The authors have shown that the filtrate bag contained large numbers of mesenchymal stem cells that could be processed without needing cell expansion. RIA therefore provided a one-stage procedure to procure stem cells for potential application to patients. No filtrate therefore should be discarded. They advocated using the concentrated stem cells together with the bone particles reamed (autografts) for the treatment of non-unions.
In the current practice of stem cell application for musculoskeletal surgery, adult stem cells are preferred to embryonic stem cells. The use of embryonic cells is surrounded by moral issues and also poses a risk of tumorigenesis.1 In contrast, the use of adult stem cells from RIA is relatively free from such a risk.
Sources of autologous adult stem cells include iliac crest bone marrow aspirate and fat cells.2,3 Stem cell transplantation from these sources requires a two stage procedure. In the first stage the marrow is aspirated for processing in the laboratory. The cells are isolated and then passaged several times to increase the number of cells to the required 2 to 4 million cells needed for clinical transplantation.4 Cells are usually used after two passages. This processing takes about two weeks to complete in the laboratory. The transplantation of cells can only be done in a second stage after the first stage produces the “cell pellet”. It is pertinent to note that the passaging of cells can lead to bizarre cell formation and apoptosis.5,6 Since fresh cells could be obtained from RIA without the need for cell expansion, these stem cells are less likely to develop bizarre cell formation and apoptosis – a distinct advantage of RIA.
Stem cell applications in musculoskeletal surgery include cartilage, bone and tendon regeneration. RIA is unlikely to be used as a source for cartilage regeneration since the bone particles or autologous bone grafts produced by the reaming could not be used in tendon surgery. Discarding the bone particles cannot be justified. For the same reason, RIA cannot be justified for procuring stem cells for tendon regeneration.
On the other hand, RIA could be useful for procuring bone particles and stem cells for bone regeneration whereby both the stem cells and the bone particles could be used. It is a useful surgical technique for the production of “tissue engineered bone substitutes”. The stem cells could be infiltrated into scaffolds such as hydroxyapatite blocks, tri-calcium phosphate, coral or polycaprolactone-tricalcium phosphate blocks7 to bridge large bone defects eg from nonunions, surgery for tumour reconstruction or congenital pseudoathrosis of the tibia. Whilst one cannot insert bone particles into the scaffold itself, the reamed bone autografts could be inserted into host-scaffold junctions to achieve better union. RIA would be particularly useful when using allograft-stem cells constructs for the reconstruction of large bone defects. Both stem cells and bone graft particles could be easily inserted into the medullary canal of the bone allografts to achieve better biological incorporation of the allograft. They could also be inserted into both host-allograft junctions to achieve union.8
RIA is particularly useful for bone applications such as the treatment of osteonecrosis of the hips,9,10 for impaction bone grafting in total hip replacement (Exeter Technique), for reconstruction of depressed articular fractures such as lateral condylar fractures of the tibia, calcaneal fractures and fractures of the distal radius11. In spinal surgery, it could be used to augment allografts by using autograft-allograft mixtures for posterior spinal fusion and for anterior spinal reconstruction using femoral cortical ring allografts following corpectomt.12 The addition of stem cells and bone particles from RIA could increase the fusion rate in posterior spinal fusion and incorporate the ring allografts better in anterior constructs. One could also explore infiltrating RIA cells and bone particles when performing kyphoplasty/ vertebroplasty procedures for osteoporotic wedge compression fractures of the spine. There are therefore several applications of RIA for bone. However careful preliminary research is needed to evaluate the effectiveness of these applications.
Whilst the authors have focused our attention on the presence of stem cells in the filtrate, they did not look into another useful component of the filtrate – namely the growth factors. In the production of Platelet Rich Plasma (PRP) about 20ml of peripheral blood “PRP Gel” is produced by centrifugation. The gel contains local growth factors including platelet derived growth factor and transforming growth factor (TGF).13 The latter includes bone morphogenetic proteins. In PRP production with centrifugation of peripheral blood, the junction of cells and serum – the “buffy coat” is the layer that is rich in growth factors. PRP gel is concentrated from this junction layer by a second spin. Likewise, in the centrifugation of the RIA filtrate, the junction between stem cells and serum could also be rich in growth factors. We could by a second spin similarly produce an “RIA PRP gel”. This would be another useful product that could be obtained from the filtrate in addition to the “cell pellet”. More research needs to be done to look into the number of growth factors that could be found in “RIA PRP gel” and also to evaluate their concentrations.
One can conclude that RIA is a good surgical technique that provides not only bone particles (autografts) but also “cells” and “growth factors”. However, much more research needs to be done on the two products that could be obtained from the RIA filtrate. Only then can the full potential of the usefulness of RIA technique be completely realised.
1. Bongso A., Lee EH. Stem cells: from Bench to Bedside. World Scientific Publishing, 2005: 1-13.
2. Pittenger MF, Mackay AM, Beck SC, et al. Multilineage potential of adult human mesenchymal stem cells. Science 1999;284:143-7.
3. Muschler GF, Midura RJ. Connective Tissue Progenitors: Practical Concepts for Clinical Applications. Clin Orthop 2002;395:66-80.
4. Nather A, Das De S, Lee CW. Culturing mesenchymal stem cells from bone marrow. In Nather A (ed). Bone Grafts and Bone Substitutes. World Scientific Publishing: New Jersey, London, Singapore. 2005:321-33.
5. Banfi A, Muraglia A, Dozin B, et al. Proliferation kinetics and differentiation potential of ex vivo expanded human bone marrow stromal cells: Implications for their use in cell therapy. Exp Hematol 2000;28:707-15.
6. Digirolamo CM, Stokes D, Colter D, et al. Propagation and senescence of human marrow stromal cells in culture: a simple colony-forming assay identifies samples with the greatest potential to propagate and differentiate. Br J Haematol 1999;107:275-81.
7. Nather A, Aziz S. Scaffolds in Bone Tissue Engineering. In Nather A (ed). Bone Grafts and Bone Substitutes. World Scientific Publishing: New Jersey, London, Singapore. 2005:357-66.
8. Nather A, David V, Teng JWH, Lee CW, Pereira BP. Effect of autologous mesenchymal stem cells on biological healing of allografts in critical-sized defects simulated in adult rabbits. Ann Acad Med 2010;39:599-606.
9. Gangji V, Hauzeur JP, Matos C, De Maetelaer V, Toungouz M, Lambermont M. Treatment of osteonecrosis of the femoral head with implantation of autologous bone marrow cells. A pilot study. J Bone Joint Surg [Am] 2004;86-A:1153-60.
10. Hauzeur JP, Gangji V. Phases 1-3 clinical trials using adult stem cells in osteonecrosis and nonunion fractures. Stem Cells Int 2010;26;2010:410170.
11. Nather A, Khalid KA, Aziz Z. Clinical applications of gamma-irradiated deep-frozen and lyophilized bone allografts – The NUH Tissue Bank experience. In Nather A, Yusof N, Hilmy N (eds). Radiation in Tissue Banking, World Scientific Publishing: New Jersey, London, Singapore. 2007. pp 305-315.
12. Nather A, Thambiah J. Allografts for Spinal Surgery. In Czitrom AA, Winkler H (eds). Orthopedic Allograft Surgery. Springer: Wien, New York. 1996:203-210.
13. Das De S, Manohara R, Nather A. Platelet-Rich Plasma in Orthopaedic Surgery: Basic Sciences and Clinical Applications. In Nather A (ed). Bone Grafts and Bone Substitutes. World Scientific Publishing: New Jersey, London, Singapore. 2005:387-403.
Associate Professor Aziz Nather
Chairman, National University Hospital Diabetic Foot Team
Department of Orthopaedic Surgery
National University Hospital
1E, NUHS Tower Block, Level 11