Trends in Biotechnology
ReviewNew Technologies To Enhance In Vivo Reprogramming for Regenerative Medicine
Section snippets
Why Is It Difficult To Manipulate Molecular Functions of Cells In Vivo?
Mammalian tissue functions are mediated by cell populations that define their state, size, and interaction with other tissues and the environment. The molecular components that drive the fate of these cells and collective tissue behavior are delineated during development and are preserved thereafter through epigenetic regulatory mechanisms. As a result of disease or aging, these cellular programs become dysregulated and organ systems suffer damage or loss.
Re-establishing or reprogramming [1]
CRISPR/Cas9-Based TFs for In Vivo Reprogramming
The type II clustered regularly interspaced short palindromic repeat (CRISPR) system and the CRISPR-associated Cas9 endonuclease are new technologies derived from the bacterial immune system that target and cleave foreign DNA (such as from viruses and plasmids). This elegant system has been engineered to be composed of a short guide RNA (gRNA or sgRNA) coupled to the Cas9 enzyme, and can identify nearly any sequence in the genome that exhibits complementarity to the sequence of the sgRNA, with
Synthetic Biology Tools Offer Combinatorial Gene Regulation for Smarter Reprogramming
Given the importance of TF control for reprogramming, tools from synthetic biology such as new genetic parts or gene circuits, coupled with mathematical modeling and engineering logic, can open new doors in reprogramming and regenerative medicine. For example, gene circuits [30], which are composed of natural or engineered promoters and well-characterized genes, are inducible systems introduced into cells that receive an input (such as a chemical or TF), process the strength of the interaction,
Nanomaterials Enable Delivery of Large Payloads for In Vivo Reprogramming
Nanoscale objects with high aspect ratios (such as nanowires and nanostraws) have emerged as new vehicles to deliver reprogramming factors into cells because they can penetrate into and through the plasma membrane without rupture [41], providing direct access to the cytosol and nucleus [42]. Decorating biomolecules onto the surface or within the nanomaterials enables straightforward delivery of a uniform and large payload to any number of cells that interface with the materials. Instead of
Engineered Biomaterials Can Enhance In Vivo Reprogramming Pressures
Although intrinsic reprogramming pressures have been the primary tool used to initiate changes in cellular programs, several studies have shown that exposing cells to a different microenvironment can reshape their expression profile [60]. These changes are mediated through alterations in metabolism [61] and synergize with other factors present in the microenvironment, such as cytokines [62], to adjust chromatin state [63] and subsequent cellular fate. Given that biomaterials offer the ability
In Vivo Cellular Reprogramming Enhances Functional Recovery Following Disease or Injury
The technologies described above offer exciting possibilities for improving the therapeutic outcomes of regenerative strategies being explored for diabetes, liver fibrosis, heart failure, and central nervous system (CNS) injuries (Table 1). The high prevalence of diabetes, and substantial transcriptional and chromatin similarity between pancreatic β cells and other acinar and endocrine cells, make the pancreas an attractive target for in vivo reprogramming [79]. In the past, AAVs were used to
Concluding Remarks and Future Perspectives
Reproducibly augmenting cell behavior and fate in vivo has already demonstrated the ability to improve functional recovery from injury (myocardial infarction, ischemia/reperfusion injury, CNS injuries) and ameliorate disease (diabetes, liver fibrosis) in animal models. Clinically translating these therapies to humans, however, will require both the use of models more predictive of human therapeutic outcomes and the continued development of delivery strategies that overcome the limitations of
Acknowledgments
The authors acknowledge support from the 3M Foundation and the University of Michigan. The authors regret that, owing to space and reference number limitations, some important studies could not be included.
Glossary
- Adeno-associated virus (AAV)
- AAV-based vectors are one of the most commonly used intracellular delivery methods for reprogramming. AAV does not integrate into the host cell genome and does not elicit an immune response; however, infected cells are phagocytosed over time. In addition, because they are non-integrating, ectopic transcription factor (TF) expression declines over time.
- Lentivirus (LV)
- another common method for delivering reprogramming factors. Lentivirus vectors integrate into the host
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Reprogramming of pancreatic islet cells for regeneration and rejuvenation
2023, Current Opinion in Genetics and DevelopmentCRISPR genome engineering for retinal diseases
2021, Progress in Molecular Biology and Translational ScienceCitation Excerpt :Overexpression of transgenes by gene augmentation may be associated with toxic effects to retinal cells.110–112 The level of gene activation with CRISPRa has the potential to be tailored by varying the number of activators recruited to a particular site, ensuring the level of expression is non-toxic.113,114 CRISPRa systems are varied but most involve the transcriptional activator VP64.
Sweat gland regeneration: Current strategies and future opportunities
2020, BiomaterialsCitation Excerpt :Besides CRISPR/Cas9 TF systems, nanoparticle vectors composed of hydrophobic lipids can also complex with or encapsulate different types and combinations of reprogramming factors, ranging from nucleic acids (e.g., lipid DNA, long non-coding RNAs, circular RNAs, miRNAs, aptamer) to proteins and small compounds for in vivo delivery. The system is designed to steer TF concentrations toward desired values via control over the transcriptional activation or repression and/or optimization of the production-to-degradation ratio without triggering phagocytosis of reprogrammed cells [140]. Notably, sequential releases can be achieved with layered materials [160].
Polyplex transfection from intracerebroventricular delivery is not significantly affected by traumatic brain injury
2020, Journal of Controlled ReleaseCitation Excerpt :Thus, therapeutic strategies for the regeneration and integration of neurons at the site of injury could greatly impact patient recovery after TBI. While stem cell transplantation therapies for tissue regeneration in the CNS have rapidly progressed into clinical study [6], gene therapies that manipulate endogenous neural progenitor cells (NPCs) with transcription or growth factors offer a promising alternative [7–9]. Compared to cultured cell therapies used as transplants, “direct reprogramming” approaches are more cost effective, less toxic, and promise access to different neuronal subtypes that may repair damaged nerve circuits with greater efficacy [8,10].