Scientists grow for the first time miniature human oesophagus in lab

Context:

• Scientists for the first time have successfully grown oesophageal organoids - a miniature, functional versions of human food pipe using pluripotent stem cells (PSCs) in laboratory.
• The human oesophageal tissue was grown entirely from pluripotent stem cells (PSCs), which can form any tissue type in the body.

About:

Oesophagus: The Food Channel

• Oesophagus is a long muscular tube part of digestive system that connects mouth to stomach to actively pass food.
• It is also called as gastro-intestinal tract (gullet or food pipe). It is around 25cm long in adults.
• There are a number of lymph nodes close to the oesophagus.
• After food is swallowed, walls of oesophagus squeeze together (contract) and moves food down to the stomach. The area where oesophagus joins stomach is called gastro-oesophageal junction.

Oesophagus has four layers:

• Mucosa – inner layer, which is moist to help food pass smoothly into stomach.
• Submucosa –Contains glands that produce mucus (phlegm), which keeps oesophagus moist.
• Muscularis – It is muscle layer, which pushes food down to stomach.
• Adventitia – It is outer layer, which attaches oesophagus to nearby parts of the body.

Disease Associated

• Oesophagus can be affected by congenital diseases, such as oesophageal atresia, a medical condition causing narrowing or malformation of oesophagus due to genetic mutations.
• Other diseases related to it includes oesophageal cancer, gastro-oesophageal reflux disease (GERD), or rare ailment called achalasia - a disease affecting muscles of lower oesophagus that prevents contraction of organ and passage of food.

Process

• After successfully generating fully formed human oesophageal organoids - which grew to a length of about 300-800 micrometers in about two months - the bioengineered tissues were compared biochemically to oesophageal tissues from patient biopsies. The tests showed the bioengineered and biopsies tissues were strikingly similar in composition.
• The research team is continuing its studies into the bioengineering process for oesophageal organoids and identifying future projects to advance the technology's eventual therapeutic potential.
• This includes using the organoids to examine the progression of specific diseases and congenital defects affecting the oesophagus.

Background:

Stem cell

• Stem cell is undifferentiated cell of multicellular organism which is capable of giving rise to indefinitely more cells (through mitosis) of same type and from which certain other kinds of cell may be formed by the cellular differentiation. Stem cells differ from other kinds of cells in the body.
• They have the remarkable potential to develop into cell types in the body during early life and growth.
• Stem Cells have three unique properties:

1. They are capable of dividing and renewing themselves for long periods;
2. They are unspecialized; and
3. They can give rise to specialized cell types.

• Commonly, stem cells come from two main sources:
  a. Embryonic stem cells: They come from human embryos that are three to five days old. They are harvested during process called in-vitro fertilization. They are known as pluripotent stem cells. These cells can give rise to virtually any other type of cell in the body.
  b. Adult stem cells: Exist throughout the body after embryonic development and are found inside of different types of tissue such as the brain, bone marrow, blood, blood vessels, skeletal muscles etc.
• The capacity to differentiate into specialized cell types and be able to give rise to any mature cell type is referred to as potency.
• Totipotent stem cells can differentiate into embryonic and extra embryonic cell types. These cells are produced from the fusion of an egg and sperm cell and can construct a complete, viable organism.The only totipotent cells are the fertilized egg and the cells produced by the first few divisions of the fertilized egg are also totipotent.
• Induced pluripotent stem cells (iPSCs): They are the descendants of totipotent cells and can differentiate into nearly all types of specialized cells in body. They can potentially produce new cells for any organ or tissue. These are true stem cells, with the potential to make any differentiated cell in the body. Embryonic Stem Cells come under this category.
• Multipotent stem cells can differentiate into a number of cells, but only those of a closely related family of cells (i.e) it can only differentiate into a limited number of types. For example, the bone marrow contains multi-potent stem cells that give rise to all the cells of the blood but not to other types of cells.
• Oligopotent stem cells can differentiate into only a few cells, such as lymphoid or myeloid stem cells.
• Unipotent cells can produce only one cell type, their own, but have the property of self-renewal, which distinguishes them from non-stem cells. Such unipotent cells include muscle stem cells.

Significance:

This bioengineered oesophageal organoids paves way for new ways to study and test drugs against gut disorders.

The research may lead to personalised diagnostic methods as it is focused on developing regenerative tissue therapies to treat or cure GI disorders.

It will also help to study birth defects like oesophageal atresia, organoids, eosinophilic esophagitis and Barrett’s metaplasia. Moreover bioengineer genetically matched oesophageal tissue can be also transplanted in individual patients.

All of the above mentioned conditions need better treatments. This requires a more precise understanding of the genetic and biochemical mechanisms behind their cause -- a need filled by the ability to generate and study robust, functional, genetically matched models of human oesophageal tissue that can be grown from a person's own cells.

Practice question

1. What are organoids? Discuss briefly how they are created in lab setting? Also, discuss what are their applications.

2. Stem cell therapy is gaining popularity in India to treat a wide variety of medical conditions including leukaemia, Thallessemia, damaged sornea and several burns. Describe briefly what stem cell therapy is and what advantages it has over other treatments? (UPSC 2017).