Cell therapy of natural femoral head osteonecrosis (nONFH) in the pig with injection of 140 × 106 autologous pig bone marrow mesenchymal stromal cells (pBMSCs) (n = 1) in femoral head (FH). (a) to (j) Coronal magnetic resonance imaging (MRI) analysis: red arrows indicate necrotic area, green dashed lines indicate drilling rearrangement, and blue arrows indicate repair area. (a) to (e) T1-weighted image. (f) to (j) T2-FS (fat saturation)-weighted image. (a) and (f) Normal pig FH (negative control). (b) and (g) Diagnosis of nONFH in pig FH. (c) and (h) Confirmation of nONFH in pig FH 1 month after MRI diagnosis. (d) and (i) Pig FH with nONFH 2 weeks after injection of autologous pBMSCs. (e) and (j) Pig FH with nONFH 9 weeks after injection of autologous pBMSCs. (k) and (l) Histological analysis of pig FH with nONFH 9 weeks after injection of autologous pBMSCs stained with Masson’s Tri-chrome (blue/green = collagen and non-mineralized bone; red = mineralized bone; purple = nuclei). Magnifications: 1× (k) and 20× (l). BM, bone marrow; Oc, osteocytes; TB, trabecular bone.