**3. Stem cells and regeneration**

**Figure 2.** A view of a eukaryotic gene, its control elements in the DNA and the proteins that guide the RNA polymerase

Different species have significant capabilities to regenerate parts of the body or whole organism after injury (**Figure 1**), but a thorough understanding of the molecular basis of regenera-

Cells are building units of tissues and organs and tissues are the basic unit of function in the body. In general, cells secrete their own support materials and structures, which are called an *extracellular matrix*. This matrix, or scaffold, is supporting the cells; it also performs as a relay

Cells acquire messages through multiple sources that grow available from the local environment. Each signal can enhance or initiate a series of responses that decide what will happen to the cell. By understanding how individual cells react to signals, interact with their surrounding environment, and organize them into tissues and organisms, researchers can manipulate

tion mechanisms will require detailed genomic resources.

these processes to repair damaged tissue or even create new cells.

**2. Building blocks and matrix**

station for a number signaling molecules [2].

**2.1. Cells**

4 Tissue Regeneration

**2.2. Messages/signals**

to the correct starting point for transcription [3].

Tissues in the human organism are generated, maintained, and repopulated by *stem cells* (**Figure 3**). These are specialized cells capable of cell renewal and can differentiate into different cell types in the human body. Stem cells have several differentiation programs; therefore, they possess information to allow them to become any cell in the body or a restricted cell type with a specialized function. These abilities make stem cells extremely useful for biomedical applications and regenerative medicine and have become the main molecular tool for these purposes. Skeletal muscles have some ability to regenerate and form new muscle tissue, while cardiac muscle cells do not regenerate. However, new research suggests that cardiac stem cells may be coaxed into regenerating cardiac muscles with new medical strategies. Smooth muscle cells have the greatest ability to regenerate.

Questions about how and why tissue regeneration attracts the attention of countless biologists, medical engineers, and doctors. Renewable capacity varies widely across organs and organisms and a range of model systems with different technical features and innovation strategies are studied. Several key issues common to natural regeneration are receiving new attention from improved models and approaches, including identification of innovative

**Figure 3.** Induced pluripotent stem cells (iPSCs) were first created from human cells in 2007. These are adult cells that have been genetically converted to an embryonic stem cell-like state [3].

capacity; importance of stem cells, differentiation and differentiation; how regeneration signals begin and target; and mechanisms that control proliferation and renewed regeneration.

Different ways to create a new fabric or tissue is using the present scaffold. The donor tissue or organ cells are stripped and the maintained collagen scaffold is used to form a new tissue. A new tissue has been created in the biological engineering of the heart, liver, lungs, and kidney tissues in rat. This approach holds great promise for the use of scaffolds from human tissues that are discarded during surgery and integrated with the patient's own cells for the

Introductory Chapter: Concepts of Tissue Regeneration http://dx.doi.org/10.5772/intechopen.76996 7

The tissue needs a good "draining and plumbing system" (veins or arteries), a way to feed nutrients into cells and carry waste. Without blood supply or any similar mechanism, cells die quickly. Ideally, scientists would like to be able to create engineered tissue using a plumbing system that has already been built (lattices). New hope for the bum knee: cartilage has been very difficult, if it is not impossible to repair since cartilage lacks a blood supply to promote regeneration. The gel/adhesive combo was successful in regenerating cartilage tissue follow-

The main goal of tissue regeneration studies is to acquire knowledge that will enhance the new wide range of regenerative medicine. This information may include evidence to stimulate stem cell activity, structural engineering of better scaffolds or direct initiation of biologic regeneration programs. Scientists already understand some forms of regeneration enough to manipulate and modify major events for therapeutic reasons. For example, the common practice of bone marrow transplantation is to properly guide hematopoietic cells to regenerated blood cells. However, for most examples of innovation, research has begun to acquire knowledge and techniques to try to ban or enhance selective steps selectively during renewal.

Musculoskeletal injuries impact millions of people globally and affect their health and well-being as well as of their companion and athletic animals. Soft-tissue injuries represent almost half of these and are associated with unorganized scar tissue formation and long timedepending healing processes. Cell based therapeutic strategies have been developed in the past decades aiming at the treatment and reversion of such disorders. Stem cells are appealing in the field, being a responsive undifferentiated population, with ability to self-renew and differentiate into different lineages. Mesenchymal stem cells can be obtained from several adult tissues, including the synovial membrane. Synovia-derived mesenchymal stem cells can be found in individuals of any age and are associated to intrinsic regenerative processes, through both paracrine and cell-to-cell interactions, thus, contributing to host healing capacity. Studies have demonstrated the potential benefit of synovia-derived mesenchymal stem

Bone regeneration is a surgical technique (**Figure 4**) that uses barrier membranes to direct, or guide, the growth of new bone at the site of the defect. The principle is that the barrier

cells in these regenerative processes in both human and veterinary medicine.

work of dedicated members that cannot be rejected by the immune system.

ing surgery in a recent clinical trial of patients.

**5. The main goal of tissue regeneration**

**5.1. Musculoskeletal tissues**

**5.2. Bone regeneration**
