Tissue Regeneration in Humans

Introduction

In the field of biology, regeneration is the progression of renewal, regeneration and growth that makes it possible for genomes, cells, organs, organisms resilient to natural changes or events that cause damage or disturbance. Regeneration is mediated by the molecular processes of DNA synthesis. Every species is capable of regeneration, from simplest organisms such as bacteria to as complex as humans. However, regeneration in biology mainly means the morphogenic processes that differentiate the phenotypic plasticity of traits allowing multi-cellular organisms to repair and maintain the stability of physiological and morphological states. [1]

Tissue regeneration is the process of renewal and growth of tissues and it is mainly common in limb development in organisms. Tissue engineering, the use of a combination of cells, engineering and materials methods, and biochemical and physio-chemical factors to replace or improve biological functions, is a growing field of research in today’s scientific world. Tissue regeneration is an important field in understanding the development of an organism because it can help us to look at the critical factors that influence the development of limbs and organs of an individual in this case humans and primates. [1]

Protein Critical for Tissue Regeneration Discovered

A flatworm well-known for its unique ability to regenerate cells is giving scientists at the University of California, more light on how cancer could be treated and how regenerative medicine could better target diseases. [2]

It has been shown that signaling by a protein called Target of Rapamycin (TOR) found in humans and most other mammals, is vital for planaria’s unique tissue regeneration. Disabling the protein stops the flatworm’s regeneration, showing that disabling it in abnormal cells could possibly prevent the growth of a cancer. [2]

Researchers have identified that the TOR protein plays a role in cancer, aging and degenerative diseases, but they haven’t found the answer to how it works. [2]

The planarian on the left is expressing the gene TOR. The planarian on the right is not, the result of a genetic manipulations that disrupts gene expression

Methods

One lab is approaching this question using tiny flatworms known as planaria. The planarian is now among the species that could be crucial in understanding the role of stem cells due to its ability to repair itself, and its secrets could help combat cancer and degenerative diseases. [2]

For this study, the researchers disabled the TOR protein in planaria and then amputated parts of the flatworm. Under typical circumstances, the organism would be able to repair itself. [2]

Results

Researchers discovered the planaria’s stem cells recognized they needed to regenerate tissue but were unable to do so in the correct place and instead formed tissues in abnormal places. This kind of regeneration hasn’t been observed before. Furthermore, the planaria with the disabled protein were unable to grow, even if nutrients were available. [2]

Conclusion

In addition to stopping cancer, understanding TOR and its role in regulation could direct to the development of medicines to encourage tissue regeneration and to fight degenerative diseases, such as Alzheimer’s. [2]

Strengths and Weaknesses of this study

Understanding the role of the TOR protein could lead to the development of medicines against cancer and other regenerative diseases, however, researchers have not figured out how this protein works which is a weakness of this study.

Watch the following video to explore more about the current research on tissue regeneration


New method for engineering human tissue regeneration

If proven successful, pending clinical trials in Yale University represent a significant scientific leap toward human tissue regeneration and engineering. In a recent research report, Yale scientists provide evidence to support a huge paradigm shift in the area of human tissue regeneration from the idea that cells added to a graft before implantation are the building blocks of tissue, to a novel belief that engineered tissue constructs can actually induce or increase the body’s own reparative mechanisms, including complex tissue regeneration. [3]

  • Methods

Breuer and his colleagues in this study conducted a three-part study, starting with two groups of mice. The first group expressed a gene that made all of its cells fluorescent green and the second group was normal. Next, Researchers extracted bone marrow cells from the “green” mice, added them to formerly designed scaffolds, and implanted the grafts into the normal mice. [3]

  • Results

The seeded bone marrow cells enhanced the performance of the graft; however, a rapid loss of green cells was observed and the cells that developed in the new vessel wall were not green which suggests that the seeded cells promoted vessel development, but did not turn into vessel wall cells themselves. Thus, these findings directed to the second part of the study, which tested whether cells produced in the host’s bone marrow might be a possible source for new cells. [3]

Second study

Researchers replaced the bone marrow cells of a female mouse with those of a male mouse before implanting the graft into female mice. They found that the cells forming the new vessel were female, meaning they did not come from the male bone marrow cells. [3]

Third study

Researchers implanted a segment of male vessel attached to the scaffold into a female host. In result, researchers found that the side of the graft next to the male segment developed with male vessel wall cells while the side of the graft attached to the female host’s vessel formed from female cells, meaning that the cells in the new vessel must have migrated from the adjacent normal vessel. [3]

Silk scaffolds can be used to produce tissue engineered bone. The figure illustrates the generation of tissue engineered bone using silk scaffolds.


Advancement in Tissue Engineering Promotes Oral Wound Healing

Oral tissue engineering for transplantation to help wound healing in the oral cavity reconstruction has taken a considerable step forward. According to the study’s lead author, Dr. Susan Gibbs of the VU University Medical Centre in Amsterdam, skin substitutes have been far more advanced than oral gingiva substitutes. Until now, no oral tissue-engineered products have been available for clinical applications. This study was aimed at constructing full thickness oral substitutes while maintaining the needed characteristics for successful oral transplantation. Researchers used small amounts of patient oral tissue acquired from biopsies, the cultured and expanded the tissues in vitro over a three-week period. [4]

Results of this study showed with a few number of patients showed that the gingiva substitute was promising and supported the need to carry out a larger patient study in the future. [4]

Click here to read about how the study of Newts can help scientists find a new way of tissue regeneration in humans

Watch the following video to learn about tissue engineering and the new advancements

Sources-

1. Sánchez, A. A. (2000). “Regeneration in the metazoans: why does it happen?”. Bioessays 22 (6): 578–590.doi:10.1002/(SICI)1521-1878(200006)22:6<578::AID-BIES11>3.0.CO;2-#. PMID 10842312

2. University of California, Merced (2012, March 20). Protein critical for tissue regeneration discovered. ScienceDaily. Retrieved April 26, 2012, from http://www.sciencedaily.com­/releases/2012/03/120320161318.htm

3. Narutoshi Hibino, Gustavo Villalona, Nicholas Pietris, Daniel R. Duncan, Adam Schoffner, Jason D. Roh, Tai Yi, Lawrence W. Dobrucki, Dane Mejias, Rajendra Sawh-Martinez, Jamie K. Harrington, Albert Sinusas, Diane S. Krause, Themis Kyriakides, W. Mark Saltzman, Jordan S. Pober, Toshiharu Shin’oka, Christopher K. Breuer. Tissue-engineered vascular grafts form neovessels that arise from regeneration of the adjacent blood vessel.FASEB Journal, 2011; DOI: 10.1096/fj.11-182246

4. Cell Transplantation (2009, February 3). Advancement In Tissue Engineering Promotes Oral Wound Healing. ScienceDaily. Retrieved March 11, 2012, fromhttp://www.sciencedaily.com­/releases/2009/02/090203080725.htm


2 Responses to Tissue Regeneration in Humans

  1. Jay says:

    Yes this is the holy grail of life and life is all we have there is nothing else for us. So coming forward with this regenerative research is ultra and totally paramount. Bring it on yesterday.

  2. Pingback: Human Regeneration- To Be Whole Again | Deakin SciComm

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