What is tissue engineering? It is a field that applies biology and engineering to build functional substitutes for damaged tissue, usually by combining cells, a scaffold and biological signals. This page explains each part and where the evidence stands.
It is one branch of what is regenerative medicine, and most of its work is still laboratory and early clinical research.
How the field defines itself
A widely cited 1993 article in Science by Robert Langer and Joseph Vacanti described the problem the field set out to address. It opened by saying that the loss or failure of an organ or tissue is one of the most frequent, devastating and costly problems in human health care, and it presented tissue engineering as a new field applying the principles of biology and engineering to the development of functional substitutes for damaged tissue.
The approach differs from simply transplanting an organ from a donor. Instead of moving existing tissue, researchers try to fabricate it. A later review put the idea in a sentence: in tissue engineering and regenerative medicine, new viable and functional tissue is fabricated from living cells cultured on an artificial matrix in a simulated biological environment.
The three main components
That same review names three main components: cells, scaffold materials and the culture environment. It adds that the requirements for each are very different depending on the type of cells and the organ-specific application. A 2025 review in dentistry uses a compact label for the same idea, calling polymer-based scaffolds, stem cells and signaling molecules the tissue engineering triad.
In practice the three parts work together:
- Cells supply the living material that can form the new tissue. They may be stem cells, which are explained in what are stem cells, or more specialized cells.
- Scaffolds give the cells a structure to attach to and grow on while the tissue forms.
- Signals, such as growth factors, tell the cells what to become and how to behave.
Stem cells are only one possible cell input. Stored sources such as those covered in cord blood banking are a separate topic, since a tissue-engineered construct is built, not simply infused.
What scaffolds have to do
The scaffold is the most engineering-heavy component. The review of scaffold design lists strategies that include mimicking the extracellular matrix, responding to the need for mass transport, predicting the structural architecture, ensuring adequate initial mechanical integrity, modifying the surface chemistry and topography to provide cell signaling, and anticipating the material selection so as to predict the required rate of bioresorption. Put plainly, a scaffold must hold its shape long enough to support cells, let nutrients and waste move through it, send the right cues to cells, and then break down at a suitable pace.
The dentistry review mentions biodegradable polymers such as collagen and gelatin methacryloyl as scaffolding materials that mimic the extracellular matrix, support cell attachment and proliferation, and allow localized delivery of bioactive factors. It also describes injectable hydrogels and 3D bioprinting as recent innovations in scaffold design.
Different tissues need different designs. A review of periodontal tissue interfaces notes that the hard and soft tissues involved make strategies challenging to develop and require multiphase scaffolds, with the greatest challenge being the mechanical integration of consecutive layers to avoid delamination.
Evidence from animal studies
Much of the evidence comes from animal models. A scoping review of mandibular bone tissue engineering screened 4524 retrieved articles and included 72 studies in animals. The reviewers report that all the studies that used a scaffold reported increased bone formation compared with negative controls, and that mesenchymal stem cells combined with scaffolds increased new bone formation and improved healing in those animal models, according to the systematic scoping review.
The review also records which materials and signals were most common in that body of animal work. Calcium phosphates, especially tricalcium phosphate and hydroxyapatite, were the scaffolds most widely used in the mandibular studies, and bone morphogenic proteins were the most popular growth factors, with all subtypes promoting significant bone formation compared with controls. This shows how the three components are chosen together for one tissue: a mineral scaffold, a cell type and a signaling protein suited to bone.
The same authors were careful about what that means for people. They wrote that several shortfalls must be addressed before the findings can be translated into clinical practice, and that a greater understanding of the biological aspects of the regenerative triad is needed before widespread translation. An animal result, in other words, is a starting point for clinical research and not a statement about human treatment.
How it relates to regenerative medicine
The scaffold review uses the combined phrase tissue engineering and regenerative medicine, which reflects how closely the two overlap. Regenerative medicine is the broader label and includes approaches that never involve a built construct, while tissue engineering is the part that fabricates tissue from cells, matrix and signals outside or inside the body. A reader meeting either term in an article about a treatment should ask the same questions: what the components are, what was tested and in what kind of study, and what regulatory status the specific product has.
Those questions matter because the language around the field is often more confident than the evidence. Terms such as scaffold, bioprinted and lab-grown describe a method of preparation, not a clinical result, and a method that works in a dish or in a small animal model still has to clear the problems of blood supply, immune compatibility, scaffold breakdown and standard protocols described below.
The unsolved problems
Blood supply is one of the clearest limits. The scaffold design review says that achieving adequate vascularization is a major challenge, because without it no three-dimensional thick tissue such as the heart, liver and kidney can remain viable. Thin or avascular tissues are therefore easier targets than whole organs.
The dentistry review likewise lists immune compatibility, scaffold degradation rates and the standardization of clinical protocols as challenges that remain despite progress. These are not details: a scaffold that degrades too quickly or too slowly, or a construct the body reacts against, can fail even when the underlying cell biology is sound.
Regulatory status in the United States
A small number of engineered tissue products have gone through FDA licensure. The agency’s list of approved cellular and gene therapy products includes entries described as allogeneic cultured keratinocytes and dermal fibroblasts in murine collagen and as an acellular tissue engineered vessel. Being on that list is a regulatory status for a specific product and a specific use, and it does not transfer to other engineered tissues.
Whether a given engineered tissue is suitable for a given person is a question for a licensed physician who knows that person’s situation.
Frequently asked questions
Is tissue engineering the same as stem cell therapy?
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No. Stem cells can be one ingredient, but tissue engineering also relies on scaffold materials and biological signals to build a tissue structure.
What is a scaffold in tissue engineering?
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It is an artificial matrix on which cells are cultured, designed to support attachment and growth and to degrade at a suitable rate as new tissue forms.
Why is it hard to engineer whole organs?
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Thick tissues need blood vessels to stay viable, and creating adequate vascularization is a major unsolved challenge cited in the scaffold design literature.
Do animal results mean a treatment works in people?
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No. Reviewers of animal studies say shortfalls must be addressed before findings can be translated into clinical practice.
