Critical limb ischemia (CLI) is a syndrome manifested by ischemic rest pain, non-healing ulcers and tissue loss. CLI patients are at very high risk of amputation and experience poor physical function, leading to severe morbidity and mortality. The fundamental goal for CLI treatment is to relieve ischemic rest pain, heal ulcers, prevent limb loss and improve the quality of life, thereby extending the survival of the patient. Surgical or endovascular revascularization aimed at increasing blood flow is currently available for limb salvage in CLI. However, up to 30% of CLI patients are not suitable for such interventions because of high operative risk or unfavorable vascular anatomy. Therefore exploring new and more effective strategies for revascularization of ischemic limbs is imperative for the establishment of a viable therapeutic alternative. With the emergence of new approaches, this review describes up-to-date progress and developments in cell-based therapy as a novel and promising alternative for CLI treatment. Preliminary clinical data have established the safety, feasibility and efficacy of stem cells, and numerous studies are underway to consolidate this evidence further. However, significant hurdles remain to be addressed before this research can be responsibly translated to the bedside. In particular, we need better understanding of the behavior of cells post-transplantation and to learn how to control their survival and migration proliferation/differentiation in the hostile pathologic environment. Future research should focus on methods of isolation, optimal dosage, appropriate cell type, route of administration, role of tissue-derived factors and supportive endogenous stimulation.
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.
Cell therapy using intramuscular injections of autologous bone-marrow mononuclear cells (BM-MNCs) improves clinical symptoms and can prevent limb amputation in atherosclerotic peripheral arterial disease (PAD) patients with critical limb ischemia (CLI). The purpose of this study was to evaluate the effects of the number of implanted BM-MNCs on clinical outcomes in atherosclerotic PAD patients with CLI who underwent cell therapy. This study was a retrospective observational study with median follow-up period of 13.5 years (range, 6.8-15.5 years) from BM-MNC implantation procedure. The mean number of implanted cells was 1.2 ± 0.7 × 109 per limb. There was no significant difference in number of BM-MNCs implanted between the no major amputation group and major amputation group (1.1 ± 0.7 × 109 vs. 1.5 ± 0.8 × 109 per limb, P = 0.138). There was also no significant difference in number of BM-MNCs implanted between the no death group and death group (1.5 ± 0.9 × 109 vs. 1.8 ± 0.8 × 109 per patient, P = 0.404). Differences in the number of BM-MNCs (mean number, 1.2 ± 0.7 × 109 per limb) for cell therapy did not alter the major amputation-free survival rate or mortality rate in atherosclerotic PAD patients with CLI. A large number of BM-MNCs will not improve limb salvage outcome or mortality.