Compositions that include fibrin microthreads are provided. The compositions can include one or more therapeutic agents including cytokines and interleukins, extracellular matrix proteins and/or biologically active fragments thereof (e.g., RGD-containing peptides), hormones, vitamins, nucleic acids, chemotherapeutics, antibiotics, and cells. Also provided are methods of making compositions that include fibrin microthreads. Also provided are methods for using the compositions to repair or ameliorate damaged or defective organs or tissues.