Optimizing bone marrow harvesting sites for enhanced mesenchymal stem cell yield and efficacy in knee osteoarthritis treatment

Table 1 Cell characteristics of bone marrow from various anatomical locations

Anatomical site	Common use	MSC characteristics	Differentiation potential	Homing and engraftment potential	Therapeutic use
Iliac crest[5]	Most commonly used site for bone marrow harvesting due to its high yield and easy access	Robust proliferative capacity, multi-lineage differentiation potential. High expression of CD105, CD73, CD90, CD146, and CD271	Potent osteogenic differentiation; suitable for bone regeneration. High expression of alkaline phosphatase and osteocalcin	Higher due to the high expression of adhesion molecules like CD146 and CD271	Ideal for bone regeneration due to osteogenic potential may support hematopoiesis
Tibial bone marrow[6]	Alternative site for MSC harvesting, especially for knee OA treatment	Potentially enhanced chondrogenic differentiation. Higher expression of chondrogenic markers like Sox9 and aggrecan	Enhanced chondrogenic potential; produces glycosaminoglycans and type II collagen. Suited for cartilage repair	Potentially higher chondrogenic activity due to enhanced niche for cartilage repair	Better suited for cartilage regeneration in OA due to chondrogenic differentiation potential
Femoral bone marrow[46]	Commonly accessed during orthopedic procedures such as total knee arthroplasty	High osteogenic potential, expressed higher levels of Runt-related transcription factor-2 and bone sialoprotein but lower proliferation rates compared to iliac crest	Superior osteogenic potential, higher mineralization capacity. High calcium deposition during osteogenic differentiation	Lower proliferation rates but high osteogenic commitment	Best suited for bone repair applications like non-union fractures or large bone defects

MSC: Mesenchymal stem cell; OA: Osteoarthritis.

Table 2 Clinical application of bone marrow from various anatomical locations

Anatomical site	Clinical application	Advantages	Drawbacks	Clinical considerations
Iliac crest	Gold standard site for BMAC harvesting, widely used in regenerative therapies for knee OA due to high progenitor cell yield. High culture success rate for MSCs	High nucleated cell and clone forming unit yield, extensive clinical experience, and literature supporting efficacy. MSC yield is superior and the culture success rate can reach up to 90%	Associated with donor-site morbidity, including pain, hematoma, and nerve injury. Requires a secondary surgical site, increasing invasiveness	Preferred in cases where maximum progenitor cell yield is critical. Established protocols and extensive use in knee OA treatment. Potential for postoperative complications
Proximal humerus	Emerging alternative, commonly used in shoulder surgeries such as rotator cuff repair. Offers high-quality BMAC without a secondary incision	No need for separate incisions during shoulder procedures, and high progenitor cell yield even after large volume aspirations. Reliable across patient age groups	Primarily useful in shoulder surgeries, less studied compared to the iliac crest, though efficacy is promising	Best for minimizing patient morbidity in shoulder surgeries, with comparable efficacy to iliac crest BMAC. Convenient for combined procedures
Acetabulum	Primarily used in hip surgeries, where BMAC harvesting can occur within the same surgical field, offering dual-purpose potential. Useful for hip-related therapies	Convenient for hip-related procedures, high progenitor cell counts comparable to the iliac crest. Single-session harvesting and BMAC preparation	Limited to hip-related procedures, indirect application in knee OA treatment	Suited for scenarios where a dual-purpose approach is needed, particularly in hip surgeries. Produces high-quality BMAC but is limited to specific surgeries
Distal femur	Anatomically accessible during knee surgeries, particularly TKA. Can be seamlessly integrated with the procedure for autologous therapies	Easy anatomical access during knee surgeries, minimally invasive, lower complication risk, and integrated into surgical workflow. MSCs show similar differentiation potential to those from the iliac crest	Lower MSC yield compared to iliac crest (0.67 million cells/mL vs 10.05 million cells/mL). Slightly lower MSC culture success rate	A viable alternative when iliac crest access is limited or undesirable. Moderate MSC culture success rate (approximately 71%) but lower yield. Beneficial in knee OA treatments integrated with TKA
Proximal tibia	Similar to the distal femur, the proximal tibia can be harvested during knee surgeries like TKA. Lower MSC yield compared to the iliac crest but viable for knee OA therapy	Reduces invasiveness, less risk of complications. Easier access in knee surgeries. MSCs exhibit robust differentiation capacity, although yield is lower than iliac crest	Lower MSC yield than iliac crest (1.70 million cells/mL vs 10.05 million cells/mL). MSC culture success rate is around 47%	Suitable alternative for patients contraindicated for iliac crest harvesting. Moderate MSC yield and culture success rate (approximately 47%). Useful in knee-focused procedures

BMAC: Bone marrow aspirate concentrate; MSC: Mesenchymal stem cell; OA: Osteoarthritis; TKA: Total knee arthroplasty.

Table 3 Merits and de-merits of bone marrow from various anatomical locations

Anatomical site	Merits	Demerits
Anterior superior iliac spine	Ease of access: Superficially located and easy to palpate, facilitating quicker and less invasive procedures	Lower cell purity: Increased risk of blood dilution due to fatty tissue, potentially reducing MSC concentration
	Adequate yield: Provides a good volume of aspirate with acceptable TNC and CFU-f yields	Variable CFU-f yield: Typically lower CFU-f counts compared to the posterior superior iliac spine, which may affect the therapeutic potential of the aspirate
	Lower complication rate: Reduced risk of neurovascular injury and other complications when performed with proper technique	Patient discomfort: Proximity to muscle attachments can cause discomfort during and after the procedure
	High culture success rate: High success rate in MSC culture, indicating reliable cell viability and expansion potential	Postoperative pain: Potential for significant postoperative pain and hematoma formation
Posterior superior iliac spine	High cell yield: Provides a high concentration of TNCs and CFU-fs, making it the preferred site for harvesting high-quality aspirates	Increased technical difficulty: Less accessible, particularly in patients with high BMI or anatomical variations, requiring more complex positioning and technique
	Reduced blood dilution: Lower fatty infiltration results in higher cell purity and reduced blood contamination	Higher risk of complications: Proximity to the sacroiliac joint and gluteal neurovascular bundle increases the risk of neurovascular injury
	Consistency in results: Yields consistent results with less variability in cell counts across different patients	Patient discomfort: A deeper location and the need to traverse more tissue can cause significant post-procedural pain
	Gold standard for MSC yield: Considered the gold standard for bone marrow harvesting due to its high MSC yield and well-established protocols	Donor-site morbidity: Associated with significant morbidity, including pain, hematoma, and nerve injury, which may deter its use in certain populations
Proximal tibia	Convenience in certain surgeries: Proximity to the knee joint makes it convenient during knee-related surgeries, reducing procedure time	Lower MSC concentration: Typically provides a lower concentration of MSCs compared to the iliac crest, which may limit its effectiveness in regenerative therapies
	Adequate cell yield in some cases: Can produce a reasonable volume of aspirate, especially when large volumes are needed	Greater variability in yield: High variability in cell yield depending on factors such as patient age, BMI, and bone density, leading to inconsistent results
	Reduced risk of major complications: Stable site with a lower risk of major complications like neurovascular injury, making it a safer choice in some contexts	Difficulty in aspiration technique: Requires careful technique to avoid complications such as cortical bone fracture, particularly in osteoporotic patients
	Integrated into knee surgeries: Easily integrated into knee surgeries like TKA, adding minimal additional risk and reducing invasiveness	Lower culture success rate: MSC culture success rate is lower compared to the iliac crest, which may limit its utility in certain therapeutic applications
Proximal humerus	Convenience in shoulder surgeries: Located within the surgical field during shoulder procedures, reducing the need for an additional surgical site	Limited data: While promising, there is limited data compared to the iliac crest, and long-term outcomes need further study
	High MSC yield: Can yield a comparable number of progenitor cells to the iliac crest, making it a viable alternative for bone marrow aspirate concentrate preparation	Variability with age: Potential variability in MSC yield with age, although studies suggest this site may still be reliable across different age groups
	Reduced morbidity: Less invasive compared to iliac crest harvesting, with a lower risk of complications and patient discomfort	Not standard practice: Not as widely used or studied as the iliac crest, leading to less familiarity and potentially greater variability in outcomes
Distal femur	Ease of access during knee surgeries: Easily accessible during knee surgeries such as TKA, reducing the need for additional procedures	Lower MSC concentration: Significantly lower MSC concentration compared to the iliac crest, potentially limiting its effectiveness in high-demand applications
	Lower postoperative complications: Reduced invasiveness with potentially fewer postoperative complications, particularly in patients with previous pelvic surgeries	Lower culture success rate: The culture success rate for MSCs is lower than that of the iliac crest, which may affect the feasibility of its use in large-scale therapeutic applications
	Potential for integration into existing surgeries: Can be seamlessly integrated into existing knee procedures, adding minimal risk and enhancing therapeutic options	Inconsistent yield: Variability in cell yield can lead to inconsistent outcomes, which may affect the reliability of the site for routine use in MSC harvesting
Acetabulum	Dual-purpose during hip surgeries: Accessible during hip surgeries, allowing simultaneous bone marrow harvesting without additional surgical risks	Limited to hip procedures: Primarily applicable in the context of hip surgeries, limiting its broader use in other orthopedic applications such as knee OA
	Comparable yield to iliac crest: Studies suggest a comparable progenitor cell yield to the iliac crest, making it a feasible alternative in certain contexts	Not a primary choice for knee OA: While effective for hip procedures, its role in knee OA treatment is more indirect and not commonly pursued as a first choice

BMI: Body mass index; CFU: Clone forming unit; MSC: Mesenchymal stem cell; OA: Osteoarthritis; TKA: Total knee arthroplasty; TNC: Total nucleated cell count.

Table 4 Challenges and limitations in isolation and characterization of bone marrow

Challenges/limitations	Proposed solutions	Research gaps	Future directions
Lower MSC yield from alternative sites (distal femur, proximal tibia)	Optimize harvesting techniques at alternative sites to enhance MSC yield and viability	Lack of comprehensive comparative studies of MSC yield from different anatomical sites	Prioritize large-scale, randomized controlled trials across multiple anatomical sites
Necessity of larger volumes or in vitro expansion due to low yield	Refinements in aspiration technique and improvements in instruments	Limited data on long-term efficacy and safety of MSC-based therapies	Focus on personalized harvesting strategies based on biomarkers and patient characteristics
Influence of patient-specific factors (age and bone quality)	Develop protocols that combine cells from multiple sites for therapeutic dose	The absence of standardized protocols leads to variability in outcomes	Explore the integration of bone marrow harvesting techniques with emerging technologies (three-dimensional bioprinting, gene editing)
Variability in MSC yield and success rates across patients	Conduct large-scale comparative studies evaluating MSC yield, viability, and regenerative potential	Insufficient exploration of alternative harvesting sites for applications beyond knee osteoarthritis	Develop bioengineered scaffolds to enhance MSC survival and differentiation
Absence of standardized aspiration protocols for different sites	Establish standardized bone marrow aspiration protocols	Limited understanding of MSC functional heterogeneity from different sites	Investigate pre-operative and post-operative strategies to minimize complications
Complications at alternative sites (e.g., cortical bone fracture)	Explore less invasive harvesting techniques to reduce morbidity	Lack of personalized strategies considering genetic background, age, and disease state	Use advanced techniques (single-cell RNA sequencing, proteomics) to assess MSC characteristics
Donor-site morbidity from iliac crest harvesting	Innovate with rotational aspiration devices and powered biopsy systems
Age and health-related limitations (osteoporosis, lower MSC density)	Investigate personalized approaches based on patient-specific factors
Long-term efficacy and safety of MSC therapies not fully studied	Include extended follow-up in studies to assess long-term efficacy and safety

MSC: Mesenchymal stem cell.