Lending the healing body a helping hand
The human body has an amazing ability to heal itself, but sometimes in need a bit of a helping hand. Chris Smith went along to the material science department in Cambridge University to speak to Ruth Cameron and before her, Serena Best, to hear about their efforts to help tissues to repair themselves.
Serena - We're trying to address all sorts of different problems that occur all over the body. Everything from orthopaedic problems where we have degeneration of the tissue with age and through trauma, but also looking at regeneration of tissue when somebody has had a heart attack, for example, how can we help to repair the heart?
Chris - So, it sounds like a range of, in some instances, building a new body part to just implant versus actually building something that helps the body to put itself right.
Serena - Yes, absolutely and that is our ultimate goal, to think about the way in which we can encourage the body to self-repair. In order to do this, we need to create an environment into which we want to encourage the body cells to migrate.
Chris - And how are you doing that?
Serena - We're interested in producing porous structures which we refer to as scaffolds. These pores are ones that are not just solid like an Aero bar that they actually allow the cells to migrate right into the centre of the implant and move around inside the implant so that the body will hopefully repair itself in due course.
Chris - So cells, blood vessels and is the idea that this scaffolding will eventually disappear because the body will just dissolve it and replace it with its own tissue?
Serena - Absolutely, yes. Ideal situation for any of the implants we're putting in in this particular application will be that we kick-start the body to repair itself and then over a matter of time, the implant will disappear and will break down into natural by-products that can be then taken away by the natural system in the body.
Chris - Ruth, how are you making these scaffolds?
Ruth - I've got one here. This is a scaffold made out of collagen, which is one of the major proteins in your natural soft tissue. This has been made by an ice templating route using freeze drying. What we do is to take a very dilute solution of the collagen in water with some other bits and pieces in there as well. You freeze the whole thing and the ice makes ice crystals, but the collagen can't become part of those ice crystals and just gets pushed to the edges of these lots of tiny ice crystals. Then you sublime off the ice which means that you can go straight from ice to water vapour and you're left behind with the kind of ghost structure of the original ice crystals, which forms a porous structure of collagen and we can then stabilise that. It's this open porous structure that Serena was talking about that the cells can now go inside.
Chris - It looks a bit like the packing foam that came with the last computer I bought when it came through the post. I mean, is that sort of polystyrene almost, isn't it? So, if I cut into that, I would see lots of interconnected little pores and holes, and channels that cells could crawl into.
Ruth - That's exactly what you'd see. If you think about an expanded polystyrene, again, that's a kind of foamy structure, but the difference with this one is, of course, it's made of collagen. But it's also open pores. It means that the pores aren't closed single entities. They're all connected up and so, there are pathways for the cells to go right into the centre of that and do what they need to do.
Chris - That one looks like it came straight out of an ice cube tray in my freezer. Could you make any shape or size of those then?
Ruth - Yup! You can make a whole range of sizes and shapes. And not just macroscopically like this which does indeed look a bit like an ice cube, but you can also think about the ways that the ice crystals can grow.
Chris - One would then implant that into a tissue to make cells grow into it and do some kind of repair. But you might need different sorts of cells, different sorts of shapes, different therefore, configurations to do repair in different tissues.
Ruth - We can and we're increasing our knowledge of how to do that all the time. That's where a lot of the ongoing research is going. So, that's thinking about the shapes of the pores and the architecture that you're trying to get to direct the cells. But there are other things that we can do as well. So, it doesn't just have to be collagen within there that you can think about other biological macromolecules that are going to give different cues to cells. You need to think about the mechanics, how squashy it is, what the cells are going to experience, what the whole structure is going to experience more macroscopically, biomechanically. And you can also think about controlling the biochemistry along the surface of all these pores by putting peptide sequences on there. That will mean that certain cells will want to sit on there or to migrate and other cells won't have the attachment sites, so you can start to programme what's going on within the structure.
Chris - Serena, what sorts of things with that technology can you now attempt to repair?
Serena - We started looking at cartilage repair.
Chris - Cartilage being in joints.
Serena - Yes, that's right. So in particular, if you imagine the soft tissue in your knee joint, people have all sorts of tears and damage that can occur due to sporting injuries or just due to old age. So, the original idea with these collagen scaffolds was to make them compatible both with the bone that we're putting into contact with, but also give it the mechanical properties of cartilage.
Chris - You made effectively a little patch that you could put into a joint which would replace the cartilage and then get it to regenerate itself in someone who previously had arthritis.
Serena - That's right. We're also interested in developing the collagen scaffolds in the form of a heart patch. And so, this is where we can put a patch on to the heart, have it stitched in surgically, but it will be there to deliver the cells to help a patient recover after a heart attack.