Stem cells: Stem cells are a fundamental component of regenerative medicine, possessing a remarkable ability to differentiate into various cell types. Embryonic stem cells, derived from early embryos, can give rise to any cell in the body. Adult stem cells, found in specific tissues (such as bone marrow or adipose tissue), contribute to tissue repair and maintenance.<br /><br />Cell signaling: Regeneration relies on complex signaling pathways. Cells communicate through growth factors, cytokines, and components of the extracellular matrix. These signals direct cell behavior during tissue repair.<br /><br />Epigenetics: Understanding epigenetic modifications—changes in gene expression without altering the DNA sequence—is crucial. Epigenetic factors influence cell fate and tissue regeneration.<br /><br />Using laboratory-engineered tissues and organs to replace damaged or missing tissues in the human body (main application):<br /><br />Laboratory-engineered tissues have already been used to replace many damaged or missing tissues in the human body, with unprecedented clinical success. Examples of these tissues include skin, cartilage, bone, nerve, cardiac, and muscle tissue, as well as ligaments and tendons such as those of the shoulder and knee joints (cruciate ligaments) and foot tendons. Furthermore, laboratory-engineered organs have also been used to replace a number of damaged organs in the human body, such as the bladder, blood vessels, heart valves, and bronchi.<br /><br />Organs are more complex than tissues. Organs typically consist of multiple and distinct tissues and cells, while tissues consist of a single type of tissue and cell. From this perspective, we can conclude that laboratory organ engineering is more complex and challenging than tissue engineering. For this reason, the number of organs that scientists have been able to develop and produce is much smaller than their tissue-based counterparts. However, current research results and the predictions of scientists in this field indicate that regenerative engineering will, God willing, be able to develop more complex organs than those mentioned above, such as the heart, liver, kidney, lung, and pancreas, and then transplant them into humans. This will provide the ideal solution to the problem of waiting for organ donors.<br /><br />Among the organs that regenerative engineering is also expected to fully develop and transplant into humans are human limbs (the foot from the knee joint to the five toes). Work is already underway to develop and engineer fully human limbs containing all the tissues that make up a limb, such as bones, muscles, ligaments, tendons, nerves, blood vessels, cartilage, and skin.<br />Establishing and Developing the Process of Transplanting Engineered Organs:<br /><br />The applications of regenerative engineering are not limited to the development and engineering of tissues and organs, but also to establishing and developing the methods used in the process of transplanting them into the body to ensure high success rates and increased therapeutic effectiveness.<br /><br />Pharmaceutical Discoveries:<br />In addition to using engineered tissues and organs as replacements for damaged or missing tissues and organs, they can also be used in pharmaceutical discovery. This is because engineered tissues and organs closely mimic the physiological functions of existing tissues and organs in the human body, and therefore can respond to newly discovered and developed drugs in the same way as tissues and organs in the body. This can help:<br /><br />Improving the efficiency and safety of drug development because it is now possible to test the drug's effectiveness on tissue or organs outside the body, thus determining whether the drug formulation needs to be modified before it is used in humans.<br /><br />Reducing the need for animal testing.<br /><br />Cells in Regenerative Engineering:<br />Regenerative engineering uses various types of cells during the process of engineering and developing tissues and organs. To date, many cells have been used in regenerative engineering, including stem cells, progenitor cells, and differentiated cells.<br />Al-mustaqbal the top in lraq