Percutaneous autologous bone marrow transplantation for the treatment of delayed union of limb bone in children

Part II: Biologic Augmentation Strategies as Useful Adjuncts in Musculoskeletal Surgery

Osseous healing after injury, whether by arthritis, osteonecrosis, or fracture, follows a fairly predictable and stepwise order of events. New bone formation requires osteoinductive, osteoconductive, and osteogenetic signals and environments for rapid and complete healing. Biologic augmentation strategies, such as bone marrow aspirate concentrates (BMACs) and other forms of mesenchymal stem cells (MSCs), have been studied with renewed interest as a way to enhance healing in patients who have osteoarthritis, osteonecrosis, delayed unions, and nonunions. Many studies have demonstrated positive results in favor of biologic augmentation strategies to treat or temporize arthritis, osteonecrosis, and nonunion. Future research is required to definitively determine the utility of these biologic augmentation strategies, and larger randomized controlled trials with longer-term follow-up are needed.

Bone marrow aspirate and bone marrow aspirate concentrate: Does the literature support use in long-bone nonunion and provide new insights into mechanism of action?

PURPOSE

To assess the use of bone marrow aspirate (BM) and bone marrow aspirate concentrate (BMAC) in the treatment of long-bone nonunion and to understand mechanism of action.

METHODS

A systematic review of PubMed and EBSCOHost was completed to identify studies that investigated the use of BM or BMAC for the diagnosis of delayed union and/or nonunion of long-bone fractures. Studies of isolated bone marrow-mesenchymal stem cells (BM-MSCs) and use in non-long-bone fractures were excluded. Statistical analysis was confounded by heterogeneous fracture fixation methods, treatment history, and scaffold use.

RESULTS

Our initial search yielded 430 publications, which was screened down to 25 studies. Successful treatment in aseptic nonunion was reported at 79-100% (BM) and 50-100% (BMAC). Septic nonunion rates were slightly better at 73-100% (BM) and 83.3-100% (BMAC). 18/24 studies report union rates > 80%. One study reports successful treatment of septic nonunion with BMAC and no antibiotics. A separate study reported a significant reduction in autograft reinfection rate when combined with BMAC (P = 0.009). Major adverse events include two deep infections at injection site and one case of heterotopic ossification. Most studies note transient mild donor site discomfort and potential injection site discomfort attributed to needle size.

CONCLUSION

The current literature pertaining to use of BM/BMAC for nonunion is extremely heterogeneous in terms of patient population and concomitant treatment modalities. While results are promising for use of BM/BMAC with other gold standard treatment methodologies, the literature requires additional Level I data to clarify the impact of role BM/BMAC in treating nonunion when used alone and in combination with other modalities.

LEVEL OF EVIDENCE

Level III.

Bone Marrow Stromal Cells Sorted by Semiconducting Polymer Nanodots for Bone Repair

The use of bone marrow stromal cells (BMSCs) for bone defect repair has shown great promise due to their differentiation potential. However, isolating the BMSCs from various cell types within the bone marrow remains challenging. To tackle this issue, we utilized semiconducting polymer dots (Pdots) as markers to select the BMSCs within a specific time frame. The therapeutic efficacy of the obtained Pdot-labeled BMSCs was assessed in a bone defect model. Initially, we evaluated the binding capacity of the Pdots with four different types of cells present in the bone marrow including BMSCs, osteoblasts, macrophages, and vascular endothelial cells, in vitro. Notably, BMSCs showed the most rapid uptake of the Pdots, being labeled within only one h of coculture, while other cells took four h to become labeled. Moreover, by colocalizing the Pdots with Prrx1, Sca-1, OSX, F480, and CD105 in the bone marrow cells of monocortical tibial defect (MTD) mice in vivo, we determined the proportions of BMSCs, macrophages, and vascular endothelial cells among all labeled cells from 1 to 8 h after the Pdots injection. It was found that BMSCs have the highest proportion (92%) among all labeled cells extracted after 1 h of Pdots injection. The therapeutic efficacy of the obtained Pdots-labeled BMSCs (1 h) was assessed in a bone defect model. Results showed that the new bone accrual was significantly increased in the treatment of Pdots-labeled BMSCs compared to the bone marrow cell-treated group. Our study revealed that BMSCs screened by the Pdots could improve bone defect repair, suggesting a promising application of the Pdots in bone healing.

Engineering exosomes and biomaterial-assisted exosomes as therapeutic carriers for bone regeneration

Mesenchymal stem cell-based therapy has become an effective therapeutic approach for bone regeneration. However, there are still limitations in successful clinical translation. Recently, the secretome of mesenchymal stem cells, especially exosome, plays a critical role in promoting bone repair and regeneration. Exosomes are nanosized, lipid bilayer-enclosed structures carrying proteins, lipids, RNAs, metabolites, growth factors, and cytokines and have attracted great attention for their potential application in bone regenerative medicine. In addition, preconditioning of parental cells and exosome engineering can enhance the regenerative potential of exosomes for treating bone defects. Moreover, with recent advancements in various biomaterials to enhance the therapeutic functions of exosomes, biomaterial-assisted exosomes have become a promising strategy for bone regeneration. This review discusses different insights regarding the roles of exosomes in bone regeneration and summarizes the applications of engineering exosomes and biomaterial-assisted exosomes as safe and versatile bone regeneration agent delivery platforms. The current hurdles of transitioning exosomes from bench to bedside are also discussed.

[Effectiveness of percutaneous injection of autologous concentrated bone marrow aspirate combined with platelet-rich plasma in treatment of delayed fracture healing]

OBJECTIVE

To analyze the effectiveness of percutaneous injection of autologous concentrated bone marrow aspirate (cBMA) combined with platelet-rich plasma (PRP) in the treatment of delayed fracture healing.

METHODS

A prospective, randomized, controlled, single-blind case study was conducted. Between March 2016 and July 2018, 66 patients who met the inclusion and exclusion criteria for delayed fracture healing but had solid internal fixation of the fracture end were randomly divided into control group (31 cases, treated with percutaneous autogenous bone marrow blood injection) and study group (35 cases, treated with percutaneous autogenous cBMA+PRP injection). General data such as gender, age, body mass index, site of delayed fracture healing, length of bone defect at fracture end, and preoperative radiographic union score for tibia (RUST) showed no significant difference between the two groups ( P>0.05). Before injection, Kirschner wire was used in both groups to stimulate the fracture end and cause minor injury. The fracture healing time, treatment cost, and adverse reactions were recorded and compared between the two groups. Visual analogue scale (VAS) score was used to evaluate pain improvement. The tibial RUST score was extended to the tubular bone healing evaluation.

RESULTS

No infection of bone marrow puncture needle eyes occurred in both groups. In the control group, local swelling was obvious in 5 cases and pain was aggravated at 1 day after operation in 11 cases. In the study group, postoperative swelling and pain were not obvious, but 2 cases presented local swelling and pain. All of them relieved after symptomatic treatment. Patients in both groups were followed up, the follow-up time of the control group was 16-36 months (mean, 21.8 months), and the study group lasted 14-33 months (mean, 23.2 months). The amount of bone marrow blood was significantly lower in the study group than in the control group ( t=4.610, P=0.000). The degree of postoperative pain in the study group was less than that in the control group, and the treatment cost was higher than that in the control group. But the differences between the two groups in VAS score at 1 day after operation and treatment cost were not significant ( P>0.05). Fracture healing was achieved in 19 cases (61.3%) in the control group and 30 cases (85.7%) in the study group. The difference in fracture healing rate between the two groups was significant ( χ 2=5.128, P=0.024). Fracture healing time and RUST score at last follow-up were significantly better in the study group than in the control group ( P<0.05). At last follow-up, RUST scores in both groups were significantly improved when compared with those before operation ( P<0.05).

CONCLUSION

Autogenous cBMA combined with PRP percutaneous injection can provide high concentration of BMSCs and growth factors, and can improve the fracture healing rate and shorten the fracture healing time better than autogenous bone marrow blood injection.

Can Extracorporeal Shockwave Promote Osteogenesis of Equine Bone Marrow-Derived Mesenchymal Stem Cells In Vitro?

Both bone marrow-derived mesenchymal stem cells (BMDMSCs) and extracorporeal shockwave (ESW) have shown promise for enhancing fracture repair. If exposure of BMDMSCs to ESW enhances osteogenic differentiation, these therapies may be combined in vivo or used as a method for preconditioning BMDMSCs. The objective of this study was to determine the effect of ESW on the osteogenic ability of equine BMDMSCs. We hypothesized that ESW would promote osteogenesis evidenced by increased gene expression, alkaline phosphatase (ALPL) expression, slide morphologic score, and protein expression. BMDMSCs were evaluated from six horses. BMDMSCs were culture expanded to passage 3, dissociated, then placed in conical tubes. Treatment cells ("shocked") were exposed to 500 pulses at 0.16 mJ/mm² energy. Cells were then reseeded and grown in either growth medium or osteogenic medium. Cellular proliferation and trilineage potential were determined. Cellular morphology was scored and cells were harvested at 1, 3, 7, 14, and 21 days for rtPCR gene expression of osteogenic markers [osteonectin (ONT), osteocalcin (OCN), ALPL, collagen type 3 (COL3), and runt-related transcription factor 2 (RUNX2)]. Media supernatants were evaluated for secretion of BMP-2, VEGF, TGFβ, and PGE₂ and cellular lysates were evaluated for ALPL production. There was no difference between the proliferative ability of shocked cells versus unshocked cells in either growth medium or osteogenic medium. ALPL production was greater in shocked cells maintained in osteogenic medium versus unshocked cells in osteogenic medium at day 3 (P < 0.005). Independent of media type, ESW caused a decrease in VEGF and TGFβ production at day 3. No significant increases in gene expression were identified by rtPCR. Exposure of BMDMSCs to ESW does not result in negative effects. An initial significant increase in ALPL was detected but no persistent osteogenic effect was observed with cell expansion.