Arthritis - Osteoarthritis
Novel and Emerging Therapies
Tanezumab is an antibody that targets nerve growth factor (NGF), which plays a significant role in pain transmission (Cattaneo 2010). Among patients with osteoarthritis (OA) of the knee, tanezumab was associated with a significant reduction in pain intensity (Felson 2011). However, in June 2010, the FDA put all trials of tanezumab on hold because a significant number of patients taking this drug experienced an unusually rapid progression of joint bone necrosis (Lane 2010). Some researchers claim this bone necrosis occurred because of overuse of the joint (due to the potent analgesic effect of tanezumab). However, the FDA is waiting for more information on the exact cause of this adverse effect before allowing trials to continue (Wood 2010; Lane2010).
Stem cells are renewable, unspecialized precursor cells that can transform into specialized cell types (Vrtovec 2013; Singh 2016). Embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells have all been investigated for their regenerative potential in osteoarthritis. Of these, mesenchymal stem cell therapy is considered the most promising. Mesenchymal stem cells can be isolated from adipose tissue, bone marrow, umbilical cord, and other sites (Burke 2016; Freitag 2016; Filardo 2013; Richardson 2016).
Mesenchymal stem cells derived from bone marrow can be delivered as a simple concentrate that can be prepared on-site. Such preparations include mesenchymal stem cells in addition to several other types of cells from bone marrow. Therefore, it can be difficult to pinpoint exactly which types of cells are responsible for the effects of the procedure. This technique has the added value of convenience, as it can be performed during a single office visit. In another approach, stem cells are isolated from bone marrow and cultured to generate specific cell types. Both types of stem cell preparations can be delivered by injection or during surgery (Filardo 2016; Burke 2016).
Adipose-derived mesenchymal stem cells are readily available, as they can be obtained by less invasive measures than bone marrow, including liposuction. Adipose tissue also contains connective tissue abundant in stromal vascular fraction, a rich source of stem cells. Adipose-derived stem cells are generally less efficient than bone marrow-derived stem cells in stimulating cartilage synthesis, but adipose taken from near the knee appear to be suitably efficacious in this regard and warrant further study (Filardo 2016; Burke 2016; Koga 2008; Jang 2015). Multiple trials using adipose-derived mesenchymal stem cells have reported positive clinical results in osteoarthritis, including decreased pain and improved function. Improved cartilage status as verified by arthroscopy and MRI has also been observed, implying the treatment resulted in cartilage regeneration (Koh 2015; Michalek 2015; Burke 2016; Pak 2016).
Individual patient characteristics appear to influence the outcomes of mesenchymal stem cell therapy in osteoarthritis, as better clinical results have been observed in younger individuals, and those with lower BMI, smaller areas of cartilage degradation, and earlier stage of osteoarthritis progression. Studies have not reported any major adverse events associated with mesenchymal stem cell harvest or therapy, and most studies report some clinical benefit (Filardo 2013; Filardo 2016). Nevertheless, the effectiveness of stem cell therapy for osteoarthritis has not been conclusively established.
Apitherapy, the use of bee venom for medicinal purposes, including relieving joint pain, can be dated back to at least the 5th century BC (Alqutub 2011). More recently, there have been numerous anecdotal reports of bee stings dramatically improving symptoms of OA (Mayo Clinic 2009b). Bee venom, when combined with acupuncture for the treatment of OA of the knee, was associated with a substantial analgesic effect compared to traditional (needle-only) acupuncture (Kwon 2001). Researchers believe that the anti-inflammatory characteristics of bee venom can be attributed to mellitinin, a component of bee venom that is one hundred times stronger than the inflammation-reducing hormone cortisone (Alqutub 2011).