Pig tissue could provide solution for heart damage

The human immune system does not reject transplanted organs based on pig cells.

By JUDY SIEGEL-ITZKOVICH
PROF. MARCELLE MACHLUF 370 (photo credit: Courtesy Technion)
PROF. MARCELLE MACHLUF 370
(photo credit: Courtesy Technion)
Although it doesn’t sound very kosher, scientists at Haifa’s Technion-Israel Institute of Technology have used pig tissue to create a thick “scaffold” for heart muscle that supports human stem cells, preserves the infrastructure of natural blood vessels and are made from extracellular matrix proteins.
Prof. Marcelle Machluf of the biotechnology and food engineering faculty and her lab colleagues did the research, which has just been published in the journal Tissue Engineering.
The work was financed by the Office of the Chief Scientist of the Ministry of Industry and Trade and was conducted in cooperation with Singapore’s research agency.
Heart attacks (myocardial infarctions) are one of the leading causes of death and disability in the Western world. When they strike, the blood supply to the myocardium (the middle of the three layers forming the wall of the heart) is impaired and, as a result, a scar is formed in the affected area. Not only does this scar not help pump the blood through the body, but it also significantly burdens the healthy parts of the heart, which are now left to handle the required load by themselves.
Current clinical treatment focuses on drugs and/or surgery to improve heart function after the infarction and prevent a recurrence. This treatment, however, is not able to rehabilitate damaged scar tissue. Thus, the only solutions for end-stage heart patients are heart transplantation or the use of ventricularassist devices to keep the heart pumping.
These two options are highly limited, both in terms of supply and cost, and this creates a significant gap between the number of people who need treatment and those who receive it. This gap has led to extensive tissue engineering and cell therapy research, aiming to develop alternatives for rehabilitating and regenerating the damaged tissue.
In recent years, several engineered tissue substitutes were developed to rehabilitate heart function, mainly in animal models. These substitutes are based on cells and/or a supportive scaffold comprising biomaterials. Such an ideal engineered system should, at the cellular level, have cells occupying the vascular system to nourish the heart tissue; myocardial cells are the most critical. Unfortunately, despite substantial investment in cell research, mature and beating myocardial cells still cannot be reproduced in the lab, so production of large amounts of cells is impossible.
Thus effort is being invested in developing scaffolds or platforms for the patients’ damaged tissue and healthy transplanted cells. These scaffolds should have biomechanical properties that are compatible with those of the myocardium, support the cells and the rehabilitating tissue while providing the required biochemical signals and break down as the natural extracellular matrix is secreted.
One of the materials considered most suitable for creating such a scaffold is the natural extracellular matrix, which maintains and supports the cells in the healthy tissue.
According to recent publications, matrices such as these have been produced from several tissues; one such matrix was produced by Machluf from pig heart tissue, which is physiologically similar to the human heart.
Because it is natural and has a protein composition that is 98 percent identical in pigs and humans, the human immune system does not reject transplanted organs based on pig cells.
Machluf’s work focuses on a matrix that is as clean as possible from cellular components that could provoke immunological rejection, while retaining its inherent vasculature.
These new scaffolds, when seeded in the appropriate cells, could serve as laboratory platforms that mimic the myocardium for research purposes, as models for the extracellular matrix in humans, and as implants for treatment of heart attacks,the Technion scientist said.