A synthetic compound suitable for transglutaminase-mediated incorporation of a therapeutic or diagnostic molecule into an extracellular matrix or a synthetic extracellular matrix component, wherein said compound comprises (a) at least one anchor domain and (b) at least one therapeutic or diagnostic molecule, wherein said anchor domain is selected from the group comprising: i. the D domain of Insulin Growth Factor-1 (IGF-I) as depicted in SEQ ID NO: 1, and ii. a derivative of i) having an amino acid sequence selected from SEQ ID NOs: 2 to 10, wherein said therapeutic or diagnostic molecule is directly linked to any of the anchor domains referred to in i) to ii) via a cleavable linker between the at least one anchor domain and the at least one therapeutic or diagnostic molecule, wherein said synthetic compound does not have the amino acid sequence of wildtype IGF-I; and wherein said synthetic compound is combined with an enzyme or fragment having transglutaminase activity, preferably a mammalian transglutaminase selected from the group consisting of FXIII, TG1, TG2, TG3, TG4, TGS, TG6 and TG7, more preferably human Factor Xllla; for use in the treatment of a disease selected from lesions, rheumatoid arthritis, osteoarthritis, musculoskeletal diseases, bone fractures, tendinitis, heart disease, atherosclerosis, impaired wound healing, muscle wasting disease, and/or bacterial infections, or for use in the in vivo diagnosis of a disease selected from the group comprising lesions and/or tissue regeneration in lesioned locations and/or for use in the prevention of inflammation in lesions, rheumatoid arthritis, osteoarthritis, musculoskeletal diseases, bone fractures, tendinitis, heart disease, atherosclerosis and impaired wound healing, and/or bacterial infections. (a) at least one anchor domain and (b) at least one therapeutic or diagnostic molecule, wherein said anchor domain is selected from the group comprising: i. the D domain of Insulin Growth Factor-1 (IGF-I) as depicted in SEQ ID NO: 1, and ii. a derivative of i) having an amino acid sequence selected from SEQ ID NOs: 2 to 10, i. the D domain of Insulin Growth Factor-1 (IGF-I) as depicted in SEQ ID NO: 1, and ii. a derivative of i) having an amino acid sequence selected from SEQ ID NOs: 2 to 10, wherein said therapeutic or diagnostic molecule is directly linked to any of the anchor domains referred to in i) to ii) via a cleavable linker between the at least one anchor domain and the at least one therapeutic or diagnostic molecule, wherein said synthetic compound does not have the amino acid sequence of wildtype IGF-I; and wherein said synthetic compound is combined with an enzyme or fragment having transglutaminase activity, preferably a mammalian transglutaminase selected from the group consisting of FXIII, TG1, TG2, TG3, TG4, TGS, TG6 and TG7, more preferably human Factor Xllla; for use in the treatment of a disease selected from lesions, rheumatoid arthritis, osteoarthritis, musculoskeletal diseases, bone fractures, tendinitis, heart disease, atherosclerosis, impaired wound healing, muscle wasting disease, and/or bacterial infections, or for use in the in vivo diagnosis of a disease selected from the group comprising lesions and/or tissue regeneration in lesioned locations and/or for use in the prevention of inflammation in lesions, rheumatoid arthritis, osteoarthritis, musculoskeletal diseases, bone fractures, tendinitis, heart disease, atherosclerosis and impaired wound healing, and/or bacterial infections.