Biology subjects

Flack, J. E.

Publications and source records attributed to Flack, J. E..

7 recordsLinked to original sources

bioRxiv2026

Peptide screening enables optimised biofunctional hydrogels for cultivated meat tissue engineering

Cultivated meat is an emerging biotechnology that aims to produce edible tissues in an ethical and sustainable manner. However, the recreation of skeletal muscle tissue that replicates the protein composition and sensory characteristics of traditional meat is a major challenge. Skeletal muscle tissue engineering requires non-animal-based scaffolds which are inexpensive and food-safe, while meeting specific mechanical requirements with respect to viscosity, stress-relaxation and stiffness. While many of these characteristics can be fulfilled by alginate-based biomaterials, a key limitation of alginate is its lack of intrinsic attachment sites for animal cells, preventing efficient adhesion, differentiation and tissue formation. Here, we established a screening platform to evaluate extracellular matrix (ECM)-mimicking peptides as functionalisations of alginate scaffolds in 2D. Our platform enables high-throughput assessment of cell/peptide interactions, serving as a predictive tool for 3D tissue constructs. Our screen identified two RGD-containing sequences (vitronectin- and fibronectin-mimicking peptides) as most effective in promoting attachment and myogenic fusion of bovine satellite cells. Notably, these peptides outperformed more complex mixtures containing up to seven different ECM-mimicking peptides. Our findings provide a streamlined approach for optimising biomaterial functionalisations for cultivated meat applications, and lay the groundwork for future advancements in scalable, sustainable skeletal muscle tissue engineering.

bioengineering↗

bioRxiv2025

Optimisation of skeletal muscle sampling for cultured fat production

To produce cultured meat at a commercially-relevant scale, bioprocesses must be robust, standardised and cost-efficient. In this respect, the limited in vitro lifespan of primary cells poses a major challenge, which requires regular cell sourcing by means of biopsy. We have previously shown that muscle-derived fibro-adipogenic progenitor cells (FAPs) represent a promising starting cell type for cultured fat production. These cells proliferate for a high number of population doublings (PDs) in serum-free growth medium. However, with accumulating PDs, FAPs lose their adipogenic differentiation capacity, thereby limiting the amount of cultured fat that can be produced from a given starting sample. Donor animal characteristics, including age, may affect this loss of differentiation. Here, we performed a longitudinal biopsy study to ask whether physiological differences between donor animals are reflected in FAP cell biology, and if this has an effect on loss of FAP differentiation capacity. We sampled twelve Limousin cattle over the first two years of their lives, successfully performing 144 muscle biopsies. Animals younger than six months demonstrated higher FAP yields per gram of muscle tissue, making them ideal donors for cultured fat production, but we observed little difference in the proliferation or differentiation of derived cell cultures. This work also provides valuable insights into the tissue harvesting process, highlighting the need for new, robust and standardised biopsy systems to mitigate contamination risk.

cell biology↗

bioRxiv2023

Short-stranded zein fibers for muscle tissue engineering in alginate-based hydrogels

Cultivated meat is a nascent technology that aims to produce an environmentally and animal-friendly alternative to conventional meat. Producing skeletal muscle tissue in an animal-free system allowing for high levels of myofusion and maturation is important for the nutritional and sensorial value of cultivated meat. Alginate is an attractive biomaterial to support muscle formation as it is food-safe, sustainable, cheap, and can be cross-linked using non-toxic methods. Although alginate can be functionalized to promote cell attachment, limitations in its mechanical properties, including form, viscosity and stress relaxation, hinder cellular capacity for myogenic differentiation and maturation in alginate-based hydrogels. Here, we show that the addition of electrospun short-stranded zein fibers increased hydrogel degradation, resulting in faster compaction, improved cell-gel interaction and enhanced alignment of bovine muscle precursor cells. We conclude that fiber-hydrogel composites are a promising approach to support optimal formation of 3D constructs, by improving tissue stability and thus prolonging culture duration. Together, this improves muscle-related protein content by facilitating myogenic differentiation and priming muscle organoids for maturation.

bioengineering↗

bioRxiv2023

Optimisation of cell fate determination for cultured muscle differentiation

Production of cultured meat requires defined medium formulations for the robust differentiation of myogenic cells into mature skeletal muscle fibers in vitro. Whilst such formulations can drive myogenic differentiation to an extent similar to serum-starvation based protocols, these cultures are invariably heterogeneous in nature, with a significant proportion of cells not participating in myofusion, limiting maturation of the muscle. Here, we use RNA sequencing to characterise this heterogeneity at single-nucleus resolution, identifying distinct cellular subpopulations, including proliferative cells that fail to exit the cell cycle, and reserve cells that do not commit to myogenic differentiation. We show that the ERK, NOTCH and RXR pathways act during the first stages of myogenic cell fate determination, and by targeting these pathways, cell cycle exit can be promoted whilst abrogating reserve cell formation. Under these improved culture conditions, fusion indices close to 100% can be robustly obtained in 2D culture. Finally, we demonstrate that this translates to higher levels of myotube formation and muscle protein accumulation in animal component-free bioartificial muscle constructs, providing proof of principle for the generation of highly differentiated cultured muscle with excellent mimicry to traditional muscle.

cell biology↗

bioRxiv2022

Single-cell analysis of bovine muscle-derived cell types for cultured meat production

Cultured meat technologies leverage the proliferation and differentiation of animal-derived stem cells ex vivo to produce edible tissues for human consumption in a sustainable fashion. However, skeletal muscle is a dynamic and highly complex tissue, involving the interplay of numerous mono- and multinucleated cells, including muscle fibres, satellite cells (SCs) and fibro-adipogenic progenitors (FAPs), and recreation of the tissue in vitro thus requires the characterisation and manipulation of a broad range of cell types. Here, we use a single-cell RNA sequencing approach to characterise cellular heterogeneity within bovine muscle and muscle-derived cell cultures over time. Using this data, we identify numerous distinct cell type, and develop robust protocols for the easy purification and proliferation of several of these populations. We note overgrowth of undesirable cell types within heterogeneous proliferative cultures as a barrier to efficient cultured meat production, and use transcriptomics to identify conditions that favour the growth of SCs in the context of serum-free medium. Combining RNA velocities computed in silico with time-resolved flow cytometric analysis, we characterise dynamic subpopulations and transitions between active, quiescent, and committed states of SCs, and demonstrate methods for modulation of these states during long-term proliferative cultures. This work provides an important reference for advancing our knowledge of bovine skeletal muscle biology, and its application in the development of cultured meat technologies.

cell biology↗

bioRxiv2022

Comparative analysis of cattle breeds as satellite cells donors for cultured beef

BackgroundCultured meat is a promising new field with the potential for considerable environmental and animal welfare benefits. One technological approach to cultured meat production utilises the proliferative and differentiative capacity of muscle-derived satellite cells (SCs) to produce large volumes of cultured muscle tissue from small biopsies of donor animals. Differing genotypes between cattle breeds lead to predictable phenotypic traits, resulting in breeds being favoured for their respective meat or milk production characteristics in the livestock industry. However, whilst these breeds show significant differences in muscle growth, it is unclear whether the physiological differences observed between them in vivo are reflected in differences in SC behaviour in vitro, particularly with respect to proliferation, differentiation and cellular longevity, and hence whether particular breeds might represent preferred SC donors for a cultured beef bioprocess. ResultsComparing SCs isolated from five breeds (Belgian Blue, Holstein Friesian, Galloway, Limousin and Simmental), we found that the proliferation rates were largely unaffected by the donor breed. In contrast, potentially meaningful differences were observed in the kinetics and extent of myogenic differentiation. Furthermore, whilst differentiation dropped for all breeds with increasing population doublings (PDs), SCs from Belgian Blue and Limousin cattle showed significantly longer retention of differentiation capacity over long-term passaging. ConclusionSCs from all breeds were able to proliferate and differentiate, although Limousin and (particularly) Belgian Blue cattle, both breeds commonly used for traditional meat production, may represent preferred donors for cultured beef production.

cell biology↗

bioRxiv2020

Feedback control of Wnt signaling based on histidine cluster co-aggregation between Naked/NKD and Axin

Feedback control is a universal feature of cell signaling pathways. Naked/NKD is a widely conserved feedback regulator of Wnt signaling which controls animal development and tissue homeostasis. Naked/NKD destabilizes Dishevelled, which assembles Wnt signalosomes to inhibit the {beta}-catenin destruction complex via recruitment of Axin. Here, we discover that the molecular mechanism underlying Naked/NKD function relies on its assembly into ultrastable decameric core aggregates via its conserved C-terminal histidine cluster (HisC). HisC aggregation is facilitated by Dishevelled and depends on accumulation of Naked/NKD during prolonged Wnt stimulation. Naked/NKD HisC cores co-aggregate with a conserved histidine cluster within Axin, to destabilize it along with Dishevelled, possibly via the autophagy receptor p62 which binds to HisC aggregates. Consistent with this, attenuated Wnt responses are observed in CRISPR-engineered flies and human epithelial cells whose HisC has been deleted. Thus, HisC aggregation by Naked/NKD provides context-dependent feedback control of prolonged Wnt responses.

cell biology↗