Types of Collagen Supplements: Benefits and How to Choose the Right One

Collagen supplements continue to lead the wellness market, with the global collagen industry estimated at $9.9 billion in 2024 and projected to grow to $18.7 billion by 2030, reflecting a strong 11.3% CAGR. This demand is fueled by consumers seeking natural, sustainable solutions to support healthy skin, joints, and overall vitality.¹Collagen Market Size, Share & Trends Analysis Report By Product (Gelatin, Hydrolyzed Collagen), By Source (Bovine, Porcine), By Application (Food & Beverages, Healthcare), By Region, And Segment Forecasts, 2025 – 2030. Grand View Research. Retrieved July 21, 2025 from https://www.grandviewresearch.com/industry-analysis/collagen-market.

For dietary supplement brand owners, understanding the various types of collagen supplements is crucial for developing effective, differentiated products. With various collagen sources and formats available, it’s essential to know how each type functions, the benefits it may offer, and how to select the right form to align with your target demographic and product positioning.

This guide breaks down the most common types of collagen supplements and provides strategic insight to help you choose the best option for your brand’s formulation goals.

What is Collagen?

What is collagen? Collagen is the most abundant protein in the human body, accounting for roughly 30% of total protein mass. It serves as the primary structural component of skin, muscles, bones, tendons, ligaments, and other connective tissues. Collagen is also found in organs, blood vessels, and the intestinal lining, where it plays a vital role in maintaining structural integrity, hydration, and elasticity.

To date, researchers have identified at least 28 types of collagen, each characterized by distinct differences in amino acid composition, structural configuration, and interactions with other molecules. These structural differences are often influenced by nutrients such as vitamin C, zinc, copper, and manganese, which support the formation of collagen’s signature triple-helix shape.

Collagen supplements provide the body with key amino acids and bioactive peptides that may help stimulate natural collagen production. These peptides act as signaling molecules that support the ongoing maintenance of tissues, including skin, nails, joints, and bones.

For brand owners developing collagen products, it’s important to highlight that collagen supplements offer functional protein, particularly beneficial when protein intake is low. Inadequate protein consumption is associated with visible signs of aging, such as thinning hair, brittle nails, and reduced mobility—all areas where collagen-based formulations may offer support.

The human body relies on about 20 different amino acids, and collagen supplements with a diverse amino acid profile are often preferred. Selecting a collagen source that delivers the right type and peptide profile can help support the body’s ability to maintain a resilient and youthful appearance over time.

As one of the leading contract manufacturers of collagen supplements, we prioritize clean, traceable, and ethically sourced raw materials. Our collagen sources include:

• • Bovine Sources (beef)
  • Porcine Sources (pork)
  • Marine Sources (fish, shark cartilage)
  • Chicken (sternum cartilage, eggshell membrane)

Because collagen powders are a premium ingredient in the nutraceutical space, they are sometimes vulnerable to adulteration. For this reason, robust quality control measures, including identity testing and supply chain transparency, are critical to ensure product integrity and brand trust.

Why Do Collagen Supplements Matter

As the body ages, collagen production naturally declines. In women, this decrease can be especially pronounced – up to 30% of skin collagen may be lost within the first five years of menopause.²Collagen. Cleveland Clinic. Retrieved July 11, 2025 from https://my.clevelandclinic.org/health/articles/23089-collagen This loss contributes to visible signs of aging such as fine lines, wrinkles, and reduced skin elasticity.

Several lifestyle and environmental factors can accelerate this decline, including:

• Excessive sun exposure
• Smoking
• Alcohol overconsumption
• Inadequate sleep
• Lack of physical activity

With age, collagen fibers in the deeper layers of the skin become less structured, transitioning from a dense, organized network into a looser, more fragmented matrix.³Rinnerhaler M, Bischof J, Streubel MK, Trost A, Richter K. Oxidative Stress in Aging Human Skin. Biomolecules. 2015 Apr 21;5(2):545-89. External stressors further degrade these fibers, diminishing their thickness and resilience, which contributes to the appearance of aging on the skin’s surface.

Exploring the Key Benefits of Collagen Supplements

Collagen supplements are widely used to support skin health, joint comfort, bone density, hair and nail strength, and muscle tone. Below is an overview of the key areas where collagen supplementation may offer value:

• Skin – The results of numerous studies have shown that type I bovine collagen peptides may help reduce the appearance of fine lines and wrinkles while improving skin elasticity and hydration.⁴Proksch E, Schunck M, Zague V, Segger D, Degwert J, Oesser S. Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis. Skin Pharmacol Physiol. 2014;27(3):113-9.⁵Proksch E, Segger D, Degwert J, Schunck M, Zague V, Oesser S. Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology: a double-blind, placebo-controlled study. Skin Pharmacol Physiol. 2014;27(1):47-55. Similar benefits have also been observed with type II collagen from chicken sternal cartilage⁶Schwartz SR, Park J. Ingestion of BioCell Collagen(®), a novel hydrolyzed chicken sternal cartilage extract; enhanced blood microcirculation and reduced facial aging signs. Clin Interv Aging. 2012;7:267-73. and collagen sourced from unhydrolyzed eggshell membrane (rich in type I, V, and X).⁷Ruff KJ, Dockery N, Aydogan C, Back M. Ovolux™ Brand Eggshell Membrane Reduces the Clinical Signs of Aging by Improving Skin, Hair & Fingernail Appearance, Texture, and Biomechanical Properties: A Single Center, Randomized, Double Blind, Placebo Controlled Clinical Trial. J Cosmetics, Dermatological Sciences and Applications. 2024; 14:306-322. https://doi.org/10.4236/jcdsa.2024.144021. The best type of collagen for skin is generally considered to be type I, though type II may also provide supportive effects.
• Joints – Type II collagen, particularly from chicken sternal cartilage, has been shown to promote joint comfort and support mobility.⁸Schwartz SR1, Park J. Ingestion of BioCell Collagen(®), a novel hydrolyzed chicken sternal cartilage extract; enhanced blood microcirculation and reduced facial aging signs. Clin Interv Aging. 2012;7:267-73. Collagen from eggshell membrane has also demonstrated benefits for functional joint capacity.⁹Blasco JM-I, Aguirre A, Gil-Quintana E, Fenaux M. The effect of daily administration of 300 mg of ovomet® for treatment of arthritis in elderly patients. Int J Clin Rheumatol. 2016; 11(5), 77-81.¹⁰Gil-Quintana E, Fenaux M, L Nuez M, et al. Short-Term Effects of Ovomet®, Eggshell Membrane, in Joint Pain: A Double-Blind and Placebo Study. J Osteopor Phys Act. 2018; 6(1):211. While type II is best known for joint support, some studies suggest type I may offer complementary benefits.
• Bone – In postmenopausal women¹¹König D, Oesser S, Scharla S, Zdzieblik D, Gollhofer A. Specific Collagen Peptides Improve Bone Mineral Density and Bone Markers in Postmenopausal Women—A Randomized Controlled Study. Nutrients. 2018; 10(1):97. https://doi.org/10.3390/nu10010097, supplementation with type I and III bovine collagen peptides has been associated with improvements in bone mineral density, suggesting a role in maintaining bone strength as part of a broader nutritional approach.
• Hair and Nails – Supplementation with type I collagen peptides has been linked to increased hair thickness and follicle activity.¹²Oesser S. The oral intake of specific Bioactive Collagen Peptides has a positive effect on hair thickness. Nutrafoods (2020) 1:134-138. Additional research¹³Ruff KJ, Dockery N, Aydogan C, Back M. Ovolux™ Brand Eggshell Membrane Reduces the Clinical Signs of Aging by Improving Skin, Hair & Fingernail Appearance, Texture, and Biomechanical Properties: A Single Center, Randomized, Double Blind, Placebo Controlled Clinical Trial. J Cosmetics, Dermatological Sciences and Applications. 2024; 14:306-322. https://doi.org/10.4236/jcdsa.2024.144021. on eggshell membrane collagen (rich in types I, V, and X) reported improvements in hair texture and nail strength. The best type of collagen for hair is widely considered to be type I, given its structural role in supporting hair growth and resilience.
• Muscle – A combination of type I and III collagen peptides, when paired with resistance training, has been shown to improve body composition by increasing fat-free mass, muscle strength, and lean body mass more effectively than exercise alone.¹⁴Oertzen-Hagemann V, Kirmse M, Eggers B, Pfeiffer K, Marcus K, de Marées M, Platen P. Effects of 12 Weeks of Hypertrophy Resistance Exercise Training Combined with Collagen Peptide Supplementation on the Skeletal Muscle Proteome in Recreationally Active Men. Nutrients. 2019 May 14;11(5):1072. doi: 10.3390/nu11051072. PMID: 31091754; PMCID: PMC6566884.
• Women – For many female consumers, collagen offers a multi-benefit approach. Type I collagen, in particular, supports skin, hair, and nail appearance, making it the most relevant form when considering collagen benefits for women across various stages of life.

Exploring the Different Types of Collagens (and What They Do)

Although approximately 28 types of collagen have been identified in the human body, only a few are commonly used in dietary supplements – primarily types I, II, and III. Below is an overview of the most relevant collagen types and their functions.

Type I Collagen

Type I collagen is the most abundant form in the human body, comprising up to 90% of total collagen. It is a key structural protein found in skin, bones, tendons, ligaments, and major organs. Type I collagen supports tissue strength¹⁵Bächinger HP, Mizuno K, Vranka JA, Boudko SP. 5.16 – Collagen Formation and Structure In Liu H-W, Mander L. Comprehensive Natural Products II. Elsevier; 2010: 469-530. ISBN 9780080453828. https://doi.org/10.1016/B978-008045382-8.00698-5. and integrity, playing a central role in maintaining skin elasticity and hydration. It also contributes to hair and nail strength, bone health, and the wound healing process.

Type II Collagen

Type II collagen is primarily located in cartilage and plays a central role in maintaining its structural integrity. It also exists in the intervertebral discs, the vitreous humor of the eye, the inner ear, and the nasal septum. This collagen type provides tensile strength and resistance to compressive forces within joints, while also supporting the environment required for healthy cartilage cells.¹⁶COL2A1 gene. MedlinePlus, National Library of Medicine. Retrieved July 21, 2025 from https://medlineplus.gov/genetics/gene/col2a1/#:~:text=Type%20II%20collagen%20is%20found%20primarily%20in,present%20in%20the%20nose%20and%20external%20ears.

Type III Collagen

Type III collagen is a fibrillar collagen often found alongside type I. It is highly concentrated in tissues requiring elasticity and structural flexibility, such as the skin, lungs, blood vessels, and intestinal walls. It supports organ structure and vascular function. Mutations or deficiencies in type III collagen have been linked to certain connective tissue conditions.¹⁷Jones ML, Bancroft JD, Gamble M. 10 – Connective Tissues and Stains. In Bancroft JD, Gamble M. Theory and Practice of Histological Techniques (Sixth Edition). Churchill Livingstone; 2008: 135-160. ISBN 9780443102790. https://doi.org/10.1016/B978-0-443-10279-0.50017-8.

Type IV Collagen

Unlike the fibrillar structure of other types, type IV collagen forms a sheet-like matrix that serves as a foundational element of basement membranes. These membranes separate and support layers of cells in tissues such as the skin and kidneys. Type IV collagen plays a vital role in cellular adhesion, migration, and differentiation, making it essential for tissue regeneration and development.¹⁸Abreu-Velez AM, Howard MS. Collagen IV in Normal Skin and in Pathological Processes. N Am J Med Sci. 2012 Jan;4(1):1-8. doi: 10.4103/1947-2714.92892. PMID: 22393540; PMCID: PMC3289483.¹⁹Öhlund D, Franklin O, Lundberg E, Lundin C, Sund M. Type IV collagen stimulates pancreatic cancer cell proliferation, migration, and inhibits apoptosis through an autocrine loop. BMC Cancer. 2013 Mar 26;13:154. doi: 10.1186/1471-2407-13-154. PMID: 23530721; PMCID: PMC3618250.

Type V Collagen

Type V collagen helps regulate the formation and diameter of type I collagen fibrils. It is present in connective tissues including skin, bone, the cornea, and the placenta. While it is less abundant than other types, its regulatory role is critical to proper fibril assembly and tissue organization.²⁰Wenstrup RJ, et al. Type V Collagen Controls the Initiation of Collagen Fibril Assembly. J Biol Chem. 2004; 279(51): 53331 – 53337.²¹Malfait F, Wenstrup R, De Paepe A (1993). Adam MP, Mirzaa GM, Pagon RA, Wallace SE, Bean LJ, Gripp KW, Amemiya A (eds.). Ehlers-Danlos Syndrome, Classic Type. GeneReviews. Seattle (WA): University of Washington, Seattle. PMID 20301422.

Type X Collagen

Type X collagen is a network-forming collagen found mainly in cartilage, particularly in the growth plate and calcifying regions of developing bone. It plays a specialized role in endochondral ossification, the process by which cartilage is converted to bone during growth and skeletal development. Genetic abnormalities in type X collagen are associated with certain skeletal disorders.²²Shen G. The role of type X collagen in facilitating and regulating endochondral ossification of articular cartilage. Orthod Craniofac Res. 2005 Feb;8(1):11-7. doi: 10.1111/j.1601-6343.2004.00308.x. PMID: 15667640.

Understanding Collagen Supplement Forms: Hydrolyzed, Undenatured, and Gelatin

Collagen supplements are available in several forms, each with distinct characteristics and functional applications. The three most common forms used in dietary supplements are hydrolyzed collagen, undenatured type II collagen, and gelatin.

Hydrolyzed Collagen

Hydrolyzed collagen, also known as collagen peptides, is produced by enzymatically breaking down collagen into smaller chains of amino acids. These peptides are highly bioavailable, easily dissolve in both hot and cold liquids, and are typically tasteless, making them ideal for powdered drink mixes. The typical daily serving ranges from 2.5 to 10 grams. Most type I and III collagen materials used in supplements are hydrolyzed for improved solubility and absorption.

Undenatured Type II Collagen

Undenatured type II collagen is derived primarily from chicken sternum cartilage and is minimally processed to retain its native triple-helix structure. Unlike hydrolyzed collagen, it is not broken down into peptides, nor is it soluble in cold water. It is typically used in small doses (around 40 mg per day) and works through a mechanism known as immune modulation, supporting joint health by interacting with the immune system rather than supplying building blocks.

Gelatin

Gelatin is created through partial hydrolysis of collagen, resulting in longer protein chains than those found in hydrolyzed collagen. Although denatured from its original form, it retains functional amino acids. Gelatin dissolves in hot water and forms a gel upon cooling. It is absorbed more slowly than collagen peptides, but remains a beneficial source of protein and amino acids.

Choosing the Right Collagen Type for Your Supplement

Supplement business owners often ask, “What is the best type of collagen?” The answer depends on the specific structure-function benefits being supported. Identifying the target health benefits is key to selecting the right collagen type.

Target Health Benefits

• Skin Health: Type I collagen is the best type of collagen for skin and for promoting skin elasticity, hydration, and wrinkle reduction.
• Joint Health: Type II collagen is the best type of collagen for joints. Undenatured Type II collagen may specifically offer additional benefits for joint health.
• Hair Health: When asked, “What is the best type of collagen for hair?”, scientists point to Type I and IV collagen as the best type of collagen for hair formation and health.
• Overall Wellness: Consider a blend of Type I and II collagens for a comprehensive approach to collagen supplementation.

How to Choose the Right Collagen Supplement: Key Considerations

So, what is the best form of collagen? The answer depends on the intended use and the health outcomes your product aims to support. Different forms and types of collagen serve different functions, and selecting the right one is essential for aligning your product with consumer needs.

Collagen Sources and Bioavailability

Collagen used in dietary supplements can come from a variety of sources, each with its own advantages and market considerations:

• Bovine Collagen: Cost-effective, but may have religious or ethical restrictions for some consumers.
• Marine Collagen: Hypoallergenic and sustainable, suitable for those with bovine allergies or ethical concerns.
• Porcine and Avian Collagen: Consider target market preferences and potential allergies.
• Ethically Sourced Collagen: Growing preference for ethically sourced collagen and innovations in vegan collagen alternatives.

When evaluating collagen efficacy, bioavailability is a critical factor. Generally, the form of collagen (not the source) has a greater impact on how well it’s absorbed. Hydrolyzed collagen peptides, typically found in type I and III collagen, are known for their high bioavailability. Undenatured type II collagen is also effective, though it operates through a different mechanism.

Selecting the right source and form of collagen allows brands to align with both consumer values and functional performance.

Delivery Formats

So, what is the best form of collagen supplement? The answer depends on the delivery method, dosage requirements, and consumer preferences. Collagen supplements are commonly available in two primary formats, each with distinct advantages:

• Powders: Highly popular for their flexibility and ability to deliver higher dosages per serving. When formulated with hydrolyzed collagen peptides, powders dissolve easily in hot or cold liquids and are generally tasteless. Non-hydrolyzed forms, however, may present challenges with taste or solubility.
• Capsules & Tablets: These offer convenience and precise dosing, making them ideal for consumers seeking portability. However, they typically contain lower amounts of collagen per serving. Capsules are best suited for doses of 1,000 mg or less to avoid requiring multiple pills daily.

Ultimately, determining the best form of collagen supplement also involves evaluating ingredient quality. Branded, clinically studied collagen peptides, paired with third-party testing and clean-label certifications, help ensure both product performance and consumer trust.

To explore innovative delivery systems in the beauty-from-within category, watch my interview on “The Vitamin Professor Podcast” with Dr. Gene Bruno, DBM, MS, RH(AHG).

Quality and Purity

In today’s competitive collagen supplement market, maintaining uncompromising quality and purity is essential for brand credibility and consumer trust. Partnering with a qualified contract development and manufacturing organization (CDMO) is the first step in safeguarding your product’s integrity.

Look for a CDMO that holds GMP (Good Manufacturing Practice) certification, which confirms adherence to regulatory quality standards. NSF International is one of the most reputable GMP certifying bodies, and their NSF Certified for Sport® program adds an extra layer of trust, particularly important if your target market includes athletes or active consumers.

Another important certification is FSSC 22000, a globally recognized food safety standard that signals a high level of operational and product safety compliance. These third-party verifications serve as critical benchmarks when selecting a manufacturing partner.

In short, ensuring your supplement manufacturer is compliant with industry regulations is one of the best things you can do to protect the integrity and reputation of your business.

Added Ingredients

One effective way to differentiate your collagen supplement in a competitive market is by including complementary ingredients that enhance its perceived value and functional support. The selection of these ingredients should align with the intended health benefits of your specific formulation. Below are targeted nutraceuticals commonly paired with collagen:

Skin Support

• Ceramides – Improve skin moisturization, reduce transepidermal water loss, and enhance elasticity.
• Astaxanthin – Offers antioxidant support, promotes skin hydration and elasticity, and helps reduce the appearance of fine lines.
• Hyaluronic Acid – A powerful humectant that binds water and supports hydration.
• Blood Orange Extract – May reduce the appearance of UV-induced age spots and skin redness.
• Grapeseed Extract – Supports even skin tone and may reduce hyperpigmentation.

Joint Support

• Cucumber Extract – Demonstrated to be more effective than glucosamine/chondroitin in some studies.
• Turmeric Extract – High-bioavailability forms may support joint comfort without a strong flavor impact.

Bone Health

• Vitamin K2 (MK-7) – Supports calcium utilization and bone mineral integrity.
• Milk Basic Protein – Backed by clinical studies for promoting bone mineral density.

Hair and Nail Support

• Rice Germ Spermidine – May support hair growth, reduce shedding, and enhance nail strength.
• Biotin – Essential for healthy hair and nail maintenance, particularly in individuals with dietary deficiencies.

Muscle Support

• Creatine Monohydrate – Widely studied for its role in increasing muscle strength and growth.
• HMB – Shown to promote lean body mass and support muscular performance.

Concluding Thoughts on the Types of Collagen Supplements

Choosing the best type of collagen for your supplement involves considering target health benefits, collagen sources, dietary restrictions, bioavailability, delivery formats, dosage requirements, and quality. Aligning your selection with market needs and desired health benefits ensures the success of your collagen supplement.

To learn more about how Vitaquest can help you Deliver What’s Next in collagen supplements, call 800-526-9095 to speak with one of our knowledgeable production specialists or to request a competitive nutraceutical manufacturing price quote if you already have your project requirements prepared.

References

• 1
  Collagen Market Size, Share & Trends Analysis Report By Product (Gelatin, Hydrolyzed Collagen), By Source (Bovine, Porcine), By Application (Food & Beverages, Healthcare), By Region, And Segment Forecasts, 2025 – 2030. Grand View Research. Retrieved July 21, 2025 from https://www.grandviewresearch.com/industry-analysis/collagen-market.
• 2
  Collagen. Cleveland Clinic. Retrieved July 11, 2025 from https://my.clevelandclinic.org/health/articles/23089-collagen
• 3
  Rinnerhaler M, Bischof J, Streubel MK, Trost A, Richter K. Oxidative Stress in Aging Human Skin. Biomolecules. 2015 Apr 21;5(2):545-89.
• 4
  Proksch E, Schunck M, Zague V, Segger D, Degwert J, Oesser S. Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis. Skin Pharmacol Physiol. 2014;27(3):113-9.
• 5
  Proksch E, Segger D, Degwert J, Schunck M, Zague V, Oesser S. Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology: a double-blind, placebo-controlled study. Skin Pharmacol Physiol. 2014;27(1):47-55.
• 6
  Schwartz SR, Park J. Ingestion of BioCell Collagen(®), a novel hydrolyzed chicken sternal cartilage extract; enhanced blood microcirculation and reduced facial aging signs. Clin Interv Aging. 2012;7:267-73.
• 7
  Ruff KJ, Dockery N, Aydogan C, Back M. Ovolux™ Brand Eggshell Membrane Reduces the Clinical Signs of Aging by Improving Skin, Hair & Fingernail Appearance, Texture, and Biomechanical Properties: A Single Center, Randomized, Double Blind, Placebo Controlled Clinical Trial. J Cosmetics, Dermatological Sciences and Applications. 2024; 14:306-322. https://doi.org/10.4236/jcdsa.2024.144021.
• 8
  Schwartz SR1, Park J. Ingestion of BioCell Collagen(®), a novel hydrolyzed chicken sternal cartilage extract; enhanced blood microcirculation and reduced facial aging signs. Clin Interv Aging. 2012;7:267-73.
• 9
  Blasco JM-I, Aguirre A, Gil-Quintana E, Fenaux M. The effect of daily administration of 300 mg of ovomet® for treatment of arthritis in elderly patients. Int J Clin Rheumatol. 2016; 11(5), 77-81.
• 10
  Gil-Quintana E, Fenaux M, L Nuez M, et al. Short-Term Effects of Ovomet®, Eggshell Membrane, in Joint Pain: A Double-Blind and Placebo Study. J Osteopor Phys Act. 2018; 6(1):211.
• 11
  König D, Oesser S, Scharla S, Zdzieblik D, Gollhofer A. Specific Collagen Peptides Improve Bone Mineral Density and Bone Markers in Postmenopausal Women—A Randomized Controlled Study. Nutrients. 2018; 10(1):97. https://doi.org/10.3390/nu10010097
• 12
  Oesser S. The oral intake of specific Bioactive Collagen Peptides has a positive effect on hair thickness. Nutrafoods (2020) 1:134-138.
• 13
  Ruff KJ, Dockery N, Aydogan C, Back M. Ovolux™ Brand Eggshell Membrane Reduces the Clinical Signs of Aging by Improving Skin, Hair & Fingernail Appearance, Texture, and Biomechanical Properties: A Single Center, Randomized, Double Blind, Placebo Controlled Clinical Trial. J Cosmetics, Dermatological Sciences and Applications. 2024; 14:306-322. https://doi.org/10.4236/jcdsa.2024.144021.
• 14
  Oertzen-Hagemann V, Kirmse M, Eggers B, Pfeiffer K, Marcus K, de Marées M, Platen P. Effects of 12 Weeks of Hypertrophy Resistance Exercise Training Combined with Collagen Peptide Supplementation on the Skeletal Muscle Proteome in Recreationally Active Men. Nutrients. 2019 May 14;11(5):1072. doi: 10.3390/nu11051072. PMID: 31091754; PMCID: PMC6566884.
• 15
  Bächinger HP, Mizuno K, Vranka JA, Boudko SP. 5.16 – Collagen Formation and Structure In Liu H-W, Mander L. Comprehensive Natural Products II. Elsevier; 2010: 469-530. ISBN 9780080453828. https://doi.org/10.1016/B978-008045382-8.00698-5.
• 16
  COL2A1 gene. MedlinePlus, National Library of Medicine. Retrieved July 21, 2025 from https://medlineplus.gov/genetics/gene/col2a1/#:~:text=Type%20II%20collagen%20is%20found%20primarily%20in,present%20in%20the%20nose%20and%20external%20ears.
• 17
  Jones ML, Bancroft JD, Gamble M. 10 – Connective Tissues and Stains. In Bancroft JD, Gamble M. Theory and Practice of Histological Techniques (Sixth Edition). Churchill Livingstone; 2008: 135-160. ISBN 9780443102790. https://doi.org/10.1016/B978-0-443-10279-0.50017-8.
• 18
  Abreu-Velez AM, Howard MS. Collagen IV in Normal Skin and in Pathological Processes. N Am J Med Sci. 2012 Jan;4(1):1-8. doi: 10.4103/1947-2714.92892. PMID: 22393540; PMCID: PMC3289483.
• 19
  Öhlund D, Franklin O, Lundberg E, Lundin C, Sund M. Type IV collagen stimulates pancreatic cancer cell proliferation, migration, and inhibits apoptosis through an autocrine loop. BMC Cancer. 2013 Mar 26;13:154. doi: 10.1186/1471-2407-13-154. PMID: 23530721; PMCID: PMC3618250.
• 20
  Wenstrup RJ, et al. Type V Collagen Controls the Initiation of Collagen Fibril Assembly. J Biol Chem. 2004; 279(51): 53331 – 53337.
• 21
  Malfait F, Wenstrup R, De Paepe A (1993). Adam MP, Mirzaa GM, Pagon RA, Wallace SE, Bean LJ, Gripp KW, Amemiya A (eds.). Ehlers-Danlos Syndrome, Classic Type. GeneReviews. Seattle (WA): University of Washington, Seattle. PMID 20301422.
• 22
  Shen G. The role of type X collagen in facilitating and regulating endochondral ossification of articular cartilage. Orthod Craniofac Res. 2005 Feb;8(1):11-7. doi: 10.1111/j.1601-6343.2004.00308.x. PMID: 15667640.