Background/Purpose

Regeneration of hyaline cartilage has been an attractive approach to cartilage repair and therapy of osteoarthritis (OA), but remains to be a challenge. SOX9 is a transcription factor belonging to the Sox (Sry-type HMG box) gene family and has been identified as a “master regulator” of chondrogenesis. We reported previously that a super positively charged cell penetrating SOX9 fusion protein (scSOX9) can induce bone marrow-derived mesenchymal stem cells (MSC) to differentiate into chondrocytes in vitro. Here we investigated the in vivo use of scSOX9 to promote hyaline cartilage regeneration in situ in combination with microfracture for articular cartilage repair in a rabbit model.  

 

Methods

scSOX9) was generated by fusing SOX9 with a super positively charged green fluorescence protein. A 4 mm in diameter, full-thickness cartilage defect was created at the right femoral trochlear groove in New Zealand female rabbits. Microfracture was performed using a 0.9 mm Kirschner wire tapped into the subchondral bone to a depth of approximately 3 mm. Three microfracture holes were created within each full-thickness chondral defect in a triangular configuration. scSOX9 was administered at the site of mcrofracture via a bilayer collagen membrane. Cartilage repair was assessed at 8 weeks by gross morphology, histology and analysis of matrix component and was quantified using International Cartilage Repair Society (ICRS) macroscopic scale and ICRS Visual Histological Assessment Scale (ICRS-VHAS). High scores indicate high quality of repaired cartilage.

Results

After creation of cartilage defect, rabbits were divided into 4 groups (n=4 in each group) for treatment: Group 1, un-treated, Group 2, microfracture only , Group 3, microfracture plus scMyoD (a control protein for scSOX9) and Group 4, microfracture plus scSOX9.  As shown in Table 1, microfracture plus scSOX9 significantly improved cartilage repair with nearly 100% defect area being covered with repaired tissue compared with 78% in Group 3, 80% in Group 2 and 18% in Group 1 respectively. Compared with all other groups, morphologically microfracture plus scSOX9 induced hyaline like cartilage which was well integrated with native cartilage and the repaired tissue showed highest intensity of Safranin O staining, indicating the highest density of proteoglycan. 

Table 1. ICRS Macroscopic Scores and ICRS Visual Histological

Assessment Scale

	ICRS Macroscopic Score	P value*	ICRS VHAS	P value*
Group 1	2.5 ± 0.5	< 0.001	3 ± 1.5	<0.001
Group 2	7 ± 2.1	<0.05	14 ± 0.5	<0.005
Group 3	5 ± 2.3	<0.01	6 ± 3.2	<0.01
Group 4	12 ± 1.2		17 ± 1.5

*p value indicated comparison of Group 4 with other groups.  

Conclusion

This short term in vivo study demonstrated that when administered at the site of microfracture, scSOX9 was able to induce reparative tissue with features of hyaline cartilage and significantly improved the outcome of cartilage repair by microfracture. These data suggest combination of microfracture with scSOX9 has great potential being translated into a therapy for cartilage repair and therapy for OA.

---

« Back to 2014 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/regeneration-of-articular-cartilage-in-situ-with-bone-marrow-derived-mesenchymal-stem-cells/