Fig. 4

Representative marker expression in the anterior cruciate ligament (ACL) of control and post-trauma mouse knee joints with immunohistochemistry. A, B The ACLs of healthy (n = 6) (A) and post-trauma knee joints (n = 6) (B) were analysed across microanatomical regions. C–E Collagen type II (COL2) expression was present in the fibrocartilaginous tibial enthesis of the healthy ACL and in the mid-substance region of the post-trauma ACL (black arrows). F–H SOX9 chondrogenesis transcriptional factor expression was found in the tibial enthesis and mid-substance regions of the post-trauma ACL (black arrows). I–K RUNX2 hypertrophic transcriptional factor was expressed in the tibial enthesis region of the post-trauma ACL (black arrows). L–N Asporin (ASPN), a small leucine-rich proteoglycan, extended within the mid-substance of the post-trauma ACL. Scale is 25 μm for C–N, and 50 μm for A–B. Post-trauma ACL images are from + 4 weeks post-trauma