Fig 2: PDGF-BB is expressed in nucleus pulposus tissue and NP cells. (A) MRI of intervertebral discs; (i) patient with L4 vertebral fractures; (ii) patient with L4/5 disc herniation. (B) Hematoxylin and eosin staining of nucleus pulposus tissue in patients with vertebral body fracture and lumbar disc herniation. Scale bar, 50 µm. (C) Immunohistochemical images of COL2, MMP3 and PDGF-BB of human nucleus pulposus tissue. Scale bar, 100 µm. (D,E) Immunohistochemical images of PDGF-BB of mouse intervertebral disc. Average percentage of positive staining area of PDGF-BB. Scale bar, 200 µm. (F) ELISA shows the expression of PDGF-BB in mouse intervertebral disc. (G–I) Quantitative PCR, ELISA and Western blot were used to detect PDGF-BB of NP cells. (J) Immunofluorescence images of P-PDGFR of NP cells. Scale bar, 100 µm. All NP cells were treated with or without IL-1ß (10 ng/ml) for 48 h. Data are presented as the mean ± SD. Significant differences between groups are indicated as ****p < 0.0001, ***p < 0.001, **p < 0.01.

Fig 3: Gene expression of chondrogenic and hypertrophic markers for PCL, PCL/RAD and RAD samples under expansion or chondrogenic media for 30 days. (a) Collagen type I (COL1A1), (b) collagen type II (COL2A1), (c) collagen type X (COL10A1), (d) RUNX2, (e) SOX9 and (f) aggrecan (ACAN) were determined through qRT-PCR. Ct values relative human beta actin (ACTB) were obtained and reported as fold increase (??Ct) relative to 2D cultures (Statistical differences are indicated as: *p < 0.05, **p < 0.01, ***p < 0.001 and ****p < 0.0001, two-way ANOVA). n = 3.

Fig 4: TrkA agonism increases cartilage and bone antigen expression after extremity injury. Immunohistochemical staining within injured tissues of Gambogic Amide (GA) or control treated animals. Representative sagittal sections of the proximal tenotomy site shown, at either 3 or 9 weeks post-injury. (a, b) Aggrecan (ACAN) immunohistochemical staining, 3 weeks post-injury. (c, d) Type II Collagen (Col2) immunohistochemical staining, 3 weeks post-injury. (e, f) Type X Collagen (ColX) immunohistochemical staining, 3 weeks post-injury. (g, h) Osteocalcin (OCN) immunohistochemical staining, 9 weeks post-injury. Dashed white lines indicate the margins of the Achilles tendon. High magnification images are shown in yellow dotted frame. N = 5 animals per group. *P < .05, **P < .01. Scale bar: 100 µm.

Fig 5: Traumatic impact-induced changes in matrix deposition and catabolic enzyme production. Rows: Engineered cartilage constructs were subjected to 30% strain or exposed to 10 ng/ml IL-1ß at 1, 3 and 7 days of culture. Columns: samples were histochemically stained with hematoxylin and eosin or Safranin O/Fast Green or immunohistochemically processed to detect COL2, MMP13 or ADAM-TS4. magnification = 100 × (inset = 40 ×)