How can this goo help regrow cartilage in our joints?
Rex Huppke here!
Researchers at 美国西北大学 have developed a rubbery goo that can be injected into joints to help regrow damaged cartilage. I spoke with Prof. Samuel Stupp, director of the university’s Center for Regenerative Nanomedicine, to learn all about it.
Let’s start with the basics. Can you explain cartilage and the role it plays in our joints?
Cartilage is one of the most important tissues in our body for proper functioning of our joints. And of course the joints are critical to our ability to move without pain. What makes cartilage particularly important is the fact that it does not have the ability to regenerate after a human being reaches full development. So that means that past the age of 18, cartilage regeneration becomes very difficult, if not impossible.?
It’s critical, but it doesn’t regenerate? Sounds like a bit of a design flaw.?
Species vary as to how easily they regenerate cartilage. For example, rabbits regenerate cartilage more easily than we do. But fundamentally, it's very difficult to know why. What's the evolutionary reason?? It probably has something to do with the function the tissue has, in that it absorbs shock and reduces friction in our joints so we can move freely. But there are no blood vessels in our cartilage, which is why it’s difficult to regenerate. So it may have something to do with the fact that the function cannot accommodate the presence of blood vessels.
I saw the biomaterial you’ve developed described as a rubbery goo. Can you break down how this goo works and how it’s administered?
This is a material that looks like a paste of sorts. Think of it as a toothpaste, maybe it’s a little more robust than toothpaste. You can squeeze it out of a tube, you can inject it through a syringe. We needed to make sure it can be injected in this way. A surgeon can prepare the surface where the defect is in the cartilage, and the defects are going to be of different sizes and shapes, so it's important it’s a paste-like material that can conform.
What is the material?
The material is made of natural components. There's nothing foreign there. The material has these molecules we have developed over a couple of decades that are composed of peptides. Peptides are the components of proteins, and so an important part of our structure as a living system. We are made of many proteins.
I think I’m made of many doughnuts.
The molecules are called peptide amphiphiles — that’s their formal name — and they are able to self-assemble when you put them in water. They self-assemble into filaments that are of nanoscale in dimension, and they mimic a lot of the filaments we naturally have around the cells in our body.?
And what do the filaments do?
The cells in our body are surrounded by something called the extracellular matrix. It’s a material around the cells that contains signals for the cells that tell them what to do and provide the cells with mechanical support. That extracellular matrix helps the cells connect to each other to make tissue. So we were able to mimic those nanoscale filaments that we normally have around cells using peptide amphiphiles, and these filaments also contain a bioactive peptide that binds to a specific protein that instructs cartilage cells to grow and proliferate.
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It sounds like you're injecting a goo that then tricks the body into doing something it doesn't normally do, right?
Right. You need that protein I mentioned in order to cause the cartilage to regenerate. It creates a scaffold and gives a signal to other uncommitted cells to turn into cartilage cells.
So you tested the material on sheep. Why sheep?
They are a large animal that, in a way, resembles the size of humans. The joints might be of comparable dimension to the joints in humans, and so that would validate the tests. They also move around a lot.
They may be more active than humans, if we’re being honest. How would using a biomaterial differ from current methods of repairing joints?
People have used different kinds of biomaterials to try to regenerate cartilage. There have been clinical trials ongoing, but the difference between our strategy and others is that our biomaterial is inherently bioactive, with a protein that signals to other cells to regenerate cartilage. Some have used, for example, hyaluronic acid to promote regeneration of cartilage. And some have used polymers to create a scaffold for cells, but it wasn’t bioactive. We’re doing both, creating a scaffold that is itself bioactive.
Amazing. Now let’s get to the most important question: My knees hurt. When might I be able to get some of this rubbery goo?
It will take a few years to get this into the clinic. But hopefully it’s not many years.
Just Curious is sponsored by Provable, the science communication force of M. Harris & Co. and MG Strategy + Design.
This interview has been condensed and edited for clarity. Header image by DALL-E Open Ai. If you liked what you read today, here's more.