Another example is the expression of the poliovirus capsid protein (VP1) fused with the Cholera non-toxic B subunit (CTB) in lettuce chloroplasts for the development of a virus-free oral polio booster vaccine (Daniell et al., 2019) or the production of codon optimized Pro-insulin-like growth factor-1 (Pro-IGF-1) fused with the CTB transmucosal carrier or cell penetrating transduction domain (PTD), for treatment of musculoskeletal diseases (Park et al., 2020). This evidence concerns the gene IGF1 and musculoskeletal system disorder.