The Urgent Need for Non-Opioid Pain Management Solutions
Surgery or trauma can lead to persistent, debilitating pain that impedes functional recovery and causes considerable distress for patients. Continuous reliance on opioid analgesics, however, has led to severe side effects and an opioid overdose epidemic that was declared a national public health emergency in 2017. There is now an urgent need to develop non-opioid alternative therapies for managing post-surgical and trauma-related pain.
An optimal strategy would be to develop local treatments that both inhibit pain and address the underlying pathophysiology, such as neuronal sensitization, while avoiding the central side effects commonly associated with opioids. A naturally occurring biologic derived from human birth tissues has recently gained attention as a potential solution to this challenging problem.
The birth tissue, predominantly comprised of the amniotic membrane (AM) and umbilical cord (UC), shares the same cell origin as the fetus and has been used as a versatile medical therapy for a wide range of conditions. FLO (Clarix Flo; BioTissue, Miami, FL), a sterile, micronized, and lyophilized form of human AM/UC matrix, has been shown to orchestrate regenerative healing with its anti-inflammatory and anti-scarring properties, particularly in ophthalmic applications.
Interestingly, FLO also appears to relieve pain effectively in several ocular surface disorders, musculoskeletal disorders such as osteoarthritis, and lower extremity neuropathy. However, the mechanisms underlying its potential pain inhibition properties and how it may affect sensory neuron excitability remained unknown.
Exploring the Pain-Relieving Potential of Human Birth Tissue Products
In a mouse model of post-surgical pain induced by a plantar incision, we first explored whether FLO could be deployed as a viable biologic for the treatment of trauma-related pain. We found that:
- Intra-paw injection of FLO, but not the vehicle (saline), acutely inhibited heat nociception in naive wild-type (WT) mice.
- FLO dose-dependently (0.1-0.5 mg) attenuated heat hypersensitivity and mechanical hyperalgesia in the hindpaw receiving the plantar incision.
- FLO partially normalized the impaired gait caused by the incision, suggesting an attenuation of movement-evoked pain.
- FLO caused no impairment in locomotor function or exploratory activity, symptoms commonly associated with opioid use.
These findings highlight the potential of FLO, a naturally derived biologic from human birth tissues, as an effective non-opioid treatment for post-surgical pain. We then sought to identify the key bioactive component mediating this pain relief.
Purifying the Key Bioactive Component: Heavy Chain-Hyaluronic Acid/Pentraxin 3 (HC-HA/PTX3)
We purified the major matrix component, the heavy chain-hyaluronic acid/pentraxin 3 (HC-HA/PTX3), from human AM. HC-HA/PTX3 has greater purity and water solubility than the whole FLO preparation.
Interestingly, HC-HA/PTX3 replicated the pain-inhibiting effects of FLO on nociceptive dorsal root ganglion (DRG) neurons via CD44-dependent pathways. Mechanistically, HC-HA/PTX3 induced cytoskeleton rearrangements to inhibit sodium current and high-voltage activated calcium current on these nociceptive neurons, suggesting it is a key bioactive component mediating the pain relief.
Our findings highlight the potential of naturally derived biologics from human birth tissues as an effective non-opioid treatment for post-surgical pain. Moreover, we have unraveled the underlying mechanisms of pain inhibition induced by FLO and HC-HA/PTX3.
Understanding the Mechanisms of Pain Relief
To elucidate the mechanisms by which FLO and HC-HA/PTX3 inhibit pain, we conducted a series of in vitro and in vivo experiments:
In Vitro Experiments:
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Calcium Imaging of DRG Neurons: FLO treatment reduced the responsiveness of DRG neurons to noxious heat stimulation, suggesting it can directly inhibit the activity of nociceptive neurons.
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Patch-Clamp Electrophysiology: HC-HA/PTX3 concentration-dependently altered the intrinsic membrane properties of small DRG neurons, decreasing their excitability.
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CD44 Dependency: The pain-inhibiting effects of HC-HA/PTX3 were abolished in DRG neurons from CD44 knockout mice, indicating the importance of CD44-dependent signaling pathways.
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Cytoskeleton Rearrangement: HC-HA/PTX3 induced polymerization and translocation of the actin cytoskeleton and the CD44 receptor in DRG neurons, which was necessary for inhibiting sodium and calcium currents.
In Vivo Experiments:
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Behavioral Pain Assays: In the plantar incision mouse model, the pain-relieving effects of both FLO and HC-HA/PTX3 were abolished in CD44 knockout mice, confirming the critical role of CD44 signaling.
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Blocking CD44: Neutralizing CD44 with an antibody prevented the analgesic actions of HC-HA/PTX3, further validating the CD44-dependent mechanisms.
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Cytoskeleton Disruption: Infusing an actin polymerization inhibitor (latrunculin-A) into DRG neurons attenuated the inhibition of sodium and calcium currents by HC-HA/PTX3, demonstrating the importance of cytoskeleton rearrangement.
Collectively, these findings reveal that HC-HA/PTX3, a key bioactive component purified from human AM, can directly inhibit the excitability of nociceptive neurons through CD44-mediated cytoskeleton rearrangement, ultimately leading to pain relief. This provides important mechanistic insights into how naturally derived biologics from human birth tissues can effectively manage post-surgical pain without the adverse effects associated with opioids.
Ensuring the Safety and Purity of HC-HA/PTX3
To ensure the quality and safety of HC-HA/PTX3, we followed rigorous good laboratory practices (GLP) during its purification and characterization:
- The purity of HC-HA/PTX3 was confirmed by the lack of detectable proteins per BCA assay, with a low level of 11.7±3.2 μg/ml, and a notable reduction in protein bands compared to the original AM preparation.
- The high molecular weight (≥500 kDa) of the hyaluronic acid component in HC-HA/PTX3 was verified using agarose gel electrophoresis.
- Western blot analysis validated the presence of the heavy chain 1 (HC1) and pentraxin 3 (PTX3) components in HC-HA/PTX3.
- Each batch of HC-HA/PTX3 was also tested and released based on its potency in inhibiting osteoclast differentiation, with an acceptance criterion of no less than 89.21% inhibition.
These quality control measures ensure that the HC-HA/PTX3 used in our studies is a highly purified, well-characterized, and potent bioactive component derived from human amniotic membrane.
Translating the Findings to Clinical Applications
The findings from our preclinical studies highlight the potential of naturally derived biologics from human birth tissues, particularly HC-HA/PTX3, as an effective non-opioid treatment for post-surgical pain. By directly inhibiting the excitability of nociceptive neurons through CD44-mediated cytoskeleton rearrangement, HC-HA/PTX3 can provide pain relief without the adverse effects associated with opioids.
These results are particularly promising given the urgent need to develop safer alternatives to opioids for managing acute and chronic pain. The local application of HC-HA/PTX3 may offer a targeted, non-systemic approach to inhibiting pain at the site of injury or surgery, while avoiding the central side effects commonly seen with opioid medications.
As we continue to explore the clinical potential of this human birth tissue-derived biologic, further research is warranted to assess its efficacy and safety in human patients. Ultimately, the development of such naturally derived, non-opioid pain management solutions could significantly improve outcomes and quality of life for individuals suffering from post-surgical or trauma-induced pain.
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