This invention provides method for repairing, regenerating, treating, or inducing the repair of an injury, a defect or a condition of a connective tissue of a subject. This invention provides a method of regenerating, enhancing, inducing repair and/or development of connective tissue as a result of a defect, injury or condition of the connective tissue of a subject comprising the step of inserting an engineered cell which comprises a nucleic acid encoding a SMAD protein or variant thereof, so as to induce regeneration, repair and/or development of the connective tissue. This invention further provides methods of ex-vivo implantation of engineered cells into an injury, defect or condition of the connective tissue. This invention also provides a nucleic acid encoding a SMAD 8 protein variant, cells comprising such SMAD 8 variant, include mesenchymal stem cells, progenitor cells or cells derived from a connective tissue. Lastly, this invention provides SMAD 8 protein variant.