Adipose Derived Mesenchymal Stem Cells in a Hyaluronic Based Scaffold for Treatment of Osteoarthritis in Horses

Introduction
Adipose-derived mesenchymal stem cells (aSC) make an ideal cell type for the regener- ative treatment of osteoarthritis (oa) (1-3). Direct injection of stem cells for cartilage defects has seen success in animal models (2-4), but scaffolds for pre-differentiation
and delivery have proven to increase efficacy of stem cell therapy (5-7). to treat subchon- dral cartilage defects without surgery a hyaluronic-acid scaffold containing aSC was developed and tested.

Materials and methods
From the horse’s own fat-tissue aSC were isolated and expanded in vitro. at passage two aSC were seeded in an ‘in situ’ cross-linkable hyaluronic acid hydrogel with chon- drogenic growth factors and cultured for one week. MSC (control) and cell-laden hydro- gels were characterized for stem cell properties (proliferation, chondrogenic differentia- tion, viability and cell surface markers). Experiments were carried out in triplicate and statistically analyzed by t-test. in addition, ten horses with oa were treated with the test product while a control group received hyaluronic acid only. Stem cells without scaffold have been tested before (unpublished data) but with undesirable results. Effects were measured after three and six months and compared to 24 hours before treatment; data were analyzed by anoVa.

Results and conclusions
In vitro aSC in our hydrogel formulation were viable, promoted proliferation and retained stem cell properties (CD29+CD44+CD90+). after 24 hours, stem cells in the biostimulative matrix started to pre-differentiate to chondrocytes and after 1 week new cartilage regions were formed. in vivo there was clear evidence in all horses of reduced pain and increased mobility as measured by degree of lameness; decreased inflamma- tion as measured by joint fluid levels (C-reactive protein, colour, clarity); and regenera- tion of cartilage evaluated by Ct scan and/or arthroscopy.
After treatment 90% of horses walked and trotted without lameness and went back to training after 6 months. Long term studies are needed to evaluate oa progression.