Nanopolymer Scaffolding for Cartilage Regrowth

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Researchers are exploring the functionality of nanopolymer scaffolds in cartilage regrowth. Cartilage is a flexible connective tissue that allows movement and reduces friction at joints. Current ailments leading to cartilage degeneration, such as osteoarthritis, have no treatment or cure [1]. Successful bone and skin regrowth with use of nanopolymer scaffolds, injectable structures that act as templates for cell regeneration, shows the promise of this nano application when applied to cartilage [2] [3].

            Structure and formation of nano-scaffoldings for cartilage can vary. Manufacturing of the scaffolds can be done with common nano-scale manufacturing methods, often electrospinning or molecular self-assembly [1]. The most common cartilage scaffolding designs created are porous sponges, non-woven fibrous structures and hydrogels made from a variety of natural (carbohydrate-based or protein-based) and synthetic polymers. Scaffolding composition factors important to scaffolding design include mechanical strength and biocompatability. Defining characteristics of the cartilage are determined based on whether the cartilage will be grown in a lab or in a patient’s body [4].

When growing new cartilage in the body, scaffolds can be injected at locations with missing or damaged cartilage. The porous or fibrous structure of the scaffold allows space for the cartilage to regrow [5]. In the case of traumatic damage, scaffolds provide the stem cells that heal the damaged site a template for growth. They work by releasing biomolecules from the scaffolds to encourage the stem cells to differentiate into cartilage cells [6]. Because the patient’s previously existing stem cells are being recruited in this method, there is minimal risk of biocompatibility issues. A challenge with the in-body approach is that the scaffold is limited in material choice and structure in order to avoid premature degradation in the presence of enzymes, typically restricted to hydrogels or polyester-based solid scaffolds. Hydrogels excel at providing a cell environment that closely mimics a normal extracellular matrix, but they lack in mechanical integrity. Polyester-based solid materials, on the other hand, better replicate the mechanical structures, but lack in the promotion of cell adhesion compared to hydrogels [5]. Limiting to only scaffold designs that are competent in vivo makes it difficult to produce connective tissue that reduces friction and allows movement as well as natural cartilage.

When growing cartilage in a lab, the design of the scaffold is more variable, allowing for more control of the quality of the cartilage generated. This is because the scaffold is not required to maintain the mechanical properties to withstand in-body stresses. Its only requirement is to provide a template for new cartilage to grow, which can be done in a less harsh environment. A down side to this method is that stem cells do not last as long outside of the body and an implant process to transfer the cartilage to the damaged site is required. If using stem cells that are not from the patient, biocompatibility must now be taken into consideration, adding additional risk  [5]

References

  1. Wieland HA, Michaelis M, Kirschbaum BJ, Rudolphi KA. Osteoarthritis — an untreatable disease?. Nature Reviews Drug Discovery [Internet]. 2005 ;4(4):331 - 344. Available from: http://www.nature.com/doifinder/10.1038/nrd1693
  2. Smith IO, Liu XH, Smith LA, Ma PX. Nanostructured polymer scaffolds for tissue engineering and regenerative medicine. Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology [Internet]. 2009 ;1(2):226 - 236. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2800311/
  3. PARMENTOLA JOHN, KYZER LINDY. OFFICE OF THE DEPUTY SECRETARY OF THE ARMY SUBJECT: ADVANCEMENTS IN ARMY SCIENCE AND TECHNOLOGY . [Internet]. 2008 . Available from: http://www.defense.gov/dodcmsshare/BloggerAssets/2008-11/11030815044420081103_Parmentola_transcript.pdf
  4. Citekey <a href="http://dx.doi.org/10.3390/jfb3040799">10.3390/jfb3040799</a> not found
  5. Citekey </span><a href="http://dx.doi.org/10.3390/jfb3040799">10.3390/jfb3040799</a><span> not found
  6. Citekey 645</span><span> not found

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Combats the structural damage of osteoarthritis and other causes of bone degeneration.

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Nanoscaffolding technology will potentially allow for cartilage regeneration and nonsurgical osteoarthritis treatment. Current cartilage healing treatments are rarely effective, even with surgery. Significant structural damage occurs in joints before the disease becomes symptomatic, and no current therapies fully combat the damage at that stage [1]. Scaffolding may work to fully repair the cartilage structure in faster, less invasive ways. Advances in scaffolding for cartilage may hold promise for exploration of organ regrowth, as well.

References

  1. Wieland HA, Michaelis M, Kirschbaum BJ, Rudolphi KA. Osteoarthritis — an untreatable disease?. Nature Reviews Drug Discovery [Internet]. 2005 ;4(4):331 - 344. Available from: http://www.nature.com/doifinder/10.1038/nrd1693

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One risk associated with this technology is immune rejection. However, using natural polymers reduces this risk, and is a common solution for current scaffolding technologies. If the tissue is grown outside of the body, a patient’s own cells are used as a starter, which also reduces risk of rejection. Many scaffolds are degraded by the body during use, and  minimize environmental threat. Degradation also poses little threat as the materials used are similar to natural biological materials and degrade fully. To date, scaffolds have been widely used and found to be safe.

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