Australian Science Illustrated – Issue 51 2017

38 | SCIENCE ILLUSTRATED

A cross section of the four-week-old embryo heart

shows that the heart is made up of both pig cells

(blue) and human cells (green).

Gene-spliced Pig

Will Grow a Copy

of Your Heart

In a ground-breaking experiment, scientists have managed

to include cells from a human in the heart of a pig embryo.

The next step will be growing an entire heart, which is only

made up of cells from the patient who needs the heart.

1

A fertilised egg cell from a

pig loses a gene, which is

normally crucial to the pig

developing its own heart. The

editing is carried out using the

new CRISPR-Cas9 tool.

2

Skin cells from the patient,

who needs a new heart, are

re-programmed into stem

cells using substances, which change

the expression of the cells' genes.

3

When the egg cell from the

pig has developed into an

early embryo without any

organs, the patient's stem cells are

injected into the embryo.

STEM CELLS

ARE INJECTED.

CELLS FROM A

HUMAN BEING

EGG CELL

SKIN CELLS

SKIN CELLS CONVERTED INTO

STEM CELLS

EARLY PIG EMBRYO

F

our weeks have passed since the

pig embryos were implanted, and

the air is heavy with excitement

in the American lab. The

scientists are so close to

completing their breakthrough project that

they can almost taste the sensation. Finally,

the fragile pig embryos have been removed

from their surrogate mothers and placed

under the microscopes. The hopeful

scientists are only looking for one thing in the

tiny embryos: human cells.

Biologist Juan Carlos Belmonte and his

team of scientists from the Salk Institute in La

Jolla, California, are the first to have produced

cross-breeds between pigs and humans.

Human stem cells were injected into pig

embryos, before the embryos were inserted

into the wombs of adult pigs. Four weeks later,

the human cells had become integral parts of

the growing pig embryos. Scientists now aim

to combine the method with sophisticated

gene technology to grow human organs in pigs

and reduce the short-age of donor organs.

FORCED TO MAKE ODD EXPERIMENTS

There is a critical shortage of donor organs

throughout the world. Waiting lists have

sextupled during the past few decades, and

about 60 % of the patients who are waiting

for a new organ die as they do so. Scientists

have struggled to find a solution for decades.

In the 1960s, 13 desperate patients had

chimp kidneys implanted, and though only

one single patient survived for more than a

few months, the experiments promised that

the method might work one day.

Later, different organs from monkeys and

pigs were transplanted into humans with

limited success. The major challenge is the

FROM HUMAN

FROM PIG

SALK INSTITUTE

GENE EDITING

TOOL INJECTED

HUMANS ORGANS