A video by anti-abortion activists of a Planned Parenthood official talking frankly about fetal organs has shed light on a world ordinarily kept from sight: the mounting demand for human tissue.

Researchers say pharmaceutical companies waste millions of dollars each year on failed drug development. Testing new medicine on human tissue, rather than just animal tissue, they say, boosts safety for people involved in clinical trials and yields faster results, which saves money. As a result, drugmakers will pay top dollar for different types of cells, tissue and organs that can be used to expedite their drug research.

The market is only growing, but the supply is limited. In the United States, most human tissue for research comes from donors after they die, provided there was informed consent from the individual or a family member. Some Planned Parenthood affiliates donate fetal organs to companies that extract cells and purify them for pharmaceutical firms.

One of those companies, Placerville, Calif.-based StemExpress, is mentioned in the anti-abortion video and calls itself in its marketing "the largest variety of raw materials available in the industry."

The company receives tissue directly from donors in addition to Planned Parenthood, a representative said, and extracts cells to purify them for researchers. The StemExpress catalog features a vial of two million "fresh" cells from a fetal liver for $1,932, and $1,840 for the same amount "cryopreserved," or frozen.

"We are proud of the role we play in helping the global research community as they strive to achieve medical breakthroughs to stamp out global disease and improve quality of life," the company said in a statement. "Everything we provide is solely at the request of the nation's and the world's great research institutions.”

The need for human tissue is "absolutely" growing, said Cate Dyer, the chief executive of StemExpress.

"Certain isolated cell types simply are better, if not best, for modeling how the human body will react to potential drugs," she said. "Scientific research and what it involves can be an uncomfortable topic for discussion, but it is vitally necessary if the research community is going to cure disease and improve quality of life.

On the secretly recorded video released this week by an anti-abortion group, Planned Parenthood official Deborah Nucatola, the organization’s senior director for medical services, spoke candidly about fetal organ donations in a way some people found callous. "I'd say a lot of people want liver," said Nucatola over lunch at a suburban Los Angeles restaurant, using a tone she employed moments earlier to discuss the antioxidants in red wine.

The footage touched off outrage among conservatives and 2016 presidential candidates who called the video horrifying.

On Thursday, Planned Parenthood president Cecile Richards apologized for Nucatola's word choice and thanked patients who choose to donate, an option she said will continue.

"Your commitment to lifesaving research, developing treatments for diseases like Parkinson's and Alzheimer's, is important and compassionate," said Planned Parenthood Richards earlier this week, "and it should be respected—not attacked."

The anti-abortion group Center for Medical Progress accused Planned Parenthood of selling the fetal tissue for profit. But never on camera does Nucatola discuss making money on the organs.

Rather, she describes costs associated with providing them  to biotech firms, like shipping and handling, which, she says, range from $30 to $100—far below the market price, researchers say.

Fetal tissue is often used in research on diseases and disorders that affect babies. Scientists use it to better understand fetal anatomy and how it may react to certain treatments. Liver is particularly helpful when assessing whether a medicine may be toxic.

"We wouldn't be where we are today in much of medicine without the use of human tissue," said Bill Leinweber, president of the National Disease Research Interchange, a non-profit that receives some government support to connect tissue to researchers around the world. "The important concept we strive to convey to folks is: Any donation of organ or tissue for research should be cherished as a gift."

Donations come exclusively from hospitals, organ procurement organizations, tissue banks or other regulated sterile medical settings. The supply, by nature, is finite and limited. Demand from researchers in both public and private institutions who seek to optimally prevent and cure an array of ailments is endless.

It's not easy to discuss, said Leinweber.

"Our society, at least in the U.S., generally finds conversations that pertain to decisions about what to do and what not to do when we die, very uncomfortable," he said. "Few of us like to consider—let alone plan for—our own mortality."

How does drug testing on human tissue even work? At Vertex Pharmaceuticals, which recently received approval from the Federal Drug Administration for a treatment for Cystic Fibrosis, scientists watched infected human lung tissue in nickel-sized petri dishes under a microscope. They injected these cells with potential new medicines and monitored the reactions, including how the cilia move following treatment. “We couldn’t have done that,” he said, “without human tissue.”

The National Institutes of Health spent $76 million on research using fetal tissue in 2014, records show, with plans to spend roughly the same amount this year and in 2016.

Nearly $1 million last year went to Trellis Bioscience, a private company, to fund work on medicine treating Cytomegalovirus, which causes enlarged spleens and seizures in newborns. About $875,000 funded HIV research at Massachusetts General Hospital and $386,000 funded work on neuro-developmental disorders at Stanford University.

Government money and tissue donation, of course, can’t reach everyone. Many researchers operating under a tight budget make it work partly by testing treatments on animal cells, which don't behave exactly like human cells—a process they say takes longer and ultimately can drive up the bill.

Biomedical entrepreneurs are harnessing this market. Over the last decade, a handful of private companies, whose founders say they’re adamant about following the law and universal ethical guidelines, have sprung up across the country to offer researchers a new source. TeVido Biodevices, which opened four years ago in Austin, Texas, uses stem cells and 3D printing to produce breast tissue with nipples. Seraph Robotics, a Cornell University spin-off also born in 2011, sells such printers to researchers who’d also like to spin cells into various types of tissue.

About 25 years ago, the National Institutes of Health Human Fetal Tissue Transplantation Research Panel declared abortion and fetal tissue use are "entirely separate issues," and that tissue use is ethically acceptable because it's morally insulated from the issue of abortion.

Providers, however, cannot legally change the way they perform an abortion in order to, say, preserve a fetal liver.

"The general consensus is that's unethical and unsafe," said Bill Murphy, co-Director of the Stem Cell and Regenerative Medicine Center at the University of Wisconsin. "That would be similar to the idea of organ donation. You can't modify a life saving procedure for a patient in order to harvest organs for transplant."

Last November, Organovo, a biomedical company in San Diego, started selling human liver tissue primarily to pharmaceutical companies. Today, nearly $2 million worth of orders are booked, said Michael Renard, the firm’s executive vice president.

In-house research, which typically takes two to four weeks, costs "somewhere in the six figures," he said. The company uses 3D printing to create life-like tissue from donor cells. "It's about better drugs—drugs tested more effectively in a more human-like model before they go into human testing," he said. "And virtually any drug you ingest goes through the liver."