gms | German Medical Science

Objectives: Stromal vascular fraction (SVF) has been used preclinically and clinically to treat late-stage knee osteoarthritis (OA) and reports of sustainable pain reduction are available. Derived from adipose tissue, SVF is a heterogeneous mixture of cells, including mesenchymal stromal cells, endothelial cells, pericytes, and immune cells. Paracrine activity is likely to modulate the local intraarticular (IA) immune response and reduce the low-grade inflammation present in primary OA. Whether SVF may also have a tissue protective effect during early disease stages remains speculative. Here, we investigated the therapeutic potential of SVF in a primary model for knee OA (Dunkin Hartley guinea pig model).

Methods: Ten female and 10 male, 6-month-old Dunkin Hartley guinea pigs with mild-moderate knee OA were randomized to two groups to either receive a single 200 uL IA injection of Dulbecco’s phosphate buffered saline (DPBS) or SVF (1 million cells) in DPBS per knee joint. One and six months following injection, animals underwent MRI examinations of knee joints in a 3T scanner. Cartilage and adjacent joint tissues were evaluated on sagittal plane images by a blinded investigator.

Following the second MRI animals were euthanized and both knees were collected for histological analysis. Three non-consecutive coronal sections among the central sections of each sample were stained with toluidine blue. An assessment of joint degeneration was conducted using the Osteoarthritis Research Society International (OARSI) scoring system, performed in a blinded manner. Paired data were analyzed using the Wilcoxon paired rank test and the significance level was set at α = 0.05.

Results and conclusion: We did not observe any acute or delayed adverse reactions, including systemic and local immune reactions, joint swelling, redness and limping following IA injections. Further, SVF treatment did not provoke ectopic bone formations, synovial infiltration, Hoffa fat pad synovitis, full-thickness osteochondral defects, or gross joint instability.

Significantly higher proteoglycan content (p = 0.030) and relatively well-preserved cartilage structures (p = 0.236) were observed in the SVF group when compared to the control DPBS group. Total OARSI scores were significantly lower in the SVF group than in the control group (p = 0.043), indicating a partial inhibition and deceleration of OA progression in animals receiving SVF (Figure 1 [Fig. 1]).

First histopathological results of this in vivo study indicate that SVF is safe and has a tissue preserving effect in early-stage primary knee OA. By targeting the low-grade inflammation present at an early disease stage SVF may ensure permanent structural protection of cartilage.