Clinical Case Review

CURRENT STEM CELL RESEARCH

Andy Hoffman, D.V.M., D.V.Sc., D.A.C.V.I.M., Professor, Director, Lung Stem Cell Laboratory and Jose Garcia-Lopez, DVM, DACVS, Associate Professor.

The clinical scenario:

Charger, a 9-year-old Oldenburg gelding, presented to clinicians at the Hospital for Large Animals at the Cummings School of Veterinary Medicine at Tufts University for non-resolving hind limb lameness. During evaluation, Charger displayed excessive toe dragging of the rear limbs and abduction (outward swinging) of the right hind. When trotting, Charger exhibited a 2 out of 5 (0= sound; 5= non-weight bearing) right hind limb lameness, with a positive upper limb flexion test (indicating pain in the upper portion of the leg).

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Image I: Ultrasound images of normal joint cartilage and a subchondral bone cyst.

In order to localize the problem better, a regional nuclear scintigraphic evaluation (bone scan) was performed along with radiographs and ultrasound. Results of the bone scan showed a localized and active region of radioisotope uptake (hot spot) at the level of the inner knee joint (medial femoral condyle) of the right hind limb. This was confirmed to be a cyst beneath the knee joint cartilage via radiographs and ultrasound of the region (subchondral bone cyst in the right medial femoral condyle, SEE IMAGE I). Ultrasound demonstrated no damage to the surrounding soft tissue structures.

Based on these findings an arthroscopic debridement of the cyst and injection of autologous stem cells (from the same animal) derived from a fat sample was recommended. Fat was harvested from Charger’s right croup, shipped to and processed by a private company to isolate ‘stem cells’, which were shipped back within 48 hours for subsequent injection.

During arthroscopic surgery, the subchondral cyst was cleaned down to healthy bleeding bone (SEE IMAGE II). The joint was thoroughly cleansed and stem cells were inserted into the defect along with a platelet rich plasma (PRP) clot to ensure position was preserved.  The incisions were closed and recovery was uneventful.

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Image II: Endoscopic images of a femoral cyst (a), which was debrided (b) and then packed with 10 million, bone marrow derived stem cells suspended in platelet rich plasma and fixed with fibrin (c).

Following surgery, Charger was placed on short term intravenous antibiotics and anti-inflammatories (Phenylbutazone) until being discharged. The postsurgical examination at months two and four showed adequate healing of the cyst. The horse was returned to his previous level of athletic activity within six months following surgery.

This case demonstrates how autologous stem cells can be derived from fat tissue for use in joint disease.  These same fat-derived stem cells in addition to stem cells derived from bone marrow and even umbilical cord tissue have been widely employed to treat a variety of soft tissue injuries in horses.   The question remains about how to optimize these therapies.  Which stem cell types are best suited for which injuries?    By what methods should cells be handled, processed, even cultured? In this case, cells were directly (enzymatically) removed from fat and shipped back for injection.  Questions remain about how best to address purity, viability and potency of stem cells which are handled, processed and shipped.    However, the case demonstrates that stem cells have potential to be safely transplanted and to contribute to healing of a cyst that is traditionally very difficult to treat.