Tissue engineering of human jaw muscles: the latest

Objectives: The influence of human jaw muscles on the craniofacial complex is undeniable; it is our goal to be able to influence these muscles biologically. We therefore have a series of approaches to create and manipulate jaw muscle organoids that are producing new developments. Methods: Primary human jaw (masseter) muscle derived cells (hMDC) were obtained using our well-established protocols and separated into myogenic (muscle forming; M) and non-myogenic (NM) components. 3D organoids were generated using (i) a degradable artificial scaffold (soluble phosphate glass), (ii) a “natural” 3D scaffold using Type I collagen or (iii) a composite of both. Combinations of M and NM cells were seeded on the scaffolds. Using immunocytochemistry and microscopy, the organoids were tested to determine structure and expression of relevant proteins, qPCR was used to determine transcription of functional genes and contraction as a measure of cellular activity was also quantified using a 3D cell seeded Culture Force Monitor. Results: hMDC cultured on glass fibre scaffolds in vitro attached, proliferated and differentiated to form prototypic muscle fibres attached to the glass fibres reminiscent of a “myotendinous” junction. hMDC cultured in 3D collagen scaffolds showed distinct contraction profiles (indicative of “functional” muscle) over 24 hours with an average peak force generation of 50 dynes for both M and NM cells. However, this peak force was enhanced to 125 dynes when cells were co-cultured. Surprisingly however, a combination of the two approaches was actually inferior to the separate methodologies with cells assuming a random configuration within collagen surrounding glass fibres. Conclusions: Jaw muscle fibres can be generated attached to soluble glass fibres whilst contractile cultures can be generated in 3D collagen. Work continues to couple the two approaches for the successful creation of jaw muscle in vitro.