Stem cell technology

Platelets carrying immunotherapy agents such as antibodies against immune checkpoint protein PD-1 have been tethered to hematopoietic stem cells to bring this immunotherapy into the bone marrow, where it is needed to treat acute myeloid leukemia (AML). The technology has been developed in the lab of Zhen Gu, Founderfounder of Zencapsule and Professor of bioengineering at UCLA Samueli School of Engineering.

Extracellular vesicles can be isolated from cell culture media and from body fluids. Since the regenerative effects of MSCs are partly mediated by secreted exosomes that carry proteins, ncRNA, RNA, and lipids, MSC exosomes are being explored as a cell-free therapy in regenerative medicine.

In contrast to drugs, which are chemically defined products that can be replicated, cell therapy and tissue engineering products are defined by their process. In order to standardize cell products the process needs to be well definedwell-defined. Production may be scaled up so that the cell product is manufactured in one or two facilities and then shipped to locations where they are needed. Alternatively, production may be scaled out to multiple facilities, such as dedicated hospital clean rooms, where it is produced in smaller batches on siteon-site.

Stem cell culture shares many of the same protocols and equipment as standard mammalian cell culture, but there are special conditions needed to maintain them in an undifferentiated state, such as supplying certain growth factors and growing cells in colonies on a feeder cell layer. While mouse-derived feeder cells are often used in research, human feeder cells (Xeno-free) or feeder-free culture systems are needed for clinical use to avoid patient exposure to animal pathogens. Stem cells are also used to generate cultured meat, a product that also aims to be grown feeder-free and serum-free to avoid relying on animal use. The Cultured Meat Foundation is aiming to create a bank of inducededinduced pluripotent cells (iPS cells) from cow, pig, chicken, tuna, salmon, and lobster that are grown serum freeserum-free and feeder freefeeder-free.

In development, stem cells receive cues from their environment, causing them to up regulateup-regulate and down regulatedown-regulate genes whichthat control stemness and cell differentiation into specialized cell types. InStem cell scientists and engineers seek to program cells in culture, stem cell scientists and engineers seek to program cells in a predictable way by supplying growth factors, and physical cues or modifying the expression of genes that control stemness or key cell type specifictype-specific genes.

• Direct Labeling.: A labeling agent is introduced into the cells, which is incorporated or attached to the cells prior to transplantation. Radionuclides are used for direct labeling but allow only short-term monitoring because radiodecay and diffusion of signal thoughthrough cell division and dispersion. Other direct labellinglabeling materials include nanoparticles or quantum dots. Depending on the radiotracer, imaging can be performed using single-photon emission computed tomography (SPECT) or positron emission tomography (PET). Magnetic resonance imaging (MRI) can track cells labeled with superparamagnetic iron oxide particles (SPIO).

• Indirect Labeling.labeling: Several reporter gene strategies have been used in pre-clinical stem cell transplant studies to study the long-term fate of transplanted cells. A reporter gene may be introduced into cells prior to transplantation that expresses fluorescent proteins such as green fluorescent protein or bioluminescence. The herpes simplex virus type 1 thymidine kinase (HSV1-tk) system phosphorylates an exogenously administered substrate. PET imaging can be used to detect a dopamine 2-like receptor reporter gene, which codes for a cell membrane protein that binds an exogenously administered probe. Another reporter gene system uses a thyroid transmembrane protein, sodium-iodide symporter (NIS), which transports iodine into cells in exchange for sodium, which can be imaged with PET or SPECT with radioactive iodine or Technetium Tc-99m pertechnetate. MRI detectedMRI-detected reporter genes are generally iron homeostasis proteins, reporter enzymes, and reporter genes whichthat generate chemical exchange saturation transfer. Reporter gene systems are not used in humans due to the potential for adverse effects of the integration of foreign DNA into human cells. Safe methods for long-term monitoring of transplanted cells in human patients are needed.

• Pre-plating makes use of the phenomenon that stem cells tend to adhere to culture plates and dishes more than the rest of the cells in a population. Pre-plating has been shown to enrich for mesenchymal stem cells (MSCs) from bone marrow or human adipose-derived stem cells from lipoaspirate from a liposuction procedure.

• Density gradient centrifugation. Separation of cells by density gradient requires knowledge of the density of the target cell type. A density gradient is established in a test tube and centrifuged cells accumulate at a position where density of cells matches the density of medium. Ficoll-paque, Percoll, and RosetteSep are used as media for stem cell separation by density gradient.

Induced Pluripotentpluripotent Stemstem Cellscells, abbreviated as iPS cells or iPSCs, are generated in the laboratory by treating adult differentiated cells from sources such as skin, with factors that reprogram the cells. The pluripotent cells can then be treated with factors that signal the cells to differentiate into another cell type.

Tissue engineering is the differentiation of cells into specific cell types using cues like growth factors, physical scaffolds, and other 3D cell culture approaches to produce functional replacement tissue or organs. Synthetic biology approaches in tissue engineering are being used for programming cells to self assembleself-assemble into tissues.

Hematopoietic stem cell transplants are routinely used to treat patients with cancers and other blood and immune system disorders. Hematopoietic cells can come from bone marrow, blood, orand umbilical cords. Many cell therapies use MSCs (mesenchymal stromal cells/mesenchymal stem cells), or PBSCPBSCs (Peripheralperipheral blood stem cellcells) or other stem cells, which may be effective due to their ability to differentiate into various tissues or due to secretion of paracrine factors such as growth factors, anti-inflammatory or pro-angiogenic factors. Cells may also be used as carriers of therapeutic agents.

Cell therapies being used or in development for treating cancer or autoimmune diseases use T cells and regulatory T cells (Tregs), respectively engineered with chimeric antigen receptors (CARs). CAR-T and TCR-T are engineered T cells, and CAR-Treg and TCR-Treg therapies are engineered Tregs. FDA-approved CAR-T products are generated from harvesting autologous T cells from patients, followed by gene editing and infusion back into the patients. Allogeneic or universal cell therapy products, also called off-the-shelf cell therapy products, would allow a broader implementation of these cell therapies. One method being researched is to derive natural killer (NK) cells from iPSCs and engineer iPSC-derived NK cells to target and kill cancer cellcells similarly to CAR-T cells.

Platelets carrying immunotherapy agents such as antibodies against immune checkpoint protein PD-1 have been tethered to hematopoietic stem cells to bring this immunotherapy into the bone marrow, where it is needed to treat acute myeloid leukemia (AML). The technology has been developed in the lab of Zhen Gu, Founder of Zencapsule and Professor of bioengineering at UCLA Samueli School of Engineering.

• Athersys developed MultiStem®, a patented, adult-derived “off-the-shelf” stem cell product platform, for multiple diseases, including neurological, cardiovascular, and inflammatory and immune disease areas, as well as other indications where there is an unmet medical need

Stem cells are used to grow organoids and organ-on-a-chip devices for disease modeling, drug development, drug testing, and personizedpersonilized medicine.

The secretome is the set of molecules such as proteins, nucleic acids, lipids, and extracellular vesicles secreted to the extracellular space. Microvesicles and exosomes are two classes of extracellular vesicles. Exosomes are smaller and are released by endosome fusion with the plasma membrane, and microvesicles are shed from the plasma membrane. Exosomes were once thought to be a method for cells to discard unwanted proteins but are now known to have a role in intercellular communication with both neighboring and distant cells in the body.

Extracellular vesicles can be isolated from cell culture media and from body fluids. Since the regenerative effects of MSCs are partly mediated by secreted exosomes whichthat carry proteins, ncRNA, RNA and lipids, MSC exosomes are being explored as a cell-free therapy in regenerative medicine.

Stem cell therapies aimed at treating an injured myocardium in patients that had experienced heart failure were intended to differentiate into cardiomyocytes, and engraft and integrate with the host tissue. The stem cells rarely differentiated into heart muscle and integrated into the host tissue, and cardiac function was restored, due to the secretion of factors from the exosomes of the transplanted induce pluripotent cell (iPSC) derived cardiomyocytes.

Aegle Therapeutics -: isolates extracellular vesicles from bone marrow derivedmarrow-derived MSCs to treat dermatological conditions

Exopharm: - developingdevelops therapies based on exosomes from platelets and stem cells

Regeneus: -a clinical stageclinical-stage regenerative medicine company using MSCs and their secretions to treat knee osteoarthritis