the-micronucleus-assay-on-cryopreserved-whole-blood

The Micronucleus Assay on Cryopreserved Whole Blood

The in vitro cytokinesis-block micronucleus (CBMN) assay is a widely used technique in radiobiology research, biological dosimetry, genotoxicity studies, ...

Ghent University

Given the low self-healing capacity of fibrocartilage and hyaline cartilage, tissue engineering holds great promise for the development of new regenerative therapies. However, dedifferentiation of cartilage cells during expansion leads to fibrous tissue instead of cartilage. The purpose of our study was to generate 3D microtissues, spheroids, mimicking the characteristics of native fibrocartilage or articular cartilage to use as modular units for implantation in meniscal and articular cartilage lesions, respectively, within the knee joint. A set of parameters was assessed to create spheroids with a geometry compatible with 3D bioprinting for the creation of a biomimetic cartilage construct. Fibrochondrocytes (FC) and articular chondrocytes (AC) spheroids were created using a high-throughput microwell system. Spheroid morphology,  viability, proliferation and extracellular matrix were extensively screened. After 2D expansion, FC and AC dedifferentiated, resulting in a loss of cartilage specific extracellular matrix proteins. Spheroid formation did not result in FC redifferentiation, but did lead to redifferentiation of AC, resulting in microtissues displaying collagen II, aggrecan and glycosaminoglycans. This study demonstrates 3D cartilage mimics that could have a potential application in the next generation of Autologous Chondrocyte Implantation procedures. Moreover, spheroids can be used as building blocks to create cartilage constructs by bioprinting in the future.

Scaffold Free Microtissue Formation for Enhanced Cartilage Repair.

The cytokinesis-block micronucleus (MN) assay is a widely used technique in basic radiobiology research, human biomonitoring studies and in vitro radiosensitivity testing. Fresh whole blood cultures are commonly used for these purposes, but immediate processing of fresh samples can be logistically challenging. Therefore, we aimed at establishing a protocol for the MN assay on cryopreserved whole blood, followed by a thorough evaluation of the reliability of this assay for use in radiosensitivity assessment in patients.

The cytokinesis-block micronucleus assay for cryopreserved whole blood.

Severe Combined Immune Deficiency (SCID) is a primary deficiency of the immune system in which opportunistic and recurring infections are often fatal during neonatal or infant life. SCID is caused by an increasing number of genetic defects that induce an abrogation of T lymphocyte development or function in which B and NK cells might be affected as well. Because of the increased availability and usage of next-generation sequencing (NGS), many novel variants in SCID genes are being identified and cause a heterogeneous disease spectrum. However, the molecular and functional implications of these new variants, of which some are non-coding, are often not characterized in detail. Using targeted NGS, we identified a novel homozygous c.465-1G>C splice acceptor site variant in the  gene in a TBNK SCID patient and fully characterized the molecular and functional impact. By performing a minigene splicing reporter assay, we revealed deregulated splicing of the  transcript since a cryptic splice acceptor in exon 7 was employed. This induced a frameshift and the generation of a p.Arg155Serfs*15 premature termination codon (PTC) within all  splice variants, resulting in the absence of full-length ARTEMIS protein. Consistently, a V(D)J recombination assay and a G0 micronucleus assay demonstrated the inability of the predicted mutant ARTEMIS protein to perform V(D)J recombination and DNA damage repair, respectively. Together, these experiments molecularly and functionally clarify how a newly identified c.465-1G>C variant in the  gene is responsible for inducing SCID. In a clinical context, this demonstrates how the experimental validation of new gene variants, that are identified by NGS, can facilitate the diagnosis of SCID which can be vital for implementing appropriate therapies.

A Novel Non-Coding Variant in DCLRE1C Results in Deregulated Splicing and Induces SCID Through the Generation of a Truncated ARTEMIS Protein That Fails to Support V(D)J Recombination and DNA Damage Repair.

Recent research on normal human tissues identified omnipresent clones of cells, driven by somatic mutations known to be responsible for carcinogenesis (e.g., in TP53 or NOTCH1). These new insights are fundamentally changing current tumor evolution models, with broad oncological implications. Most studies are based on surgical remnant tissues, which are not available for many organs and rarely in a pan-organ setting (multiple organs from the same individual). Here, we describe an approach based on clinically annotated post-mortem tissues, derived from whole-body donors that are routinely used for educational purposes at human anatomy units. We validated this post-mortem approach using UV-exposed and unexposed epidermal skin tissues and confirm the presence of positively selected NOTCH1/2-, TP53- and FAT1-driven clones. No selection signals were detected in a set of immune genes or housekeeping genes. Additionally, we provide the first evidence for smoking-induced clonal changes in oral epithelia, likely underlying the origin of head and neck carcinogenesis. In conclusion, the whole-body donor-based approach provides a nearly unlimited healthy tissue resource to study mutational clonality and gain fundamental mutagenic insights in the presumed earliest stages of tumor evolution.

Article	Year
Scaffold Free Microtissue Formation for Enhanced Cartilage Repair. Annals of biomedical engineering\| PubMed ID: 31451988	2020
The cytokinesis-block micronucleus assay for cryopreserved whole blood. International journal of radiation biology\| PubMed ID: 34138661	2021
A Novel Non-Coding Variant in DCLRE1C Results in Deregulated Splicing and Induces SCID Through the Generation of a Truncated ARTEMIS Protein That Fails to Support V(D)J Recombination and DNA... Frontiers in immunology\| PubMed ID: 34220820	2021
A clinically annotated post-mortem approach to study multi-organ somatic mutational clonality in normal tissues. Scientific reports\| PubMed ID: 35725896	2022

Elien Beyls

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