Repair of segmental load-bearing bone defect by autologous mesenchymal stem cells and plasma-derived fibrin impregnated ceramic block results in early recovery of limb function

Abstract

Calcium phosphate-based bone substitutes have not been used to repair load-bearing bone defects due to their weak mechanical property. In this study, we reevaluated the functional outcomes of combining ceramic block with osteogenic-induced mesenchymal stem cells and platelet-rich plasma (TEB) to repair critical-sized segmental tibial defect. Comparisons were made with fresh marrow-impregnated ceramic block (MIC) and partially demineralized allogeneic bone block (ALLO). Six New Zealand White female rabbits were used in each study group and three rabbits with no implants were used as negative controls. By Day 90, 4/6 rabbits in TEB group and 2/6 in ALLO and MIC groups resumed normal gait pattern. Union was achieved significantly faster in TEB group with a radiological score of 4.50 ± 0.78 versus ALLO (1.06 ± 0.32), MIC (1.28 ± 0.24), and negative controls (0). Histologically, TEB group scored the highest percentage of new bone (82% ± 5.1%) compared to ALLO (5% ± 2.5%) and MIC (26% ± 5.2%). Biomechanically, TEB-treated tibiae achieved the highest compressive strength (43.50 ± 12.72 MPa) compared to those treated with ALLO (15.15 ± 3.57 MPa) and MIC (23.28 ± 6.14 MPa). In conclusion, TEB can repair critical-sized segmental load-bearing bone defects and restore limb function.

Figure 1

Gross appearance of implants used in the three treatment groups.

Figure 2

Radiological changes seen in the three test groups immediately: Day 21, Day 60, and Day 90 after operation. TEB: defect bridged by uniform new bone, cut ends of cortex no longer distinguishable, graft no longer distinguishable. MIC: a slight increase in radiodensity surrounding and distinguishable from the graft (callus formation) with no bridging of cortex. ALLO: a slight increase in radiodensity surrounding and distinguishable from the graft bridging of one cortex with new bone formation.

Figure 3

Gait pattern recorded with TechScan software. (a) Hopping pattern of a normal rabbit with even pressure on both hind limbs. (b) A near normal hopping pattern of a rabbit from TEB group at Day 90 after operation. (c) A distorted gait pattern of a rabbit from ALLO group showing unloading of the experimental limb (colour bars indicate pressure in PSI).

Figure 4

Gross appearance of postimplanted experimental tibia compared with contralateral controls. All groups maintained equal length between test and contralateral tibiae. TEB showed good continuity of cortices along the bone-implant-bone interphases. Implant material for ALLO and MIC groups are still visible. Lt: implanted left tibia; Rt: normal right tibia.

Figure 5

Histological sections from the middle segment of the implants three months after implantation (H&E). (a) Abundant new bones were found in TEB. The section reveals new bones (Nb) forming a trabecular network amidst infiltrated cells (Ic) while new compact bone (Nb) was found at the right periphery (40x). (b) Here, the peripheral bone appeared more mature with lamellar and osteon features (O) adjacent to the well-formed intramedullary canal filled with marrow element (Me) (100x). (c) Residual ceramic (Ce) was noted in MIC. Mineral deposits (Mi) (stained red) were seen around the ceramic (40x). (d) The section reveals new bones (Nb) that are undergoing mineralization amidst infiltrated marrow element (Me) (40x). (e) Significant fibrous tissues (Fb) were noted in ALLO. The section reveals new bones (Nb) forming a trabecular network amidst infiltrated cells (Ic) (40x). (f) An intact allograft bone (Allo) (100x).

Figure 6

Histogram showing the mean percentage of residual implant, osteoid, and mature new bone determined in representative sections of TEB, MIC, and ALLO specimens.