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EDITORIAL Table of Contents   
Year : 2005  |  Volume : 39  |  Issue : 2  |  Page : 73-74
Stem cells in Orthopaedics


Professor of Orthopaedics, Institute of Medical Sciences, BHU, Varanasi, India

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How to cite this article:
Goel S C. Stem cells in Orthopaedics. Indian J Orthop 2005;39:73-4

How to cite this URL:
Goel S C. Stem cells in Orthopaedics. Indian J Orthop [serial online] 2005 [cited 2019 Jul 18];39:73-4. Available from: http://www.ijoonline.com/text.asp?2005/39/2/73/36774
Recently there has been wide interest in stem cell research. It has also been highly controversial. Stem cells are unspecialized cells that can self-renew indefinitely and that can also differentiate into more mature cells with specialized functions. In humans, stem cells have been identified in the inner cell mass of the early embryo; in some tissues of the fetus, the umbilical cord and placenta; and in several adult organs. In some adult organs, stem cells can give rise to more than one specialized cell type within that organ (for example, neural stem cells give rise to three cell types found in the brain- neurons, glial cells, and astrocytes). When a stem cell is found to give rise to multiple tissue types associated with different organs, the stem cell is referred to as multipotent. The word "pluripotent" is sometimes used to describe stem cells that can differentiate into a very wide range of tissue types.

Both adult and embryonic stem cells can contribute to the development of regenerative medicine. [1] Embryonic stem cells (ESCs) have the advantage of multipotency and have shown themselves to be readily culturable in the laboratory. Although the degree of plasticity of adult stem cells is still unknown and there are difficulties in purifying and culturing them, the only proven stem cell-based medical therapies that are currently available rely on adult-derived stem cells from bone marrow and skin. Adult stem cells from other tissues might someday provide therapies that stimulate the body's own regenerative potential. Stem cells are rare and difficult to isolate, and very few stem cell types have been confirmed to exist in adult human tissues. Much of the work that is used to support the argument that adult stem cells can substitute for embryonic stem cells was done only in mice or other animal models, which may not be applicable to humans. Because of a misunderstanding of the current state of knowledge, there may be an impression that widespread clinical application of new therapies is certain and imminent. In fact, stem cell research is in its infancy, and there are considerable gaps in knowledge about new therapies from either adult or embryo derived stem cells.

Bone formation in the embryo, during adult fracture repair and remodeling, involves the progeny of a small number of cells called mesenchymal stem cells. These cells continuously replicate themselves, while a portion becomes committed to mesenchymal cell lineages such as bone, cartilage, tendon, ligament and muscle. The differentiation of these cells is a complex multistep pathway involving discrete cellular transitions. Progress from one stage to the next depends on the presence of specific bioactive factors, nutrients, and other environmental cues whose exquisitely controlled conditions orchestrate the entire differentiation events. As for the inducing agents, it has reported that MSCs readily differentiate into colonies of osteoblasts, chondrocytes and adipocytes in responsible to dexamethasone, 1,25 dihydroxyvitamine D3, osteogenin, osteogenic growth peptide, or cytokines such as BMPs. MSCs possess osteogenic potential and have extensive prospect in treatment of bone diseases.

Adult stem cells, such as blood-forming stem cells in bone marrow (called hematopoietic stem cells, or HSCs), are currently the only type of stem cell commonly used to treat human diseases. More advanced techniques of collecting, or "harvesting," HSCs are now used in order to treat leukemia, lymphoma and several inherited blood disorders. The clinical potential of adult stem cells has also been shown in the treatment of other human diseases that include diabetes and advanced kidney cancer. However, these newer uses have involved studies with a very limited number of patients. Under appropriate induction conditions, these cells can differentiate into bone, cartilage, and fat. Umbilical cord blood does contain mesenchymal stem cells and should not be regarded as medical waste. It can serve as an alternative source of mesenchymal stem cells to bone marrow. [2]

Ideal skeletal reconstruction depends on regeneration of normal tissues that result from initiation of progenitor cell activity. However, knowledge of the origins and phenotypic characteristics of these progenitors and the controlling factors that govern bone formation and remodeling to give a functional skeleton adequate for physiological needs is limited. Practical methods are currently being investigated to amplify in in-vitro culture the appropriate autologous cells to aid skeletal healing and reconstruction. Recent advances in the fields of biomaterials, biomimetics, and tissue engineering have focused attention on the potentials for clinical application. Current cell therapy procedures include the use of tissue-cultured skin cells for treatment of burns and ulcers, and in orthopedics, the use of cultured cartilage cells for articular defects.

The repair of a fracture necessarily entails synthesis of osseous tissue requiring the transformation of undifferentiated osteochondral progenitor cells to mature osteoblasts and chondrocytes. There are stem cells for all mesenchymal tissues, resident in bone marrow throughout life, that have a lineage comparable to that described for hematopoiesis. Marrow derived and periosteal derived progenitor cells have been shown to produce bone and cartilage in numerous in vivo and in vitro studies. The differentiation process appears to depend heavily on the influences of numerous cytokines, especially the transforming growth factor beta superfamily. Initial cartilage formation from progenitor cells is important in any secondary fracture repair [3] .

Bone marrow-derived MSCs are susceptible to in vitro lipofectamine mediated TGF-beta 1 gene transfer. This can be used to modify the functional biology of articular tissue repair along defined pathways of growth and differentiation and to affect a better repair of full-thickness articular cartilage defects that occur as a result of injury and osteoarthritis [4] .

The potentials for using osteogenic stem cells in orthopedics for bone and cartilage defect healing is immense, and is likely to further expand significantly in the future.

 
   References Top

1.Commission on Life Sciences. Stem Cells and the Future of Regen­erative Medicine. E publication. 2002.  Back to cited text no. 1    
2.Lee OK, Kuo TK, Chen WM, Lee KD, Hsieh SL, Chen TH. Isolation of multipotent mesenchymal stem cells from umbilical cord blood. Blood. 2004 Mar 1;103(5):1669-75.  Back to cited text no. 2    
3.Yoo JU, Johnstone B. The role of osteochondral progenitor cells in fracture repair. Clin Orthop. 1998 Oct;(355 Suppl):S73-81.  Back to cited text no. 3    
4.Guo X, Du J, Zheng Q, Yang S, Liu Y, Duan D, Yi C. Expression of transforming growth factor beta 1 in mesenchymal stem cells: potential utility in molecular tissue engineering for osteochondral repair. J Huazhong Univ Sci Technolog Med Sci. 2002;22(2):112-5.  Back to cited text no. 4    

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Correspondence Address:
S C Goel
Professor of Orthopaedics, Institute of Medical Sciences, BHU, Varanasi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5413.36774

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