Tissue Engineering and Regenative Medicine
This past couple of weeks I had the opportunity of attending COSMOS for Tissue Engineering and Regenerative Medicine under Dr. Robert Sah and Dr. Roberto Gaetani. The first two weeks were lecture and lab skill bases since we were in-person and had access to the UCSD Bioengineering facilities. TE-RM is defined as combining cells and biomaterials to create tissues and/or regenerate existing tissue. Scientists can harvest, modify, and replace already existing cells to minimize patient rejection. They can also use donor cells or STEM cells to grow whole new tissue or induce regenerative reactions.
These donor cells range from bone marrow cells, embryonic cells, fetus cells, or other adult cells. Adult Stem cells are challenging to work with for tissue engineering since they have already differentiated or there is less tissue they can differentiate into. For example, there are four different levels of differentiated cells. First, embryonic cells are totipotent meaning that every cell can form any form of tissue. Next, they differentiate into pluripotent cells in the blastocyst which reduces the number of cells they can form. Next, fetal tissue is multipotent again limiting differentiation. Finally, unipotent cells are the actual tissue that is already differentiated meaning they have a unique function and are unable to differentiate into another tissue type.
Researchers, however, have been able to produce induced Pluripotent Stem cells (iPS) from adult skin fibroblasts which can differentiate into various types of tissue. With these new iPS, they can then introduce growth factors such as Bovine Serum, something derived from bovine fetal blood, to induce proliferation and cell function. With the grown tissues, they can use it as either a form of drug/disease modeling outside of living hosts or as a method of treatment.
Because researchers take cells, induce pluripotent, and then induce proliferation/differentiation, they have to use different assays to make sure cells are correctly progressing. Some methods of cell characterization are staining. Stains range from fluorescent to dyes and can vary in the procedural method. For example, stains like H&E diffuse into cell membranes and show if cells have an intact nuclear membrane or are most likely dead. Other stains, however, are incorporated into cells using antibodies and markers. If a target protein is present, an antibody will bind to that protein and then more staged antibodies will bind to that original antibody (a lot of antibodies). Then, scientists can activate the marked antibodies with specific wavelengths of light and see if a cell is producing proteins that match up with what it is supposed to be differentiated into.
To make cell culturing easy and repeatable, scientists have also accumulated different cell lines over the decades and stored them carefully in cell banks. For example, in the next two weeks, I will be working with RAW264.7 cells, a cell that was derived from a genetically mutated mouse cell. We will then apply a specific ligand or signaling molecule called RANKL to induce osteoclastogenesis differentiation hopefully. This is again important in disease modeling and will hopefully aid scientists in understanding the progression and cause of osteoarthritis.