In the 1990s, Laura Niklason observed a troubling reality during her residency at Massachusetts General Hospital in Boston. Patients undergoing cardiac bypass surgery often required new blood vessels, and surgeons typically resorted to harvesting veins or arteries from other parts of the body—most commonly the legs. This process not only caused additional pain but also presented risks associated with healing and infection at multiple sites. Niklason was struck by the absence of a viable alternative and envisioned a future where replacement blood vessels could be grown on demand.

At the time, the concept seemed far-fetched, as no such solution existed. Yet, the vessel-harvesting procedure continued to be a necessary part of surgeries for various conditions, especially for cardiac and dialysis patients. Existing synthetic arteries, made from materials resembling Teflon, often led to complications like infections and immune responses, necessitating repeated surgical interventions. Niklason recognized that lab-grown organs, crafted from human cells, could significantly enhance the outcomes of over 500,000 vascular replacement surgeries annually, representing a substantial market worth hundreds of millions.

Despite facing significant technological challenges and skepticism from the scientific community, Niklason pressed on. Eventually, her pioneering living tubes began to be implanted in human patients. In the mid-1990s, she shared her aspirations with her mentor, Charles Vacanti, who had gained notoriety for his work on growing organs, including a human-shaped ear in a mouse. Vacanti connected her with Robert Langer, a renowned tissue engineer at MIT, and Niklason joined his lab as a postdoctoral researcher.

In Langer's lab, Niklason embarked on a pioneering project that few had previously attempted. Understanding that blood vessel cells are constantly influenced by the mechanical forces of blood flow, she sought to replicate these conditions in the lab to ensure the growth of robust, flexible tubes capable of thriving in the human body. While many biologists focused solely on chemical stimuli to encourage cell growth, Niklason aimed to integrate physical forces into the process.

The prevailing approach in tissue engineering relied heavily on finding the right chemical formulations to coax cells into forming tissues. However, Niklason understood that to create a functional blood vessel, cells also needed to build an external matrix that provided structure and support. This understanding led her to explore the natural physical environment of cells, reasoning that the evolutionary pressures faced by cells throughout history shaped their ability to thrive under specific mechanical conditions.

Had it not been for a network of visionary bioengineers around her, Niklason's groundbreaking ideas could have easily been overlooked. Other forward-thinking researchers, like Don Ingber, were also challenging established norms. Ingber proposed the theory of "tensegrity," suggesting that the mechanical forces acting on cells influence gene expression, a concept that initially faced skepticism.

While Ingber highlighted the significance of mechanics in cellular behavior, Langer was busy establishing one of the leading tissue engineering labs at MIT. This collaborative environment fostered Niklason's unconventional approach, which was not yet widely accepted. Despite the lack of a clear blueprint for her ambitious project, Niklason was determined to mimic the heart's pulsatile action in her laboratory experiments.

With a combination of tenacity and creativity, she developed a bio-incubator that successfully replicated the conditions necessary for blood vessel growth. By using cells from cow blood vessels and employing a biodegradable scaffold, she created a system where the cells could thrive. The pulsing mechanism imitated the heart's rhythm, prompting the cells to produce essential components like collagen and elastin, ultimately forming a functional lab-grown blood vessel.

In 1999, Niklason and Langer published their groundbreaking findings in Science, marking a significant milestone in the field. However, the ultimate challenge remained: implanting these vessels into human patients, which posed substantial risks.

Relocating to North Carolina, Niklason continued her research as an assistant professor at Duke University. In 2004, she co-founded Humacyte with her Ph.D. student and a former postdoctoral researcher, aiming to commercialize lab-grown veins. Initially, she intended to use patients' own cells for vessel creation, but complications arose due to the compromised condition of their cells. Instead, they sourced healthy cells from organ donors, later removing them after constructing a protein scaffold, a decision that felt counterintuitive but was necessary.

As research progressed, the bio-incubator was refined to ensure it accurately mimicked the pressures experienced in the human body. While some animals rejected the implants, trials in primates showed promising results. The vessels were designed to be "stealth tissues," tricking the body into accepting them as its own, with evidence suggesting that the patient’s own cells eventually integrated with the implanted tissue.

This year, clinical trials commenced in Poland and the United States, assessing the safety of Niklason's innovative blood vessels. The next phases will evaluate their effectiveness against existing treatment methods.

Other bioengineers have also made strides in similar areas. Simon Hoerstrup developed tiny vessels for infants, while Paolo Macchiarini created artificial tracheas, advancing the field of regenerative medicine. Ingber’s insights, once dismissed, have gained recognition in the scientific community, culminating in the establishment of the Wyss Institute at Harvard, celebrated for its groundbreaking organ-on-a-chip technology.

While the path toward creating complex organs remains long and challenging, advances in simpler structures are promising. The recent interest in 3D printing may eventually lead to the fabrication of functional organs, but incorporating mechanical stresses, as Niklason has pioneered, will be critical for success.

If her vessels prove effective in trials, they could revolutionize care for cardiac and dialysis patients in the near future. After two decades of dedicated research, Niklason has begun to replicate the complex environments where our cells and organs have evolved.

Cynthia Graber is an award-winning print and radio reporter based in Somerville, Mass.

Originally published at Nautilus on April 17, 2014.