rhBMP-2 (Recombinant Human Bone Morphogenetic Protein-2) in real world spine surgery. A phase IV, National, multicentre, retrospective study collecting data from patient medical files in French spinal centres

The leptomeninges as a critical organ for normal CNS development and function: First patient and public involved systematic review of arachnoiditis (chronic meningitis)

BACKGROUND & IMPORTANCE

This patient and public-involved systematic review originally focused on arachnoiditis, a supposedly rare "iatrogenic chronic meningitis" causing permanent neurologic damage and intractable pain. We sought to prove disease existence, causation, symptoms, and inform future directions. After 63 terms for the same pathology were found, the study was renamed Diseases of the Leptomeninges (DLMs). We present results that nullify traditional clinical thinking about DLMs, answer study questions, and create a unified path forward.

METHODS

The prospective PRISMA protocol is published at Arcsology.org. We used four platforms, 10 sources, extraction software, and critical review with ≥2 researchers at each phase. All human sources to 12/6/2020 were eligible for qualitative synthesis utilizing R. Weekly updates since cutoff strengthen conclusions.

RESULTS

Included were 887/14286 sources containing 12721 DLMs patients. Pathology involves the subarachnoid space (SAS) and pia. DLMs occurred in all countries as a contributor to the top 10 causes of disability-adjusted life years lost, with communicable diseases (CDs) predominating. In the USA, the ratio of CDs to iatrogenic causes is 2.4:1, contradicting arachnoiditis literature. Spinal fusion surgery comprised 54.7% of the iatrogenic category, with rhBMP-2 resulting in 2.4x more DLMs than no use (p<0.0001). Spinal injections and neuraxial anesthesia procedures cause 1.1%, and 0.2% permanent DLMs, respectively. Syringomyelia, hydrocephalus, and arachnoid cysts are complications caused by blocked CSF flow. CNS neuron death occurs due to insufficient arterial supply from compromised vasculature and nerves traversing the SAS. Contrast MRI is currently the diagnostic test of choice. Lack of radiologist recognition is problematic.

DISCUSSION & CONCLUSION

DLMs are common. The LM clinically functions as an organ with critical CNS-sustaining roles involving the SAS-pia structure, enclosed cells, lymphatics, and biologic pathways. Cases involve all specialties. Causes are numerous, symptoms predictable, and outcomes dependent on time to treatment and extent of residual SAS damage. An international disease classification and possible treatment trials are proposed.

Evaluation of the efficacy and safety of Escherichia coli-derived recombinant human bone morphogenetic protein-2 in transforaminal lumbar interbody fusion to treat degenerative spinal disease: a protocol of prospective, randomized controlled, assessor-blinded, open-label, multicenter trial

Background

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been widely used as an alternative bone graft in spine fusion surgery. However, clinical outcome such as effects and complications has not yet been revealed for transforaminal lumbar interbody fusion (TLIF). Although previous studies have reported some results, the evidence is weak. Therefore, the purpose of this trial is to evaluate the effectiveness and safety of Escherichia coli-derived rhBMP-2 combined with hydroxyapatite (HA) in TLIF.

Methods

This trial is designed as a prospective, assessor-blinded, open-label, multicenter, randomized controlled study. Participants will be recruited from six tertiary teaching hospitals. All randomized participants will be undergoing one- or two-level TLIF with rhBMP-2 (77 participants) as the active experimental group or with an auto-iliac bone graft (77 participants) as the control group. The primary interbody fusion rate outcome will be evaluated using computed tomography (CT) 12 months after surgery. The secondary outcomes will be as follows: clinical outcomes (visual analog scale score, EuroQol-5-dimensions-5-level score, Oswestry Disability Index score, and some surgery-related variables) and adverse effects (radiculitis, heterotrophic ossification, endplate resorption, and osteolysis). Radiological outcomes will be evaluated using simple radiography or CT. All outcomes will be measured, collected, and evaluated before surgery and at 12, 24, and 52 weeks postoperatively.

Discussion

This study will be the primary of its kind to evaluate the effectiveness and safety of E. coli-derived rhBMP-2 with HA in one- or two-level TLIF. It is designed to evaluate the equivalence of the results between rhBMP-2 with HA and auto-iliac bone graft using an appropriate sample size, assessor-blinded analyses, and prospective registration to avoid bias. This study will set up clear conclusions for using E. coli-derived rhBMP-2 with HA in TLIF.

Trial registration: This study protocol was registered at Korea Clinical Research Information Service (https://cris.nih.go.kr; number identifier: KCT0005610) on 19 November 2020. And protocol version is v1.1, January 2022.

Preparation of a nanopearl powder/C-HA (chitosan-hyaluronic acid)/rhBMP-2 (recombinant human bone morphogenetic protein-2) composite artificial bone material and a preliminary study of its effects on MC3T3-E1 cells

A nanopearl powder/C-HA (chitosan-hyaluronic acid)/rhBMP-2 (recombinant human bone morphogenetic protein-2) composite artificial bone material was prepared, and its biological properties were evaluated. The nanopearl powder/C-HA/rhBMP-2 composite porous artificial bone material was prepared using the freeze-drying method after the nanopearl powder was prepared using mechanical ball milling. The particle was measured with a transmission electron microscope, its surface morphology and pore size were observed under a scanning electron microscope. The porosity of the artificial bone was determined using pycnometry, a compression performance test was conducted with a universal testing machine, and XRD (X-ray diffraction) patterns were recorded to examine the crystal form of the pearl powder in the composite artificial bone. Finally, the artificial bone was cocultured with mouse MC3T3-E1 cells to investigate its effects on cell proliferation and differentiation and the expression of osteogenesis-related genes. The pearl powder prepared in this experiment had a particle size in the nanometer range. This nanopearl powder, along with C-HA and rhBMP-2, was compounded into the nanopearl powder/C-HA/rhBMP-2 composite artificial bone, showing pore sizes of 188.53 ± 15.32 μm, a porosity of 86.43 ± 2.78% and a compressive strength of 0.342 ± 0.024 MPa. Notably, rhBMP-2 was released from the artificial bone in a sustained manner. Moreover, this artificial bone promoted the adhesion, proliferation, and differentiation of MC3T3-E1 cells and upregulated the expression of ColαI (collagen α1), OCN (osteocalcin), OPN (osteopontin) and Runx2 (runt-related gene 2). Conclusively, this nanopearl powder/C-HA/rhBMP-2 composite artificial bone material showed good performance and cytocompatibility, suggesting that it can be used for bone tissue engineering.

Therapeutics for enhancement of spinal fusion: A mini review

Objective

With the advances in biological technologies over the past 20 years, a number of new therapies to promote bone healing have been introduced. Particularly in the spinal surgery field, more unprecedented biological therapeutics become available to enhance spinal fusion success rate along with advanced instrumentation approaches. Yet surgeons may not have been well informed about their safety and efficacy profiles in order to improve clinical practices. Therefore there is a need to summarize the evidence and bring the latest progress to surgeons for better clinical services for patients.

Methods

We comprehensively reviewed the literatures in regard to the biological therapeutics for enhancement of spinal fusion published in the last two decades.

Results

Autograft bone is still the gold standard for bone grafting in spinal fusion surgery due to its good osteoconductive, osteoinductive, and osteogenic abilities. Accumulating evidence suggests that adding rhBMPs in combination with autograft effectively promotes the fusion rate and improves surgical outcomes. However, the stimulating effect on spinal fusion of other growth factors, including PDGF, VEGF, TGF-beta, and FGF, is not convincing, while Nell-1 and activin A exhibited preliminary efficacy. In terms of systemic therapeutic approaches, the osteoporosis drug Teriparatide has played a positive role in promoting bone healing after spinal surgery, while new medications such as denosumab and sclerostin antibodies still need further validation. Currently, other treatment, such as controlled-release formulations and carriers, are being studied for better releasing profile and the administration convenience of the active ingredients.

Conclusion

As the world's population continues to grow older, the number of spinal fusion cases grows substantially due to increased surgical needs for spinal degenerative disease (SDD). Critical advancements in biological therapeutics that promote spinal fusion have brought better clinical outcomes to patients lately. With the accumulation of higher-level evidence, the safety and efficacy of present and emerging products are becoming more evident. These emerging therapeutics will shift the landscape of perioperative therapy for the enhancement of spinal fusion.

Changes in Recombinant Human Bone Morphogenetic Protein-2 Use in Posterior Fusion Over the Past Two Decades

Background

In 2011, studies suggested that complications and cancer rates associated with bone morphogenetic protein (BMP) were greater than previously reported. However, later studies reported complication rates similar to prior literature and no increased cancer rate. We evaluated the pattern of clinical utilization of BMP in posteriorly based lumbar fusion by comparing two periods: 2002-2004 and 2017-2019.

Methods

Patients who received BMP from 2002-2004 (Early) and 2017-2019 (Late) from a single multi-surgeon institution who had a lumbar fusion were identified. One hundred patients from each cohort were randomly selected. Mean total BMP used at each level and the proportion of BMP placed in the interbody space versus posterolateral gutters were evaluated.

Results

In the transforaminal lumbar intebody fusion (TLIF) cohort, the total BMP dose in the Late group (6.15 mg) was nearly half of that used in the Early group (12.04 mg, p<0.000). The amount of BMP used in the posterolateral gutters remained similar (Early: 4.01 mg vs Late: 3.38 mg, p=0.222). The amount of BMP used in the interbody space was less in the Late group (2.76 mg) compared to the Early group (8.03 mg, p<0.000). In the posterior spinal fusion (PSF) cohort, the total BMP dose remained similar between the Early (11.96 mg) and the Late groups (10.82 mg, p=0.007).

Conclusion

Change in the use of BMP in TLIF cases was driven by the complications reported in the literature with no change in outcome. A similar impetus was not seen for PSF.

A BMP/Activin A Chimera Induces Posterolateral Spine Fusion in Nonhuman Primates at Lower Concentrations Than BMP-2

BACKGROUND

Supraphysiologic bone morphogenetic protein (BMP)-2 concentrations are required to induce spinal fusion. In this study, a BMP-2/BMP-6/activin A chimera (BV-265), optimized for BMP receptor binding, delivered in a recombinant human collagen:CDHA [calcium-deficient hydroxyapatite] porous composite matrix (CM) or bovine collagen:CDHA granule porous composite matrix (PCM), engineered for optimal BV-265 retention and guided tissue repair, was compared with BMP-2 delivered in a bovine absorbable collagen sponge (ACS) wrapped around a MASTERGRAFT Matrix (MM) ceramic-collagen rod (ACS:MM) in a nonhuman primate noninstrumented posterolateral fusion (PLF) model.

METHODS

In vivo retention of 125I-labeled-BV-265/CM or PCM was compared with 125I-labeled-BMP-2/ACS or BMP-2/buffer in a rat muscle pouch model using scintigraphy. Noninstrumented PLF was performed by implanting CM, BV-265/CM, BV-265/PCM, or BMP-2/ACS:MM across L3-L4 and L5-L6 or L3-L4-L5 decorticated transverse processes in 26 monkeys. Computed tomography (CT) images were acquired at 0, 4, 8, 12, and 24 weeks after surgery, where applicable. Manual palpation, μCT (microcomputed tomography) or nCT (nanocomputed tomography), and histological analysis were performed following euthanasia.

RESULTS

Retention of 125I-labeled-BV-265/CM was greater than BV-265/PCM, followed by BMP-2/ACS and BMP-2/buffer. The CM, 0.43 mg/cm3 BMP-2/ACS:MM, and 0.05 mg/cm3 BV-265/CM failed to generate PLFs. The 0.15-mg/cm3 BV-265/CM or 0.075-mg/cm3 BV-265/PCM combinations were partially effective. The 0.25-mg/cm3 BV-265/CM and 0.15 and 0.3-mg/cm3 BV-265/PCM combinations generated successful 2-level PLFs at 12 and 24 weeks.

CONCLUSIONS

BV-265/CM or PCM can induce fusion in a challenging nonhuman primate noninstrumented PLF model at substantially lower concentrations than BMP-2/ACS:MM.

CLINICAL RELEVANCE

BV-265/CM and PCM represent potential alternatives to induce PLF in humans at substantially lower concentrations than BMP-2/ACS:MM.

Osteobiologics

BACKGROUND

Osteobiologics are engineered materials that facilitate bone healing and have been increasingly used in spine surgery. Autologous iliac crest bone grafts have been used historically, but morbidity associated with graft harvesting has led surgeons to seek alternative solutions. Allograft bone, biomaterial scaffolds, growth factors, and stem cells have been explored as bone graft substitutes and supplements.

OBJECTIVE

To review current and emerging osteobiologic technologies.

METHODS

A literature review of English-language studies was performed in PubMed. Search terms included combinations of "spine," "fusion," "osteobiologics," "autologous," "allogen(e)ic," "graft," "scaffold," "bone morphogenic protein," and "stem cells."

RESULTS

Evidence supports allograft bone as an autologous bone supplement or replacement in scenarios where minimal autologous bone is available. There are promising data on ceramics and P-15; however, comparative human trials remain scarce. Growth factors, including recombinant human bone morphogenic proteins (rhBMPs) 2 and 7, have been explored in humans after successful animal trials. Evidence continues to support the use of rhBMP-2 in lumbar fusion in patient populations with poor bone quality or revision surgery, while there is limited evidence for rhBMP-7. Stem cells have been incredibly promising in promoting fusion in animal models, but human trials to this point have only involved products with questionable stem cell content, thereby limiting possible conclusions.

CONCLUSION

Engineered stem cells that overexpress osteoinductive factors are likely the future of spine fusion, but issues with applying viral vector-transduced stem cells in humans have limited progress.

Bone Morphogenetic Proteins, Carriers, and Animal Models in the Development of Novel Bone Regenerative Therapies

Bone morphogenetic proteins (BMPs) possess a unique ability to induce new bone formation. Numerous preclinical studies have been conducted to develop novel, BMP-based osteoinductive devices for the management of segmental bone defects and posterolateral spinal fusion (PLF). In these studies, BMPs were combined with a broad range of carriers (natural and synthetic polymers, inorganic materials, and their combinations) and tested in various models in mice, rats, rabbits, dogs, sheep, and non-human primates. In this review, we summarized bone regeneration strategies and animal models used for the initial, intermediate, and advanced evaluation of promising therapeutical solutions for new bone formation and repair. Moreover, in this review, we discuss basic aspects to be considered when planning animal experiments, including anatomical characteristics of the species used, appropriate BMP dosing, duration of the observation period, and sample size.

BMP and TGFβ use and release in bone regeneration

A fracture that does not unite in nine months is defined as nonunion. Nonunion is common in fragmented fractures and large bone defects where vascularization is impaired. The distal third of the tibia, the scaphoid bone or the talus fractures are furthermore prone to nonunion. Open fractures and spinal fusion cases also need special monitoring for healing. Bone tissue regeneration can be attained by autografts, allografts, xenografts and synthetic materials, however their limited availability and the increased surgical time as well as the donor site morbidity of autograft use, and lower probability of success, increased costs and disease transmission and immunological reaction probability of allografts oblige us to find better solutions and new grafts to overcome the cons. A proper biomaterial for regeneration should be osteoinductive, osteoconductive, biocompatible and mechanically suitable. Cytokine therapy, where growth factors are introduced either exogenously or triggered endogenously, is one of the commonly used method in bone tissue engineering. Transforming growth factor β (TGFβ) superfamily, which can be divided structurally into two groups as bone morphogenetic proteins (BMPs), growth differentiation factors (GDFs) and TGFβ, activin, Nodal branch, Mullerian hormone, are known to be produced by osteoblasts and other bone cells and present already in bone matrix abundantly, to take roles in bone homeostasis. BMP family, as the biggest subfamily of TGFβ superfamily, is also reported to be the most effective growth factors in bone and development, which makes them one of the most popular cytokines used in bone regeneration. Complications depending on the excess use of growth factors, and pleiotropic functions of BMPs are however the main reasons of why they should be approached with care. In this review, the Smad dependent signaling pathways of TGFβ and BMP families and their relations and the applications in preclinical and clinical studies will be briefly summarized.