Arthroscopy: The Journal of Arthroscopic and Related Surgery
Volume 26, Issue 9 , Pages 1145-1146, September 2010

Author's Reply

Article Outline

 

We read with interest the remarks of Dr. Dines concerning terminology used in articles by Nin et al.,1 Radice et al.,2 Orrego et al.,3 and Vogrin et al.4

We must agree with Dines in his statement that “it is critical … to determine what exactly is being used to improve outcomes” after anterior cruciate ligament (ACL) reconstruction.

The use of growth factors derived from activated platelets has been the focus of many orthopaedic research studies in the last few years; therefore, we can find some misunderstanding regarding the terminology.

Platelet-rich plasma (PRP), also known as platelet-enriched plasma, platelet-rich concentrate, platelet concentrate, or platelet gel, may be defined as the volume of the plasma fraction of autologous blood containing a platelet concentration above the baseline. A concentration of platelets, 5 times higher than the blood, has been suggested to be a working definition for PRP.5

Platelets in the PRP can be activated by the addition of thrombin and calcium, resulting in the release of a cascade of proteins from the α granules. Among them, there is a group of proteins known as growth factors (also known as platelet growth factors). In many texts, including our previous letter to the editor,4 the term “PDGF” has been confusingly used as a synonym for all platelet growth factors. In molecular biology, platelet-derived growth factor (PDGF) is only one of the numerous growth factors or proteins that regulate cell growth and division. They include PDGF, transforming growth factor, platelet factor 4, interleukin 1, platelet-derived angiogenesis factor, vascular endothelial growth factor, epidermal growth factor, platelet-derived endothelial growth factor, insulin-like growth factor, and others.6 The interaction between these growth factors and surface receptors on the target cells activates the intracellular signaling pathways that induce the production of proteins needed for the regenerative processes, such as cellular proliferation, matrix formation, collagen synthesis, and osteoid production.7

In particular, PDGF plays a significant role in blood vessel formation (angiogenesis), the growth of blood vessels from already existing blood vessel tissue. In chemical terms, PDGF is a dimeric glycoprotein composed of 2 A (-AA) or 2 B (-BB) chains or a combination of the 2 (-AB).

It is true that there are recombinant human growth factors available, but they have several disadvantages, including that they have a short life span, they provide inefficient local delivery to target cells, they are expensive, and high doses may be required to achieve any therapeutic effect. In comparison, autologous platelet concentrates offer an easy way to obtain high concentrations of growth factors for tissue healing and regeneration. An important feature of autologous platelet concentrates is also the elimination of allogeneic immune reactions and disease transmission.8

Therefore in our letter regarding our concerns about platelet concentrate, we were actually only discussing the function of autologous platelet growth factors, as a sum of bioactive proteins, released from the platelet α granules in platelet concentrates, as well as their biological effect after application in ACL reconstruction.4

Of course, we agree that randomized, controlled clinical trials are needed to study the beneficial therapeutic effects of every single PDGF in ACL reconstruction surgery, when these separate entities are commercially available.

Back to Article Outline

References 

  1. Nin J, Gasque G, Azcarate A, et al. Has platelet-rich plasma any role in anterior cruciate ligament allograft healing?. Arthroscopy. 2009;25:1206–1213
  2. Radice F, Yanez R, Gutierrez V, et al. Comparison of magnetic resonance imaging findings in anterior cruciate ligament grafts with and without autologous platelet-derived growth factors. Arthroscopy. 2010;26:50–57
  3. Orrego M, Larrain C, Rosales J, et al. Effects of platelet concentrate and a bone plug on the healing of hamstring tendons in a bone tunnel. Arthroscopy. 2008;24:1373–1380
  4. Vogrin M, Rozman P, Haspl M. Concerns about the effects of platelet concentrate. Arthroscopy. 2009;25:941–942(letter)
  5. Alsousou J, Thompson M, Hulley P, Noble A, Willet K. The biology of platelet-rich plasma and its applications in trauma and orthopaedic surgery. J Bone Joint Surg Br. 2009;91:987–996
  6. Sanchez AR, Sheridan PJ, Kupp LI. Is platelet-rich plasma the perfect enhancement factor? (A current review). Int J Oral Maxillofac Implants. 2003;18:93–103
  7. Schliephake H. Bone growth factors in maxillofacial reconstruction. Int J Oral Maxillofac Surg. 2002;31:496-484
  8. Weibrich G, Kleis WKG, Hafner G, Hitzler WE. Growth factors levels in platelet-rich plasma and correlations with donor age, sex, and platelet count. J Craniomaxillofac Surg. 2002;30:97–102

PII: S0749-8063(10)00627-4

doi:10.1016/j.arthro.2010.06.019

Refers to article:

  • Growth Factor Confusion

    Joshua S. Dines
    Arthroscopy: The Journal of Arthroscopic and Related Surgery September 2010 (Vol. 26, Issue 9, Page 1144)

Arthroscopy: The Journal of Arthroscopic and Related Surgery
Volume 26, Issue 9 , Pages 1145-1146, September 2010

Article Tools