Making Cartilage From a Printer

Anyone see this story?

Amazing advancements in the technology of 3D printing have been made at Scripps Clinic in La Jolla. Dr. Darryl D’Lima along with his colleagues report they have discovered a process to “bioprint” cartilage tissue ... Adapted from a Hewlett-Packard inkjet printer, the bioprinter spews out both cartilage progenitor cells and a biocompatible liquid that will congeal in the presence of ultraviolet light. In addition, the device can print bone cells necessary to deposit where cartilage attaches to bone.

(A less breathless take on the news is here.)

I especially loved the phrase “adapted from a Hewlett-Packard inkjet printer,” which has a certain mad-scientist-in-the-garage feel to it. The printed droplets are about one picoliter, or one billionth of a liter, and so are tiny enough to fill microscopic defects in cartilage or bone.

My prediction is we’ll see lots of new cartilage regeneration technologies in the 21st century. Great news, right?

Actually, it leaves me kind of depressed.

Why?

Because I think the fancy, high-tech solutions to regenerating cartilage -- maybe one day doctors will spray it out of a can? -- overlook the validity of natural solutions. That’s partly because of the following statement, which I believe to be wrong:

This tough, slippery tissue functions as a cushion between joints, but it does not often regenerate.

I think that’s false, and that cartilage does often regenerate. What’s more, it’s been shown that, after an injury to the tissue, the cartilage-making cells known as chrondrocytes kick into high gear. So your body tries to do the right thing, and heal itself.

But the real reason I believe cartilage often regenerates is because that’s what at least two clinical studies have shown. In at least one subject, a place where bone was exposed was later found to be covered with cartilage of almost full thickness. From my earlier linked post:

Here are some interesting numbers from a report published in Rheumatology magazine in 2006 entitled "Factors Affecting Progression of Knee Cartilage Defects in Normal Subjects Over Two Years."

Initially, there were 14 locations at Grade 3 (less than 50 percent thickness) in the subjects' knees. Three remained the same and five went to bare bone -- that's the bad news. However the good news is that almost half of them improved: four became Grade 2 and two Grade 1, which is nearly normal!

There were five sites at Grade 4, or bare bone. Now you'd expect at the end of two years, those five sites would still be at Grade 4, absent surgical intervention (such as a microfracture). But one ended up Grade 3, two were Grade 2, and one even healed all the way to Grade 1!

Now the initial durability of that fill-in cartilage can be questioned. Maybe it’s more fibrocartilage at first, but after microfractures, the fibrocartilage after a while begins to take on the appearance of normal articular cartilage.

So here’s why I’m depressed, in a nutshell:

No doubt, billions of dollars will be spent on finding ever-more clever ways to grow cartilage and insert it into human knee joints. We should expect no less, considering the state of medical technology, our relentless quest for progress and, not insignificantly, the potential profits to be made by someone.

What saddens me is there won’t be a commensurately well-funded effort to figure out how to encourage cartilage to regrow naturally. That’s a real shame. You wouldn’t need billions of dollars to conduct such a study, just some time, some willing subjects, and a healthy amount of skepticism that bio-engineering isn’t the only solution for this problem.