Bone homing of mesenchymal stem cells by ectopic alpha 4 integrin expression
Sanjay Kumar1, Selvarangan Ponnazhagan
1Department of Pathology, The University of Alabama at Birmingham, Birmingham, AL 35294-0007, USA.
Summary
Transient expression of alpha4 integrin on mesenchymal stem cells (MSC) enhances bone homing in mice. Engrafted MSC retained stem cell properties and formed bone cells, offering a new strategy for bone defect therapies.
Area of Science:
- Regenerative Medicine
- Cell Therapy
- Molecular Medicine
Background:
- Mesenchymal stem cells (MSC) hold promise for tissue regeneration and cell therapy due to their pluripotent nature.
- A key challenge for autologous MSC transfer is poor engraftment to target tissues.
- Improving MSC homing is crucial for effective therapeutic applications.
Purpose of the Study:
- To investigate if transient expression of alpha4 integrin (CD49d) on MSC can enhance bone homing.
- To evaluate the impact of alpha4 integrin and beta1 integrin (CD29) heterodimerization on MSC targeting.
- To assess the in vivo differentiation potential of engrafted MSC in a mouse model.
Main Methods:
- Genetically engineered MSC to transiently express alpha4 integrin (CD49d).
- Utilized an immunocompetent mouse model to assess bone homing of modified MSC.
- Confirmed alpha4 integrin and beta1 integrin (CD29) heterodimerization.
- Analyzed in vivo differentiation of engrafted MSC into osteoblasts and osteocytes.
Main Results:
- Transient alpha4 integrin expression significantly increased MSC bone homing in vivo.
- Alpha4/beta1 integrin heterodimerization was confirmed to mediate enhanced targeting.
- Engrafted MSC successfully differentiated into osteoblasts and osteocytes within mouse limb bones.
- Modified MSC retained their stem cell properties post-engraftment.
Conclusions:
- Transient ectopic expression of alpha4 integrin is a novel strategy to improve MSC bone homing.
- This approach facilitates targeted delivery and in vivo bone formation by MSC.
- Potential applications include therapies for osteopenic bone defects and bone metastasis.
Related Concept Videos
01:19Mesenchymal Stem Cells
Mesenchymal stem cells (MSCs) are adult stem cells that can differentiate into most connective tissue cell types, except for hematopoietic cells, depending upon the source of MSCs. For example, bone-marrow-derived MSCs (BM-MSCs) can differentiate into osteocytes, hepatocytes, and pancreatic and neuronal cells. MSCs can be isolated from various sources such as bone marrow, placenta, adipose tissue, teeth, and Wharton’s jelly, a gelatinous substance in the umbilical cord. The ease of their access...
01:10Integrins
Animal and protozoan cells do not have cell walls to help maintain shape and provide structural stability. Instead, these eukaryotic cells secrete a sticky mass of carbohydrates and proteins into the spaces between adjacent cells. This network of proteins and molecules is called an extracellular matrix or ECM.
Some ECM proteins assemble into a basement membrane to which the remaining components adhere. Proteoglycans typically form the bulk of the ECM while fibrous proteins, like collagen,...
Some ECM proteins assemble into a basement membrane to which the remaining components adhere. Proteoglycans typically form the bulk of the ECM while fibrous proteins, like collagen,...
01:15Activation of Integrins
Integrins bind ligands and transmit information from outside the cell to inside or vice-versa through an "outside-in signaling" or "inside-out signaling."
In "outside-in signaling," external factors in the extracellular space bind to exposed ligand binding sites on integrins. This causes the inactive protein to undergo a conformational change to become active. Integrins are often clustered on the cell membrane. Repetitive and regularly spaced ligand binding events provide an effective stimulus.
In "outside-in signaling," external factors in the extracellular space bind to exposed ligand binding sites on integrins. This causes the inactive protein to undergo a conformational change to become active. Integrins are often clustered on the cell membrane. Repetitive and regularly spaced ligand binding events provide an effective stimulus.
01:17Intracellular Signaling Affects Focal Adhesions
Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer's hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some...
Some...