## 6 3D-Printed Tissues and Organs
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Tissue** & **Techniques** & **Cell Types** & **Growth Factors** & **Materials** & **References** \\ \hline \multirow{3}{*}{Heart valve} & Extrusion-based & Aortic valve interstitial cell & \multirow{3}{*}{–} & Hyaluronic acid & \multirow{3}{*}{[62; 68]} \\  & bioprinting & Aortic root sinus smooth-muscle cell & & & Gelatin \\ \hline \multirow{3}{*}{Myocardial tissue} & Extrusion-based & \multirow{3}{*}{Cardiomyocyte progenitor cell} & \multirow{3}{*}{–} & \multirow{3}{*}{Alginate} & \multirow{3}{*}{[69; 70]} \\  & bioprinting & & & & \\ \hline \multirow{6}{*}{Blood vessel} & Jetting-based & Endothelial cell & \multirow{3}{*}{–} & \multirow{3}{*}{Fibrin} & \multirow{3}{*}{[71; 72]} \\  & bioprinting & & Smooth-muscle cell & & \\ \cline{2-6}  & & Mesenchymal stem cell & & & \\ \cline{2-6}  & & Endothelial cell & \multirow{3}{*}{–} & Collagen & \multirow{3}{*}{[52; 73; 74]} \\  & Extrusion-based & Cardiac cell & & & & \\ \cline{2-6}  & bioprinting & Smooth-muscle cell & & & \\ \cline{2-6}  & Fibroblast & & & & \\ \hline \multirow{6}{*}{Muscolo-skeletal tissue} & Jetting-based & Muscle-derived stem cells & \multirow{3}{*}{BMP-2} & \multirow{3}{*}{Fibrin} & \multirow{3}{*}{[75; 76; 77]} \\  & bioprinting & Myoblast & FGF-2 & & \\ \cline{2-6}  & & Mesenchymal fibroblast & & & \\ \cline{2-6}  & Extrusion-based & Bone marrow stromal cell & \multirow{3}{*}{TGF-\(\beta\)} & \multirow{3}{*}{TGF-\(\beta\)} & \multirow{3}{*}{[78; 79]} \\  & bioprinting & Endothelial progenitor cell & & & \\ \cline{2-6}  & Endogenous stem cell & & & & \\ \hline \multirow{6}{*}{Nerve} & Jetting-based & Embryonic motor neuron cell & \multirow{3}{*}{CNTF} & \multirow{3}{*}{[80; 81]} \\  & Jetting-based & Hipocampal cell & & & \\ \cline{2-6}  & bioprinting & Cortical cell & & & \\ \cline{2-6}  & Neuronal precursor cell & & & & \\ \cline{2-6}  & & Neural stem cells & & & \\ \cline{2-6}  & Extrusion-based & Bone-marrow stem cell & \multirow{3}{*}{–} & \multirow{3}{*}{Agarose} & \multirow{3}{*}{[82; 83]} \\  & bioprinting & Schwann cells & & & \\ \hline \multirow{6}{*}{Skin} & Jetting-based & \multirow{3}{*}{Dermal fibroblast & \multirow{3}{*}{–} & Collagen & \multirow{3}{*}{[84]} \\  & bioprinting & Epidermal keratinocyte & & & \\ \cline{2-6}  & Extrusion-based & \multirow{3}{*}{Epithelial progenitors} & & & \\ \cline{2-6}  & bioprinting & & & & \\ \hline \multirow{2}{*}{Bone} & Extrusion-based & \multirow{3}{*}{Human mesenchymal stem cells} & \multirow{3}{*}{–} & \multirow{3}{*}{GelMA} & \multirow{3}{*}{[86]} \\  & bioprinting & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Tissue-engineering applications using 3D bioprinting, adapted from [PERSON] et al. [8] (with permission from Oxford University Press). BMP-2—; FGF-2—; TGF-\(\beta\)—; CNTF—; VEGF—; EGF—; GelMA—gelatin methacrylol. cells. This will reduce the possibility of rejection by the body, and the patient will not have to spend the rest of his/her life on anti-rejection drugs and having to deal with all of the associated side effects. [PERSON] et al. [89] (Figure 3) proposed using scaffolds of extracellular matrix from lungs of adult rat that retain the hierarchical branching with cellular components removed. A bioreactor was used to culture pulmonary epithelium and vascular endothelium on the acellular lung matrix, resulting in hierarchical organization within the matrix and efficient repopulation of the vascular compartment. When implanted into rats in vivo for short time intervals (45 to 120 minutes) the engineered lungs participated in gas exchange, although the inflation of engineered lung was found to be less than that of the native lung, and some bleeding and clotting was observed. While this represents a step toward developing a viable strategy for generating fully functional lungs in vitro, there remains the issue of extracting scaffolds from lungs, among others. This is where 3D bioprinting can help by developing patient-specific, on-demand biological scaffolds. Figure 3: Scheme for lung tissue engineering [89].