Abstract

Chronic degenerative changes in cartilage and subchondral bone that lead to instability of the cartilage microenvironment are essential for the development of osteoarthritis (OA) in the old. Synchronous repair of cartilage and subchondral bone may be a key strategy for OA treatment. PDGF-BB effectively promoted chondrocyte regeneration and angiogenesis. However, the mechanisms by which PDGF-BB affects subchondral bone and the delivery of PDGF-BB to the joint cavity need to be further explored. In this study, we used sodium hyaluronate to deliver PDGF-BB (SH-PDGF) to the joint space and aimed to determine the mechanisms of SH-PDGF in repairing cartilage and subchondral bone and stabilising the cartilage microenvironment. In this research, we determined the pharmacokinetics of PDGF-BB and SH-PDGF in cartilage. Moreover, we investigated the effects of PDGF-BB and SH-PDGF on cartilage and the subchondral bone microenvironment by identifying changes in the HIF-VEGF-Notch axis and SDF-1-CXCR4 axis in an OA rat model. The results showed that PDGF-BB increased cell viability, decreased HIF-1α levels, inhibited inflammation and improved matrix metabolism in osteoarthritic chondrocytes under hyperoxic or hypoxic conditions. We also found that PDGF-BB and SH-PDGF showed similar effects on repairing cartilage and subchondral bone simultaneously. However, SH-PDGF had some advantages over PDGF-BB in prolonging the injection interval and decreasing the injection time. These protective effects were mediated by the inhibition of both the HIF-1α-VEGF-Notch axis and the SDF-1-CXCR4 axis. The underlying mechanisms include the inhibition of HIF-1α-VEGF-Notch-mediated vessel invasion and SDF-1-CXCR4 axis-mediated crosstalk between cartilage and subchondral tissue.

Keywords: cartilage; microenvironment; osteoarthritis; platelet‐derived growth factor; subchondral bone.

FIGURE 1

(A) The injection and detection strategy to obtain the time‐concentration plot of PDGF‐BB and SH‐PDGF. (B) Time‐concentration plot of PDGF‐BB and SH‐PDGF. Effects of PDGF‐BB and SH‐PDGF on histopathology in OA in vivo (5 rats in each group). (C) HE and toluidine blue staining of cartilage. (D) En bloc basic fuchsin staining of cartilage. (E and F) The OARSI score of cartilage. (G) The HC/CC thickness ratio in cartilage. (H) The number of microcracks in the CC and upper layer of subchondral bone. ns, no significant difference; **p < 0.01; ***p < 0.001.

FIGURE 2

Effects of PDGF‐BB and SH‐PDGF on the microenvironment of cartilage and subchondral bone in OA in vivo (5 rats in each group). (A, B and E, F) Effects of PDGF‐BB and SH‐PDGF on angiogenesis and vessel invasion in subchondral bone. (C and G) Effects of PDGF‐BB and SH‐PDGF on osteoclast formation in subchondral bone determined by TRAP IF. (D and H) Effects of PDGF‐BB and SH‐PDGF on the hypoxic cartilage microenvironment, as shown by pimonidazole IF. ns, no significant difference; *p < 0.05; ***p < 0.001.

FIGURE 3

Effects of PDGF‐BB and SH‐PDGF on HIF‐1α expression in OA in vivo (5 rats in each group). (A and E) Effects of PDGF‐BB and SH‐PDGF on HIF‐1α expression in cartilage determined by FISH. (B and F) Effects of PDGF‐BB and SH‐PDGF on HIF‐1α expression in subchondral bone determined by FISH. (C and G) Effects of PDGF‐BB and SH‐PDGF on HIF‐1α expression in cartilage, as shown by IF. (D and H) Effects of PDGF‐BB and SH‐PDGF on HIF‐1α expression in subchondral bone determined by IF. ns, no significant difference; *p < 0.05; **p < 0.01; ***p < 0.001.

FIGURE 4

Effects of PDGF‐BB and SH‐PDGF on VEGF and Notch1 expression in OA in vivo (5 rats in each group). (A and E) Effects of PDGF‐BB and SH‐PDGF on VEGF expression in cartilage, as shown by IF. (B and F) Effects of PDGF‐BB and SH‐PDGF on VEGF expression in subchondral bone shown by IF. (C and G) Effects of PDGF‐BB and SH‐PDGF on Notch1 expression in cartilage, as shown by IF. (D and H) Effects of PDGF‐BB and SH‐PDGF on Notch1 expression in subchondral bone shown by IF. ns, no significant difference; *p < 0.05; **p < 0.01; ***p < 0.001.

FIGURE 5

Effects of PDGF‐BB and SH‐PDGF on SDF‐1 expression in OA in vivo (5 rats in each group). (A and E) Effects of PDGF‐BB and SH‐PDGF on SDF‐1 expression in cartilage determined by FISH. (B and F) Effects of PDGF‐BB and SH‐PDGF on SDF‐1 expression in subchondral bone determined by FISH. (C and G) Effects of PDGF‐BB and SH‐PDGF on SDF‐1 expression in cartilage, as determined by IF. (D and H) Effects of PDGF‐BB and SH‐PDGF on SDF‐1 expression in subchondral bone determined by IF. ns, no significant difference; **p < 0.01; ***p < 0.001.

FIGURE 6

Effects of PDGF‐BB and SH‐PDGF on NFATc1, CXCR4, ALK1, and ALK5 expression in OA in vivo (5 rats in each group). (A and E) Effects of PDGF‐BB and SH‐PDGF on NFATc1 expression in subchondral bone determined by IF. (B and F) Effects of PDGF‐BB and SH‐PDGF on CXCR4 expression in cartilage, as shown by IF. (C and G) Effects of PDGF‐BB and SH‐PDGF on ALK1 expression in cartilage shown by IF. (D and H) Effects of PDGF‐BB and SH‐PDGF on ALK5 expression in cartilage, as shown by IF. ns, no significant difference; *p < 0.05; **p < 0.01; ***p < 0.001.

FIGURE 7

Schematic model of the effects and mechanisms of PDGF‐BB and SH‐PDGF on synchronously repairing cartilage and subchondral bone and stabilising the cartilage microenvironment in OA.