What is tissue engineering?
Tissue engineering forms part of a multidisciplinary field known as regenerative medicine, which includes areas such as stem cell research, molecular biology, gene therapy, biomaterials and nanotechnology, to name a few.1 Specifically, tissue engineering aims to repair or replace tissues that have been damaged or diseased by growing new tissues to be implanted into a patient. Tissue engineering often involves the use of seeding a patient’s own or donor stem cells onto a biocompatible scaffold to create tissue that is compatible with the patient, and which is structurally and functionally identical to that which is being replaced. The scaffolds used in tissue engineering can be created though methods such as:
· decellularising tissue to reveal the underlying extracellular matrix structure, which can then be seeded with a patient’s own stem cells to promote tissue growth around a defined structure2
· 3D printing scaffolds from biocompatible materials (e.g. polymers).3
· Through the application of these techniques and others, researchers have been able to create a range of tissues and organs such as blood vessels, tracheas, bladders and livers.4,5 However, in many of these cases, especially when creating complex tissues (tissues with multiple layers and cell types), researchers have struggled to create tissues that retain the functional characteristics of the healthy tissues they are trying to recreate. Thus, most successful tissue engineering applications to date have come in the form of a number of skin substitutes, which have been translated from research into commercial products and are used regularly in hospitals around the world.6
Tissue regeneration was the focus of my PhD studies, which centred on trying to regrow retina tissue that had degenerated due to diseases such as age-related macular degeneration (AMD), the most common cause of sight loss in the UK. When I was finishing my studies in 2010, it felt like a treatment or cure for AMD using tissue engineering techniques was still light years away. However, the field has advanced rapidly in recent years. Importantly, a number of these advances have gone on to be clinically tested in humans and are showing incredible promise.
A recent breakthrough in retina tissue engineering
In March this year, it was announced that two patients were able to regain their sight after receiving stem cell-derived retinal tissue. The two patients, previously unable to read (even with glasses) due to AMD, received a patch seeded with stem cells designed to mimic the retinal pigment epithelium (RPE). The RPE is one of the many layers of the retina that supports the light-sensitive photoreceptor cell layer and is often damaged in patients with AMD. The patch was surgically inserted under the patient’s retina to replace the damaged RPE layer and monitored for 12 months, after which the two patients were able to read 60-80 words per minute (with the help of normal reading glasses). These results constituted the first instance of restoring vision using tissue engineering techniques and demonstrated that new therapies could be right around the corner. However, while very promising, it is important to note that many further studies need to be completed, and that this study only demonstrated the safety and effectiveness of a new technique in two patients. The researchers hope that an affordable ‘off-the-shelf’ treatment could be made available in the next five years.7
As other examples of tissue engineering become clinically successful, the widespread use of these techniques could have profound effects on health care, including:
· delivering outcomes that exceed those of conventional surgical therapies
· eliminating organ transplant rejection (or the need for organ donation altogether)
· lowering the use of medications for patients
· lowering the risks of complications
· reducing medical follow-ups.