Comparative Clinical Outcomes After Intra-articular Injection With Adipose-Derived Cultured Stem Cells or Noncultured Stromal Vascular Fraction for the Treatment of Knee Osteoarthritis: Letter to the Editor

Abstract

Biologic therapies have huge potential in orthopaedic sports medicine. 4 To reach scientific evidence on stem cells or platelet-rich plasma, many articles of the American Journal of Sports Medicine have addressed this issue. The article by Yokota and coworkers 6 has provided new insight into the role of mesenchymal stem cells (MSCs) on osteoarthritis treatment. It is worth pointing out that Japan's Regenerative Medicine Promoting Act on the Safety of Regenerative Medicine makes it easier to develop research in this field. However, heterogeneity among formulations is the more relevant drawback to obtain definite conclusions when comparing results of different studies. The understanding of the mechanism of action is hampered, among others, by this lack of international standards. 1,5 In their study ''Comparative Clinical Outcomes After Intra-articular Injection With Adipose-Derived Cultured Stem Cells or Noncultured Stromal Vascular Fraction for the Treatment of Knee Osteoarthritis,'' Yokota et al did not specify the stromal vascular fraction (SVF) product composition before the injection. The authors stated that ''the number of cells injected was unknown for the SVF group as the entire 5 mL of SVF produced was subsequently injected.'' We believe that this is a methodological pitfall that could lead to inconsistent conclusions. The authors established that ''adipose stem cells (ASCs) are as safe as and potentially more effective than SVF for intra-articular injection in patients with knee osteoarthritis.'' Obviously, comparison between these 2 cohorts is not feasible, since the number of SVF-viable cells is unknown. Furthermore, the authors concluded that the ASC treatment outperformed the SVF one partly because of the lower proportion of hematopoietic cells and higher frequency of colony-forming unit fibroblasts. There is consistent scientific evidence that MSCs' beneficial effect is achieved through an immunomodulatory and paracrine mechanism. 2 Concerning this, SVF has better cell composition to permit MSC action. Another point to comment is the administration of nonsteroidal anti-inflammatory drugs after the injection. There is scientific evidence to suggest a potential interaction between these drugs and a regenerative medicine product; thus, their use is not recommended immediately after the biological treatment injection. 3 For all of the aforementioned, we firmly believe that the study's weaknesses undermine its conclusions.