Printers Aren’t Just For Homework Anymore: The Science and Ethics of Bioprinting

What do you get when you combine the technology of inkjet printers, digital modeling, and 3-D manufacturing?  Right.  3-D printers. 

Okay, that was easy.  Now add living tissues to the mix. 

Very funny.  But no… not an Obama bobble head with human hair.

The real answer?  Three-dimensional cellular construction, also known as 3-D bioprinting.

Standard 3-D printers have been around since the 1980s.  Guided by a three-dimensional computer image, the printer-head lays down successive layers of a material such as plastic in the form of an image, say, the Eifel Tower.  The outcome is a precisely-fashioned plastic model of the thing imaged. 

In the last ten years, the technology has become quite common in fields such as dental, automotive and aerospace engineering, architecture, as well as in the design of footwear, jewelry, eyewear, etc.

Printing Human Tissues

Scientists in the field of regenerative medicine conceived the idea of using 3-D printing technology to produce—to print—human tissues and organs.  Rather than layers of plastic, bioprinters set down layer upon layer of biomaterials such as living cells, which are built up into three-dimensional structures.  The technology is at various stages of development, most still at the research phase.

What’s “the ink”?  Most techniques use induced Pluripotent Stem (iPS) cells, the revolutionary technology that we’ve covered in these pages several times over the last few years.  The iPS cells are usually derived from healthy tissue samples taken from would-be transplant recipients.

One example of the new technique is skin printing, which researchers hope will improve graft treatments for burn victims.  It involves printing sheets of iPS cells derived from healthy skin samples from burn victims.  The cells grow and differentiate into the different layers of skin and then can be transplanted.  In some cases, the skin cells are printed directly onto a victim’s wound.

At Cornell University, experimental heart valves and knee cartilage have been printed; at Wake Forest, functional kidney cells; and at the University of Missouri-Columbia, sheets of beating heart muscle.

Bio-scaffolding

Even more innovative is the technique of bio-scaffolding to create larger organs, for example, new bones for bone replacement surgery.  A digital image of a segment of bone is developed from a bone injury patient.  From that image, a three-dimensional bone scaffold identical to the segment is “printed out” using artificial materials.  The scaffold is then coated with stem cells derived from the patient’s own body.  The printed bone structure is then transferred into the patient, where, over time, the artificial scaffold harmlessly degrades, leaving behind new bone grown from the patient’s own stem cells.

Scaffolding technology has already been used to create replacement tracheas, blood vessels and bladders for use in surgical transplants (watch this interesting video). Researchers at the University of Louisville predict that within ten years, bioprinting will be used to create fully-functioning “bioficial” human hearts.

Ethical Considerations

What ethical questions are raised by the new technology?  The first concerns the sources of stem cells used in a given technique.  Although most bioprinting protocols use iPS cells, not all do.  Some use adult stem cells, which are morally legitimate.  But others use stem cells derived from destroying human embryos.  This is the case, for example, with research at Heriot-Watt University in Edinburgh, Scotland, where researchers have developed a bioprinter that uses human embryonic stem cells as its “ink.” 

Safety concerns are also important to consider.  The urgent need for transplantable organs mustn’t move us to cut corners in clinical safety trials with this new generation of “bioficial” products.

We also have reasons to be concerned about researchers stretching towards unethical boundaries; for example, if they were to begin coveting the forbidden fruit of producing whole brains for purposes of transplanting them into humans. 

I do not mean to stigmatize research into the repair and regeneration of damaged neurological tissue.  I have family members with Alzheimer’s disease and would welcome (they would welcome!) therapeutic treatment options for overcoming the crippling condition. 

But whole brain transplants?  Even if they were ever possible utilizing brain matter derived from one’s own stem cells, which is doubtful, they would so impact a person’s personality and conscious identity (loss of memory, character, psychological development, brain-body history) that in all but the most narrow of circumstances I don’t see how they could be ethically licit.  (Perhaps in fetuses with severe traumatic brain injury; but only perhaps.)
 
Not all agree.  Just last week, the Promethian juices of scientists were stimulated when the journal Nature announced that “mini-brains” had been produced in vitro for the first time. 

Austrian researchers grew stem cells upon a gel that resembled some of the brain’s natural connective tissues.  The cells developed into neural tissue clumps that when infused with nutrients and oxygen began to interact in ways characteristic of fetal brains in the early weeks of human development. 

One enthusiastic scientist interviewed for the article (and not involved in the study) proclaimed: “It’s a seminal study to making a brain in a dish!”  But, he continued, a “fully formed artificial brain might still be years away.”  Phew!  I guess we don’t need to worry.

Defend Our Ethical Boundaries

This new technology, especially the scaffolding method, puts us in reach within a decade of the elusive goal of achieving a surplus of transplantable organs for those who need them.  And it seems that the goal can be achieved through morally licit forms of research. 

This is unbelievable.

Ten years ago scientists were arguing that this was only possible if we “relaxed” our morality: “give us embryos,” they cried, “otherwise people will die;” or if not embryos, then at least suspend the “dead-donor rule” for vital organ donation. 

The amoralists were proven wrong; iPS cell research and adult stem cell research now dominate the field of regenerative medicine. 

But the amoralists haven’t gone away.  Even in the face of the staggering failure of embryonic stem cell research, they’re still clamoring for human embryos, though not as loudly.  And more and more are advocating for the abandonment of the dead-donor rule in transplant medicine.

We mustn’t lose hope that reason will prevail over lust in the field of regenerative medicine.  Where scientific genius is guided by good morals, remarkably good things can happen.  Shinya Yamanaka’s breakthrough with iPS cells in 2007 is merely the most recent example.